Effect of Anatomy on Human Nasal Air Flow and Odorant Transport Patterns: Implications for Olfaction

TLDR

Recent studies comparing CT or MRI images of nasal anatomy with olfactory sensitivity have found a correlation between specific anatomical areas and olfactory performance. The authors developed a rapid CFD method that converts individual nasal CT scans into anatomically accurate 3‑D models to predict airflow and odorant transport, potentially determining olfactory sensitivity. The CFD‑based 3‑D model can be quickly modified to represent anatomical deviations such as polyps and is used to simulate inspiratory and expiratory airflow with odorants via finite‑volume methods to assess how variations in the olfactory slit and nasal valve affect transport. Anatomical changes in the olfactory region and nasal valve strongly alter airflow and odorant transport, affecting olfactory function, and individualized CFD models can link such deviations to perceptual disturbances and guide therapeutic interventions.

Abstract

Recent studies that have compared CT or MRI images of an individual's nasal anatomy and measures of their olfactory sensitivity have found a correlation between specific anatomical areas and performance on olfactory assessments. Using computational fluid dynamics (CFD) techniques, we have developed a method to quickly (<few days) convert nasal CT scans from an individual patient into an anatomically accurate 3-D numerical nasal model that can be used to predict airflow and odorant transport, which may ultimately determine olfactory sensitivity. The 3-D model can be also be rapidly modified to depict various anatomical deviations, such as polyps and their removal, that may alter nasal airflow and impair olfactory ability. To evaluate the degree to which variations in critical nasal areas such as the olfactory slit and nasal valve can alter airflow and odorant transport, inspiratory and expiratory airflow with odorants were simulated using numerical finite volume methods. Results suggest that anatomical changes in the olfactory region (upper meatus below the cribriform plate) and the nasal valve region will strongly affect airflow patterns and odorant transport through the olfactory region, with subsequent effects on olfactory function. The ability to model odorant transport through individualized models of the nasal passages holds promise for relating anatomical deviations to generalized or selective disturbances in olfactory perception and may provide important guidance for treatments for nasal-sinus disease, occupational rhinitis and surgical interventions that seek to optimize airflow and improve deficient olfactory function.