Responsiveness of Various Exercise-Testing Protocols to Therapeutic Interventions in COPD

Abstract

Exercise intolerance is a key element in the pathophysiology and course of Chronic Obstructive Pulmonary Disease (COPD). As such, evaluating exercise tolerance has become an important part of the management of COPD. A wide variety of exercise-testing protocols is currently available, each protocol having its own strengths and weaknesses relative to their discriminative, methodological, and evaluative characteristics. This paper aims to review the responsiveness of several exercise-testing protocols used to evaluate the efficacy of pharmacological and nonpharmacological interventions to improve exercise tolerance in COPD. This will be done taking into account the minimally important difference, an important concept in the interpretation of the findings about responsiveness of exercise testing protocols. Among the currently available exercise-testing protocols (incremental, constant work rate, or self-paced), constant work rate exercise tests (cycle endurance test and endurance shuttle walking test) emerge as the most responsive ones for detecting and quantifying changes in exercise capacity after an intervention in COPD.

Figure 1

The impact of the power/duration relationship on the exercise endurance response following an intervention. With CP: critical power pre- or postintervention, considered as the asymptote of the power/duration relationship.

Figure 2

The impact of interventions on the exercise performance following testing methodologies in COPD population. With CPET: CardioPulmonary Exercise Test, ISWT: Incremental Shuttle Walking Test, CET: Cycle Endurance Test, ESWT: Endurance Shuttle Walking Test and 6MWT: 6 minute Walking Test. The percentages of improvement have been calculated, for each exercise protocol, by using the references quoted in the manuscript. All the others tests present in Table 1 (incremental treadmill exercise, constant work rate treadmill test, 3 min walk and step tests, and 6 minute stepper test) are not shown as there is nonexistent or insufficient data in the literature.