Deposition Characteristics of Inhalable Particles With Different Diameters in the Human Lower Respiratory Tract

ABSTRACT Inhalable particles entering the respiratory system contribute significantly to respiratory diseases. Using a three‐dimensional model of the adult lower respiratory tract reconstructed from CT data (trachea to segmental bronchi), this study numerically investigated the deposition characteristics of monodisperse particles (0.1–10 μm). Simulations were performed under calm breathing (Q = 30 L/min) using computational fluid dynamics coupled with a discrete phase model. Deposition was analyzed for nine individual particle diameters and for an equal‐proportion mixture. Results indicate that particles predominantly deposit in the left and right main bronchi. As particle diameter increases, the primary deposition site shifts from the bronchi to the tracheal inlet, and subsequently to the upper and lower lobar bronchi. Quantitatively, deposition ranged from 1 particle (0.1 μm) to 113 particles (10 μm) out of 342 injected, corresponding to deposition rates of 0.29% and 33.04%, respectively. These findings provide precise, location‐specific deposition data and elucidate the mechanisms governing particle motion. This work establishes a scientific foundation for understanding respiratory particle dynamics, with implications for assessing the pathogenic effects of particulate matter and advancing inhalable drug delivery systems.