Prediction of the transport, deposition, and absorption of multicomponent E-cigarette aerosols in a subject-specific mouth-to-G10 human respiratory system

Abstract

Predicting the transport and deposition of e-cigarette aerosols in human respiratory systems is essential to understand how e-liquid compositions, especially different nicotine forms, can influence the absorption of nicotine in the human lung. Using a newly developed computational fluid-particle dynamics (CFPD) method based on the species transport and discrete phase models, this study simulated and compared the transport dynamics of multi-component e-cigarette aerosols in a subject-specific human respiratory system. Specifically, the experimentally calibrated and validated CFPD model can predict the gas-liquid phase change dynamics of water, propylene glycol (PG), vegetable glycerin (VG), and nicotine in the aerosols during their transport through the pulmonary route. Results indicate that acidity levels in e-liquid can affect nicotine evaporation and that higher levels of acidity can reduce evaporation rates and increase the delivery of nicotine vapor to small airways. The study also found that benzoic acid was more effective in reducing nicotine evaporation compared to lactic acid. Furthermore, increasing the PG/VG ratio in the initial e-liquid composition can potentially lead to a reduction in nicotine evaporation rate, and therefore an increase in the amount of nicotine vapor absorbed in small airways beyond generation 10 (G10). Additionally, droplet size dynamics are influenced more by larger mass components such as PG evaporation and water condensation from the humid air, rather than nicotine. However, the impact of initial e-liquid composition on droplet transport and deposition is relatively insignificant compared to its impact on vapor phase transport and absorption. Lastly, increasing the follow-up inhalation flow rate after puffing increases liquid phase deposition and nicotine vapor absorption from the mouth to G10, but does not significantly affect evaporation and condensation. A decrease in droplet size results in an increase in the nicotine evaporation rate and subsequent absorption by the airways from the mouth to G10.