Potential Effects of Inspiratory Airflow Patterns at the Nostrils on Predictions of Particle Deposition Efficiency in Human Nasal Passages. J. S. Kimbell, D. Kalisak, and B. Asgharian, CIIT Centers for Health Research
Computational fluid dynamics simulations of regional nasal particle deposition provide information about specific nasal deposition sites and nasal filtering capabilities for lung protection. Initial comparisons of predicted nasal deposition efficiency with measured values in the literature showed that simulations overpredicted nasal deposition for particles with mass median aerodynamic diameter (MMAD) < 2 mm entering at steady-state inspiratory flow rates of 7.5 or 15 L/min. Initially, inspiratory airflow simulations were conducted with uniform airflow vectors imposed on the nostrils pushing air into the nasal passages (plug flow conditions at the inlet). Subsequently, simulations were run with airflow vectors imposed at the nasopharynx that pulled airflow through the nasal passages, resulting in a more physiologic airflow profile at the nostrils. Nasal deposition efficiencies for these two cases were compared for simulations at equal flow rates. Preliminary simulations indicated that the use of physiologic flow conditions at the nostrils (i.e., pulling air into the nose from the nasopharynx) reduced predictions of nasal deposition efficiency for 2 mm particles by more than 7-fold over predictions made using plug flow conditions at the inlet. These results suggest that for small particles (<2 mm MMAD) or low inspiratory flow rates such as resting breathing conditions, the probability that particles deposit in the nasal passages is sensitive to initial particle velocity. The accuracy of the manner in which inspiratory airflow is simulated at the nostrils may have a significant impact on the accuracy of nasal deposition efficiency predictions.
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