表面张力对人肺腺泡区血流动力学和肺泡力学的影响
Surface tension effects on flow dynamics and alveolar mechanics in the acinar region of human lung
摘要：
在过去的几年中，计算流体动力学（CFD）模拟、体外设置和实验性离体方法已被应用于许多肺泡几何形状。他们的目的是研究和检查气流模式，颗粒运输和颗粒肺泡壁沉积分数。这些研究对于制药和毒理学研究都是必不可少的，尤其是在当今威胁性的COVID-19病毒不断升级的情况下。然而，大多数这些研究忽略了表面活性剂层，覆盖肺泡和空气表面活性剂的表面张力对流动动力学和空气肺泡表面力学的影响。本研究采用了一个现实的人类呼吸轮廓4.75，强调表面活性剂层的重要性，通过数值比较的气流现象之间的表面活性剂丰富和表面活性剂缺乏的模型。腺泡模型表现出生理上准确的肺泡和导管尺寸从肺代18延伸到23。近端肺代经历占主导地位的再循环流，而远端肺泡区域的更远代表现出占主导地位的径向流。在表面张力富集模型中，表面张力值在吸气和呼气期间交替变化。在表面活性剂缺乏的模型中，只有水覆盖肺泡壁。结果表明，肺泡中的表面活性剂缺乏会不利地改变气流行为，并通过产生涡流产生不稳定的混沌呼吸，伴随着更高的涡度和速度幅度。此外，高空气-水表面张力在表面活性剂缺乏的情况下，被发现诱导较高的剪切应力值比表面活性剂丰富的情况下的肺泡壁。总之，得出的结论是，表面活性剂的存在改善了呼吸力学，并允许平稳呼吸和正常呼吸。
英文摘要：
Computational fluid dynamics (CFD) simulations, in-vitro setups, and experimental ex-vivo approaches have been applied to numerous alveolar geometries over the past years. They aimed to study and examine airflow patterns, particle transport, and particle-alveolar wall deposition fractions. These studies are imperative to both pharmaceutical and toxicological studies, especially nowadays with the escalation of the menacing COVID-19 virus. However, most of these studies ignored the surfactant layer that covers the alveoli and the effect of the air-surfactant surface tension on flow dynamics and air-alveolar surface mechanics. The present study employs a realistic human breathing profile of 4.75 to emphasize the importance of the surfactant layer by numerically comparing airflow phenomena between a surfactant-enriched and surfactant-deficient model. The acinar model exhibits physiologically accurate alveolar and duct dimensions extending from lung generations 18 to 23. Proximal lung generations experience dominant recirculating flow while farther generations in the distal alveolar region exhibit dominant radial flows. In the surfactant-enriched model, surface tension values alternate during inhalation and exhalation. In the surfactant-deficient model, only water coats the alveolar walls. Results showed that surfactant deficiency in the alveoli adversely alters airflow behavior and generates unsteady chaotic breathing through the production of vorticities, accompanied by higher vorticity and velocity magnitudes. In addition, high air-water surface tension in the surfactant-deficient case was found to induce higher shear stress values on the alveolar walls than that of the surfactant-enriched case. Overall, it was concluded that the presence of the surfactant improves respiratory mechanics and allows for smooth breathing and normal respiration.
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