Decreasing the particle size of aerosols of local anaesthetic by heating

Abstract

We used a cascade impactor and radioactive labelling to determine the distribution of particle size in aerosols from several commercially available nebulizers, and the effect of heating on the size distribution. Mass median diameter (MMD) of the unheated aerosols ranged from 1.4 to 4.8 μm and this was reduced by heating to a range of 06 to 1.9 μm. Bupivacaine (0.5%) can be given as an aerosol after heating with minimal side-effects from anaesthesia of the upper respiratory tract, since the smaller, concentrated, particles are deposited deeper in the lung. This may have clinical applications.