A novel experimental approach to measure nebulized droplet deposition pattern and deposition fraction in an idealized mouth-to-throat model

Accurate measurement of droplet/particle deposition fraction and spatial distribution is vital for understanding various inhalation processes, including nebulized therapy, inhalation of atmospheric pollutants, and exposure risk assessment to aerosols such as airborne SARS-COV-2-laden droplets. This paper presents a novel method to measure the deposition fraction and spatial distribution of the deposited particulate phase (i.e., deposition pattern) of droplets through a single experiment. The experiment employs an idealized mouth-to-throat model as a test platform for two vibrating mesh nebulizers to deposit droplets. By utilizing a nebulized solution of normal saline containing the fluorescein, the qualitative observation of droplet deposition pattern on the internal surfaces is achieved under ultraviolet excitation. Furthermore, through rinsing the experimental components and quantitatively determining the deposition fraction based on rinsate absorbance, experimental results indicate that the deposition fraction of nebulized droplets decreases initially and then increases with increasing inspiratory flow rate from 15 to 60 l/min. Additionally, the deposition hotspots gradually shift from the bottom of the oral cavity to the throat as the inhalation flow rate increases. In addition to providing validation data for the transport and deposition of high-concentration droplets, this experimental method has the potential for extension to research on aerosol transmission and exposure risk assessment. It offers valuable insight into the behavior of nebulized droplets, aiding in developing effective strategies for aerosolized therapies and mitigating transmission risks in various applications.