1. What is a PaO2/FiO2 Ratio Calculator?

Definition: This calculator computes the PaO2/FiO2 ratio (P/F ratio) to assess lung oxygenation efficiency.

Purpose: It helps evaluate hypoxemia severity, often used in diagnosing Acute Respiratory Distress Syndrome (ARDS).

2. How Does the Calculator Work?

The P/F ratio is calculated using:

Unit conversions for PaO2:

• Pa to mmHg: Multiply by 0.00750062
• hPa to mmHg: Multiply by 0.750062
• kPa to mmHg: Multiply by 7.50062
• inHg to mmHg: Multiply by 25.4

FiO2 conversion:

• FiO2 (% to fraction): Divide by 100

Explanation: PaO2 is converted to mmHg, FiO2 to a fraction, then the ratio is computed.

3. Importance of P/F Ratio Calculation

Details: A lower P/F ratio indicates worse oxygenation, aiding in ARDS classification (e.g., ≤300 mmHg for mild ARDS).

4. Using the Calculator

Tips: Enter PaO2 (in any supported unit) and FiO2 (%); both must be >0. Results show the P/F ratio in mmHg.

• Normal: > 400
• Mild ARDS: 200–300
• Moderate ARDS: 100–200
• Severe ARDS: < 100

5. Frequently Asked Questions (FAQs)

Q1: What does a low P/F ratio indicate?
A ratio <300 suggests hypoxemia, potentially ARDS, requiring medical attention.

Q2: Why is FiO2 important in the calculation?
FiO2 adjusts for supplemental oxygen, making the ratio a true measure of lung function.

Q3: Can I use pulse oximetry instead of PaO2?
No, PaO2 requires an arterial blood gas test; SpO2 from pulse oximetry isn’t equivalent.

Q4: How does altitude affect the P/F ratio?
At higher altitudes, lower atmospheric pressure reduces PaO2, potentially lowering the ratio.

Q5: When should I consult a doctor?
If the P/F ratio is <300, especially with symptoms like shortness of breath, seek medical advice.

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