The Role of Gas Analysis and Cardiopulmonary Exercise Testing

Apart from the measurement of the vital signs, evaluation of exercise performance constitutes one of the most crucial parameters in the clinical assessment of a patient. Many different methods are currently employed by the health care providers in this regard, but most remain un-standardized and arbitrary. Generally, physicians depend on the clinical history and the information provided by the patients about their own ability to walk a certain distance or climb a certain number of steps. Physicians, then, assign the patients a “grade” by arbitrarily ascribing a New York Heart Association (NYHA) functional class, I–IV, to provide some semblance of objectivity to obtain a measure of their level of peak exercise ability. The information so obtained, however, still remains inherently subjective since it can be influenced by bias from both the patient and the physician. Furthermore, the exercise stress tests routinely performed for evaluation of chest pain do not adequately assess the exercise performance since the acquired parameters, such as “exercise duration” and “maximum heart rate achieved”, do not necessarily show concordance with exercise capacity [1]. Medical literature, on the other hand, has consistently shown that the “accurate level” of exercise performance is highly predictive of and correlates strongly with the occurrence of future adverse cardiovascular events. The need, therefore, for evaluation of exercise performance with greater objectivity and precision cannot be overstated. The use of gas analysis with stress testing, known as cardiopulmonary exercise (CPX) testing, is just such a test that can easily be performed in an outpatient setting by minor modifications to the regular stress testing assembly. CPX testing adequately provides the obviously much-needed precise and objective assessment of exercise performance. In addition to obtaining the electrocardiogram, heart rate, and blood pressure similar to a routine stress test, the CPX test also assesses breathby-breath analysis of ventilation (VE), oxygen uptake (VO2), and carbon dioxide production (VCO2) and provides a much more comprehensive evaluation of the functional ability of a patient. Such information not only helps prognosticate future