Berlin definition of ARDS: the criteria and severity bands (2012)

The Berlin definition of ARDS (acute respiratory distress syndrome) has two parts. Three clinical criteria must all be met, and then the PaO2/FiO2 ratio, measured with enough positive pressure, sets the severity: mild, moderate or severe. This calculator applies the 2012 rule to the findings and ratio you supply and returns the severity.

Not a medical device. Not a diagnosis or dosing recommendation.

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Respiratory calculators
ARDS Definition Task Force; Ranieri VM et al. · 2012
Worked examples
Frequently asked questions

What is the Berlin definition of ARDS?

It's a consensus definition written by the ARDS Definition Task Force and published in JAMA. The clinical part asks about timing, chest imaging and the origin of the respiratory failure. The oxygenation part grades severity by PaO2/FiO2, and it counts when the patient is on PEEP or CPAP of at least 5 cm H2O.

Magent doesn't read images, take a history or work out the ratio from PaO2 and FiO2. The PaO2/FiO2 is supplied by the caller.

The Berlin definition rule

clinical box = onset within 1 week
             and bilateral opacities not fully explained
             and respiratory failure not fully explained
                 by cardiac failure or fluid overload

if clinical box:
  severe    PaO2/FiO2 ≤ 100            and PEEP ≥ 5
  moderate  100 < PaO2/FiO2 ≤ 200      and PEEP ≥ 5
  mild      200 < PaO2/FiO2 ≤ 300      and PEEP or CPAP ≥ 5
otherwise none

Exact expression the calculator uses:

clinical_box iff onset_within_1_week and bilateral_opacities_not_fully_explained and origin_not_fully_hf_or_fluid; severe iff clinical_box and pf_ratio <= 100 and peep_ge_5; moderate iff clinical_box and 100 < pf_ratio <= 200 and peep_ge_5; mild iff clinical_box and 200 < pf_ratio <= 300 and (peep_ge_5 or cpap_ge_5); berlin_ards iff severity is mild, moderate, or severe; else none (Ranieri 2012 Berlin Definition)

Inputs

Input	Meaning
`onset_within_1_week`	Onset within 1 week of a known clinical insult or new or worsening respiratory symptoms
`bilateral_opacities_not_fully_explained`	Bilateral opacities not fully explained by effusions, collapse or nodules
`origin_not_fully_hf_or_fluid`	Respiratory failure not fully explained by cardiac failure or fluid overload
`peep_ge_5`	PEEP of 5 cm H2O or more
`cpap_ge_5`	CPAP of 5 cm H2O or more
`pf_ratio`	PaO2/FiO2 in mm Hg, 20 to 800

How the calculation works

Check the clinical box. All three clinical inputs must be true. If any is false, severity is none.
Grade by PaO2/FiO2:

PaO2/FiO2 (mm Hg)	Pressure needed	Severity
100 or less	PEEP 5 or more	`severe`
Above 100 up to 200	PEEP 5 or more	`moderate`
Above 200 up to 300	PEEP or CPAP 5 or more	`mild`
Above 300, or pressure not met		`none`

Set the flag. berlin_ards is true for mild, moderate or severe.

CPAP counts for the mild band and nothing else. A ratio in the moderate or severe range with CPAP and no PEEP returns none.

Worked examples

These use Magent's own expected values for the calculator. In each, the three clinical criteria are all met.

Example 1: PEEP with a ratio of 150

The clinical box is met.
150 is above 100 and at most 200, and PEEP is 5 or more.
Severity moderate.

Example 2: PEEP with a ratio of 250

The clinical box is met.
250 is above 200 and at most 300, and PEEP is 5 or more.
Severity mild.

Example 3: CPAP without PEEP and a ratio of 150

The clinical box is met.
150 is in the moderate range, but moderate needs PEEP.
CPAP counts for the mild band, and 150 isn't in the mild range.
Severity none, so berlin_ards is false.

History of the Berlin definition

The ARDS Definition Task Force published "Acute respiratory distress syndrome: the Berlin Definition" in JAMA in 2012. The three clinical criteria and the three severity bands the calculator uses come from that paper.

When it's used

When a team records whether a patient with acute respiratory failure meets the Berlin criteria and at what severity, for notes, audit or research.

Where it's used

Intensive care units and ARDS research.

Who uses it

Intensivists, critical care teams and researchers. The calculator applies the rule to their findings.

Limits of the calculation

The clinical criteria are judgements, entered as given.
The PaO2/FiO2 must be correct and taken on the stated pressure. The calculator doesn't check either.
A severity label isn't a finding about cause, and the calculator gives no ventilator advice.
This page doesn't say what a result means for a particular person.

Clinical decisions belong to a qualified clinician who knows the patient.

SpO2/FiO2 ratio divides pulse-oximeter SpO2 by FiO2. The Berlin definition grades severity on the arterial PaO2/FiO2 instead.

Glossary

PaO2/FiO2: arterial oxygen in mm Hg divided by the inspired oxygen fraction.
PEEP: positive end-expiratory pressure, from a ventilator.
CPAP: continuous positive airway pressure.
Bilateral opacities: shadowing on both sides of a chest image.

Common mistakes

Grading with CPAP above the mild band. Moderate and severe need PEEP.
Grading without the clinical box. If any clinical criterion is missing, the result is none.
Entering PaO2 alone. The input is the ratio.

Source

ARDS Definition Task Force; Ranieri VM, et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012;307(23):2526-2533. DOI: 10.1001/jama.2012.5669. PMID: 22797452

Frequently asked questions

What are the Berlin ARDS criteria?

Onset within 1 week, bilateral opacities not fully explained by effusions, collapse or nodules, and respiratory failure not fully explained by cardiac failure or fluid overload.

What are the Berlin severity bands?

Severe at a PaO2/FiO2 of 100 or less, moderate above 100 up to 200 and mild above 200 up to 300, each with at least 5 cm H2O of pressure.

Why isn't CPAP enough for moderate ARDS?

The 2012 rule accepts CPAP for the mild band. Moderate and severe need PEEP.

Does the calculator work out the PaO2/FiO2?

No. You enter the ratio.