Question

The amount of air that moves in or out of the lungs with each respiratory cycle is:

• A. Inspiratory reserve volume
• B. Expiratory reserve volume
• C. Tidal volume
• D. Residual volume

Answer 1

The Correct Option is C

The correct option is (C): Tidal volume.

Answer 2

The question asks for the term describing the volume of air that moves in and out of the lungs during one normal, quiet breath. Let's look at each of the standard lung volumes to work out which one fits.

1. Inspiratory reserve volume: This is the extra air a person can breathe in forcibly after a normal inspiration, on top of the tidal volume. It only comes into play during deep or forced breathing, not a regular cycle.
2. Expiratory reserve volume: This is the extra air that can be forcibly breathed out after a normal expiration. Like the inspiratory reserve, it is only used during forced breathing and is not part of a normal quiet breath.
3. Tidal volume: This is defined as the volume of air inspired or expired in a single normal breath during quiet, resting breathing. In a healthy adult it is about 500 mL per breath. This matches the description in the question exactly.
4. Residual volume: This is the air that stays in the lungs even after the most forceful expiration possible. It can never be exhaled and so is never part of the air that moves in or out during breathing.

Only tidal volume describes air that is actually exchanged with each ordinary respiratory cycle; the other volumes describe reserves or air that is not exchanged at all.

Therefore, the correct answer is Tidal volume.