1. What is the P/F Ratio?

The P/F ratio (PaO₂/FiO₂ ratio) is a measure of oxygenation used to assess respiratory function, particularly in critical care settings. It's a key component in diagnosing and classifying acute respiratory distress syndrome (ARDS).

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 (0.21 for room air to 1.0 for 100% oxygen)

Interpretation: The calculator also provides a normal distribution analysis of the result based on standard clinical ranges.

3. Importance of P/F Ratio

Details: The P/F ratio is crucial for assessing oxygenation status, diagnosing ARDS, and guiding mechanical ventilation strategies in critically ill patients.

4. Using the Calculator

Tips: Enter PaO₂ in mmHg (from arterial blood gas) and FiO₂ as a decimal (0.21-1.0). The calculator will compute the ratio and provide interpretation.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal P/F ratio?
A: Normal P/F ratio is >300 mmHg. Values between 200-300 indicate mild, 100-200 moderate, and <100 severe hypoxemia.

Q2: How is this different from SpO₂/FiO₂ ratio?
A: SpO₂/FiO₂ is a non-invasive alternative but less accurate. P/F ratio using PaO₂ is the gold standard.

Q3: When should P/F ratio be measured?
A: Primarily in ICU settings for patients on supplemental oxygen or mechanical ventilation, especially when ARDS is suspected.

Q4: What are limitations of P/F ratio?
A: It doesn't account for PEEP levels, patient effort, or other ventilatory parameters that affect oxygenation.

Q5: How does P/F ratio relate to ARDS classification?
A: ARDS is classified as mild (P/F 200-300), moderate (P/F 100-200), and severe (P/F <100) when PEEP ≥5 cmH₂O.