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Cardiopulmonary exercise testing in differential diagnosis of dyspnea.

Dyspnea is a common exercise-induced symptom whose treatment is often improperly because the pathophysiology causing the exercise intolerance is not well understood. The most important requirement for exercise performance is transport of oxygen to support the bioenergetic processes in the muscle cells (including, of course, the heart) and elimination of the carbon dioxide formed as a product of exercise metabolism. Thus, appropriate cardiovascular and respiratory responses are required and the patient's symptoms should be sought for in terms of a gas exchange defect between the cells and environment. The defect may be in the lungs, heart, peripheral or pulmonary circulation, hemoglobin content and quality, metabolic disorders, psychogenic disorders or the muscles themselves, or there could be combinations of these defects. Cardiopulmonary exercise testing (CPET) allows the simultaneous study of the responses of the cardiovascular and ventilatory systems through the measurement and the integrative interpretation of a lot of parameters (1). ❑