124 Chapter 7 Materials and methods Study design A retrospective study was conducted in the NICU of the LUMC, a tertiary-level perinatal centre with annually around 100 intensive care admissions of infants born before 30 weeks of gestation. A statement of no objection (G19.075) for obtaining and publishing the anonymised data was provided by the ethical board of the LUMC. Infants admitted to the NICU between May 1, 2012 and December 31, 2018 and born between 24 and 29 weeks and 6 days of gestation were included in the analysis. Infants were excluded from the study if they were admitted > 24 h after birth, required no invasive or non-invasive respiratory support during their admission or had major congenital abnormalities. The pre-implementation cohort included patients admitted between May 1st 2012 and June 17th 2015 that received FiO 2 manually titrated by bedside staff according to local guidelines. The post-implementation cohort consisted of infants admitted from October 18th 2015 to December 2018, taking into consideration a washout period of 4 months. Data collection All data were obtained from our patient data management systems (Metavision; IMDsoft, Tel Aviv, Israel and HiX; ChipSoft, Amsterdam, The Netherlands). Infants were invited for follow-up at 24 months corrected age for assessment by a neonatologist, paediatric physiotherapist and paediatric psychologist. Respectively they were responsible for the general and neurological examination, the assessment of motor function and assessment of cognitive functioning. Primary outcome was a composite outcome of mortality or severe neurodevelopmental impairment (NDI). Secondary outcomes were as follows: mild to moderate NDI, early mortality (mortality until one month after corrected term age), late mortality (mortality between one month after corrected term age and 2-year follow-up), motor and cognitive development scores, visual impairment, hearing loss, cerebral palsy, behavioural functioning and number of readmissions. SevereNDI was defined as at least one of the following: cerebral palsy (Gross Motor Function Classification System (GMFCS)16 ≥ level 3), Bayley-III-NL cognitive or motor scores less than two standard deviations under the mean, severe bilateral visual impairment or blindness and/or bilateral sensorineural hearing loss or deafness needing hearing aids or cochlear implants.