Clinical applications of cardiopulmonary exercise testing.

Noninvasive measurement of metabolic and cardiorespiratory variables can be readily obtained using computerized systems as part of exercise testing of patients on a cycle ergometer or treadmill. The major indications for CPEX are: to assess exercise-related symptoms, especially dyspnea and chest pain; to measure exercise capacity including acceptability of patients with end-stage heart disease for cardiac transplantation; to evaluate for impairment/disability; to establish safety and guidelines for exercise training; and to assess response to specific therapy. As most patients with chronic cardiorespiratory disorders reduce their activities and consequently become deconditioned, CPEX should be considered as part of the initial evaluation. The results of CPEX should enable the physician to understand the reason(s) for the patient's exercise limitation and usually support the recommendation that the patient participate in a reconditioning or rehabilitation program. Should expired gases be measured as routine for all exercise tests? The use of CPEX depends on the clinical question. If the question is, "Does the patient have ischemic heart disease?", then a standard "cardiac stress test" is adequate. If the clinical question is, "Why is the individual limited in exercise ability?" or "Why is a patient breathless with activities?", then comprehensive CPEX is indicated. One important issue relating to CPEX is cost effectiveness. Do the results of CPEX justify the expense? There are little if any data to answer this question. However, if CPEX can establish a specific diagnosis, exclude significant heart disease, estimate work capacity, and/or provide guidelines for prescription of exercise intensity, this information may be invaluable to the individual patient and to the health-care provider. It is possible that CPEX may answer a specific clinical question and thereby actually eliminate the need and reduce the cost of additional expensive diagnostic tests. A prospective assessment of the cost effectiveness of CPEX will be important for select clinical problems.