Document Detail

The breathing route dependence of ventilatory responses to hypercapnia and exercise is modulated by upper airway resistance.
MedLine Citation:
PMID:  10612565     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: The ventilatory response to hypercapnia is greater breathing orally than nasally. METHODOLOGY: We hypothesize that this is due to higher nasal resistance to airflow compared with oral resistance. Seven normal male subjects were studied during both progressive hyperoxic hypercapnia (HC) and exercise (EX) until ventilation exceeded 40 L/min. Under each condition, subjects breathed via the nose only or the mouth only. For each breathing route, ventilation and pathway resistance were calculated simultaneously at the highest common exercise workload (140 +/- 20 watt; mean +/- SE) or the same end-tidal CO2 level (8.0 +/- 0.5%). RESULTS: The ventilatory response breathing nasally was decreased by a similar amount for both EX and HC when compared with the oral route. The difference between nasal and oral ventilation was highly correlated with the difference between nasal resistance and oral resistance for both EX and HC (linear regression analysis; r = 0.91 for EX and r = 0.86 for HC; both P < 0.01). CONCLUSION: We conclude that the breathing route dependence of ventilatory responses to respiratory stimuli in normal subjects is independent of the method of stimulation and is substantially determined by the added resistance of nasal breathing.
Y X Shi; M Seto-Poon; J R Wheatley
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Publication Detail:
Type:  Clinical Trial; Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Respirology (Carlton, Vic.)     Volume:  4     ISSN:  1323-7799     ISO Abbreviation:  Respirology     Publication Date:  1999 Dec 
Date Detail:
Created Date:  2000-02-15     Completed Date:  2000-02-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9616368     Medline TA:  Respirology     Country:  AUSTRALIA    
Other Details:
Languages:  eng     Pagination:  331-8     Citation Subset:  IM; S    
Department of Respiratory Medicine, University of Sydney, Westmead Hospital, New South Wales, Australia.
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MeSH Terms
Airway Resistance / physiology*
Analysis of Variance
Exercise Test*
Linear Models
Mouth Breathing / physiopathology
Nasal Cavity / physiology*
Reference Values
Respiratory Mechanics
Sensitivity and Specificity

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