Group of Structural Mechanics and Materials Modeling, Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna 3, 50018 Zaragoza, Spain.
Ann Biomed Eng. 2010 Apr;38(4):1556-65. doi: 10.1007/s10439-010-9951-3. Epub 2010 Feb 9.
The main physiological function of coughing is to remove from the airways the mucus and foreign particles that enter the lungs with respirable air. However, in patients with endotracheal tubes, further surgery has to be performed to improve cough effectiveness. Thus, it is necessary to analyze how this process is carried out in healthy tracheas to suggest ways to improve its efficacy in operated patients. A finite element model of a human trachea is developed and used to analyze the deformability of the tracheal walls under coughing. The geometry of the trachea is obtained from CT of a 70-year-old male patient. A fluid structure interaction approach is used to analyze the deformation of the wall when the fluid (in this case, air) flows inside the trachea. A structured hexahedral-based grid for the tracheal walls and an unstructured tetrahedral-based mesh with coincident nodes for the fluid are used to perform the simulations with the finite element-based commercial software code (ADINA R&D Inc.). Tracheal wall is modeled as an anisotropic fiber reinforced hyperelastic solid material in which the different orientation of the fibers is introduced. The implantation of an endotracheal prosthesis is simulated. Boundary conditions for breathing and coughing are applied at the inlet and at the outlet surfaces of the fluid mesh. The collapsibility of a human trachea under breathing and coughing is shown in terms of flow patterns and wall stresses. The ability of the model to reproduce the normal breathing and coughing is proved by comparing the deformed shape of the trachea with experimental results. Moreover the implantation of an endotracheal prosthesis would be related with a decrease of coughing efficiency, as clinically seen.
咳嗽的主要生理功能是清除随可吸入空气进入肺部的黏液和外来颗粒。然而，对于接受气管内管的患者，需要进一步的手术来提高咳嗽的效果。因此，有必要分析健康气管中这一过程是如何进行的，以便为提高手术患者的疗效提供建议。建立了一个人类气管的有限元模型，用于分析咳嗽时气管壁的可变形性。气管的几何形状是从一位 70 岁男性患者的 CT 中获得的。采用流固耦合方法来分析当气管内的流体（在这种情况下是空气）流动时壁的变形。使用基于结构六面体的网格来对气管壁进行模拟，同时使用具有重合节点的非结构四面体网格来对流体进行模拟，这些模拟是使用基于有限元的商业软件（ADINA R&D Inc.）完成的。气管壁被建模为各向异性纤维增强超弹性固体材料，其中引入了纤维的不同取向。模拟了气管内假体的植入。在流体网格的入口和出口表面施加呼吸和咳嗽的边界条件。以流动模式和壁面应力的形式显示了人类气管在呼吸和咳嗽下的塌陷能力。通过将气管的变形形状与实验结果进行比较，证明了模型再现正常呼吸和咳嗽的能力。此外，正如临床上所见，气管内假体的植入与咳嗽效率的降低有关。
