Bronchial vagal tone and responsiveness to histamine, exercise and bronchodilators in adult patients with cystic fibrosis.

Atopy and bronchial responsiveness to histamine, exercise and bronchodilators were investigated in 18 adult patients with cystic fibrosis (CF). Reversibility of airflow limitation was measured after ipratropium bromide and terbutaline, and histamine and exercise provocation tests were performed. Histamine hyperresponsiveness was observed in 10 out of 18 patients and was not confined to those with severe airway obstruction. The positive histamine responders showed significantly better bronchodilatation after terbutaline, when compared to negative histamine responders. Histamine responsiveness was not related to atopy or exercise responsiveness. Exercise challenge caused bronchodilatation without bronchoconstriction in all patients. The exercise-induced bronchodilatation correlated with bronchodilatation after ipratropium bromide. It is proposed that an increased vagal tone may lead to an increased resting bronchomotor tone which can be reduced by ipratropium bromide and by exercise in adult patients with cystic fibrosis.