Exercising your patient: which test(s) and when?

With the introduction of the stair climb test of surgical patients in the 1950s, the role of exercise-based testing as a useful diagnostic tool and an adjunct to conventional cardiopulmonary testing was established. Since then, we have witnessed a rapid development of numerous tests, varying in their protocols and clinical applications. The relatively simple "field tests" (shuttle walks, stair climb, 6-minute walk test) require minimal equipment and technical support, and so are generally available to physicians and patients. At the other end of the spectrum is the cardiopulmonary exercise test (CPET), more complex in its equipment requirements, technical support, and with an often complex interpretive strategy. The 6-minute walk test (6MWT), in particular, has evolved into a versatile study with diagnostic utility in many disorders, including COPD, pulmonary hypertension, interstitial lung disease, congestive heart failure, and in the pre-surgical evaluation of patients, among others. With the added dimensions of optional O(2) saturation monitoring and calculated post-exercise heart rate recovery, the 6MWT is providing important clinical information well beyond the measure of distance walked. Is it sufficiently robust and informative to replace the more demanding and less available CPET? In many instances, the clinical applications are overlapping, with the 6MWT functioning as an adequate surrogate. However, in the initial evaluation of unexplained dyspnea, in formal evaluation of impairment and disability, in detailed evaluation of congestive heart failure, and in the selected lung cancer patient prior to resection, CPET remains superior. Investigations of portable metabolic and cardiovascular monitoring devices aiming to enhance the diagnostic capabilities of 6MWT may further narrow or close the remaining gap between these two exercise studies.