What is the normal tidal volume range in ml/kg?

• A. 3-4 ml/kg
• B. 4-5 ml/kg
• C. 5-7 ml/kg
• D. 7-9 ml/kg

Answer: (C)

Tidal volume is assessed relative to predicted body weight, not actual weight, because lung size correlates with height and sex. In a healthy adult, the normal breathing volume per breath falls roughly in the middle of five to seven milliliters for every kilogram of predicted body weight, with about six milliliters per kilogram often used as a practical target. This balance provides adequate ventilation while reducing the risk of overstretching the lungs.

Choosing values much lower, like three to four milliliters per kilogram, would typically under-ventilate and could cause CO2 retention. Values at seven to nine milliliters per kilogram are on the higher end and increase the risk of ventilator-induced lung injury due to overdistension. Therefore, five to seven milliliters per kilogram best represents normal tidal volume.