Document Detail

The contribution of chemoreflex drives to resting breathing in man.
MedLine Citation:
PMID:  11429624     Owner:  NLM     Status:  MEDLINE    
The contribution of automatic drives to breathing at rest, relative to behavioural drives such as "wakefulness", has been a subject of debate. We measured the combined central and peripheral chemoreflex contribution to resting ventilation using a modified rebreathing method that included a prior hyperventilation and addition of oxygen to maintain isoxia at a P(ET,O2) (end-tidal partial pressure of oxygen) of 100 mmHg. During rebreathing, ventilation was unrelated to P(ET,CO2) (end-tidal partial pressure of carbon dioxide) in the hypocapnic range, but after a threshold P(ET,CO2) was exceeded, ventilation increased linearly with P(ET,CO2). We considered the sub-threshold ventilation to be an estimate of the behavioural drives to breathe (mean +/- S.E.M. = 3.1 +/- 0.5 l min(-1)), and compared it to ventilation at rest (mean +/- S.E.M. = 9.1 +/- 0.7 l min(-1)). The difference was significant (Student's paired t test, P < 0.001). We also considered the threshold P(CO2) observed during rebreathing to be an estimate of the chemoreflex threshold at rest (mean +/- S.E.M. = 42.0 +/- 0.5 mmHg). However, P(ET,CO2) during rebreathing estimates mixed venous or tissue P(CO2), whereas the resting P(ET,CO2) during resting breathing estimates P(a,CO2) (arterial partial pressure of carbon dioxide). The chemoreflex threshold measured during rebreathing was therefore reduced by the difference in P(ET,CO2) at rest and at the start of rebreathing (the plateau estimates the mixed venous P(CO2) at rest) in order to make comparisons. The corrected chemoreflex thresholds (mean +/- S.E.M. = 26.0 +/- 0.9 mmHg) were significantly less (paired Student's t test, P < 0.001) than the resting P(ET,CO2) values (mean +/- S.E.M. = 34.3 +/- 0.5 mmHg). We conclude that both the behavioural and chemoreflex drives contribute to resting ventilation. Experimental Physiology (2001) 86.1, 109-116.
S Mahamed; A F Ali; D Ho; B Wang; J Duffin
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental physiology     Volume:  86     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2001 Jan 
Date Detail:
Created Date:  2001-06-28     Completed Date:  2001-08-09     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  109-16     Citation Subset:  IM    
Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
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MeSH Terms
Behavior / physiology
Carbon Dioxide
Chemoreceptor Cells / physiology*
Differential Threshold
Partial Pressure
Reflex / physiology*
Respiratory Physiological Phenomena
Tidal Volume
Reg. No./Substance:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen

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