Rhinomanometry Versus Computational Fluid Dynamics: Correlated, but Different Techniques

Area of Science:

• Biomedical Engineering
• Respiratory Medicine
• Medical Imaging

Background:

• Previous studies indicate a low correlation between computational fluid dynamics (CFD) and rhinomanometry (RMN) for nasal resistance assessment.
• The discrepancy's source between subjective and objective nasal patency measures remains unclear.

Purpose of the Study:

• To investigate the correlation and agreement between nasal resistance calculated via CFD (R_CFD) and measured by RMN (R_RMN).
• To examine the correlation between objective (R_CFD, R_RMN) and subjective (visual analog scale - VAS) measures of nasal patency.

Main Methods:

• Twenty-five patients with nasal obstruction underwent RMN before and after oxymetazoline decongestion.
• Subjective nasal patency was assessed using a VAS.
• CFD simulations were based on CT scans, and validated using in vitro experiments (R_EXPERIMENT) on nasal replicas.

Main Results:

• Mucosal decongestion significantly reduced nasal resistance and improved subjective airflow sensation.
• A strong correlation (r=0.96) and good agreement were found between R_CFD and R_EXPERIMENT.
• A moderate correlation (r=0.41) was observed between R_CFD and R_RMN, with CFD underpredicting resistance. Correlation improved (r=0.76) when comparing unilateral airflow at 75 Pa.

Conclusions:

• CFD and RMN show moderate correlation, but CFD underestimates in vivo nasal resistance, potentially due to assuming rigid nasal walls.
• Subjective nasal patency correlates better with unilateral airflow measurements and in the context of interventions, aligning with prior research.