The Six-Minute Stepper Test Is Valid to Evaluate Functional Capacity in Hospitalized Patients With Exacerbated COPD

Abstract

Background: The six-minute stepper test (6MST) is a self-paced test considered a valid tool to assess functional capacity in stable COPD patients. However, a high floor effect, where a large proportion of participants reach the minimum score when using the measurement instrument, might compromise the test validity in the hospital setting. Therefore, this study aimed at verifying the concurrent validity of 6MST in hospitalized patients with acute exacerbation of COPD (AECOPD). Methods: A cross-sectional study was conducted in a tertiary hospital. Patients who were hospitalized due to AECOPD were considered for inclusion. On the first day, when patients reached minimum clinical criteria considered as the use of non-invasive ventilation less than 2 h for 6 h/period, dyspnea at rest less than 7 (very severe) on the modified Borg scale, a respiratory rate less than 25 breaths per minute, oxygen pulse saturation greater than 88% (considering use of supplemental oxygen) and absence of paradoxical breathing pattern, they underwent a lung function evaluation and answered three questionnaires: Chronic Respiratory Questionnaire (CRQ), Modified Medical Research Council Dyspnea Scale (MMRC), and COPD Assessment Test (CAT). Then, on two consecutive days, patients performed 6MST or six-minute walk test (6MWT), in random order. Each test was performed twice, and the best performance was recorded. Also, the patient’s severity was classified according to the BODE index. Inspiratory capacity measurements were performed before and after each test execution. Results: Sixteen patients (69.4 ± 11.4 years) with a mean FEV₁ of 49.4 ± 9.9% predicted were included (9 females). There was a strong correlation of the performance in 6MST (number of cycles) with 6MWT (distance walked in meters) in absolute values (r = 0.87, p < 0.001) as well as with the percentage of predicted normal 6MWT (r = 0.86, p < 0.001). There was a strong correlation between the performance in 6MST with the dynamic hyperinflation (r = 0.72, p = 0.002) and a moderate correlation between 6MST with the percentage of reduction of inspiratory capacity (r = 0.68, p = 0.004). We also identified that 6MST showed moderate negative correlations with CAT (r = −0.62, p = 0.01) and BODE index (r = −0.59, p = 0.01). Conclusion: It could be concluded that 6MST is valid for evaluating functional capacity in hospitalized patients with exacerbated COPD.