Pulmonary Diffusing Capacity For Nitric Oxide During Exercise In Morbid Obesity

Morbidly obese individuals may have altered pulmonary diffusion during exercise. The purpose of this study was to examine pulmonary diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) during exercise in these subjects. Ten morbidly obese subjects (age = 38 +/- 9 years, BMI = 47 +/- 7 kg/m(2), peak oxygen consumption or (V) over dotO(2peak) = 2.4 +/- 0.4 l/min) and nine nonobese controls (age = 41 +/- 9 years, BMI = 23 +/- 2 kg/m(2), (V) over dotO(2peak) = 2.6 +/- 0.9 l/min) participated in two sessions: the first measured resting (V) over dotO(2) and (V) over dotO(2peak) for determination of wattage equating to 40, 75, and 90% oxygen uptake reserve ((V) over dotO(2)R). The second session measured pulmonary diffusion from single- breath maneuvers of 5 s each, as well as heart rate (HR) and (V) over dotO(2) over three workloads. DLNO, DLCO, and pulmonary capillary blood volume were larger in obese compared to nonobese groups (P <= 0.06) only when expressed relative to alveolar volume (VA). The slope between (V) over dotO(2) and all measures of pulmonary diffusion, whether or not expressed to VA, were not different between groups (P > 0.10). The morbidly obese have increased pulmonary diffusion per unit increase in VA compared with nonobese controls which may be due to a lower rise in VA per unit increase in (V) over dotO(2) in the obese during exercise.