title: Effect of airflow and material models on tissue displacement for surgical planning of pharyngeal airways in pediatric down syndrome patients.
abstract: Pharyngeal narrowing in obstructive sleep apnea (OSA) results from flow-induced displacement of soft tissue. The objective of this study is to evaluate the effect of airflow parameters and material model on soft tissue displacement for planning surgical treatment in pediatric patients with OSA and Down syndrome (DS). Anatomically accurate, three-dimensional geometries of the pharynx and supporting tissue were reconstructed for one pediatric OSA patient with DS using magnetic resonance images. Six millimeters of adenoid tissue was virtually removed based on recommendations from the surgeon, to replicate the actual adenoidectomy. Computational simulations of flow-induced obstruction of the pharynx during inspiration were performed using patient-specific values of tissue elasticity for pre and post-operative airways. Sensitivity of tissue displacement to selection of turbulence model, variation in inspiratory airflow, nasal airway resistance and choice of non-linear material model was evaluated. The displacement was less sensitive to selection of turbulence model (10% difference) and more sensitive to airflow rate (20% difference) and nasal resistance (30% difference). The sensitivity analysis indicated that selection of Neo-Hookean, Yeoh, Mooney-Rivlin or Gent models would result in identical tissue displacements (less than 1% difference) for the same flow conditions. Change in pharyngeal airway resistance between the rigid and collapsible models was nearly twice for the pre-operative case as compared to the post-operative scenario. The tissue strain at the site of obstruction in the velopharyngeal airway was lowered by approximately 84% following surgery. Inclusion of tissue elasticity resulted in better agreement with the actual surgical outcome compared to a rigid wall assumption, thereby emphasizing the importance of pharyngeal compliance for guiding treatment in pediatric OSA patients.
authors.affiliation: Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH, USA.
authors.forename: Dhananjay Radhakrishnan
authors.initials: DR
authors.lastname: Subramaniam
authors.affiliation: Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors.forename: Goutham
authors.initials: G
authors.lastname: Mylavarapu
authors.affiliation: Division of Pediatric Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fleck
authors.affiliation: Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Pediatrics, University of Cincinnati, College of Medicine, Cincinnati, OH, USA.
authors.forename: Raouf S
authors.initials: RS
authors.lastname: Amin
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, University of Cincinnati Medical Center, Cincinnati, OH, USA; Division of Pediatric Otolaryngology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors.forename: Sally R
authors.initials: SR
authors.lastname: Shott
authors.affiliation: Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH, USA; Department of Otolaryngology - Head and Neck Surgery, University of Cincinnati Medical Center, Cincinnati, OH, USA. Electronic address: ephraim.gutmark@uc.edu.
authors.forename: Ephraim J
authors.initials: EJ
authors.lastname: Gutmark
mesh_terms: D002648:Child; D003198:Computer Simulation; D004314:Down Syndrome / Q000150:complications*; D006801:Humans; D008279:Magnetic Resonance Imaging; D010614:Pharynx / Q000601:surgery*; D020181:Sleep Apnea, Obstructive / Q000601:surgery*
keywords: Flow; Pharyngeal airway; Sleep apnea; Tissue displacement; Virtual surgery