Respiratory Volumes and Capacities
An instrument called a spirometer is used to measure the volume of air that moves into and out of the lungs, and the process of taking the measurements is called spirometry. Respiratory (pulmonary) volumes are an important aspect of pulmonary function testing because they can provide information about the physical condition of the lungs.
Respiratory capacity (pulmonary capacity) is the sum of two or more volumes.
Factors such as age, sex, body build, and physical conditioning have an influence on lung volumes and capacities. Lungs usually reach their maximumin capacity in early adulthood and decline with age after that.