The correct option is Expiratory Capacity.
Explanation
Respiratory capacities are derived by summing specific lung volumes to assess pulmonary function. These capacities quantify the maximum amount of air that can be inhaled or exhaled under specific conditions.
Analysis of Options:
- Expiratory Capacity (EC): This is defined as the total volume of air a person can expire after a normal inspiration. It is the sum of Tidal Volume (TV) and Expiratory Reserve Volume (ERV). Mathematically, EC = TV + ERV.
- Inspiratory Capacity (IC): This represents the total volume of air a person can inspire after a normal expiration. It is the sum of Tidal Volume and Inspiratory Reserve Volume (IC = TV + IRV).
- Functional Residual Capacity (FRC): This is the volume of air remaining in the lungs after a normal expiration. It is the sum of Expiratory Reserve Volume and Residual Volume (FRC = ERV + RV).
- Vital Capacity (VC): This is the maximum volume of air a person can breathe in after a forced expiration. It includes Expiratory Reserve Volume, Tidal Volume, and Inspiratory Reserve Volume (VC = ERV + TV + IRV).
Key Takeaway: Expiratory Capacity specifically measures the total expiratory potential following a normal breath in, combining the air moved during normal breathing (TV) with the additional air that can be forcibly exhaled (ERV).