Noninvasive oxygenation monitoring in PPHN: validation of the oxygen saturation index and the oxygen saturation to fraction of inspired oxygen ratio against conventional invasive indices.

OBJECTIVE

To evaluate the correlation and agreement between the Oxygen Saturation Index (OSI) and Oxygenation Index (OI), and between the SpO2/FiO2 ratio (S/F) and PaO2/FiO2 ratio (P/F) in neonates with persistent pulmonary hypertension (PPHN), and to identify noninvasive thresholds for clinical use.

STUDY

DESIGN

This retrospective study analyzed 2717 paired arterial blood gas and SpO2 measurements from 377 PPHN infants treated at a tertiary NICU (2012-2021). Correlation (Spearman), linear mixed-effects models (LMMs), Bland-Altman agreement, and ROC analyses were performed across SpO2 strata.

RESULTS

OSI strongly correlated with OI (r = 0.93), and S/F with P/F (r = 0.84), with best performance at SpO2 ≥80%. Agreement declined under severe hypoxemia. ROC analysis showed excellent discrimination for OSI (AUC > 0.96) and good performance for S/F (AUC up to 0.96).

CONCLUSION

OSI and S/F are reliable noninvasive surrogates for invasive oxygenation indices when SpO2 ≥ 80% and may help reduce arterial sampling in PPHN monitoring.