| Cardiovascular determinants of maximal oxygen consumption in upright and supine posture at the end of prolonged bed rest in humans. | |
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MedLine Citation:
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PMID: 20348037 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We tested the hypothesis that, after bed rest, maximal oxygen consumption ( VO₂max ) decreases more upright than supine, because of adequate cardiovascular response supine, but not upright. On 9 subjects, we determined VO₂max and maximal cardiac output (Q ) upright and supine, before and after (reambulation day upright, the following day supine) 35-day bed rest, by classical steady state protocol. Oxygen consumption, heart rate (f(H)) and stroke volume (Q(st)) were measured by a metabolic cart, electrocardiography and Modelflow from pulse pressure profiles, respectively. We computed Q as f(H) times Q(st), and systemic oxygen flow ( QaO₂) as Q. times arterial oxygen concentration, obtained after haemoglobin and arterial oxygen saturation measurements. Before bed rest, all parameters at maximal exercise were similar upright and supine. After bed rest, VO₂max was lower (p<0.05) than before, both upright (-38.6%) and supine (-17.0%), being 30.8% higher supine than upright. Maximal Q(st) decreased upright (-44.3%), but not supine (+3.7%), being 98.9% higher supine than upright. Maximal Q decreased upright (-45.1%), but not supine (+9.0%), being higher supine than upright (+98.4%). Maximal QaO₂ decreased upright (-37.8%), but not supine (+14.8%), being higher (+74.8%) upright than supine. After bed rest, the cardiovascular response (i) did not affect VO₂max supine, (ii) partially explained the VO₂max decrease upright, and (iii) caused the VO₂max differences between postures. We speculate that impaired peripheral oxygen transfer and/or utilisation may explain the VO₂max decrease supine and the fraction of VO₂max decrease upright unexplained by cardiovascular responses. |
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Authors:
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Aurélien Bringard; Silvia Pogliaghi; Alessandra Adami; Gabriela De Roia; Frédéric Lador; Daniela Lucini; Paolo Pizzinelli; Carlo Capelli; Guido Ferretti |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2010-03-27 |
Journal Detail:
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Title: Respiratory physiology & neurobiology Volume: 172 ISSN: 1878-1519 ISO Abbreviation: Respir Physiol Neurobiol Publication Date: 2010 Jun |
Date Detail:
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Created Date: 2010-06-14 Completed Date: 2010-09-17 Revised Date: 2010-10-25 |
Medline Journal Info:
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Nlm Unique ID: 101140022 Medline TA: Respir Physiol Neurobiol Country: Netherlands |
Other Details:
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Languages: eng Pagination: 53-62 Citation Subset: IM |
Copyright Information:
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Copyright 2010 Elsevier B.V. All rights reserved. |
Affiliation:
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Département des Neurosciences Fondamentales, Centre Médical Universitaire, 1 rue Michel Servet, CH-1211 Geneve 4, Switzerland. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Bed Rest* Blood Pressure / physiology Cardiac Output / physiology Cardiovascular System* Heart Rate / physiology Humans Male Oxygen Consumption / physiology* Posture / physiology* Respiratory Function Tests / methods Stroke Volume / physiology Supine Position / physiology Young Adult |
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