人体上呼吸道内气流运动特性与气溶胶沉积规律的研究

发布时间：2018-05-20 11:53

本文选题：上呼吸道 + 气流运动　；参考：《中国人民解放军军事医学科学院》2008年博士论文

【摘要】： 空气污染物气溶胶对人类健康产生严重的威胁,人体通过呼吸道吸入有毒气溶胶会引发哮喘、肺气肿和支气管炎等呼吸道疾病,SARS和禽流感等疾病的爆发同样是病毒以生物气溶胶的形式通过呼吸道传播而引发感染;针对各种呼吸道疾病,气溶胶吸入治疗在呼吸道疾病的防治中表现出了明显的优势。人体上呼吸道内气流流场、气溶胶性质、呼吸模式及其几何特性决定了有毒气溶胶或吸入药物气溶胶的沉积位置和局部浓度,进而决定有毒气溶胶的危害程度或药物气溶胶的治疗效果。因此,研究人体呼吸道内的气流运动特性,探讨有毒气溶胶或药物气溶胶在人体呼吸道内的沉积规律,对于认识有毒气溶胶对人体的危害、进行剂量健康效应的评价以及继续深入探索有毒气溶胶的致病机理具有重要的实际意义,对于提高药物气溶胶的治疗效果具有重要的指导意义。本文在总结国内外研究工作的基础上,借鉴ARLA(Aerosol Research Laboratory of Alberta)的理想口-喉模型和Weible模型的气管-支气管模型,建立了具有口腔-咽-喉-气管-前三级支气管的完整的人体上呼吸道模型。运用CFD数值仿真和试验研究相结合的方法对人体上呼吸道内的气流运动特性和气溶胶运动沉积规律进行了全面、系统的研究。研究结果表明: 稳态呼吸模式下,气流在咽部外壁、气管外壁发生分离现象,气流在气管内壁形成局部高速区域,容易造成较多的气溶胶沉积;在气管内的三个截面内分别形成两个对称的二次涡流运动,二次涡流运动使得气管内壁所受到的流动剪应力增大,而外壁面剪应力减小;同时轴向速度在气管内壁引起高剪应力分布,而外壁的剪应力较小,二次涡流容易造成气溶胶在气管内壁沉积较多;进入到支气管内的气流在分叉处发生分离,并且在下游支气管的内壁区域形成新的边界层,靠近支气管内壁速度较高,并且在支气管边界层的外缘速度达到最大值,靠近支气管外壁速度较低。循环吸气模式下,吸气加速阶段咽部、喉部和声门下游气管内壁形成局部高速区,容易造成气溶胶因惯性碰撞而沉积;在咽部外壁、声门下游气管上部外壁气流逐渐发生分离,形成分离区,使得气溶胶在这些部位随气流环流循环运动,滞留时间增加,容易造成一部分气溶胶在咽部外壁和气管外壁的沉积;支气管平面内形成抛物线型的速度分布,气流主流逐渐偏离支气管外壁,流向内壁,容易造成气溶胶在支气管内壁沉积较多;支气管内各个截面上形成的二次涡流运动的强度逐渐增强,二次涡流运动会造成气溶胶在内壁的沉积几率增加。吸气减速阶段,咽部外壁的分离区逐渐向内壁方向扩大,同时在咽部的内壁也发生气流分离现象,气管外壁的分离区向气管内壁方向扩大,同时向气管下游延伸;在第一级支气管外壁区产生气流分离现象,形成较小的分离区,在第二级和第三级支气管内没有发生类似现象。循环呼气模式下,呼气加速阶段与吸气加速阶段不同,气管平面内气流流速分布比较均匀;气管内逐渐形成四个二次涡流运动,气流在支气管内经过多级分支的效果是使速度分布均匀化,特别是在同级两个支气管轴线共处的平面内的速度分布在经过几级汇合后,轴线处的峰值分布现象会消失而变得均匀;在支气管内呈现典型的抛物线速度分布形式,支气管内的二次气流运动经历了从两个涡流到四个涡流的运动变化过程。呼气减速阶段,呼气终了时刻,在第一级和第二级支气管的内壁均出现了气流分离现象,在内壁形成分离区。循环呼吸模式下,咽部、喉部、气管以及支气管内高轴向速度区和二次涡流运动均是在呼吸过程中逐渐出现的,只是间歇性地产生,所以由此而引起的气道壁面的气流剪应力集中,形成的高剪应力区也是间歇性的,只在整个周期的部分时间出现。壁面受到的剪应力周期性地改变方向,引起壁面劳损和组织损伤的可能性增大,同时在这些部位容易造成气溶胶的沉积,还可能会引起各种呼吸道疾病。呼气阶段支气管内的气流运动、气流剪应力的分布和气溶胶的运动形式比吸气阶段更为复杂。采用激光快速成型技术(Stereo-Lithography,SL)制作了人体上呼吸道的试验模型,应用粒子图像速度仪(Particle Image Velocimetry,PIV)对人体上呼吸道内的稳态气流运动特性进行了试验研究,分析了在低强度呼吸条件下人体上呼吸道内的气流运动特性。研究结果表明,数值仿真结果与试验测量结果基本一致,证明了数值仿真方法的准确性和合理性。利用拉格朗日方法对气溶胶在上呼吸道内的运动进行仿真计算,分析了不同呼吸模式下气溶胶的沉积特点。惯性碰撞对于微尺度气溶胶沉积而言是主要的沉积机制,惯性参数是衡量碰撞作用造成颗粒沉积的一个重要的参数,人体上呼吸道内不同部位气溶胶沉积率随惯性参数的增加而增加;而湍流扩散、二次气流运动和环流气流运动对气溶胶在人体上呼吸道内的沉积同样具有重要的影响,人体的呼吸流量和气溶胶性质对气溶胶在上呼吸道内的沉积模式影响较小;惯性碰撞和湍流扩散的影响致使在喉部气溶胶沉积最多,气管中气溶胶的沉积效率要高于支气管中的气溶胶沉积效率。人体循环吸气模式下,气溶胶在人体上呼吸道内的沉积率要高于稳态吸气情况下的气溶胶的沉积率;循环吸气模式下的气溶胶沉积率远大于循环呼气模式下的气溶胶沉积率。建立了气溶胶在人体上呼吸道内沉积的试验台,对气溶胶在上呼吸道内的沉积进行了试验研究。数值仿真结果与试验结果基本一致,平均误差为11%,沉积变化趋势吻合较好。人体上呼吸道内气溶胶沉积的数值仿真方法,能够较好地预测气溶胶在上呼吸道内的沉积模式以及不同部位的沉积率,是我们获得上呼吸道内有毒气溶胶或药物气溶胶在不同部位沉积信息的一种有效的方法。
