Particle transport and deposition analysis in diseased and stented upper airways: a parametric study

The aim of the present work is the evaluation of particle transport and deposition under different conditions of the airway model. Since chronic obstructive pulmonary disease is becoming the fourth leading cause of death worldwide, it is clear that studying airflow and particles dynamics in pre- and postoperatory condition is quite important for health- risk assessment and improving drug aerosol therapies. Particular attention has been given to stenotic and stented models because there are few studies in literature under realistic breathing conditions. The model used in this study is an idealized structure that comprehend an oral tract followed by the larynx with a restricted section to simulate the glottis, and a tracheobronchial tree with asymmetric branching of straight tubes. Stenotic trachea has been designed reducing the diameter of 20%, 30% and 50% of the original healthy size. The stents used in this analysis are the Dumon stent and the Y tracheobronchial stent, with different thickness. The healthy, stenotic and stented models have been analysed under normal and forced breathing conditions for different micro- particle sizes using computational fluid dynamics. It has been found that deposition is enhanced on the bifurcation after the stenosis, for all particle diameters and degree of the stenosis. Moreover, re-adjustment of the flow at the central line makes the airflow enter the less-deviated right branch. Local overdoses is present on the stents, in percentage around 3 to 13%, increasing with the device thickness, particle size and flow rate. The aim of this work is to contribute to the understanding of particle transport and deposition in patients with airways diseases and that underwent surgery in order to improve their quality of life with proper therapies.