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Sigg AA, Zivkovic V, Bartussek J, Schuepbach RA, Ince C, Hilty MP. The physiological basis for individualized oxygenation targets in critically ill patients with circulatory shock. Intensive Care Med Exp 2024; 12:72. [PMID: 39174691 PMCID: PMC11341514 DOI: 10.1186/s40635-024-00651-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 07/21/2024] [Indexed: 08/24/2024] Open
Abstract
BACKGROUND Circulatory shock, defined as decreased tissue perfusion, leading to inadequate oxygen delivery to meet cellular metabolic demands, remains a common condition with high morbidity and mortality. Rapid restitution and restoration of adequate tissue perfusion are the main treatment goals. To achieve this, current hemodynamic strategies focus on adjusting global physiological variables such as cardiac output (CO), hemoglobin (Hb) concentration, and arterial hemoglobin oxygen saturation (SaO2). However, it remains a challenge to identify optimal targets for these global variables that best support microcirculatory function. Weighting up the risks and benefits is especially difficult for choosing the amount of oxygen supplementation in critically ill patients. This review assesses the physiological basis for oxygen delivery to the tissue and provides an overview of the relevant literature to emphasize the importance of considering risks and benefits and support decision making at the bedside. PHYSIOLOGICAL PREMISES Oxygen must reach the tissue to enable oxidative phosphorylation. The human body timely detects hypoxia via different mechanisms aiming to maintain adequate tissue oxygenation. In contrast to the pulmonary circulation, where the main response to hypoxia is arteriolar vasoconstriction, the regulatory mechanisms of the systemic circulation aim to optimize oxygen availability in the tissues. This is achieved by increasing the capillary density in the microcirculation and the capillary hematocrit thereby increasing the capacity of oxygen diffusion from the red blood cells to the tissue. Hyperoxia, on the other hand, is associated with oxygen radical production, promoting cell death. CURRENT STATE OF RESEARCH Clinical trials in critically ill patients have primarily focused on comparing macrocirculatory endpoints and outcomes based on stroke volume and oxygenation targets. Some earlier studies have indicated potential benefits of conservative oxygenation. Recent trials show contradictory results regarding mortality, organ dysfunction, and ventilatory-free days. Empirical studies comparing various targets for SaO2, or partial pressure of oxygen indicate a U-shaped curve balancing positive and negative effects of oxygen supplementation. CONCLUSION AND FUTURE DIRECTIONS To optimize risk-benefit ratio of resuscitation measures in critically ill patients with circulatory shock in addition to individual targets for CO and Hb concentration, a primary aim should be to restore tissue perfusion and avoid hyperoxia. In the future, an individualized approach with microcirculatory targets will become increasingly relevant. Further studies are needed to define optimal targets.
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Affiliation(s)
- Anne-Aylin Sigg
- Institute of Intensive Care Medicine, University Hospital of Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.
| | - Vanja Zivkovic
- Institute of Intensive Care Medicine, University Hospital of Zurich, Raemistrasse 100, 8091, Zurich, Switzerland
| | - Jan Bartussek
- Institute of Intensive Care Medicine, University Hospital of Zurich, Raemistrasse 100, 8091, Zurich, Switzerland
| | - Reto A Schuepbach
- Institute of Intensive Care Medicine, University Hospital of Zurich, Raemistrasse 100, 8091, Zurich, Switzerland
| | - Can Ince
- Department of Intensive Care, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
| | - Matthias P Hilty
- Institute of Intensive Care Medicine, University Hospital of Zurich, Raemistrasse 100, 8091, Zurich, Switzerland
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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. EUROPEAN HEART JOURNAL. CARDIOVASCULAR PHARMACOTHERAPY 2024; 10:316-328. [PMID: 38216517 DOI: 10.1093/ehjcvp/pvae004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/13/2023] [Accepted: 01/11/2024] [Indexed: 01/14/2024]
Abstract
BACKGROUND An increasing number of hypertensive persons travel to high altitude (HA) while using antihypertensive medications such as beta-blockers. 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, beta-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, Ppa was invasively measured without medication, with PROP and PROP + GLYC, both at sea level (SL, 488 m) and after a 3-week sojourn at 3454 m altitude (HA). Bilateral thigh-cuff release manoeuvres 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 ± 1 mmHg and from 69 ± 8 to 108 ± 11 dyn 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 beta-adrenergic blockade increases, and muscarinic blockade decreases PVR, whereas both increase pulmonary artery elastance. Future studies may confirm potential implications from the finding that beta-adrenergic blockade exaggerates HPV for the management of mountaineers using beta-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, ZH 8091, Switzerland
| | - Christoph Siebenmann
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, ZH 8091, Switzerland
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, TA 39100, Italy
| | - Peter Rasmussen
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, ZH 8091, Switzerland
| | - Stefanie Keiser
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, ZH 8091, Switzerland
| | - Andrea Müller
- Institute of Intensive Care Medicine, University Hospital of Zurich, ZH 8091, Switzerland
