Oxygenation index explained

The oxygenation index is a calculation used in intensive care medicine to measure the fraction of inspired oxygen (FiO2) and its usage within the body.

A lower oxygenation index is better - this can be inferred by the equation itself. As the oxygenation of a person improves, they will be able to achieve a higher PaO2 at a lower FiO2. This would be reflected on the formula as a decrease in the numerator or an increase in the denominator - thus lowering the OI. Typically an OI threshold is set for when a neonate should be placed on ECMO, for example >40.

Equation

$OI\; =\; \backslash frac$^[1]

• $Fi\backslash ce$: Fraction of inspired oxygen, in percent;

M _{PAW} : Mean airway pressure, in mmHg;

• $Pa\backslash ce$: Partial pressure of oxygen in arterial blood, in mmHg.

References

1. Ortiz RM, Cilley RE, Bartlett RH. Extracorporeal membrane oxygenation in pediatric respiratory failure. Pediatr Clin North Am. 1987 Feb;34(1):39-46.