Automatically adjusted oxygen flow rates to stabilize oxygen saturation during exercise in O2-dependent and hypercapnic COPD

Introduction: O2 desaturation frequently occurs during exercise in COPD patients on long-term oxygen therapy (LTOT) due to unadjusted O2 flow rates. We evaluated a new closed-loop system (FreeO2) that automatically and continuously adjusts the O2 flows to the patient9s needs based on the recorded SpO2. In hypercapnic LTOT COPD, the impact of such a strategy on PaCO2 is of particular interest. We hypothesized that continuous O2 titration would reduce desaturation and improve exercise tolerance. Methods: 8 patients (FEV1 = 0.8 ± 0.3 L; PaCO2 = 49.5 ± 3.2 mmHg) were included in a double blind cross-over study. After assessment of maximal aerobic capacity and being familiarized with endurance shuttle walking test (ESWT, 85% peakVO2), patients performed 2 ESWT, one with FreeO2 (SpO2 target set at 94%) and the other with constant O2flows (resting O2 flow + 1L/min), in a random order. PCO2 was measured through earlobe blood capillary samplings. Results: Mean O2 flows during exercise were 5.9 ± 3.1 vs. 3.3 ± 1.4 L/min with FreeO2 vs. constant O2, respectively. All patients improved O2 saturation at the end of ESWT with FreeO2 vs. constant O2(96 [93;97] vs. 85 [77;94]%, p = 0.03, respectively). Six patients out of 8 improved their walking distance leading to a trend toward significant increase in walking distance with FreeO2 as compared to constant O2 (383 [291;610] vs. 334 [208;485] m, p = 0.07). PCO2 was similar between groups at the end and 10 min post ESWT. Conclusion: Automatic adjustment of O2 during exercise was associated with improvement in O2 saturation and a trend to significant increase in walking distance without change in PaCO2 in hypercapnic LTOT COPD.