Unlike the P/F ratio, the oxygenation index accounts for how much ventilator pressure is needed. It is used in neonatal and paediatric intensive care: an OI above 25 is severe and above 40 has been used as a threshold for ECMO.
How to use the Oxygenation Index Calculator
- FiO₂
- Mean airway pressure
- PaO₂
- SpO₂
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter FiO₂, mean airway pressure from the ventilator and PaO₂ (or SpO₂).
Inputs explained
| Field | What to enter |
|---|---|
| FiO₂ | In % |
| Mean airway pressure | In cmH₂O |
| PaO₂ | In mmHg |
| SpO₂ | In % |
What each result means
- Oxygenation index = [FiO₂]×[Mean airway pressure]÷[PaO₂]
- Oxygen saturation index = [FiO₂]×[Mean airway pressure]÷[SpO₂]
Example values
How the main result changes when FiO₂ changes and everything else stays at the example values above:
| FiO₂ (%) | Oxygenation index |
|---|---|
| 30 | 6.4 |
| 45 | 9.6 |
| 60 | 12.9 |
| 75 | 16.1 |
| 90 | 19.3 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
OI = FiO₂ (%) × mean airway pressure (cmH₂O) ÷ PaO₂ (mmHg)
OSI = FiO₂ (%) × mean airway pressure ÷ SpO₂ (%)
Worked example
Inputs — FiO₂: 60 %; Mean airway pressure: 15 cmH₂O; PaO₂: 70 mmHg; SpO₂: 92 %.
Results — Oxygenation index = 12.9; Oxygen saturation index = 9.8.
Key terms
- OI
- Oxygenation index.
- OSI
- Oxygen saturation index.
Frequently asked questions
What is a high oxygenation index?
Above 16 in paediatric ARDS (PALICC) is severe; above 40 may prompt ECMO consideration.
Why include mean airway pressure?
It reflects how much ventilatory support is needed to achieve the oxygenation.
When is OSI used?
When arterial blood gases are not available and SpO₂ is 97% or less.