Document Detail


Voluntary versus reflex regulation of maximal exercise flow: volume loops.
MedLine Citation:
PMID:  2912335     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We determined the efficiency with which maximal exercise ventilatory output could be mimicked voluntarily. Five normal subjects exercised to maximal volitional effort and flow:volume and pressure:volume loops, and end-expiratory lung volume (EELV) and breathing pattern were measured. All subjects increased expiratory flow rate and reduced EELV sufficiently so that the forced vital capacity loop was approximated during at least some portion of expiration, but the generation of pleural pressure remained effective, i.e., equal to or only slightly in excess of that required to produce maximal expiratory flow (Pmax). Subsequently, while at rest, subjects used visual feedback and were able to closely mimic the flow:volume, EELV, and breath-timing achieved in maximal exercise; however: (1) expiratory pressures were excessive and usually exceeded average Pmax; (2) abdominal expiratory muscle activity was increased, as indicated by positive shifts in expiratory gastric pressure; and (3) total ventilatory work was increased 15 to 40% greater than that achieved in maximal exercise. Maximal voluntary efforts (MVV) caused EELV to increase and ventilatory work was increased 20 to 300% greater than during maximal exercise. We conclude that accurate determination of maximal effective ventilatory output available for maximal exercise or precise quantitation of the metabolic cost of producing maximal exercise ventilation requires replication of the pressure:volume, breath-timing, and EELV characteristics achieved in maximal exercise.
Authors:
J V Klas; J A Dempsey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American review of respiratory disease     Volume:  139     ISSN:  0003-0805     ISO Abbreviation:  Am. Rev. Respir. Dis.     Publication Date:  1989 Jan 
Date Detail:
Created Date:  1989-02-15     Completed Date:  1989-02-15     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370523     Medline TA:  Am Rev Respir Dis     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  150-6     Citation Subset:  AIM; IM    
Affiliation:
John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison.
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MeSH Terms
Descriptor/Qualifier:
Adult
Humans
Lung Volume Measurements*
Male
Maximal Voluntary Ventilation
Middle Aged
Physical Exertion*
Pulmonary Ventilation*
Reflex / physiology*
Work of Breathing

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


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