Expiratory Reserve Volume is defined as

• A. The maximum amount of air that can be inspired after a tidal expiration.
• B. The volume of air that remains in the lungs after a maximal expiration.
• C. The volume of air exhaled in addition to tidal volume.
• D. The volume of air in excess of tidal volume that can be exhaled forcefully.

Answer: (D)

Expiratory Reserve Volume is the amount of air you can forcefully exhale after you have completed a normal exhale. After a tidal breath, there’s still air in the lungs, and you can push out this extra air with a strong exhale—that additional amount is the ERV. It’s different from residual volume, which is air left in the lungs after a maximal exhale and cannot be voluntarily expelled, and from inspiratory reserve volume, which is the extra air you can inhale beyond a normal inhalation. So the ERV is the volume of air in excess of tidal volume that can be exhaled forcefully. In healthy adults, this is typically several hundred milliliters up to about a liter.