[Study on simulated airflow dynamics of children with obstructive sleep apnea treated by different surgical methods]

Objective:To analyze the effects of adenoidectomy, tonsillectomy and tonsillectomy combined with adenoidectomy on obstructive sleep apnea children by computational fluid dynamics numerical simulation. Methods:A case of typical tonsil with adenoid hypertrophy was selected. Mimics 21.0 software was used to establish the original preoperative model, adenoidectomy, tonsillectomy and virtual surgical models of tonsillectomy combined adenoidectomy, and the computational fluid dynamics model of the upper airway was established by ANSYS 2019 R1 software, and then the pressure and velocity of the internal flow field of the CFD model were numerically simulated. Seven planes perpendicular to the flow trace were selected as the observation planes, including the cross section of the sinusostoma complex, the anterior end of the adenoid body, the narrowest cross section of the nasopharyngeal cavity, the pharyngostoma tube, the narrowest cross section of the oropharyngeal cavity, the lower pole of the tonsil and the glottis section. The comparison indexes included pressure, flow velocity and flow distribution. Results:Compared with the original model before operation, after the adenoids were removed only, the pressure drop between the section of the ostiomeatal complex and the section of the eustachian tube decreased, the high velocity peak at the anterior end of the adenoids disappeared, and the flow trace through the middle nasal canal increased. When only bilateral tonsils were removed, the pressure drop between the eustachian tube and the glottis slowed down and the flow velocity between the eustachian tube and the glottis slowed down. Combined tonsillar-adenoidectomy resulted in the most uniform pressure distribution, the most gentle pressure change and flow rate in the upper airway, and the most ignificant increase in airflow trace through the middle nasal canal among the three operations. Conclusion:Adenoidectomy, tonsillectomy and combined tonsillar adenoidectomy can make the airflow velocity and pressure of upper respiratory tract uniform to different degrees, but there are obvious differences in the specific anatomical location and degree. The application of CFD can intuitively predict the improvement of upper airway flow field in OSA children by different surgical methods, which helps clinicians to make surgical decision.