A Method to Quantify the Confounding Effect of the Nasal Cycle on Nasal Airway Obstruction

Abstract

Objectives: (1) Develop a methodology to eliminate the confounding effect of the nasal cycle when comparing pre- and postsurgery nasal resistance measurements. (2) Illustrate this methodology by reporting nasal resistances derived from computational fluid dynamics (CFD) simulations in a test subject using computational models that span the full range of mucosal engorgement associated with the nasal cycle. Methods: A cohort of 40 nasal airway obstruction patients was reviewed to select the one patient with the greatest reciprocal change in turbinate engorgement between pre- and postsurgery computed tomography (CT) scans. Ten 3-dimensional anatomically accurate nasal cycling CFD models were created based on the pre- and postoperative CT scans. The thickness of the inferior turbinate, middle turbinate, and septal swell body was systematically increased/decreased by adding/removing layers of pixels around these structures using medical imaging software. Results: After surgery (septoplasty), without adjusting for the nasal cycle, nasal resistance decreased by 17% on the left side and by 69% on the right side, and total resistance decreased by 53%. However, after adjusting for cycling, the unilateral nasal resistance decreased by 50% and 43% on the left and right sides respectively, while bilateral resistance decreased by 47%. Conclusions: By simulating the nasal cycle using computational models, changes in nasal resistance due to surgery can be distinguished from physiological changes due to the nasal cycle. This ability can lead to more precise objective comparisons of pre- and postsurgery nasal resistance measurements and potentially more accurate virtual presurgery planning.