1. What is PF Ratio?

The PF Ratio (PaO2/FiO2 ratio) is a clinical indicator used to assess pulmonary gas exchange and oxygenation status. It's particularly useful in evaluating patients with respiratory distress and acute respiratory failure.

2. How Does the Calculator Work?

The calculator uses the PF ratio formula:

Where:

• \( SpO_2 \) — Oxygen saturation measured by pulse oximetry (%)
• \( FiO_2 \) — Fraction of inspired oxygen (decimal)
• \( PaO_2 \) — Estimated arterial oxygen partial pressure

Explanation: The equation converts SpO2 to estimated PaO2 using standard conversion formulas, then divides by FiO2 to obtain the PF ratio.

3. Importance of PF Ratio Calculation

Details: PF ratio is crucial for diagnosing and classifying acute respiratory distress syndrome (ARDS), monitoring respiratory status, and guiding oxygen therapy decisions.

4. Using the Calculator

Tips: Enter SpO2 as a percentage (0-100%) and FiO2 as a decimal (0.21-1.0). Normal room air is FiO2 = 0.21.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal PF ratio?
A: Normal PF ratio is >400 mmHg. Values between 300-400 indicate mild impairment, 200-300 moderate impairment, and <200 severe impairment.

Q2: How accurate is SpO2 to PaO2 conversion?
A: The conversion provides an estimate. For precise measurements, arterial blood gas analysis is recommended.

Q3: When should PF ratio be measured?
A: It should be measured when assessing patients with respiratory symptoms, monitoring ARDS progression, or evaluating oxygen therapy effectiveness.

Q4: Are there limitations to using SpO2 for PF ratio?
A: Yes, SpO2 measurements can be affected by poor perfusion, motion artifacts, nail polish, and certain hemoglobin variants.

Q5: How does PF ratio relate to ARDS classification?
A: PF ratio <300 indicates ARDS, <200 indicates moderate ARDS, and <100 indicates severe ARDS when other criteria are met.