Analysis of upper airway flow field between obstructive sleep apnea and normal children based on computational fluid dynamics

Objective:In this study, the characteristics of the upper airway flow field were analyzed by using computational fluid dynamics（CFD）. The study analyze the differences in the upper airway flow field between normal children and children with obstructive sleep apnea（OSA）, and the pathological characteristics of children with OSA were elaborated from the perspective of airway fluid dynamics. Methods:The upper airway models of a normal child and a child with OSA were constructed. The differences in the same inspiration pressure, such as airflow velocity, airflow pattern, ventilation volume, and pressure, were analyzed. To verify CFD results, rhinomanometry was carried out and an experimental bench based 3D technology was also built. Results:The CFD results are consistent with the in vitro 3D model experiments and clinical measurement results. The adenoid area of nasopharynx is only 11.274 mm²of the child with OSA, about 1/6 of that of normal children. At the area of nasopharyngeal in OSA children, the flow velocity increased but the pressure dropped sharply, which was 69.197% of the total pressure drop, and the resistance value was 6.59 times of that of normal children. Streamline of nasopharyngeal is more disorder. Normal children's inspiratory flow was 116.139 mL/s, while OSA children's inspiratory flow was 47.055 mL/s, with a difference rate as high as 59.48%. Conclusion:The airflow of OSA children in nasopharynx is significantly different from that of normal children. The airflow characteristics of upper airway were discussed in detail with the use of CFD, which can help clinicians intuitively understand the abnormal flow behavior of children with OSA.