Customized three-dimensional computational fluid dynamics simulation of the upper airway of obstructive sleep apnea

Objective: To use computer simulations to describe the role of fluid dynamics in the human upper airway. Materials and Methods: The model was constructed using raw data from three-dimensional (3-D) computed tomogram (CT) images of an obstructive sleep apnea (OSA) patient. Using Bionix® software (CantiBio Inc., Suwon, Korea), the CT data in DICOM format was transformed into an anatomically correct 3-D Computational fluid dynamic (CFD) model of the human upper airway. Once constructed, the model was meshed into 725,671 tetra-elements. The solution for testing was performed by the STAR-CD software (CD adapco group, New York, NY). Airflow was assumed to be turbulent at an inspiration rate of 170, 200, and 230 ml/s per nostril. The velocity magnitude, relative pressure, and flow distribution was obtained. Results: High airflow velocity predominated in medial and ventral nasal airway regions. Maximum air velocity (15.41 m/s) and lowest pressure (negative 110.8 Pa) were observed at the narrowest portions of the velopharynx. Considering differences in model geometry, flow rate, and reference sections, when airflow patterns in nasal cavity were compared, our results were in agreement with previous data. Conclusions: CFD analyses on airway CT data enhanced our understanding of pharyngeal aerodynamics in the pathophysiology of OSA and could predict the outcome of surgeries for airway modification in OSA patients.