A Numerical Simulation Model for Realistic Representation of the Evolution, Transport, and Deposition of Hygroscopic Aerosols in the Respiratory Tract

Abstract

Achieving accurate simulation of respiratory drug delivery is essential for understanding nebulized droplet behaviour and assessing aerosol exposure risk. Previous studies have shown that the dynamic evolution of droplets can be analyzed more accurately using a two-way coupling method between the continuous phase (i.e., airflow) and the discrete phase (droplets), as the highly concentrated aerosol exchanges water vapor mass with the environment during the nebulization process. In order to verify the rationality and scientific validity of the two-way coupling method and to provide a more comprehensive quantitative analysis, we simulated the nebulized inhalation process of droplets under different environmental temperature and humidity conditions in an idealized mouth-throat (MT) airway model, and also recorded the droplet/particle deposition fractions ( ) and deposition patterns, and analyzed them in comparison with the experimental data. The interactions between the continuous and discrete phases are modeled by an innovative two-way coupling method of aerosol-water vapor interactions in highly concentrated droplets by the particle parcel method. The simulation results illustrate that the predictions of the droplets by the two-way coupling method used are in good agreement with the experimental data and the overall trend can be reasonably explained. This may have significance for the study of drug aerosol delivery efficiency in the human respiratory tract. In addition, as evaporation of nebulized droplets is slowed down in warm and wet condition, which may further affect the deposition of nebulized droplets in the lower respiratory tract.

Keywords: Nebulized inhalation, Validation, Highly concentrated droplet aerosol, Environmental temperature, humidity