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Relation between Pulmonary Gas Exchange and Closing Volume before and after Substantial Weight Loss in Obese Subjects

1974; BMJ; Volume: 3; Issue: 5927 Linguagem: Inglês

10.1136/bmj.3.5927.391

0959-8138

M. J. B. Farebrother, G. J. R. McHardy, James Munro,

Respiratory Support and Mechanisms

Relations between expiratory reserve volume (ERV), closing volume (CV) as a percentage of vital capacity (CV/VC%), and pulmonary gas exchange have been investigated in the sitting and supine postures in eight severely obese subjects before and after substantial weight loss. CV/VC% exceeded predicted values but did not change with posture or weight loss; the increase could have been owing to the smoking habits of the subjects. Arterial oxygen pressure (PaO 2 ) was significantly less in the supine than in the sitting posture and improved after weight loss in six subjects. The reduction in PaO 2 was correlated with the extent to which dependent airways were closed within the range of tidal breathing, shown by increasing negativity of ERV-CV as a percentage of VC. A good correlation was also found between PaO 2 and ERV, an easier measurement for routine use. Improvement of pulmonary gas exchange occurred only in those patients who lost weight to within 30% in excess of ideal.