Clearance in small ciliated airways in allergic asthmatics after bronchialallergen provocation

Background: Asthma tends to affect mucociliary clearance, as assessed from measurements in large airways. However, there is no knowledge about clearan ce in the smallest airways of the tracheobronchial region in acute exacerba tion of asthma. Objective: The aim of the study was to investigate clearanc e from the bronchiolar region in patients with allergic asthma in a situati on resembling a mild acute exacerbation of the disease. We also aimed to co mpare clearance data with corresponding data found for healthy subjects and asthmatics on therapy. Methods: Tracheobronchial clearance was studied twi ce in 9 patients with mild asthma of the allergic type after inhalation of 6 mu m (aerodynamic diameter) monodisperse Teflon particles labelled with I n-111. At one exposure, inhalation was performed 4 h after bronchial provoc ation with an allergen the patients were allergic to. The second exposure w as a control measurement. The particles were inhaled at an extremely slow f low, 0.05 liter/s, which gives deposition mainly in the small ciliated airw ays (bronchioles). Lung retention was measured at 0, 24, 48 and 72 h. Resul ts: All patients demonstrated an early asthmatic reaction of varying degree after bronchial provocation. There was significant clearance of radioaeros ol in each 24-hour period for both exposures, with the possible exception o f the period between 24 and 48 h for the provocation exposure, with similar fractions of retained particles at all points of time. The retained fracti ons were significantly larger compared to a group of healthy subjects and a sthmatics on regular treatment with anti-inflammatory drugs. Conclusions: O ur results indicate that in allergic asthmatics a bronchial allergen provoc ation with an early asthmatic reaction does not significantly influence ove rall clearance from the bronchiolar region. However, in the present group o f patients, retention in small ciliated airways was significantly higher co mpared to healthy subjects and asthmatics on regular treatment.