PDF(Pubmed)
Abstract：
UNASSIGNED: 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, particle propagation depth, particle residence times, 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.
UNASSIGNED: The present study employs a realistic human breathing profile of 4.75s for one complete breathing cycle 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. Airflow patterns in the surfactant-enriched model support previous findings that the recirculation of the flow is affected by its propagation depth. 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, with values increasing to 25 mN/m at the inhalation and decreasing to 1 mN/m at the end of the exhalation. In the surfactant-deficient model, only water coats the alveolar walls with a high surface tension value of 70 mN/m.
UNASSIGNED: 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 magnitudes (100% increase at the end of exhalation) and higher velocity magnitudes (8.69% increase during inhalation and 11.9% increase during exhalation). In addition, high air-water surface tension in the surfactant-deficient case was found to induce higher shear stress values (by around a factor of 10) on the alveolar walls than that of the surfactant-enriched case.
UNASSIGNED: Overall, it was concluded that the presence of the surfactant improves respiratory mechanics and allows for smooth breathing and normal respiration.
UNASSIGNED: The present study employs a realistic human breathing profile of 4.75s for one complete breathing cycle 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. Airflow patterns in the surfactant-enriched model support previous findings that the recirculation of the flow is affected by its propagation depth. 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, with values increasing to 25 mN/m at the inhalation and decreasing to 1 mN/m at the end of the exhalation. In the surfactant-deficient model, only water coats the alveolar walls with a high surface tension value of 70 mN/m.
UNASSIGNED: 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 magnitudes (100% increase at the end of exhalation) and higher velocity magnitudes (8.69% increase during inhalation and 11.9% increase during exhalation). In addition, high air-water surface tension in the surfactant-deficient case was found to induce higher shear stress values (by around a factor of 10) on the alveolar walls than that of the surfactant-enriched case.
UNASSIGNED: Overall, it was concluded that the presence of the surfactant improves respiratory mechanics and allows for smooth breathing and normal respiration.
摘要：
未经评估：计算流体动力学（CFD）模拟，体外设置，在过去的几年中，实验离体方法已应用于许多肺泡几何形状。他们旨在研究和检查气流模式，粒子传输，粒子传播深度,颗粒停留时间,和颗粒-肺泡壁沉积部分。这些研究对于药物和毒理学研究都是必不可少的，特别是如今，随着来势凶猛的COVID-19病毒的升级。然而,这些研究中的大多数都忽略了覆盖肺泡的表面活性剂层以及空气-表面活性剂表面张力对流动动力学和空气-肺泡表面力学的影响。
UNASSIGNED：本研究在一个完整的呼吸周期中采用了4.75s的真实人类呼吸曲线，以通过数值比较富含表面活性剂和表面活性剂之间的气流现象来强调表面活性剂层的重要性。缺乏模型。腺泡模型表现出生理上准确的肺泡和导管尺寸，从肺代18到23。富含表面活性剂的模型中的气流模式支持先前的发现，即气流的再循环受其传播深度的影响。近端肺代经历主要的再循环流，而远端肺泡区域的更多代则表现出主要的径向流。在富含表面活性剂的模型中，表面张力值在吸气和呼气期间交替变化，值在吸入时增加到25mN/m，在呼气结束时减少到1mN/m。在缺乏表面活性剂的模型中，只有水以70mN/m的高表面张力值覆盖肺泡壁。
UNASSIGNED：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，并通过产生涡度而产生不稳定的混沌呼吸，伴随着更高的涡度大小（呼气结束时增加100％）和更高的速度大小（吸气时增加8.69％，呼气时增加11.9％）。此外,发现在缺乏表面活性剂的情况下，较高的空气-水表面张力会在肺泡壁上引起比富含表面活性剂的情况更高的剪切应力值（约为10倍）。
未经评估：总的来说，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。
UNASSIGNED：本研究在一个完整的呼吸周期中采用了4.75s的真实人类呼吸曲线，以通过数值比较富含表面活性剂和表面活性剂之间的气流现象来强调表面活性剂层的重要性。缺乏模型。腺泡模型表现出生理上准确的肺泡和导管尺寸，从肺代18到23。富含表面活性剂的模型中的气流模式支持先前的发现，即气流的再循环受其传播深度的影响。近端肺代经历主要的再循环流，而远端肺泡区域的更多代则表现出主要的径向流。在富含表面活性剂的模型中，表面张力值在吸气和呼气期间交替变化，值在吸入时增加到25mN/m，在呼气结束时减少到1mN/m。在缺乏表面活性剂的模型中，只有水以70mN/m的高表面张力值覆盖肺泡壁。
UNASSIGNED：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，并通过产生涡度而产生不稳定的混沌呼吸，伴随着更高的涡度大小（呼气结束时增加100％）和更高的速度大小（吸气时增加8.69％，呼气时增加11.9％）。此外,发现在缺乏表面活性剂的情况下，较高的空气-水表面张力会在肺泡壁上引起比富含表面活性剂的情况更高的剪切应力值（约为10倍）。
未经评估：总的来说，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。
