Anaesthesia / Critical Care Respiratory Emergency Medicine Strong — JAMA 2012 (Berlin Definition)

P/F Ratio (Horowitz Index)

PaO₂/FiO₂ ratio. Quantifies oxygenation efficiency and is the cornerstone of the Berlin ARDS Definition. Normal >400. Enter PaO₂ from ABG and FiO₂ as a percentage.

Score interpretation

Normal Oxygenation ≥ 301

P/F Ratio >300: Normal oxygenation. ARDS criteria not met.

→ Routine monitoring. Continue current respiratory support. No ARDS classification required.

Mild ARDS 201–300

P/F Ratio 201–300 with PEEP/CPAP ≥5 cmH₂O: Mild ARDS (Berlin Definition).

→ Lung-protective ventilation: Vt 6 ml/kg IBW, plateau pressure <30 cmH₂O. Treat underlying cause (sepsis, aspiration, pneumonia). Optimise PEEP. Reassess in 12–24 hours.

Moderate ARDS 101–200

P/F Ratio 101–200 with PEEP ≥5 cmH₂O: Moderate ARDS (Berlin Definition). Mortality ~32%.

→ Lung-protective ventilation (Vt 6 ml/kg IBW). Higher PEEP strategy. Prone positioning for ≥16 hours/day. Neuromuscular blockade (48 hours) if severe dyssynchrony. Consider ECMO referral if deteriorating.

Severe ARDS 0–100

P/F Ratio ≤100 with PEEP ≥5 cmH₂O: Severe ARDS (Berlin Definition). Mortality ~45%.

→ Mandatory prone positioning (≥16 hours/day). High PEEP strategy. Neuromuscular blockade. Early ECMO referral to specialist centre if P/F <80 or refractory to conventional therapy. Specialist intensivist + respiratory physician. Goals of care discussion.

Interpretation bands for the P/F Ratio. Apply clinical judgement and local guidance.

References

ARDS Definition Task Force; Ranieri VM et al. Acute Respiratory Distress Syndrome: The Berlin Definition. JAMA. 2012;307(23):2526–2533.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Silverman-Anderson Retraction Score · Respiratory Assessment

Drugs

Pathways

Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.

Score interpretation

References

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