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.[citation needed]
A normal adult has a vital capacity between 3 and 5 litres.[3] A human's vital capacity depends on age, sex, height, mass, and possibly ethnicity.[4] However, the dependence on ethnicity is poorly understood or defined, as it was first established by studying black slaves in the 19th century[5] and may be the result of conflation with environmental factors.[6]
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.[7]
Vital capacity increases with height and decreases with age. Formulas to estimate vital capacity are:[3]
where is approximate vital capacity in cm3, is age in years, and is height in cm.
References
^Chhabra, S. K. (January 1998). "Forced Vital Capacity, Slow Vital Capacity, or Inspiratory Vital Capacity: Which Is the Best Measure of Vital Capacity?". Journal of Asthma. 35 (4): 361–365. doi:10.3109/02770909809075669. PMID9669830.
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. PMID13970718.
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. PMID13968399.
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. PMID11722472.
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. OCLC114155676. PMID4074961. INIST8470928.
