THE OPTIMAL PARTICLE-SIZE FOR PARASYMPATHICOLYTIC AEROSOLS IN MILD ASTHMATICS

Background: the optimal particle size of a parasympathicolytic aerosol is unknown. Methods: eight stable asthmatics with a mean FEV(1) of 72% of the predicted value inhaled three types of monodisperse ipratropium bromide aerosols, with;particle sizes of 1.5, 2.8 and 5 mu m, respectively, and a placebo aerosol. The volunteers inhaled 8 mu g ipratropium bromide, after which lung function improvement was determined. The changes in lung function were analysed with repeated measurements ANOVA. Results: according to the changes in FEV(1) and MEF(50/25) the 1.5/2.8 mu m aerosol induced significantly better bronchodilatation than the 5 mu m aerosol. No particle size effect was noticeable with regard to changes in R(tot), VC, FVC and PEF. Conclusions: in mild asthmatics the particle size of choice for a parasympathicolytic aerosol should be less than or equal to 2.8 mu m.