Exercising Your Patient: Which Test(s) and When?

Abstract

With the introduction of the stair climb test of surgical patients in the 1950s, the role of exercisebased 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.

Pulmonary Function Testing

“…In these circumstances, some form of exercise evaluation is required. 19 A number of exercise testing protocols have evolved, usually to answer a specific question regarding exercise intolerance. Stair climbing is a simple form of exercise dating back 50 years.…”

“…These include the FOT, 18 enhanced use of transcutaneous P O 2 and P CO 2 sensors (for adults as well as children), uptake of NO to measure D LNO (membrane transfer factor), 44 impedance cardiography to measure cardiac output, 19 and analysis of exhaled NO (F ENO ) to assess airway inflammation. 35 Some technologies are on the horizon that are "brand new" and may have a role in the PFT lab of the future.…”

Assessing Maximal Exercise Capacity: Peak Work or Peak Oxygen Consumption?

“…[1][2][3][4][5][6][7] Indeed, peak V O 2 is a robust predictor of outcomes in many cardiopulmonary diseases such as COPD, congestive heart failure, cystic fibrosis, and pulmonary hypertension. [1][2][3]8,9 However, we have observed that there are some patients who achieve higher percent-of-predicted peak work than percent-ofpredicted peak V O 2 , and vice versa. In these cases it is unclear whether to use peak work or peak V O 2 as the parameter by which to judge the patient's exercise capacity.…”

“…This is in accordance with the general concept of rating impairment versus disability, 34 wherein the former reflects physiological function, while the latter reflects the ability to perform work in the context of personal and environmental factors: a more global measure. It is important to emphasize, however, that peak V O 2 remains an important measure of cardiovascular conditioning, 35 preoperative risk in lung resection surgery, 36 and a predictor of future cardiopulmonary outcomes, [1][2][3]8,9 and such relationships have not been found for direct measures of work.…”

Which Pulmonary Function Tests Best Differentiate Between COPD Phenotypes?

“…However, among patients with COPD, the presence of a low D LCO warrants measurement of exercise O 2 , often in conjunction with a 6-min walk distance test. [23][24][25] Are Measurements of Hyperinflation Helpful?…”