Question

Match the respiratory capacities to their correct calculations.

• A. TV + IRV
• B. ERV + IC
• C. TV + ERV
• D. ERV + RV

Answer 1

Functional Residual Capacity (FRC) = Expiratory Reserve Volume (ERV) + Residual Volume (RV)

FRC ensures that there is some air in the lungs at all times and gas exchange in the alveoli and the pulmonary capillaries occurs at all times, even between breaths.

Expiratory Capacity (EC) = Tidal Volume (TV) + Expiratory Reserve Volume (ERV)

Inspiratory Capacity (IC) = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV)

IC tells us how much additional air the lung can hold, and a decrease in this indicates lung disease.
e.g : in emphysema, the hyperinflation causes patients to have a higher resting lung volume

Vital Capacity (VC) = Expiratory Reserve Volume (ERV) + Inspiratory Capacity (IC)