PF Ratio Calculator – PaO2/FiO2 Tool
The PF Ratio Calculator helps healthcare professionals calculate the PaO₂/FiO₂ ratio, a vital metric used to assess lung function and diagnose Acute Respiratory Distress Syndrome (ARDS). It is a key indicator of how efficiently oxygen is being transferred from the lungs to the blood.
How to Use the PF Ratio Calculator
Enter the following values:
- PaO₂ (partial pressure of oxygen) – measured in mmHg
- FiO₂ (fraction of inspired oxygen) – expressed as a decimal (e.g. 50% = 0.50)
The tool will instantly calculate the PF Ratio = PaO₂ / FiO₂
PF Ratio Formula
PF Ratio = PaO₂ ÷ FiO₂
Example
PaO₂ = 90 mmHg
FiO₂ = 0.60 (60%)
→ PF Ratio = 90 ÷ 0.60 = 150
PF Ratio Interpretation
| PF Ratio | Severity |
|---|---|
| > 300 | Normal Oxygenation |
| 200–300 | Mild ARDS |
| 100–200 | Moderate ARDS |
| < 100 | Severe ARDS |
Common Use Cases
- Diagnosing ARDS in ICU or ER settings
- Monitoring patient oxygenation status
- Ventilator management
- Tracking COVID-19 respiratory severity
- Critical care and anesthesia assessment
Why Use the PF Ratio Calculator?
The PF ratio is crucial for quickly evaluating lung performance, especially in critically ill patients. It helps clinicians determine the severity of hypoxemia and guides oxygen therapy decisions.
Frequently Asked Questions (FAQs)
What is a normal PF Ratio?
A PF Ratio greater than 300 is considered normal. Below 300 may indicate impaired lung function.
What does a PF ratio below 100 mean?
A PF Ratio less than 100 indicates severe ARDS and often requires mechanical ventilation and ICU care.
Is FiO₂ the same as oxygen saturation?
No, FiO₂ is the fraction of oxygen in the air the patient breathes; SpO₂ is the measured oxygen saturation in the blood.
Can I calculate PF ratio with SpO₂?
Not directly. PaO₂ must be measured via arterial blood gas (ABG) test for accurate PF ratio.
Is the PF Ratio used in COVID-19 care?
Yes, it was widely used to classify ARDS severity in COVID-19 patients and guide ventilation strategies.
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