Ambulatory Long-Term Oxygen Therapy in Patients with Severe COPD: A Randomized Crossover Trial to Compare Constant-Minute-Volume and Constant-Bolus Systems.

Background and Methods: Constant-minute-volume and constant-bolus devices serve as two different means of portable oxygen conservation. A prospective randomised crossover study was conducted in COPD GOLD IV patients to investigate the effect of these two devices on dyspnea, oxygenation and 6-minute walking test (6MWT) distance. The primary endpoint was the final operating level required (operating level range 1-5 for both devices) by either device to meet the success criteria for mobile oxygen therapy, as outlined in the British Thoracic Society guidelines (SpO2 ≥90% throughout 6MWT; ≥10% increase in walking distance from baseline; improvement in BORG of at least 1 point from baseline). Results: Twenty-five patients were enrolled in the study and randomly assigned to one of two sequences involving the use of each type of portable oxygen conservation device. 14 female, 67.9 years (±7.8); FEV1: 27.3%pred. (±8.4); PaO2 at rest without oxygen: 50.3mmHg (±5.9). For both systems, 24/25 patients (96%) were successfully recruited. The mean operating-level difference when success criteria were met was -0.58 in favor of the constant bolus device (95% CI: -0.88 to -0.28, P <0.001). Secondary endpoints (walking distance, respiratory rate and BORG dyspnea) showed no statistically significant or clinically relevant differences. An algorithm created especially for this study showed a high success rate in terms of titration for the required operating level. Conclusion: Both portable oxygen-conserving devices met the success criteria in 96% of patients in the 6MWT when they were titrated to the correct level. The constant-bolus device required a significantly lower operating level to achieve the success criteria, hereby reducing energy consumption. Individual titration of the respective device is recommended, which can be facilitated by the novel titration algorithm described here.