Study of bubbles formation in organic tissue subjected to pressure variation environments and bubble embolism

由于环境压力的变化，有机组织中经常会产生气泡，因此气泡是导致气泡栓塞的原因之一。本文从流体力学的角度进行了实验研究，旨在阐明人工心脏瓣膜置换后的减压病和并发症：(1)在1.15 mm的小直径管道内流动时，在过饱和的液气溶液(氧气、二氧化碳、氦)中产生直径为0.06 mm~0.84 mm的气泡。还观察到气泡的并入现象和链状气泡的形成。气泡数目随着管内气体附加压力和流速的增加而增加。在溶解二氧化碳的液体中，气泡的大小和数量都大于氧气和氦中的情况。小管内的气泡流动可能是造成小动脉和小静脉阻塞的原因。(2)在肌肉模型和脂肪模型等软组织中，在高压条件下也会出现气泡。在脂肪模型中易形成二氧化碳气泡，且氦气的气泡密度比氧气、二氧化碳的气泡密度大。(3)在高速脉动流动中，发现人工瓣膜周围存在空化现象。在流量q=5L/min，平均流速v=0.57m/S的条件下，在主动脉瓣下游观察到空化泡。在主动脉瓣周围可见0.2 mm~0.5 mm大小的气泡，气泡的运动速度为0.46m/S~1.2m/S，在主动脉瓣上游，关闭瓣膜时产生爆炸性空化现象。人工瓣膜周围产生的小气泡是导致心血管系统血栓和HIT的主要原因。

Bubbles often generate in organic tissue subjected to pressure variation of environments, and consequently the bubbles are responsible for bubble embolism. In this work, the experimental studies are conducted from viewpoint of fluid dynamics in order to clarify decompression disease such as submarine sickness and complication after substitution of an artificial heart valve.(1)During the flow in the pipe with small diameter of 1.15mm, the bubbles of diameter 0.06mm〜0.84mm are generated in oversaturated liquid-gas solutions (oxygen, carbon dioxide, helium). The incorporation phenomena of bubbles and the formation of chain bubbles are also observed. The number of bubbles increase with increasing of gas additional pressure and flow velocity in pipe. In the liquids solved carbon dioxide, the size and the number of occurring bubbles are larger than the case in oxygen and helium. The bubbly flow in the small pipe may be cause of obstruction an of arteriola and venula.(2)In soft organic tissue such as musclar model and fat moder under the conditions of high gas pressure, the bubbles also occur. Carbon dioxide bubbles are easy to make in fat model, and the number of bubble density of helium is large as compare with the cases of oxygen, carbon dioxide.(3)Cavitation phenomena are detected around an artificial valve in pulsatile flow with high velocity. In the conditions of flow rate Q=5L/min and mean flow velocity v=0.57m/s, cavitation bubbles are observed in downstream of aortic valve. The bubbles of the size of 0.2mm〜0.5 mm are detected around aortic valve, and the velocities of movement of the bubbles are 0.46m/s〜1.2m/s. On the upstream side of aortic valve, cavitation phenomena are produced explosively at closing of the valve. The small bubbles produced around artificial valve are responsible for embolism in cardiovascular system and HITS.