E-cigarette aerosol deposition efficiency is increased in direct-to-lung, compared to mouth-to-lung, inhalation patterns

Determining the health effects of vaping is challenging due to the constantly evolving landscape of electronic cigarette (EC) products and modes of use. Studying the effect of EC aerosols on health requires in vivo and in vitro experiments, where dose and deposition of aerosol is important. We present a computational approach to predict aerosol dosimetry throughout a realistic airway tree to support experimental dosimetry, providing the ability to predict dosimetry in different subjects, species, vaping products and inhalation conditions. EC aerosol transport was modelled using advection-diffusion equations, and deposition was estimated via the mechanisms of sedimentation, impaction, and Brownian diffusion. The model was applied to determine the impact of particle size, such as with increasing EC device power settings, and comparison of mouth-to-lung (MTL) and direct-to-lung (DTL) vaping regimens. Results showed a bell-shaped trend in deposition efficiency, ranging from 74% to 72% over a particle size range of 20 nm to 3.5 μm, with the lowest deposition (∼15% in DTL and ∼5% in MTL vaping) in the mid-particle size range (0.5 μm). Deposition was higher for DTL vaping compared with MTL. MTL vaping resulted in a higher proportion of deposition in the upper airways, while DTL vaping showed greater deposition in the respiratory airways, due to differences in flow rates and puff volume. The mass of particles deposited throughout the airway tree varied from 1×10 -7 mg to 4×10 -3 mg indicating large variability and the importance of tailoring dose correctly depending on which part of the airway tree is being studied. • An in silico model was used to predict e-cigarette aerosol transport in the lungs. • Model predictions can be used to inform dosimetry for in vitro airway studies. • Deposition is sensitive to aerosol droplet size, vaping topography • Direct-to-lung vaping increased aerosol deposition especially in the alveolar zone. • Vaping dosimetry varies widely across airway generations and vaping styles.