Eulerian–Lagrangian and thin film modeling of drug delivery under physiologically varying breathing in a realistic lung model

This work presents a computational approach to investigate antiviral aerosol deposition in anatomically realistic human airways under various physiological inhalation conditions. Antiviral drugs are represented as fine droplets that form a thin coating on airway surfaces, primarily targeting early infection sites. The suggested method combines an Eulerian–Lagrangian discrete phase model (DPM) to track droplet motion and an Eulerian wall film (EWF) model to mimic the evolution of deposited liquid films. This combination effectively addresses the shortcomings of previous studies that employed DPM exclusively, which ignored the post-deposition redistribution dynamics of liquid drugs on airway surfaces. To the best of our knowledge, this is the first study to integrate a DPM–EWF framework within a realistic airway model under both healthy and disease-specific inhalation conditions to predict drug delivery. The study assesses airflow parameters, film thickness, deposition efficiency, and surface area coverage for aerosol particles from 1 to 10 μm. Results reveal that distressed breathing patterns of chronic obstructive pulmonary disease patients significantly alter the deposition preferences between the upper (∼5.28%) and lower lobes (∼2.52%) compared to the equivalent ideal (upper: ∼3.31%, lower: ∼4.32%) and realistic healthy (upper: ∼3.80%, lower: ∼6.79%) inhalations. Moreover, the distressed breathing also limits the drug penetration into deeper generations, as the highest surface coverage is observed at the carinal region rather than the usual left lower lobe found in ideal and realistic healthy breathing cases. Such deposition contrasts highlight the importance of optimizing inhalation therapy and device designs for individuals with obstructive airway diseases.