Pathophysiology of dyspnea in COPD.

Dyspnea refers to the sensation of breathlessness, shortness of breath, or difficulty breathing that is commonly observed in patients with respiratory and cardiac disease. In the United States alone, dyspnea is reported in up to 4 million all-cause emergency room visits annually. Dyspnea can be a symptom of several different underlying physical conditions, typically involving the lung and heart. Indeed, it is an important symptom in chronic obstructive pulmonary disease (COPD), where it is associated with limited physical activity, increased anxiety and depression, decreased health-related quality of life (HRQoL), and reduced survival. Currently there is no single physiological correlate that will accurately predict dyspnea, particularly because the mechanisms that contribute to respiratory discomfort can vary between diseases and between individuals experiencing breathlessness who have been diagnosed with the same disease. Therefore, various subjective clinical and psychophysical scales and questionnaires are typically used to measure or predict dyspnea. It is the goal of this review to discuss the pathophysiological mechanisms leading to dyspnea, particularly those associated with COPD, the physical and psychological impact on patients, assessment approaches, and modalities currently used to treat it.