Document Detail


Oxygen cost of breathing during fatiguing inspiratory resistive loads.
MedLine Citation:
PMID:  2745273     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
When a subject breathes against an inspiratory resistance, the inspiratory pressure, the inspiratory flow, and the lung volume at which the breathing task takes place all interact to determine the length of time the task can be sustained (Tlim). We hypothesized that the mechanism actually limiting tasks in which these parameters were varied involved the rate of energy utilization by the inspiratory muscles. To test this hypothesis, we studied four experienced normal subjects during fatiguing breathing tasks performed over a range of pressures and flows and at two different lung volumes. We assessed energy utilization by measuring the increment in the rate of whole body O2 consumption due to the breathing task (VO2 resp). Power and mean esophageal pressure correlated with Tlim but depended also on lung volume and inspiratory flow rate. In contrast, VO2 resp closely correlated with Tlim, and this relationship was not systematically altered by inspiratory flow or lung volume. The shape of the VO2 resp vs. Tlim curve was approximately hyperbolic, with high rates of VO2 resp associated with short endurance times and lower rates of VO2 resp approaching an asymptotic value at high Tlim. These findings are consistent with a mechanism whereby a critical rate of energy utilization determines the endurance of the inspiratory pump, and that rate varies with pressure, flow, and lung volume.
Authors:
F D McCool; G E Tzelepis; D E Leith; F G Hoppin
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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:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  66     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1989 May 
Date Detail:
Created Date:  1989-08-25     Completed Date:  1989-08-25     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2045-55     Citation Subset:  IM; S    
Affiliation:
Department of Medicine, Memorial Hospital of Rhode Island, Pawtucket 02860.
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MeSH Terms
Descriptor/Qualifier:
Esophagus / physiology
Humans
Inhalation*
Lung / physiology*
Lung Volume Measurements
Mathematics
Models, Theoretical
Oxygen Consumption
Pressure
Respiration*
Respiratory Muscles / physiology
Spirometry
Grant Support
ID/Acronym/Agency:
HL-34149/HL/NHLBI NIH HHS

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


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