Latent pulmonary function abnormalities in former asthmatic subjects

A great deal is known about the lung functional abnormalities present in asthmatics during acute attacks and during asymptomatic periods. Relatively little attention has been given to the ex asthmatic - the individual who has been totally free of symptoms for many years and who may be considered to be completely free of disease. The purpose of this study was to investigate a group of former asthmatic patients to determine whether any latent pulmonary function abnormalities are present many years following the last attack. In order to achieve this, ten noncigarette smoking, former childhood asthmatics, on no medication and with no history of allergic rhinitis, were compared to a control group of ten, also matched for age and sex. The ex asthmatics were young adults who had been completely free of symptoms for an average of 9.9 years (range 3 to 22 years). The experimental protocol was designed in order to evaluate routine lung volumes as well as large airways, small airways, and bronchial reactivity. Lung volumes, Wright peak flow and FEV₁/FVC% could not distinguish between the two groups. Although specific conductance was consistently normal in controls, it was abnormal in six ex asthmatics, suggesting latent involvement of the large airways. Mid maximal flow rate (MMFR), maximal expiratory flow rate at 50% and 75% vital capacity (V max 50 and V max 75) and closing volume (CV), tests reflecting small airway function, were all statistically lower in ex asthmatic patients. Following inhalation of isoproterenol, the changes in specific conductance and FEV₁ were similar in both groups. Increases in V max 50 and V max 75 were 31.8% and 31.9% respectively in ex asthmatic patients compared to 2.6% and 4.2% in controls. These differences were highly significant. These data show that latent abnormalities of large and small airways exist in ex asthmatic young adults many years following the disappearance of clinical disease.