vital capacity (VC) [L, vita, life, capacitas, capacity] , the maximum volume of air that can be expelled at the normal rate of exhalation after a maximum inspiration, representing the greatest possible breathing capacity. The VC equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume. The average normal value of 4 to 5 L is affected by age, the physical dimensions of the chest cage, physical fitness, posture, and gender. The VC may be reduced by a decrease in the amount of functioning lung tissue resulting from atelectasis, edema, fibrosis, pneumonia, pulmonary resection, or tumors; by limited chest expansion resulting from ascites, chest deformity, neuromuscular disease, pneumothorax, or pregnancy; or by airway obstruction. Compare forced expiratory volume, forced expiratory vital capacity, residual volume.
