Associations of Exercise Tolerance and Clinical Parameters in Japanese Patients With Chronic Obstructive Pulmonary Disease: Impact of Skeletal Muscle

Background: Decreasing exercise tolerance is one of the key features related to a poor prognosis in patients with chronic obstructive pulmonary disease (COPD). Cardiopulmonary exercise testing (CPET) is useful for evaluating exercise tolerance. The present study was performed to clarify the correlation between exercise tolerance and clinical parameters, focusing especially on the cross-sectional area (CSA) of skeletal muscle. Methods: The present study retrospectively investigated 69 patients with COPD who underwent CPET. The correlations between oxygen uptake (⩒O 2 ) at peak exercise and clinical parameters of COPD, including skeletal muscle area measured using single-section axial computed tomography (CT), were evaluated. Results: The COPD assessment test score (ρ = -0.35, p = 0.02) and the CSA of the pectoralis muscles (ρ = 0.32, p = 0.02) were weakly correlated with V̇ O2 at peak exercise. In addition, forced expiratory volume in one second (FEV 1 ) (ρ = 0.39, p = 0.0009), FEV 1 /forced vital capacity (ρ = 0.33, p = 0.006), and the CSA of the erector spinae muscles (ρ = 0.34, p = 0.009) were correlated with ⩒ O2 at peak exercise. Conclusions: Decreased FEV 1 and loss of skeletal muscles, especially anti-gravity muscles, are correlated with a low level of exercise tolerance in COPD patients.