[Abstract]:Air pollutant aerosols pose a serious threat to human health. Inhalation of aerosols through the respiratory tract causes respiratory diseases such as asthma, emphysema and bronchitis. The outbreak of SARS and avian influenza is the same as the infection of the virus in the form of biological aerosols through the breathing tract; for various respiratory diseases. Aerosol inhalation therapy has shown obvious advantages in the prevention and control of respiratory diseases. The flow field, aerosol properties, breathing patterns and geometric properties of the upper respiratory tract determine the location and local concentration of toxic aerosols or inhaled aerosol aerosols, and determine the degree of harm or drug gas solubility of the aerosol. Therefore, the characteristics of the air flow in the human respiratory tract are studied, and the depositional laws of toxic aerosol or drug aerosol in the human respiratory tract are discussed. It is important to recognize the harm of the toxic aerosol to the human body, to evaluate the health effect of the dose and to further explore the pathogenic mechanism of the toxic aerosol. The intertemporal significance has important guiding significance for improving the therapeutic effect of aerosol.
On the basis of the research work at home and abroad, the complete human upper respiratory tract model with oral pharynx larynx trachea and the first three bronchus is established using the ideal oral throat model of ARLA (Aerosol Research Laboratory of Alberta) and the tracheobronchial model of Weible model. The combination of CFD numerical simulation and experimental research is combined. The characteristics of the airflow and the rule of aerosol movement and deposition in the upper respiratory tract of the human body were studied comprehensively and systematically.
In the steady breathing mode, the air flow is separated from the outer wall of the pharynx and the outer wall of the trachea is separated. The air flow in the inner wall of the trachea is formed in a local high-speed region, which can easily cause more aerosol deposition, and two symmetrical two swirl motions are formed in the three sections of the trachea, and the flow shear stress on the inner wall of the trachea is caused by the two vortexes. In addition, the shear stress of the outer wall decreases, while the axial velocity causes the high shear stress distribution on the inner wall of the trachea, while the shear stress of the outer wall is smaller. The two swirl can easily cause more deposition of aerosols in the inner wall of the trachea, and the air flow into the bronchus is separated at the fork, and a new boundary layer is formed in the inner wall area of the downstream bronchi. The velocity near the inner wall of the bronchus is high, and the velocity at the outer edge of the bronchial boundary layer reaches the maximum, and the velocity near the bronchial outer wall is relatively low.
