What is tidal volume?

• A. The amount of air inhaled and exhaled during a normal breathing cycle.
• B. The maximum amount of air the lungs can hold after a deep inhalation.
• C. The total air in the lungs after a forced expiration.
• D. The air left in the lungs after a normal exhalation.

Answer: (A)

Tidal volume is the amount of air you move into and out of your lungs during a normal, at-rest breath. In a healthy adult, this is about 500 mL per breath, though it varies with body size and conditioning. It’s the actual air exchanged with each quiet inspiration and expiration, not the total capacity of the lungs or the air that remains after breathing out.

To place it in context with other lung volumes: the maximum amount the lungs can hold after a deep inhalation is the total lung capacity. The air left in the lungs after a forced expiration is the residual volume. The air left after a normal exhalation is the functional residual capacity. Tidal volume specifically describes the typical, quiet-breath air exchange, making it the best choice.