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Turner R, Rasmussen P, Gatterer H, Tremblay JC, Roche J, Strapazzon G, Roveri G, Lawley J, Siebenmann C. Cerebral blood flow regulation in hypobaric hypoxia: role of haemoconcentration. J Physiol 2024. [PMID: 38687185 DOI: 10.1113/jp285169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 04/04/2024] [Indexed: 05/02/2024] Open
Abstract
During acute hypoxic exposure, cerebral blood flow (CBF) increases to compensate for the reduced arterial oxygen content (CaO2). Nevertheless, as exposure extends, both CaO2 and CBF progressively normalize. Haemoconcentration is the primary mechanism underlying the CaO2 restoration and may therefore explain, at least in part, the CBF normalization. Accordingly, we tested the hypothesis that reversing the haemoconcentration associated with extended hypoxic exposure returns CBF towards the values observed in acute hypoxia. Twenty-three healthy lowlanders (12 females) completed two identical 4-day sojourns in a hypobaric chamber, one in normoxia (NX) and one in hypobaric hypoxia (HH, 3500 m). CBF was measured by ultrasound after 1, 6, 12, 48 and 96 h and compared between sojourns to assess the time course of changes in CBF. In addition, CBF was measured at the end of the HH sojourn after hypervolaemic haemodilution. Compared with NX, CBF was increased in HH after 1 h (P = 0.001) but similar at all later time points (all P > 0.199). Haemoglobin concentration was higher in HH than NX from 12 h to 96 h (all P < 0.001). While haemodilution reduced haemoglobin concentration from 14.8 ± 1.0 to 13.9 ± 1.2 g·dl-1 (P < 0.001), it did not increase CBF (974 ± 282 to 872 ± 200 ml·min-1; P = 0.135). We thus conclude that, at least at this moderate altitude, haemoconcentration is not the primary mechanism underlying CBF normalization with acclimatization. These data ostensibly reflect the fact that CBF regulation at high altitude is a complex process that integrates physiological variables beyond CaO2. KEY POINTS: Acute hypoxia causes an increase in cerebral blood flow (CBF). However, as exposure extends, CBF progressively normalizes. We investigated whether hypoxia-induced haemoconcentration contributes to the normalization of CBF during extended hypoxia. Following 4 days of hypobaric hypoxic exposure (corresponding to 3500 m altitude), we measured CBF before and after abolishing hypoxia-induced haemoconcentration by hypervolaemic haemodilution. Contrary to our hypothesis, the haemodilution did not increase CBF in hypoxia. Our findings do not support haemoconcentration as a stimulus for the CBF normalization during extended hypoxia.
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Affiliation(s)
- Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
- Institut für Sportwissenschaft, Universität Innsbruck, Tyrol, Austria
| | | | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Joshua C Tremblay
- School of Sport and Health Sciences, Cardiff Metropolitan University, Wales, UK
| | - Johanna Roche
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giulia Roveri
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Justin Lawley
- Institut für Sportwissenschaft, Universität Innsbruck, Tyrol, Austria
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Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
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Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
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Ibrahim A, Stefani A, Cesari M, Roche J, Gatterer H, Holzknecht E, Turner R, Vinetti G, Furian M, Heidbreder A, Högl B, Siebenmann C. Effects of periodic breathing on sleep at high altitude: a randomized, placebo-controlled, crossover study using inspiratory CO 2. J Physiol 2024. [PMID: 38408065 DOI: 10.1113/jp285397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 01/17/2024] [Indexed: 02/28/2024] Open
Abstract
Hypoxia at high altitude facilitates changes in ventilatory control that can lead to nocturnal periodic breathing (nPB). Here, we introduce a placebo-controlled approach to prevent nPB by increasing inspiratory CO2 and used it to assess whether nPB contributes to the adverse effects of hypoxia on sleep architecture. In a randomized, single-blinded, crossover design, 12 men underwent two sojourns (three days/nights each, separated by 4 weeks) in hypobaric hypoxia corresponding to 4000 m altitude, with polysomnography during the first and third night of each sojourn. During all nights, subjects' heads were encompassed by a canopy retaining exhaled CO2 , and CO2 concentration in the canopy (i.e. inspiratory CO2 concentration) was controlled by adjustment of fresh air inflow. Throughout the placebo sojourn inspiratory CO2 was ≤0.2%, whereas throughout the other sojourn it was increased to 1.76% (IQR, 1.07%-2.44%). During the placebo sojourn, total sleep time (TST) with nPB was 54.3% (37.4%-80.8%) and 45.0% (24.5%-56.5%) during the first and the third night, respectively (P = 0.042). Increased inspiratory CO2 reduced TST with nPB by an absolute 38.1% (28.1%-48.1%), the apnoea-hypopnoea index by 58.1/h (40.1-76.1/h), and oxygen desaturation index ≥3% by 56.0/h (38.9.1-73.2/h) (all P < 0.001), whereas it increased the mean arterial oxygen saturation in TST by 2.0% (0.4%-3.5%, P = 0.035). Increased inspiratory CO2 slightly increased the percentage of N3 sleep during the third night (P = 0.045), without other effects on sleep architecture. Increasing inspiratory CO2 effectively prevented hypoxia-induced nPB without affecting sleep macro-architecture, indicating that nPB does not explain the sleep deterioration commonly observed at high altitudes. KEY POINTS: Periodic breathing is common during sleep at high altitude, and it is unclear how this affects sleep architecture. We developed a placebo-controlled approach to prevent nocturnal periodic breathing (nPB) with inspiratory CO2 administration and used it to assess the effects of nPB on sleep in hypobaric hypoxia. Nocturnal periodic breathing was effectively mitigated by an increased inspiratory CO2 fraction in a blinded manner. Prevention of nPB did not lead to relevant changes in sleep architecture in hypobaric hypoxia. We conclude that nPB does not explain the deterioration in sleep architecture commonly observed at high altitude.
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Affiliation(s)
- Abubaker Ibrahim
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Ambra Stefani
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Matteo Cesari
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Johanna Roche
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Evi Holzknecht
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giovanni Vinetti
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Michael Furian
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland
| | - Anna Heidbreder
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Birgit Högl
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
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Hilty MP, Siebenmann C, Rasmussen P, Keiser S, Müller A, Lundby C, Maggiorini M. Beta-adrenergic blockade increases pulmonary vascular resistance and causes exaggerated hypoxic pulmonary vasoconstriction at high altitude: a physiological study. Eur Heart J Cardiovasc Pharmacother 2024:pvae004. [PMID: 38216517 DOI: 10.1093/ehjcvp/pvae004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2024]
Abstract
BACKGROUND An increasing number of hypertensive persons travel to high altitude while using antihypertensive medications such as betablockers. Nevertheless, while hypoxic exposure initiates an increase in pulmonary artery pressure (Ppa) and pulmonary vascular resistance (PVR), the contribution of the autonomic nervous system is unclear. In animals, β-adrenergic blockade has induced pulmonary vasoconstriction in normoxia and exaggerated hypoxic pulmonary vasoconstriction (HPV) and both effects were abolished by muscarinic blockade. We thus hypothesized that in humans propranolol (PROP) increases Ppa and PVR in normoxia and exaggerates HPV, and that these effects of PROP are abolished by glycopyrrolate (GLYC). METHODS In seven healthy male lowlanders, pulmonary artery pressure was invasively measured without medication, with PROP and PROP+GLYC, both at sea level (SL, 488m) and after a three-week sojourn at 3454m altitude (HA). Bilateral thigh-cuff release maneuvers were performed to derive pulmonary pressure-flow relationships and pulmonary vessel distensibility. RESULTS At SL, PROP increased Ppa and PVR from (mean±SEM) 14±1 to 17±1mmHg and from 69±8 to 108±11dyn*s*cm-5 (21 and 57% increase, p=0.01 and p<0.0001). The PVR response to PROP was amplified at HA to 76% (p<0.0001, p[interaction]=0.05). At both altitudes, PROP+GLYC abolished the effect of PROP on Ppa and PVR. Pulmonary vessel distensibility decreased from 2.9±0.5 to 1.7±0.2 at HA (p<0.0001) and to 1.2±0.2 with PROP, and further decreased to 0.9±0.2%*mmHg-1 with PROP+GLYC (p=0.01). CONCLUSIONS Our data show that β-adrenergic blockade increases, and muscarinic blockade decreases PVR, whereas both increase pulmonary artery elastance. Future studies may confirm potential implications from the finding that β-adrenergic blockade exaggerates HPV for the management of mountaineers using β-blockers for prevention or treatment of cardiovascular conditions.
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Affiliation(s)
- Matthias Peter Hilty
- Institute of Intensive Care Medicine, University Hospital of Zurich, Switzerland
| | - Christoph Siebenmann
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Switzerland
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Peter Rasmussen
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Switzerland
| | - Stefanie Keiser
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Switzerland
| | - Andrea Müller
- Institute of Intensive Care Medicine, University Hospital of Zurich, Switzerland
| | - Carsten Lundby
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Switzerland
- Department of Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, Norway
| | - Marco Maggiorini
- Institute of Intensive Care Medicine, University Hospital of Zurich, Switzerland
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Oberholzer L, Montero D, Robach P, Siebenmann C, Ryrsøe CK, Bonne TC, Breenfeldt Andersen A, Bejder J, Karlsen T, Edvardsen E, Rønnestad BR, Hamarsland H, Cepeda-Lopez AC, Rittweger J, Treff G, Ahlgrim C, Almquist NW, Hallén J, Lundby C. Determinants and reference values for blood volume and total hemoglobin mass in women and men. Am J Hematol 2024; 99:88-98. [PMID: 38032792 DOI: 10.1002/ajh.27162] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 10/04/2023] [Accepted: 10/12/2023] [Indexed: 12/02/2023]
Abstract
Blood volume (BV) is an important clinical parameter and is usually reported per kg of body mass (BM). When fat mass is elevated, this underestimates BV/BM. One aim was to study if differences in BV/BM related to sex, age, and fitness would decrease if normalized to lean body mass (LBM). The analysis included 263 women and 319 men (age: 10-93 years, body mass index: 14-41 kg/m2 ) and 107 athletes who underwent assessment of BV and hemoglobin mass (Hbmass ), body composition, and cardiorespiratory fitness. BV/BM was 25% lower (70.3 ± 11.3 and 80.3 ± 10.8 mL/kgBM ) in women than men, respectively, whereas BV/LBM was 6% higher in women (110.9 ± 12.5 and 105.3 ± 11.2 mL/kgLBM ). Hbmass /BM was 34% lower (8.9 ± 1.4 and 11.5 ± 11.2 g/kgBM ) in women than in men, respectively, but only 6% lower (14.0 ± 1.5 and 14.9 ± 1.5 g/kgLBM )/LBM. Age did not affect BV. Athlete's BV/BM was 17.2% higher than non-athletes, but decreased to only 2.5% when normalized to LBM. Of the variables analyzed, LBM was the strongest predictor for BV (R2 = .72, p < .001) and Hbmass (R2 = .81, p < .001). These data may only be valid for BV/Hbmass when assessed by CO re-breathing. Hbmass /LBM could be considered a valuable clinical matrix in medical care aiming to normalize blood homeostasis.
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Affiliation(s)
- Laura Oberholzer
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - David Montero
- Department of Medicine, School of Clinical Medicine/Public Health, The University of Hongkong, Hongkong, China
| | - Paul Robach
- Ecole Nationale des Sports de Montagne, site de l'Ecole Nationale de Ski et d'Alpinisme, Chamonix, France
| | | | - Camilla Koch Ryrsøe
- Department of Infectious Diseases and Pulmonary Medicine, Nordsjaellands University Hospital, Hillerød, Denmark
| | - Thomas C Bonne
- Department of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | | | - Jacob Bejder
- Department of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Trine Karlsen
- Faculty of Nursing and Health Sciences, Nord University, Bodø, Norway
- Cardiac Exercise Research Group, Department of Circulation and Medical Imaging, NTNU-Norwegian University of Science of Technology, Trondheim, Norway
| | - Elisabeth Edvardsen
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Bent R Rønnestad
- Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, Norway
| | - Håvard Hamarsland
- Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, Norway
| | - Ana C Cepeda-Lopez
- Health Sciences Division, University of Monterrey (UDEM), Monterrey, Mexico
| | - Jörn Rittweger
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
- Department of Pediatrics and Adolescent Medicine, University Hospital Cologne, Cologne, Germany
| | - Gunnar Treff
- Division of Sports and Rehabilitation Medicine, Ulm University Hospital, Ulm, Germany
| | - Christoph Ahlgrim
- University Heart Center Freiburg, Medical Center-University of Freiburg, Bad Krozingen, Germany
| | - Nicki Winfield Almquist
- Department of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Jostein Hallén
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Carsten Lundby
- Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, Norway
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Siebenmann C, Roche J, Schlittler M, Simpson LL, Stembridge M. Regulation of haemoglobin concentration at high altitude. J Physiol 2023. [PMID: 38051656 DOI: 10.1113/jp284578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/21/2023] [Indexed: 12/07/2023] Open
Abstract
Lowlanders sojourning for more than 1 day at high altitude (HA) experience a reduction in plasma volume (PV) that increases haemoglobin concentration and thus restores arterial oxygen content. If the sojourn extends over weeks, an expansion of total red cell volume (RCV) occurs and contributes to the haemoconcentration. While the reduction in PV was classically attributed to an increased diuretic fluid loss, recent studies support fluid redistribution, rather than loss, as the underlying mechanism. The fluid redistribution is presumably driven by a disappearance of proteins from the circulation and the resulting reduction in oncotic pressure exerted by the plasma, although the fate of the disappearing proteins remains unclear. The RCV expansion is the result of an accelerated erythropoietic activity secondary to enhanced renal erythropoietin release, but a contribution of other mechanisms cannot be excluded. After return from HA, intravascular volumes return to normal values and the normalisation of RCV might involve selective destruction of newly formed erythrocytes, although this explanation has been strongly challenged by recent studies. In contrast to acclimatised lowlanders, native highlanders originating from the Tibetan and the Ethiopian plateaus present with a normal or only mildly elevated haemoglobin concentration. Genetic adaptations blunting the erythropoietic response to HA exposure have been proposed as an explanation for the absence of more pronounced haemoconcentration in these populations, but new evidence also supports a contribution of a larger than expected PV. The functional significance of the relatively low haemoglobin concentration in Tibetan and Ethiopian highlanders is incompletely understood and warrants further investigation.
