Lung-protective ventilation sets tidal volume per kilogram of predicted body weight, which is calculated from height and sex, not from actual weight. A tall thin patient and a short obese patient of the same weight have very different lung sizes.
A common target is about 6–8 mL/kg predicted body weight, with plateau pressure kept below 30 cmH2O and driving pressure as low as practical. In brain injury, carbon dioxide also matters: avoid both hypercapnia, which raises intracranial pressure, and unplanned hyperventilation, which can cause cerebral ischaemia.
- Measure or estimate height and calculate predicted body weight at intubation.
- Start at about 6–8 mL/kg predicted body weight.
- Check plateau and driving pressure after setting the ventilator.
- In brain injury, set a carbon dioxide target and check a blood gas early.
- Record the predicted body weight on the chart so every shift uses the same figure.
Why it matters
Tidal volumes set on actual weight are a common, avoidable cause of injurious ventilation, especially in women and short patients.
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