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

Total lung capacity (TLC) is defined as the total volume of air that the lungs can hold. It encompasses several components of lung volume. The key components involved in calculating TLC are the vital capacity (VC) and the residual volume (RV).

Vital capacity (VC) is made up of the tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). Since RV is the volume of air remaining in the lungs after a maximal exhalation, the total lung capacity can be expressed as the sum of the vital capacity and the residual volume.

Thus, the formula for total lung capacity is correctly represented by adding the forced vital capacity (FVC, which is a measure of the VC) and the residual volume (RV). This highlights the comprehensive nature of TLC by accounting for both the actively used capacities during breathing and the air that remains in the lungs at all times.

Understanding this relationship is crucial in pulmonary physiology and helps in the assessment of lung function in various clinical scenarios.