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Exposure to acute normobaric hypoxia results in adaptions of both the macro- and microcirculatory system. Sci Rep 2020; 10:20938. [PMID: 33262355 PMCID: PMC7708486 DOI: 10.1038/s41598-020-77724-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 10/14/2020] [Indexed: 12/19/2022] Open
Abstract
Although acute hypoxia is of utmost pathophysiologic relevance in health and disease, studies on its effects on both the macro- and microcirculation are scarce. Herein, we provide a comprehensive analysis of the effects of acute normobaric hypoxia on human macro- and microcirculation. 20 healthy participants were enrolled in this study. Hypoxia was induced in a normobaric hypoxia chamber by decreasing the partial pressure of oxygen in inhaled air stepwisely (pO2; 21.25 kPa (0 k), 16.42 kPa (2 k), 12.63 kPa (4 k) and 9.64 kPa (6 k)). Macrocirculatory effects were assessed by cardiac output measurements, microcirculatory changes were investigated by sidestream dark-field imaging in the sublingual capillary bed and videocapillaroscopy at the nailfold. Exposure to hypoxia resulted in a decrease of systemic vascular resistance (p < 0.0001) and diastolic blood pressure (p = 0.014). Concomitantly, we observed an increase in heart rate (p < 0.0001) and an increase of cardiac output (p < 0.0001). In the sublingual microcirculation, exposure to hypoxia resulted in an increase of total vessel density, proportion of perfused vessels and perfused vessel density. Furthermore, we observed an increase in peripheral capillary density. Exposure to acute hypoxia results in vasodilatation of resistance arteries, as well as recruitment of microvessels of the central and peripheral microcirculation. The observed macro- and microcirculatory effects are most likely a result from compensatory mechanisms to ensure adequate tissue oxygenation.
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Osawa T, Arimitsu T, Takahashi H. Hypoxia affects tissue oxygenation differently in the thigh and calf muscles during incremental running. Eur J Appl Physiol 2017; 117:2057-2064. [PMID: 28819691 DOI: 10.1007/s00421-017-3696-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Accepted: 08/04/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE The present study was performed to determine the impact of hypoxia on working muscle oxygenation during incremental running, and to compare tissue oxygenation between the thigh and calf muscles. METHODS Nine distance runners and triathletes performed incremental running tests to exhaustion under normoxic and hypoxic conditions (fraction of inspired oxygen = 0.15). Peak pulmonary oxygen uptake ([Formula: see text]) and tissue oxygen saturation (StO2) were measured simultaneously in both the vastus lateralis and medial gastrocnemius. RESULTS Hypoxia significantly decreased peak running speed and [Formula: see text] (p < 0.01). During incremental running, StO2 in the vastus lateralis decreased almost linearly, and the rate of decrease from warm-up (180 m min-1) to [Formula: see text] was significantly greater than in the medial gastrocnemius under both normoxic and hypoxic conditions (p < 0.01). StO2 in both muscles was significantly decreased under hypoxic compared with normoxic conditions at all running speeds (p < 0.01). The rate at which StO2 was decreased by hypoxia was greater in the vastus lateralis as the running speed increased, whereas it changed little in the medial gastrocnemius. CONCLUSIONS These results suggest that the thigh is more deoxygenated than the calf under hypoxic conditions, and that the effects of hypoxia on tissue oxygenation differ between these two muscles during incremental running.
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Affiliation(s)
- Takuya Osawa
- COI Project Center, Juntendo University, 1-1, Hiraga-gakuendai, Inzai-shi, Chiba, Japan. .,Department of Sports Science, Japan Institute of Sports Sciences, Tokyo, Japan.