| | - Carsten Lundby
- Center for Integrative Human Physiology (ZIHP), Institute of Physiology, University of Zurich, ZH 8091, Switzerland
- Department of Health and Exercise Physiology, Inland Norway University of Applied Sciences, Lillehammer, OP 2624, Norway
| | - Marco Maggiorini
- Institute of Intensive Care Medicine, University Hospital of Zurich, ZH 8091, Switzerland
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Wang NN, Yu SF, Dang P, Su R, Li H, Ma HL, Liu M, Zhang DL. The neuroimmune pathway of high-altitude adaptation: influence of erythrocytes on attention networks through inflammation and the autonomic nervous system. Front Neurosci 2024; 18:1373136. [PMID: 38638694 PMCID: PMC11024340 DOI: 10.3389/fnins.2024.1373136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/19/2024] [Indexed: 04/20/2024] Open
Abstract
Introduction Many studies have shown that the functional adaptation of immigrants to high-altitude is closely related to oxygen transport, inflammatory response and autonomic nervous system. However, it remains unclear how human attention changes in response to hypoxia-induced neurophysiological activity during high-altitude exposure. Methods In the present study, we analyzed the relationship between hypoxic-induced neurophysiological responses and attention networks in 116 immigrants (3,680 m) using an attention network test to simultaneously record electroencephalogram and electrocardiogram in combination with specific routine blood markers. Results Our analysis revealed that red blood cells exert an indirect influence on the three attention networks, mediated through inflammatory processes and heart rate variability. Discussion The present study provides experimental evidence for the role of a neuroimmune pathway in determining human attention performance at high- altitude. Our findings have implications for understanding the complex interactions between physiological and neurocognitive processes in immigrants adapting to hypoxic environments.
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Affiliation(s)
- Nian-Nian Wang
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
- Key Laboratory of Brain, Cognition, and Education Sciences, Ministry of Education, Guangzhou, China
- School of Psychology, Center for Studies of Psychological Application, and Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, China
| | - Si-Fang Yu
- Key Laboratory of Brain, Cognition, and Education Sciences, Ministry of Education, Guangzhou, China
- School of Psychology, Center for Studies of Psychological Application, and Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, China
| | - Peng Dang
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
| | - Rui Su
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
| | - Hao Li
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
| | - Hai-Lin Ma
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
| | - Ming Liu
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
- Key Laboratory of Brain, Cognition, and Education Sciences, Ministry of Education, Guangzhou, China
- School of Psychology, Center for Studies of Psychological Application, and Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, China
| | - De-Long Zhang
- Key Laboratory of High Altitudes Brain Science and Environmental Acclimation, Tibet University, Lhasa, China
- Key Laboratory of Brain, Cognition, and Education Sciences, Ministry of Education, Guangzhou, China
- School of Psychology, Center for Studies of Psychological Application, and Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, China
- School of Educational Sciences, Kashi University, Kashi, China
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Rathi V, Sagi SSK, Yadav AK, Kumar M, Varshney R. Quercetin prophylaxis protects the kidneys by modulating the renin-angiotensin-aldosterone axis under acute hypobaric hypoxic stress. Sci Rep 2024; 14:7617. [PMID: 38556603 PMCID: PMC10982295 DOI: 10.1038/s41598-024-58134-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 03/26/2024] [Indexed: 04/02/2024] Open
Abstract
The study presented here aims at assessing the effects of hypobaric hypoxia on RAAS pathway and its components along with mitigation of anomalies with quercetin prophylaxis. One hour prior to hypobaric hypoxia exposure, male SD rats were orally supplemented with quercetin (50 mg/kg BW) and acetazolamide (50 mg/kg BW) and exposed them to 25,000 ft. (7,620 m) in a simulated environmental chamber for 12 h at 25 ± 2 °C. Different biochemical parameters like renin activity, aldosterone, angiotensin I, ACE 2 were determined in plasma. As a conventional response to low oxygen conditions, oxidative stress parameters (ROS and MDA) were elevated along with suppressed antioxidant system (GPx and catalase) in plasma of rats. Quercetin prophylaxis significantly down regulated the hypoxia induced oxidative stress by reducing plasma ROS & MDA levels with efficient enhancement of antioxidants (GPx and Catalase). Further, hypoxia mediated regulation of renin and ACE 2 proves the outstanding efficacy of quercetin in repudiating altercations in RAAS cascade due to hypobaric hypoxia. Furthermore, differential protein expression of HIF-1α, NFκB, IL-18 and endothelin-1 analyzed by western blotting approves the biochemical outcomes and showed that quercetin significantly aids in the reduction of inflammation under hypoxia. Studies conducted with Surface Plasmon Resonance demonstrated a binding among quercetin and ACE 2 that indicates that this flavonoid might regulate RAAS pathway via ACE 2. Henceforth, the study promotes the prophylaxis of quercetin for the better adaptability under hypobaric hypoxic conditions via modulating the RAAS pathway.
