American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Which lung volume is calculated as FRC?

1. TV + RV

2. ERV + RV

3. RV + IC

4. FVC + ERV

The correct answer is: ERV + RV

Functional Residual Capacity (FRC) is defined as the volume of air present in the lungs at the end of passive expiration. FRC is specifically comprised of two components: the expiratory reserve volume (ERV), which is the maximum amount of air that can be exhaled after a normal expiration, and the residual volume (RV), which is the volume of air remaining in the lungs after a maximal exhalation. The calculation of FRC can be represented as the sum of ERV and RV, which is why this choice is the correct answer. Each of these components is crucial for understanding lung function, as they contribute to the total volume of air available in the lungs during the respiratory cycle. The other answer choices do not accurately represent the components of FRC. For example, the combination of tidal volume (TV) with residual volume (RV) does not correctly reflect FRC, as tidal volume represents the amount of air inhaled or exhaled during normal breathing, which is distinct from the capacities counted in FRC. Additionally, combining RV with inspiratory capacity (IC) or forced vital capacity (FVC) with ERV does not represent the FRC either, as these combinations include volumes that are unrelated to the specific