Tidal volume is defined as

• A. The maximum air exhaled after a deep inhalation.
• B. The air remaining in the lungs after maximal exhalation.
• C. The total amount of air that can be inspired.
• D. The volume of air breathed in and out in any one breath.

Answer: (D)

Tidal volume is the amount of air moved in and out with each normal breath. It reflects the volume exchanged during quiet breathing, not the maximum amount you can inhale or exhale or the air still remaining in the lungs after a full breath. In a healthy adult, this is typically about 500 mL per breath. It’s different from other lung volumes: residual volume is air left after a maximal exhale; inspiratory reserve volume is the extra air you can inhale beyond a normal inhalation; expiratory reserve volume is the extra air you can exhale beyond a normal exhalation; vital capacity is the maximum air you can exhale after a full inhalation. So the description of the volume of air breathed in and out in any one breath aligns with tidal volume.