Oxygenation Index (OI) Calculator

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Percentage of oxygen in the gas mixture delivered to the patient. Room air = 21%, pure oxygen = 100%.
%
Mean airway pressure from the ventilator monitor. For BiPAP/CPAP patients use the MAP estimator below.
cmH2O
Enable to calculate MAP from IPAP, EPAP, inspiratory time, and respiratory rate (useful when MAP is not directly displayed).
Partial pressure of oxygen measured from an arterial blood gas sample.
mmHg
Oxygenation Index (OI)Mild impairment
10.3

Higher values indicate worse oxygenation and greater support requirements.

P/F ratio (PaO2/FiO2)117mmHg
FiO2 (decimal)0.6
10.3
Normal<5Mild5-15Moderate15-25Severe25-40Critical / ECMO40+

OI 10.3 - mild oxygenation impairment, consistent with early or resolving lung disease.

  • Values in this range indicate some diffusion barrier or V/Q mismatch but generally manageable with conventional ventilation.
  • Optimise PEEP and FiO2 to minimise oxygen toxicity while maintaining target saturation.
  • The complementary P/F ratio is 117 mmHg, placing the patient in the moderate ARDS range (100-200).

Next stepReassess every 4-6 hours and trend the value to detect deterioration early.

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