Blaber A P, Bondar R L, Stein F, Dunphy P T, Moradshahi P, Kassam M S, Freeman R
School of Kinesiology, Faculty of Health Sciences, University of Western Ontario, London, Canada.
Stroke. 1997 Sep;28(9):1686-92. doi: 10.1161/01.str.28.9.1686.
Autonomic nervous system diseases affect systemic blood pressure regulation. Patients with autonomic nervous system diseases have consistently larger drops in blood pressure associated with standing than the normal population. Autonomic dysfunction and/or these changes in blood pressure may affect dynamic cerebral autoregulation.
Heart rate, mean blood flow velocity (MBFV) of the middle cerebral artery via transcranial Doppler ultrasound, mean arterial blood pressure adjusted to brain level (MABPbrain) via Finapres, and end tidal CO2 were measured continuously during graded tilt (after 5 minutes in supine position as baseline, -10 degrees, +10 degrees, +30 degrees, +60 degrees, -10 degrees, and supine recovery) in autonomic failure patients and their age- and sex-matched control subjects. The dynamic response of MBFV to spontaneous variations in MABPbrain was investigated by cross-spectral analysis. The transfer gain and phase relationships between MBFV and MABPbrain were determined from the final 256 beats of each 5-minute-tilt segment. The transfer gain was normalized to mean MABPbrain and MBFV and then converted to decibels (dB).
MBFV variation (0.03 to 0.14 Hz) preceded MABPbrain by similar phase angles in patients and control subjects and in all tilt conditions (patients: 31 +/- 5 degrees; control subjects: 30 +/- 5 degrees; mean +/- SEM). Patients had a higher supine gain than control subjects (P < .05). Both patients and control subjects showed a significant decrease in gain with tilt and by 60 degrees the patients were not different from the control subjects (supine to 60 degrees: patients = 5.23 +/- 0.77 to -1.65 +/- 0.89 dB; control subjects = 1.74 +/- 0.82 to -1.80 +/- 0.62 dB).
These data indicate an altered, yet present, autoregulatory response with autonomic failure.
自主神经系统疾病会影响全身血压调节。自主神经系统疾病患者站立时血压下降幅度始终大于正常人群。自主神经功能障碍和/或这些血压变化可能会影响动态脑自动调节。
在自主神经功能衰竭患者及其年龄和性别匹配的对照受试者进行分级倾斜试验期间（仰卧位5分钟作为基线，-10度、+10度、+30度、+60度、-10度以及仰卧位恢复），连续测量心率、经颅多普勒超声测量的大脑中动脉平均血流速度（MBFV）、通过Finapres测量的调整至脑水平的平均动脉血压（MABPbrain）以及呼气末二氧化碳。通过互谱分析研究MBFV对MABPbrain自发变化的动态反应。从每个5分钟倾斜段的最后256次心跳中确定MBFV与MABPbrain之间的传递增益和相位关系。传递增益经平均MABPbrain和MBFV归一化后转换为分贝（dB）。
在患者和对照受试者以及所有倾斜条件下，MBFV变化（0.03至0.14赫兹）在相位角上先于MABPbrain出现相似情况（患者：31±5度；对照受试者：30±5度；平均值±标准误）。患者仰卧位增益高于对照受试者（P<0.05）。患者和对照受试者的增益均随倾斜而显著降低，到60度时患者与对照受试者无差异（仰卧位至60度：患者=5.23±0.77至-1.65±0.89 dB；对照受试者=1.74±0.82至-1.80±0.62 dB）。
这些数据表明自主神经功能衰竭时存在改变但仍存在的自动调节反应。
