Respiratory

Oxygenation Index (OI) Calculator

Mean airway pressure times FiO₂ over PaO₂: how much ventilator support it takes to oxygenate, used mostly in neonates and children.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Turn on JavaScript to use this calculator, or open it in the web app.

Formula

OI = (Mean Airway Pressure × FiO₂) / PaO₂

How it is used

• Used commonly in pediatric/neonatal ICUs and severe adult ARDS.
• OI > 40 is frequently used as an indication for ECMO consideration in neonates.

Same formula as the app. Open it in the web app.

Related one-pagers

• Neonatal and Pediatric Respiratory CareOI = MAP × FiO₂ × 100 ÷ PaO₂; 40 means ECMO referral.
• CEN: HEENT EmergenciesOpen globe · Laceration, Seidel sign, irregular pupil, odd chamber depth, no red reflex · Shield taped to bony rim, NPO, IV antibiotics, antiemetic, tetanus, CT · Patch, pressure, drops or ointment, MRI
• Equipment, Gas Supply and Patient DataRegulator fires: crack the valve first, new crush gasket (or reusable metal-bound washer), no oil or grease, hand-tighten, open slowly. Hissing at the yoke: close the valve, then reseat or replace the seal.
• Vasopressors and InotropesNo phentolamine: terbutaline 0.5–1 mg diluted in up to 10 mL saline infiltrated subcutaneously, or 2% nitroglycerin ointment over the area (Stefanos, Pharmacotherapy 2023).

Related calculators

• A-a Gradient
• Alveolar Gas Equation (PAO₂)
• Arterial Oxygen Content (CaO₂)
• Dead Space Fraction (Bohr)
• Driving Pressure
• Dynamic Compliance
• Minute Ventilation
• O₂ Extraction Ratio

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.