BACKGROUND: Breathing-retraining and helium-oxygen (heliox) have been used to improve exercise tolerance in COPD. We hypothesized that, in patients with COPD, exercise duration after exercise-training plus breathing-retraining and oxygen would be longer than after exercise-training plus heliox or after exercise-training plus oxygen alone. We also explored the short-term maintenance of gains in exercise duration after using each technique. METHODS: Of 192 COPD patients recruited, 103 were randomly assigned to exercise-training plus heliox (n = 33), exercise-training plus breathing-retraining and oxygen (n = 35) and exercise-training and oxygen (n = 35). FiO2 was 0.30 during testing and training in all groups. Patients exercised on a treadmill thrice-weekly for eight weeks. Before, at completion of training, and six-weeks later, patients underwent constant-load treadmill testing. RESULTS: At completion of training, improvements in exercise duration in the heliox and breathing-retraining groups were not significantly different. Compared to the exercise-training plus oxygen group, exercise duration improved more in the breathing-retraining group (p = 0.008) but not in the heliox group (p = 0.142). Hyperinflation was reduced with breathing-retraining plus oxygen compared to the other two groups. Six-weeks later, improvements in exercise duration were still greater with breathing-retraining than with exercise-training (p = 0.015). In contrast, improvements in exercise duration with heliox did not differ from those in the other two groups. CONCLUSIONS: In moderate-to-severe COPD, exercise-training combined with either heliox or with breathing-retraining yielded not significantly different improvements in exercise duration -- with only the latter being superior to exercise-training. Six-weeks after training, these improvements were still greater after exercise-training plus breathing-retraining than after exercise-training. TRIAL REGISTRY: ClinicalTrials.gov; number NCT00123422.

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