Oxygenation saturation index in neonatal hypoxemic respiratory failure.

Background: This study aimed to assess the validity of the oxygenation saturation index (OSI) and the ratio of oxygen saturation to the fraction of inspired oxygen (FO) (S/F ratio) with percutaneous oxygen saturation (OSI and the S/F ratio) and to evaluate the correlation between these values and the oxygen index (OI). It also determined their cut-off values for predicting OI in accordance with neonatal hypoxic respiratory failure severity.

Methods: We reviewed the data of 77 neonates (gestational age 31.7 ± 6.1 weeks; birthweight, 1768 ± 983 g) requiring invasive mechanical ventilation between 2013 and 2020, 1233 arterial blood gas samples in total. We calculated the OI, OSI, OSI with arterial oxygen saturation (SaO) (OSI), S/F ratio, and the ratio of SaO to FO (S/F ratio).

Results: The regression and Bland-Altman analysis showed good agreement between OSI or the S/F ratio and OSI or the S/F ratio. Although a significant positive correlation was found between OSI and OI, OSI was overestimated in SpO > 98% with a higher slope of the fitted regression line than that below 98% of SpO. Furthermore, receiver-operating characteristic curve analysis using only SpO ≤ 98% samples showed that the optimal cut-off points of OSI and the S/F ratio for predicting OI were: OI 5, 3.0 and 332; OI 10, 5.3 and 231; OI 15, 7.7 and 108; OI 20, 11.0 and 149; and OI 25, 17.1 and 103, respectively.

Conclusion: The cut-off OSI and S/F ratio values could allow continuous monitoring for oxygenation changes in neonates with the potential for wider clinical applications.