Expiratory reserve volume is best described as which of the following?

• A. Air remaining after residual volume.
• B. The amount of air that cannot be forcibly exhaled.
• C. The amount of air that can be forcibly inhaled after normal inspiration.
• D. The amount of air that can be forcibly exhaled.

Answer: (D)

Expiratory reserve volume is the extra amount of air you can forcefully exhale after completing a normal, relaxed exhalation. This means after you breathe out normally, you can still push out more air; that additional quantity is the expiratory reserve volume. That’s why describing it as the amount of air that can be forcibly exhaled fits best. It’s not air that cannot be exhaled (that would be residual volume), nor is it the air you can inhale after a normal breath (that’s inspiratory reserve volume). ERV combines with other volumes to help define overall lung capacity, such as vital capacity and functional residual capacity.