The expression "vital capacity" of the lungs has long been employed to designate the quantity of air that can be breathed out by the deepest possible expiration after the deepest possible inspiration. It is regarded as a rough measure of lung capacity, and has long been determined in the physical examination of persons engaged in gymnastic exercises. The vital capacity shows a considerable range in absolute values determined for admittedly healthy, normal persons, the variations being accounted for largely by the differences in the size of the individuals examined; an average figure for an adult man is 3,700 c.c. The data in regard to this factor are usually secured by spirometry.
It seems almost obvious that any considerable decrease in the vital capacity of a person must represent a decided physiologic disadvantage. For example, interference with pulmonary ventilation may occur when a pleural effusion arises; and the difficulty presents itself
CLINICAL SPIROMETRY AND THE VITAL CAPACITY OF THE LUNGS. JAMA. 1922;78(6):433–434. doi:10.1001/jama.1922.02640590037016
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