# Oxygenation Index Calculator (OI and OSI)

URL: https://speedycalculator.com/calculators/health/oxygenation-index/
Last updated: 2026-10-30

> The oxygenation index calculator measures the severity of hypoxaemic respiratory failure in ventilated patients from FiO₂, mean airway pressure and PaO₂, and gives the oxygen saturation index (OSI) when only SpO₂ is available.

## Inputs

- FiO₂ (%)
- Mean airway pressure (cmH₂O)
- PaO₂ (mmHg)
- SpO₂ (%)

## Results

- Oxygenation index
- Oxygen saturation index

## Formula

```
OI = FiO₂ (%) × mean airway pressure (cmH₂O) ÷ PaO₂ (mmHg)
OSI = FiO₂ (%) × mean airway pressure ÷ SpO₂ (%)
```

## Explanation

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

FieldWhat to enterFiO₂In %Mean airway pressureIn cmH₂OPaO₂In mmHgSpO₂In %

### 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 index306.4459.66012.97516.19019.3
*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.*

## 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.

## FAQ

**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.


## Sources

- [PALICC – Pediatric acute respiratory distress syndrome consensus recommendations (2023)](https://pubmed.ncbi.nlm.nih.gov/36661420/)