About this Oxygen Index (OI)
Oxygen Index (OI) helps clinicians describe how much ventilatory support is being used relative to the oxygen level achieved. A higher OI generally reflects more severe oxygenation failure, but escalation decisions depend on the full ICU picture and local protocols.
Who this calculator is for
- ICU clinicians, respiratory therapists, and trainees reviewing ventilated-patient oxygenation data.
- People learning how FiO2, mean airway pressure, and PaO2 combine into a single severity metric.
- Anyone who needs a quick OI snapshot from already measured ventilator and blood-gas values.
When to use it
- Use this calculator when mean airway pressure, FiO2, and PaO2 are all available at the same time point.
- Use it to trend respiratory severity over serial blood gases in a ventilated patient.
- Use it as an educational reference when discussing oxygenation indices in neonatal or pediatric critical care.
How to use this calculator
- Enter Mean Airway Pressure (MAP) from the ventilator.
- Enter FiO2 percentage (e.g., 50 for 50%).
- Enter PaO2 from the arterial blood gas.
Key assumptions
- The calculation assumes the ventilator settings and arterial blood gas are from the same clinical moment.
- OI is a severity descriptor, not a standalone rule for intubation, ECMO, or other treatment decisions.
- Thresholds vary by population and protocol, especially between neonatal, pediatric, and adult care settings.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
Key Features
- Instant Calculation
- Private & Secure
- Mobile Optimized
Things to Keep in Mind
Clinical parameters such as MAP and PaO2 change rapidly. This calculation is a snapshot in time.