The effect of breathing retraining using metronome-based acoustic feedback on exercise endurance in COPD: A randomized trial

Background: During exercise training patients with COPD can entrain their breathing pattern to visual feedback cues as to achieve a slower respiratory rate and prolong exhalation. The result is an improvement in exercise tolerance and a reduction in dynamic hyperinflation. Acoustic stimuli, including metronome-generated acoustic stimuli, can entrain human movements. Accordingly, we hypothesized that exercise duration and dynamic hyperinflation would be less after exercise-training plus breathing retraining using a metronome-based acoustic feedback system than after exercise-training alone. Methods: Of 205 patients with COPD (FEV1=44±16% predicted (±SD)) recruited, 119 were randomly assigned to exercise training plus breathing-retraining using acoustic feedback (n=58) or exercise training alone (n=61). Patients exercised on a treadmill thrice-weekly for twelve weeks. Before and at completion of training, patients underwent constant-load treadmill testing with inspiratory capacity measures every 2 minutes. Results: At completion of training, improvements in exercise duration in the breathing-retraining plus exercise training and exercise training alone groups were similar (p=0.35). At isotime, inspiratory capacity increased (less exercise-induced dynamic hyperinflation) by 3% (p=0.001) in the breathing-retraining plus exercise training group and remained unchanged in the exercise alone group. The between-group change in inspiratory capacity, however, was not significant (p=0.08). Conclusions: In patients with COPD, breathing-retraining using a metronome-based acoustic feedback did not result in improved exercise endurance or decreased dynamic hyperinflation when compared to exercise training alone.