Interpreting the Incremental Cardiopulmonary Exercise Test

The incremental cardiopulmonary exercise test (CPET) is an increasingly used diagnostic method that serves to evaluate patients with chief complaint of dyspnea during exercise. Performing maximal symptom-limited CPET can show if the tested subject has a reduced exercise capacity and give clues to the mechanism of such exercise capacity reduction, cardiac, pulmonary, or pulmonary vascular source. In this review, it is suggested that the evaluation of the complex results of CPET should be performed by first determining if myocardial/circulatory insufficiency is present and second if there is gas exchange abnormality. By looking with scrutiny at the oxygen consumption (VO2) versus work rate plot, one can see if oxygen delivery is adequate or if it is hampered by abnormally reduced blood flow through skeletal muscle. Elevated ventilatory equivalent of carbon dioxide at the ventilatory threshold and or arterial oxygen desaturation during effort, strongly suggest gas exchange abnormalities. The absence of circulatory insufficiency and gas exchange abnormalities, almost always suggest normal response to effort or deconditioning whenever peak VO2 is below the maximal predicted value.