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Affiliation(s)
- Vaishnavi Rathi
- Defence Institute of Physiology and Allied Sciences, DRDO, Lucknow Road, Timarpur, New Delhi, 110054, India
| | - Sarada S K Sagi
- Defence Institute of Physiology and Allied Sciences, DRDO, Lucknow Road, Timarpur, New Delhi, 110054, India.
| | - Amit Kumar Yadav
- Department of Biophysics, All India Institute of Medical Science, Delhi, India
| | - Manoj Kumar
- Department of Biophysics, All India Institute of Medical Science, Delhi, India
| | - Rajeev Varshney
- Defence Institute of Physiology and Allied Sciences, DRDO, Lucknow Road, Timarpur, New Delhi, 110054, India
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Raberin A, Burtscher J, Citherlet T, Manferdelli G, Krumm B, Bourdillon N, Antero J, Rasica L, Malatesta D, Brocherie F, Burtscher M, Millet GP. Women at Altitude: Sex-Related Physiological Responses to Exercise in Hypoxia. Sports Med 2024; 54:271-287. [PMID: 37902936 PMCID: PMC10933174 DOI: 10.1007/s40279-023-01954-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2023] [Indexed: 11/01/2023]
Abstract
Sex differences in physiological responses to various stressors, including exercise, have been well documented. However, the specific impact of these differences on exposure to hypoxia, both at rest and during exercise, has remained underexplored. Many studies on the physiological responses to hypoxia have either excluded women or included only a limited number without analyzing sex-related differences. To address this gap, this comprehensive review conducted an extensive literature search to examine changes in physiological functions related to oxygen transport and consumption in hypoxic conditions. The review encompasses various aspects, including ventilatory responses, cardiovascular adjustments, hematological alterations, muscle metabolism shifts, and autonomic function modifications. Furthermore, it delves into the influence of sex hormones, which evolve throughout life, encompassing considerations related to the menstrual cycle and menopause. Among these physiological functions, the ventilatory response to exercise emerges as one of the most sex-sensitive factors that may modify reactions to hypoxia. While no significant sex-based differences were observed in cardiac hemodynamic changes during hypoxia, there is evidence of greater vascular reactivity in women, particularly at rest or when combined with exercise. Consequently, a diffusive mechanism appears to be implicated in sex-related variations in responses to hypoxia. Despite well-established sex disparities in hematological parameters, both acute and chronic hematological responses to hypoxia do not seem to differ significantly between sexes. However, it is important to note that these responses are sensitive to fluctuations in sex hormones, and further investigation is needed to elucidate the impact of the menstrual cycle and menopause on physiological responses to hypoxia.
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Affiliation(s)
- Antoine Raberin
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Johannes Burtscher
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Tom Citherlet
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Giorgio Manferdelli
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Bastien Krumm
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Bourdillon
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Juliana Antero
- Institut de Recherche Bio-Médicale Et d'Épidémiologie du Sport (EA 7329), French Institute of Sport, Paris, France
| | - Letizia Rasica
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Davide Malatesta
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Franck Brocherie
- Laboratory Sport, Expertise and Performance (EA 7370), French Institute of Sport, Paris, France
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Grégoire P Millet
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
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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: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [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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Richalet J, Hermand E. Modeling the oxygen transport to the myocardium at maximal exercise at high altitude. Physiol Rep 2022; 10:e15262. [PMID: 35439356 PMCID: PMC9017981 DOI: 10.14814/phy2.15262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/22/2022] [Accepted: 03/23/2022] [Indexed: 06/14/2023] Open
Abstract
Exposure to high altitude induces a decrease in oxygen pressure and saturation in the arterial blood, which is aggravated by exercise. Heart rate (HR) at maximal exercise decreases when altitude increases in prolonged exposure to hypoxia. We developed a simple model of myocardial oxygenation in order to demonstrate that the observed blunting of maximal HR at high altitude is necessary for the maintenance of a normal myocardial oxygenation. Using data from the available scientific literature, we estimated the myocardial venous oxygen pressure and saturation at maximal exercise in two conditions: (1) with actual values of maximal HR (decreasing with altitude); (2) with sea-level values of maximal heart rate, whatever the altitude (no change in HR). We demonstrated that, in the absence of autoregulation of maximal HR, myocardial tissue oxygenation would be incompatible with life above 6200 m-7600 m, depending on the hypothesis concerning a possible increase in coronary reserve (increase in coronary blood flow at exercise). The decrease in maximal HR at high altitude could be explained by several biological mechanisms involving the autonomic nervous system and its receptors on myocytes. These experimental and clinical observations support the hypothesis that there exists an integrated system at the cellular level, which protects the myocardium from a hazardous disequilibrium between O2 supply and O2 consumption at high altitude.
