基于逆向工程的人体气道重建及其流场分析

Reconstruction and Flow Field Analysis of Human Airway Based on Reverse Engineering

目的针对老年人气管萎缩导致整体气道尺寸变小的情况,研究狭窄气道重建及不同呼吸状态下空气流场对气道的影响。方法运用Mimics建立人体气道的三维模型,利用计算流体动力学方法对气道内的流场进行仿真,分析并比较不同呼吸状态下气管内壁压强及其气流的分布状态。结果在不同呼吸状态下,气管内壁压强数值在主气管内壁相对均匀,但在支气管狭窄段的气流入口处出现明显下降,在最狭窄的区域附近达到负压。气流速度从气管管道中心向边界层递减,流速在狭窄处达到最大值。气流穿过狭窄区域后产生涡流,且入口流速越大,正压和负压压强越大,狭窄处压降越明显,涡流现象越明显。结论气道狭窄区域因负压造成继续收缩,会导致病人呼吸困难,而涡流会使气管壁受到气动剪切应力的影响可能损伤气道壁黏膜。因此,了解萎缩狭窄气道内的压强分布及流速分布情况,可为此类病变气道的临床诊治提供参考依据。

Objective In view of the situation that tracheal atrophy causes the overall airway size to become smaller in the elderly,effects of the airway wall surface on reconstruction of a narrow airway and the airflow field under different respiratory conditions were investigated.Methods A three-dimensional(3D)model of human airway was established by using Mimics,and flow field in the airway was simulated by computational fluid dynamics(CFD)method.The inner wall pressure and the distribution of airflow were analyzed and compared under different breathing states.Results Under different respiratory states,the pressure of endotracheal wall was relatively uniform in the endotracheal wall,but decreased significantly in air inlet of the bronchial stenosis segment,and reached negative pressure near the narrowest area.The airflow velocity decreased from the center of the pipe to the boundary layer,and the velocity reached the maximum at the narrow area.Vortex was generated when airflow passed through the narrow area,and the larger the inlet flow velocity was,the larger the positive pressure and negative pressure were,the more obvious the pressure drop at the narrow area was,and the more obvious the vortex phenomenon was.Conclusions The constriction of the airway stenosis area caused by negative pressure will lead to the patient’s dyspnea,and the eddy current will cause the airway wall to be affected by the aerodynamic shear stress and may damage the airway wall mucosa.Therefore,understanding of the pressure distribution and velocity distribution in the narrow airway can provide references for clinical diagnosis and treatment of such diseased airways.