Effect of liquid properties and aerosol dilution conditions on the final droplet size of aerosol delivered from nebulizers

Authors:

• Katarzyna Ewa Dobrowolska,
• Małgorzata Matyśkiewicz,
• Tomasz Robert Sosnowski

Abstract

Nebulizers are medical devices, which disperse pharmaceutical liquids to fine droplets for inhalation (aerosol therapy). Such droplets with diameter below 5 μm can penetrate to the lowest parts of human lungs and deposit on the surface of lungs. Deposition areas and hence the efficiency of aerosol therapy are strongly influenced by many factors, i.e.: geometry of the respiratory system, individual respiratory parameters and the properties of aerosol which are related to the physicochemical properties of the liquid drug. Optimization of these parameters and better understanding of their impact on droplet size distribution in the aerosol cloud can improve the effectiveness of the therapy. The aim of this study was to investigate the influence of: (i) physicochemical properties (i.e., surface tension, viscosity and conductivity) of selected reference liquids, and (ii) properties and amount of external air which dilutes the aerosol during inhalation from nebulizers (i.e. air temperature and humidity) on the characteristics of the aerosol (droplet size distribution and mass output). Aerosol parameters were measured, among others, by laser diffraction with the simultaneous monitoring the external conditions of air admixed to the clouds emitted from jet (Pari Boy) and mesh (Intec Twister) nebulizers. The results show that the surface tension and viscosity of atomized liquid change the droplet size distribution of aerosol. The principle of operation of a given nebulizer (jet or mesh) also strongly influence the characteristics of aerosol. The effect of diluting was noted. To conclude, the variation in aerosol parameters measured in this study being the result of liquid properties and different conditions of aerosol dilution, show the importance of tested factors on predicted drug deposition in the lungs. Therefore, these factors should be taken into account in the optimization of drug nebulization process for inhalation therapy.