Air-Exchange Physiology

Volumes of air exchange in breathing can be measured with a spirometer.

Tidal Volume (TV): The tidal volume is the amount of air normally breathed in and out with each breath (about 500 ml).

Vital Capacity (VC): The largest amount of air that we can breathe in and out in one inspiration and expiration is known as the vital capacity. In normal young men, this is about 4800 ml.

Expiratory Reserve Volume (ERV): The amount of air that can be forcibly exhaled after expiring the tidal volume is called expiratory reserve volume.

Inspiratory Reserve Volume (IRV): The amount of air that can be forcible inhaled after a normal inspiration is called the inspiratory reserve volume.

Residual Volume (RV): The air that remains in the lungs after the most forceful expiration is called the residual volume.