A longitudinal study of bronchodilator responsiveness in cystic fibrosis.

The prevalence of bronchodilator responsiveness was evaluated in 20 outpatients with cystic fibrosis (CF) every 1 to 3 months for a 1-yr period and in 20 patients with CF during a hospital admission. All but 1 subject (95%) showed a significant bronchodilator response at least once on an outpatient basis; nonhospitalized subjects were responsive 49% of the time. Bronchodilator responsiveness was unrelated to long-term pulmonary severity or indexes of atopy but it was significantly influenced by season of the year; 70% of the population was responsive in winter compared with 25% in summer. Bronchodilator responsiveness increased during hospital admission together with improvement in baseline values; 23% of the population was responsive during the first 3 days compared with 80% by the end of the second week of admission. After discharge, a reverse pattern occurred, with decrease in bronchodilator responsiveness and a fall in baseline values. However, in some patients, bronchodilator responsiveness was lost when baseline values were still at their best. Bronchodilator responsiveness in CF tends to undulate with pulmonary exacerbations of the disease.