Exercise testing in the evaluation of cardiopulmonary disease. A cardiologist's point of view

The heart and lungs work in synchrony as a metabolic unit to transport the respiratory gases, O2 and CO2, between the atmosphere and the metabolizing tissues. This article reviews the physiologic behavior of the cardiopulmonary unit; in particular it focuses on the physiologic stress of exercise and the utility of monitoring respiratory gas exchange during exercise to assess the nature of cardiovascular disease and its severity.