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Affiliation(s)
- Jean‐Paul Richalet
- UMR INSERM U1272 Hypoxie & PoumonUniversité Sorbonne Paris NordBobignyFrance
| | - Eric Hermand
- Université Littoral Côte d’OpaleUniversité ArtoisUniversité Lille, CHU LilleULR 7369 ‐ URePSSS‐Unité de Recherche Pluridisciplinaire Sport Santé SociétéDunkerqueFrance
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Verratti V, Tonacci A, Bondi D, Chiavaroli A, Ferrante C, Brunetti L, Crisafulli A, Cerretelli P. Ethnic Differences on Cardiac Rhythms and Autonomic Nervous System Responses During a High-Altitude Trek: A Pilot Study Comparing Italian Trekkers to Nepalese Porters. Front Physiol 2021; 12:709451. [PMID: 34497537 PMCID: PMC8419438 DOI: 10.3389/fphys.2021.709451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/28/2021] [Indexed: 01/10/2023] Open
Abstract
Altitude hypoxia exposure results in increased sympathetic activity and heart rate due to several mechanisms. Recent studies have contested the validity of heart rate variability (HRV) analysis on sympathetic activity measurement. But the plethora of HRV metrics may provide meaningful insights, particularly if linked with cardiovascular and autonomic nervous system parameters. However, the population-specific nature of HRV and cardiorespiratory response to altitude hypoxia are still missing. Six Italian trekkers and six Nepalese porters completed 300 km of a Himalayan trek. The ECG analysis was conducted at baseline, and before (bBC) and after (aBC) the high-altitude (HA) circuit. Urine was collected before and after the expedition in Italians, for assessing catecholamines. Heart rate increased with altitude significantly (p < 0.001) in the Italian group; systolic (p = 0.030) and diastolic (p = 0.012) blood pressure, and mean arterial pressure (p = 0.004) increased with altitude. Instead, pulse pressure did not change, although the Nepalese group showed lower baseline values than the Italians. As expected, peripheral oxygen saturation decreased with altitude (p < 0.001), independently of the ethnic groups. Nepalese had a higher respiratory rate (p = 0.007), independent of altitude. The cardiac vagal index increased at altitude, from baseline to bBC (p = 0.008). Higuchi fractal dimension (HFD) showed higher basal values in the Nepalese group (p = 0.041), and a tendency for the highest values at bBC. Regarding the urinary catecholamine response, exposure to HA increased urinary levels, particularly of norepinephrine (p = 0.005, d = 1.623). Our findings suggest a better cardiovascular resilience of the Nepalese group when compared with Italians, which might be due to an intrinsic adaptation to HA, resulting from their job.
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Affiliation(s)
- Vittore Verratti
- Department of Psychological, Health and Territorial Sciences, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Alessandro Tonacci
- Institute of Clinical Physiology, National Research Council of Italy, Pisa, Italy
| | - Danilo Bondi
- Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Annalisa Chiavaroli
- Department of Pharmacy, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Claudio Ferrante
- Department of Pharmacy, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Luigi Brunetti
- Department of Pharmacy, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Antonio Crisafulli
- Department of Medical Science and Public Health, University of Cagliari, Cagliari, Italy
| | - Paolo Cerretelli
- Institute of Bioimaging and Molecular Physiology, National Research Council of Italy, Segrate, Italy
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Iturriaga R, Alcayaga J, Chapleau MW, Somers VK. Carotid body chemoreceptors: physiology, pathology, and implications for health and disease. Physiol Rev 2021; 101:1177-1235. [PMID: 33570461 PMCID: PMC8526340 DOI: 10.1152/physrev.00039.2019] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The carotid body (CB) is the main peripheral chemoreceptor for arterial respiratory gases O2 and CO2 and pH, eliciting reflex ventilatory, cardiovascular, and humoral responses to maintain homeostasis. This review examines the fundamental biology underlying CB chemoreceptor function, its contribution to integrated physiological responses, and its role in maintaining health and potentiating disease. Emphasis is placed on 1) transduction mechanisms in chemoreceptor (type I) cells, highlighting the role played by the hypoxic inhibition of O2-dependent K+ channels and mitochondrial oxidative metabolism, and their modification by intracellular molecules and other ion channels; 2) synaptic mechanisms linking type I cells and petrosal nerve terminals, focusing on the role played by the main proposed transmitters and modulatory gases, and the participation of glial cells in regulation of the chemosensory process; 3) integrated reflex responses to CB activation, emphasizing that the responses differ dramatically depending on the nature of the physiological, pathological, or environmental challenges, and the interactions of the chemoreceptor reflex with other reflexes in optimizing oxygen delivery to the tissues; and 4) the contribution of enhanced CB chemosensory discharge to autonomic and cardiorespiratory pathophysiology in obstructive sleep apnea, congestive heart failure, resistant hypertension, and metabolic diseases and how modulation of enhanced CB reactivity in disease conditions may attenuate pathophysiology.