In the cycle suction mode, a local high-speed region is formed in the throat of the suction acceleration stage, the throat and the inner wall of the trachea at the lower reaches of the glottis, which can easily cause the aerosol to be deposited by the inertia collision, and the outer wall of the upper wall of the trachea in the lower throat of the pharynx gradually separates and forms a separation area, causing the aerosol to be detained in these parts with the circulation circulation of the air flow. When the time increases, a part of the aerosol is deposited in the outer wall of the pharynx and the outer wall of the trachea; the velocity distribution of the parabolic type is formed in the plane of the bronchus, and the mainstream of the air flow gradually deviates from the outer wall of the bronchus and flows into the inner wall. It is easy to cause more deposition of aerosols in the inner wall of the bronchus, and two swirl movements formed on each section of the trachea. The strength of the two swirl will increase the deposition probability of the aerosol on the inner wall. The separation area of the outer wall of the pharynx expands gradually to the inner wall, while the inner wall of the pharynx also occurs in the inner wall of the pharynx. The separation area of the outer wall of the trachea extends to the inner wall of the trachea and extends downstream of the trachea at the same time. There was a phenomenon of air separation in the outer wall of the bronchus, and a smaller separation area was formed. There was no similar phenomenon in grade second and grade third bronchi.
In the cycle expiration mode, the air flow velocity distribution in the trachea plane is more uniform in the exhaled exhalation stage than in the inhalation acceleration stage, and four two swirl motions are formed in the trachea, and the effect of the air flow through the multistage branch in the bronchus is to homogenization the velocity distribution, especially in the plane of the two bronchial axes cooperating at the same level. The peak distribution in the axis will disappear after the convergence of the degree distribution at several levels. The typical parabolic velocity distribution in the bronchus shows a typical parabolic velocity distribution in the bronchus. The two flow of air in the bronchus has undergone the movement from two swirl to four eddy current. The air separation phenomenon appeared in the inner wall of the two grade bronchus, and the separation area was formed in the inner wall.
In the cycle breathing mode, the throat, larynx, trachea, and the high axial velocity zone and two swirl movement in the bronchus are all gradually appearing during the breathing process, only intermittent real estate, so the air shear stress concentration of the airway wall is concentrated, and the high shear stress area is intermittent, only in the whole period. The shear stress periodically changes the direction of the wall and causes the increase in the possibility of wall strain and tissue damage. At the same time, it is easy to cause the deposition of aerosol and may cause various respiratory diseases. The airflow movement in the bronchus, the distribution of the air flow shear stress and the form ratio of the aerosol movement in the expiratory stage The inhalation stage is more complex.
The experimental model of the human upper respiratory tract was made by Stereo-Lithography (SL). The dynamic characteristics of the steady air flow in the upper respiratory tract were studied by the Particle Image Velocimetry (PIV), and the airflow in the upper respiratory tract under low intensity respiration was analyzed. The results show that the numerical simulation results are basically consistent with the experimental results, which proves the accuracy and rationality of the numerical simulation method.
The Lagrange method is used to simulate the motion of aerosols in the upper respiratory tract, and the characteristics of aerosol deposition in different breathing patterns are analyzed. Inertial collisions are the main deposition mechanism for microscale aerosol deposition. The inertial parameters are an important parameter to measure the particle deposition caused by collision, and the human body calls on the body. The aerosol deposition rate in the different parts of the suction channel increases with the increase of the inertial parameters, while the turbulent diffusion, the two air flow and the circulation flow have an important influence on the deposition of aerosols in the upper respiratory tract. The respiratory flow and aerosol properties of the human body have little influence on the deposition pattern of gas soluble glue in the upper respiratory tract. The effect of inertial and turbulent diffusion causes the most deposition in the larynx. The deposition efficiency of the aerosol in the trachea is higher than the aerosol deposition efficiency in the bronchus. The deposition rate of aerosols in the human body's upper respiratory tract is higher than that in the steady inhalation condition. The aerosol deposition rate is much larger than the aerosol deposition rate under cyclic expiratory mode.
An experimental platform for aerosol deposition in the upper respiratory tract was established, and the deposition of aerosols in the upper respiratory tract was experimentally studied. The numerical simulation results are basically consistent with the experimental results, the average error is 11%, and the trend of deposition changes well. The numerical simulation method of aerosol deposition in the upper respiratory tract can be well predicted. The deposition patterns of aerosols in the upper respiratory tract and the deposition rate in different parts of the upper respiratory tract are an effective method for obtaining the information of the aerosol or aerosol in the upper respiratory tract in different parts of the respiratory tract.
【学位授予单位】：中国人民解放军军事医学科学院
【学位级别】：博士
【学位授予年份】：2008
【分类号】：R363

【参考文献】