Vital capacity 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.
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.
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
|Height||150–155 cm (5'–5'2")||155–160 cm (5'2"–5'4")||160–165 cm (5'4"–5'6")||165–170 cm (5'6"–5'8")||170–175 cm (5'8"–5'10")||175–180 cm (5'10"–6')|
|Vital capacity (cm3)||2900||3150||3400||3720||3950||4300|
|Vital capacity (cm3)||3425||3500||3225||3050||2850|
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.
- "Vital Capacity". Family Practice Notebook. Retrieved 19 February 2015.
- Hutchinson, J (1846). "On the capacity of the lungs, and on the respiratory functions, with a view of establishing a precise and easy method of detecting disease by the spirometer". Med Chir Trans 29: 137–252. PMC 2116876. PMID 20895846.
- "Pulmonary Function Tests". UCSD. Retrieved 19 February 2015.
- Pratt, Joseph H. (1922). "Long-continued observations on the vital capacity in health and in heart disease". Transactions of the Association of American Physicians (W. J. Dornan, Incorporated) 37: 182–197.
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