基于分叉管路的对称特征模拟肺内物质输运

发布时间：2018-03-25 15:26

本文选题：全肺　切入点：屏气呼吸　出处：《西安建筑科技大学》2017年硕士论文

【摘要】：研究呼吸过程肺部颗粒物的沉积及气体传输特性对于评估人体健康至关重要。例如,发生火灾时,人处于高浓度烟气环境中,有毒有害烟气随呼吸进入人体呼吸道,当有害物质到达人体呼吸功能的肺腺泡区,可穿过气血屏障进入血液,严重危害人体健康。有毒有害烟气进入肺部的深度和浓度,直接影响人在火灾中的存活时间。另一方面,吸入疗法是利用药物颗粒在肺内病变区域沉积的一种新型治疗呼吸系统疾病的方法,由于它的高生物利用度和高效率的优点,近年来被认为是一种很有前途的治疗方式。本文基于多级分叉特征的健康成年人肺部模型,通过对模型的合理简化及边界条件的改进,改善了数值模拟的效率,研究在不同的呼吸状态,如平静呼吸、高频呼吸、深呼吸以及屏气呼吸状况下肺内颗粒沉积及气体传输特性。本文数值模拟采用多物理场耦合软件COMSOL Multiphysics4.3a。首先,利用本课题前人建立的二维八级肺腺泡模型,研究了屏气状况下重力方向对肺腺泡内颗粒沉积特性的影响,竖直重力方向和水平重力方向分别代表人处于竖直站立和平躺两个状态。研究表明:不同的重力方向对肺腺泡内的整体沉积率基本没有影响,但对分级沉积率有影响,相对于人站立时的竖直重力方向,人在平躺状况下能增加特定区域的分级沉积率。其次,基于Weibel-A肺部模型,通过对称简化原则建立二维4-23级健康成年人全肺模型,研究了全肺内不同呼吸方式对气体传输的影响。研究表明:气体在肺部扩散非常快,在第一个吸气周期就能到达具有呼吸功能的肺腺泡区域;在循环呼吸状况下,通过高频呼吸、平静呼吸、深呼吸的对比发现,高频呼吸和平静呼吸传输速度相当,深呼吸扩散更快;通过循环呼吸和屏气呼吸的对比发现,屏气能减缓肺部气体传输,这一现象在平静呼吸时最明显;通过对比不同方式的屏气呼吸发现,平静屏气呼吸气体传输最慢,高频屏气呼吸次之,深屏气呼吸传输最快。最后,通过全肺模型引出了模拟多级分叉网络中粒子沉积计算量巨大的难点,基于此提出粒子加倍算法,改进对多级分叉网络中粒子传输和沉积特性的模拟。并且对所提出的粒子加倍算法进行了详细分析,首先对加倍前的原始粒子和加倍后产生的次级粒子的速度大小和运动轨迹进行分析,然后对粒子加倍算法计算分叉网络中颗粒沉积率进行研究,证明粒子加倍方法的可行性和有效性。本文所提出的粒子加倍算法,不仅可以简化全肺内颗粒沉积的数值模拟,而且可以运用到河流或者空调管路等多级分叉网络中的研究中。
[Abstract]:It is important to study the deposition and gas transport characteristics of pulmonary particulate matter in respiratory process. For example, when a fire occurs, a person is in a high concentration of smoke, and the toxic and harmful smoke enters the respiratory tract of the human body with breathing. When the harmful substance reaches the pulmonary acinar area of the human body's respiratory function, it can enter blood through the air and blood barrier and seriously endanger human health. The depth and concentration of toxic and harmful smoke entering the lungs directly affect the survival time of a person in a fire. On the other hand, Inhalation therapy is a new method for the treatment of respiratory diseases, which is deposited in the diseased area of the lung by using drug particles, because of its advantages of high bioavailability and high efficiency. In recent years, it has been considered as a promising treatment method. In this paper, the efficiency of numerical simulation is improved by reasonably simplifying the model and improving the boundary conditions. The characteristics of particle deposition and gas transport in lung under different breathing conditions, such as calm breathing, high frequency breathing, deep breathing and breath-holding, were studied. In this paper, the multi-physical field coupling software COMSOL Multiphysics4.3a was used to simulate the particle deposition and gas transport in the lung. In this paper, the influence of gravity direction on the deposition characteristics of pulmonary acinar particles under breath-holding condition was studied by using the 2-D eight grade pulmonary acinus model established by our predecessors. The direction of vertical gravity and the direction of horizontal gravity represent a person standing vertically and lying flat, respectively. The study shows that different directions of gravity have no effect on the overall deposition rate of pulmonary acinus, but have an effect on the deposition rate of different grades. Compared with the vertical gravity direction of standing, people can increase the graded deposition rate of specific areas in lying on their back. Secondly, based on the Weibel-A lung model, the 2-D 4-23 grade healthy adult whole lung model is established by the principle of symmetry simplification. The effects of different breathing patterns in the whole lung on gas transport were studied. The results show that the gas diffuses very quickly in the lung and reaches the pulmonary acinar region with respiratory function in the first inspiratory cycle, and in the condition of circulatory respiration, By comparing high-frequency breathing, calm breathing, and deep breathing, it was found that high-frequency breathing and calm breathing transmit at the same speed, and deep breathing diffuses faster; by comparing circulatory breathing with breath-holding, holding breath can slow down lung gas transmission. This phenomenon is most obvious when breathing peacefully. By comparing different breathing modes, it is found that the slow transfer of breath-holding gas is the slowest, followed by high-frequency breath-holding, and the fastest transmission of deep breath-holding. Through the whole lung model, the difficulty of particle deposition calculation in simulating multilevel bifurcation network is presented. Based on this, a particle doubling algorithm is proposed. The simulation of particle transport and deposition characteristics in multilevel bifurcation network is improved, and the particle doubling algorithm is analyzed in detail. The velocity and trajectory of the original particles before doubling and the secondary particles after doubling are analyzed, and then the particle doubling algorithm is studied to calculate the deposition rate of particles in the bifurcation network. It is proved that the particle doubling method is feasible and effective. The particle doubling algorithm presented in this paper not only simplifies the numerical simulation of particle deposition in the whole lung, but also can be applied to the study of multi-level bifurcation networks such as rivers or air conditioning pipes.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R56;TU83

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