In Silico Investigation of Tracheal Stenosis Effects on Aerosolized Drug Delivery under Realistic Physiological Breathing

Tracheal stenosis significantly alters respiratory airflow and influences the transport and deposition of inhaled drug particles. The present study numerically investigates aerosol transport, particle deposition, and thin-film formation in disease-specific tracheobronchial airways with mild (15%), moderate (45%), and extreme (70%) stenosis under a realistic inhalation maneuver. The novelty of this study lies in its disease-specific assessment of aerosol drug delivery across different degrees of tracheal stenosis under physiological conditions. Furthermore, the combined Eulerian wall film and discrete phase model (DPM) captures both particle deposition and post-deposition liquid film behavior, providing a more realistic representation of inhaled drug transport than conventional DPM-based approaches. The investigation evaluates airflow characteristics, deposition efficiency, film thickness, and area coverage for aerosol particles of 1, 5, and 10 μm. The results indicate that increasing stenosis severity significantly alters airflow asymmetry, leading to directionally biased jet formation and distinct particle deposition behavior. The peak velocity magnitude along the stenosis increases from nearly 4.2 to 12 m/s, leading to an equally strong increase in vorticity generation (4000 to 12 000 s−1) as severity increases from mild to extreme. As a result, the drug deposition asymmetry also changes significantly, leading to a 7.51 times higher film thickness in the right lung for the extreme cases, compared to 2.49 and 0.07 times in the similar moderate and mild stenosis cases, respectively. Clinically, extreme stenosis promotes localized drug accumulation and non-uniform aerosol delivery due to jet-induced asymmetric particle transport, highlighting the need for patient-specific inhalation therapy optimization.