Cardiopulmonary exercise test to predict pulmonary rehabilitation outcome in chronic obstructive pulmonary disease (COPD)

Background: there are not robust predictors of a pulmonary rehabilitation program (PRP) outcome. AIM: to evaluate if the main exercise-limiting factor, derived from a cardiopulmonary exercise test (CPET), can predict PRP outcome in patients affected by COPD. METHODS: CPETs of 64 COPD patients (mean FEV1 1.38 ± 0.44 L, 57.3 ± 18.7% pred.) have been reviewed, identifying 3 groups, according to the main limiting factor: group 1 ventilatory limit (N=32); group 2 muscular limit (N=14); group 3 ventilatory + muscular limit (N=18). We compared baseline characteristics (including BODE index) of the 3 groups; then, we analyzed the main outcomes of a PRP within each group: modified Medical Research Council (mMRC) scale, maximum load achieved in CPET, endurance time for upper (ETU) and lower limbs (ETL), 6-minute walk distance (6MWD) and Saint George's Respiratory Questionnaire (SGRQ). Results: patients belonging to group 2 had higher FEV1 and lower BODE index values than both group 1 and 3 (1.73 ± 0.38 L versus 1.32 ± 0.44 L and 1.24 ± 0.32 L respectively, for FEV1; 1.1 ± 1.2 versus 2.4 ± 1.7 and 2.9 ± 1.8 respectively, for BODE index; p<0.05). When evaluating the response to a PRP, patients in group 2 significantly improved only in 6MWD and ETL, while patients from groups 1 and 3 had significant benefits also in mMRC and SGRQ scores (figure 1). CONCLUSIONS: identifying the main exercise-limiting factor by using CPET does not distinguish COPD patients with regard to the main outcomes of a PRP. Baseline disease severity, evaluated by FEV1 and BODE index, seems to be more related to the response to a PRP.