How is Total Lung Capacity (TLC) calculated?

Total Lung Capacity (TLC) is calculated by adding the Vital Capacity (VC) and the Residual Volume (RV). Vital Capacity is the maximum amount of air a person can exhale after a maximum inhalation, while Residual Volume is the amount of air that remains in the lungs after a forceful exhalation. Therefore, TLC effectively represents the total volume of air in the lungs after maximum inhalation.

This option correctly illustrates that TLC encompasses both the air that can be actively controlled during breathing (as captured in the Vital Capacity) and the air that remains in the lungs at all times, which is vital for maintaining lung function and gas exchange even when a person is not inhaling or exhaling.

In contrast, other options do not provide the combination of volumes needed to calculate TLC. For example, combining ERV with RV only accounts for part of lung air and excluding the vital capacity limits the total volume measured. Similarly, including TV and FEV does not contribute to a meaningful measure of total lung capacity, as these terms refer to specific volumes unrelated to the calculation of total lung capacity.