Topic overview

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Lung capacities are combinations of individual lung volumes. Total lung capacity is the sum of all volumes, while vital capacity and inspiratory capacity combine volumes that can be moved during breathing. Functional residual capacity represents the volume remaining after a normal exhalation and includes residual volume, which cannot be exhaled. Because spirometry cannot measure residual volume, it also cannot directly measure capacities that include it. Capacity patterns help distinguish restrictive changes, which reduce TLC and VC, from obstructive changes, which can increase RV and TLC while reducing VC. The topic also connects these measures with oxygen reserve, aerosol delivery, perioperative assessment, and monitoring for pulmonary effects of disease or treatment.