Document Detail

Respiratory muscle coordination and diaphragm length during expiratory threshold loading.
MedLine Citation:
PMID:  2055836     Owner:  NLM     Status:  MEDLINE    
Active expiration is produced by the abdominal muscles and the rib cage expiratory muscles. We hypothesized that the relative contribution of these two groups to expiration would affect diaphragmatic length and, hence, influence the subsequent inspiration. To address this question we measured the respiratory muscle response to expiratory threshold loading in spontaneously breathing anesthetized dogs. Prevagotomy, the increase in lung volume (functional residual capacity) and decrease in initial resting length of the diaphragm were attenuated by greater than 50% of values predicted by the passive relationships. Diaphragmatic activation (electromyogram) increased and tidal volume (VT) was preserved. Postvagotomy, effective expiratory muscle recruitment was abolished. The triangularis sterni muscle remained active, and the increase in lung volume was attenuated by less than 15% of that predicted by the passive relationship. Diaphragmatic length was shorter than predicted. VT was not restored, even though costal diaphragmatic and parasternal intercostal electromyogram increased. During expiratory threshold loading with abdominal muscles resected and vagus intact, recruitment of the rib cage expiratory muscles produced a reduction in lung volume comparable with prevagotomy; however, diaphragmatic length decreased markedly. Both the rib cage and abdominal expiratory muscles may defend lung volume; however, their combined action is important to restore diaphragmatic initial length and, accordingly, to preserve VT.
J D Road; A M Leevers; E Goldman; A Grassino
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  70     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1991 Apr 
Date Detail:
Created Date:  1991-08-01     Completed Date:  1991-08-01     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:  1554-62     Citation Subset:  IM    
Department of Medicine, University of British Columbia, Vancouver, Canada.
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MeSH Terms
Diaphragm / physiology*
Functional Residual Capacity / physiology
Positive-Pressure Respiration
Respiratory Mechanics / physiology*
Respiratory Muscles / physiology*

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