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Affiliation(s)
- Rodrigo Iturriaga
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile, and Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Julio Alcayaga
- Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Mark W Chapleau
- Department of Internal Medicine, University of Iowa and Department of Veterans Affairs Medical Center, Iowa City, Iowa
| | - Virend K Somers
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
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Beltrán AR, Arce-Álvarez A, Ramirez-Campillo R, Vásquez-Muñoz M, von Igel M, Ramírez MA, Del Rio R, Andrade DC. Baroreflex Modulation During Acute High-Altitude Exposure in Rats. Front Physiol 2020; 11:1049. [PMID: 32973562 PMCID: PMC7472463 DOI: 10.3389/fphys.2020.01049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 07/30/2020] [Indexed: 12/25/2022] Open
Abstract
Baroreflex (BR) control is critically dependent of sympathetic and parasympathetic modulation. It has been documented that during acute hypobaric hypoxia there is a BR control impairment, however, the effect of a natural hypoxic environment on BR function is limited and controversial. Therefore, the aim of this study was to determine the effect of acute High-Altitude exposure on sympathetic/parasympathetic modulation of BR control in normal rats. Male Sprague Dawley rats were randomly allocated into Sea-Level (n = 7) and High-Altitude (n = 5) (3,270 m above sea level) groups. The BR control was studied using phenylephrine (Phe) and sodium nitroprusside (SNP) through sigmoidal analysis. The autonomic control of the heart was estimated using heart rate variability (HRV) analysis in frequency domain. Additionally, to determine the maximum sympathetic and parasympathetic activation of BR, spectral non-stationary method analysis, during Phe (0.05 μg/mL) and SNP administration (0.10 μg/mL) were used. Compared to Sea-Level condition, the High-Altitude group displayed parasympathetic withdrawal (high frequency, 0.6-2.4 Hz) and sympathoexcitation (low frequency, 0.04-0.6 Hz). Regarding to BR modulation, rats showed a significant decrease (p < 0.05) of curvature and parasympathetic bradycardic responses to Phe, without significant differences in sympathetic tachycardic responses to SNP after High-Altitude exposure. In addition, the non-stationary analysis of HRV showed a reduction of parasympathetic activation (Phe) in the High-Altitude group. Our results suggest that acute exposure to High-Altitude produces an autonomic and BR control impairment, characterized by parasympathetic withdrawal after 24 h of high-altitude exposure.
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Affiliation(s)
- Ana Rosa Beltrán
- Departamento de Educación, Facultad de Educación, Universidad de Antofagasta, Antofagasta, Chile
- Laboratorio de Fisiología Celular, Departamento Biomédico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Alexis Arce-Álvarez
- Escuela de Kinesiología, Facultad de Salud, Universidad Católica Silva Henríquez, Santiago, Chile
| | - Rodrigo Ramirez-Campillo
- Laboratory of Human Performance, Quality of Life and Wellness Research Group, Department of Physical Activity Sciences, Universidad de Los Lagos, Osorno, Chile
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Manuel Vásquez-Muñoz
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Magdalena von Igel
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Marco A. Ramírez
- Laboratorio de Fisiología Celular, Departamento Biomédico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
| | - David C. Andrade
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Pedagogía en Educación Física, Deportes y Recreación, Universidad Mayor, Santiago, Chile
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11
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Williams AM, Ainslie PN, Anholm JD, Gasho C, Subedi P, Stembridge M. Left Ventricular Twist Is Augmented in Hypoxia by β 1-Adrenergic-Dependent and β 1-Adrenergic-Independent Factors, Without Evidence of Endocardial Dysfunction. Circ Cardiovasc Imaging 2020; 12:e008455. [PMID: 31060374 DOI: 10.1161/circimaging.118.008455] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Left ventricular (LV) twist mechanics are augmented with both acute and chronic hypoxemia. Although the underlying mechanisms remain unknown, sympathetic activation and a direct effect of hypoxemia on the myocardium have been proposed, the latter of which may produce subendocardial dysfunction that is masked by larger subepicardial torque. This study therefore sought to (1) determine the individual and combined influences of β1-AR (β1-adrenergic receptor) stimulation and peripheral O2 saturation (Spo2) on LV twist in acute and chronic hypoxia and (2) elucidate whether endocardial versus epicardial mechanics respond differently to hypoxia. METHODS Twelve males (27±4 years) were tested near sea level in acute hypoxia (Spo2=82±4%) and following 3 to 6 days at 5050 m (high altitude; Spo2=83±3%). In both settings, participants received infusions of β1-AR blocker esmolol and volume-matched saline (double-blind, randomized). LV mechanics were assessed with 2-dimensional speckle-tracking echocardiography, and region-specific analysis to compare subendocardial and subepicardial mechanics. RESULTS At sea level, compared with baseline (14.8±3.0°) LV twist was reduced with esmolol (11.2±3.3°; P=0.007) and augmented during hypoxia (19.6±4.9°; P<0.001), whereas esmolol+hypoxia augmented twist compared with esmolol alone (16.5±3.3°; P<0.001). At 5050 m, LV twist was increased compared with sea level (19.5±5.4°; P=0.004), and reduced with esmolol (13.0±3.8°; P<0.001) and Spo2 normalization (12.8±3.4°; P<0.001). Moreover, esmolol+normalized Spo2 lowered twist further than esmolol alone (10.5±3.1°; P=0.036). There was no mechanics-derived evidence of endocardial dysfunction with hypoxia at sea level or high altitude. CONCLUSIONS These findings suggest LV twist is augmented in hypoxia via β1-AR-dependent and β1-AR-independent mechanisms (eg, α1-AR stimulation), but does not appear to reflect endocardial dysfunction.
