Large lungs after childhood asthma: a consequence of enlarged airspaces.

Abstract

The long-term effects of asthma on lung volume were investigated in 18 asthmatic patients during periods of remission from airway obstruction; ten had developed asthma in childhood (before 8 years of age) and eight after the age of 18 years. Subjects whose asthma began in childhood had an increased total lung capacity (TLC) on average; adult-onset asthmatics had normal mean lung volumes. Exponential analysis of static pressure-volume curves in these subjects showed that the childhood-onset asthmatics had lungs of increased distensibility, while adult-onset asthmatics had lungs of normal distensibility. In a further ten adults selected for having had asthma in the past and an increased vital capacity, all had developed asthma in childhood, had lungs of increased distensibility and an increased TLC. Increased distensibility and an increased TLC were closely associated within individuals. The close relationship between distensibility and the size of peripheral air spaces demonstrated in mammalian lungs, suggests that asthma in childhood may increase TLC and distensibility because of an increase in the size of peripheral airspaces.