Document Detail

Cardiovascular determinants of maximal oxygen consumption in upright and supine posture at the end of prolonged bed rest in humans.
MedLine Citation:
PMID:  20348037     Owner:  NLM     Status:  MEDLINE    
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.
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:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-27
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  172     ISSN:  1878-1519     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2010 Jun 
Date Detail:
Created Date:  2010-06-14     Completed Date:  2010-09-17     Revised Date:  2010-10-25    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  53-62     Citation Subset:  IM    
Copyright Information:
Copyright 2010 Elsevier B.V. All rights reserved.
Département des Neurosciences Fondamentales, Centre Médical Universitaire, 1 rue Michel Servet, CH-1211 Geneve 4, Switzerland.
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MeSH Terms
Bed Rest*
Blood Pressure / physiology
Cardiac Output / physiology
Cardiovascular System*
Heart Rate / physiology
Oxygen Consumption / physiology*
Posture / physiology*
Respiratory Function Tests / methods
Stroke Volume / physiology
Supine Position / physiology
Young Adult

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