ICU Map

PaO2/FiO2 Ratio

Grades hypoxemia severity using the 2012 Berlin ARDS oxygenation bands when PaO2/FiO2 is measured with PEEP/CPAP ≥5 cmH2O. The newer Global ARDS Definition also recognizes nonintubated ARDS on HFNO ≥30 L/min and additional pathways, so this calculator should not be used as the sole modern ARDS diagnostic tool.

Formula

P/F ratio = PaO2 / FiO2

Result

Enter all values to see the result.

Limitations

  • The severity bands shown here are the Berlin 2012 PaO2/FiO2 categories and assume PEEP/CPAP ≥5 cmH2O. The Global ARDS Definition expands diagnosis to selected nonintubated patients (including HFNO ≥30 L/min), so absence of Berlin-compatible PEEP does not by itself exclude ARDS under the newer framework.
  • Does not itself establish an ARDS diagnosis; the Berlin definition's timing, imaging, and cardiac-exclusion criteria must also be met.
  • FiO2 is often only approximately known on non-invasive or high-flow oxygen devices, which limits precision outside invasive mechanical ventilation.

References

  • ARDS Definition Task Force. Berlin Definition of ARDS. JAMA 2012.
  • Matthay MA, et al. A New Global Definition of Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med. 2024;209:37-47.

Clinical Context & Relevant Topics (4)

Disease Reference
Acute Respiratory Distress Syndrome

Acute, diffuse inflammatory lung injury causing hypoxemia and bilateral infiltrates not fully explained by cardiac failure or fluid overload.

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Hypoxemic Respiratory Failure

Pathophysiologic mechanisms (shunt vs V/Q mismatch), dynamic ROX index trajectories, P-SILI prevention, and evidence-based oxygen escalation ladders.

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Severe Community-Acquired Pneumonia (Severe CAP)

IDSA/ATS severe CAP criteria, rapid microbiology, targeted empiric antimicrobial regimens, and landmark adjunctive hydrocortisone evidence (CAPE COD).

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Respiratory Failure: Basic Principles

Core taxonomy (Types I–IV), alveolar gas exchange physiology, work-of-breathing mechanics, and escalation thresholds in acute respiratory failure.

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Relevant Clinical Pathways (9)

Decision Protocols
Mechanical Ventilation Initiation Workflow

From post-intubation verification and lung-protective settings to mechanics optimization.

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Mechanical Ventilation Liberation & Weaning

From readiness screening and spontaneous breathing trials to extubation and post-extubation support.

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