The role of gas analysis with exercise testing

Assessment of exercise performance is an integral component of clinical evaluation. Currently, exercise capacity is judged by obtaining the history of distance traveled or steps climbed before the appearance of dyspnea, and assigning a New York Heart Association functional class, 14, to grade the dysfunction. This form of assessment is inherently subjective and influenced by both patient and physician bias. The conventional stress test that is limited to evaluation of angina also fails to reliably assess the exercise performance. Neither peak heart rate nor exercise duration consistently correlate with exercise capacity? The use of gas analysis with the stress testing, termed cardio-pulmonary exercise (CPX) testing, provides the much-needed objectivity. In addition to the parameters measured by conventional stress testing, e.g., heart rate, blood pressure, and electrocardiographic monitoring, CPX encompasses thorough breath-by-breath analysis of oxygen uptake (V02), carbon dioxide production (VCO?), and ventilation (VE) as well. This expansion of exercise testing constitutes comprehensive functional assessment that helps to quantitate and differentiate the disorders of such diverse organ systems as heart, lungs, blood, and vessels. A physician can use CPX to systematically address limiting symptoms and their origins, cardiac or ventilatory; objectively grade the severity of functional incapacity; determine the progressive nature of an illness; and access the response to medical or surgical management. This section reviews physiologic principles and methods, and clinical applications of CPX testing, with emphasis on its use in assessing functional capacity, distinguishing between primary cardiac versus ventilatory system limitation, assigning prognosis and preoperative risk, developing