Vital capacity

Output of a spirometer

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:

$${\begin{aligned}vc_{female}=(21.78-0.101a)\cdot h\\vc_{male}=(27.63-0.112a)\cdot h\\\end{aligned}}$$ where $vc$ is approximate vital capacity in cm³, $a$ is age in years, and $h$ is height in cm.

Further reading

Several studies have been made to measure and predict vital capacity:

• Berglund, E.; Birath, G.; Bjure, J.; Grimby, G.; Kjellmer, I.; Sandqvist, L.; Söderholm, B. (1963). "Spirometric Studies in Normal Subjects I: Forced Expirograms in Subjects Between 7 and 70 Years of Age". Acta Medica Scandinavica. 173 (2): 185–192. doi:10.1111/j.0954-6820.1963.tb16520.x. PMID 13970718.
• Birath, G.; Kjellmer, I.; Sandqvist, L. (1963). "Spirometric Studies in Normal Subjects: II. Ventilatory Capacity Tests in Adults". Acta Medica Scandinavica. 173 (2): 193–198. doi:10.1111/j.0954-6820.1963.tb16521.x. PMID 13968399.
• Grimby, G.; Sóderholm, B. (1963). "Spirometric Studies in Normal Subjects: III. Static Lung Volumes and Maximum Voluntary Ventilation in Adults with a Note on Physical Fitness". Acta Medica Scandinavica. 173 (2): 199–206. doi:10.1111/j.0954-6820.1963.tb16523.x.
• Forche, Günther; Stadlober, Ernst; Harnoncourt, Karl (1988). "Neue spirometrische Bezugswerte für Kinder, Jugendliche und Erwachsene" [New spirometric reference values for children, adolescents and adults]. Österreichische Ärztezeitung (in German). 43 (15, 16): 40–42.
• Gulsvik, A.; Tosteson, T.; Bakke, P.; Humerfelt, S.; Weiss, S. T.; Speizer, F. E. (30 November 2001). "Expiratory and inspiratory forced vital capacity and one-second forced volume in asymptomatic never-smokers in Norway: Spirometric standards in Norway". Clinical Physiology. 21 (6): 648–660. doi:10.1046/j.1365-2281.2001.00377.x. PMID 11722472.
• Hedenström, H; Malmberg, P; Agarwal, K (November 1985). "Reference values for lung function tests in females. Regression equations with smoking variables". Bulletin Européen de Physiopathologie Respiratoire. 21 (6): 551–557. OCLC 114155676. PMID 4074961. INIST 8470928.
• Langhammer, A.; Johnsen, R.; Gulsvik, A.; Holmen, T.L.; Bjermer, L. (1 November 2001). "Forced spirometry reference values for Norwegian adults: the Bronchial Obstruction in Nord-Trøndelag study". European Respiratory Journal. 18 (5): 770–779. doi:10.1183/09031936.01.00255301. PMID 11757626.