A large patient, 140 kg, intubated for severe respiratory distress; using a lung protective strategy, which tidal volume is most appropriate?

• A. 470 mL
• B. 700 mL
• C. 250 mL
• D. 285 mL

Answer: (A)

Lung protective ventilation sets tidal volume based on predicted body weight, not actual weight, to minimize volutrauma. The goal is typically about 6 mL per kilogram of predicted body weight (PBW), with plateau pressures kept as low as possible (often ≤30 cm H2O). For a very large patient, PBW is still used, and even though the actual weight is 140 kg, the VT is calculated from PBW, not from body mass.

If we estimate PBW for a tall or average-height adult to be around 70–75 kg, a VT near 6 mL/kg would be roughly 420–450 mL. The 470 mL option is the closest to that target, aligning with the lung-protective aim of about 6 mL/kg PBW. The other volumes are either too high (700 mL) or closer to 4 mL/kg PBW, which is not the standard target in most ARDS or severe respiratory distress scenarios, where the emphasis is on limiting volutrauma with ~6 mL/kg PBW.