🫁 P/F Ratio (PaO₂/FiO₂, Berlin ARDS)
UseGrade hypoxaemia and classify ARDS severity.
SourceARDS Definition Task Force. Acute Respiratory Distress Syndrome: The Berlin Definition. JAMA 2012;3…
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
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Methodology · worked example, guidelines & full notes
The Berlin definition requires PEEP/CPAP ≥ 5 cmH₂O.
When to use
Grade hypoxaemia and classify ARDS severity.
How it works
P/F = PaO₂ ÷ FiO₂ (fraction). ≤ 300 mild, ≤ 200 moderate, ≤ 100 severe ARDS, measured on PEEP ≥ 5 cmH₂O.
Key points
- The Berlin definition requires PEEP/CPAP ≥ 5 cmH₂O.
- At altitude, multiply by (barometric pressure / 760).
- Lower ratios indicate worse oxygenation.
- Note: the 2024 global definition of ARDS (Matthay MA, et al. Am J Respir Crit Care Med 2024;209(1):37–47; doi:10.1164/rccm.202303-0558WS) builds on the Berlin definition by including high-flow nasal oxygen at ≥30 L/min, allowing SpO₂/FiO₂ ≤315 (when SpO₂ ≤97%) as an alternative to PaO₂/FiO₂ ≤300 to identify hypoxaemia, adding ultrasound as an imaging modality for bilateral opacities, and not requiring PEEP, oxygen flow rate or specific respiratory support devices in resource-limited settings; this tool still calculates Berlin P/F categories.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| PaO₂ | 80 mmHg |
|---|---|
| FiO₂ | 0.5 fraction |
→P/F ratio160mmHg
- Berlin category：Moderate ARDS
- Requires：PEEP/CPAP ≥ 5 cmH₂O for the ARDS definition.
Verification & sources · governance
FAQ
Frequently asked questions
- What are the limits and cautions when using P/F Ratio (PaO₂/FiO₂, Berlin ARDS)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- Does P/F Ratio (PaO₂/FiO₂, Berlin ARDS) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is P/F Ratio (PaO₂/FiO₂, Berlin ARDS) calculated in practice? Can you show a worked example?
- Inputs: PaO₂ 80 mmHg, FiO₂ 0.5 fraction → Result: P/F ratio 160 mmHg（Berlin category: Moderate ARDS, Requires: PEEP/CPAP ≥ 5 cmH₂O for the ARDS definition.）