ToolsCalculators
Oxygenation index (OI)
Grades hypoxaemic respiratory failure severity in ventilated patients.
Oxygenation index (OI)
FiO₂
%
Mean airway pressure
cmH₂O
PaO₂
mmHg
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When to use
- Quantifying and trending severity of hypoxaemic respiratory failure in a mechanically ventilated patient.
- Applying paediatric ARDS severity categories and informing ECMO discussions.
Formula
OI = (FiO₂ [%] × mean airway pressure [cmH₂O]) ÷ PaO₂ [mmHg]. Higher values indicate worse oxygenation.
Pearls and pitfalls
- Because it incorporates mean airway pressure, OI reflects ventilator support as well as gas exchange, unlike the P/F ratio.
- PALICC paediatric ARDS bands: mild 4 to <8, moderate 8 to <16, severe ≥16 on invasive ventilation.