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Affiliation(s)
- Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, Canada (A.M.W., P.N.A.).,Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, Canada (A.M.W., P.N.A.)
| | - James D Anholm
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Chris Gasho
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Prajan Subedi
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Mike Stembridge
- Pulmonary and Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, CA (J.D.A., C.G., P.S.)
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12
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Zera T, Moraes DJA, da Silva MP, Fisher JP, Paton JFR. The Logic of Carotid Body Connectivity to the Brain. Physiology (Bethesda) 2020; 34:264-282. [PMID: 31165684 DOI: 10.1152/physiol.00057.2018] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The carotid body has emerged as a therapeutic target for cardio-respiratory-metabolic diseases. With the expansive functions of the chemoreflex, we sought mechanisms to explain differential control of individual responses. We purport a remarkable correlation between phenotype of a chemosensory unit (glomus cell-sensory afferent) with a distinct component of the reflex response. This logic could permit differential modulation of distinct chemoreflex responses, a strategy ideal for therapeutic exploitation.
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Affiliation(s)
- Tymoteusz Zera
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw , Warsaw , Poland
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo , São Paulo , Brazil
| | - Melina P da Silva
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo , São Paulo , Brazil
| | - James P Fisher
- Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland , Auckland , New Zealand
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland , Auckland , New Zealand
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13
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Verratti V, Mrakic-Sposta S, Moriggi M, Tonacci A, Bhandari S, Migliorelli D, Bajracharya A, Bondi D, Agrò EF, Cerretelli P. Urinary physiology and hypoxia: a pilot study of moderate-altitude trekking effects on urodynamic indexes. Am J Physiol Renal Physiol 2019; 317:F1081-F1086. [DOI: 10.1152/ajprenal.00333.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exposure to high altitude is one of the most widely used models to study the adaptive response to hypoxia in humans. However, little is known about the related effects on micturition. The present study addresses the adaptive urinary responses in four healthy adult lowlanders, comparing urodynamic indexes at Kathmandu [1,450 m above sea level (a.s.l.); K1450] and during a sojourn in Namche Bazar (3,500 m a.s.l.; NB3500). The urodynamic testing consisted of cistomanometry and bladder pressure/flow measurements. Anthropometrics, electrocardiographic, and peripheral capillary oxygen saturation data were also collected. The main findings consisted of significant reductions in bladder power at maximum urine flow by ~30%, bladder contractility index by 13%, and infused volume both at first (by 57%) and urgency sensation (by 14%) to urinate, indicating a reduced cystometric capacity, at NB3500. In addition to the urinary changes, we found that oxygen saturation, body mass index, body surface area, and median RR time were all significantly reduced at altitude. We submit that the hypoxia-related parasympathetic inhibition could be the underlying mechanism of both urodynamic and heart rate adaptive responses to high-altitude exposure. Moreover, increased diuresis and faster bladder filling at altitude may trigger the anticipation of being able to void, a common cause of urgency. We believe that the present pilot study represents an original approach to the study of urinary physiology at altitude.
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Affiliation(s)
- Vittore Verratti
- Department of Psychological Sciences, Health, and Territory, University “G. d’Annunzio” of Chieti-Pescara, Chieti, Italy
- Laboratory of Clinical and Hypoxic Physiology, University “G. d’Annunzio” of Chieti-Pescara, Chieti, Italy
| | - Simona Mrakic-Sposta
- Institute of Bioimaging and Molecular Physiology, National Research Council of Italy, Segrate, Italy
| | - Manuela Moriggi
- Institute of Bioimaging and Molecular Physiology, National Research Council of Italy, Segrate, Italy
| | - Alessandro Tonacci
- Institute of Clinical Physiology, National Research Council of Italy, Pisa, Italy
| | - Suwas Bhandari
- Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | | | | | - Danilo Bondi
- Department of Neuroscience, Imaging, and Clinical Sciences, University “G. d’Annunzio” of Chieti-Pescara, Chieti, Italy
| | - Enrico Finazzi Agrò
- Department of Surgical Sciences, University of Rome “Tor Vergata” and Unit of Urology Policlinic, Tor Vergata University Hospital, Rome, Italy
| | - Paolo Cerretelli
- Institute of Bioimaging and Molecular Physiology, National Research Council of Italy, Segrate, Italy
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14
