Evaluation of Obstructive Sleep Apnea Syndrome by Computational Fluid Dynamics

Abstract

The amelioration of obstructive sleep apnea syndrome (OSAS) by maxillomandibular advancement (MMA) surgery can be predicted by analyzing anatomical airway changes with 3-dimensional (3D) geometrical reconstruction and computational fluid dynamics. Computer Enabling Technology Lab (ETLab) and Computational Simulation Lab (CSLab) can be used to analyze anatomic airway change for previously operated patients with a clinical cure of OSAS. MMA surgery reduces airway resistance and pressure effort (gradient) of OSAS by increasing the dimension of the airway. ETLab has been used to reconstruct the upper airway as a 3D computer model (bone and soft tissue surrounding the pharyngeal airway) from existing helical computed tomography scan format of OSAS patients. ETLab can compare and construct the geometry with numerical meshes of the airway between pre- and postoperative MMA by the use of bioengineering software. This technology uses high-fidelity computation fluid dynamic simulations, developed at the CSLab, for prediction and analysis of the flow field in the airway for pre- and postoperative MMA. It is possible to use the simulation to predict the likely success of future treatment and develop a prognostic factor. The soft- and hard-tissue mesh is used to determine the pre- and postoperative differences in the facial and pharyngeal tongue base for soft-tissue change associated with hard-tissue movement. This correlation predicts the amount of surgical movement necessary to create an adequate airflow. These results help define the surgical techniques in OSAS for more precise identification of upper airway anatomical features. This process correlates the area and pressure change at the velopharynx, oropharynx, and retroglossal space of the upper airway by the ETLab. Results can compare with polysomnogram and cure rates. 3D computer analysis can be used to test flow dynamics in the human airway for surgical treatment of OSAS.