A computational model of upper airway collapsibility

A computational model is being developed to investigate pharyngeal collapsibility, pertinent to obstructive sleep apnea. The geometrical structure of the pharyngeal airway is constructed from mid-sagittal plane MR images from normal subjects. The genioglossal muscle activation is simulated by a pressure and state dependent contraction module. This model establishes a direct connection between the contractile forces and the measured electromyogram signals at various upper airway conditions and effectively avoids the difficulty in determining the muscle shortening velocity at complex pharyngeal conditions when modeling muscle contractions. Using the finite element method, we simulate the genioglossal muscle activation behaviors and mimic air flow, tissue deformation and collapse under negative pharyngeal pressures. Using our model, we simulate mandibular advancement and show it to change the collapsibility markedly. A 1-cm advancement decreases pharyngeal closing pressure from -13 to about -20 cmH₂O. The present study shows that a realistic computational model can simulate pharyngeal collapsibility and potentially improve the treatment of sleep apnea.