Comparative study on the transport and deposition of dust mite fecal particles in the upper airway of Asian children with adenoid hypertrophy before and after surgery.

Adenoidectomy is a routine treatment for adenoid hypertrophy (AH), but its effect on allergen deposition in the upper airways remains unclear. In this study, anatomically realistic upper airway models of eight Asian children with AH and their post-operative counterparts were reconstructed. Based on experimentally validated models, the transport trajectories of dust mite fecal particles were simulated and tracked using a computational fluid dynamics-discrete phase model (CFD-DPM). The results demonstrated that as particle diameter increased, the nasal septum and vestibule gradually became major sites of fecal particle accumulation. A deposition peak was observed in the nasopharynx, with maximum deposition occurring at 20 μm. Airflow within the sinuses is weak, resulting in a particle deposition efficiency (DE) below 1 %. After adenoidectomy, nasopharyngeal airflow became smoother, accompanied by a marked reduction in 1-50 μm particle deposition. Differences in overall nasal cavity deposition before and after surgery are minimal (< 2 %). The final deposition location of particles in the nasal cavity is highly dependent on their initial entry path through the nostrils. These findings highlight that particle deposition in children with AH is highly dependent on particle size. Adenoidectomy markedly improves nasopharyngeal patency, reduces allergen retention, and supports more effective targeted delivery of therapeutic aerosols.