Evaporation of Aqueous Aerosols Produced by Jet Nebulizers: Effects on Particle Size and Concentration of Solution in the Droplets

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Abstract
Aqueous droplets produced by jet nebulizers can lose water by evaporation prior to entry into the patient's mouth, or a sizing device. Evaporation causes increase in the concentration of the solution in the droplet and reduction in size. These changes can complicate interpretation of results from experiments such as in vitro particle sizing or human respiratory tract deposition. We present experimental data obtained by nebulization of isotonic saline using a variety of aerosol delivery systems employing jet nebulizers. The impact of the evaporation phenomena is particularly great when a large volume of dry dilution air is mixed with the aerosol stream - a situation that is quite common in aerosol experiments. The experimental results approach the values calculated from the theoretical mass balance models in the limit of equilibrium between the droplets and the surrounding atmosphere.