Computational Fluid Dynamics Analysis And Experimental Study Of The Upper Airway Of Children

In recent years,children's obstructive sleep apnea-hypopnea syndrome(OSAHS)has a high incidence,which seriously affects physical and mental health and growth.Animals and carcasses do not reflect body constitution and it is difficult to obtain clear and intuitive flow field by the experiment.On the contrary,computational fluid dynamic(CFD)that can clearly capture flow characteristics,reduce time and cost has been widely used in the study of OSAHS.However,there are still many problems.For example,the research subjects are mainly adults;CFD method has not been unified;there are many numerical simulations and no experiment;there is a lack of research on basic medical issues.Therefore,this paper carried out CFD analysis and experiments on children's upper airway.The main work is as follows:(1)The three-dimensional model of children's upper airway was built by using CT images.The influence of different CFD methods(boundary conditions and flow models)on the inspiration flow was analyzed.The model was printed with 3D printing technology.The experiment and rhinomanometry were conducted to verify CFD methods.(2)The upper airway models of normal children and children with OSAHS were constructed,and the difference of inspiratory airflow was studied.The velocity,pressure drop and resistance in the nasopharyngeal adenoid were 2.492,9.893 and 6.592 times of those of normal children,and the discrepancy rate of ventilation volume was up to 59.484%.Subsequently,adenoidectomy was performed,and postoperative flow characteristics were similar to those of normal children.(3)The upper airway models with different adenoid sizes were established to reasearch the influence of adenoid size on inspiratory airflow.When stenosis resulted by adenoid was above 64%,the velocity increased,the pressure decreased and the streamline was irregular in the nasopharyngeal adenoid;and the ventilation volume decreased.The result verifies that when adenoid hypertrophy obstructs the airway more than 2/3,the children show symptoms such as snoring and shortness of breath.(4)The upper airway models with different tonsil sizes were constructed to investigate the effect of tonsil size on inspiratory airflow.When the tonsil reached three-degree,the velocity increased and the pressure decreased in the oropharyngeal tonsil;and the air volume decreased.The tonsil is larger,the phenomenon is more obvious.The result confirms that the tonsil above three-degree has an impact on ventilation,which should be treated in time.(5)The upper airway models of normal,adenoid hypertrophy,tonsil hypertrophy,and adenoid with tonsil hypertrophy were constructed to study the impact of adenoid and tonsil on inspiratory airflow.When adenoid was hypertrophied,tonsil hypertrophy had less effect on the upper airway inspiratory airflow,and the influence of adenoid hypertrophy on ventilation volume was much greater than that of tonsil hypertrophy.The result verifies that children with adenoid hypertrophy are more easily to develop OSAHS than children with tonsil hypertrophy.