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Affiliation(s)
| | - Johanna Roche
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Maja Schlittler
- AO Research Institute Davos, Regenerative Orthopaedics Program, Davos, Switzerland
| | - Lydia L Simpson
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
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Kammerer T, Walzl A, Müller T, Groene P, Roveri G, Turner R, Roche J, Gatterer H, Siebenmann C, Schäfer ST. Effects of Hypobaric Hypoxia on Coagulation in Healthy Subjects Exposed to 3,500 m Altitude. High Alt Med Biol 2023; 24:94-103. [PMID: 37339401 DOI: 10.1089/ham.2022.0154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023] Open
Abstract
Kammerer, Tobias, Anna Walzl, Thomas Müller, Philipp Groene, Giulia Roveri, Rachel Turner, Johanna Roche, Hannes Gatterer, Christoph Siebenmann, and Simon T. Schäfer. Effects of hypobaric hypoxia on coagulation in healthy subjects exposed to 3,500 m altitude. High Alt Med Biol. 24:94-103, 2023. Background: Hypoxia is discussed as a trigger for prothrombotic changes both in intensive care and high altitude medicine. This research study aimed to evaluate the effect of isolated hypobaric hypoxia (HH) on coagulation in females in a highly standardized setting. Methods: Twelve healthy female subjects were studied under HH (equivalent to 3,500 m) and normoxia (NX) during two 4-day sojourns, in a strictly controlled crossover design. Nutrition, fluid intake, hormonal status (i.e., menstrual cycle variation), and physical stress were standardized. Functional coagulation and blood lysis were measured by viscoelastometry and compared between HH and NX. In addition, plasma-based coagulation tests (PBCTs), namely prothrombin time, activated partial thromboplastin time, fibrinogen, factor VIII coagulation activity (FVIII:C), von Willebrand factor antigen (vWF:Ag), and von Willebrand factor ristocetin cofactor activity (vWF:RCo) were measured. Results: Neither for Viscoelastic Haemostatic Assays nor for PBCTs significant changes were found for HH compared with NX (all p > 0.05). Specifically, the lysis ability, as well as clotting time, clot formation, clot amplitude, and maximum clot firmness unchanged were similar between HH and NX. This also applied to all other variables. Conclusion: We demonstrate that moderate HH per se has no influence on blood coagulation in healthy females.
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Affiliation(s)
- Tobias Kammerer
- Department of Anaesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
- Department of Anaesthesiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Anna Walzl
- Department of Anaesthesiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Thomas Müller
- Department of Laboratory Medicine, Hospital Voecklabruck, Voecklabruck, Austria
| | - Philipp Groene
- Department of Anaesthesiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Giulia Roveri
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
- Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Rachel Turner
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
| | - Johanna Roche
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
| | - Hannes Gatterer
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
- Institute for Sports Medicine, Alpine Medicine and Health Tourism (ISAG), UMIT TIROL-Private University for Health Sciences and Health Technology, Hall in Tirol, Austria
| | | | - Simon T Schäfer
- Department of Anaesthesiology, Ludwig-Maximilians-University Munich, Munich, Germany
- Department of Anesthesia, Intensive Care Medicine, Emergency Medicine and Pain Therapy, University Hospital, Carl-von-Ossietzky University Oldenburg, Klinikum Oldenburg AöR, Oldenburg, Germany
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Gatterer H, Roche J, Turner R, Vinetti G, Roveri G, Schlittler M, Kob M, Walzl A, Dal Cappello T, Debevec T, Siebenmann C. Changes in body mass, appetite-related hormones, and appetite sensation in women during 4 days of hypobaric hypoxic exposure equivalent to 3,500-m altitude. J Appl Physiol (1985) 2023; 134:133-141. [PMID: 36476162 PMCID: PMC9829471 DOI: 10.1152/japplphysiol.00369.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Altitude exposure may suppress appetite and hence provide a viable weight-loss strategy. While changes in food intake and availability as well as physical activity may contribute to altered appetite at altitude, herein we aimed to investigate the isolated effects of hypobaric hypoxia on appetite regulation and sensation. Twelve healthy women (age: 24.0 ± 4.2 years, body mass: 60.6 ± 7.0 kg) completed two 4-day sojourns in a hypobaric chamber, one in normoxia [PB = 761 mmHg, 262 m (NX)] and one in hypobaric hypoxia [PB = 493 mmHg (HH)] equivalent to 3,500-m altitude. Energy intake was standardized 4 days prior and throughout both sojourns. Plasma concentrations of leptin, acylated ghrelin, cholecystokinin (CCK), and cytokine growth differentiation factor 15 (GDF15) were determined every morning. Before and after breakfast, lunch, and dinner, appetite was assessed using visual analog scales. Body mass was significantly decreased following HH but not NX (-0.71 ± 0.32 kg vs. -0.05 ± 0.54 kg, condition: P < 0.001). Compared to NX, acylated ghrelin decreased throughout the HH sojourn (condition × time: P = 0.020), while leptin was higher throughout the entire HH sojourn (condition: P < 0.001). No differences were observed in CCK and GDF15 between the sojourns. Feelings of satiety and fullness were higher (condition: P < 0.001 and P = 0.013, respectively), whereas prospective food consumption was lower in HH than in NX (condition: P < 0.001). Our findings suggest that hypoxia exerts an anorexigenic effect on appetite-regulating hormones, suppresses subjective appetite sensation, and can induce weight loss in young healthy women. Among the investigated hormones, acylated ghrelin and leptin most likely explain the observed HH-induced appetite suppression.NEW & NOTEWORTHY This study investigated the effects of hypoxia on appetite regulation in women while strictly controlling for diet, physical activity, menstrual cycle, and environmental conditions. In young women, 4 days of altitude exposure (3,500 m) decreases body weight and circulating acylated ghrelin levels while preserving leptin concentrations. In line with the hormonal changes, altitude exposure induces alterations in appetite sensation, consisting of a decreased feeling of hunger and prospective food intake and an increased feeling of fullness and satiety.
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Affiliation(s)
- Hannes Gatterer
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy,2Institute for Sports Medicine, Alpine Medicine and Health Tourism (ISAG), UMIT TIROL–Private University for Health Sciences and Health Technology, Hall in Tirol, Austria
| | - Johanna Roche
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Rachel Turner
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giovanni Vinetti
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giulia Roveri
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy,3Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Maja Schlittler
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Michael Kob
- 4Division of Clinical Nutrition, Bolzano Regional Hospital, Bolzano, Italy
| | - Anna Walzl
- 5Department of Anaesthesiology, University Hospital, LMU Munich, Munich, Germany
| | - Tomas Dal Cappello
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Tadej Debevec
- 6Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia,7Department of Automation, Biocybernetics, and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
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9
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Roche J, Rasmussen P, Gatterer H, Roveri G, Turner R, van Hall G, Maillard M, Walzl A, Kob M, Strapazzon G, Goetze JP, Schäfer ST, Kammerer T, Nader E, Connes P, Robert M, Mueller T, Feraille E, Siebenmann C. Hypoxia briefly increases diuresis but reduces plasma volume by fluid redistribution in women. Am J Physiol Heart Circ Physiol 2022; 323:H1068-H1079. [PMID: 36269645 PMCID: PMC9678412 DOI: 10.1152/ajpheart.00394.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We have recently reported that hypobaric hypoxia (HH) reduces plasma volume (PV) in men by decreasing total circulating plasma protein (TCPP). Here, we investigated whether this applies to women and whether an inflammatory response and/or endothelial glycocalyx shedding could facilitate the TCCP reduction. We further investigated whether acute HH induces a short-lived diuretic response that was overlooked in our recent study, where only 24-h urine volumes were evaluated. In a strictly controlled crossover protocol, 12 women underwent two 4-day sojourns in a hypobaric chamber: one in normoxia (NX) and one in HH equivalent to 3,500-m altitude. PV, urine output, TCPP, and markers for inflammation and glycocalyx shedding were repeatedly measured. Total body water (TBW) was determined pre- and postsojourns by deuterium dilution. PV was reduced after 12 h of HH and thereafter remained 230-330 mL lower than in NX (P < 0.0001). Urine flow was 45% higher in HH than in NX throughout the first 6 h (P = 0.01) but lower during the second half of the first day (P < 0.001). Twenty-four-hour urine volumes (P ≥ 0.37) and TBW (P ≥ 0.14) were not different between the sojourns. TCPP was lower in HH than in NX at the same time points as PV (P < 0.001), but inflammatory or glycocalyx shedding markers were not consistently increased. As in men, and despite initially increased diuresis, HH-induced PV contraction in women is driven by a loss of TCPP and ensuing fluid redistribution, rather than by fluid loss. The mechanism underlying the TCPP reduction remains unclear but does not seem to involve inflammation or glycocalyx shedding.NEW & NOTEWORTHY This study is the first to investigate the mechanisms underlying plasma volume (PV) contraction in response to hypoxia in women while strictly controlling for confounders. PV contraction in women has a similar time course and magnitude as in men and is driven by the same mechanism, namely, oncotically driven redistribution rather than loss of fluid. We further report that hypoxia facilitates an increase in diuresis, that is, however, short-lived and of little relevance for PV regulation.
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Affiliation(s)
- Johanna Roche
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | | | - Hannes Gatterer
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giulia Roveri
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Rachel Turner
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Gerrit van Hall
- 3Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark,4Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark,5Clinical Metabolomics Core Facility, Rigshospitalet, University of Copenhagen, Denmark
| | - Marc Maillard
- 6Service of Nephrology, University Hospital of Lausanne, Lausanne, Switzerland
| | - Anna Walzl
- 7Department of Anesthesiology, LMU Klinikum, Ludwig-Maximilians-University München, Munich, Germany
| | - Michael Kob
- 8Division of Clinical Nutrition, Bolzano Regional Hospital, Bolzano, Italy
| | - Giacomo Strapazzon
- 1Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Jens Peter Goetze
- 3Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Simon Thomas Schäfer
- 7Department of Anesthesiology, LMU Klinikum, Ludwig-Maximilians-University München, Munich, Germany
| | - Tobias Kammerer
- 7Department of Anesthesiology, LMU Klinikum, Ludwig-Maximilians-University München, Munich, Germany,9Department for Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Elie Nader
- 10Laboratory LIBM EA7424, Vascular Biology and Red Blood Cell Team, University of Lyon, Lyon, France
| | - Philippe Connes
- 10Laboratory LIBM EA7424, Vascular Biology and Red Blood Cell Team, University of Lyon, Lyon, France
| | - Mélanie Robert
- 10Laboratory LIBM EA7424, Vascular Biology and Red Blood Cell Team, University of Lyon, Lyon, France
| | - Thomas Mueller
- 11Department of Clinical Pathology, Hospital of Bolzano, Bolzano, Italy,12Department of Laboratory Medicine, Hospital Voecklabruck, Voecklabruck, Austria
| | - Eric Feraille
- 13National Center of Competence in Research Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland,14Department of Cellular Physiology and Metabolism, University of Geneva, Geneva, Switzerland
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10
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Fisher JP, Roche J, Turner R, Walzl A, Roveri G, Gatterer H, Siebenmann C. Hypobaric hypoxia and cardiac baroreflex sensitivity in young women. Am J Physiol Heart Circ Physiol 2022; 323:H1048-H1054. [PMID: 36240437 PMCID: PMC9678423 DOI: 10.1152/ajpheart.00452.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We sought to determine the effects of prolonged moderate hypobaric hypoxia (HH) on cardiac baroreflex sensitivity (cBRS) in young women and whether these effects are a consequence of the reduced arterial oxygen (O2) tension and/or increased pulmonary ventilation in HH. We hypothesized that HH would reduce cBRS and that this effect would be counteracted by acute restoration of the inspiratory partial pressure of O2 ([Formula: see text]) and/or voluntary attenuation of pulmonary ventilation. Twelve healthy women (24.0 ± 4.2 yr) were studied before (day 0) and twice during a sojourn in a hypobaric chamber (∼8 h, day 1; 4 days, day 4) where barometric pressure corresponded to ∼3,500-m altitude. Minute ventilation (V̇e; pneumotachometer), heart rate (electrocardiogram), and arterial pressure (finger volume clamp method) were recorded. cBRS was calculated using transfer function analysis between systolic pressure and RR interval. Assessments were made during 1) spontaneous breathing and (in HH only), 2) controlled breathing (reducing V̇e by ∼1 to 2 L/min), and 3) breathing a hyperoxic gas mixture that normalized [Formula: see text]. During spontaneous breathing, HH decreased cBRS (12.5 ± 7.1, 8.9 ± 4.4, and 7.4 ± 3.0 ms/mmHg on days 0, 1, and 4, respectively; P = 0.018). The normalization of [Formula: see text] increased cBRS (10.6 ± 3.3 and 10.7 ± 6.1 ms/mmHg on days 1 and 4) in HH compared with values observed during spontaneous breathing (P < 0.001), whereas controlled breathing had no effect on cBRS (P = 0.708). These findings indicate that ongoing arterial chemoreflex activation by the reduced arterial O2 tension, independently of the hypoxic ventilatory response, reduces cBRS in young women exposed to extended HH.NEW & NOTEWORTHY We examined the effects of prolonged hypobaric hypoxia (corresponding to ∼3,500-m altitude) on cardiac baroreflex sensitivity (cBRS) in young women and investigated underlying mechanisms. We found that cBRS was reduced in hypoxia and that this reduction was attenuated by acute restoration of inspiratory oxygen partial pressure but not by volitional restraint of pulmonary ventilation. These findings help to elucidate the role of arterial chemoreflex mechanisms in the control of cBRS during hypobaric hypoxia in young women.
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Affiliation(s)
- James P. Fisher
- 1Manaaki Manawa–The Centre for Heart Research, Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, Auckland, New Zealand
| | - Johanna Roche
- 2Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Rachel Turner
- 2Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Anna Walzl
- 3Department of Anaesthesiology, LMU Klinikum, Ludwig-Maximilians-University München, Munich, Germany
| | - Giulia Roveri
- 2Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hannes Gatterer
- 2Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
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11
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Diaz-Canestro C, Siebenmann C, Montero D. Marked improvements in cardiac function in postmenopausal women exposed to blood withdrawal plus endurance training. J Sports Sci 2022; 40:1609-1617. [PMID: 35767591 DOI: 10.1080/02640414.2022.2095489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The cardiac phenotype of a substantial fraction of the population, i.e., mature women, is mainly unresponsive to endurance training (ET), the most effective intervention to improve cardiorespiratory fitness. This study assessed whether a novel intervention comprising additional haemodynamic stimuli may overcome the generalized limitations to modify the cardiac phenotype of middle-aged and older women. Fifteen healthy postmenopausal women (52-75 yr) were recruited. Transthoracic echocardiography and central haemodynamics were assessed during incremental cycle ergometry (i) in baseline conditions, (ii) after standard (10%) blood withdrawal and (iii) subsequent 8-week ET. Main outcomes such as left ventricular (LV) function and structure and blood volume (BV) were determined. Phlebotomy induced a 0.5 ± 0.1 l reduction of BV, which was re-established after ET. Decrements in LV end-systolic volume (-27%) and increments in LV ejection fraction (+8%) during exercise as well as improved E/A ratio were detected after ET compared with baseline. In parallel, ET induced a 10% increment in LV mass without a concomitant increase in LV size. In conclusion, postmenopausal women exhibit large improvements in cardiac systolic and diastolic functions along with LV concentric remodelling in response to the sequenced combination of blood withdrawal and ET.
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Affiliation(s)
- Candela Diaz-Canestro
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | | | - David Montero
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.,Department of Cardiac Sciences, Cumming School of Medicine, Calgary, Alberta, Canada.,Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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12
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Pilmark NS, Oberholzer L, Halling JF, Kristensen JM, Bønding CP, Elkjær I, Lyngbæk M, Elster G, Siebenmann C, Holm NF, Birk JBB, Larsen EL, Meinild-Lundby AK, Wojtaszewski JF, Pilegaard H, Poulsen H, Pedersen BK, Hansen KB, Karstoft K. Skeletal muscle adaptations to exercise are not influenced by metformin treatment in humans: secondary analyses of two randomised, clinical trials. Appl Physiol Nutr Metab 2021; 47:309-320. [PMID: 34784247 DOI: 10.1139/apnm-2021-0194] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Metformin and exercise both improve glycemic control, but in vitro studies have indicated that an interaction between metformin and exercise occurs in skeletal muscle, suggesting a blunting effect of metformin on exercise training adaptations. Two studies (a double-blind, parallel-group, randomized clinical trial conducted in 29 glucose-intolerant individuals and a double-blind, cross-over trial conducted in 15 healthy lean males) were included in this paper. In both studies, the effect of acute exercise +/- metformin treatment on different skeletal muscle variables, previously suggested to be involved in a pharmaco-physiological interaction between metformin and exercise, was assessed. Furthermore, in the parallel-group trial, the effect of 12 weeks of exercise training was assessed. Skeletal muscle biopsies were obtained before and after acute exercise and 12 weeks of exercise training, and mitochondrial respiration, oxidative stress and AMPK activation was determined. Metformin did not significantly affect the effects of acute exercise or exercise training on mitochondrial respiration, oxidative stress or AMPK activation, indicating that the response to acute exercise and exercise training adaptations in skeletal muscle is not affected by metformin treatment. Further studies are needed to investigate whether an interaction between metformin and exercise is present in other tissues, e.g. the gut. Trial registration: ClinicalTrials.gov (NCT03316690 and NCT02951260). Novelty bullets • Metformin does not affect exercise-induced alterations in mitochondrial respiratory capacity in human skeletal muscle • Metformin does not affect exercise-induced alterations in systemic levels of oxidative stress nor emission of reactive oxygen species from human skeletal muscle • Metformin does not affect exercise-induced AMPK activation in human skeletal muscle.
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Affiliation(s)
- Nanna Skytt Pilmark
- Rigshospitalet, 53146, Centre for Physical Activity Research (CFAS), Copenhagen, Denmark;
| | - Laura Oberholzer
- Center for Physical Activity Research, University Hospital of Copenhagen, Blegdamsvej 9, Copenhagen, Denmark, 2100;
| | - Jens Frey Halling
- university of copenhagen, department of biology, , copenhagen, Denmark;
| | - Jonas M Kristensen
- University of Copenhagen, Denmark, Department of Nutrition, Exercise and Sports,, copenhagen, Denmark;
| | | | - Ida Elkjær
- Center for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark;
| | - Mark Lyngbæk
- Center for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark;
| | - Grit Elster
- Center for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark;
| | - Christoph Siebenmann
- Institute of Mountain Emergency Medicine,, EURAC Research, Bolzano, Italy, bolzano, Italy;
| | - Niels Frederich Holm
- Center for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark;
| | - Jesper Bratz Bratz Birk
- University of Copenhagen, Denmark, Department of Nutrition, Exercise and Sports,, copenhagen, Denmark;
| | - Emil List Larsen
- Copenhagen University Hospital, 53146, Department of Clinical Pharmacology, Bispebjerg and Frederiksberg Hospital, Kobenhavn, Denmark;
| | | | - J F Wojtaszewski
- University of Copenhagen, Denmark, Department of Nutrition, Exercise and Sports,, copenhagen, Denmark;
| | | | - Henrik Poulsen
- Copenhagen University Hospital, 53146, Department of Clinical Pharmacology, Bispebjerg and Frederiksberg Hospital, Kobenhavn, Denmark;
| | - Bente Klarlund Pedersen
- Rigshospitalet, 53146, Centre of Inflammation and Metabolism / Centre for Physical Activity Research (CIM/CFAS), København, Denmark;
| | - Katrine Bagge Hansen
- Steno Diabetes Center Copenhagen, 53138, Steno Diabetes Center Copenhagen, Gentofte, Denmark, Gentofte, Denmark;
| | - Kristian Karstoft
- Rigshospitalet, 53146, Centre for Physical Activity Research (CFAS), Blegdamsvej 9, Copenhagen, Denmark, 2100.,Bispebjerg Hospital, 53166, Department of Clinical Pharmacology, Copenhagen, Denmark, 2400;
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13
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Siebenmann C, Sorensen H, Bonne TC, Zaar M, Aachmann-Andersen NJ, Nordsborg NB, Nielsen HB, Secher NH, Lundby C, Rasmussen P. Cerebral lactate uptake during exercise is driven by the increased arterial lactate concentration. J Appl Physiol (1985) 2021; 131:1824-1830. [PMID: 34734784 DOI: 10.1152/japplphysiol.00505.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise facilitates cerebral lactate uptake, likely by increasing arterial lactate concentration and hence the diffusion gradient across the blood brain barrier. However, non-specific β-adrenergic blockade by propranolol has previously reduced the arterio-jugular venous lactate difference (AVLac) during exercise, suggesting β-adrenergic control of cerebral lactate uptake. Alternatively, we hypothesize that propranolol reduces cerebral lactate uptake by decreasing arterial lactate concentration. To test that hypothesis, we evaluated cerebral lactate uptake taking changes in arterial concentration into account. Nine healthy males performed incremental cycling exercise to exhaustion with and without intravenous propranolol (18.7 ± 1.9 mg). Lactate concentration was determined in arterial and internal jugular venous blood at the end of each workload. To take changes in arterial lactate into account we calculated the fractional extraction (FELac) defined as AVLac divided by the arterial lactate concentration. Arterial lactate concentration was reduced by propranolol at any workload (p<0.05), reaching 14 ± 3 and 11 ± 3 mmol l-1 during maximal exercise without and with propranolol, respectively. While AVLac and FELac increased during exercise (both p<0.05), they were both unaffected by propranolol at any workload (p=0.68 and p=0.26) or for any given arterial lactate concentration (p=0.78 and p=0.22). These findings support that, while propranolol may reduce cerebral lactate uptake, this effect reflects the propranolol-induced reduction in arterial lactate concentration and not inhibition of a β-adrenergic mechanism within the brain. We hence conclude that cerebral lactate uptake during exercise is directly driven by the increasing arterial concentration with work rate.
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Affiliation(s)
- Christoph Siebenmann
- Zurich Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Zurich, Switzerland.,Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Henrik Sorensen
- Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Christian Bonne
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Morten Zaar
- Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | - Niels Henry Secher
- Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Carsten Lundby
- Zurich Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Zurich, Switzerland.,Innland Norway University of Applied Sciences, Lillehammer, Norway
| | - Peter Rasmussen
- Zurich Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, Zurich, Switzerland
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14
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Diaz-Canestro C, Siebenmann C, Montero D. Blood Oxygen Carrying Capacity Determines Cardiorespiratory Fitness in Middle-Age and Older Women and Men. Med Sci Sports Exerc 2021; 53:2274-2282. [PMID: 34107511 DOI: 10.1249/mss.0000000000002720] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
PURPOSE Whether blood oxygen (O2)-carrying capacity plays a substantial role in determining cardiorespiratory fitness, a strong predictor of mortality, remains uncertain in women and elderly individuals because of the scarcity of experimental investigations. This study experimentally assessed the role of blood O2-carrying capacity on cardiorespiratory fitness in middle-age and older individuals. METHODS Healthy women and men (n = 31, 35-76 yr) matched by age and fitness were recruited. Transthoracic echocardiography, central hemodynamics, and O2 uptake were assessed throughout incremental exercise in (i) control conditions and (ii) after a 10% reduction of blood O2-carrying capacity via carbon monoxide administration, in a blinded manner. Effects on cardiac function, blood pressure, peak O2 uptake, and effective hemoglobin (Hb) were determined with established methods. RESULTS Blood O2-carrying capacity, represented by effective Hb, was similarly reduced in women (11.8 ± 0.6 vs 10.7 ± 0.6 g·dL-1, P < 0.001) and men (13.0 ± 0.9 vs 11.7 ± 0.6 g·dL-1, P < 0.001) (P for sex effect = 0.580). Reduced O2-carrying capacity did not induce major effects on cardiac function and hemodynamics during exercise, except for a 10%-15% decrement in peak systolic blood pressure in both sexes (P ≤ 0.034). Peak O2 uptake decreased from 35 ± 6 to 31 ± 6 mL·min-1·kg-1, P < 0.001) in women and from 35 ± 9 to 32 ± 9 mL·min-1·kg-1 (P = 0.024) in men in approximate proportion to the reduction of O2-carrying capacity, an effect that did not differ between sexes (P = 0.778). CONCLUSIONS Blood O2-carrying capacity stands out as a major determinant of cardiorespiratory fitness in healthy mature women and men, with no differential effect of sex.
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15
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Gatterer H, Rauch S, Regli IB, Woyke S, Schlittler M, Turner R, Strapazzon G, Brugger H, Goetze JP, Feraille E, Siebenmann C. Plasma volume contraction reduces atrial natriuretic peptide after four days of hypobaric hypoxia exposure. Am J Physiol Regul Integr Comp Physiol 2021; 320:R526-R531. [PMID: 33533684 DOI: 10.1152/ajpregu.00313.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether low arterial oxygen tension ([Formula: see text]) or hypoxia-induced plasma volume (PV) contraction, which reduces central blood volume (BV) and atrial distension, explain reduction in circulating atrial natriuretic peptide (ANP) after prolonged hypoxic exposure. Ten healthy males were exposed for 4 days to hypobaric hypoxia corresponding to an altitude of 3,500 m. PV changes were determined by carbon monoxide rebreathing. Venous plasma concentrations of midregional proANP (MR-proANP) were measured before and at the end of the exposure. At the latter time point, the measurement was repeated after 1) restoration of [Formula: see text] by breathing a hyperoxic gas mixture for 30 min and 2) restoration of BV by fluid infusion. Correspondingly, left ventricular end-diastolic volume (LVEDV), left atrial area (LAA), and right atrial area (RAA) were determined by ultrasound before exposure and both before and after fluid infusion at the end of the exposure. Hypoxic exposure reduced MR-proANP from 37.9 ± 18.5 to 24.5 ± 10.3 pmol/L (P = 0.034), LVEDV from 107.4 ± 33.5 to 91.6 ± 26.3 mL (P = 0.005), LAA from 15.8 ± 4.9 to 13.3 ± 4.2 cm2 (P = 0.007), and RAA from 16.2 ± 3.1 to 14.3 ± 3.5 cm2 (P = 0.001). Hyperoxic breathing did not affect MR-proANP (24.8 ± 12.3 pmol/L, P = 0.890). Conversely, fluid infusion restored LVEDV, LAA, and RAA to near-baseline values (108.0 ± 29.3 mL, 17.2 ± 5.7 cm2, and 17.2 ± 3.1 cm2, respectively, P > 0.05 vs. baseline) and increased MR-proANP to 29.5 ± 13.3 pmol/L (P = 0.010 vs. preinfusion and P = 0.182 vs. baseline). These findings support that ANP reduction in hypoxia is at least partially attributed to plasma volume contraction, whereas reduced [Formula: see text] does not seem to contribute.
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Affiliation(s)
- Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Simon Rauch
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
| | - Ivo B Regli
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
| | - Simon Woyke
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Maja Schlittler
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hermann Brugger
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Jens P Goetze
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Eric Feraille
- National Center of Competence in Research Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland.,Department of Cellular Physiology and Metabolism, University of Geneva, University Medical Center, Geneva, Switzerland
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16
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AlSalahi SE, Junejo RT, Bradley C, Balanos GM, Siebenmann C, Fisher JP. The middle cerebral artery blood velocity response to acute normobaric hypoxia occurs independently of changes in ventilation in humans. Exp Physiol 2021; 106:861-867. [PMID: 33527604 DOI: 10.1113/ep089127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 01/28/2021] [Indexed: 12/22/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does the ventilatory response to moderate acute hypoxia increase cerebral perfusion independently of changes in arterial oxygen tension in humans? What is the main finding and its importance? The ventilatory response does not increase middle cerebral artery mean blood velocity during moderate isocapnic acute hypoxia beyond that elicited by reduced oxygen saturation. ABSTRACT Hypoxia induces ventilatory, cardiovascular and cerebrovascular adjustments to defend against reductions in systemic oxygen delivery. We aimed to determine whether the ventilatory response to moderate acute hypoxia increases cerebral perfusion independently of changes in arterial oxygenation. Eleven young healthy individuals were exposed to four 15 min experimental conditions: (1) normoxia (partial pressure of end-tidal oxygen, P ET O 2 = 100 mmHg), (2) hypoxia ( P ET O 2 = 50 mmHg), (3) normoxia with breathing volitionally matched to levels observed during hypoxia (hyperpnoea; P ET O 2 = 100 mmHg) and (4) hypoxia ( P ET O 2 = 50 mmHg) with respiratory frequency and tidal volume volitionally matched to levels observed during normoxia (i.e., restricted breathing (RB)). Isocapnia was maintained in all conditions. Middle cerebral artery mean blood velocity (MCA Vmean ), assessed by transcranial Doppler ultrasound, was increased during hypoxia (58 ± 12 cm/s, P = 0.04) and hypoxia + RB (61 ± 14 cm/s, P < 0.001) compared to normoxia (55 ± 11 cm/s), while it was unchanged during hyperpnoea (52 ± 13 cm/s, P = 0.08). MCA Vmean was not different between hypoxia and hypoxia + RB (P > 0.05). These findings suggest that the hypoxic ventilatory response does not increase cerebral perfusion, indexed using MCA Vmean , during moderate isocapnic acute hypoxia beyond that elicited by reduced oxygen saturation.
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Affiliation(s)
- Sultan E AlSalahi
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Rehan T Junejo
- Department of Life Sciences, Manchester Metropolitan University, Manchester, UK
| | - Chris Bradley
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - George M Balanos
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | | | - James P Fisher
- Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, Auckland, New Zealand
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17
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Pilmark NS, Lyngbæk M, Oberholzer L, Elkjær I, Petersen-Bønding C, Kofoed K, Siebenmann C, Kellenberger K, van Hall G, Abildgaard J, Ellingsgaard H, Lauridsen C, Ried-Larsen M, Pedersen BK, Hansen KB, Karstoft K. The interaction between metformin and physical activity on postprandial glucose and glucose kinetics: a randomised, clinical trial. Diabetologia 2021; 64:397-409. [PMID: 32979074 DOI: 10.1007/s00125-020-05282-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 08/10/2020] [Indexed: 01/04/2023]
Abstract
AIMS/HYPOTHESIS The aim of this parallel-group, double-blinded (study personnel and participants), randomised clinical trial was to assess the interaction between metformin and exercise training on postprandial glucose in glucose-intolerant individuals. METHODS Glucose-intolerant (2 h OGTT glucose of 7.8-11.0 mmol/l and/or HbA1c of 39-47 mmol/mol [5.7-6.5%] or glucose-lowering-medication naive type 2 diabetes), overweight/obese (BMI 25-42 kg/m2) individuals were randomly allocated to a placebo study group (PLA, n = 15) or a metformin study group (MET, n = 14), and underwent 3 experimental days: BASELINE (before randomisation), MEDICATION (after 3 weeks of metformin [2 g/day] or placebo treatment) and TRAINING (after 12 weeks of exercise training in combination with metformin/placebo treatment). Training consisted of supervised bicycle interval sessions with a mean intensity of 64% of Wattmax for 45 min, 4 times/week. The primary outcome was postprandial glucose (mean glucose concentration) during a mixed meal tolerance test (MMTT), which was assessed on each experimental day. For within-group differences, a group × time interaction was assessed using two-way repeated measures ANOVA. Between-group changes of the outcomes at different timepoints were compared using unpaired two-tailed Student's t tests. RESULTS Postprandial glucose improved from BASELINE to TRAINING in both the PLA group and the MET group (∆PLA: -0.7 [95% CI -1.4, 0.0] mmol/l, p = 0.05 and ∆MET: -0.7 [-1.5, -0.0] mmol/l, p = 0.03), with no between-group difference (p = 0.92). In PLA, the entire reduction was seen from MEDICATION to TRAINING (-0.8 [-1.3, -0.1] mmol/l, p = 0.01). Conversely, in MET, the entire reduction was observed from BASELINE to MEDICATION (-0.9 [-1.6, -0.2] mmol/l, p = 0.01). The reductions in mean glucose concentration during the MMTT from BASELINE to TRAINING were dependent on differential time effects: in the PLA group, a decrease was observed at timepoint (t) = 120 min (p = 0.009), whereas in the MET group, a reduction occurred at t = 30 min (p < 0.001). V̇O2peak increased 15% (4.6 [3.3, 5.9] ml kg-1 min-1, p < 0.0001) from MEDICATION to TRAINING and body weight decreased (-4.0 [-5.2, -2.7] kg, p < 0.0001) from BASELINE to TRAINING, with no between-group differences (p = 0.7 and p = 0.5, respectively). CONCLUSIONS/INTERPRETATION Metformin plus exercise training was not superior to exercise training alone in improving postprandial glucose. The differential time effects during the MMTT suggest an interaction between the two modalities. FUNDING The Beckett foundation, A.P Møller Foundation, DDA, the Research Foundation of Rigshospitalet and Trygfonden. TRIAL REGISTRATION ClinicalTrials.gov (NCT03316690). Graphical abstract.
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Affiliation(s)
- Nanna S Pilmark
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Mark Lyngbæk
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Laura Oberholzer
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Ida Elkjær
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christina Petersen-Bønding
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Katja Kofoed
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christoph Siebenmann
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Katja Kellenberger
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Section for Elite Sport, Swiss Federal Institute of Sports, Magglingen, Switzerland
| | - Gerrit van Hall
- Biomedical Sciences, Faculty of Health & Medical Science, University of Copenhagen, Copenhagen, Denmark
- Clinical Metabolomics Core Facility, Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
| | - Julie Abildgaard
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Growth and Reproduction, Rigshospitalet, Copenhagen, Denmark
| | - Helga Ellingsgaard
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Carsten Lauridsen
- Department of Diagnostic Radiology, Copenhagen University Hospital, Copenhagen, Denmark
- Copenhagen University College, Copenhagen N, Denmark
| | - Mathias Ried-Larsen
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Bente K Pedersen
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - Kristian Karstoft
- Centre for Physical Activity Research (CFAS), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
- Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
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18
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Schlittler M, Gatterer H, Turner R, Regli IB, Woyke S, Strapazzon G, Rasmussen P, Kob M, Mueller T, Goetze JP, Maillard M, van Hall G, Feraille E, Siebenmann C. Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude. J Physiol 2020; 599:1083-1096. [PMID: 33124686 PMCID: PMC7894546 DOI: 10.1113/jp280601] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 10/27/2020] [Indexed: 12/16/2022] Open
Abstract
Key points Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O2 content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH‐induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra‐ to the extravascular space, rather than fluid loss, as the mechanism underlying HH‐induced PV contraction.
Abstract Extended hypoxic exposure reduces plasma volume (PV). The mechanisms underlying this effect are controversial, possibly as previous studies have been confounded by inconsistent experimental conditions. Here, we investigated the effect of hypobaric hypoxia (HH) on PV in a cross‐over study that strictly controlled for diet, water intake, physical activity and temperature. Eleven males completed two 4‐day sojourns in a hypobaric chamber, one in normoxia (NX) and one in HH equivalent to 3500 m altitude. PV, urine output, volume‐regulating hormones and plasma protein concentration were determined daily. Total body water (TBW) was determined at the end of both sojourns by deuterium dilution. Although PV was 8.1 ± 5.8% lower in HH than in NX after 24 h and remained ∼10% lower thereafter (all P < 0.002), no differences were detected in TBW (P = 0.17) or in 24 h urine volumes (all P > 0.23). Plasma renin activity and circulating aldosterone were suppressed in HH during the first half of the sojourn (all P < 0.05) but thereafter similar to NX, whereas no differences were detected for copeptin between sojourns (all P > 0.05). Markers for atrial natriuretic peptide were higher in HH than NX after 30 min (P = 0.001) but lower during the last 2 days (P < 0.001). While plasma protein concentration was similar between sojourns, total circulating protein mass (TCP) was reduced in HH at the same time points as PV (all P < 0.03). Despite transient hormonal changes favouring increased diuresis, HH did not enhance urine output. Instead, the maintained TBW and reduced TCP support an oncotically driven fluid redistribution into the extravascular compartment as the mechanism underlying PV contraction. Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O2 content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH‐induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra‐ to the extravascular space, rather than fluid loss, as the mechanism underlying HH‐induced PV contraction.
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Affiliation(s)
- Maja Schlittler
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Ivo B Regli
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, 'F. Tappeiner' Hospital, Merano, Italy
| | - Simon Woyke
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy.,Department of Anaesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Austria
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | | | - Michael Kob
- Division of Clinical Nutrition, Bolzano Regional Hospital, Bolzano, Italy
| | - Thomas Mueller
- Department of Clinical Pathology, Hospital of Bolzano, Bolzano, Italy
| | - Jens P Goetze
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Marc Maillard
- Service of Nephrology, University Hospital of Lausanne, Lausanne, Switzerland
| | - Gerrit van Hall
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Clinical Metabolomics Core Facility, Rigshospitalet, University of Copenhagen, Denmark
| | - Eric Feraille
- National Center of Competence in Research Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland.,Department of Cellular Physiology and Metabolism, University of Geneva University Medical Center, Geneva, Switzerland
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19
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Tremblay JC, Ainslie PN, Turner R, Gatterer H, Schlittler M, Woyke S, Regli IB, Strapazzon G, Rauch S, Siebenmann C. Endothelial function and shear stress in hypobaric hypoxia: time course and impact of plasma volume expansion in men. Am J Physiol Heart Circ Physiol 2020; 319:H980-H994. [PMID: 32886005 DOI: 10.1152/ajpheart.00597.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High-altitude exposure typically reduces endothelial function, and this is modulated by hemoconcentration resulting from plasma volume contraction. However, the specific impact of hypobaric hypoxia independent of external factors (e.g., cold, varying altitudes, exercise, diet, and dehydration) on endothelial function is unknown. We examined the temporal changes in blood viscosity, shear stress, and endothelial function and the impact of plasma volume expansion (PVX) during exposure to hypobaric hypoxia while controlling for external factors. Eleven healthy men (25 ± 4 yr, mean ± SD) completed two 4-day chamber visits [normoxia (NX) and hypobaric hypoxia (HH; equivalent altitude, 3,500 m)] in a crossover design. Endothelial function was assessed via flow-mediated dilation in response to transient (reactive hyperemia; RH-FMD) and sustained (progressive handgrip exercise; SS-FMD) increases in shear stress before entering and after 1, 6, 12, 48, and 96 h in the chamber. During HH, endothelial function was also measured on the last day after PVX to preexposure levels (1,140 ± 320 mL balanced crystalloid solution). Blood viscosity and arterial shear stress increased on the first day during HH compared with NX and remained elevated at 48 and 96 h (P < 0.005). RH-FMD did not differ during HH compared with NX and was unaffected by PVX despite reductions in blood viscosity (P < 0.05). The stimulus-response slope of increases in shear stress to vasodilation during SS-FMD was preserved in HH and increased by 44 ± 73% following PVX (P = 0.023). These findings suggest that endothelial function is maintained in HH when other stressors are absent and that PVX improves endothelial function in a shear-stress stimulus-specific manner.NEW & NOTEWORTHY Using a normoxic crossover study design, we examined the impact of hypobaric hypoxia (4 days; altitude equivalent, 3,500 m) and hemoconcentration on blood viscosity, shear stress, and endothelial function. Blood viscosity increased during the hypoxic exposure and was accompanied by elevated resting and exercising arterial shear stress. Flow-mediated dilation stimulated by reactive hyperemia and handgrip exercise was preserved throughout the hypoxic exposure. Plasma volume expansion reversed the hypoxia-associated hemoconcentration and selectively increased handgrip exercise flow-mediated dilation.
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Affiliation(s)
- Joshua C Tremblay
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, Kelowna, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, Kelowna, Canada
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Maja Schlittler
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Simon Woyke
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Ivo B Regli
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesiology and Intensive Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Simon Rauch
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Department of Anesthesia and Intensive Care Medicine, "F. Tappeiner" Hospital, Merano, Italy
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20
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Affiliation(s)
| | - Jerome A Dempsey
- Department Population Health Sciences, University of Wisconsin-Madison, Madison, WI
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21
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Mikkelsen CJ, Junge N, Piil JF, Morris NB, Oberholzer L, Siebenmann C, Lundby C, Nybo L. Prolonged Heat Acclimation and Aerobic Performance in Endurance Trained Athletes. Front Physiol 2019; 10:1372. [PMID: 31749712 PMCID: PMC6843002 DOI: 10.3389/fphys.2019.01372] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Accepted: 10/16/2019] [Indexed: 11/17/2022] Open
Abstract
Heat acclimation (HA) involves physiological adaptations that directly promote exercise performance in hot environments. However, for endurance-athletes it is unclear if adaptations also improve aerobic capacity and performance in cool conditions, partly because previous randomized controlled trial (RCT) studies have been restricted to short intervention periods. Prolonged HA was therefore deployed in the present RCT study including 21 cyclists [38 ± 2 years, 184 ± 1 cm, 80.4 ± 1.7 kg, and maximal oxygen uptake (VO2max) of 58.1 ± 1.2 mL/min/kg; mean ± SE] allocated to either 5½ weeks of training in the heat [HEAT (n = 12)] or cool control [CON (n = 9)]. Training registration, familiarization to test procedures, determination of VO2max, blood volume and 15 km time trial (TT) performance were assessed in cool conditions (14°C) during a 2-week lead-in period, as well as immediately pre and post the intervention. Participants were instructed to maintain total training volume and complete habitual high intensity intervals in normal settings; but HEAT substituted part of cool training with 28 ± 2 sessions in the heat (1 h at 60% VO2max in 40°C; eliciting core temperatures above 39°C in all sessions), while CON completed all training in cool conditions. Acclimation for HEAT was verified by lower sweat sodium [Na+], reduced steady-state heart rate and improved submaximal exercise endurance in the heat. However, when tested in cool conditions both peak power output and VO2max remained unchanged for HEAT (pre 60.0 ± 1.5 vs. 59.8 ± 1.3 mL O2/min/kg). TT performance tested in 14°C was improved for HEAT and average power output increased from 298 ± 6 to 315 ± 6 W (P < 0.05), but a similar improvement was observed for CON (from 294 ± 11 to 311 ± 10 W). Based on the present findings, we conclude that training in the heat was not superior compared to normal (control) training for improving aerobic power or TT performance in cool conditions.
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Affiliation(s)
- C. Jacob Mikkelsen
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Nicklas Junge
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Jacob F. Piil
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Nathan B. Morris
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Laura Oberholzer
- Centre for Physical Activity Research, Copenhagen University Hospital, Copenhagen, Denmark
| | - Christoph Siebenmann
- Centre for Physical Activity Research, Copenhagen University Hospital, Copenhagen, Denmark
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - Carsten Lundby
- Centre for Physical Activity Research, Copenhagen University Hospital, Copenhagen, Denmark
- Innland Norway University of Applied Sciences, Lillehammer, Norway
| | - Lars Nybo
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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22
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Oberholzer L, Siebenmann C, Mikkelsen CJ, Junge N, Piil JF, Morris NB, Goetze JP, Meinild Lundby AK, Nybo L, Lundby C. Hematological Adaptations to Prolonged Heat Acclimation in Endurance-Trained Males. Front Physiol 2019; 10:1379. [PMID: 31749713 PMCID: PMC6842970 DOI: 10.3389/fphys.2019.01379] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 10/18/2019] [Indexed: 11/13/2022] Open
Abstract
Heat acclimation is associated with plasma volume (PV) expansion that occurs within the first week of exposure. However, prolonged effects on hemoglobin mass (Hbmass) are unclear as intervention periods in previous studies have not allowed sufficient time for erythropoiesis to manifest. Therefore, Hbmass, intravascular volumes, and blood volume (BV)-regulating hormones were assessed with 5½ weeks of exercise-heat acclimation (HEAT) or matched training in cold conditions (CON) in 21 male cyclists [(mean ± SD) age: 38 ± 9 years, body weight: 80.4 ± 7.9 kg, VO2peak: 59.1 ± 5.2 ml/min/kg]. HEAT (n = 12) consisted of 1 h cycling at 60% VO2peak in 40°C for 5 days/week in addition to regular training, whereas CON (n = 9) trained exclusively in cold conditions (<15°C). Before and after the intervention, Hbmass and intravascular volumes were assessed by carbon monoxide rebreathing, while reticulocyte count and BV-regulating hormones were measured before, after 2 weeks and post intervention. Total training volume during the intervention was similar (p = 0.282) between HEAT (509 ± 173 min/week) and CON (576 ± 143 min/week). PV increased (p = 0.004) in both groups, by 303 ± 345 ml in HEAT and 188 ± 286 ml in CON. There was also a main effect of time (p = 0.038) for Hbmass with +34 ± 36 g in HEAT and +2 ± 33 g in CON and a tendency toward a higher increase in Hbmass in HEAT compared to CON (time × group interaction: p = 0.061). The Hbmass changes were weakly correlated to alterations in PV (r = 0.493, p = 0.023). Reticulocyte count and BV-regulating hormones remained unchanged for both groups. In conclusion, Hbmass was slightly increased following prolonged training in the heat and although the mechanistic link remains to be revealed, the increase could represent a compensatory response in erythropoiesis secondary to PV expansion.
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Affiliation(s)
- Laura Oberholzer
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christoph Siebenmann
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - C. Jacob Mikkelsen
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nicklas Junge
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob F. Piil
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nathan B. Morris
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens P. Goetze
- Department of Clinical Biochemistry, University of Copenhagen, Copenhagen, Denmark
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne-Kristine Meinild Lundby
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Lars Nybo
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Carsten Lundby
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Innland Norway University of Applied Sciences, Lillehammer, Norway
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23
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Oberholzer L, Siebenmann C, Mikkelsen CJ, Junge N, Piil JF, Morris NB, Goetze JP, Meinild Lundby AK, Nybo L, Lundby C. Hematological Adaptations to Prolonged Heat Acclimation in Endurance-Trained Males. Front Physiol 2019. [PMID: 31749713 DOI: 10.3389/fphys.2019.01379, 10.3389/fpls.2019.01379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Heat acclimation is associated with plasma volume (PV) expansion that occurs within the first week of exposure. However, prolonged effects on hemoglobin mass (Hbmass) are unclear as intervention periods in previous studies have not allowed sufficient time for erythropoiesis to manifest. Therefore, Hbmass, intravascular volumes, and blood volume (BV)-regulating hormones were assessed with 5½ weeks of exercise-heat acclimation (HEAT) or matched training in cold conditions (CON) in 21 male cyclists [(mean ± SD) age: 38 ± 9 years, body weight: 80.4 ± 7.9 kg, VO2peak: 59.1 ± 5.2 ml/min/kg]. HEAT (n = 12) consisted of 1 h cycling at 60% VO2peak in 40°C for 5 days/week in addition to regular training, whereas CON (n = 9) trained exclusively in cold conditions (<15°C). Before and after the intervention, Hbmass and intravascular volumes were assessed by carbon monoxide rebreathing, while reticulocyte count and BV-regulating hormones were measured before, after 2 weeks and post intervention. Total training volume during the intervention was similar (p = 0.282) between HEAT (509 ± 173 min/week) and CON (576 ± 143 min/week). PV increased (p = 0.004) in both groups, by 303 ± 345 ml in HEAT and 188 ± 286 ml in CON. There was also a main effect of time (p = 0.038) for Hbmass with +34 ± 36 g in HEAT and +2 ± 33 g in CON and a tendency toward a higher increase in Hbmass in HEAT compared to CON (time × group interaction: p = 0.061). The Hbmass changes were weakly correlated to alterations in PV (r = 0.493, p = 0.023). Reticulocyte count and BV-regulating hormones remained unchanged for both groups. In conclusion, Hbmass was slightly increased following prolonged training in the heat and although the mechanistic link remains to be revealed, the increase could represent a compensatory response in erythropoiesis secondary to PV expansion.
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Affiliation(s)
- Laura Oberholzer
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christoph Siebenmann
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | - C Jacob Mikkelsen
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nicklas Junge
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob F Piil
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nathan B Morris
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens P Goetze
- Department of Clinical Biochemistry, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne-Kristine Meinild Lundby
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Lars Nybo
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Carsten Lundby
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Innland Norway University of Applied Sciences, Lillehammer, Norway
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24
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Taylor CE, Boulton D, Howden EJ, Siebenmann C, Macefield VG. Central command increases muscle sympathetic nerve activity more to contracting than noncontracting muscle during rhythmic isotonic leg exercise. J Neurophysiol 2019; 121:1704-1710. [PMID: 30864865 DOI: 10.1152/jn.00075.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously shown that the increase in muscle sympathetic nerve activity (MSNA) to contracting muscle during sustained isometric exercise is due primarily to central command and that contracting muscle does not express a metaboreceptor-driven increase in MSNA. Here we tested the hypothesis that MSNA increases to the contracting muscle also during rhythmic isotonic exercise, in which muscle metabolites will not accumulate because the contraction is performed without external load. MSNA was recorded from the common peroneal nerve in 10 participants, and negative-going sympathetic spikes were extracted during 50 cycles of sinusoidal (0.15 Hz) isotonic dorsiflexions of the ipsilateral or contralateral ankle. Electromyographic activity (EMG) was recorded from the tibialis anterior muscle on both sides. Cross-correlation analysis between MSNA and EMG revealed a marked cyclic modulation of MSNA to the contracting (ipsilateral) muscle. This modulation, in which MSNA increased during the contraction phase, was three times greater than that to the noncontracting muscle (modulation index = 27.4 ± 3.2% vs. 9.2 ± 1.5%; P < 0.002). There were no differences in either the intensity or the magnitude of modulation of EMG during ipsilateral and contralateral contractions. We conclude that central command increases MSNA to the contracting muscle during rhythmic isotonic exercise. NEW & NOTEWORTHY Muscle sympathetic nerve activity (MSNA) increases to contracting muscle during isometric exercise, but whether this occurs during rhythmic isotonic exercise is unknown. We recorded MSNA to the pretibial flexors during cyclic dorsiflexion of the ipsilateral or contralateral ankle. MSNA showed a cyclic increase during the contraction phase that was significantly higher to the contracting than the noncontracting muscle, supporting central command as the primary mechanism responsible for increasing MSNA.
