Oxygen Saturation Index in Neonates with a Congenital Diaphragmatic Hernia: A Retrospective Cohort Study

Introduction: The oxygenation index (OI) is a marker for respiratory disease severity and adverse neonatal outcomes. The oxygen saturation index (OSI) is an alternative that allows for continuous noninvasive monitoring, but evidence for clinical use in critically ill neonates is scarce. The aim of this study was to evaluate the OSI as compared to the OI in term neonates with a congenital diaphragmatic hernia (CDH). Methods: A single-center retrospective cohort study was conducted including all live-born infants with an isolated CDH between June 2017 and December 2020. Paired values of the OI and OSI in the first 24 h after birth were collected. The relation between OI and OSI measurements was assessed, taking into account arterial pH, body temperature, and preductal versus postductal location of oxygen saturation measurement or arterial blood sampling. The predictive values for pulmonary hypertension, need for extracorporeal membrane oxygenation therapy, and survival at discharge were evaluated. Results: Of 33 subjects included, 398 paired values of the OI (median 5.8 [3.3-17.2]) and OSI (median 7.3 [3.6-14.4]) were collected. The OI and OSI correlated strongly (r = 0.77, p < 0.001). The OSI values corresponding to the clinically relevant OI values (10, 15, 20, and 40) were 8.9, 10.9, 12.9, and 20.9, respectively. The predictive values of the OI and OSI were comparable for all adverse neonatal outcomes. No difference was found in the area under the receiver operating characteristic curves for the OI and the OSI for adverse neonatal outcomes. Conclusions: The OSI could replace the OI in clinical practice in infants with a CDH.