The effect of anatomical structures on particle transport mechanisms in the human upper airway

Abstract

The human upper airway exhibits complex and variable geometry, yet few studies have examined the impact of specific anatomical structures on drug deposition. This thesis systematically isolates key pharyngeal features—the uvula, epiglottis, and soft palate—to assess their influence on airflow and particle deposition in a realistic airway model.

Using Computational Fluid Dynamics (CFD), simulations of 3 µm particles revealed that widening the soft palate region significantly reduces upper airway deposition, while the removal of the uvula and epiglottis alters flow dynamics and regional deposition but has minimal effect on total pharyngeal deposition. These findings were validated through experimental studies using Next-Generation Impaction (NGI) and High-Performance Liquid Chromatography (HPLC), confirming that increased airway space enhances fine particle fraction (FPF) and reduces deposition.

Additionally, the study highlights that inhaler resistance and airway anatomy significantly impact lung dose efficiency. While NGI and HPLC effectively measure total deposition, they lack the capability for real-time regional deposition analysis. To address this, a novel laser-photodiode method was developed, enabling real-time tracking of aerosol dynamics, particle velocity, and regional deposition. This technique offers a practical, high-resolution approach for studying drug transport in the human airway, bridging the gap between experimental and computational models.