Pulmonary function in children with a history of laryngotracheobronchitis.

Baseline, postexercise, and postisoproterenol lung function was studied in 27 children, 8 to 18 years of age, with a past history of laryngotracheobronchitis (croup) and in ten children without such a history. The LTB subjects were divided into two groups, based on the presence or absence of allergies. Baseline flow tests were similar in all groups but small airway function was mildly abnormal in several members of each group. There was no consistent response to isoproterenol inhalation among those who had had croup and normal subjects. Following exercise, however, a significant (P less than 0.05) number of subjects (14 of 27) in both LTB groups demonstrated bronchoconstriction with a greater than 10% drop in peak expiratory flows. From these studies, it appears that children with a past history of croup have a higher prevalence of increased bronchial reactivity, which occurs irrespective of allergy and baseline lung function abnormalities.