B7: Computational Bioengineering IV

FLOW VISUALIZATION FOR NASAL CAVITY FLOW IN AEROSOL EXHALATION THROUGH NOSE TREATMENT


Takahisa Yamamoto1, Yoshiki Kobayashi2, Shunpei Shikano1, Masahiro Takeyama1, Mikiya Asako2


1National Institute of Technology Gifu College, Japan;
2Kansai Medical University, Japan


Aerosol medicine exhalation through nose (ETN) is one of promising and comprehensive treatment methods for Eosinophilic Chronic Rhinosinusitis (ECRS) with asthma. In this treatment, the patient inhales aerosol of inhaled corticosteroid (ICS) medicine from mouth using portable inhaler. Then a part of the aerosol still floats 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. This study performed Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD) analysis for the transport phenomena of aerosol medicine during exhalation period to evaluate the curative effect of ETN numerically and  experimentally. A 3D anatomically accurate patient-specific model was reconstructed from the data obtained using multidetector CT scanner. This study used a Euler-Lagrange particle transport model for aerosol transport in CFD analysis. In addition, Particle Image Velocimetry (PIV) measurement was conducted using living-body model of nasal-pharynx airway in EFD analysis. As results of CFD and EFD analysis, ETN formed impinging flow toward upper wall of nasopharynx, subsequently complex swirl and circulation flow in the nasopharynx region. In addition, main flow of ETN passed upper region of nasal cavity. Such the tendencies affected on aerosol transport characteristics; a part of aerosol particles moved into ethmoindal sinuses. Total aerosol deposition amount during ETN depended on flow rate of exhalation. This tendency was more remarkable on the upper wall of nasopharynx. On the other hand, deposition rate of aerosol on the ethmoidal sinuses did not appear strong correlation with flow rate of exhalation. These results imply that both aerosol transport and deposition during ETN has non-stationary characteristics. 

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