What does the Functional Residual Capacity (FRC) refer to?

Functional Residual Capacity (FRC) refers to the volume of air that remains in the lungs after a normal exhalation. This volume is significant because it represents the balance point in the respiratory cycle where the forces of the lungs trying to collapse and the chest wall trying to expand are equal. FRC includes the Residual Volume (the air remaining in the lungs after a maximal exhalation) and the Expiratory Reserve Volume (the additional air that can be forcefully exhaled after a normal exhalation). This capacity is important for maintaining adequate gas exchange and preventing the alveoli from fully collapsing.

Understanding FRC is crucial in various clinical contexts, particularly in assessing lung function and the effectiveness of gas exchange in patients with respiratory conditions. Knowing this helps emphasize the importance of maintaining a certain volume of air in the lungs even when not actively breathing in or out.