![]() Pharyngeal collapse in pediatric patients with Down syndrome (DS) results from hypotonia, obesity, midface hypoplasia, relative macroglossia, large tonsils and adenoids (Shott et al., 2006). ![]() High AHI or positive values of P crit indicate greater OSA severity. ![]() The number of events per hour when airflow reduces or ceases to flow in the pharynx is referred to as the Apnea-Hypopnea index (AHI) (Ruehland et al., 2009). P crit is the critical value of transmural pressure resulting in complete pharyngeal obstruction (Patil et al., 2004). Moreover, negative pressures generated during inspiratory airflow have been hypothesized to result in upper airway collapse (Roberts et al., 1985). Narrow airways or extremely compliant tissue supporting the pharynx enhance the probability of sleep disorders such as snoring and obstructive sleep apnea (OSA) (Suratt et al., 1984). 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.Īirway narrowing is likely to occur when forces promoting airway collapse exceed the forces in soft tissue tending to dilate the airway (Bilston and Gandevia, 2014). The tissue strain at the site of obstruction in the velopharyngeal airway was lowered by approximately 84% following surgery. 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 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. 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). 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. 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. Six millimeters of adenoid tissue was virtually removed based on recommendations from the surgeon, to replicate the actual adenoidectomy. Anatomically accurate, three-dimensional geometries of the pharynx and supporting tissue were reconstructed for one pediatric OSA patient with DS using magnetic resonance images. 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). ![]() Pharyngeal narrowing in obstructive sleep apnea (OSA) results from flow-induced displacement of soft tissue. ![]()
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