Document Detail

Changes in alveolar mixing efficiency during exercise.
MedLine Citation:
PMID:  1788489     Owner:  NLM     Status:  MEDLINE    
The increased alveolar-arterial oxygen gradient (A-aDO2) occurring at higher levels of exercise may reflect impaired gas mixing. This latter function was investigated using the multiple breath nitrogen washout technique in 30 physical training students (15 M, 15 F). They were examined at rest and at work loads of 50, 100 and 150 W, using a cycle ergometer. Measurements included tidal volume (VT), serial dead space (VDS) and from the washout alveolar dead space (VDA), lung volume as the end-expiratory volume (EEV) and alveolar gas mixing efficiency (AME). There were expected rises in mean V1 from 641 +/- 161 to 1650 +/- 248 ml and in minute ventilation (VE) from 11.1 +/- 3.1 to 47.1 +/- 5.2 L.min-1 at 150 W but EEV changed only slightly from 2555 +/-559 to 2321 +/- 585 ml at the same workload. Despite an increase in VDS from 156 +/- 33 to 258 +/- 35 ml and VDA from 139 +/- 40 to 305 +/- 73 ml, AME rose significantly with exercise from 72.5 +/- 5.0 to 78.3 +/- 3.3%. These results are discussed in relation to the morphology of the lung, and the stationary interface theory. They suggest that gas mixing improves at the onset of exercise only, so that the widening in A-aDO2 with increasing levels of exercise cannot be explained by impaired mixing efficiency alone, and is probably due to other factors such as critically rapid transit time of blood through the pulmonary capillaries as cardiac output increases.
T Hale; W J Kox
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Respiration physiology     Volume:  86     ISSN:  0034-5687     ISO Abbreviation:  Respir Physiol     Publication Date:  1991 Dec 
Date Detail:
Created Date:  1992-03-23     Completed Date:  1992-03-23     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0047142     Medline TA:  Respir Physiol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  283-91     Citation Subset:  IM; S    
Department of Anaesthesia, Charing Cross Hospital, London, U.K.
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MeSH Terms
Exercise / physiology*
Pulmonary Alveoli / physiology*
Pulmonary Gas Exchange / physiology*
Respiratory Dead Space
Tidal Volume

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

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