{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,2]],"date-time":"2026-03-02T14:07:01Z","timestamp":1772460421470,"version":"3.50.1"},"reference-count":52,"publisher":"American Physiological Society","issue":"10","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2012,11,15]]},"abstract":"<jats:p>Muscle efficiency increases with fiber length and decreases with load. Diaphragm efficiency (Eff<jats:sub>di<\/jats:sub>) in healthy humans, measured as power output (\u1e86di) relative to the root mean square of diaphragm electromyogram (RMS<jats:sub>di<\/jats:sub>), increases with hyperpnea due to phasic activity of abdominal muscles acting to increase diaphragm length at end expiration ( L<jats:sub>di ee<\/jats:sub>) and decrease inspiratory load. In chronic obstructive pulmonary disease (COPD), hyperpnea may decrease Eff<jats:sub>di<\/jats:sub>if L<jats:sub>di ee<\/jats:sub>decreases and load increases due to airflow obstruction and dynamic hyperinflation. To examine this hypothesis, we measured Eff<jats:sub>di<\/jats:sub>in six COPD subjects (mean forced expiratory volume in 1 s: 54% predicted) when breathing air and at intervals during progressive hypercapnic hyperpnea. \u1e86di was measured as the product of mean inspiratory transdiaphragmatic pressure (\u0394Pdi<jats:sub>mean<\/jats:sub>), diaphragm tidal volume measured fluoroscopically, and 1\/inspiratory duration. Results were compared with those of six healthy subjects reported previously. In COPD, L<jats:sub>di ee<\/jats:sub>was normal when breathing air. \u0394Pdi<jats:sub>mean<\/jats:sub>and \u1e86di increased normally, and RMS<jats:sub>di<\/jats:sub>increased disproportionately ( P = 0.01) with hyperpnea, and, unlike health, inspiratory capacity (IC), L<jats:sub>di ee<\/jats:sub>, and Eff<jats:sub>di<\/jats:sub>did not increase. IC and L<jats:sub>di ee<\/jats:sub>were constant with hyperpnea because mean expiratory flow increased as expiratory duration decreased ( r<jats:sup>2<\/jats:sup>= 0.65), and because expiratory flow was terminated actively by the balance between expiratory and inspiratory muscle forces near end expiration, and these forces increased proportionately with hyperpnea ( r<jats:sup>2<\/jats:sup>= 0.49). At maximum ventilation, diaphragm radius of curvature at end inspiration increased in COPD ( P = 0.04) but not controls; diaphragm radius of curvature at end inspiration and ln(Eff<jats:sub>di<\/jats:sub>) were negatively correlated ( P = 0.01). Thus in COPD with modest airflow obstruction, Eff<jats:sub>di<\/jats:sub>did not increase normally with hyperpnea due to a constant L<jats:sub>di ee<\/jats:sub>and inspiratory flattening of the diaphragm.<\/jats:p>","DOI":"10.1152\/japplphysiol.01453.2011","type":"journal-article","created":{"date-parts":[[2012,9,21]],"date-time":"2012-09-21T05:20:42Z","timestamp":1348204842000},"page":"1567-1575","source":"Crossref","is-referenced-by-count":9,"title":["Diaphragm efficiency estimated as power output relative to activation in chronic obstructive pulmonary disease"],"prefix":"10.1152","volume":"113","author":[{"given":"Kevin E.","family":"Finucane","sequence":"first","affiliation":[{"name":"Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; and"},{"name":"West Australian Sleep Disorders Research Institute, Queen Elizabeth II Medical Centre, Perth, Western Australia, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bhajan","family":"Singh","sequence":"additional","affiliation":[{"name":"Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; and"},{"name":"West Australian Sleep Disorders Research Institute, Queen Elizabeth II Medical Centre, Perth, Western Australia, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1997.83.4.1256"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1991.70.1.223"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1993.sp019937"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1998.85.3.1123"},{"key":"B5","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1996.81.3.1434"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1995.79.3.975"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1974.36.4.475"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00865.2004"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1982.53.2.405"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00173.2009"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.01313.2010"},{"key":"B12","doi-asserted-by":"publisher","DOI":"10.1097\/00000542-200104000-00013"},{"key":"B13","first-page":"33","volume":"129","author":"Dodd DS","year":"1984","journal-title":"Am Rev Respir Dis"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1994.76.1.185"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.01165.2004"},{"key":"B16","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.91465.2008"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1136\/thx.52.4.355"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.1164\/rccm.200111-087OC"},{"key":"B19","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1976.41.5.739"},{"key":"B20","doi-asserted-by":"publisher","DOI":"10.1098\/rspb.1964.0004"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.00687.2001"},{"key":"B22","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00230.2002"},{"key":"B23","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1997.82.3.723"},{"key":"B24","doi-asserted-by":"crossref","first-page":"2491","DOI":"10.1242\/jeb.198.12.2491","volume":"198","author":"Layland J","year":"1995","journal-title":"J Exp Biol"},{"key":"B25","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1981.51.3.732"},{"key":"B26","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00116.2001"},{"key":"B27","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00008.2009"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1164\/ajrccm.161.1.9903010"},{"key":"B29","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1989.66.5.2045"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.1016\/S0034-5687(98)00024-3"},{"key":"B31","doi-asserted-by":"publisher","DOI":"10.1136\/thx.44.11.903"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1513\/pats.200508-093DO"},{"key":"B33","doi-asserted-by":"publisher","DOI":"10.1186\/1465-9921-9-12"},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.1164\/ajrccm.158.5.9802014"},{"key":"B35","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1999.87.5.1697"},{"key":"B36","doi-asserted-by":"publisher","DOI":"10.1164\/ajrccm\/141.2.281"},{"key":"B37","doi-asserted-by":"publisher","DOI":"10.1164\/ajrccm.152.3.7663810"},{"key":"B38","doi-asserted-by":"publisher","DOI":"10.1016\/S0021-9290(03)00081-2"},{"key":"B39","unstructured":"Shen K.Interactive Computerised Functional Analysis of Lateral Fluoroscopy Images to Quantify the Volume Displaced by Motion of the Diaphragm(Honours Thesis). 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