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 (FEV1) of 37.9% of the predicted value inhaled three types of monodisperse salbutamol and ipratropium bromide aerosols with particle sizes of 1.5 microns, 2.8 microns, and 5 microns, respectively, and a placebo aerosol. The volunteers inhaled 20 micrograms salbutamol and 8 micrograms ipratropium bromide, after which lung function changes were determined and analysed with repeated measurements analysis of variance (ANOVA). RESULTS Greater improvements in FEV1, specific airway conductance (sGaw) and maximum expiratory flow at 75%/50% of the forced vital capacity (MEF75/50) were induced by the 2.8 microns 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 microns.