🫁 P/F Ratio (PaO₂/FiO₂, Berlin ARDS)
Calculate the PaO₂/FiO₂ (P/F) ratio for ARDS severity under the Berlin definition.
Clinical takeaway
The Berlin definition requires PEEP/CPAP ≥ 5 cmH₂O.
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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.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
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.
Frequently asked questions
- What is P/F Ratio (PaO₂/FiO₂, Berlin ARDS)?
- Calculate the PaO₂/FiO₂ (P/F) ratio for ARDS severity under the Berlin definition.
- How is P/F Ratio (PaO₂/FiO₂, Berlin ARDS) calculated? What is the core formula?
- P/F = PaO₂ ÷ FiO₂ (fraction). ≤ 300 mild, ≤ 200 moderate, ≤ 100 severe ARDS, measured on PEEP ≥ 5 cmH₂O.
- When is P/F Ratio (PaO₂/FiO₂, Berlin ARDS) used?
- Grade hypoxaemia and classify ARDS severity.
- What are the key clinical points for P/F Ratio (PaO₂/FiO₂, Berlin ARDS)?
- The Berlin definition requires PEEP/CPAP ≥ 5 cmH₂O. At altitude, multiply by (barometric pressure / 760). Lower ratios indicate worse oxygenation.
- 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.
- 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.）