Lin H Y, Bianccucci B A, Deutsch S, Fontaine A A, Tarbell J M
Bioengineering Department, Penn State University, University Park 16802-4400, USA.
J Biomech Eng. 2000 Aug;122(4):304-9. doi: 10.1115/1.1287171.
Clinical studies using transcranial Doppler ultrasonography in patients with mechanical heart valves (MHV) have detected gaseous emboli. The relationship of gaseous emboli release and cavitation on MHV has been a subject of debate in the literature. To study the influence of cavitation and gas content on the formation and growth of stable gas bubbles, a mock circulatory loop, which employed a Medtronic-Hall pyrolytic carbon disk valve in the mitral position, was used. A high-speed video camera allowed observation of cavitation and gas bubble release on the inflow valve surfaces as a function of cavitation intensity and carbon dioxide (CO2) concentration, while an ultrasonic monitoring system scanned the aortic outflow tract to quantify gas bubble production by calculating the gray scale levels of the images. In the absence of cavitation, no stable gas bubbles were formed. When gas bubbles were formed, they were first seen a few milliseconds after and in the vicinity of cavitation collapse. The volume of the gas bubbles detected in the aortic track increased with both increased CO2 and increased cavitation intensity. No correlation was observed between O2 concentration and bubble volume. We conclude that cavitation is an essential precursor to stable gas bubble formation, and CO2, the most soluble blood gas, is the major component of stable gas bubbles.
使用经颅多普勒超声对机械心脏瓣膜（MHV）患者进行的临床研究已检测到气体栓子。气体栓子释放与MHV上的空化作用之间的关系一直是文献中的一个争论主题。为了研究空化作用和气体含量对稳定气泡形成和生长的影响，使用了一个模拟循环回路，该回路在二尖瓣位置采用了美敦力 - 霍尔热解碳盘形瓣膜。一台高速摄像机可观察流入瓣膜表面上的空化作用和气泡释放情况，作为空化强度和二氧化碳（CO₂）浓度的函数，同时一个超声监测系统扫描主动脉流出道，通过计算图像的灰度水平来量化气泡产生情况。在没有空化作用的情况下，未形成稳定气泡。当形成气泡时，它们首先在空化作用崩溃后的几毫秒内且在其附近被观察到。在主动脉通道中检测到的气泡体积随着CO₂增加和空化强度增加而增大。未观察到氧气浓度与气泡体积之间存在相关性。我们得出结论，空化作用是稳定气泡形成的必要前提，而CO₂作为血液中最易溶解的气体，是稳定气泡的主要成分。
