Mechanisms of non-pharmacologic adjunct therapies used during exercise in COPD

Individuals with chronic obstructive pulmonary disease (COPD) are often limited in their ability to perform exercise due to a heightened sense of dyspnea and/or the occurrence of leg fatigue associated with a reduced ventilatory capacity and peripheral skeletal muscle dysfunction, respectively. Pulmonary rehabilitation programs have been shown to improve exercise tolerance and health related quality of life. Additional therapeutic approaches such as non-invasive ventilatory support (NIVS), heliox (He-O(2)) and supplemental oxygen have been used as non-pharmacologic adjuncts to exercise to enhance the ability of patients with COPD to exercise at a higher exercise-intensity and thus improve the physiological benefits of exercise. The purpose of the current review is to examine the pathophysiology of exercise limitation in COPD and to explore the physiological mechanisms underlying the effect of the adjunct therapies on exercise in patients with COPD. This review indicates that strategies that aim to unload the respiratory muscles and enhance oxygen saturation during exercise alleviate exercise limiting factors and improve exercise performance in patients with COPD. However, available data shows significant variability in the effectiveness across patients. Further research is needed to identify the most appropriate candidates for these forms of therapies.