What is the volume of additional air that can be forcibly exhaled after normal exhalation called?

The volume of additional air that can be forcibly exhaled after normal exhalation is known as the expiratory reserve volume (ERV). This volume represents the capacity of the lungs to expel more air than what is typically exhaled during a normal breath.

After a normal exhalation, there remains a significant amount of air in the lungs to prevent collapse and maintain the necessary gas exchange functionalities. The ERV indicates the amount of air that can be exhaled with effort beyond this normal tidal breathing.

In contrast, inspiratory reserve volume refers to the amount of air that can be inhaled after taking a normal breath, which is not relevant to exhalation; tidal volume is the amount of air inhaled or exhaled in a normal breath; and vital capacity measures the total amount of air that can be exhaled after a deep inhalation, which includes both the tidal volume and both reserve volumes but does not specify the additional air that can be exhaled specifically post-normal expiration. Therefore, the only term that directly describes the additional air that can be forcibly exhaled after a normal exhalation is expiratory reserve volume.