2024 AIChE Annual Meeting
Using 3D Printing to Correlate Tonsil Size to Aerosol Deposition in the Upper-Airways
The anatomy of the upper respiratory tract plays a crucial role in determining local airflow dynamics; this is especially significant in pediatric airways, which continuously evolve and change throughout development (Kolewe et al. AAPS PHarmSciTech 2023). The tonsils, located in the upper airway region, are tissues prone to temporary swelling, which can limit airflow and change how inhaled aerosol medicines reach the lung. This work develops an experimental platform using 3D printing to evaluate the effect of tonsil size on the 1) local deposition of aerosolized therapeutics in the upper-airway and on the 2) amount of inhaled medicine that reaches the rest of the respiratory tract. Tonsil size is categorized by the Brodsky scale, which compares the distance between tonsils against that of the walls of the airway without tonsils. Each category in this scale is referred to as a grade, where a model with less than 25% difference in distance is referred to as grade 1, 26-50% is a grade 2, 51-75% is a grade 3, and 75+% is a grade 4. In this work, CT scans from pediatric patients (ages 3.5-4.7 years old) with various tonsil grades were used to create 3D printable models. Models were digitally split into three different sections according to their placement with respect to the tonsils: top (above tonsils), middle (tonsil area), bottom (below tonsils). After models were split, locking mechanisms were added to ensure easy reassembly, and parts were printed using a Carbon M1 printer. Nebulized doses of a fluorescent tracer (Rhodamine-B) were administered through the model under a fixed flow rate (~15 L/min); deposition in the different upper airway model areas and particle size leaving the model were evaluated. Results from these three patient models show different degrees of deposition as a function of tonsil grade, with generally more deposition in the top and middle segments of the upper-airway compared to the bottom section. On-going studies will continue these experimental evaluations with more models to build a correlation between local deposition and tonsil grade.