Lung Volumes and Capacities
Lung volumes refer to basic volumes of the lung, whereas lung capacities are the sum of two or more basic lung volumes.
The following are the four lung volumes:
Tidal Volume (VT):
volume of gas inspired or expired during a normal quiet breathing. (500ml)Inspiratory Reserve Volume (IRV):
volume of gas that can be fully inspired from the end of quiet inspiration. (3000ml)Expiratory Reserve Volume (ERV):
volume of gas that can be fully expired from the end of quiet expiration. (1100ml)Residual Volume (RV):
volume of air in lungs that cannot be forcefully expired. This volume cannot be directly measured and indirect measurements are usually utilised. (1200ml)
The four lung capacities are:
Vital Capacity (VC)
: maximum volume of gas that can be expired after a maximal inspiration (IRV + VT + ERV). (4600ml)Inspiratory Capacity (IC):
the maximal volume of air that can be inspired from quiet end-expiration (VT + IRV). (3500ml)Functional Residual Capacity (FRC):
total volume of air in the lung at end of normal end-expiration (ERV + RV). (2300ml)Total Lung Capacity (TLC)
: total volume of gas in lung at maximal end- inspiration (IRV + VT + ERV + RV). (5800ml)