PaO2/FiO2 (P/F) Ratio Calculator
This calculator helps healthcare professionals assess lung function by calculating the PaO2/FiO2 ratio, a crucial metric in diagnosing ARDS and other respiratory conditions.
Results
Data Source and Methodology
All calculations are strictly based on the formulas and data provided by authoritative medical sources.
Reference: MDCalc - Horowitz Index
The Formula Explained
The P/F Ratio is calculated as follows:
\( \text{P/F Ratio} = \frac{\text{PaO2}}{\text{FiO2}} \)
Glossary of Terms
- PaO2: Partial pressure of oxygen in arterial blood, measured in mmHg.
- FiO2: Fraction of inspired oxygen, expressed as a percentage.
- P/F Ratio: A key indicator of pulmonary function.
How It Works: A Step-by-Step Example
For example, with a PaO2 of 80 mmHg and an FiO2 of 50%, the P/F ratio is calculated as follows:
\( \text{P/F Ratio} = \frac{80}{0.5} = 160 \)
Frequently Asked Questions (FAQ)
What is the P/F ratio used for?
The P/F ratio is used to assess the severity of respiratory failure and guide treatment decisions.
What is a normal P/F ratio?
A normal P/F ratio is typically above 300. A lower ratio indicates impaired lung function.
How do I convert FiO2 percentage to a decimal?
Divide the FiO2 percentage by 100 to convert it to a decimal.
Why is the P/F ratio important?
It provides a quick assessment of oxygenation efficiency and the severity of hypoxemia.
Formula (LaTeX) + variables + units
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The P/F Ratio is calculated as follows: \( \text{P/F Ratio} = \frac{\text{PaO2}}{\text{FiO2}} \)
- No variables provided in audit spec.
- MDCalc - Horowitz Index — mdcalc.com · Accessed 2026-01-19
https://www.mdcalc.com/calc/4062/horowitz-index-lung-function-p-f-ratio
Last code update: 2026-01-19
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