The relation of fat-free mass to maximum exercise performance in patients with chronic obstructive pulmonary disease

To assess the factors determining maximum exercise performance in patients with chronic obstructive pulmonary disease (COPD), we examined nutritional status with special reference to body composition and pulmonary function in 50 stable COPD patients. Nutritional status was evaluated by body weight a nd body composition, including fat mass (FM) and fat-free mass (FFM) assess ed by bioelectrical impedance analysis (BIA). Exercise performance was eval uated by maximum oxygen uptake ((V) over dot O-2max) on a cycle ergometer. A total of 50 patients (FEV1 = 0.98 L) was divided randomly into either a s tudy group (group A, n = 25) or validation group (group B, n = 25). Stepwis e regression analysis was performed in group A to determine the best predic tors of ire,,, from measurements of pulmonary function and nutritional stat us. Stepwise regression analysis revealed that (V) over dot O-2max was pred icted best by the following equation in group A: (V) over dot O-2max (mL/mi n) = 10.223 x FFM (kg) + 4.188 x MVV (L/min) + 9.952 x DLco (mL/min/mmHg) - 127.9 (r = 0.84, p < 0.001). This equation was then cross-validated in gro up B: Measured (V) over dot O-2max (mL/min) = 1.554 x Predicted (V) over do t O-2max (mL/min) - 324.0 (r = 0.87, p < 0.001). We conclude that FFM is an important factor in determining maximum exercise performance, along with p ulmonary function parameters, in patients with COPD.