Variability in oropharyngeal airflow and aerosol deposition due to changing tongue positions

Abstract

Human tongue is a highly compliant entity and its position has significant effects on the delivery efficiency of orally inhaled pharmaceuticals. However, studies of tongue postures on aerosol transport and deposition are rare due to technical challenges in developing such models. This study presents a computational oropharyngeal model with varying tongue shapes, which are representative of the positions a subject takes during pulmonary drug delivery. The affected airflow and aerosol behaviors were simulated using a well-validated computational fluid-particle tracking model. Results show that, depending on the extent of the morphology variations, tongue position can significantly alter the airflow pattern and particle behaviors in the oral cavity and the subsequent pharyngeal airway. The variability in the total oropharyngeal filtering rate was 6%–25% and varied with particles sizes and breathing conditions. Much higher differences were observed in the compartmental deposition fractions, with the most pronounced variations in the oral cavity. The effects from tongue positioning were also observed in the particle distributions that entered the lungs, which might further cause differences in the pulmonary deposition distributions. Results of this study indicate that the tongue position can be a key factor in administering therapeutic agents to conducting airways (e.g., bronchial asthma).