Berg Emily J, Robinson Risa J
Department of Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Drive, Building 9, Rochester, NY 14623, USA.
J Biomech Eng. 2011 Jun;133(6):061004. doi: 10.1115/1.4004251.
Emphysema is a progressive lung disease that involves permanent destruction of the alveolar walls. Fluid mechanics in the pulmonary region and how they are altered with the presence of emphysema are not well understood. Much of our understanding of the flow fields occurring in the healthy pulmonary region is based on idealized geometries, and little attention has been paid to emphysemic geometries. The goal of this research was to utilize actual replica lung geometries to gain a better understanding of the mechanisms that govern fluid motion and particle transport in the most distal regions of the lung and to compare the differences that exist between healthy and emphysematous lungs. Excised human healthy and emphysemic lungs were cast, scanned, graphically reconstructed, and used to fabricate clear, hollow, compliant models. Three dimensional flow fields were obtained experimentally using stereoscopic particle image velocimetry techniques for healthy and emphysematic breathing conditions. Measured alveolar velocities ranged over two orders of magnitude from the duct entrance to the wall in both models. Recirculating flow was not found in either the healthy or the emphysematic model, while the average flow rate was three times larger in emphysema as compared to healthy. Diffusion dominated particle flow, which is characteristic in the pulmonary region of the healthy lung, was not seen for emphysema, except for very small particle sizes. Flow speeds dissipated quickly in the healthy lung (60% reduction in 0.25 mm) but not in the emphysematic lung (only 8% reduction 0.25 mm). Alveolar ventilation per unit volume was 30% smaller in emphysema compared to healthy. Destruction of the alveolar walls in emphysema leads to significant differences in flow fields between the healthy and emphysemic lung. Models based on replica geometry provide a useful means to quantify these differences and could ultimately improve our understanding of disease progression.
肺气肿是一种进行性肺部疾病，涉及肺泡壁的永久性破坏。肺部区域的流体力学以及它们如何因肺气肿的存在而改变，目前还没有得到很好的理解。我们对健康肺部区域发生的流场的许多理解是基于理想化的几何形状，而对肺气肿的几何形状关注很少。本研究的目的是利用实际的复制肺几何形状，更好地理解控制肺部最远端区域流体运动和颗粒传输的机制，并比较健康肺和肺气肿肺之间存在的差异。对切除的人类健康肺和肺气肿肺进行铸型、扫描、图形重建，并用于制造透明、空心、顺应性模型。使用立体粒子图像测速技术，在健康和肺气肿呼吸条件下通过实验获得三维流场。在两个模型中，从管道入口到壁的测量肺泡速度范围跨越两个数量级。在健康模型和肺气肿模型中均未发现回流，而肺气肿模型中的平均流速是健康模型的三倍。除了非常小的颗粒尺寸外，在肺气肿中未观察到以健康肺的肺部区域为特征的扩散主导的颗粒流。流速在健康肺中迅速消散（在0.25毫米内降低60%），但在肺气肿肺中则不然（在0.25毫米内仅降低8%）。与健康肺相比，肺气肿中单位体积的肺泡通气量小30%。肺气肿中肺泡壁的破坏导致健康肺和肺气肿肺之间的流场存在显著差异。基于复制几何形状的模型提供了一种量化这些差异的有用方法，并最终可能改善我们对疾病进展的理解。
