146 Chapter 8 The applied definition of BPD 16 may prove unsuitable for infants receiving automated oxygen titration. The general consensus is that during a day supplemental oxygen should be given for at least 12 hours to be counted towards the 28 days required for the diagnosis of BPD. During automated oxygen control the administered proportion oxygen may be only intermittently be above 0.21 in a 24-hour period, and this may not be predictive of BPD, for example when these brief moments are linked to apnoeic events. Depending on what criteria are used to define BPD, significantly more infants would be classified as having BPD. Severalmeasureswere taken tominimise the risk of bias associatedwith retrospective chart studies, such as missing data from patients in regional hospitals. Given that the data are relatively recent and thanks to the modest cohort size, we were able to have two independent researchers check all electronic patient records and discharge papers from regional hospitals for the outcomes. Furthermore, respiratory support data was based on automatically stored data in our patient data management system, precluding human error. In 2017 our unit changed to single room care28, and although there have been no other major changes in standard care besides type of ventilator, we cannot rule out that there are unmeasured changes that can influence results in either direction. Importantly, the outcomes of some outcomes were rare (for example mortality and PVL) and it should be noted that the power of the study may not be sufficient to observe a difference in these outcomes between the groups. This is reflected in the broad relative risk confidence intervals, indicative that the true effect may bemarkedly different. Ultimately, the retrospective nature of this study precludes us from drawing definite conclusions on the causal effect of choice of algorithm on short-term clinical outcome. Further research is warranted to replicate these findings, preferably in a large multicentre randomised trial.
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