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 .