ABSTRACT
The conduct of a standard clinical cardiopulmonary exercise test (CPET) involves acquisition of continuous measurements of metabolic, cardiovascular and respiratory parameters over the course of an 8–15 minute effort, where exercise progresses incrementally from minimal movement to a maximal symptom-limited effort. The measurements of ventilation, oxygen consumption, carbon dioxide output, electrocardiogram, and oxygen saturation are acquired while the subject is exercising on a treadmill or a cycle ergometer. The standard exercise protocol for all CPETs has two defining characteristics: first, a progressive work test requires the subject to gradually transition exercise from minimal exertion to a symptom-limited maximal effort over 8–15 minutes; second, that exercise effort is performed on a cycle ergometer or a treadmill, exercise modes that recruit over 50% of a subject's total muscle mass. Given those two test characteristics, the maximal oxygen uptake attained by a normal subject is determined by the maximal cardiac output rather than muscle strength or maximal respiratory capacity. However, for patients presenting with exercise limitation, organ system limitations may arise from cardiac, respiratory, or metabolic abnormalities, and hence, understanding the normal CPET responses for all three systems is a necessary first step before considering the influence of disease on exercise limitation.
