The paper highlights selected problems of physical chemistry and dynamics of colloidal systems indispensable for the understanding and optimization of drug delivery by inhalation. Besides describing the fundamental aspects of aerosol flow and deposition in the respiratory system, some problems related to particle or droplet generation in the inhalers are discussed. In particular, the influence of liquid properties on aerosol formation in different nebulizers is demonstrated as a critical factor in successful aerosol therapy. The paper also addresses interactions between inhaled drug particles and bronchial mucus or the pulmonary surfactant, indicating another broad field of colloid and interface science application in medicine.
The works presents the application of mass/volume balances of liquid drug converted into the aerosol during atomization in medical nebulizers. The amount of liquid that can be delivered to the respiratory system during inhalation is reduced compared to the nominal dose not only because of drug losses both in the device (the residual volume, RV) and outside the nebulizer (in the mouthpiece, mask, or tubings), but also to the limitations of the patient (periodic flow with limited capacity). The paper should help to understand the complexity of aerosol therapy widely used in asthma, COPD and other pulmonary diseases.
Nebulizers are the class of atomizing devices used to disperse liquids to fine droplets. They found their application in selected technological (typically: small-scale) processes, but their most common use is related to the generation of medicinal aerosols for inhalation. In this work we present the experimental data on the evolution of the size distributions of water droplets generated by two nebulizers (pneumatic and vibrating-mesh) as a result of aerosol mixing with the ambient air. Such a process reflects the real situation, where aerosol emitted from a nebulizer is diluted by additional air sucked by a patient during inhalation. Droplet size distribution was determined by laser diffraction, and these results were further discussed including the data of the aerosol velocity measured by the Laser Doppler Anemometry (LDA). It was demonstrated – as expected - that dilution with the ambient air with moderate humidity results in the intense evaporation of the smallest droplets. However, larger droplet may be saved to a different degree depending on the velocity and geometry of the aerosol cloud emitted from the nebulizer, and on the volume of the diluting air. These parameters have an influence on the droplet coalescence which is another process shaping the droplet size distribution in the studied conditions. The results can deepen the understanding of the mist dynamics which can be applied in various fields of colloidal science and technology.
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