Effect of Immersion on RV in Young Women: Implications for Measurement of Body Density

Abstract

The effect of immersion to the chin on the residual volume (RV), vital capacity (VC), functional residual capacity (FRO, and expiratory reserve volume (ERV) of 27 normal females, mean age 20.7 years, was studied. Mean determinations decreased (P < .01) for all measured lung volumes from the corresponding measurement with the subjects in air (RV 17.4%, VC 12.1%, FRC 46.9%, ERV 70.3%). In addition, the effect of the decreased RV on body density (Db) and percent fat (% fat) determinations were also examined. The mean reduction in RV of 17.4% (195ml) corresponded to a mean relative error of only 0.35% in the Db measure. It is recommended that when measuring RV to later determine Db by hydrostatic weighing, the determination be made with subject in air. This procedure will allow for greater ease in measurement for both the subject and researcher with no loss in physiologic accuracy.

Key words

lung volumes - functional residual capacity - residual volume - hydrostatic weighing