Review of the Oxygenation Index

The oxygenation index (OI) captures the severity of hypoxemic respiratory failure by using two parameters of ventilator settingsbreath as the numerator and a blood oxygenation parameter as the denominator. The two ventilator parameters are Mean Airway Pressure (MAP) in cmH2O and FiO₂ as a percentage. The blood oxygenation parameter is PaO₂ in mmHg.

Oxygenation Index = (FiO2 ×MAP)/PaO2 ×100

OI is built on another commonly used index, the PaO2/FiO2 (P/F) ratio, which accounts for oxygenation and delivered FiO₂, delivery but does not take into account the ventilator pressure required to achieve the PaO2.