Aerosol Deposition Characteristics during Exhalation Through Nose Treatment: Relationship between Impaction Parameter and Deposition Ratio

Abstract

Aerosol medicine exhalation through the nose treatment (ETN) has conducted as an effective treatment for Eosinophilic Chronic Rhinosinusitis (ECRS). In ETN, the patient inhales aerosol of inhaled corticosteroid (ICS) medicine from mouth using portable inhaler. Then a part of the aerosol still floas and remains in upper airway. When the patient exhales inhaled air through the nose, the aerosol is effectively transported on the walls of middle meatus and olfactory fissure. The mechanism of how ETN improves ECRS with asthma is still controversial even though ETN gets a lot of attention as a treatment method for ECRS with asthma. In this study, computational fluid dynamics (CFD) analysis of aerosol transport phenomena were performed based on patient CT data in order to evaluate the therapeutic effect of ETN numerically. Three cases were selected in this study, one is a patient who had ECRS with asthma and a history of endoscopic sinus surgery and the others are healthy cases. 3D anatomically accurate patient-specific models were reconstructed from the data obtained using multidetector CT scanner with medical imaging software package. The entire series was loaded into the software, and then the nasal-pharynx airway was identified in each of the axial images based on predefined threshold of - 300 Housfield units relative to the surrounding tissue. The nasal-pharynx airway models were exported into a CFD meshing software package to generate discrete volume cells. This study used both a Euler-Lagrange particle transport model for aerosol transport and a model for complex intranasal turbulent flow. This study analyzed both inhaled state and exhaled state, and compared the aerosol deposition characteristics under conditions by changing the particle diameter and flow rate of aerosol. As a result of CFD analysis, amount of aerosol deposition depended on particle diameter and flow rate, and tendency of aerosol deposition was consistent in all cases analyzed in this study. Furthermore, in the inhaled state, aerosol mainly deposited in nasal meatus areas where not contribute to treatment of ECRS. Exhaled state was more effective treatment for ECRS compared to the inhaled state. The results show advantages of ETN as well as CFD analysis will contribute further development of ENT.