Lung volume and its subdivisions in normal and asthmatic males.

Measurements of lung volume and its subdivisions were made in 89 asthmatic children and adults and 58 normal subjects. The asthmatics were divided into three groups according to the classification of Jones (1966). In this the FEV is used as an index of airways resistance which is divided into labile and fixed components. The compartment of lung volume showing the largest increase was the residual volume in subjects with a predominantly fixed increase of airways resistance (group 3) and this was true of both the children and adults. This compartment was also significantly enlarged in the labile subjects (groups 1 and 2). Significant increases in functional residual capacity were demonstrated in all three groups, especially in the children. Total lung capacity was significantly increased in the two labile groups of children but not in the adults. Even a low level of lability (group 1) may be associated with highly significant abnormalities in lung volume compartments which may be more evident in the child than in the adult.