Lung Volumes and Capacities

PFT

TLC Total lung capacity

is the maximum amount of air the lungs can hold after a deep inhalation, including the vital capacity and residual volume.

TLC=Inspiratory Reserve Volume (IRV) + Tidal Volume (TV) + Expiratory Reserve Volume (ERV) + Residual Volume (RV)

Inspiratory reserve volume (IRV)

is the maximum amount of air that can be inhaled after a normal inhalation, representing the additional air that can be drawn into the lungs beyond tidal volume.

Tidal Volume (Vt)

is the amount of air inhaled or exhaled during normal breathing, typically around 500 mL per breath in adults.

Inspiratory Capacity (IC) 

is the maximum amount of air that can be inhaled after a normal expiration, calculated as the sum of tidal volume and inspiratory reserve volume.

Inspiratory Reserve Volume (IRV) + Tidal Volume (VT)= Inspiratory Capacity (IC)

Expiratory Reserve Volume (ERV) 

is the maximum amount of air that can be exhaled after the end of a normal expiration, representing the additional air that can be expelled from the lungs.

Residential Volume (RV)

is the amount of air remaining in the lungs after a maximum exhalation, which prevents lung collapse and assists in gas exchange.

Functional Residual Capacity (FRC)

is the total amount of air left in the lungs after a normal expiration, calculated as the sum of expiratory reserve volume and residual volume.

Expiratory reserve volume (ERV) + Residual volume (RV) = Functional Residual Volume

Vital Capacity (VC) 

is the maximum amount of air a person can exhale after a maximum inhalation. It represents the total volume of air that can be moved in and out of the lungs.

Inspiratory Reserve Volume (IRV) + Tidal Volume (VT) + Expiratory Reserve Volume (ERV) = Vital Capacity (VC)