todays practice of cardiopulmonary medicine Concepts and Applications of Cardiopulmonary Exercise Testing *

H P he development of rapidly responding oxygen and carbon dioxide analyzers has led to a broader application of oxygen and carbon dioxide monitoring in clinical practice. This is particularly the case in the exercise laboratory, where oxygen uptake (Vo z ) and carbon dioxide production (Vco 2 ) can be easily monitored using either intermittent or breath-by-breath sampling techniques. We term the monitoring of these respiratory gases during various forms of muscular work as cardiopulmonary exercise (CPX) testing to distinguish it from traditional stress testing and to indicate that heart and lung function can be assessed simultaneously Hence, CPX testing makes it possible to assess the exercise response in patients with cardiovascular or respiratory disease, or in patients with coexistent heart and lung disease. Clinically relevant issues that heretofore could not be adequately addressed from the response in exercise heart rate or blood pressure alone, can now be examined in objective and quantitative terms. Specifically, one can determine aerobic capacity, anaerobic threshold, the ventilatory response, and the appearance of hypoxemia and use this information to address the nature and severity of disease, its progression over time, and its response to therapy 1 The CPX testing is therefore gaining in popularity while an increasing number of clinical applications are being identified to ensure its role as a valuable clinical tool in the future. The purpose of this brief review is to provide an overview of physiologic concepts relevant to CPX testing. We then will discuss our approach to using CPX testing in the assessment of common clinical problems that include evaluating the severity of cardiac or circulatory failure, identifying the cause of exertional dyspnea, and finally monitoring the response to medical therapy in patients with chronic cardiac failure. For a more detailed discussion of these topics,