1. What is the P/F Ratio?

The P/F Ratio (PaO2/FiO2 ratio) is a clinical indicator used to assess lung function and oxygenation status. It's calculated by dividing the partial pressure of arterial oxygen (PaO2) by the fraction of inspired oxygen (FiO2).

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 provides a standardized measure of oxygenation efficiency that accounts for variations in inspired oxygen concentration.

3. Importance of P/F Ratio Calculation

Details: The P/F Ratio is crucial for diagnosing and classifying acute respiratory distress syndrome (ARDS), monitoring respiratory status in critically ill patients, and guiding oxygen therapy decisions.

4. Using the Calculator

Tips: Enter PaO2 in mmHg and FiO2 as a fraction between 0.21 and 1.0. Normal room air has an FiO2 of 0.21 (21% oxygen).

5. Frequently Asked Questions (FAQ)

Q1: What is a normal P/F Ratio?
A: A normal P/F Ratio is typically greater than 300-500 mmHg. Values below 300 may indicate impaired oxygenation.

Q2: How is P/F Ratio used in ARDS classification?
A: ARDS is classified as mild (P/F Ratio 200-300), moderate (P/F Ratio 100-200), or severe (P/F Ratio < 100).

Q3: When should P/F Ratio be measured?
A: It should be measured in patients with respiratory distress, those on mechanical ventilation, or when assessing oxygenation status in critical care settings.

Q4: Are there limitations to P/F Ratio?
A: The ratio may be affected by altitude, positive end-expiratory pressure (PEEP), and other factors that influence oxygenation.

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