Abstract:Objective: To analyze the effect of adenoid size on the upper airway flow by constructing 8 differents upper airway finite element numerical models with the adenoid size decreasing successively in the same airway. So they will help clinicians to deeper understand the pathogenesis of adenoid in children with sleep apnea and to regulate the indications for adenoid surgery. Methods: Based on the CT scan of the upper airway, 8 differents upper airway three-dimensional models with decreasing adenoids in the same airway were constructed by 3D reconstruction software Amira.Computational Fluid Dynamics (CFD) is used to simulate the inspiratory airflow in each upper airway.The influence of the size of adenoids on the flow field characteristics of the upper airway was analyzed from the aspects of flow velocity, flow pattern, flow pressure and ventilation volume. Results:When the adenoid was enlarged and blocked within 55% of the nostril, the flow velocity and pressure of the quiet inspiratory were basically the same as that of the normal airway, the flow line was regular, and the ventilation volume was between 77.812 ~74.854 mL/s.When the degree of obstruction reached more than 64%, the nasopharyngeal airflow velocity and pressure drop sharply increased, streamline disorder, and the ventilation volume significantly reduced. Conclusion: Adenoid hypertrophy can seriously affect the normal aspiration of children when obstruction of nostril up to 2/3.The larger the adenoids, the more obvious the symptoms of suffocation, snoring, and apnea were.Adenoid hypertrophy is an important factor that causes Obstructive Sleep apnea-Hypopnea Syndrome (OSAHS)of children.