Indexes of flow and cross-sectional area of the middle cerebral artery using Doppler ultrasound during hypoxia and hypercapnia in humans
Indexes of flow and cross-sectional area of the middle cerebral artery using Doppler ultrasound during hypoxia and hypercapnia in humans
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DOI：
10.1161/01.str.27.12.2244
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发表时间：
1996-12-01
期刊：
影响因子：
8.3
通讯作者：
Robbins, PA
中科院分区：
文献类型：
--
作者：
Poulin, MJ;Robbins, PA
背景和目的本研究以低氧和高二氧化碳状态下多普勒信号功率的变化来评估大脑中动脉横截面积的变化。此外，还检查了速度谱轮廓()、强度加权平均速度()和大脑中动脉血流指数(P)三项脑血流速度指标之间的一致性程度。P。被计算为乘以总功率信号的乘积。功率与血管横截面积成正比，因此这一计算允许该变量的任何变化。方法使用四种方案，每种方案重复六次，年龄20.8+/-1.7岁(平均+/-SD)。第一个是控制方案(A)，呼气末PO2(ETPO(2))始终保持在100 mm Hg，ETPCO(2)始终保持在桉树上方1~2 mm Hg。第二组为低氧阶梯方案(B)，ETPO(2)从对照组降至50 mm Hg，持续20分钟。第三组为高碳酸组(C)，ETPCO(2)较对照组升高7.5 mm Hg，持续20分钟。第四组为低氧高碳酸血症联合方案(D)，持续20分钟。采用动态潮气末强迫系统控制ETPCO(2)和ETPO(2)。每10毫秒收集和存储一次多普勒数据，并在稍后逐个节拍地确定平均值。、、幂和P。结果A、B两组功率无明显变化，P>0.05，P>0.05。C组在高碳酸血症缓解时，与P组相比，功率有一过性无显著增加，两者均有一过性无显著下降。D组在刺激期显著高于D组(配对t检验，P
Background and Purpose This study examined changes in cross-sectional area of the middle cerebral artery as assessed by changes in Doppler signal power during hypoxia and hypercapnia. In addition, it examined the degree of consistency among three indexes of cerebral blood flow and velocity: the velocity spectral outline (), the intensity-weighted mean velocity (), and an index of middle cerebral artery flow (P .). P . was calculated as the product of multiplied by the total power signal. Power is proportional to cross-sectional area of the vessel; this calculation therefore allows for any changes in this variable.Methods Four protocols were used, each repeated six times for six healthy adults aged 20.8 +/- 1.7 years (mean +/- SD). The first was a control protocol (A) with end-tidal PO2 (ETPO(2)) maintained at 100 mm Hg and ETPCO(2) at 1 to 2 mm Hg above eucapnia throughout. The second was a hypoxic step protocol (B) with ETPO(2) lowered from control values to 50 mm Hg for 20 minutes. The third was a hypercapnic step protocol (C) with ETPCO(2) elevated from control by 7.5 mm Hg for 20 minutes. The fourth was a combined hypoxic and hypercapnic step protocol (D) lasting 20 minutes. A dynamic end-tidal forcing system was used to control ETPCO(2) and ETPO(2). Doppler data were collected and stored every 10 milliseconds, and mean values were determined later on a beat-by-beat basis. , , power, and P . were expressed as a percentage of the average value over a 3-minute period before the step.Results In protocols A and B, there were no changes in power and there were no differences between , , and P .. In C, at the relief from hypercapnia, there was a transient nonsignificant increase in power and a transient nonsignificant decrease in both and compared with P .. In D, during the stimulus period, was significantly higher than (paired t test, P