| Oxygen cost of increasing tidal volume and diaphragm flattening in obstructive pulmonary disease. | |
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MedLine Citation:
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PMID: 8365977 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Hypercapnia is associated with a shallow breathing pattern in patients with severe chronic obstructive pulmonary disease (COPD). We sought to determine the oxygen cost of increasing tidal volume and to relate this to hypercapnia [arterial PCO2 (PaCO2) > or = 45 Torr] and diaphragm flattening. We studied 3 normal subjects and 12 patients with stable but comparably severe COPD (forced expired volume in 1 s 1.01 +/- 0.09 liters) who had baseline PaCO2 ranging from 36 to 56 Torr. Oxygen consumption was measured during the subject's native breathing pattern and then while tidal volume was increased by 20%; minute ventilation was held constant by proportionately slowing frequency. There was a significant oxygen cost of increasing tidal volume for hypercapnic patients (235 +/- 23 to 260 +/- 25 ml O2/min; P = 0.002); no significant oxygen cost was observed in normal or eucapnic patients. This oxygen cost was positively correlated to baseline PaCO2 (r2 = 0.88, P < 0.001) and degree of diaphragm flattening assessed from chest radiographs (r2 = 0.74, P < 0.05). Although others have shown that force generation is preserved during chronic hyperinflation (G. A. Farkas and C. Roussos. J. Appl. Physiol. 54: 1635-1640, 1983; T. Similowski et al. N. Engl. J. Med. 325: 917-923, 1991), we conclude that diaphragm flattening produces mechanical inefficiency that may contribute to limiting the effective operating range of the respiratory muscles during tidal breathing. |
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Authors:
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W D Pitcher; H S Cunningham |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 74 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 1993 Jun |
Date Detail:
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Created Date: 1993-10-01 Completed Date: 1993-10-01 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 2750-6 Citation Subset: IM |
Affiliation:
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Pulmonary and Critical Care Medicine Division, University of Texas, Southwestern Medical Center, Dallas 75216. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Aged Diaphragm / physiopathology* Humans Hypercapnia / physiopathology Lung Diseases, Obstructive / physiopathology* Male Middle Aged Oxygen Consumption / physiology* Respiratory Mechanics / physiology Tidal Volume / physiology* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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