Effect of respiratory muscle endurance training in patients with COPD undergoing pulmonary rehabilitation.
BACKGROUND
Respiratory muscle endurance training (hyperpnea training) has been shown to have beneficial effects in patients with COPD.


STUDY OBJECTIVES
The purpose of this study was to determine whether hyperpnea training, when added to an endurance exercise training program, would lead to additional benefits compared with endurance training alone in patients with COPD.


SETTING AND PARTICIPANTS
Patients with COPD entering an 8-week outpatient pulmonary rehabilitation program. Fifteen patients (mean [+/- SE] FEV1, 45 +/- 6% predicted) were randomized to combined therapy, and 14 patients (mean FEV1, 44 +/- 4% predicted) were randomized to endurance training.


METHODS
Peak exercise capacity, exercise endurance time during constant workload cycle exercise, 6-min walk distance, quality of life as measured by the chronic respiratory questionnaire, respiratory muscle strength and endurance, and quadriceps fatigability were measured before and after endurance or combined training.


RESULTS
After rehabilitation, peak exercise capacity, exercise endurance time, 6-min walk distance, and quality of life all increased in both groups, but there was no significant difference in the extent of improvement between groups. Mean respiratory muscle endurance increased to a significantly greater extent in the combined therapy group (17.5 +/- 2.7 vs 8.5 +/- 2.5 min, respectively; p = 0.02). Respiratory muscle strength was significantly increased, and quadriceps fatigability was significantly reduced after rehabilitation in the combined therapy group but not in the endurance training group, but the difference between groups did not reach statistical significance.


CONCLUSION
The endurance of the respiratory muscles can be improved by specific training beyond that achieved by endurance training alone in patients with COPD. However, this improvement did not translate into additional improvement in quality of life or exercise performance.