A primer in cardiopulmonary exercise testing.

Cardiopulmonary exercise testing is useful in diagnosing the cause of exercise intolerance, in evaluating disability, and in defining the response to therapy. This testing modality is firmly founded on physiological principles. An efficient interaction of the body's systems is required to transport oxygen to the exercising muscles; failure of any system will yield characteristic changes in the ventilatory and gas exchange responses to exercise. An important measurement to make during exercise testing is the work rate at which oxygen transport begins to be inadequate. This work rate, known as the anaerobic threshold, is marked by a rise in blood lactate, and can be estimated noninvasively by examination of gas exchange responses during incremental exercise. In recent years, computerized systems and improved transducers have been introduced to facilitate breath-by-breath measurements during exercise testing. These systems also facilitate calibration, data presentation and report generation, making cardiopulmonary exercise testing a practical testing modality.