Objective indicators of severity of asthma

Subjects with asthma who are intensively treated in residential care facilities frequently demonstrate marked clinical improvement in their disease, with fewer attacks and improved well being. Despite their improved status, it is known that pulmonary function test results often remain abnormal in patients with asthma. This prospective study on children with asthma receiving residential care was carried out to determine which pulmonary function parameter best reflected clinical improvement through correlation with the duration of complete freedom from wheezing. Evaluated in 42 children were spirometry values including forced vital capacity, forced expiratory volume in 1 second, peak expiratory flow rate, forced expiratory flow (between 25% and 75% of forced vital capacity), and lung volumes as reflected by residual volume/total lung capacity. Bronchial hyperreactivity as reflected by bimonthly provocative concentration causing a 20% fall in FEV1 in response to methacholine inhalation was evaluated in 18 patients. All pulmonary function test results were correlated with days since last wheezing episode. Results indicate that only peak expiratory flow rate (r = 0.91; p < 0.001), forced expiratory volume in 1 second (r = 0.69; p < 0.01), and forced expiratory flow (r = 0.62; p < 0.05) demonstrated significant correlation with the number of days since last wheezing episode. Of particular interest was the failure of bronchial hyperreactivity to improve despite intensive therapy with bronchodilators and corticosteroids. Persistence of bronchial hyperreactivity despite intensive therapy with corticosteroids suggests that in at least some children with severe asthma, bronchial hyperreactivity may be especially long-lived, may be perpetuated by inhaled beta 2 agonists, or may exist independently of airway inflammation.