THE OPTIMAL PARTICLE-SIZE FOR BETA-ADRENERGIC AEROSOLS IN MILD ASTHMATICS

Background: the optimal particle size of a beta(2)-mimetic aerosol is not known. Methods: eight stable asthmatics with a FEV(1) (forced expiratory volume) of 72% of the predicted value inhaled three types of monodisperse salbutamol aerosols, with particle sizes of 1.5, 2.8 and 5 mu m, respectively, and a placebo aerosol. The volunteers inhaled cumulative dosages of 5, 10, 20 and 40 mu g salbutamol, after which lung function improvement was determined. The four resulting dose-response curves (one for each type of aerosol) were analysed with repeated measurements ANOVA. Results: for the FEV, and the MEF(75/50/25) (maximum expiratory flow) the 2.8 mu m aerosol induced a significantly better dilation than the 5 mu m aerosol. In the case of the PEF (peak expiratory flow) the 1.5 mu m aerosol elicited a significantly smaller improvement than the 2.8 mu m aerosol. No particle size effect was noticeable in the case of the VC (vital capacity), FVC (forced vital capacity) and the R(tot). Conclusions: in mild asthmatics the particle size of choice for a beta(2)-mimetic aerosol should be around 2.8 mu m.