In lung-protective ventilation, tidal volume is calculated based on which weight measure?

• A. Ideal body weight
• B. Actual body weight
• C. Lean body weight
• D. Total body weight

Answer: (A)

In lung-protective ventilation, the tidal volume is set to reflect the size of the lungs, not the patient’s total mass. The size of the lungs correlates best with height and sex, which is captured by using ideal (predicted) body weight to guide tidal volume calculations. This approach helps keep ventilation gentle—typically about 6 mL per kilogram of ideal body weight—minimizing the risk of volutrauma and barotrauma.

Using actual body weight can overestimate lung size in obese patients, leading to unnecessarily large tidal volumes. Lean body weight and total body weight don’t map reliably to lung capacity. So, ideal body weight is the appropriate measure to base tidal volume on.