Pilot Study of Nasal Anatomic and Functional Contributions to Odor Identification Variability

The role of conductive factors on olfactory acuity has received little attention. The relationships between nasal anatomy, inspiratory airflow and olfaction remain unclear, including if nasal anatomic and functional factors account for some variabilities in odor identification in the absence of sensorineural defects. This preliminary study aimed to analyze olfactory cleft airflow dynamics using computational modeling techniques and to develop linear regression models linking smell identification scores to nasal anatomy and computational-derived functional metrics.

Computational fluid dynamics modeling was used to generate nasal airflow-related parameters based on radiographic images of 10 subjects with varying olfactory acuity, but without prior nasal surgery or nasal deformity. Olfaction was assessed using the University of Pennsylvania Smell Identification Test (SIT).

Average olfactory airflow volume comprised only 2.43% of total nasal airflow volume. Higher olfactory resistance demonstrated strong associations with higher SIT scores. No one particular anatomic or functional parameter correlated strongly with SIT score. However, the 3-parameter linear regression model comprising bilateral nasal surface area-to-volume ratio, bilateral nasal resistance and olfactory resistance accounted for 82% of the variations in SIT scores (P = .01). Among 2-parameter linear regression models, the model comprising bilateral nasal surface area-to-volume ratio and bilateral nasal resistance accounted for 52% of SIT score variability (P = .08).

These findings demonstrate that a significant portion of variability in SIT scores can be explained by the combination of nasal resistance, olfactory resistance, and nasal surface area-to-volume ratio, suggesting that nasal anatomy and airflow-related quantities contribute toward variability in olfaction.

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