Hylke Salverda

61 3 Comparison of two devices for automated oxygen control in preterm infants OxyGenie adjusted FiO2 about 10 times more frequently than the CLiO2 device (1155 (1044 – 1255) vs 194 (178 – 205) adjustments/hour, p = 0.001). The average delivered FiO2 was similar during both study periods (0.27 +-0.05 vs 0.26 +- 0.08, p = 0.56). FiO2 was more variable when titrated by the OxyGenie algorithm (coefficient of variation 19.5% (15.2% - 25.0%) vs 13.3% (12.8% - 19.0%), p = 0.015). During OxyGenie control, manual overrides of the AOC were made only in one individual subject (4 adjustments) versus nine individuals (16 adjustments) with manual overrides during the period of CLiO2 oxygen control. Discussion In this randomised controlled crossover study, automated titration of inspired oxygen concentration using the OxyGenie controller significantly increased the time spent within the SpO2 TR when compared to the CLiO2 controller. The difference in controller function was reflected in the SpO2 histogram, with a more balanced distribution of SpO2 values within and around the TR during OxyGenie control. This resulted in significantly less time spent above the TR, and fewer hyperoxaemic episodes, albeit at the cost of a small increase in time spent with SpO2 values below TR. The greater time with SpO2 in the range 80-90% with OxyGenie compared with CLiO2 control was not accompanied by an increase in the frequency of hypoxic episodes, which were, indeed, significantly fewer during OxyGenie control. These results suggest that algorithm design, and in particular algorithm responsiveness, plays an important role in how successful SpO2 targeting will be with a given oxygen control device. This is the first study to compare two different ventilators incorporating AOC algorithms head-to-head. Although earlier studies have individually compared the algorithms in question to manual oxygen titration,15-20, 23, 24 heterogeneity between the studies has precluded drawing inferences about their function relative to each other. Our findings in relation to proportion of time within TR were similar to previous studies, implying that the SpO2 targeting results achieved by controllers in our study were representative of their overall performance. Compared with the TR time of 80% in this study, other studies of OxyGenie control have demonstrated TR times of 81% 23 and 88%.28 For CLiO 2 (69% TR time in this study), other studies have shown TR time of 40%15, 58%16, 62%18, 76%19, 73%20 and 62%24) The study was terminated before reaching the predetermined sample size of 50 infants. The deployment of the SLE6000 ventilator at LUMC had an impact on numbers of eligible infants by virtue of 1) the option of nasal high flow (not available