This secondary analysis of the Milrinone in CDH Trial evaluated how well the non-invasive Oxygen Saturation Index (OSI) predicts the invasive Oxygenation Index (OI) in 61 neonates with congenital diaphragmatic hernia (CDH) and significant hypoxemia (OI≥10 or OSI≥5), using 572 matched PaO2-SpO2 pairs from a prospective multicenter cohort.
Preductal OSI correlated strongly with OI (r=0.82; 95% CI 0.79–0.85 across all 572 samples). When SpO2 was matched from the same site as the arterial blood gas, correlation was 0.97 (preductal) and 0.86 (postductal). The best-fit quadratic equations were: preductal OI = 0.3×OSI + 0.1×OSI² + 2.4; postductal OI = 0.6×OSI + 0.08×OSI² + 2.6.
- Preductal-matched pairs were available in only 4 patients (22 samples), limiting confidence in the preductal-specific equation. - This is a secondary analysis of a single trial (Milrinone in CDH), so findings may not generalize to all CDH populations or severity spectra. - Site-specific quadratic models did not improve model fit (QICu) over simpler linear models.
OSI derived from preductal SpO2 correlates well with invasive OI in CDH and may serve as a viable non-invasive endpoint in clinical trials, even when postductal arterial access is present. Clinicians and trialists can consider OSI as a practical substitute to reduce reliance on arterial blood gas sampling in this population.
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