Document Detail

Ventilatory response to asphyxia in conscious rats: effect of ambient and body temperatures.
MedLine Citation:
PMID:  9628229     Owner:  NLM     Status:  MEDLINE    
In many mammals the ventilatory response to hypoxia depends on ambient temperature (Ta), largely because of the hypometabolic effects of hypoxia below thermoneutrality. We questioned whether the ventilatory response to asphyxia also depends upon Ta, and the role played by metabolism and body temperature (Tb). Oxygen consumption (VO2) and pulmonary ventilation (VE) were measured in conscious rats at Ta = 27 degrees C (warm) and 11 degrees C (cold), breathing air or two levels of asphyxic gases, moderate (10% O2-4% CO2), or severe (10% O2-8% CO2), for approximately 30 min each. In the cold, the pattern of the VE response to moderate asphyxia was qualitatively similar to that seen in hypoxia alone, i.e the attained VE/VO2 was similar in warm and cold conditions, with, in the latter, a major drop in VO2 and little or no hyperpnea. During severe asphyxia, however, the VE/VO2 attained in the cold was less than in the warm, and it was accompanied by a large drop in Tb (approximately 6 degrees C). Blood gases confirmed the lower asphyxic hyperventilation in the cold. By maintaining Tb at 38 degrees C with an implanted abdominal heat exchanger, the VE/VO2 levels attained during asphyxia were the same between cold and warm conditions. We conclude that (a) the VE response to asphyxia is Ta-dependent, largely because of the hypometabolic effect of the hypoxic component in the cold, (b) during moderate asphyxia the hypercapnic component is qualitatively unimportant, and (c) with severe asphyxia the hypercapnia becomes an important contributor to the Ta-sensitivity by aggravating the decrease in Tb in the cold and lowering VE sensitivity.
J P Mortola; M Maskrey
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Respiration physiology     Volume:  111     ISSN:  0034-5687     ISO Abbreviation:  Respir Physiol     Publication Date:  1998 Mar 
Date Detail:
Created Date:  1998-08-13     Completed Date:  1998-08-13     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0047142     Medline TA:  Respir Physiol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  233-46     Citation Subset:  IM; S    
Department of Anatomy and Physiology, University of Tasmania at Hobart, Australia.
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MeSH Terms
Anoxia / physiopathology
Asphyxia / physiopathology*
Body Temperature / physiology*
Hypercapnia / physiopathology
Oxygen Consumption / physiology
Rats, Wistar
Reference Values
Respiration / physiology*

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