title: Simulating the nasal cycle with computational fluid dynamics.
abstract: OBJECTIVE
  (1) To develop a method to account for the confounding effect of the nasal cycle when comparing preoperative and postoperative objective measures of nasal patency. (2) To illustrate this method by reporting objective measures derived from computational fluid dynamics (CFD) models spanning the full range of mucosal engorgement associated with the nasal cycle in 2 subjects.
  
  
  METHODS
  Retrospective.
  
  
  METHODS
  Academic tertiary medical center.
  
  
  METHODS
  A cohort of 24 patients with nasal airway obstruction was reviewed to select the 2 patients with the greatest reciprocal change in mucosal engorgement between preoperative and postoperative computed tomography (CT) scans. Three-dimensional anatomic models were created based on the preoperative and postoperative CT scans. Nasal cycling models were also created by gradually changing the thickness of the inferior turbinate, middle turbinate, and septal swell body. Moreover, CFD was used to simulate airflow and to calculate nasal resistance and the average heat flux.
  
  
  RESULTS
  Before accounting for the nasal cycle, patient A appeared to have a paradoxical worsening nasal obstruction in the right cavity postoperatively. After accounting for the nasal cycle, patient A had small improvements in objective measures postoperatively. The magnitude of the surgical effect also differed in patient B after accounting for the nasal cycle.
  
  
  CONCLUSIONS
  By simulating the nasal cycle and comparing models in similar congestive states, surgical changes in nasal patency can be distinguished from physiological changes associated with the nasal cycle. This ability can lead to more precise comparisons of preoperative and postoperative objective measures and potentially more accurate virtual surgery planning.
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Ruchin G
authors.initials: RG
authors.lastname: Patel
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA ggarcia@mcw.edu.
authors.forename: Guilherme J M
authors.initials: GJ
authors.lastname: Garcia
authors.affiliation: Division of Otolaryngology-Head and Neck Surgery, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: Dennis O
authors.initials: DO
authors.lastname: Frank-Ito
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.
authors.forename: Julia S
authors.initials: JS
authors.lastname: Kimbell
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Rhee
mesh_terms: D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D008953:Models, Anatomic; D009297:Nasal Mucosa / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D015508:Nasal Obstruction / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
keywords: computational fluid dynamics (CFD) simulations; mucosal cooling; nasal airway obstruction; nasal cycle; nasal resistance; nasal surgery; septoplasty