Document Detail

Uneven gas mixing during rebreathing assessed by simultaneously measuring dead space.
MedLine Citation:
PMID:  7153127     Owner:  NLM     Status:  MEDLINE    
To evaluate the rate of gas mixing in human lungs during rebreathing maneuvers used to measure pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc), we devised a method to determine the dead space during rebreathing (VRD). Required measurements are initial concentration of a foreign inert insoluble gas in the rebreathing bag, first mixed expired concentration, equilibrated concentration, volume inspired, and volume of the first expired breath. In subjects breathing rapidly at 30 breaths/min with inspired volumes in excess of 2 liters, VRD had values three or more times greater than the predicted anatomical dead space (VD). Breath holding after the first inspiration progressively diminished VRD so that after 10-15 s, it approximately equaled predicted VD. VRD measured with helium was smaller than VRD measured with sulfur hexafluoride. The reported degree of uneven ventilation from gravitational forces in normal humans can account for only about one-third of the difference between VRD and VD. These findings support the concept that mixing by diffusion between peripheral parallel airways is incomplete at normal breathing rates in humans and can result in errors as high as 25% in Vt and Qc.
M F Petrini; B T Peterson; R W Hyde; V Lam; M J Utell; M C Kallay
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of applied physiology: respiratory, environmental and exercise physiology     Volume:  53     ISSN:  0161-7567     ISO Abbreviation:  J Appl Physiol Respir Environ Exerc Physiol     Publication Date:  1982 Oct 
Date Detail:
Created Date:  1983-03-11     Completed Date:  1983-03-11     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  7801242     Medline TA:  J Appl Physiol Respir Environ Exerc Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  930-9     Citation Subset:  IM    
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MeSH Terms
Lung Volume Measurements
Models, Biological*
Respiratory Dead Space*
Respiratory Function Tests
Grant Support

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

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