The Influence of Airway Tree Geometry and Ventilation Frequency on Airflow Distribution
The Influence of Airway Tree Geometry and Ventilation Frequency on Airflow Distribution
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DOI：
10.1115/1.4030621
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发表时间：
2015-08-01
影响因子：
1.7
通讯作者：
Bruecker, Christoph
中科院分区：
文献类型：
--
作者：
Bauer, Katrin;Bruecker, Christoph
众所周知，人类的肺是不对称和异质的，这导致了空气的不均匀分布。在本文的范围内，将分析上呼吸道树状结构对通风分布的影响，以及常规机械通风(CMV)和高频振荡通风(HFOV)的差异。比较是在正压通风的假设下进行的。因此，肺组织的力学预计将起到次要作用。因此，在上呼吸道的3D模型几何形状处以数值方式产生振荡流动。对于足够大的频率，在HFOV范围内(这里是7赫兹)，速度剖面的形状会发生变化，但这对流量分布没有明显的影响。气流分割更多地取决于气道树的几何形状，即分支长度、曲率和弯曲度。由于在二次流驱动下的进气/呼气过程中物质的迁移，发生了新鲜空气到远端分支的对流净输送。然而，根据颗粒路径线的可视化显示，二次流混合起到的作用很小。通过计算一个呼吸周期的平均流量，进一步研究了定常流动现象。研究发现，气流在上肺呼吸道的总体质量传输中只占很小的比例。
The human lung is known to be asymmetric and heterogeneous which leads to an inhomogeneous distribution of air. Within the scope of this paper the influence of the upper airway tree geometry on ventilation distribution and the differences between conventional mechanical ventilation (CMV) and high frequency oscillatory ventilation (HFOV) will be analyzed. The comparison is carried out under the assumption of positive pressure ventilation. Thereby, the mechanics of lung tissue is expected to play a minor role. Oscillatory flow is therefore generated numerically at a 3D model geometry of the upper human airways. For large enough frequencies in the range of HFOV (here 7 Hz) the shape of the velocity profiles changes, but this had no measurable influence on the flow distribution. The flow division is rather governed by airway tree geometry, i.e., branch length, curvature, and tortuosity. A convective net transport of fresh air to the distal branches occurs due to the relocation of mass during ins-/expiration driven by secondary flow. However, a mixing by secondary flow plays a minor role as was suggested by the visualization of particle pathlines. The phenomenon of steady streaming is further investigated by calculating the mean flow of one breathing cycle. Streaming was found to contribute only to a minor percentage to the overall mass transport in the upper lung airways.