A model of airflow in the nasal cavities: Implications for nasal air conditioning and epistaxis

Background: A friction force is generated when moving air contacts the nasal walls, referred to as wall shear stress. This interaction facilitates heat and mass transfer between the mucosa and air, i.e., air-conditioning. The objective of this research was to study the distribution of wall shear stress within the nasal cavity to identify areas that contribute significantly to air-conditioning within the nasal cavity. Methods: Three-dimensional computational models of the nasal airways of five healthy subjects (three male and two female subjects) were constructed from nasal CT scans. Numerical simulations Of nasal airflow were conducted using the commercial computational fluid dynamics code Fluent 6 (Ansys, Inc., Canonsburg, PA). Wall shear stress was derived from the numerical simulation. Air-conditioning was simulated to confirm the relationship with wall shear stress. Results: Nasal airflow simulations predicted high wall shear stress along the anterior aspect of the inferior turbinate, the anteroinferior aspect of the middle turbinate, and within Little's area. Conclusion: The airflow simulations indicate that the inferior and middle turbinates and Little's area on the anterior nasal septum contribute significantly to nasal air-conditioning. The concentration Of wall shear stress within Little's area indicates a desiccating and potentially traumatic effect of inhaled air that may explain the predilection for spontaneous epistaxis at this site. (Am J Rhinol Allergy 23, 244-249, 2009; doi: 10.2500/ajra.2009.23.3308)