Pulmonary rehabilitation (PR) improves outcomes in patients with chronic obstructive pulmonary disease (COPD). Optimal assessment includes cardiopulmonary exercise testing (CPET), but consultations are limited. Field tests could be used to individualize PR instead of CPET. The six-minute stepper test (6MST) is easy to set up and its sensitivity and reproducibility have previously been reported in patients with COPD. The aim of this study was to develop a prediction equation to set intensity in patients attending PR, based on the 6MST. The following relationships were analyzed: mean heart rate (HR) during the first (HR1-3) and last (HR4-6) 3 minutes of the 6MST and HR at the ventilatory threshold (HRvt) from CPET; step count at the end of the 6MST and workload at the Ventilatory threshold (VT) (Wvt); and forced expiratory volume in 1 second and step count during the 6MST. This retrospective study included patients with COPD referred for PR who underwent CPET, pulmonary function evaluations and the 6MST. Twenty-four patients were included. Prediction equations were HRvt = 0.7887 × HR1-3 + 20.83 and HRvt = 0.6180 × HR4-6 + 30.77. There was a strong correlation between HR1-3 and HR4-6 and HRvt (r = 0.69, p < 0.001 and r = 0.57, p < 0.01 respectively). A significant correlation was also found between step count and LogWvt (r = 0.63, p < 0.01). The prediction equation was LogWvt = 0.001722 × step count + 1.248. The 6MST could be used to individualize aerobic training in patients with COPD. Further prospective studies are needed to confirm these results.
Keywords: COPD; Cardiopulmonary exercise testing; field test; pulmonary rehabilitation; six-minute stepper test.