Transport and deposition of inhalable aerosol drug particles in the human respiratory tract: variations across lung zones and the impact of breath-holding.

Abstract

The transport and deposition of drug particles within patient's respiratory systems played a vital role in determining the therapeutic effectiveness of inhalation therapy. This study focused on transport of inhalable particles to different lung lobes and the influences of breath-holding. An in vitro simulation system including a 3D printed respiratory tract, a respiratory pattern simulator and special-designed particle collectors was built for investigating transport of drug particles to different lung zones. A corresponding computational fluid dynamics (CFD) model was also constructed. A transport ratio, ω_T, and a deposition ratio, ω_D, were defined for comparatively studying particles delivered to different lung lobes and deposited to different locations in the respiratory tract. In vitro experimental results revealed significant higher ωT to the left lung (29.1 % ± 4.2 %) compared to the right one (22.1 ± 4.4 %) under normal breathing condition, while ωT to the left upper (14.4 % ± 3.1 %) and left lower lobes were greater (14.6 % ± 2.8 %) than to the right lower lobe (10.5 % ± 3.0 %) than to the right middle and upper lobes (5.7 % ± 1.2 % and 6 % ± 2.0 %, respectively), and these results were in consistent to numerical simulation results. The results also showed that breath-holding increased nasal deposition ω_D by 31-65 %, but had little effects on overall ω_T to different lung lobes. These findings highlighted the role of airway anatomy and airflow dynamics in particles delivery, offering insights for optimizing inhalation therapy by identifying key mechanisms of aerosol transport and deposition.