Skeletal muscle dysfunction in chronic obstructive pulmonary disease

Abstract

Intolerance to exercise in COPD patients has recently drawn increased attention, as muscular changes have been suggested to be the main factor responsible for the physical impairment. In addition to deconditioning related to physical inactivity, there are evidences of skeletal muscle changes in these patients. This article briefly reviews the skeletal muscle dysfunction in patients with COPD, underlining muscular functional, structural, and bioenergetic changes. Loss of muscle strength occurs mainly in lower limbs; muscle strength remains near to normal in upper limbs probably due to daily-life activities being performed by the upper body. Some patients with COPD present reduced arm and leg muscle crossectional area. There are evidences that oxidative and phosphocreatine capacity is reduced with normal glicolitic enzymes concentration, resulting in poor aerobic capacity. Malnutrition, miopaty caused by chronic use of corticosteroids, reduced anabolic hormones, deconditioning, reduced aminoacids metabolism, local or systemic inflammation, and oxidative stress, may contribute to the pathogenesis of skeletal muscle dysfunction in COPD. The decisive factors of this dysfunction are not still totally explained. Strategies as exercise, neuromuscular electrical stimulation, supplementation with anabolic agents and creatine, and antioxidant therapy, are rationale for the muscle abnormalities management.