Objective To evaluate the efficacy of automatic oxygen control (A-FiO₂) in reducing the extremes of oxygen saturations (SpO₂<80% and SpO₂>98%) in preterm infants on high-flow nasal cannula (HFNC) respiratory support using Vapotherm Precision Flow.

Design A parallel-arm randomised controlled trial.

Setting A level-III neonatal intensive care unit.

Patients Preterm infants born <33 (23+0 to 32+6) weeks receiving HFNC as respiratory support.

Interventions A-FiO₂ versus manual (M-FiO₂) oxygen control during the full course of HFNC support.

Outcomes The primary outcome of this study is percentage of time spent in extreme oxygen saturations (<80% and >98%) in preterm infants when receiving HFNC as respiratory support. Secondary outcomes were time with SpO₂ between 90% and 95% plus time >95% without supplemental oxygen.

Results 60 infants were randomised equally to either A-FiO₂ or M-FiO₂ arm. Their baseline characteristics were comparable. They spent a median of 5.3 (IQR: 2.0–8.4) and 6.5 (IQR: 2.9–13.7) days in the study, A-FiO₂ and M-FiO₂, respectively. The percentage of time spent in SpO₂<80% (median of 0.4% (0.1%–0.8%) vs 1.6% (0.6%–2.6%), p=0.002) and >98% (median 0.2% (0.1%–0.9%) vs 1.9% (0.7%–4%), p<0.001) were significantly lower in A-FiO₂ compared with M-FiO₂. The difference in median percentage of time in target range between the two arms was 26% (81% (74%–93%) in A-FiO₂ vs 55% (48%–72%) in M-FiO₂).

Conclusion A-FiO₂ was associated with statistically significant reduction in the percentage of time spent in extremes of saturation when compared with M-FiO₂ in preterm infants receiving HFNC.

Trial registration number NCT04687618.