Functional residual capacity (FRC)

Functional residual capacity is the volume of air present in the lungs at the end of passive expiration where the opposing elastic recoil forces of the lungs and chest wall are balanced. FRC is a critical concept in respiratory physiology, representing a pulmonary equilibrium point and is the sum of expiratory reserve volume (ERV) and residual volume (RV). It is essential as a clinical measurement for assessing lung mechanics and diseases, but is not a molecule, receptor, or direct therapeutic target. In summary, "Functional residual capacity" is a physiological measurement, not a molecular or therapeutic target. Its inclusion as a target molecule/receptor is an error.