| | - Takuma Arimitsu
- Department of Sports Science, Japan Institute of Sports Sciences, Tokyo, Japan.,Faculty of Sport and Health Science, Ritsumeikan University, Shiga, Japan
| | - Hideyuki Takahashi
- Department of Sports Science, Japan Institute of Sports Sciences, Tokyo, Japan
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Peltonen JE, Hägglund H, Koskela-Koivisto T, Koponen AS, Aho JM, Rissanen APE, Shoemaker JK, Tiitinen A, Tikkanen HO. Alveolar gas exchange, oxygen delivery and tissue deoxygenation in men and women during incremental exercise. Respir Physiol Neurobiol 2013; 188:102-12. [DOI: 10.1016/j.resp.2013.05.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 04/24/2013] [Accepted: 05/13/2013] [Indexed: 01/08/2023]
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Poole DC, Copp SW, Hirai DM, Musch TI. Dynamics of muscle microcirculatory and blood-myocyte O(2) flux during contractions. Acta Physiol (Oxf) 2011; 202:293-310. [PMID: 21199399 DOI: 10.1111/j.1748-1716.2010.02246.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The O(2) requirements of contracting skeletal muscle may increase 100-fold above rest. In 1919, August Krogh's brilliant insights recognized the capillary as the principal site for this increased blood-myocyte O(2) flux. Based on the premise that most capillaries did not sustain RBC flux at rest, Krogh proposed that capillary recruitment [i.e. initiation of red blood cell (RBC) flux in previously non-flowing capillaries] increased the capillary surface area available for O(2) flux and reduced mean capillary-to-mitochondrial diffusion distances. More modern experimental approaches reveal that most muscle capillaries may support RBC flux at rest. Thus, rather than contraction-induced capillary recruitment per se, increased RBC flux and haematocrit within already-flowing capillaries probably elevate perfusive and diffusive O(2) conductances and hence blood-myocyte O(2) flux. Additional surface area for O(2) exchange is recruited but, crucially, this may occur along the length of already-flowing capillaries (i.e. longitudinal recruitment). Today, the capillary is still considered the principal site for O(2) and substrate delivery to contracting skeletal muscle. Indeed, the presence of very low intramyocyte O(2) partial pressures (PO(2)s) and the absence of intramyocyte PO(2) gradients, whilst refuting the relevance of diffusion distances, place an even greater importance on capillary hemodynamics. This emergent picture calls for a paradigm-shift in our understanding of the function of capillaries by de-emphasizing de novo'capillary recruitment'. Diseases such as heart failure impair blood-myocyte O(2) flux, in part, by decreasing the proportion of RBC-flowing capillaries. Knowledge of capillary function in healthy muscle is requisite for identification of pathology and efficient design of therapeutic treatments.
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Affiliation(s)
- D C Poole
- Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS, USA.
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Heinonen IH, Kemppainen J, Kaskinoro K, Peltonen JE, Borra R, Lindroos M, Oikonen V, Nuutila P, Knuuti J, Boushel R, Kalliokoski KK. Regulation of human skeletal muscle perfusion and its heterogeneity during exercise in moderate hypoxia. Am J Physiol Regul Integr Comp Physiol 2010; 299:R72-9. [PMID: 20427728 DOI: 10.1152/ajpregu.00056.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although many effects of both acute and chronic hypoxia on the circulation are well characterized, the distribution and regulation of blood flow (BF) heterogeneity in skeletal muscle during systemic hypoxia is not well understood in humans. We measured muscle BF within the thigh muscles of nine healthy young men using positron emission tomography during one-leg dynamic knee extension exercise in normoxia and moderate physiological systemic hypoxia (14% O(2) corresponding to approximately 3,400 m of altitude) without and with local adenosine receptor inhibition with femoral artery infusion of aminophylline. Systemic hypoxia reduced oxygen extraction of the limb but increased muscle BF, and this flow increment was confined solely to the exercising quadriceps femoris muscle. Exercising muscle BF heterogeneity was reduced from rest (P = 0.055) but was not affected by hypoxia. Adenosine receptor inhibition had no effect on capillary BF during exercise in either normoxia or hypoxia. Finally, one-leg exercise increased muscle BF heterogeneity both in the resting posterior hamstring part of the exercising leg and in the resting contralateral leg, whereas mean BF was unchanged. In conclusion, the results show that increased BF during one-leg exercise in moderate hypoxia is confined only to the contracting muscles, and the working muscle hyperemia appears not to be directly mediated by adenosine. Increased flow heterogeneity in noncontracting muscles likely reflects sympathetic nervous constraints to curtail BF increments in areas other than working skeletal muscles, but this effect is not potentiated in moderate systemic hypoxia during small muscle mass exercise.
