【作者】 赖伟；

【导师】 裴觉民； 谭小苹；

【作者基本信息】 四川大学 ， 生物医学工程， 2003， 硕士

【摘要】 随着人们生存的外界环境的变化，如大气、水源、食品污染，人口密度剧增，以及高节奏大压力的生活方式，呼吸系统疾病已经成为危害我国人民健康的常见疾病，因而对呼吸系统疾病的研究显得十分重要及迫切。目前从生物学与临床医学角度已进行了大量工作，如从氧自由基、DNA角度研究肺病变时的分子生物学变化，通过各种显微镜进行微观形态学观察，并通过动物实验和临床观察，得到疾病的各种表观特征，指导医生进行治疗。虽然上述研究以及气体分析、医学影像技术等新技术新设备对医生诊治有很大帮助，但是仅仅通过上述手段是不够的，由于呼吸系统，特别是支气管树的特殊构造，无法定量检测出支气管树内不同部位的气体流动状况和压力分布，只能依靠其他方法间接测到肺内压和主气道压力，这对疾病的诊治不利，因此有必要从物理的力学的角度，研究呼吸时肺支气管树内的气体流动问题。 国内外学者在呼吸力学问题的研究中，通过物理实验和数学模型模拟方法，研究气管内气体流动、肺部气体交换、呼吸道的压力降以及肺的机械通气等问题，并取得了不少成果。但在肺通气阻力问题方面，这些数学模型将呼吸系统简化为几个部分，对其做整体研究，缺乏对支气管树局部的考虑，没有体现出支气管树内不同位置气体流动的差异。 本文从整体和局部两个方面研究支气管树内的气体的分布与流动情况。在整体方面利用流体网络理论，建立支气管树在前五至七级为非对称分叉，后面的分级为对称分叉结构的三参数集中参数模型，利用Gear算法求解常微分方程组，得到正常呼吸过程中气体在肺支气管树内不同分段的压力和流量分布，较好体现了气体在肺支气管树前几级的分配和压力变化。并在此基础上探讨了支四川大学硕士学位论文气管局部受阻时，肺支气管树内不同部位所受到的影响及压力和流量的变化，并进行了比较;在局部方面，利用计算流体力学的基本理论和通用计算流体力学软件，对支气管树一级分叉部位的气体流动进行了二维和三维模型的数值模拟和分析。得到气管内的气体在一个呼吸周期非定常条件下的流动变化，模拟结果与实验观察相吻合。并与定常条件下的计算结果进行了比较。 本文所做的工作对认识肺支气管树在生理、病理状态下的气流分布很有意义，对进一步研究气道阻力、气道病变受阻的气体流动状况等的理论研究和临床应用具有较大帮助。更多还原

【Abstract】 Respiratory diseases have become very common ailments threatening people’s health and lives with environmental deteriorating. Many factors, such as atmospheric pollution, water pollution, food pollution, population density leaping and high-pressured life style, etc. could be counted as the causes. Currently, variety of researches in biological and medical fields is being carried out. For instance, investigations into the changes of molecular biology in pathological changes of the lungs from the angle of oxygen-derived free radicals and DNA, the observation of micro- configuration using various microscopes, investigation of the apparent characteristics of diseases through animal test and clinic diagnosis, etc. have proved helpful approaches. Although more and more newly-developed techniques and equipment mentioned above have come into use in clinic diagnosis and therapies, many problems are kept unsolved in the research of the lungs. Pressure distribution and airflow status in the bronchial tree cannot be measured directly and exactly due to the complex and fragile structure of the bronchial tree, with only the pressure in the trachea and lungs being measured indirectly in other ways. This is an obstacle to the diagnosis and cure of the lung diseases. So physical and mechanical modeling is but a feasible method to explore the airflow and pressure distribution in bronchial tree during respiration.Many a mathematical model about investigation into airflow in the trachea, gas exchange in the lungs, pressure drop in the bronchial passages, and lung ventilationhave been set up and some useful results have been obtained. However, in view of the resistance of pulmonary ventilation, these mathematical models simplified respiratory system into several parts in order to make a overall study, so that they are lack of considering localities of the bronchial tree and do not give the differences of airflow between various locations.The air distribution and airflow status in the bronchial tree has been dealt with in the present thesis in two different ways - local and overall. Based on the theory of fluid network, a three-element lumped parameter model of bronchial tree was proposed in the overall treatment. It was assumed that the upper five or seven generations of the twenty-four generations of the respiratory airway are asymmetric, while the rest are symmetric. The Gear method was applied to solve the ordinary differential equations of the mathematical model. The pressure and flow rate distributions in different positions of the lungs have been computed, and fairly reasonable pressure change and air distribution along the upper generations of bronchial tree have been obtained. In addition, the effects of partial bronchial obstruction on the change of pressure and flow at different locations in the bronchial tree were compared to the results under the normal physiological conditions. Based on the basic theory and software of computational fluid mechanics, two dimensional and three dimensional flows at the bifurcation area of the first generation were modeled and solved mathematically in the local treatment. The results of the change of flow during a single respiratory period were matched with the observance of experiment by other authors. The results were also compared to those in steady conditions.The results of this research may lead to meaningful understanding of the distribution of airflow along the bronchial tree under physiological and pathological conditions and may offer a helpful basis for the further study in the theoretical and clinical research of the resistance and the airflow along normal and blocked respiratory airways.更多还原