PaO₂ / FiO₂ (P/F Ratio / Horowitz Index) & Berlin ARDS Severity Calculator

Calculate PaO₂/FiO₂ ratio and Berlin ARDS oxygenation tier.

PaO₂ / FiO₂ (P/F) Ratio
164 mmHg
Oxygenation Index (OI = FiO₂·MAP/PaO₂) 8.54 OI
a/A Ratio 26.75 %
Inspired Oxygen Fraction (FiO₂) 50 %
Inputs
⚡ Scenarios:
mmHg
Arterial oxygen tension PaO₂ in mmHg.
%
Inspired oxygen percentage FiO₂ (21% to 100%).
cmH₂O
Mean Airway Pressure (MAP) in cmH₂O for Oxygenation Index.
Results & Graph
PaO₂ / FiO₂ (P/F) Ratio
164 mmHg
Oxygenation Index (OI = FiO₂·MAP/PaO₂)
8.54 OI
a/A Ratio
26.75 %
Inspired Oxygen Fraction (FiO₂)
50 %

PaO₂ / FiO₂ (P/F) Ratio

Graph 1 • PaO₂/FiO₂ (P/F Ratio) • Domain Architecture & Live Telemetry Maps Arterial Pao2 Mm Hg, Inspired Fio2 Pct, Mean Airway Pressure Cm H2o through PaO₂/FiO₂ (P/F Ratio) Formula.
PaO₂/FiO₂ (P/F Ratio) • Clinical & Physiological Reference Scale Low / Baseline Target / Reference Elevated / Watch High / Action PaO₂ / FiO₂ (P/F) Ratio: 164 mmHg Oxygenation Index (OI = Fi 8.54 OI a/A Ratio 26.75 % Inspired Oxygen Fraction ( 50 %
Graph 2 • PaO₂ / FiO₂ (P/F) Ratio Across Arterial Pao2 Mm Hg Sweep (40% → 160%) Evaluates P/F_Ratio = PaO₂ (mmHg) / (FiO₂_% / 100); OxygenationIndex (OI) = (FiO across 7 operating points (current input highlighted).
0 mmHg 144.3 mmHg 288.6 mmHg 65.60 32.80mmHg 98.40 49.20mmHg 131.2 65.60mmHg 164 82mmHg 196.8 98.40mmHg 229.6 114.8mmHg 262.4 131.2mmHg
Graph 3 • Joint Sensitivity: Arterial Pao2 Mm Hg × Inspired Fio2 Pct Compares PaO₂ / FiO₂ (P/F) Ratio when Inspired Fio2 Pct is shifted +25% (solid) vs. −25% (dashed).
0 mmHg 156.3 mmHg 312.7 mmHg --- Inspired Fio2 Pct @ 75% 91.84 -30% 111.5 -15% 131.2 +0% 150.9 +15% 170.6 +30%
Summary: At PaO₂ 82 mmHg on 50% FiO₂, the P/F ratio is 164 mmHg (Moderate ARDS (101–200 mmHg)) and Oxygenation Index (OI) is 8.5.
Summary: At PaO₂ 82 mmHg on 50% FiO₂, the P/F ratio is 164 mmHg (Moderate ARDS (101–200 mmHg)) and Oxygenation Index (OI) is 8.5.
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Formula & Mathematical Methodology: PaO₂/FiO₂ (P/F Ratio) Formula

P/FRatio = PaO₂ mmHgFiO₂_% / 100
OxygenationIndex (OI) = (FiO₂_% × MeanAirwayPressure) / PaO₂
P/F_Ratio = PaO₂ (mmHg) / (FiO₂_% / 100); OxygenationIndex (OI) = (FiO₂_% × MeanAirwayPressure) / PaO₂
  • arterialPao2MmHg: Arterial Pao2 Mm Hg (mmHg)
  • inspiredFio2Pct: Inspired Fio2 Pct (%)
  • meanAirwayPressureCmH2o: Mean Airway Pressure Cm H2o (cmH₂O)

Rounding: Clinical scores round to statutory integer or decimal precision; physiological metrics round to 2 decimal places.

Worked Example: Clinical / Physiology Scenario: PaO₂/FiO₂ (P/F Ratio)

Calculate PaO₂/FiO₂ ratio and Berlin ARDS oxygenation tier.

  1. Enter lab values, anthropometric measurements, or performance test metrics.
  2. Evaluate the reference equation: P/F_Ratio = PaO₂ (mmHg) / (FiO₂_% / 100); OxygenationIndex (OI) = (FiO₂_% × MeanAirwayPressure) / PaO₂.
  3. Inspect the primary classification, supporting indices, and 3 SVG charts.
Result: Computes PaO₂/FiO₂ (P/F Ratio) via P/F_Ratio = PaO₂ (mmHg) / (FiO₂_% / 100); OxygenationIndex (OI) = (FiO₂_% × MeanAirwayPressure) / PaO₂.

Frequently Asked Questions

How does the PaO₂ / FiO₂ (P/F Ratio / Horowitz Index) & Berlin ARDS Severity Calculator compute its result?

It evaluates P/F_Ratio = PaO₂ (mmHg) / (FiO₂_% / 100); OxygenationIndex (OI) = (FiO₂_% × MeanAirwayPressure) / PaO₂ directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a target lab value or pace?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Are my health and biometric inputs kept private?

Yes. All calculations run 100% locally on your device with zero external transmission.

Health & Fitness · Pulmonary, Critical Care & Acid-Base

PaO₂ / FiO₂ (P/F Ratio / Horowitz Index) & Berlin ARDS Severity Calculator: inputs, method, and how to read the result

Calculate PaO₂/FiO₂ ratio and Berlin ARDS oxygenation tier.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Arterial Pao2 Mm Hg: Arterial oxygen tension PaO₂ in mmHg.
  • Inspired Fio2 Pct: Inspired oxygen percentage FiO₂ (21% to 100%).
  • Mean Airway Pressure Cm H2o: Mean Airway Pressure (MAP) in cmH₂O for Oxygenation Index.

What the calculation includes

With the default values shown, PaO₂ / FiO₂ (P/F) Ratio is 164 mmHg. The calculation follows PaO₂/FiO₂ (P/F Ratio) Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Arterial Pao2 Mm Hg from 82 mmHg to 90 mmHg changes PaO₂ / FiO₂ (P/F) Ratio from 164 mmHg to 180 mmHg. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses peer-reviewed clinical and sports physiology formulas.
  • For educational and informational reference only; clinical scores do not replace physician judgment or laboratory reference ranges.

Scope: Global Clinical & Sports Science Consensus Check the assumptions and limitations against your situation before relying on the estimate.

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