63 3 Comparison of two devices for automated oxygen control in preterm infants increase in time spent with SpO2 80%-90%. Although at first glance it appears there is a trade-off between hyperoxaemia and hypoxaemia, the reduction in hypoxaemic episodes with OxyGenie control suggests that hypoxaemia is resolved more quickly. This is in line with the clinical observation of caregivers, who reported that OxyGenie responded more rapidly to SpO2 deviations into hypoxaemia than CLiO2. Compared to other studies, time with SpO2 <80% was modest with both controllers. For the OxyGenie controller it was 0.5% in our study vs 0% 23 previously; for the CLiO 2 controller it was 0.2% whereas other studies reported 9.8% 15, 1.2% and 0.8% 18, 3.1% 19, 1.3% 20 and 0.9% 24. The increase in time spent under TR could be due to a lower median SpO2 during OxyGenie control (93% vs 94%) on the steeper part of the oxygen-dissociation curve. The higher median SpO2 during CLiO2 control could be because, according to the patent, an SpO2 of 94% is targeted while in TR and the FiO2 is rarely titrated below the BaseFiO2. 26 Even though the benefit of AOC on SpO2 TR time is well-established, the effect on clinical outcome is still unknown. The effect of SpO2 targeting within different ranges on clinical outcome was demonstrated by the NeOPRoM trials,4 and a range of studies have evidenced the harmful effects of hypoxaemia and hyperoxaemia (and episodes thereof),34-39 both of which are affected by AOC. We would maintain that when searching for clinical effect of AOC it is important to use an algorithm that most successfully avoids and mitigates SpO2 deviations, because the effect on clinical outcomes may be modest and in some cases may be difficult to detect given their relatively low incidence. Finally, low compliance in TR adherence such as reported in the NeOPRoM trials4 could be improved upon by using AOC. For the best differentiation between treatment groups it is important to have a controller that best targets the predefined ranges. Conclusion In this study the OxyGenie controller was more effective in keeping the oxygen saturation within target range and preventing hyperoxaemia, and just as effective in preventing hypoxaemia (SpO2<80%), albeit at the cost of a small increase with SpO2 80%-90%.