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Affiliation(s)
- Ilkka H Heinonen
- Turku PET Centre, Turku University Hospital, University of Turku, Turku, Finland.
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Ponsot E, Dufour SP, Doutreleau S, Lonsdorfer-Wolf E, Lampert E, Piquard F, Geny B, Mettauer B, Ventura-Clapier R, Richard R. Impairment of maximal aerobic power with moderate hypoxia in endurance athletes: do skeletal muscle mitochondria play a role? Am J Physiol Regul Integr Comp Physiol 2010; 298:R558-66. [DOI: 10.1152/ajpregu.00216.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigates the role of central vs. peripheral factors in the limitation of maximal oxygen uptake (V̇o2max) with moderate hypoxia [inspired fraction (FiO2) =14.5%]. Fifteen endurance-trained athletes performed maximal cycle incremental tests to assess V̇o2max, maximal cardiac output (Q̇max), and maximal arteriovenous oxygen (a-vO2) difference in normoxia and hypoxia. Muscle biopsies of vastus lateralis were taken 1 wk before the cycling tests to evaluate maximal muscle oxidative capacity (V̇max) and sensitivity of mitochondrial respiration to ADP ( Km) on permeabilized muscle fibers in situ. Those athletes exhibiting the largest reduction of V̇o2max in moderate hypoxia (Severe Loss group: −18 ± 2%) suffered from significant reductions in Q̇max (−4 ± 1%) and maximal a-vO2 difference (−14 ± 2%). Athletes who well tolerated hypoxia, as attested by a significantly smaller drop of V̇o2max with hypoxia (Moderate Loss group: −7 ± 1%), also display a blunted Q̇max (−9 ± 2%) but, conversely, were able to maintain maximal a-vO2 difference (+1 ± 2%). Though V̇max was similar in the two experimental groups, the smallest reduction of V̇o2max with moderate hypoxia was observed in those athletes presenting the lowest apparent Km for ADP in the presence of creatine ( Km+Cr). In already-trained athletes with high muscular oxidative capacities, the qualitative, rather than quantitative, aspects of the mitochondrial function may constitute a limiting factor to aerobic ATP turnover when exercising at low FiO2, presumably through the functional coupling between the mitochondrial creatine kinase and ATP production. This study suggests a potential role for peripheral factors, including the alteration of cellular homeostasis in active muscles, in determining the tolerance to hypoxia in maximally exercising endurance-trained athletes.
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Affiliation(s)
- Elodie Ponsot
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
- School of Health and Medical Sciences, Örebro University, Örebro, Sweden
| | - Stéphane P. Dufour
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
- UFR STAPS, Université de Strasbourg, Strasbourg, France
| | - Stéphane Doutreleau
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
| | - Evelyne Lonsdorfer-Wolf
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
| | - Eliane Lampert
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
| | - François Piquard
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
| | - Bernard Geny
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
| | - Bertrand Mettauer
- Service de Cardiologie, Hôpitaux Civils de Colmar, Colmar, France; and
| | | | - Ruddy Richard
- Service de Physiologie et d'Explorations Fonctionnelles, Hôpital Civil and Département de Physiologie, UPRES E.A. 3072, Faculté de Médecine, Strasbourg, France
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Bourdillon N, Mollard P, Letournel M, Beaudry M, Richalet JP. Interaction between hypoxia and training on NIRS signal during exercise: Contribution of a mathematical model. Respir Physiol Neurobiol 2009; 169:50-61. [DOI: 10.1016/j.resp.2009.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 08/17/2009] [Accepted: 08/19/2009] [Indexed: 10/20/2022]
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