Evaluation of Particle Deposition Efficiency in Human Oral Passage: A CFD Study

Targeted drug-aerosol delivery in human respiratory airway has become a popular method for specific disease treatment with costly and/or aggressive medicine, and a standard procedure for treating quite a few respiratory diseases. However, the efficiency of targeted drug-aerosol delivery is still a problematic issue due to the complex geometry of human upper airways. In this study, CT scans of a male subject were obtained to reconstruct a 3D model of human oral passage. The airway was extended to a hemi sphere region representing for zero gauge pressure boundary condition. Velocity magnitude was applied at the hypopharynx. Sinusoidal variation of velocity corresponding to ventilation rate of both 7.5 and 15 L/min was simulated. Particles with diameters of 1, 8, 15, 22 and 31 μm were released near the mouth. These particles were released in three directions: parallel to the oral airway, 30 degree above the oral airway and 30 degree below the oral airway. And the particles were released at three different initial speeds, 0, 2.5 and 5 m/s. For each of the above categories, 10,000 particles were released. The deposition efficiency (DE) was found to generally increase with particle sizes. In most of the cases, the DE increased with initial released velocity. With release angles of 30 and -30 degree, the DE increased greatly for initial velocity magnitudes from 0m/s to 2.5m/s but would increase at a slower rate for initial velocity magnitudes from 2.5m/s to 5m/s. Compared to higher global airflow rate (15 L/min), at 7.5 L/min the DE is generally larger for particle size below 15 μm, but smaller for particle size above.