{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T23:14:51Z","timestamp":1774566891784,"version":"3.50.1"},"reference-count":0,"publisher":"American Physiological Society","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[1993,6,1]]},"abstract":"<jats:p> 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) &gt; 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 &lt; 0.001) and degree of diaphragm flattening assessed from chest radiographs (r2 = 0.74, P &lt; 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\u20131640, 1983; T. Similowski et al. N. Engl. J. Med. 325: 917\u2013923, 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. <\/jats:p>","DOI":"10.1152\/jappl.1993.74.6.2750","type":"journal-article","created":{"date-parts":[[2017,12,22]],"date-time":"2017-12-22T00:48:51Z","timestamp":1513903731000},"page":"2750-2756","source":"Crossref","is-referenced-by-count":17,"title":["Oxygen cost of increasing tidal volume and diaphragm flattening in obstructive pulmonary disease"],"prefix":"10.1152","volume":"74","author":[{"given":"W. D.","family":"Pitcher","sequence":"first","affiliation":[{"name":"Pulmonary and Critical Care Medicine Division, University of Texas, Southwestern Medical Center, Dallas 75216."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H. S.","family":"Cunningham","sequence":"additional","affiliation":[{"name":"Pulmonary and Critical Care Medicine Division, University of Texas, Southwestern Medical Center, Dallas 75216."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","container-title":["Journal of Applied Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.physiology.org\/doi\/pdf\/10.1152\/jappl.1993.74.6.2750","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,9,8]],"date-time":"2019-09-08T16:37:33Z","timestamp":1567960653000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.physiology.org\/doi\/10.1152\/jappl.1993.74.6.2750"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1993,6,1]]},"references-count":0,"journal-issue":{"issue":"6","published-print":{"date-parts":[[1993,6,1]]}},"alternative-id":["10.1152\/jappl.1993.74.6.2750"],"URL":"https:\/\/doi.org\/10.1152\/jappl.1993.74.6.2750","relation":{},"ISSN":["8750-7587","1522-1601"],"issn-type":[{"value":"8750-7587","type":"print"},{"value":"1522-1601","type":"electronic"}],"subject":[],"published":{"date-parts":[[1993,6,1]]}}}