Document Detail

Vagal nerve activity contributes to improve the efficiency of pulmonary gas exchange in hypoxic humans.
MedLine Citation:
PMID:  16809376     Owner:  NLM     Status:  MEDLINE    
The aim of this study was to test our hypothesis that both phasic cardiac vagal activity and tonic pulmonary vagal activity, estimated as respiratory sinus arrhythmia (RSA) and anatomical dead space volume, respectively, contribute to improve the efficiency of pulmonary gas exchange in humans. We examined the effect of blocking vagal nerve activity with atropine on pulmonary gas exchange. Ten healthy volunteers inhaled hypoxic gas with constant tidal volume and respiratory frequency through a respiratory circuit with a respiratory analyser. Arterial partial pressure of O(2) (P(aO(2))) and arterial oxygen saturation (S(pO(2))) were measured, and alveolar-to-arterial P(O(2)) difference (D(A-aO(2))) was calculated. Anatomical dead space (V(D,an)), alveolar dead space (V(D,alv)) and the ratio of physiological dead space to tidal volume (V(D,phys)/V(T)) were measured. Electrocardiogram was recorded, and the amplitude of R-R interval variability in the high-frequency component (RRIHF) was utilized as an index of RSA magnitude. These parameters of pulmonary function were measured before and after administration of atropine (0.02 mg kg(-1)). Decreased RRIHF (P < 0.01) was accompanied by decreases in P(aO(2)) and S(pO(2)) (P < 0.05 and P < 0.01, respectively) and an increase in D(A-aO(2)) (P < 0.05). Anatomical dead space, V(D,alv) and V(D,phys)/V(T) increased (P < 0.01, P < 0.05 and P < 0.01, respectively) after atropine administration. The blockade of the vagal nerve with atropine resulted in an increase in V(D,an) and V(D,alv) and a deterioration of pulmonary oxygenation, accompanied by attenuation of RSA. Our findings suggest that both phasic cardiac and tonic pulmonary vagal nerve activity contribute to improve the efficiency of pulmonary gas exchange in hypoxic conscious humans.
Shoji Ito; Hiroshi Sasano; Nobuko Sasano; Junichiro Hayano; Joseph A Fisher; Hirotada Katsuya
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-06-29
Journal Detail:
Title:  Experimental physiology     Volume:  91     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2006 Sep 
Date Detail:
Created Date:  2006-09-01     Completed Date:  2006-10-30     Revised Date:  2008-06-24    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  935-41     Citation Subset:  IM    
Department of Anaesthesiology and Medical Crisis Management, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467-8601, Japan.
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MeSH Terms
Anoxia / physiopathology*
Arrhythmia, Sinus / physiopathology
Atropine / pharmacology
Middle Aged
Oxygen Consumption / physiology
Parasympatholytics / pharmacology
Pulmonary Gas Exchange / physiology*
Respiratory Mechanics / drug effects,  physiology
Tidal Volume / physiology
Vagus Nerve / drug effects,  physiology*
Reg. No./Substance:
0/Parasympatholytics; 51-55-8/Atropine
Comment In:
Exp Physiol. 2008 Apr;93(4):513-4; author reply 515   [PMID:  18344262 ]

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