A computational fluid dynamics analysis of the effects of size and shape of anterior nasal septal perforations

Background: Nasal septal perforations (NSPs) often cause bleeding, crusting, obstruction, and/or whistling. The objective was to analyze the impact of anterior NSP size and shape on nasal physiology using computational fluid dynamics (CFD). Methods: A 3-dimensional model of the nasal cavity was constructed from a radiologically normal CT scan using imaging software. Anterior NSPs (ovoid (ONSP): 0.5, 1, 2, and 3 cm long anterior-to-posteriorly and round (RNSP, 0.5 and 1 cm)) were virtually created in the model and divided into ventral, dorsal, anterior, and posterior regions. Steady-state inspiratory airflow, heat, and water vapor transport were simulated using Fluent (TM) CFD software. Air crossover through the perforation, wall shear, heat flux, water vapor flux, resistance, and humidification were analyzed. Results: Air crossover and wall shear increased with perforation size. Regionally, wall shear and heat and water vapor flux were highest posteriorly and lowest anteriorly, generally increasing with size in those regions. RNSPs had greater heat and water vapor flux compared to corresponding size ONSPs. Resistance decreased by 10% or more from normal only in the 3 cm ONSP. Maximum water content was achieved more posteriorly in larger NSP nasal cavities. Conclusions: High wall shear and heat and water vapor flux in posterior perforation regions may explain the crusting most commonly noted on posterior NSP edges. This preliminary study suggests that larger NSPs have a greater effect on nasal resistance and water content. Decrease in resistance with larger NSP size may be implicated in reported symptomatic improvement following enlargement of NSPs for treatment.