1. What is the PaO2/FiO2 Ratio?

The PaO2/FiO2 (P/F) ratio is a measure of oxygenation that compares arterial oxygen partial pressure (PaO2) to the fraction of inspired oxygen (FiO2). It's commonly used to assess the severity of acute respiratory distress syndrome (ARDS) and other lung conditions.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( PaO_2 \) — Arterial oxygen partial pressure (mmHg)
• \( FiO_2 \) — Fraction of inspired oxygen (decimal from 0.21 to 1.0)

Explanation: The ratio provides a standardized way to evaluate oxygenation status regardless of the amount of supplemental oxygen being administered.

3. Importance of P/F Ratio

Details: The P/F ratio is crucial for diagnosing and classifying ARDS severity:

• Mild ARDS: 200-300 mmHg
• Moderate ARDS: 100-200 mmHg
• Severe ARDS: <100 mmHg

4. Using the Calculator

Tips: Enter PaO2 in mmHg (from arterial blood gas) and FiO2 as a decimal (0.21 for room air, 1.0 for 100% oxygen). Values must be valid (PaO2 > 0, FiO2 between 0.21-1.0).

5. Frequently Asked Questions (FAQ)

Q1: What is a normal P/F ratio?
A: Normal is typically >300 mmHg on room air (FiO2 = 0.21).

Q2: How does this differ from the Oxygenation Index?
A: The OI incorporates mean airway pressure and is more commonly used in mechanical ventilation settings.

Q3: When should P/F ratio be measured?
A: It's most useful in acute settings when assessing oxygenation status and ARDS severity.

Q4: Are there limitations to this ratio?
A: It doesn't account for positive end-expiratory pressure (PEEP) or other ventilator settings that may affect oxygenation.

Q5: Can this be used for non-intubated patients?
A: Yes, it can be used for patients on supplemental oxygen via nasal cannula or mask, though interpretation may differ.