Optimal particle size for beta(2) agonist and anticholinergic aerosols in patients with severe airflow obstruction

Background - The optimal particle size of a beta(2) agonist or anticholinergic aerosol in patients with severe airflow obstruction is unknown. Methods - Seven stable patients with a mean forced expiratory volume in one second (FEV(1)) of 37.9% of the predicted value inhaled three types of monodisperse salbutamol and ipratropium bromide aerosols with particle sizes of 1.5 mu m, 2.8 mu m, and 5 mu m, respectively, and a placebo aerosol. The volunteers inhaled 20 mu g salbutamol and 8 mu g ipratropium bromide, after which lung function changes were determined and analysed with repeated measurements analysis of variance (ANOVA). Results - Greater improvements in FEV,, specific airway conductance (sGaw) and maximum expiratory flow at 75%/50% of the forced vital capacity (MEF(75/50)) were induced by the 2.8 mu m aerosol than by the other particle sizes. Conclusions - In patients with severe airflow obstruction the particle size of choice for a beta(2) agonist or anticholinergic aerosol should be approximately 3 mu m.