What volumes should the respiratory therapist examine to calculate vital capacity?

Vital capacity (VC) is a key lung volume that represents the maximum amount of air a person can forcibly exhale after a maximum inhalation. To calculate vital capacity, one must combine specific components of lung volumes.

The correct calculation for vital capacity involves adding the inspiratory reserve volume (IRV), the tidal volume (VT), and the expiratory reserve volume (ERV). This combination reflects the total volume of air that can be moved in and out of the lungs. By summing IRV, which is the additional air that can be inhaled after a normal inhalation, the tidal volume, which is the air exchanged in normal breath, and the expiratory reserve volume, which is the additional air that can be exhaled after a normal exhalation, you get a comprehensive measurement of the vital capacity.

This calculation underscores the dynamic potential of lung function, highlighting how much air can be inhaled and exhaled beyond the normal resting states. Thus, the correct answer effectively captures those volumes necessary to determine vital capacity accurately.