Oxygenation Index (OI) — Pediatric and Neonatal ARDS Severity Calculator

The Oxygenation Index (OI) is a standardized physiological measure of oxygenation efficiency in mechanically ventilated patients that accounts for both the degree of supplemental oxygen required AND the mean airway pressure (MAP) applied — unlike PaO₂/FiO₂ (P/F ratio) which only accounts for FiO₂. Formula: OI = (FiO₂ × Mean Airway Pressure × 100) / PaO₂. Higher OI = worse oxygenation for the level of ventilatory support. OI is the primary ARDS severity metric in the Pediatric Acute Lung Injury Consensus Conference (PALICC-2) criteria and is used to guide ECMO/inhaled nitric oxide decision-making in pediatric and neonatal intensive care.