PaO₂/FiO₂ ratio (P/F)

CategoryRespiratory
Versionv1.0.0
Reviewed2026-07-25
ValidationIndependent clinical validation: pending

P/F ratio = PaO₂ ÷ FiO₂, with PaO₂ in mmHg (kPa is converted using 1 kPa = 7.50062 mmHg) and FiO₂ as a fraction from 0.21 to 1. A single dimensionless value is returned; it is displayed rounded to a whole number, but the interpretation bands are matched against the unrounded ratio. Bands follow the Berlin (2012) adult ARDS severity strata: ≤ 100 severe, > 100 to ≤ 200 moderate, > 200 to ≤ 300 mild, and > 300 above the ARDS oxygenation threshold.

Result	Interpretation
≤ 100	≤ 100 — Corresponds to the severe category in the Berlin ARDS definition (with PEEP or CPAP ≥ 5 cm H₂O).
>100 to 200	> 100 to ≤ 200 — Corresponds to the moderate category in the Berlin ARDS definition (with PEEP or CPAP ≥ 5 cm H₂O).
>200 to 300	> 200 to ≤ 300 — Corresponds to the mild category in the Berlin ARDS definition (with PEEP or CPAP ≥ 5 cm H₂O).
> 300	> 300 — Above the Berlin ARDS oxygenation threshold. Interpret in the full clinical context.

References

ARDS Definition Task Force; Ranieri VM, et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012;307(23):2526–2533.PMID 22797452 DOI 10.1001/jama.2012.5669
Emeriaud G, et al. Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric ARDS (PALICC-2). Pediatr Crit Care Med. 2023;24(2):143–168.PMID 36661420 DOI 10.1097/PCC.0000000000003147

Reproduction rights

Freely reproducible.Arithmetic ratio; Berlin/PALICC-2 numeric thresholds are facts, not copyrightable expression (pf-sf.md IP status).

Other respiratory scores

Important

For use by qualified health professionals as an informational and educational aid. It supports clinical judgment and does not replace it. Verify every result independently before making a clinical decision. This is not a medical device.