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Affiliation(s)
- Chloe E Taylor
- School of Science and Health, Western Sydney University , Sydney, New South Wales , Australia.,School of Medicine, Western Sydney University , Sydney, New South Wales , Australia
| | - Daniel Boulton
- School of Medicine, Western Sydney University , Sydney, New South Wales , Australia
| | - Erin J Howden
- Baker Heart and Diabetes Institute , Melbourne, Victoria , Australia
| | - Christoph Siebenmann
- Baker Heart and Diabetes Institute , Melbourne, Victoria , Australia.,The Centre for Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen , Copenhagen , Denmark
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Taylor CE, Boulton D, Howden E, Siebenmann C, Macefield VG. Central Command Increases Muscle Sympathetic Nerve Activity More to Contracting than Non‐Contracting Muscle during Unloaded Rhythmic Exercise in Humans. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.860.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Chloe E Taylor
- School of Science and HealthWestern Sydney UniversitySydneyAustralia
- School of MedicineWestern Sydney UniversitySydneyAustralia
| | - Daniel Boulton
- School of MedicineWestern Sydney UniversitySydneyAustralia
| | - Erin Howden
- Baker Heart and Diabetes InstituteMelbourneAustralia
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Siebenmann C, Ryrsø CK, Oberholzer L, Fisher JP, Hilsted LM, Rasmussen P, Secher NH, Lundby C. Hypoxia-induced vagal withdrawal is independent of the hypoxic ventilatory response in men. J Appl Physiol (1985) 2019; 126:124-131. [DOI: 10.1152/japplphysiol.00701.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxia increases heart rate (HR) in humans by sympathetic activation and vagal withdrawal. However, in anaesthetized dogs hypoxia increases vagal activity and reduces HR if pulmonary ventilation does not increase and we evaluated whether that observation applies to awake humans. Ten healthy males were exposed to 15 min of normoxia and hypoxia (10.5% O2), while respiratory rate and tidal volume were volitionally controlled at values identified during spontaneous breathing in hypoxia. End-tidal CO2 tension was clamped at 40 mmHg by CO2 supplementation. β-Adrenergic blockade by intravenous propranolol isolated vagal regulation of HR. During spontaneous breathing, hypoxia increased ventilation by 3.2 ± 2.1 l/min ( P = 0.0033) and HR by 8.9 ± 5.5 beats/min ( P < 0.001). During controlled breathing, respiratory rate (16.3 ± 3.2 vs. 16.4 ± 3.3 breaths/min) and tidal volume (1.05 ± 0.27 vs. 1.06 ± 0.24 l) were similar for normoxia and hypoxia, whereas the HR increase in hypoxia persisted without (8.6 ± 10.2 beats/min) and with (6.6 ± 5.6 beats/min) propranolol. Neither controlled breathing ( P = 0.80), propranolol ( P = 0.64), nor their combination ( P = 0.89) affected the HR increase in hypoxia. Arterial pressure was unaffected ( P = 0.48) by hypoxia across conditions. The hypoxia-induced increase in HR during controlled breathing and β-adrenergic blockade indicates that hypoxia reduces vagal activity in humans even when ventilation does not increase. Vagal withdrawal in hypoxia seems to be governed by the arterial chemoreflex rather than a pulmonary inflation reflex in humans. NEW & NOTEWORTHY Hypoxia accelerates the heart rate of humans by increasing sympathetic activity and reducing vagal activity. Animal studies have indicated that hypoxia-induced vagal withdrawal is governed by a pulmonary inflation reflex that is activated by the increased pulmonary ventilation in hypoxia. The present findings, however, indicate that humans experience vagal withdrawal in hypoxia even if ventilation does not increase, indicating that vagal withdrawal is governed by the arterial chemoreflex rather than a pulmonary inflation reflex.
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Affiliation(s)
- Christoph Siebenmann
- The Centre for Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Camilla K. Ryrsø
- The Centre for Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Laura Oberholzer
- The Centre for Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - James P. Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, United Kingdom
| | - Linda M. Hilsted
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - Niels H. Secher
- Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Carsten Lundby
- The Centre for Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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Keramidas ME, Siebenmann C, Norrbrand L, Gadefors M, Eiken O. A brief pre-exercise nap may alleviate physical performance impairments induced by short-term sustained operations with partial sleep deprivation – A field-based study. Chronobiol Int 2018; 35:1464-1470. [PMID: 29985669 DOI: 10.1080/07420528.2018.1490316] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Michail E. Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, Royal Institute of Technology-KTH, Stockholm, Sweden
| | - Christoph Siebenmann
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, Royal Institute of Technology-KTH, Stockholm, Sweden
| | - Lena Norrbrand
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, Royal Institute of Technology-KTH, Stockholm, Sweden
| | | | - Ola Eiken
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, Royal Institute of Technology-KTH, Stockholm, Sweden
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Robach P, Pichon A, Siebenmann C, Rønnestad BR, Lundby C. Response to Millet and Brocherie. Scand J Med Sci Sports 2018; 28:2244-2245. [PMID: 29981191 DOI: 10.1111/sms.13262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Paul Robach
- Ecole Nationale des Sports de Montagne, Site de l'Ecole Nationale de Ski et d'Alpinisme, Chamonix, France
| | - Aurélien Pichon
- Laboratory Mobility, Aging & Exercise (MOVE) - EA 6314, Faculty of Sport Sciences, University of Poitiers, Poitiers, France
| | - Christoph Siebenmann
- The Centre for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark
| | - Bent R Rønnestad
- Inland Norway University of Applied Sciences, Lillehammer, Norway
| | - Carsten Lundby
- The Centre for Physical Activity Research, University Hospital of Copenhagen, Copenhagen, Denmark
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Ryrsø CK, Thaning P, Siebenmann C, Lundby C, Lange P, Pedersen BK, Hellsten Y, Iepsen UW. Effect of endurance versus resistance training on local muscle and systemic inflammation and oxidative stress in COPD. Scand J Med Sci Sports 2018; 28:2339-2348. [DOI: 10.1111/sms.13227] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2018] [Indexed: 12/25/2022]
Affiliation(s)
- C. K. Ryrsø
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
| | - P. Thaning
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
- Department of Respiratory Medicine; University Hospital Hvidovre; Copenhagen Denmark
| | - C. Siebenmann
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
| | - C. Lundby
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
| | - P. Lange
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
- Department of Public Health, Section of Social Medicine; University of Copenhagen; Copenhagen Denmark
- Medical Department O, Respiratory Section; Herlev and Gentofte Hospital; Herlev Denmark
| | - B. K. Pedersen
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
| | - Y. Hellsten
- Department of Nutrition, Exercise, and Sports; University of Copenhagen; Copenhagen Denmark
| | - U. W. Iepsen
- The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research; Rigshospitalet, University of Copenhagen; Copenhagen Denmark
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Kölegård R, Da Silva C, Siebenmann C, Keramidas ME, Eiken O. Cardiac performance is influenced by rotational changes of position in the transversal plane, both in the horizontal and in the 60̊ head-up postures. Clin Physiol Funct Imaging 2018; 38:1021-1028. [PMID: 29697185 DOI: 10.1111/cpf.12520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/19/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND Echocardiography is usually performed with the subject/patient lying in the left lateral position (LLP), because the acoustic window is better in this than in the supine position (SP). The aim was to investigate cardiac responses to rotational changes of position in the transversal plane, from SP to LLP while horizontal, and from leaning on the back (HUT-LB) to leaning on the left side (HUT-LL) while tilted 60° head-up from the horizontal. METHODS Healthy men (n = 12) underwent 10-min HUT provocations. Cardiac variables were measured using two-dimensional echocardiography, Doppler, tissue Doppler imaging and arterial pressures using a volume-clamp method. RESULTS In horizontal posture, cardiac volumes were smaller in SP than in LLP: end-diastolic volume (EDV) by 14%, end-systolic volume (ESV) by 13%, stroke volume (SV) by 14%, and cardiac output (CO) by 16% (P<0·03). In addition, the mitral annular plane systolic excursion (MAPSE) was 11% smaller (P = 0·001) and the left ventricle isovolumic relaxation time (IVRT) 27% longer in SP than in LLP. The ejection fraction, heart rate, arterial pressure and pulmonary ventilation were similar in SP and LLP. During HUT, EDV, SV, CO and MAPSE were smaller, and IVRT was longer, in HUT-LB than in HUT-LL, by -19%, -20%, -17%, -18% and +35%, respectively (P<0·04). CONCLUSIONS Cardiac performance is enhanced in LLP versus SP and in HUT-LL versus HUT-LB, which can be attributed to improved venous return, conceivably, wholly or in part, due to increased hydrostatic pressure gradients between the caval veins and the heart in the LLP and HUT-LL positions.
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Affiliation(s)
- Roger Kölegård
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre (SAPC, KTH, CBH), Royal Institute of Technology, Solna, Sweden
| | - Cristina Da Silva
- Department of Physiology, Karolinska University Hospital, Stockholm, Sweden
| | - Christoph Siebenmann
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre (SAPC, KTH, CBH), Royal Institute of Technology, Solna, Sweden
| | - Michail E Keramidas
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre (SAPC, KTH, CBH), Royal Institute of Technology, Solna, Sweden
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre (SAPC, KTH, CBH), Royal Institute of Technology, Solna, Sweden
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Robach P, Hansen J, Pichon A, Meinild Lundby AK, Dandanell S, Slettaløkken Falch G, Hammarström D, Pesta DH, Siebenmann C, Keiser S, Kérivel P, Whist JE, Rønnestad BR, Lundby C. Hypobaric live high-train low does not improve aerobic performance more than live low-train low in cross-country skiers. Scand J Med Sci Sports 2018; 28:1636-1652. [DOI: 10.1111/sms.13075] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/13/2018] [Indexed: 01/16/2023]
Affiliation(s)
- P. Robach
- Ecole Nationale des Sports de Montagne; site de l'Ecole Nationale de Ski et d'Alpinisme; Chamonix France
- HP2, Université Grenoble Alpes; Grenoble France
| | - J. Hansen
- Inland Norway University of Applied Sciences; Lillehammer Norway
| | - A. Pichon
- Laboratory Mobility, Aging & Exercise (MOVE) - EA 6314; Faculty of Sport Sciences; University of Poitiers; Poitiers France
| | - A.-K. Meinild Lundby
- The Centre for Physical Activity Research; University Hospital of Copenhagen; Copenhagen Denmark
| | - S. Dandanell
- Center for Healthy Aging; Department of Biomedical Sciences; XLab; University of Copenhagen; Copenhagen Denmark
- Department for Physiotherapy and Occupational Therapy; Metropolitan University College; Copenhagen Denmark
| | | | - D. Hammarström
- Inland Norway University of Applied Sciences; Lillehammer Norway
| | - D. H. Pesta
- Department of Sport Science; Faculty for Sports Science and Psychology; University of Innsbruck; Innsbruck Austria
- Department of Visceral, Transplant, and Thoracic Surgery; D. Swarovski Research Laboratory; Medical University of Innsbruck; Innsbruck Austria
| | - C. Siebenmann
- The Centre for Physical Activity Research; University Hospital of Copenhagen; Copenhagen Denmark
| | - S. Keiser
- Institute of Physiology; University of Zürich; Zürich Switzerland
| | - P. Kérivel
- Ecole Nationale des Sports de Montagne; site de l'Ecole Nationale de Ski et d'Alpinisme; Chamonix France
| | - J. E. Whist
- Innlandet Hospital Trust; Lillehammer Norway
| | - B. R. Rønnestad
- Inland Norway University of Applied Sciences; Lillehammer Norway
| | - C. Lundby
- The Centre for Physical Activity Research; University Hospital of Copenhagen; Copenhagen Denmark
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Curtelin D, Morales-Alamo D, Torres-Peralta R, Rasmussen P, Martin-Rincon M, Perez-Valera M, Siebenmann C, Pérez-Suárez I, Cherouveim E, Sheel AW, Lundby C, Calbet JA. Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans. J Cereb Blood Flow Metab 2018; 38:136-150. [PMID: 28186430 PMCID: PMC5757439 DOI: 10.1177/0271678x17691986] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min-1, mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery.
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Affiliation(s)
- David Curtelin
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,2 Emergency Medicine Department, Insular Universitary Hospital of Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - David Morales-Alamo
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Rafael Torres-Peralta
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Peter Rasmussen
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Marcos Martin-Rincon
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Mario Perez-Valera
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Christoph Siebenmann
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Ismael Pérez-Suárez
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Evgenia Cherouveim
- 5 Department of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Athens, Greece
| | - A William Sheel
- 6 School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - Carsten Lundby
- 4 Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - José Al Calbet
- 1 Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.,3 Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
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Siebenmann C, Keiser S, Robach P, Lundby C. CORP: The assessment of total hemoglobin mass by carbon monoxide rebreathing. J Appl Physiol (1985) 2017; 123:645-654. [DOI: 10.1152/japplphysiol.00185.2017] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 06/14/2017] [Accepted: 06/26/2017] [Indexed: 11/22/2022] Open
Abstract
In this Cores of Reproducibility in Physiology (CORP) article, we present the theory and practical aspects of the carbon monoxide (CO) rebreathing method for the determination of total hemoglobin mass in humans. With CO rebreathing, a small quantity of CO is diluted in O2and rebreathed for a specified time period, during which most of the CO is absorbed and bound to circulating hemoglobin. The dilution principle then allows calculation of the total number of circulating hemoglobin molecules based on the number of absorbed CO molecules and the resulting changes in the fraction of carboxyhemoglobin in blood. Total hemoglobin mass is derived by multiplication with the molar weight of hemoglobin. CO rebreathing has been used for >100 yr and has undergone steady improvement so that today excellent values in terms of accuracy and precision can be achieved if the methodological precautions are carefully followed.
