Lung ventilation, volumes, and measurement

Overview of ventilation
Ventilation is the exchange of air between the lungs and the surroundings. Several terms are used to describe ventilation that are based on the root pnoea (breathing) and various prefixes:

Pulmonary volumes
Several parameters regarding the volume of air that flows between the lungs and surroundings can be measured. These include Tidal volume: amount of air that flows into the lungs during inspiration or out of them during expiration, VT = 500ml

Inspiratory reserve volume (IRV): The amount of air that is inspired in maximal inspiratory effort, in addition to the amount of tidal volume. IRV= 3L.

Expiratory reserve volume (ERV): The volume expelled by an active expiratory effort after passive expiration, ERV= 1.7L.

Residual volume (RV): The air that stays in the lungs after maximal expiratory effort (after ERV), RV= 1.2L.

Inspiratory capacity (IC): Maximum inhaled air after normal expiration, IC = + IRV

Vital capacity (VC): Maximum inspiration and after maximum expiration. Around 5L.


 * VC = IRV + TV + ERV
 * VC = IC + ERV since IC=Vt + IRV

Expiratory capacity: maximum exhaled air after normal inspiration.

Functional residual capacity (FRC): The amount of air that remains in the lungs at the end of normal expiration. FRC = ERV + RV

Total lung capacity: The maximum volume the lungs can contain, around 6L.


 * TLC = VC + RV
 * TLC = IC + FRC

One-second forced expiratory volume (FEV1): maximum volume forcibly expired after max. possible inspiration over one second)