Define tidal volume.

• A. The amount of air inhaled or exhaled with normal breathing
• B. The total air volume in lungs after maximal inspiration
• C. The amount of air remaining after forced expiration
• D. The air taken in during a deep breath

Answer: (A)

Tidal volume is the amount of air moved in or out of the lungs during a normal, resting breath. It represents the air you inhale and exhale with each regular breath, not the total lung capacity or the air you can forcefully move. In a typical adult, this is about 500 mL per breath, though it varies with body size and other factors.

This is distinct from the total air in the lungs after a maximal inhale (that’s the total lung capacity), the air remaining after a forced exhale (residual volume), and the air taken in during a deep breath (inspiratory reserve volume).