成年人中心性气道流体力学特征分析

Analysis of fluid dynamics characteristics of central airway in adults

目的运用计算流体力学(CFD)技术对健康成年人中心性气道进行流体力学特征分析,研究空气流场对中心性气道的影响。方法选择4例健康成年人胸部CT影像,其中男性2例,女性2例;年龄26~53岁,平均年龄37.5岁;体质量48.5~74.0 kg,平均体质量60.6 kg。使用Mimics 21医学图像软件将4例健康成年人的胸部CT图像以医学数字成像与通信(DICOM)格式导入,并构建中心性气道的三维模型。对三维模型进行修整,使用Geomagic Studio 12软件。使用Ansys fluent 19.2软件的网格划分模块将模型进行网格划分。划分好网格后,将其导入Ansys 19.2软件进行CFD模拟计算。在模拟计算中,设定相同的潮气量,并对中心性气道内部气流流场变化进行动态分析。结果在基于CT图像数据构建的中心性气道的三维模型基础上,使用了CFD进行数值模拟。结果显示,在施加相同潮气量的情况下,气流入口速度为2.15~4.44 m/s。气道流速在从入口到出口的过程中逐渐降低,并形成了高流速的区域。气道最大流速的变化为3.25~6.77 m/s,并且最大流速靠近气管壁面。气道壁面压力由气管到支气管逐渐降低。在流速越高的区域,气道壁面压力的绝对值越高。气道壁面最大切应力变化为0.888~2.240 Pa,其中气管壁、气管分叉处及二级、三级支气管的切应力相对较大,并随着气管和支气管的直径减小而增加。结论通过对健康成年人中心性气道模型进行CFD模拟,发现气道流速、壁面压力、壁面切应力与气道结构有着密切的关系,呈现出一定的整体空间分布和局部特征。

Objective To analyze fluid mechanics characteristics of central airway in healthy adults by using computational fluid dynamics(CFD)technique,and study influence of air flow field on central airway.Methods Four healthy adult chest CT images were selected,which included 2 males and 2 females,aged 26-53 years old with mean age of 37.5 years old;body mass was 48.5-74.0 kg with mean body mass of 60.6 kg.Four chest CT images were imported in DICOM format using Mimics 21 medical image software,and three-dimensional model of the central airway was constructed.The three-dimensional model was trimmed using Geomagic Studio 12 software.After meshing model by Ansys fluent 19.2 software meshing module,which was imported into Ansys 19.2 software for CFD simulation calculation.The simulations were conducted with the same tidal volume,and the variations of airflow within central airway were dynamically analyzed.Results The CFD was used for numerical simulation on three-dimensional model of central airway constructed based on CT image data.The results showed that the inlet velocity of the airflow was 2.15-4.44 m/s at the same tidal volume.The flow rate of airway gradually decreased from the inlet to the outlet,and the high flow rate area was formed.The maximum flow velocity was 3.25-6.77 m/s,the maximum flow velocity was closed to trachea wall,and airway wall pressure gradually decreased from trachea to bronchus.The absolute value of wall pressure in the area with higher flow velocity was higher.The maximum shear stress of airway wall was 0.888-2.240 Pa,in which the shear stress of airway wall,trachea bifurcation and secondary and tertiary bronchus was relatively large,and increased with the diameter decrease of trachea and bronchus.Conclusion It is demonstrated that the flow velocity,wall pressure and wall shear stress of airway are closely related to airway structure,which shows a certain overall spatial distribution and local characteristics by using CFD simulation of central airway model for healthy adults.