mmHg (arterial)
⚕️ For clinical reference only. Not a substitute for professional judgment.
PaO₂/FiO₂ Ratio PF Ratio
Classifies ARDS severity using the Berlin definition. Use arterial PaO₂ and FiO₂ on current ventilatory support.
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Enter PaO₂ and FiO₂
Enter arterial PaO₂ and FiO₂ to classify ARDS severity.
Oxygenation Parameters
fraction (0.21–1.0)
When to use
- Classifying acute hypoxaemic respiratory failure (ARDS Berlin definition)
- Monitoring ventilatory response — prone, PEEP, paralysis
- Guiding ECMO referral in severe ARDS (PF ratio <80)
- Serial assessment in ICU patients
Formula
PF Ratio = PaO₂ (mmHg) ÷ FiO₂
Berlin ARDS: requires PEEP ≥5 cmH₂O
Mild: PF 201–300
Moderate: PF 101–200
Severe: PF ≤100
References
- ARDS Definition Task Force. Acute Respiratory Distress Syndrome. JAMA. 2012;307(23):2526–33.