Effect of airflow and material models on tissue displacement for surgical planning of pharyngeal airways in pediatric down syndrome patients

Dhananjay Radhakrishnan Subramaniam; Goutham Mylavarapu; Robert J Fleck; Raouf S Amin; Sally R Shott; Ephraim J Gutmark

doi:10.1016/j.jmbbm.2017.03.007

Effect of airflow and material models on tissue displacement for surgical planning of pharyngeal airways in pediatric down syndrome patients

J Mech Behav Biomed Mater. 2017 Jul:71:122-135. doi: 10.1016/j.jmbbm.2017.03.007. Epub 2017 Mar 8.

Authors

Dhananjay Radhakrishnan Subramaniam¹, Goutham Mylavarapu², Robert J Fleck³, Raouf S Amin⁴, Sally R Shott⁵, Ephraim J Gutmark⁶

Affiliations

¹ Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH, USA.
² Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
³ Division of Pediatric Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
⁴ 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.
⁵ 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.
⁶ 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.

PMID: 28292706
DOI: 10.1016/j.jmbbm.2017.03.007

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.

Keywords: Flow; Pharyngeal airway; Sleep apnea; Tissue displacement; Virtual surgery.

MeSH terms

Child
Computer Simulation
Down Syndrome / complications*
Humans
Magnetic Resonance Imaging
Pharynx / surgery*
Sleep Apnea, Obstructive / surgery*

Grants and funding

R01 HL105206/HL/NHLBI NIH HHS/United States