Performance of a maximum cardiopulmonary stress test is perhaps one of the most informative tests we have in the armamentarium of the pulmonary function laboratory. Yet, the results generated from such a test are easily the most difficult set of results one has to interpret. The reasons for this are several. First, the response of the body to muscular exercise is in itself complex,1
and, second, the number of variables or end points measured are numerous. But last, the principal difficulty is that the integration of the complex response, the number of variables, and the clinical situation try even the most experienced practitioner. As a result, this exceptionally useful endeavor is misunderstood and accordingly underutilized.