Study objectives: To compare, in clinical conditions, the efficacy of refilled oxygen cylinders (O2-HFs) in improving oxygenation and exercise capacity of patients with COPD during a 6-min walking test.
Design: Prospective randomized study with a cross-over design.
Setting: A university teaching hospital.
Patients: Ten patients with COPD, in a stable state and previously treated with long-term domiciliary oxygen therapy. Baseline characteristics were as follows: age, 65 +/- 7 years; PaO2 on room air, 55.4 +/- 6.3 mm Hg; PaCO2 on room air, 46.2 +/- 7.4 mm Hg; FEV1/vital capacity, 47 +/- 7%; and FEV1, 30 +/- 7% of predicted value (mean +/- SD).
Design: All patients performed three successive 6-min walking tests, the first test in room air and the other tests in a randomized order with either a conventional oxygen cylinder (O2-C) or an O2-HF.
Measurements and results: The fraction of inspired oxygen (FIO2) delivered by O2-HFs was significantly lower than the FIO2 delivered by O2-Cs (94.2 +/- 2.6% vs 98.8 +/- 4.9%, p = 0.02). Mean O2-HF and O2-C weights before the walking tests were similar (3,510 +/- 251 g and 3,770 +/- 142 g, respectively; p = 0.09). Mean transcutaneous oxygen saturation was similarly improved with both oxygen delivery systems. Mean distances with O2-C (373.5 +/- 81 m) and O2-HF (375 +/- 97 m) were not different but significantly improved, as compared with room air (334.5 +/- 90 m; p = 0.03 and 0.02, respectively). Dyspnea sensations were similar for the three tests.
Conclusion: O2-HFs are as efficient as O2-Cs for performing short-term exercises. Because of a lower cost, pressurizing units may be worthwhile for improving ambulatory oxygen therapy and pulmonary rehabilitation programs.