Regional air trapping before and after exercise in young adults with cystic fibrosis.

Much of respiratory therapy in patients with cystic fibrosis is directed toward clearing airway secretions and dilating the airways to improve ventilation to slowly equilibrating spaces. We studied nine patients with cystic fibrosis (18 to 28 years old) who had mild to severe airway obstruction to determine whether ventilation to regions containing slow spaces was influenced by a period of exercise. Regional ventilation was assessed by measuring the trapped-air index (TAI) before and at least (1/2) hour after bicycle exercise. On the average, the TAI was highest in the apices and lowest in the lung bases. The apical TAI correlated significantly with the overall amount of trapped air and the forced expiratory volume in one second, indicating that abnormalities in the apices have a pronounced influence on overall lung function. For the patients with moderate or severe airway obstruction, the mean TAI decreased after exercise in the upper regions where it was abnormally high before exercise. The results suggest that slow spaces exist in the apices of all patients with cystic fibrosis who have airway obstruction and that a period of exercise improves tidal ventilation in the apices of patients with moderate or severe airway obstruction.