本文選題：上呼吸道 + 氣流運動�。� 參考：《中國人民解放軍軍事醫(yī)學科學院》2008年博士論文

【摘要】： 空氣污染物氣溶膠對人類健康產生嚴重的威脅,人體通過呼吸道吸入有毒氣溶膠會引發(fā)哮喘、肺氣腫和支氣管炎等呼吸道疾病,SARS和禽流感等疾病的爆發(fā)同樣是病毒以生物氣溶膠的形式通過呼吸道傳播而引發(fā)感染;針對各種呼吸道疾病,氣溶膠吸入治療在呼吸道疾病的防治中表現出了明顯的優(yōu)勢。人體上呼吸道內氣流流場、氣溶膠性質、呼吸模式及其幾何特性決定了有毒氣溶膠或吸入藥物氣溶膠的沉積位置和局部濃度,進而決定有毒氣溶膠的危害程度或藥物氣溶膠的治療效果。因此,研究人體呼吸道內的氣流運動特性,探討有毒氣溶膠或藥物氣溶膠在人體呼吸道內的沉積規(guī)律,對于認識有毒氣溶膠對人體的危害、進行劑量健康效應的評價以及繼續(xù)深入探索有毒氣溶膠的致病機理具有重要的實際意義,對于提高藥物氣溶膠的治療效果具有重要的指導意義。 本文在總結國內外研究工作的基礎上,借鑒ARLA(Aerosol Research Laboratory of Alberta)的理想口-喉模型和Weible模型的氣管-支氣管模型,建立了具有口腔-咽-喉-氣管-前三級支氣管的完整的人體上呼吸道模型。運用CFD數值仿真和試驗研究相結合的方法對人體上呼吸道內的氣流運動特性和氣溶膠運動沉積規(guī)律進行了全面、系統(tǒng)的研究。研究結果表明: 穩(wěn)態(tài)呼吸模式下,氣流在咽部外壁、氣管外壁發(fā)生分離現象,氣流在氣管內壁形成局部高速區(qū)域,容易造成較多的氣溶膠沉積;在氣管內的三個截面內分別形成兩個對稱的二次渦流運動,二次渦流運動使得氣管內壁所受到的流動剪應力增大,而外壁面剪應力減小;同時軸向速度在氣管內壁引起高剪應力分布,而外壁的剪應力較小,二次渦流容易造成氣溶膠在氣管內壁沉積較多;進入到支氣管內的氣流在分叉處發(fā)生分離,并且在下游支氣管的內壁區(qū)域形成新的邊界層,靠近支氣管內壁速度較高,并且在支氣管邊界層的外緣速度達到最大值,靠近支氣管外壁速度較低。 循環(huán)吸氣模式下,吸氣加速階段咽部、喉部和聲門下游氣管內壁形成局部高速區(qū),容易造成氣溶膠因慣性碰撞而沉積;在咽部外壁、聲門下游氣管上部外壁氣流逐漸發(fā)生分離,形成分離區(qū),使得氣溶膠在這些部位隨氣流環(huán)流循環(huán)運動,滯留時間增加,容易造成一部分氣溶膠在咽部外壁和氣管外壁的沉積;支氣管平面內形成拋物線型的速度分布,氣流主流逐漸偏離支氣管外壁,流向內壁,容易造成氣溶膠在支氣管內壁沉積較多;支氣管內各個截面上形成的二次渦流運動的強度逐漸增強,二次渦流運動會造成氣溶膠在內壁的沉積幾率增加。吸氣減速階段,咽部外壁的分離區(qū)逐漸向內壁方向擴大,同時在咽部的內壁也發(fā)生氣流分離現象,氣管外壁的分離區(qū)向氣管內壁方向擴大,同時向氣管下游延伸;在第一級支氣管外壁區(qū)產生氣流分離現象,形成較小的分離區(qū),在第二級和第三級支氣管內沒有發(fā)生類似現象。 循環(huán)呼氣模式下,呼氣加速階段與吸氣加速階段不同,氣管平面內氣流流速分布比較均勻;氣管內逐漸形成四個二次渦流運動,氣流在支氣管內經過多級分支的效果是使速度分布均勻化,特別是在同級兩個支氣管軸線共處的平面內的速度分布在經過幾級匯合后,軸線處的峰值分布現象會消失而變得均勻;在支氣管內呈現典型的拋物線速度分布形式,支氣管內的二次氣流運動經歷了從兩個渦流到四個渦流的運動變化過程。呼氣減速階段,呼氣終了時刻,在第一級和第二級支氣管的內壁均出現了氣流分離現象,在內壁形成分離區(qū)。 循環(huán)呼吸模式下,咽部、喉部、氣管以及支氣管內高軸向速度區(qū)和二次渦流運動均是在呼吸過程中逐漸出現的,只是間歇性地產生,所以由此而引起的氣道壁面的氣流剪應力集中,形成的高剪應力區(qū)也是間歇性的,只在整個周期的部分時間出現。壁面受到的剪應力周期性地改變方向,引起壁面勞損和組織損傷的可能性增大,同時在這些部位容易造成氣溶膠的沉積,還可能會引起各種呼吸道疾病。呼氣階段支氣管內的氣流運動、氣流剪應力的分布和氣溶膠的運動形式比吸氣階段更為復雜。 采用激光快速成型技術(Stereo-Lithography,SL)制作了人體上呼吸道的試驗模型,應用粒子圖像速度儀(Particle Image Velocimetry,PIV)對人體上呼吸道內的穩(wěn)態(tài)氣流運動特性進行了試驗研究,分析了在低強度呼吸條件下人體上呼吸道內的氣流運動特性。研究結果表明,數值仿真結果與試驗測量結果基本一致,證明了數值仿真方法的準確性和合理性。 利用拉格朗日方法對氣溶膠在上呼吸道內的運動進行仿真計算,分析了不同呼吸模式下氣溶膠的沉積特點。慣性碰撞對于微尺度氣溶膠沉積而言是主要的沉積機制,慣性參數是衡量碰撞作用造成顆粒沉積的一個重要的參數,人體上呼吸道內不同部位氣溶膠沉積率隨慣性參數的增加而增加;而湍流擴散、二次氣流運動和環(huán)流氣流運動對氣溶膠在人體上呼吸道內的沉積同樣具有重要的影響,人體的呼吸流量和氣溶膠性質對氣溶膠在上呼吸道內的沉積模式影響較小;慣性碰撞和湍流擴散的影響致使在喉部氣溶膠沉積最多,氣管中氣溶膠的沉積效率要高于支氣管中的氣溶膠沉積效率。人體循環(huán)吸氣模式下,氣溶膠在人體上呼吸道內的沉積率要高于穩(wěn)態(tài)吸氣情況下的氣溶膠的沉積率;循環(huán)吸氣模式下的氣溶膠沉積率遠大于循環(huán)呼氣模式下的氣溶膠沉積率。 建立了氣溶膠在人體上呼吸道內沉積的試驗臺,對氣溶膠在上呼吸道內的沉積進行了試驗研究。數值仿真結果與試驗結果基本一致,平均誤差為11%,沉積變化趨勢吻合較好。人體上呼吸道內氣溶膠沉積的數值仿真方法,能夠較好地預測氣溶膠在上呼吸道內的沉積模式以及不同部位的沉積率,是我們獲得上呼吸道內有毒氣溶膠或藥物氣溶膠在不同部位沉積信息的一種有效的方法。
[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.
【學位授予單位】：中國人民解放軍軍事醫(yī)學科學院
【學位級別】：博士
【學位授予年份】：2008
【分類號】：R363

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