肺腺泡内颗粒物的沉积及阻塞影响的数值模拟研究
发布时间：2018-07-14 12:23
【摘要】：近年来,随着经济发展带来的空气污染日益严重,由此引起的各类呼吸系统疾病和发病率和死亡率随之上升。大气中的可吸入颗粒物尤其是PM2.5(可入肺颗粒物)被吸入后,在人体呼吸系统的肺腺泡区沉积,甚至会进入人体的血液循环系统,对人体的健康造成危害。儿童的呼吸系统还处于发育阶段,自身的抵抗力较差,对大气中的可吸入颗粒物更加敏感。因此,研究成人和儿童肺腺泡区的气流特性以及可吸入颗粒物的沉积,对理解气体和颗粒物的输运机理,评价可入肺颗粒物对不同年龄人群的影响具有重要意义,将有助于肺部物质输运及相关领域的深入研究。并且,研究药物颗粒在肺腺泡病变部位的沉积,可以评价药物的靶向作用,为进一步改善和优化药物靶向治疗提供可靠的理论基础。由于人体肺腺泡部位的真实生理结构尺度小、肺泡数量多、结构复杂,目前仅有组织学上的平面切片图形。实验中一般利用相似原则建模,开展大尺度下的流动显示与颗粒沉积实验。与之相比,数值模拟方法则不受实验手段的制约,能够揭示流动中的细节。本文基于Weibel-A模型数据的基础,通过假设简化建立三维0~8级正常肺腺泡模型和二维阻塞肺腺泡模型,并通过引入动壁面边界条件反映肺部节律收缩/扩张的动力学机制,采用数值模拟手段研究成人与儿童肺腺泡气流与颗粒的沉积特性,肺腺泡的阻塞产生的影响,以及药物颗粒在阻塞部位的靶向作用。本文数值模拟采用多物理场耦合软件COMSOL Multiphysics 4.3a,分别采用欧拉法和拉格朗日法对肺腺泡区气流流动和颗粒运动进行研究。正常肺腺泡的模拟结果表明:随着肺腺泡级数的增加,气流速度逐渐减小,压力值逐渐增大,颗粒物的分级沉积率逐渐增大;模型的三维结构是肺腺泡流动特性的研究中不可忽视的问题,颗粒的沉积率整体高于二维模型;与固定肺泡壁条件相比,动肺泡壁条件可以增强肺泡内流场的对流流动,使颗粒沉积率增大;不同呼吸状态下,颗粒的沉积有所不同,主要受呼吸时间的影响;年龄越小的个体,肺腺泡各级的气流速度和压力值相对越大,颗粒的沉积率也越大。阻塞肺腺泡的模拟结果表明:阻塞主要影响阻塞处的上下游流速,以及和阻塞处具有相同上级的另一侧流速;阻塞处附近压降较大,且距离肺腺泡终端越远的区域发生阻塞,其压降值越大;管段的阻塞对有相同上级的正常一侧区域的颗粒沉积几乎没有影响;阻塞主要影响阻塞处下一分叉处的颗粒沉积;概括性地找出药物的最佳靶向粒径不太可能,药物的靶向性和阻塞发生的部位以及阻塞处的数量等复杂因素有关。
[Abstract]:In recent years, air pollution caused by economic development is becoming more and more serious. After inhalable particulate matter (PM2.5) in the atmosphere is inhaled, it deposits in the pulmonary acinar area of the human respiratory system, and even enters the human blood circulatory system, which is harmful to human health. The respiratory system of children is still in the developmental stage, their own resistance is poor, and they are more sensitive to respirable particles in the atmosphere. Therefore, it is of great significance to study the airflow characteristics of pulmonary acinar area and the deposition of inhalable particles in adults and children, in order to understand the transport mechanism of gas and particulate matter, and to evaluate the effect of particulate matter on people of different ages. It will be helpful for the further study of lung transport and related fields. Furthermore, the study of the deposition of drug particles in the lesion of pulmonary acinus can evaluate the targeting effect of drugs and provide a reliable theoretical basis for further improvement and optimization of drug targeting therapy. Due to the small size of the real structure of the human pulmonary acinar, the large number of alveoli and the complex structure, there are only histologically planar slices. In the experiments, the principle of similarity is generally used to model the flow display and particle deposition in large scale. In contrast, the numerical simulation method is not restricted by experimental means and can reveal the details of the flow. On the basis of Weibel-A model data, a 3-dimensional normal pulmonary acinar model of grade 8 and a two-dimensional model of obstructive pulmonary acinus were established by hypothetical simplification, and the dynamic mechanism of pulmonary rhythm contraction / dilation was reflected by introducing the moving wall boundary condition. The characteristics of airflow and particle deposition of pulmonary acinar in adults and children, the effects of pulmonary acinar obstruction and the targeting effect of drug particles on the blocking site were studied by numerical simulation. In this paper, the multi-physical field coupling software COMSOL Multiphysics 4.3a is used to simulate the airflow and particle motion in the pulmonary acinar region by Euler method and Lagrangian method, respectively. The simulation results of normal pulmonary acinar show that with the increase of pulmonary acinar progression, the airflow velocity decreases gradually, the pressure value increases, and the graded deposition rate of particulate matter increases. The three-dimensional structure of the model can not be ignored in the study of the characteristics of pulmonary acinar flow, the deposition rate of particles is higher than that of the two-dimensional model, compared with the fixed alveolar wall condition, the dynamic alveolar wall condition can enhance the convective flow in the alveolar flow field. The deposition rate of particles is different in different breathing states, which is mainly affected by respiration time. The younger the age is, the greater the airflow velocity and pressure at all levels of pulmonary acinus are, and the higher the deposition rate of particles is. The simulation results of obstructive pulmonary acinar show that blockage mainly affects the upstream and downstream velocity of the blockage and the flow velocity on the other side with the same superior level as the obstruction place, and the pressure drop near the obstruction place is larger, and the area farther away from the pulmonary acinar terminal is blocked. The greater the pressure drop value, the less likely the blockage of the tube segment has any effect on the particle deposition in the normal side of the area with the same upper level; the blockage mainly affects the particle deposition at the next branch of the blockage; and it is unlikely that the optimal target particle size of the drug will be found. Drug targeting is related to complex factors such as the location and number of blockages occurring.
