Alveolar-arterial gas exchange during muscular work in obesity

Abstract

Various aspects of alveolar-arterial gas exchange in 13 obese (110-190 kg, 31-50% body fat) and 13 normal, healthy, sedentary young adults were compared at rest, at moderate and severe levels of steady-state work at similar metabolic rates, and at "maximum" work intensities. The majority of obese subjects were capable of meeting the rising requirement for CO2 elimination during moderate, severe, and all-out work. In only 1 of 13 cases was the work of breathing elevated[long dash]or sensitivity to respiratory stimuli reduced[long dash]to such an extent that pulmonary ventilation was depressed and hypercapnia resulted. Alveolar-to-arterial O2 transport was limited in varying degrees, and measured values of steady-state DLCO were consistently reduced in the majority of obese subjects during moderate and severe levels of work. It was proposed that the basic disorder in O2 and CO exchange in obesity was one of nonuniform ventilation distribution with reduction in the effective alveolar-capillary interface.