Measurement of Blood Flow Velocity in Cerebral Microvessels by a Fiber-Optic Laser-Doppler Anemometer Microscope

本研究旨在建立光纤激光多普勒显微镜（FLDAM）测量软脑膜微血管内红细胞流速的可行性，并分析颅内压升高时软脑膜微血管内血流动力学的变化。用FLDAM成功地测量了直径为10~230 μ m的软脑膜微血管中红细胞的运动速度，微动脉中的红细胞运动速度与心跳同步，呈规律性脉动，其幅度可达平均速度的46%，而微静脉中的红细胞运动速度仅呈小幅度的随机波动。速度脉动幅度定义为系综平均速度最大值与最小值之差的一半。小动脉的时间平均流速随时间的增加而增加， ...更多信息 直径.直径为10和50 μ m的小动脉平均流速分别为3.5和14 mm/s。微动脉内流速相对于股动脉压的时滞随沿血管从上游到下游的距离沿着增加，这表明血流脉冲沿着微动脉传播。测定了几个软脑膜小动脉的血流脉冲传播速度。颅内压在10~115 cm/s之间。通过改变植入大鼠闭合颅窗的内压，研究颅内压（ICP）对软脑膜微循环的影响。当ICP从0增加到50 mmHg时，微静脉的平均直径从1.1单调减小到0.78，其中直径通过ICP = 5mmHg时的直径归一化。另一方面，在小静脉的时间平均速度从0.85单调增加到1.91。结果表明，ICP对微静脉的容积流速无明显影响，微动脉的容积流速变化较微静脉小。在一定的ICP值范围内，微动脉流速脉动幅度随ICP的增加呈阶梯状增加，ICP_<cr '>随血管位置的不同而不同。ICP_随血管直径的增加而增加，沿微动脉由上至下沿着逐渐减小，表明ICP_代表微动脉在某一搏动时相的血管内压力。<cr><cr>少

This research project was aimed to establish the applicability of our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) to the measurement of red cell velocity in the cerebral pial microvessels and was also aimed to analyze the blood flow dynamics under the increased intracranial pressures.A closed cranial window was implanted on one side of the parietal region of rats to observe the brain pial microcirculation. The red cell velocity in single pial microvessels with diameter range from 10 to 230 mum was successfully measured by the FLDAM.The red cell velocity in arterioles showed regular pulsation synchronous with the heart beats with amplitude up to 46 % of the mean velocity, while the velocity in venules only showed random fluctuations with small amplitude. The amplitude of velocity pulsation was defined as the half of the difference betweenthe maximum and minimum of the ensemble average velocity. The temporal mean velocity in the arterioles increased with increasing … More diameter. It was 3.5 and 14 mm/s for the arteriole with 10 and 50 mum in diameter, respectively, on an average. The time lag of the velocity in the arteriole relative to the femoral arterial pressure increased with the distance along the vessel from upstream to downstream, which indicates the propagation of flow pulse along the arteriole. The propagation velocity of flow pulse was determined for several pial arterioles. It ranged between 10 and 115 cm/s.Effects of intracranial pressure (ICP) on the pial microcirculation were studied by changing the internal pressure of the closed cranial window implanted in the rats. The average diameter of venules decreased monotonically from 1.1 to 0.78 as the ICP increased from 0 to 50 mmHg, where the diameter is normalized by the diameter at ICP=5mmHg. On the other hand, the temporal mean velocity in venules increased monotonically from 0.85 to 1.91. As a result, the volume flow rate in venules did not change significantly with ICP.The changes of arterioles with ICP were small compared with those of venules. The amplitude of velocity pulsation in arterioles showed stepwise increase with ICP at a certain value of ICP,ICP_<cr'> which depended on the location of the vessel. ICP_<cr> increased with increasing vessel diameter and decreased from upstream to downstream along an arteriole, suggesting that ICP_<cr> represents the intravascular pressure of the arteriole at a certain phase of pulsation. Less