Frictional resistance sheds light on the multicomponent nature of nasal obstruction: A combined in vivo and computational fluid dynamics study

• Geometrical and resistive properties of 3D-reconstructed rigid nasal cavities.
• Nasal perimeter increases with nasal area twice more than in circular tubes.
• Frictional resistance is inferred by computational fluid dynamics (CFD).
• In vivo rhinomanometry data obtained in humans are compared to CFD data.
• Nasal resistance is affected by compliance and the lack of geometrical similarity.

Exploring nasal flow contributes to better understanding of pathophysiological functions of nasal cavities. We combined the rhinomanometry measurements of 11 patients and computational fluid dynamics (CFD) simulations in 3 nasal airway models to dissect the complex mechanisms that determine nasal flow obstruction: spatial complexity and pressure-dependent deformability of nasal airways. We quantified spatial complexity by calculating longitudinal variations of hydraulic diameter, perimeter and area of nasal cavities, and their impact on flow characteristics by examining the longitudinal variations of the kinetic energy coefficient and the kinetic to potential energy ratio. Airway distensibility variably affected in vivo pressure–flow relationships through the appearance of flow-limitation patterns characterized by maximum flow and/or flow plateau. We quantified deformability and spatial complexity effects on nasal airway resistance by normalizing all data with averaged reference parameters. The results show that discrepancies in nasal flow resistances reflect airway deformability and geometrical complexity, and thereby constitute a framework to better characterize nasal obstruction.