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

Thorax. 2021 Oct 16;thoraxjnl-2020-216509. doi: 10.1136/thoraxjnl-2020-216509. Online ahead of print.


Rationale: In patients with COPD, oxygen (O2)-supplementation via a constant flow oxygen system (CFOS) can result in insufficient oxygen saturation (SpO2 <90%) during exercise. An automatically titrating O2-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 (ESWTCFOS) and (2) ATOS targeting an SpO2 of 92% (ESWTATOS). Primary outcome measure was walking time. Secondary measures were SpO2, transcutaneous-PCO2 (TcPCO2), 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, FEV1 28.8 (24.8, 35.1) % predicted, PO2 54.7 (51.0, 57.7) mm Hg, PCO2 44.2 (38.2, 47.8) mm Hg) walked significantly longer with ESWTATOS in comparison to ESWTCFOS (median effect (95% CI) +144.5 (54 to 241.5) s, p<0.001). At isotime, SpO2 was significantly higher (+3 (95% CI 1 to 4) %, p<0.001) with ATOS while TcPCO2, RR and HR were comparable. End exercise, PO2 (+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 PCO2 was comparable.

Conclusion: In patients with hypoxaemia with severe COPD the use of ATOS leads to significant, clinically relevant improvements in walking endurance time, SpO2, PO2 and dyspnoea with no impact on PCO2.

Trial registration number: NCT03803384.

Keywords: COPD pathology; ambulatory oxygen therapy; exercise.

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