Functional residual capacity
Description
Functional Residual Capacity (FRC) is the volume of air present in the lungs, specifically the parenchyma tissues, at the end of passive expiration. At FRC, the elastic recoil forces of the lungs and chest wall are equal but opposite and there is no exertion by the diaphragm or other respiratory muscles.
FRC is the sum of Expiratory Reserve Volume (ERV) and Residual Volume (RV) and measures approximately 2400 mL in an 80 kg, average-sized male.
Variables
| FRC | Functional residual capacity: : the volume in the lungs at the end-expiratory position (ml) |
| ERV | Expiratory reserve volume: the maximal volume of air that can be exhaled from the end-expiratory position (ml) |
| RV | Residual volume: the volume of air remaining in the lungs after a maximal exhalation (ml) |