Document Detail

Ventilatory response to 8 h of isocapnic and poikilocapnic hypoxia in humans.
MedLine Citation:
PMID:  7775303     Owner:  NLM     Status:  MEDLINE    
Almost all studies of the effects of prolonged hypoxia on ventilation (VE) in humans have been performed with the end-tidal PCO2 (PETCO2) left uncontrolled. The purpose of this study was to compare the effects of 8 h of hypoxia with PETCO2 held constant with 8 h of hypoxia with PETCO2 left uncontrolled. Ten subjects completed the study. Each was seated inside a chamber in which the inspired gas could be controlled so as to maintain the desired partial pressures of end-tidal gases (sampled via nasal catheter) constant (see L.S.G.E. Howard et al. J. Appl. Physiol. 78:1088-1091, 1995.). Three 8-h protocols were employed: 1) isocapnic hypoxia, at an end-tidal PO2 of 55 Torr with PETCO2 held at the subject's resting value; 2) poikilocapnic hypoxia, at the same end-tidal PO2; and 3) control, where the inspired gas was air. VE was measured (over 3 min) at 0 and 20 min and at hourly intervals between 1.5 and 7.5 h. There was a rise in VE during isocapnic hypoxia [from an initial VE of 16.2 +/- 1.3 (SE) l/min to a final VE of 24.8 +/- 1.6 l/min], which was significant compared with poikilocapnic hypoxia and control values (P < 0.001, analysis of variance). There was no significant progressive rise in VE during poikilocapnic hypoxia compared with control values. These results show that isocapnic hypoxia produces a progressive increase in VE when sustained over an 8-h period. The onset of this response is faster than has been noted in studies of the progressive rise in VE associated with the poikilocapnic hypoxia of altitude.
L S Howard; P A Robbins
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  78     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1995 Mar 
Date Detail:
Created Date:  1995-07-11     Completed Date:  1995-07-11     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1092-7     Citation Subset:  IM    
University of Oxford, University Laboratory of Physiology, United Kingdom.
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MeSH Terms
Adaptation, Physiological
Anoxia / physiopathology*
Hypocapnia / physiopathology*
Tidal Volume
Time Factors
Grant Support
//Wellcome Trust

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