The significance of peripheral skeletal muscle disease as a limiting factor in patients with COPD has been emphasized.1,4–6
In fact, some investigators have concluded that muscle dysfunction is seen in a considerable proportion of COPD patients and have suggested inactivity, acidosis, hypoxemia, chronic inflammation, malnutrition, coexisting heart disease, severe deconditioning, and medications (especially corticosteroids) as some of the proposed mechanisms. Controversy remains as to whether or not COPD is associated with a specific myopathic condition or whether peripheral muscle disorders are secondary to the consequences of COPD, resulting in malnutrition, chronic inflammation, or disuse. How often and how much peripheral muscle disorders affect function in COPD is a very important question. This is because we want to know whether the treatment of COPD should be directed only at the lungs, using bronchodilators, corticosteroids, oxygen, and smoking cessation, or whether therapy with exercise training, nutritional interventions, and anabolic agents would be of benefit. Furthermore, some investigators7
have found an association between reduced muscle mass and survival in COPD patients, independent of a reduction of FEV1.