Reducing Dynamic Hyperinflation Through Breathing Retraining

Dynamic hyperinflation limits exercise tolerance in chronic obstructive pulmonary disease (COPD). To limit dynamic hyperinflation during exercise and thus improve exercise tolerance, we successfully developed a visual-auditory ventilation-feedback system. The system retrains patient's breathing pattern during exercise. The goal of the current proposal was to develop a user-friendly ventilation-feedback technique with a novel auditory feedback system. We reasoned that the proposed feedback system plus exercise training would be superior to exercise training alone while having the potential for an easier application into clinical practice. Hypotheses: The primary hypothesis is that the exercise duration of patients with moderate-to-severe COPD who successfully complete a 12-week program of breathing retraining plus exercise will be longer than that of patients who complete a 12-week program of treadmill exercise training alone. We also hypothesized that the primary predictor of improved exercise duration will be a reduction in dynamic hyperinflation and to a lesser extent, improvement in peripheral muscle function. Lastly, we hypothesize that dyspnea will be reduced in patients assigned to breathing retraining plus exercise when compared to exercise training alone. Methods: The proposed study was a randomized controlled clinical trial. 119 patients with moderate-to-severe COPD were randomized into breathing retraining plus exercise or exercise training alone. Both groups received 12-weeks of treadmill exercise training three times weekly. The breathing retraining plus exercise group also received auditory feedback to decrease respiratory rate and prolong exhalation. The goal of breathing retraining was to reduce exercise-induced dynamic hyperinflation. Follow-up testing was completed at 6, 12, and 24 weeks. Testing included a pulmonary function test, symptom-limited and constant workrate treadmill tests, six-minute walk, dyspnea measurements, testing of respiratory muscle strength and endurance, and quadriceps muscle endurance testing. Analysis: Measures of central tendency will be used to describe the study sample. A two-sample t-test ( = 0.05) was used to analyze changes from baseline to 12-weeks between the breathing retraining plus exercise group and exercise training alone group. In data analysis, intention-to-treat principles were used. Since several measures will be taken on each patient, mixed-models analysis will be used to compare changes over time between the two groups. Multiple regression analysis will be employed to determine the predictors of improved exercise performance.