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Affiliation(s)
- Christoph Siebenmann
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Stefanie Keiser
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland; and
| | - Paul Robach
- National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Carsten Lundby
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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Siebenmann C, Keramidas ME, Rundqvist H, Mijwel S, Cowburn AS, Johnson RS, Eiken O. Cutaneous exposure to hypoxia does not affect skin perfusion in humans. Acta Physiol (Oxf) 2017; 220:361-369. [PMID: 27809413 DOI: 10.1111/apha.12825] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 09/09/2016] [Accepted: 10/28/2016] [Indexed: 11/28/2022]
Abstract
AIM Experiments have indicated that skin perfusion in mice is sensitive to reductions in environmental O2 availability. Specifically, a reduction in skin-surface PO2 attenuates transcutaneous O2 diffusion, and hence epidermal O2 supply. In response, epidermal HIF-1α expression increases and facilitates initial cutaneous vasoconstriction and subsequent nitric oxide-dependent vasodilation. Here, we investigated whether the same mechanism exists in humans. METHODS In a first experiment, eight males rested twice for 8 h in a hypobaric chamber. Once, barometric pressure was reduced by 50%, while systemic oxygenation was preserved by O2 -enriched (42%) breathing gas (HypoxiaSkin ), and once barometric pressure and inspired O2 fraction were normal (Control1 ). In a second experiment, nine males rested for 8 h with both forearms wrapped in plastic bags. O2 was expelled from one bag by nitrogen flushing (AnoxiaSkin ), whereas the other bag was flushed with air (Control2 ). In both experiments, skin blood flux was assessed by laser Doppler on the dorsal forearm, and HIF-1α expression was determined by immunohistochemical staining in forearm skin biopsies. RESULTS Skin blood flux during HypoxiaSkin and AnoxiaSkin remained similar to the corresponding Control trial (P = 0.67 and P = 0.81). Immunohistochemically stained epidermal HIF-1α was detected on 8.2 ± 6.1 and 5.3 ± 5.7% of the analysed area during HypoxiaSkin and Control1 (P = 0.30) and on 2.3 ± 1.8 and 2.4 ± 1.8% during AnoxiaSkin and Control2 (P = 0.90) respectively. CONCLUSION Reductions in skin-surface PO2 do not affect skin perfusion in humans. The unchanged epidermal HIF-1α expression suggests that epidermal O2 homoeostasis was not disturbed by HypoxiaSkin /AnoxiaSkin , potentially due to compensatory increases in arterial O2 extraction.
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Affiliation(s)
- C. Siebenmann
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Stockholm Sweden
| | - M. E. Keramidas
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Stockholm Sweden
| | - H. Rundqvist
- Department of Cell and Molecular Biology; Karolinska Institutet; Stockholm Sweden
| | - S. Mijwel
- Department of Physiology and Pharmacology; Karolinska Institutet; Stockholm Sweden
| | - A. S. Cowburn
- Departments of Physiology, Development and Neuroscience and Medicine; University of Cambridge; Cambridge UK
| | - R. S. Johnson
- Department of Cell and Molecular Biology; Karolinska Institutet; Stockholm Sweden
- Departments of Physiology, Development and Neuroscience and Medicine; University of Cambridge; Cambridge UK
| | - O. Eiken
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Stockholm Sweden
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Siebenmann C, Robach P, Lundby C. Regulation of blood volume in lowlanders exposed to high altitude. J Appl Physiol (1985) 2017; 123:957-966. [PMID: 28572493 DOI: 10.1152/japplphysiol.00118.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 05/18/2017] [Accepted: 05/31/2017] [Indexed: 12/21/2022] Open
Abstract
Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O2 content ([Formula: see text]). As HA exposure extends, this reduction in [Formula: see text] is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a reduction in circulating blood volume is common at HA. Although the regulation of hematological responses to HA has been investigated for decades, it remains incompletely understood. This is not only related to the large number of mechanisms that could be involved and the complexity of their interplay but also to the difficulty of conducting comprehensive experiments in the often secluded HA environment. In this review, we present our understanding of the kinetics, the mechanisms and the physiological relevance of the HA-induced reduction in PV and expansion in RCV.
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Affiliation(s)
- Christoph Siebenmann
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
| | - Paul Robach
- National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Carsten Lundby
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
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Niemann MJ, Sørensen H, Siebenmann C, Lundby C, Secher NH. Carbon monoxide reduces near-infrared spectroscopy determined ‘total’ hemoglobin: a human volunteer study. Scandinavian Journal of Clinical and Laboratory Investigation 2017; 77:259-262. [DOI: 10.1080/00365513.2017.1299209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Keiser S, Meinild-Lundby AK, Steiner T, Trösch S, Rauber S, Krafft A, Burkhardt T, Hilty MP, Siebenmann C, Wehrlin JP, Lundby C. Detection of blood volumes and haemoglobin mass by means of CO re-breathing and indocyanine green and sodium fluorescein injections. Scand J Clin Lab Invest 2017; 77:164-174. [PMID: 28276723 DOI: 10.1080/00365513.2016.1271908] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The main aim of the present study was to quantify the magnitude of differences introduced when estimating a given blood volume compartment (e.g. plasma volume) through the direct determination of another compartment (e.g. red cell volume) by multiplication of venous haematocrit and/or haemoglobin concentration. However, since whole body haematocrit is higher than venous haematocrit such an approach might comprise certain errors. To test this experimentally, four different methods for detecting blood volumes and haemoglobin mass (Hbmass) were compared, namely the carbon monoxide (CO) re-breathing (for Hbmass), the indocyanine green (ICG; for plasma volume [PV]) and the sodium fluorescein (SoF; for red blood cell volume [RBCV]) methods. No difference between ICG and CO re-breathing derived PV could be established when a whole body/venous haematocrit correction factor of 0.91 was applied (p = 0.11, r = 0.43, mean difference -340 ± 612 mL). In contrast, when comparing RBCV derived by the CO re-breathing and the SoF method, the SoF method revealed lower RBCV values as compared to the CO re-breathing method (p < 0.05, r = 0.95, mean difference -728 ± 184 mL). However, compared to the ICG and the SoF methods, the typical error (%TE) and hence reliability of the CO re-breathing method was lower for all measured parameters. Therefore, estimating blood volume compartments by the direct assessment of another compartment can be considered a suitable approach. The CO re-breathing method proved accurate in determining the induced phlebotomy and is at the same time judged easier to perform than any of the other methods.
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Affiliation(s)
- Stefanie Keiser
- a Zurich Center for Integrative Human Physiology , Institute of Physiology, University of Zurich , Zurich , Switzerland
| | - Anne-Kristine Meinild-Lundby
- a Zurich Center for Integrative Human Physiology , Institute of Physiology, University of Zurich , Zurich , Switzerland
| | - Thomas Steiner
- b Swiss Federal Institute of Sports , Magglingen , Switzerland
| | - Severin Trösch
- b Swiss Federal Institute of Sports , Magglingen , Switzerland
| | - Sven Rauber
- a Zurich Center for Integrative Human Physiology , Institute of Physiology, University of Zurich , Zurich , Switzerland
| | - Alexander Krafft
- c Foeto-Maternal Haematology Group, Department of Obstetrics , University Hospital of Zurich , Zurich , Switzerland
| | - Tilo Burkhardt
- c Foeto-Maternal Haematology Group, Department of Obstetrics , University Hospital of Zurich , Zurich , Switzerland
| | | | - Christoph Siebenmann
- e Department of Environmental Physiology, School of Technology and Health , Royal Institute of Technology , Solna , Sweden
| | | | - Carsten Lundby
- a Zurich Center for Integrative Human Physiology , Institute of Physiology, University of Zurich , Zurich , Switzerland
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Siebenmann C, Rasmussen P, Hug M, Keiser S, Flück D, Fisher JP, Hilty MP, Maggiorini M, Lundby C. Parasympathetic withdrawal increases heart rate after 2 weeks at 3454 m altitude. J Physiol 2017; 595:1619-1626. [PMID: 27966225 DOI: 10.1113/jp273726] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 11/21/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Heart rate is increased in chronic hypoxia and we tested whether this is the result of increased sympathetic nervous activity, reduced parasympathetic nervous activity, or a non-autonomic mechanism. In seven lowlanders, heart rate was measured at sea level and after 2 weeks at high altitude after individual and combined pharmacological inhibition of sympathetic and/or parasympathetic control of the heart. Inhibition of parasympathetic control of the heart alone or in combination with inhibition of sympathetic control abolished the high altitude-induced increase in heart rate. Inhibition of sympathetic control of the heart alone did not prevent the high altitude-induced increase in heart rate. These results indicate that a reduced parasympathetic nervous activity is the main mechanism underlying the elevated heart rate in chronic hypoxia. ABSTRACT Chronic hypoxia increases resting heart rate (HR), but the underlying mechanism remains incompletely understood. We investigated the relative contributions of the sympathetic and parasympathetic nervous systems, along with potential non-autonomic mechanisms, by individual and combined pharmacological inhibition of muscarinic and/or β-adrenergic receptors. In seven healthy lowlanders, resting HR was determined at sea level (SL) and after 15-18 days of exposure to 3454 m high altitude (HA) without drug intervention (control, CONT) as well as after intravenous administration of either propranolol (PROP), or glycopyrrolate (GLYC), or PROP and GLYC in combination (PROP+GLYC). Circulating noradrenaline concentration increased from 0.9 ± 0.4 nmol l-1 at SL to 2.7 ± 1.5 nmol l-1 at HA (P = 0.03). The effect of HA on HR depended on the type of autonomic inhibition (P = 0.006). Specifically, HR was increased at HA from 64 ± 10 to 74 ± 12 beats min-1 during the CONT treatment (P = 0.007) and from 52 ± 4 to 59 ± 5 beats min-1 during the PROP treatment (P < 0.001). In contrast, HR was similar between SL and HA during the GLYC treatment (110 ± 7 and 112 ± 5 beats min-1 , P = 0.28) and PROP+GLYC treatment (83 ± 5 and 85 ± 5 beats min-1 , P = 0.25). Our results identify a reduction in cardiac parasympathetic activity as the primary mechanism underlying the elevated HR associated with 2 weeks of exposure to hypoxia. Unexpectedly, the sympathoactivation at HA that was evidenced by increased circulating noradrenaline concentration had little effect on HR, potentially reflecting down-regulation of cardiac β-adrenergic receptor function in chronic hypoxia. These effects of chronic hypoxia on autonomic control of the heart may concern not only HA dwellers, but also patients with disorders that are associated with hypoxaemia.
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Affiliation(s)
- Christoph Siebenmann
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland.,Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - Peter Rasmussen
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland.,H. Lundbeck A/S, Valby, Denmark
| | - Mike Hug
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Stefanie Keiser
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Daniela Flück
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - James P Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Matthias P Hilty
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - Marco Maggiorini
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - Carsten Lundby
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
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Sundblad P, Frånberg O, Siebenmann C, Gennser M. Measuring Uptake and Elimination of Nitrogen in Humans at Different Ambient Pressures. Aerosp Med Hum Perform 2016; 87:1045-1050. [PMID: 28323592 DOI: 10.3357/amhp.4680.2016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND To measure nitrogen (N2) wash-out and uptake requires elaborate set-ups, especially when doing the measurements at increased or decreased ambient pressure. Here we present a transportable device for quantifying N2 turnover in humans which can be used at different ambient pressures. METHODS A modified close-circuit electronic rebreather was used to assess N2 turnover. Changes in N2 volume within the rebreathing circuit, reflecting N2 uptake or washout, were derived from the continuously monitored total system volume and the calculated volumes of oxygen and water vapor. The calculation of continuous N2 volume curves was performed off-line using dedicated computer software. RESULTS Four subjects participated in the proof-of-concept tests. At steady state, the drift in calculated N2 volume in the rebreathing circuit over a 1-h duration was minimal. Three of the subjects participated in additional N2 steady-state measurements where 1019 mL (BTPD) of N2 was injected into the rebreathing circuit over 20 min and the measured volume increase was 1006 ± 32 mL. Lastly, N2 elimination was assessed during decompression to 0.5 atm and while breathing hyperoxic gas. N2 uptake was measured during compression to 1.8 atm. The elimination and uptake curves were deemed to be realistic. DISCUSSION A method for assessing N2 turnover in humans has been developed and a first evaluation has been performed. It is easy to work with operationally and can be used at different ambient pressures. More research is needed in order to further validate it as a method for assessing N2 turnover in humans.Sundblad P, Frånberg O, Siebenmann C, Gennser M. Measuring uptake and elimination of nitrogen in humans at different ambient pressures. Aerosp Med Hum Perform. 2016; 87(12):1045-1050.
