1. What is the P/F Ratio?

The P/F Ratio (PaO2/FiO2 ratio) is a clinical indicator used to assess the severity of hypoxemia and lung function. It's particularly useful in diagnosing and monitoring acute respiratory distress syndrome (ARDS) and other respiratory conditions.

2. How Does the Calculator Work?

The calculator uses the P/F Ratio formula:

Where:

• \( PaO_2 \) — Partial pressure of arterial oxygen (mmHg)
• \( FiO_2 \) — Fraction of inspired oxygen (0-1)

Explanation: The ratio compares the oxygen level in arterial blood to the concentration of oxygen being inhaled, providing a measure of how effectively the lungs are oxygenating the blood.

3. Importance of P/F Ratio Calculation

Details: The P/F Ratio is crucial for diagnosing ARDS severity, guiding treatment decisions, monitoring patient progress, and determining the need for advanced respiratory support.

4. Using the Calculator

Tips: Enter PaO2 in mmHg and FiO2 as a fraction between 0.21 and 1.0. Both values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are normal P/F Ratio values?
A: Normal P/F Ratio is typically >400 mmHg. Values between 300-400 indicate mild hypoxemia, 200-300 moderate, and <200 severe hypoxemia/ARDS.

Q2: How is ARDS classified using P/F Ratio?
A: Mild ARDS: 200-300 mmHg, Moderate ARDS: 100-200 mmHg, Severe ARDS: <100 mmHg (with PEEP ≥5 cm H2O).

Q3: When should P/F Ratio be measured?
A: It should be measured when assessing patients with respiratory distress, monitoring ARDS patients, or evaluating the need for mechanical ventilation.

Q4: Are there limitations to P/F Ratio?
A: The ratio can be affected by altitude, barometric pressure, and the accuracy of FiO2 measurement. It should be interpreted in clinical context.

Q5: How does P/F Ratio differ from other oxygenation indices?
A: P/F Ratio is simpler than other indices like Oxygenation Index (OI) but provides a quick assessment of oxygenation efficiency.