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

Introduction: O 2 desaturation frequently occurs during exercise in COPD patients on long-term oxygen therapy (LTOT) due to unadjusted O 2 flow rates. We evaluated a new closed-loop system (FreeO 2 ) that automatically and continuously adjusts the O 2 flows to the patient9s needs based on the recorded SpO 2 . In hypercapnic LTOT COPD, the impact of such a strategy on PaCO 2 is of particular interest. We hypothesized that continuous O 2 titration would reduce desaturation and improve exercise tolerance. Methods: 8 patients (FEV 1 = 0.8 ± 0.3 L; PaCO 2 = 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% peakVO 2 ), patients performed 2 ESWT, one with FreeO 2 (SpO 2 target set at 94%) and the other with constant O 2 flows (resting O 2 flow + 1L/min), in a random order. PCO 2 was measured through earlobe blood capillary samplings. Results: Mean O 2 flows during exercise were 5.9 ± 3.1 vs. 3.3 ± 1.4 L/min with FreeO 2 vs. constant O 2 , respectively. All patients improved O 2 saturation at the end of ESWT with FreeO 2 vs. constant O 2 (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 FreeO 2 as compared to constant O 2 (383 [291;610] vs. 334 [208;485] m, p = 0.07). PCO 2 was similar between groups at the end and 10 min post ESWT. Conclusion: Automatic adjustment of O 2 during exercise was associated with improvement in O 2 saturation and a trend to significant increase in walking distance without change in PaCO 2 in hypercapnic LTOT COPD.