【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】：2016
【分类号】：R56;X51
，
本文编号：2121634
[Abstract]:In recent years, air pollution caused by economic development is becoming more and more serious. After inhalable particulate matter (PM2.5) in the atmosphere is inhaled, it deposits in the pulmonary acinar area of the human respiratory system, and even enters the human blood circulatory system, which is harmful to human health. The respiratory system of children is still in the developmental stage, their own resistance is poor, and they are more sensitive to respirable particles in the atmosphere. Therefore, it is of great significance to study the airflow characteristics of pulmonary acinar area and the deposition of inhalable particles in adults and children, in order to understand the transport mechanism of gas and particulate matter, and to evaluate the effect of particulate matter on people of different ages. It will be helpful for the further study of lung transport and related fields. Furthermore, the study of the deposition of drug particles in the lesion of pulmonary acinus can evaluate the targeting effect of drugs and provide a reliable theoretical basis for further improvement and optimization of drug targeting therapy. Due to the small size of the real structure of the human pulmonary acinar, the large number of alveoli and the complex structure, there are only histologically planar slices. In the experiments, the principle of similarity is generally used to model the flow display and particle deposition in large scale. In contrast, the numerical simulation method is not restricted by experimental means and can reveal the details of the flow. On the basis of Weibel-A model data, a 3-dimensional normal pulmonary acinar model of grade 8 and a two-dimensional model of obstructive pulmonary acinus were established by hypothetical simplification, and the dynamic mechanism of pulmonary rhythm contraction / dilation was reflected by introducing the moving wall boundary condition. The characteristics of airflow and particle deposition of pulmonary acinar in adults and children, the effects of pulmonary acinar obstruction and the targeting effect of drug particles on the blocking site were studied by numerical simulation. In this paper, the multi-physical field coupling software COMSOL Multiphysics 4.3a is used to simulate the airflow and particle motion in the pulmonary acinar region by Euler method and Lagrangian method, respectively. The simulation results of normal pulmonary acinar show that with the increase of pulmonary acinar progression, the airflow velocity decreases gradually, the pressure value increases, and the graded deposition rate of particulate matter increases. The three-dimensional structure of the model can not be ignored in the study of the characteristics of pulmonary acinar flow, the deposition rate of particles is higher than that of the two-dimensional model, compared with the fixed alveolar wall condition, the dynamic alveolar wall condition can enhance the convective flow in the alveolar flow field. The deposition rate of particles is different in different breathing states, which is mainly affected by respiration time. The younger the age is, the greater the airflow velocity and pressure at all levels of pulmonary acinus are, and the higher the deposition rate of particles is. The simulation results of obstructive pulmonary acinar show that blockage mainly affects the upstream and downstream velocity of the blockage and the flow velocity on the other side with the same superior level as the obstruction place, and the pressure drop near the obstruction place is larger, and the area farther away from the pulmonary acinar terminal is blocked. The greater the pressure drop value, the less likely the blockage of the tube segment has any effect on the particle deposition in the normal side of the area with the same upper level; the blockage mainly affects the particle deposition at the next branch of the blockage; and it is unlikely that the optimal target particle size of the drug will be found. Drug targeting is related to complex factors such as the location and number of blockages occurring.
【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】：2016
【分类号】：R56;X51
，
本文编号：2121634
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