Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. It is approximately equal to Forced Vital Capacity (FVC).
A person's vital capacity can be measured by a wet or regular spirometer. In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease. Furthermore, the vital capacity is used to determine the severity of respiratory muscle involvement in neuromuscular disease, and can guide treatment decisions in Guillain–Barré syndrome and myasthenic crisis.
A normal adult has a vital capacity between 3 and 5 litres. A human's vital capacity depends on age, sex, height, mass, and possibly ethnicity. However, the dependence on ethnicity is poorly understood or defined, as it was first established by studying black slaves in the 19th century and may be the result of conflation with environmental factors.
Lung volumes and lung capacities refer to the volume of air associated with different phases of the respiratory cycle. Lung volumes are directly measured, whereas lung capacities are inferred from volumes.
Role in diagnosis
The vital capacity can be used to help differentiate causes of lung disease. In restrictive lung disease the vital capacity is decreased. In obstructive lung disease it is usually normal or only slightly decreased.
Estimated vital capacities
+ Males by height Height 150–155 cm (4'11"–5'1") 155–160 cm (5'1"–5'3") 160–165 cm (5'3"–5'5") 165–170 cm (5'5"–5'7") 170–175 cm (5'7"–5'9") 175–180 cm (5'9"–5'11) Vital capacity (cm3) 2900 3150 3400 3720 3950 4300
+ Males by age Age 15–25 25–35 35–45 45–55 55–65 Vital capacity (cm3) 3425 3500 3225 3050 2850
Formulas Vital capacity increases with height and decreases with age. Formulas to estimate vital capacity are:
where is approximate vital capacity in cm3, is age in years, and is height in cm.
References
Further reading Several studies have been made to measure and predict vital capacity: