The role of exercise testing in pulmonary diagnosis.

Exercise stresses the body's functional reserves that allow for the increased metabolic work and gas transport necessary for the efficient production of energy with physical activity or stress. Disease that reduces reserve in the gas transport organs will produce exertional symptoms not present at rest. Exercise testing has been well established in the evaluation of healthy persons and cardiac patients who are limited by cardiac or peripheral muscle function. For patients with lung disease, however, whose exercise performance is limited by reduced ventilatory capacity and disordered gas exchange, principles of exercise testing (and training) are different. In the evaluation of pulmonary patients, exercise testing can be used to measure exercise tolerance, assess the limitation to exercise in patients with unexplained dyspnea, evaluate patients for respiratory disability, assess blood gas changes with exercise, and detect exercise-induced asthma. Nevertheless, our understanding of the role of exercise in pulmonary diagnosis is at an early stage of development and much needs to be learned about the practical applications of exercise testing in the diagnosis, staging, and serial evaluation of pulmonary diseases.