Hylke Salverda

109 6 The effect of AOC on clinical outcomes in preterm infants: a pre- and post- study according to the modified Bell staging criteria.24 IVH was classified according to Papile’s adapted classification 25, 26, PVL according to the de Vries’ classification. 27 Oxygen titration Following the recent European guidelines 28, the SpO 2 TR in our NICU changed from 85%-95% to 90-95% in November 2014. The ventilator used for respiratory support was the AVEA ventilator (Vyaire, Yorba Linda CA, United States) during the majority of the study period. In August 2015 the CLiO2 TM algorithm (Closed Loop of inspired Oxygen) 14 was implemented in the AVEA ventilator. This is a hybrid rule-based adaptive algorithm designed for AOC in preterm infants. In November 2018 the SLE6000 (SLE, London, United Kingdom) was introduced as standard of care ventilator. The SLE6000 has the VDL1.1 algorithm 29 built-in as the Oxygenie® option, a PID algorithm with several enhancements. Both algorithms are described in more detail elsewhere. 30 Data analysis Data are presented as mean (SD), median (range) or number (percentage) as appropriate, with standard tests for normality. Statistical comparison was performed using an independent t-test, a Mann-Whitney U test, a chi-square or Fisher’s exact respectively. Statistical analyses were performed by IBM SPSS Statistics for Mac, version 25 (IBM, Armonk, New York, USA). Two-tailed P-values of <0.05 were considered statistically significant. Results Patient characteristics During the study period 588 infants within the gestation range 24-29 weeks were admitted to the LUMC NICU, of which 8 were excluded from analysis (admitted >24 h, n=6; major congenital anomaly, n=2). In the pre-implementation cohort 293 infants were included and compared with 295 infants in the post-implementation cohort. There were no significant differences in baseline characteristics between the groups (table 1), so we can assume that treatment assignment cannot be retrospectively related to patient characteristics. The LUMC is a national referral centre for foetal therapy, which is reflected by a high number of multiple pregnancies in both groups.