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Affiliation(s)
- Patrik Sundblad
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, School of Technology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
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Siebenmann C, Rasmussen P. Does cerebral hypoxia facilitate central fatigue? Exp Physiol 2016; 101:1173-1177. [DOI: 10.1113/ep085640] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 02/16/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Christoph Siebenmann
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Solna Sweden
| | - Peter Rasmussen
- H. Lundbeck A/S; Valby; Denmark
- Department of Neuroscience and Pharmacology; University of Copenhagen; Denmark
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Affiliation(s)
- Christoph Siebenmann
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Solna Sweden
| | - Carsten Lundby
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
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Siebenmann C, Cathomen A, Hug M, Keiser S, Lundby AK, Hilty MP, Goetze JP, Rasmussen P, Lundby C. Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454-m altitude. J Appl Physiol (1985) 2015; 119:1194-201. [DOI: 10.1152/japplphysiol.01121.2014] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 02/25/2015] [Indexed: 01/14/2023] Open
Abstract
High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements, and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV was estimated by carbon monoxide rebreathing at SL, on every 4th day at HA, and 1 and 2 wk upon return to SL. Four weeks at HA increased Hbmass by 5.26% (range 2.5-11.1%; P < 0.001). The individual Hbmass increases commenced with up to 12 days of delay and reached a maximal rate of 4.04 ± 1.02 g/day after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20–24 days. Upon return to SL Hbmass decayed by −2.46 ± 2.3 g/day, reaching values similar to baseline after 2 wk. PV, aldosterone concentration, and renin activity were reduced at HA ( P < 0.001) while the total circulating protein mass remained unaffected. In summary, the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ∼3 wk. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data support that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - A. Cathomen
- Institute of Human Movement Sciences and Sport, ETH Zürich, Zürich, Switzerland
| | - M. Hug
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - S. Keiser
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - A. K. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - M. P. Hilty
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - J. P. Goetze
- Department of Clinical Biochemistry, Copenhagen, and Aarhus University, Aarhus, Denmark
| | | | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
- Food and Nutrition and Sport Science, Gothenburg University, Gothenburg, Sweden
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Jacobs RA, Lundby AKM, Fenk S, Gehrig S, Siebenmann C, Flück D, Kirk N, Hilty MP, Lundby C. Twenty-eight days of exposure to 3454 m increases mitochondrial volume density in human skeletal muscle. J Physiol 2015; 594:1151-66. [PMID: 26339730 DOI: 10.1113/jp271118] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/28/2015] [Indexed: 12/11/2022] Open
Abstract
The role of hypoxia on skeletal muscle mitochondria is controversial. Studies superimposing exercise training on hypoxic exposure demonstrate an increase in skeletal muscle mitochondrial volume density (Mito(VD)) over equivalent normoxic training. In contrast, reductions in both skeletal muscle mass and Mito(VD) have been reported following mountaineering expeditions. These observations may, however, be confounded by negative energy balance, which may obscure the results. Accordingly we sought to examine the effects of high altitude hypoxic exposure on mitochondrial characteristics, with emphasis on Mito(VD), while minimizing changes in energy balance. For this purpose, skeletal muscle biopsies were obtained from nine lowlanders at sea level (Pre) and following 7 and 28 days of exposure to 3454 m. Maximal ergometer power output, whole body weight and composition, leg lean mass and skeletal muscle fibre area all remained unchanged following the altitude exposure. Transmission electron microscopy determined that intermyofibrillar (IMF) Mito(VD) was augmented (P = 0.028) by 11.5 ± 9.2% from Pre (5.05 ± 0.9%) to 28 Days (5.61 ± 0.04%). In contrast, there was no change in subsarcolemmal (SS) Mito(VD). As a result, total Mito(VD) (IMF + SS) was increased (P = 0.031) from 6.20 ± 1.5% at Pre to 6.62 ± 1.4% at 28 Days (7.8 ± 9.3%). At the same time no changes in mass-specific respiratory capacities, mitochondrial protein or antioxidant content were found. This study demonstrates that skeletal muscle Mito(VD) may increase with 28 days acclimation to 3454 m.
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Affiliation(s)
- Robert A Jacobs
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland.,Health and Physical Education, School of Teaching and Learning, Western Carolina University, Cullowhee, NC, USA.,Physical Therapy Department, Western Carolina University, Cullowhee, NC, USA
| | | | - Simone Fenk
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland
| | - Saskia Gehrig
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland
| | - Christoph Siebenmann
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland.,Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - Daniela Flück
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland
| | - Niels Kirk
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland
| | | | - Carsten Lundby
- Zürich Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Switzerland
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Calbet JAL, Losa-Reyna J, Torres-Peralta R, Rasmussen P, Ponce-González JG, Sheel AW, de la Calle-Herrero J, Guadalupe-Grau A, Morales-Alamo D, Fuentes T, Rodríguez-García L, Siebenmann C, Boushel R, Lundby C. Limitations to oxygen transport and utilization during sprint exercise in humans: evidence for a functional reserve in muscle O2 diffusing capacity. J Physiol 2015; 593:4649-64. [PMID: 26258623 DOI: 10.1113/jp270408] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 08/05/2015] [Indexed: 12/14/2022] Open
Abstract
To determine the contribution of convective and diffusive limitations to V̇(O2peak) during exercise in humans, oxygen transport and haemodynamics were measured in 11 men (22 ± 2 years) during incremental (IE) and 30 s all-out cycling sprints (Wingate test, WgT), in normoxia (Nx, P(IO2): 143 mmHg) and hypoxia (Hyp, P(IO2): 73 mmHg). Carboxyhaemoglobin (COHb) was increased to 6-7% before both WgTs to left-shift the oxyhaemoglobin dissociation curve. Leg V̇(O2) was measured by the Fick method and leg blood flow (BF) with thermodilution, and muscle O2 diffusing capacity (D(MO2)) was calculated. In the WgT mean power output, leg BF, leg O2 delivery and leg V̇(O2) were 7, 5, 28 and 23% lower in Hyp than Nx (P < 0.05); however, peak WgT D(MO2) was higher in Hyp (51.5 ± 9.7) than Nx (20.5 ± 3.0 ml min(-1) mmHg(-1), P < 0.05). Despite a similar P(aO2) (33.3 ± 2.4 and 34.1 ± 3.3 mmHg), mean capillary P(O2) (16.7 ± 1.2 and 17.1 ± 1.6 mmHg), and peak perfusion during IE and WgT in Hyp, D(MO2) and leg V̇(O2) were 12 and 14% higher, respectively, during WgT than IE in Hyp (both P < 0.05). D(MO2) was insensitive to COHb (COHb: 0.7 vs. 7%, in IE Hyp and WgT Hyp). At exhaustion, the Y equilibration index was well above 1.0 in both conditions, reflecting greater convective than diffusive limitation to the O2 transfer in both Nx and Hyp. In conclusion, muscle V̇(O2) during sprint exercise is not limited by O2 delivery, O2 offloading from haemoglobin or structure-dependent diffusion constraints in the skeletal muscle. These findings reveal a remarkable functional reserve in muscle O2 diffusing capacity.
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Affiliation(s)
- José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - José Losa-Reyna
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Rafael Torres-Peralta
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Peter Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Jesús Gustavo Ponce-González
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jaime de la Calle-Herrero
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Amelia Guadalupe-Grau
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - David Morales-Alamo
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Teresa Fuentes
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Lorena Rodríguez-García
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Christoph Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Robert Boushel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.,Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Carsten Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
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Flück D, Siebenmann C, Keiser S, Cathomen A, Lundby C. Cerebrovascular reactivity is increased with acclimatization to 3,454 m altitude. J Cereb Blood Flow Metab 2015; 35:1323-30. [PMID: 25806704 PMCID: PMC4528007 DOI: 10.1038/jcbfm.2015.51] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 02/11/2015] [Accepted: 03/02/2015] [Indexed: 12/27/2022]
Abstract
Controversy exists regarding the effect of high-altitude exposure on cerebrovascular CO2 reactivity (CVR). Confounding factors in previous studies include the use of different experimental approaches, ascent profiles, duration and severity of exposure and plausibly environmental factors associated with altitude exposure. One aim of the present study was to determine CVR throughout acclimatization to high altitude when controlling for these. Middle cerebral artery mean velocity (MCAv mean) CVR was assessed during hyperventilation (hypocapnia) and CO2 administration (hypercapnia) with background normoxia (sea level (SL)) and hypoxia (3,454 m) in nine healthy volunteers (26 ± 4 years (mean ± s.d.)) at SL, and after 30 minutes (HA0), 3 (HA3) and 22 (HA22) days of high-altitude (3,454 m) exposure. At altitude, ventilation was increased whereas MCAv mean was not altered. Hypercapnic CVR was decreased at HA0 (1.16% ± 0.16%/mm Hg, mean ± s.e.m.), whereas both hyper- and hypocapnic CVR were increased at HA3 (3.13% ± 0.18% and 2.96% ± 0.10%/mm Hg) and HA22 (3.32% ± 0.12% and 3.24% ± 0.14%/mm Hg) compared with SL (1.98% ± 0.22% and 2.38% ± 0.10%/mm Hg; P < 0.01) regardless of background oxygenation. Cerebrovascular conductance (MCAv mean/mean arterial pressure) CVR was determined to account for blood pressure changes and revealed an attenuated response. Collectively our results show that hypocapnic and hypercapnic CVR are both elevated with acclimatization to high altitude.
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Affiliation(s)
- Daniela Flück
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland
| | | | - Stefanie Keiser
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland
| | - Adrian Cathomen
- Institute of Human Movement Sciences, ETH Zurich, Zurich, Switzerland
| | - Carsten Lundby
- 1] Zurich Center for Integrative Human Physiology (ZIHP), Zurich, Switzerland [2] Institute of Physiology, ZIHP, University of Zurich, Zurich, Switzerland [3] Department of Food and Nutrition and Sport Science, Gothenburg University, Gothenburg, Sweden
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Siebenmann C, Rasmussen P, Sørensen H, Bonne TC, Zaar M, Aachmann-Andersen NJ, Nordsborg NB, Secher NH, Lundby C. Hypoxia increases exercise heart rate despite combined inhibition of β-adrenergic and muscarinic receptors. Am J Physiol Heart Circ Physiol 2015; 308:H1540-6. [DOI: 10.1152/ajpheart.00861.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/15/2015] [Indexed: 11/22/2022]
Abstract
Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of β-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions ( P < 0.001) but was always higher at a given workload in hypoxia than normoxia ( P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 ± 13.8 beats/min during Cont and similar (17.2 ± 7.7 beats/min, P = 0.95) during Prop but smaller ( P < 0.001) during Glyc and Prop + Glyc (9.8 ± 9.6 and 8.1 ± 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia ( P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 ± 1.9, 1.7 ± 1.8, and 2.3 ± 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 ± 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than β-adrenergic transmission. A potential candidate is α-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined β-adrenergic and muscarinic receptor inhibition.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - P. Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - H. Sørensen
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - T. C. Bonne
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - M. Zaar
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - N. B. Nordsborg
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - N. H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
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Sørensen H, Ogoh S, Sato K, Siebenmann C, Rasmussen P, Lundby C, Secher N. Cardiac Mechanoreceptor Activation in Humans: Evaluation by Phenylephrine and Norepinephrine. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.643.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Henrik Sørensen
- Copenhagen Muscle Research Centre University of CopenhagenDenmark
| | - Shigehiko Ogoh
- Department of Biomedical EngineeringToyo UniversityJapan
| | - Kohei Sato
- Department of Biomedical EngineeringToyo UniversityJapan
| | | | - Peter Rasmussen
- Copenhagen Muscle Research Centre University of CopenhagenDenmark
| | | | - Niels Secher
- Copenhagen Muscle Research Centre University of CopenhagenDenmark
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Abstract
INTRODUCTION Altitude acclimatization is associated with a rapid increase in hematocrit. The time course and the contribution of the red cell volume expansion are not clear. The purpose of the present meta-analysis was to explore how much altitude exposure is required to induce polycythemia in healthy lowlanders. METHODS A systematic review was performed of 66 published articles (including 447 volunteers) identified through literature search. We performed a mixed-model random-effects meta-analysis and a Monte Carlo simulation on the extracted data. RESULTS The following results were obtained in this study: 1) the red cell volume expansion for a given duration of exposure is dependent on altitude (P < 0.0001), that is, that the increase in red cell volume was accelerated at higher altitudes; and 2) the extent of the erythropoietic response depends on the initial red cell volume (P < 0.0001). It seems that exposure time must exceed 2 wk at an altitude of more than 4000 m to exert a statistically significant effect. At lower altitudes, longer exposure times are needed with altitudes lower than 3000 m not yielding an increase within 4 wk. CONCLUSIONS Red cell volume response to hypoxia is generally slow, although it accelerates with increasing altitude. This, in combination with a dependency on initial red cell volume, suggests that, for example, athletes may need to spend more time at altitude to see an effect on red cell volume than commonly recommended.
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Affiliation(s)
- Peter Rasmussen
- Zurich Center of Integrative Human Physiology, Institute of Physiology, Zurich, Switzerland.
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Siebenmann C, Rasmussen P, Sørensen H, Zaar M, Hvidtfeldt M, Pichon A, Secher NH, Lundby C. Cardiac output during exercise: A comparison of four methods. Scand J Med Sci Sports 2014; 25:e20-7. [DOI: 10.1111/sms.12201] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2014] [Indexed: 12/21/2022]
Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - P. Rasmussen
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - H. Sørensen
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Zaar
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Hvidtfeldt
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - A. Pichon
- Laboratoire Réponses Cellulaires et Fonctionnelles à l'Hypoxie; Université Paris 13; Bobigny France
| | - N. H. Secher
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - C. Lundby
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
- Food & Nutrition & Sport Science; Gothenburg University; Gothenburg Sweden
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