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Sanz-Quinto S, López-Grueso R, Brizuela G, Flatt AA, Moya-Ramón M. Influence of Training Models at 3,900-m Altitude on the Physiological Response and Performance of a Professional Wheelchair Athlete: A Case Study. J Strength Cond Res 2019; 33:1714-1722. [PMID: 29927887 DOI: 10.1519/jsc.0000000000002667] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Sanz-Quinto, S, López-Grueso, R, Brizuela, G, Flatt, AA, and Moya-Ramón, M. Influence of training models at 3,900-m altitude on the physiological response and performance of a professional wheelchair athlete: A case study. J Strength Cond Res 33(6): 1715-1723, 2019-This case study compared the effects of two training camps using flexible planning (FP) vs. inflexible planning (IP) at 3,860-m altitude on physiological and performance responses of an elite marathon wheelchair athlete with Charcot-Marie-Tooth disease (CMT). During IP, the athlete completed preplanned training sessions. During FP, training was adjusted based on vagally mediated heart rate variability (HRV) with specific sessions being performed when a reference HRV value was attained. The camp phases were baseline in normoxia (BN), baseline in hypoxia (BH), specific training weeks 1-4 (W1, W2, W3, W4), and Post-camp (Post). Outcome measures included the root mean square of successive R-R interval differences (rMSSD), resting heart rate (HRrest), oxygen saturation (SO2), diastolic blood pressure and systolic blood pressure, power output and a 3,000-m test. A greater impairment of normalized rMSSD (BN) was shown in IP during BH (57.30 ± 2.38% vs. 72.94 ± 11.59%, p = 0.004), W2 (63.99 ± 10.32% vs. 81.65 ± 8.87%, p = 0.005), and W4 (46.11 ± 8.61% vs. 59.35 ± 6.81%, p = 0.008). At Post, only in FP was rMSSD restored (104.47 ± 35.80%). Relative changes were shown in power output (+3 W in IP vs. +6 W in FP) and 3,000-m test (-7s in IP vs. -16s in FP). This case study demonstrated that FP resulted in less suppression and faster restoration of rMSSD and more positive changes in performance than IP in an elite wheelchair marathoner with CMT.
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Affiliation(s)
| | | | - Gabriel Brizuela
- Department of Physical and Sports Education, University of Valencia, Valencia, Spain
| | - Andrew A Flatt
- Department of Health Science and Kinesiology, Georgia Southern University, Savannah, Georgia
| | - Manuel Moya-Ramón
- Sports Research Center, Miguel Hernandez University, Elche, Spain.,Department of Health Psychology, Miguel Hernandez University, Elche, Institute for Health and Biomedical Research (ISABIAL-FISABIO Foundation), Alicante, Spain
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15
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Teixeira AL. Lifelong high-altitude hypoxia induces arterial baroreflex adaptations: new insights and future directions. J Physiol 2019; 597:3253-3254. [PMID: 31078133 DOI: 10.1113/jp278174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- André L Teixeira
- Neuro V̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, DF, Brazil
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16
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Hilty MP, Merz TM, Hefti U, Ince C, Maggiorini M, Pichler Hefti J. Recruitment of non-perfused sublingual capillaries increases microcirculatory oxygen extraction capacity throughout ascent to 7126 m. J Physiol 2019; 597:2623-2638. [PMID: 30843200 DOI: 10.1113/jp277590] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 03/05/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS A physiological response to increase microcirculatory oxygen extraction capacity at high altitude is to recruit capillaries. In the present study, we report that high altitude-induced sublingual capillary recruitment is an intrinsic mechanism of the sublingual microcirculation that is independent of changes in cardiac output, arterial blood pressure or systemic vascular hindrance. Using a topical nitroglycerin challenge to the sublingual microcirculation, we show that high altitude-related capillary recruitment is a functional response of the sublingual microcirculation as opposed to an anatomical response associated with angiogenesis. The concurrent presence of a low capillary density and high microvascular reactivity to topical nitroglycerin at sea level was found to be associated with a failure to reach the summit, whereas the presence of a high baseline capillary density with the ability to further increase maximum recruitable capillary density upon ascent to an extreme altitude was associated with summit success. ABSTRACT A high altitude (HA) stay is associated with an increase in sublingual capillary total vessel density (TVD), suggesting microvascular recruitment. We hypothesized that microvascular recruitment occurs independent of cardiac output changes, that it relies on haemodynamic changes within the microcirculation as opposed to structural changes and that microcirculatory function is related to individual performance at HA. In 41 healthy subjects, sublingual handheld vital microscopy and echocardiography were performed at sea level (SL), as well as at 6022 m (C2) and 7042 m (C3), during ascent to 7126 m within 21 days. Sublingual topical nitroglycerin was applied to measure microvascular reactivity and maximum recruitable TVD (TVDNG ). HA exposure decreased resting cardiac output, whereas TVD (mean ± SD) increased from 18.81 ± 3.92 to 20.92 ± 3.66 and 21.25 ± 2.27 mm mm-2 (P < 0.01). The difference between TVD and TVDNG was 2.28 ± 4.59 mm mm-2 at SL (P < 0.01) but remained undetectable at HA. Maximal TVDNG was observed at C3. Those who reached the summit (n = 15) demonstrated higher TVD at SL (P < 0.01), comparable to TVDNG in non-summiters (n = 21) at SL and in both groups at C2. Recruitment of sublingual capillary TVD to increase microcirculatory oxygen extraction capacity at HA was found to be an intrinsic mechanism of the microcirculation independent of cardiac output changes. Microvascular reactivity to topical nitroglycerin demonstrated that HA-related capillary recruitment is a functional response as opposed to a structural change. The performance of the vascular microcirculation needed to reach the summit was found to be associated with a higher TVD at SL and the ability to further increase TVDNG upon ascent to extreme altitude.
