Bento David, Sousa Lúcia, Yaginuma Tomoko, Garcia Valdemar, Lima Rui, Miranda João M
School of Technology and Management (ESTiG), Polytechnic Institute of Bragança (IPB), Campus de Santa Apolónia, 5300-253, Bragança, Portugal.
Transport Phenomena Research Center (CEFT), Department of Chemical Engineering, Engineering Faculty, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
Biomed Microdevices. 2017 Mar;19(1):6. doi: 10.1007/s10544-016-0138-z.
Gas embolisms can hinder blood flow and lead to occlusion of the vessels and ischemia. Bubbles in microvessels circulate as tubular bubbles (Taylor bubbles) and can be trapped, blocking the normal flow of blood. To understand how Taylor bubbles flow in microcirculation, in particular, how bubbles disturb the blood flow at the scale of blood cells, experiments were performed in microchannels at a low Capillary number. Bubbles moving with a stream of in vitro blood were filmed with the help of a high-speed camera. Cell-free layers (CFLs) were observed downstream of the bubble, near the microchannel walls and along the centerline, and their thicknesses were quantified. Upstream to the bubble, the cell concentration is higher and CFLs are less clear. While just upstream of the bubble the maximum RBC concentration happens at positions closest to the wall, downstream the maximum is in an intermediate region between the centerline and the wall. Bubbles within microchannels promote complex spatio-temporal variations of the CFL thickness along the microchannel with significant relevance for local rheology and transport processes. The phenomenon is explained by the flow pattern characteristic of low Capillary number flows. Spatio-temporal variations of blood rheology may have an important role in bubble trapping and dislodging.
气体栓塞会阻碍血流，导致血管阻塞和局部缺血。微血管中的气泡以管状气泡（泰勒气泡）的形式循环，并可能被困住，从而阻断血液的正常流动。为了了解泰勒气泡在微循环中的流动情况，特别是气泡如何在血细胞尺度上干扰血流，研究人员在低毛细血管数的微通道中进行了实验。借助高速摄像机拍摄了气泡与体外血流一起流动的过程。在气泡下游、靠近微通道壁以及沿中心线观察到了无细胞层（CFL），并对其厚度进行了量化。在气泡上游，细胞浓度较高，CFL不太明显。虽然就在气泡上游，红细胞最大浓度出现在最靠近壁的位置，但在下游，最大值出现在中心线和壁之间的中间区域。微通道内的气泡会促进CFL厚度沿微通道的复杂时空变化，这与局部流变学和传输过程密切相关。该现象可通过低毛细血管数流动的流型特征来解释。血液流变学的时空变化可能在气泡捕获和移动中起重要作用。
