The oxygenation index combines mean airway pressure with the PF ratio into a single number used mainly in severe respiratory failure — especially in neonates and children — to help decide if a patient needs ECMO.
Mild.
Moderate.
Severe.
Sustained values often prompt ECMO evaluation.
Given: FiO₂ 0.6, MAP 18 cmH₂O, PaO₂ 55 mmHg.
1080 ÷ 55The more airway pressure it takes to move oxygen across, the higher the index climbs.
It is less standardized in adults than in neonates and children, but the same logic — combining how much pressure support is needed with how well oxygen is transferring — is applied in adult severe ARDS and ECMO-referral discussions.
In the commonly cited neonatal reference, a sustained OI above 40 often triggers ECMO evaluation, with 25–40 considered severe. Exact thresholds vary by center and by patient age.
A high OI means a lot of airway pressure is being used yet oxygen still isn't getting into the blood — so the lungs are failing despite aggressive support.
The ventilator reports it directly; it reflects the average pressure applied across the whole breath cycle, driven by PEEP, inspiratory pressure, and inspiratory time.