The Relation of Fat-free Mass to Maximum Exercise Performance in Patients with Chronic Obstructive Pulmonary Disease

Abstract

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 and body composition, including fat mass (FM) and fat-free mass (FFM) assessed by bioelectrical impedance analysis (BIA). Exercise performance was evaluated by maximum oxygen uptake (Vo _2max) on a cycle ergometer. A total of 50 patients (FEV₁= 0.98 L) was divided randomly into either a study group (group A, n= 25) or validation group (group B, n= 25). Stepwise regression analysis was performed in group A to determine the best predictors of Vo _2max from measurements of pulmonary function and nutritional status. Stepwise regression analysis revealed that Vo _2max was predicted best by the following equation in group A: Vo _2max (mL/min) = 10.223 × FFM (kg) + 4.188 × MVV (L/min) + 9.952 × DL_co (mL/min/mmHg) − 127.9 (r= 0.84, p < 0.001). This equation was then cross-validated in group B: Measured Vo _2max (mL/min) = 1.554 × Predicted Vo _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 pulmonary function parameters, in patients with COPD.