Document Detail


Relationship between inspired and expired gas temperatures in a hyperbaric environment.
MedLine Citation:
PMID:  1480846     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
When breathing room air at sea level the expired gas temperature (TE) increases in proportion to the inspired one (TI). Previous studies conducted under hyperbaric conditions have assumed that the TE vs TI relationship was the same when humans breathed room air at atmospheric pressure or helium-oxygen mixture under hyperbaric conditions. We hypothesized that the use of dilutant gases, as helium (He) or hydrogen (H2), having low density but high specific heat compared to nitrogen, could change the TE vs TI regression. The present study was conducted on 3 professional divers participating in the COMEX Hydra IX experiment. Three conditions were studied: A, (23.5 ATA, He-H2-O2 mixture); B, (21 ATA, H2-O2 mixture); and C, (21 ATA, He-O2 mixture). In each condition six different inspired temperatures were tested, while minute ventilation, TI and TE values were measured simultaneously. In all cases a linear relationship was found between TE and TI, but the slopes of the regression lines obtained in conditions A and B (gas mixture containing H2) were significantly lower than in condition C (He-O2 mixture). Computation of the convective respiratory heat loss (Cr) revealed that, when the subjects breathed the coldest gas mixtures (+10 degrees C), Cr value was 1.6 times higher in condition B than in C. These data are consistent with theoretical considerations and they demonstrate that a single equation cannot be used to predict the TE vs TI relationship in all environmental circumstances.
Authors:
H Burnet; M Reynaud-Gaubert; M Lucciano; Y Jammes
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Respiration physiology     Volume:  90     ISSN:  0034-5687     ISO Abbreviation:  Respir Physiol     Publication Date:  1992 Dec 
Date Detail:
Created Date:  1993-02-08     Completed Date:  1993-02-08     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0047142     Medline TA:  Respir Physiol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  377-86     Citation Subset:  IM    
Affiliation:
Laboratoire de Biologie des Hautes pressions, URA 1330-CNRS, Faculté de Médecine-Nord, Marseille, France.
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MeSH Terms
Descriptor/Qualifier:
Body Temperature Regulation
Gases*
Helium
Humans
Hydrogen
Hyperbaric Oxygenation*
Oxygen
Respiration*
Temperature*
Chemical
Reg. No./Substance:
0/Gases; 1333-74-0/Hydrogen; 7440-59-7/Helium; 7782-44-7/Oxygen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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