Predicted body weight & protective tidal volume
Tidal volume in mL from predicted body weight (ARDSNet formula) for lung-protective ventilation
- ESICM 2023 ARDS guideline (4–8 mL/kg PBW)
Sources last checked: 2026-10-13
Predicted body weight & protective tidal volume
Tidal volume in mL from predicted body weight (ARDSNet formula) for lung-protective ventilation
Uses height, never actual weight. Measure or estimate height carefully (e.g. knee height or ulna length if bedridden). The ARDSNet protocol started at 6 mL/kg PBW and adjusted tidal volume to a plateau pressure ≤ 30 cmH₂O.
What is the Predicted body weight & protective tidal volume?
Predicted body weight (PBW) estimates lean body weight from sex and height, and is the reference for setting tidal volume in lung-protective ventilation. The formula comes from the ARDS Network trial (2000), in which ventilation at 6 mL/kg PBW with plateau pressure ≤ 30 cmH₂O reduced mortality compared with 12 mL/kg. The ESICM 2023 ARDS guideline recommends tidal volumes of 4–8 mL/kg PBW.
When to use it
- Setting the initial tidal volume in ARDS or at risk of ARDS
- Checking whether a patient's current tidal volume is lung-protective
- Normalising driving pressure or compliance to body size
When not to use it
- Children — paediatric ventilation uses different references
- With actual body weight entered in place of height — PBW must come from height
How it is calculated
PBW (kg), men = 50 + 0.91 × (height cm − 152.4) PBW (kg), women = 45.5 + 0.91 × (height cm − 152.4) Tidal volume (mL) = PBW × target mL/kg
Clinical pearls and limitations
- Uses height, never actual weight. Measure or estimate height carefully (e.g. knee height or ulna length if bedridden). The ARDSNet protocol started at 6 mL/kg PBW and adjusted tidal volume to a plateau pressure ≤ 30 cmH₂O.
- Obese patients do not have bigger lungs: always use PBW, never actual weight.
- Women and short patients are most often over-ventilated when tidal volume is chosen by eye.
- Tidal volume is interpreted together with plateau pressure (≤ 30 cmH₂O in the ARDSNet protocol) and driving pressure (plateau − PEEP).
- If the patient cannot be measured standing, estimate height from knee height or ulna length rather than guessing.
Frequently asked questions
What is the ARDSNet predicted body weight formula?
Men: 50 + 0.91 × (height in cm − 152.4). Women: 45.5 + 0.91 × (height in cm − 152.4). The result is in kg.
What tidal volume for a 180 cm man?
PBW is about 75 kg, so 6 mL/kg gives about 450 mL and 8 mL/kg about 600 mL.
Is predicted body weight the same as ideal body weight?
The ARDSNet PBW equation is essentially the Devine ideal-body-weight formula rewritten for centimetres; the terms are often used interchangeably in ventilation.
Should tidal volume be 6 or 8 mL/kg?
The ARDSNet protocol targeted 6 mL/kg PBW; the ESICM 2023 guideline recommends 4–8 mL/kg PBW, adjusted to plateau and driving pressure.
Evidence and guidelines
- Primary source: Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342(18):1301-1308.
- Grasselli G et al. ESICM guidelines on ARDS. Intensive Care Med 2023;49(7):727-759 — Recommendation 5.1: low tidal volume ventilation, 4–8 mL/kg PBW.
- PBW formula (ARDSNet) as stated in: Respiratory mechanics modifies the impact of ventilator settings on clinical outcome. Intensive Care Med 2026;52(10):2071-2084.
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