Correlation and Prediction of Oxygen Index from Oxygen Saturation Index in Neonates with Acute Respiratory Failure

Objective The aim of this article was to evaluate the correlation between the oxygen index (OI) and the oxygen saturation index (OSI, measured by pulse oximetry and noninvasively) in neonates with acute respiratory failure and to predict the OI from the OSI. Study Design A retrospective cohort study was conducted in neonates requiring invasive mechanical ventilation who had arterial blood gas between 2018 and 2019 at a neonatal intensive care unit. The correlation between OI and OSI was analyzed by using the Pearson correlation coefficient. Results A total of 636 measurements from 68 neonates (35 preterm and 33 terms) were recruited into the study. There was a strong correlation between the OI and the OSI ( r = 0.90) in all neonates. The correlation between the OI and the OSI in persistent pulmonary hypertension of the newborn, congenital cyanotic heart disease, and other causes of respiratory failure also showed a strong correlation ( r = 0.88, 0.93, and 0.88, respectively). The correlation was strong in neonates with an oxygen saturation less than 85% ( r = 0.88), those with oxygen saturation ranging from 85 to 95% ( r = 0.87), and also in preterm and term infants (gestational age < 28, 28 - 34, 34 - 36, and >= 37 weeks, r = 0.87, 0.92, 0.89, and 0.90, respectively). There were strong accuracy measures of the OI for OI cutoffs of 5, 10, 15, and 20 (area under the curve > 0.85). The equation relating the OI and OSI was represented by: OI = (2.3 x OSI) - 4. Conclusion The OSI has a strong correlation with the OI, is a reliable assessor of the severity of respiratory failure in neonates without arterial sampling, and has high accuracy when the OI is less than 40.