Modeling the Transient Absorption of Particulate Drugs in the Human Upper Airways

Predicting the dynamics of aerosols in the respiratory tract is crucial for the analysis of toxic effects of particulate matters and to the respiratory targeted drug delivery. The present work focuses on evaluating the transient absorption of drug particles on the airway walls of the respiratory tract. For this purpose, simulations of airflow and particulate matters inside a three-dimensional model of respiratory airways were coupled to a one-dimensional drug absorption model. The drug absorption from mucus to the respiratory walls was studied using the transient mass transfer equations in a multilayer model. Different breathing rates of 5, 7.5, and 10 Lit/min were considered in the simulations. Particles with different sizes of 2, 5, 10, and 30µm were released at the entrance of the oral cavity during the inspiration phase. The airflow velocity distribution, particle concentration, and flux of drugs at the interface of mucus-tissue were studied in detail. The transient absorption process that occurred over the breathing time considered of 4 s was evaluated. The results showed that the drug mass flow rate at the mucus-tissue interface and the drug concentration in the tissue layer decreases with time. Also, it was found that after inspiration, the location of the maximum concentration changes from mucus to the tissue layer.