What is the normal spontaneous tidal volume (Vt) in ml/kg?

• A. 5-8 ml/kg
• B. 10-12 ml/kg
• C. 1-3 ml/kg
• D. 8-10 ml/kg

Answer: (A)

Normal spontaneous tidal volume is about 5 to 8 mL per kilogram of ideal body weight. This range reflects a breath that provides enough air for gas exchange without overdistending the lungs. Using ideal body weight matters because lung size correlates with height, not actual weight, so the per‑kg dosing helps prevent both under-ventilation and injury from too large a breath.

For example, a 70 kg person would typically have roughly 350–560 mL per breath at rest. Tidal volumes much lower than this (1–3 mL/kg) risk hypoventilation and CO2 retention, while volumes at the high end (8–10 mL/kg or more) raise the risk of volutrauma and hemodynamic compromise. The standard, commonly accepted range to describe normal spontaneous Vt is 5–8 mL/kg.