Methods: There are different technologies for portable oxygen-conserving devices: constant-minute-volume devices and constant-bolus devices. A prospective randomised crossover study investigated the effect of the two devices on dyspnea, oxygenation and 6-minute walking test (6MWT) distance in COPD GOLD IV patients. Participants performed one 6MWT without oxygen and at least one 6MWT with either device. Primary endpoint was the final operating level necessary for either device required to meet the success criteria for mobile oxygen therapy (SpO2s ?90% throughout 6MWT; ?10% increase in walking distance from baseline; improvement in BORG of ?1 point from baseline).

Results: 25 patients were included (female=14, Ø67.9 years (±7.8); FEV1:27.3%pred. (±8.4); PaO2 at rest without O2:50.3mmHg(±5.9). 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). In both systems, 24/25 patients (96%) were successfully recruited. Secondary endpoints walking distance, respiratory rate and BORG dyspnea showed no statistically significant difference. An algorithm created specifically for this study showed a high success rate regarding the titration of the required operating level.

Conclusion: Both portable oxygen conserving devices met the success criteria for 96% of patients in the 6MWT when titrated to the correct level. The constant bolus device required a significantly lower operating level to achieve success criteria. Individual titration of the respective device is recommended, which can be supported by the newly developed titration algorithm.