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Affiliation(s)
- Matthias Peter Hilty
- Intensive Care Unit, University Hospital of Zurich, Zurich, Switzerland.,Department of Intensive Care, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
| | - Tobias Michael Merz
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.,Cardiovascular Intensive Care Unit, Auckland City Hospital, Auckland, New Zealand
| | - Urs Hefti
- Swiss Sportclinic, Bern, Switzerland
| | - Can Ince
- Department of Intensive Care, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
| | - Marco Maggiorini
- Intensive Care Unit, University Hospital of Zurich, Zurich, Switzerland
| | - Jacqueline Pichler Hefti
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.,Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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17
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O'Brien KA, Pollock RD, Stroud M, Lambert RJ, Kumar A, Atkinson RA, Green DA, Anton-Solanas A, Edwards LM, Harridge SDR. Human physiological and metabolic responses to an attempted winter crossing of Antarctica: the effects of prolonged hypobaric hypoxia. Physiol Rep 2019. [PMID: 29521037 PMCID: PMC5843758 DOI: 10.14814/phy2.13613] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
An insufficient supply of oxygen to the tissues (hypoxia), as is experienced upon high‐altitude exposure, elicits physiological acclimatization mechanisms alongside metabolic remodeling. Details of the integrative adaptive processes in response to chronic hypobaric hypoxic exposure remain to be sufficiently investigated. In this small applied field study, subjects (n = 5, male, age 28–54 years) undertook a 40 week Antarctica expedition in the winter months, which included 24 weeks residing above 2500 m. Measurements taken pre‐ and postexpedition revealed alterations to glucose and fatty acid resonances within the serum metabolic profile, a 7.8 (±3.6)% increase in respiratory exchange ratio measured during incremental exercise (area under curve, P > 0.01, mean ± SD) and a 2.1(±0.8) % decrease in fat tissue (P < 0.05) postexpedition. This was accompanied by an 11.6 (±1.9) % increase (P > 0.001) in VO2 max corrected to % lean mass postexpedition. In addition, spine bone mineral density and lung function measures were identified as novel parameters of interest. This study provides, an in‐depth characterization of the responses to chronic hypobaric hypoxic exposure in one of the most hostile environments on Earth.
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Affiliation(s)
- Katie A O'Brien
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom.,Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Ross D Pollock
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom
| | - Mike Stroud
- Biomedical Research Centre in Nutrition, Southampton University Hospitals Trust, Southampton, United Kingdom
| | - Rob J Lambert
- Department of Trauma and Orthopaedics, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom
| | - Alex Kumar
- Department of Medicine and Physiology, Fribourg, Switzerland.,Department of Primary Care & Public Health Sciences, King's College London, London, United Kingdom
| | - Robert A Atkinson
- Centre for Biomolecular Spectroscopy and Randall Division of Cell and Molecular Biophysics, King's College London Guy's Campus London, London, United Kingdom
| | - David A Green
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom.,KBRwyle, European Astronaut Centre, European Space Agency, Linder Höhe, Cologne, Germany
| | | | - Lindsay M Edwards
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom.,Respiratory Data Sciences Group, Respiratory TAU, GlaxosmithKline Medicines Research, Stevenage, United Kingdom
| | - Steve D R Harridge
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom
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18
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Differential responses of autonomic function in sea level residents, acclimatized lowlanders at >3500 m and Himalayan high altitude natives at >3500 m: A cross-sectional study. Respir Physiol Neurobiol 2018; 254:40-48. [DOI: 10.1016/j.resp.2018.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 04/03/2018] [Accepted: 04/07/2018] [Indexed: 11/22/2022]
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19
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Response to: Comment on "Soluble Urokinase-Type Plasminogen Activator Receptor Plasma Concentration May Predict Susceptibility to High Altitude Pulmonary Edema". Mediators Inflamm 2018; 2018:8036759. [PMID: 29853793 PMCID: PMC5954876 DOI: 10.1155/2018/8036759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 03/28/2018] [Indexed: 11/18/2022] Open
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20
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Attias J, Bieles J, Carvil P, Laing C, Lewis F, Jaka O, O'Brien K, Ruchaya P. Altitude exposure and increased heart rate: the role of the parasympathetic nervous system. J Physiol 2017; 595:4589-4590. [PMID: 28409829 DOI: 10.1113/jp274220] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Julia Attias
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Julie Bieles
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Philip Carvil
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Charles Laing
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Fiona Lewis
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Oihane Jaka
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Katie O'Brien
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
| | - Prashant Ruchaya
- Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK
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21
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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] [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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