Relation between changes of rib cage circumference and lung volume

Abstract

The static relation between lung volume and rib cage circumference has been determined over the vital capacity range in standing, sitting, and supine position. The average change of circumference over the expiratory reserve volume in the three positions was, respectively, 20.7, 30.5, and 26.5% of the total change. The patterns of the volume-circumference curves have been discussed in terms of the different mechanical features of the rib cage and of the abdomen-diaphragm according to the lung volume and the position. The volume displacement of the rib cage, DeltaVrc, and of the abdomen-diaphragm, DeltaV(ab + di), at different lung volumes, have been calculated by a geometrical approach. These results agreed with determinations of DeltaV(ab + di) over the tidal volume range obtained by immobilizing the rib cage at resting volume. Over the expiratory reserve volume, DeltaVrc, in the three positions, was, respectively, 18.9, 27.8, and 40.7% of the lung volume change; over the vital capacity, DeltaVrc was, respectively, 39.6, 37.1, and 41.1. effect of position and lung volume on the rib cage circumference; volume displacement of the rib cage and of the abdomen-diaphragm Submitted on September 14, 1964