Lung volumes

Vital capacity is the maximum amount of air that can be breathed out after breathing in as much air as possible. Taking part in regular aerobic exercise has been shown to increase a person's vital capacity.

Tidal volume is the amount of air breathed in with each normal breath. The average tidal volume is 0.5 litres (500 ml).

Total lung capacity is the total amount of air that the lungs can hold after the biggest possible breath in. The average total lung capacity is about 6 litres (6000 ml).

These volumes can be seen in this spirometry trace.

A man exhales into a tube, and the vital capacity, total lung capacity and tidal volume are measured in litres.

During exercise, tidal volume increases as the depth of breathing increases and the rate of breathing increases too. This has the effect of taking more oxygen into the body and removing more carbon dioxide.