Abstract
BackgroundAlthough the endurance shuttle walk test (ESWT) has proven to be responsive to change in exercise capacity after pulmonary rehabilitation (PR) for COPD, the minimally important difference (MID) has not yet been established. We aimed to establish the MID of the ESWT in patients with severe COPD and chronic hypercapnic respiratory failure following PR.MethodsData were derived from a randomized controlled trial, investigating the value of noninvasive positive pressure ventilation added to PR. Fifty-five patients with stable COPD, GOLD stage IV, with chronic respiratory failure were included (mean (SD) FEV1 31.1 (12.0) % pred, age 62 (9) y). MID estimates of the ESWT in seconds, percentage and meters change were calculated with anchor based and distribution based methods. Six minute walking distance (6MWD), peak work rate on bicycle ergometry (Wpeak) and Chronic Respiratory Questionnaire (CRQ) were used as anchors and Cohen’s effect size was used as distribution based method.ResultsThe estimated MID of the ESWT with the different anchors ranged from 186–199 s, 76–82% and 154–164 m. Using the distribution based method the MID was 144 s, 61% and 137 m.ConclusionsEstimates of the MID for the ESWT after PR showed only small differences using different anchors in patients with COPD and chronic respiratory failure. Therefore we recommend using a range of 186–199 s, 76–82% or 154–164 m as MID of the ESWT in COPD patients with chronic respiratory failure. Further research in larger populations should elucidate whether this cut-off value is also valid in other COPD populations and with other interventions.Trial registrationClinicalTrials.Gov (ID NCT00135538).Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-015-0182-x) contains supplementary material, which is available to authorized users.
Highlights
The endurance shuttle walk test (ESWT) has proven to be responsive to change in exercise capacity after pulmonary rehabilitation (PR) for Chronic Obstructive Pulmonary Disease (COPD), the minimally important difference (MID) has not yet been established
Patients with severe Chronic Obstructive Pulmonary Disease (COPD) have an impaired exercise capacity, which is frequently associated with lower physical activity level [1] and, importantly, with lower quality of life [2,3] and higher mortality [4]
Using three different anchors we found MID estimates ranging from 186–199 s, 76–82% and 154– 164 m
Summary
The endurance shuttle walk test (ESWT) has proven to be responsive to change in exercise capacity after pulmonary rehabilitation (PR) for COPD, the minimally important difference (MID) has not yet been established. Maximal exercise capacity is commonly assessed with incremental cycle ergometry or treadmill walking, but these tests are not very responsive to interventions such as medication [7] or exercise training [8]. Field walking tests, such as the six-minute walking distance (6MWD) and endurance shuttle walk test (ESWT), might better reflect quality of life and activities of daily living, and might be more relevant measurements in patients with severe COPD. The ESWT is less affected by motivation and pacing ability of the patient than the 6MWD because gate speed is imposed [13,14]
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