Oxygenation Index Calculator – Calculate OI Online | DietDekho
🩺 Medical Tool

Oxygenation Index
Calculator (OI)

Enter the required parameters below to instantly calculate the Oxygenation Index (OI). This tool helps assess the severity of hypoxic respiratory failure, particularly in neonatal and pediatric populations.

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Calculate Your OI

Determine the Oxygenation Index using FiO2, MAP, and PaO2

Expressed as a percentage (e.g., enter 100 for 100% O2).

%
Please enter a valid FiO2 between 21 and 100.

Measured during mechanical ventilation.

cmH₂O
Please enter a valid MAP.

Partial pressure of oxygen from arterial blood gas (ABG).

mmHg
Please enter a valid PaO2.
Understanding the Math

What Is the Oxygenation Index (OI)?

The Oxygenation Index (OI) is a clinical calculation primarily used in neonatal and pediatric intensive care settings to evaluate the severity of hypoxic respiratory failure and persistent pulmonary hypertension of the newborn (PPHN). It provides a standardized metric to decide on advanced respiratory interventions like inhaled nitric oxide (iNO) and Extracorporeal Membrane Oxygenation (ECMO).

The formula for calculating the Oxygenation Index is: OI = (FiO₂ × MAP) / PaO₂. In this formula, the FiO2 is represented as a whole number percentage rather than a decimal (e.g., 100 instead of 1.0).

Clinical Interpretation
OI Severity Chart

How to Interpret OI Scores

Oxygenation Index (OI) Clinical Severity Standard Considerations (Neonatal/Pediatric)
< 15 Mild / Good Standard ventilator management; relatively good outcome expected.
15 – 25 Moderate Indicates worsening respiratory failure. Often considered a threshold for initiating inhaled Nitric Oxide (iNO).
25 – 40 Severe Severe respiratory failure. High-Frequency Ventilation (HFV) and continuous iNO are typically indicated.
> 40 Very Severe Critical condition. Generally accepted criteria to consider evaluation for ECMO (Extracorporeal Membrane Oxygenation).
Understanding The Variables
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FiO₂ (Fraction of Inspired Oxygen)

The percentage of oxygen concentration participating in gas exchange in the alveoli. Room air is approximately 21%, while medical oxygen can be delivered up to 100%. In the formula, use the percentage value (21-100).

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MAP (Mean Airway Pressure)

The average pressure applied to the lungs during mechanical ventilation over an entire respiratory cycle. It is measured in cmH₂O and represents the continuous distending pressure keeping the lungs open.

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PaO₂ (Arterial Oxygen Tension)

The partial pressure of oxygen in arterial blood, measured in mmHg. This value is obtained from an arterial blood gas (ABG) test and shows how well oxygen is able to move from the lungs into the blood.

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Clinical Utility

Because the index incorporates MAP, it is a much better marker of lung disease severity than merely looking at oxygenation alone, as it factors in the physical pressure required to achieve that oxygenation.

FAQs

Common Questions About Oxygenation Index (OI)

What formula is used to calculate OI? +
The Oxygenation Index calculation formula is: OI = (FiO2 × MAP) / PaO2. Note that FiO2 is treated as a percentage (e.g., 100 for 100%), not a decimal (like 1.0).
Why is OI used instead of the P/F ratio? +
While the P/F ratio (PaO2/FiO2) is useful for evaluating oxygenation, it does not account for the amount of airway pressure (MAP) required to achieve that oxygenation. The Oxygenation Index includes MAP, making it a more accurate reflection of lung disease severity, particularly in ventilated pediatric and neonatal patients.
When is ECMO considered based on OI? +
In neonates and pediatrics, an Oxygenation Index greater than 40 on 3 to 5 blood gases measured 30 to 60 minutes apart is generally considered a criterion to evaluate the patient for Extracorporeal Membrane Oxygenation (ECMO).
What is a normal Oxygenation Index? +
A healthy person breathing room air without mechanical ventilation cannot be accurately assessed using MAP. However, in a clinical ventilated setting, an OI less than 15 is considered mild and typically associated with a good prognosis. The lower the index, the better the oxygenation with less required ventilator support.
Medical Disclaimer: This Oxygenation Index Calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should not be based solely on the results of this calculator. Always consult with a qualified healthcare provider or intensive care physician for medical decision-making.