Automatic oxygen titration versus constant oxygen flow rates during walking in COPD: a randomised controlled, double-blind, crossover trial

RATIONALE: In patients with COPD, oxygen (O(2))-supplementation via a constant flow oxygen system (CFOS) can result in insufficient oxygen saturation (SpO(2) <90%) during exercise. An automatically titrating O(2)-system (ATOS) has been shown to be beneficial compared with an untitrated CFOS, however, it is unknown if ATOS is superior to CFOS, titrated during exercise as stipulated by guidelines. The aim was to investigate the effects of ATOS compared with titrated CFOS on walking capacity in people with hypoxaemic COPD. METHODS: Fifty participants completed this prospective randomised controlled, double-blind, crossover trial. Participants performed two endurance shuttle walk tests (ESWTs) with: (1) exercise titrated CFOS (ESWT(CFOS)) and (2) ATOS targeting an SpO(2) of 92% (ESWT(ATOS)). Primary outcome measure was walking time. Secondary measures were SpO(2), transcutaneous-PCO(2) (TcPCO(2)), respiratory rate (RR), heart rate (HR) at isotime (end of shortest ESWT) with blood gases and dyspnoea at rest and end exercise. RESULTS: Participants (median (IQR): age 66 (59, 70) years, FEV(1) 28.8 (24.8, 35.1) % predicted, PO(2) 54.7 (51.0, 57.7) mm Hg, PCO(2) 44.2 (38.2, 47.8) mm Hg) walked significantly longer with ESWT(ATOS) in comparison to ESWT(CFOS) (median effect (95% CI) +144.5 (54 to 241.5) s, p<0.001). At isotime, SpO(2) was significantly higher (+3 (95% CI 1 to 4) %, p<0.001) with ATOS while TcPCO(2), RR and HR were comparable. End exercise, PO(2) (+8.85 (95% CI 6.35 to 11.9) mm Hg) and dyspnoea (−0.5 (95% CI −1.0 to −0.5) points) differed significantly in favour of ATOS (each p<0.001) while PCO(2) was comparable. CONCLUSION: In patients with hypoxaemia with severe COPD the use of ATOS leads to significant, clinically relevant improvements in walking endurance time, SpO(2), PO(2) and dyspnoea with no impact on PCO(2). TRIAL REGISTRATION NUMBER: NCT03803384.