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Effects of the laryngeal jet on nano- and microparticle transport and deposition in an approximate model of the upper tracheobronchial airways

Departments of ¹Mechanical Engineering and ³Pharmaceutics, Virginia Commonwealth University, Richmond, Virginia; ²Department of Systems Engineering, University of Arkansas, Little Rock, Arkansas; ⁴Department of Medicine, University of North Carolina, Chapel Hill, North Carolina; and ⁵CyberMedicine, Laguna Beach, California

Submitted 20 November 2007 ; accepted in final form 31 March 2008

The extent to which laryngeal-induced flow features penetrate into the upper tracheobronchial (TB) airways and their related impact on particle transport and deposition are not well understood. The objective of this study was to evaluate the effects of including the laryngeal jet on the behavior and fate of inhaled aerosols in an approximate model of the upper TB region. The upper TB model was based on a simplified numerical reproduction of a replica cast geometry used in previous in vitro deposition experiments that extended to the sixth respiratory generation along some paths. Simulations with and without an approximate larynx were performed. Particle sizes ranging from 2.5 nm to 12 µm were considered using a well-tested Lagrangian tracking model. The model larynx was observed to significantly affect flow dynamics, including a laryngeal jet skewed toward the right wall of the trachea and a significant reverse flow in the left region of the trachea. Inclusion of the laryngeal model increased the tracheal deposition of nano- and micrometer particles by factors ranging from 2 to 10 and significantly reduced deposition in the first three bronchi of the model. Considering localized conditions, inclusion of the laryngeal approximation decreased deposition at the main carina and produced a maximum in local surface deposition density in the lobar-to-segmental bifurcations (G2–G3) for both 40-nm and 4-µm aerosols. These findings corroborate previous experiments and highlight the need to include a laryngeal representation in future computational and in vitro models of the TB region.

respiratory fluid dynamics; aerosol deposition; microdosimetry; laryngeal jet; Coanda effect; tracheobronchial deposition patterns; respiratory drug delivery