PaO2/FiO2 Ratio (P/F Ratio)
Measures oxygenation status and classifies ARDS severity using PaO2 and FiO2.
mmHg
Arterial partial pressure of oxygen (from ABG)
fraction
Fraction of inspired oxygen (as decimal: 0.40 = 40%)
Enter PaO2 and FiO2 to calculate P/F ratio
References
- The ARDS Definition Task Force - Berlin Definition - JAMA
- The P/F Ratio - Iskander's Corner - American Thoracic Society
Clinical Notes & Warnings
- Requires PaO2 from arterial blood gas (ABG).
- Does not account for PEEP level or mean airway pressure.
- Oxygenation Index (OI) may be more informative than P/F for ECMO decisions.
- On high PEEP (>10), oxygenation may be better than P/F suggests.
Berlin ARDS criteria (2012): Mild 200-300, Moderate 100-200, Severe <100 mmHg on PEEP >=5. S/F ratio can approximate P/F: S/F = SpO2/FiO2.