Duarte J, Markus H, Harrison M J
Department of Clinical Neurology, General Hospital of Segovia, Spain.
J Neuroimaging. 1995 Oct;5(4):209-11. doi: 10.1111/jon199554209.
Hyperventilation results in a fall in carbon dioxide concentration, a fall in cerebral blood flow, and slowing of activity on the electroencephalogram. The temporal relationship and duration of these responses are uncertain, and were investigated using simultaneous monitoring of cerebral blood flow velocity and of the electroencephalograph, with end-tidal carbon dioxide monitoring. Sixteen patients and 9 normal volunteers were studied. Cerebral blood flow velocity in the middle cerebral artery was measured using transcranial Doppler sonography during 3 minutes of hyperventilation and during a 3-minute recovery period. Electroencephalographic recordings were rated by both visual score and measurement of the dominant posterior frequency. End-tidal expired carbon dioxide tension was monitored during the same hyperventilation protocol in the volunteers. Flow velocity fell rapidly during active hyperventilation. Electroencephalographic slowing closely correlated with the decrease in flow velocity (r = 0.86), but lagged behind it. In healthy volunteers capnographic records showed a very tight coupling between end-tidal carbon dioxide concentration and flow velocity (r = 0.94). Three minutes after hyperventilation, carbon dioxide concentration, cerebral blood flow velocity, and electroencephalographic activity were still not back to the resting state. The fall in both cerebral blood flow velocity and carbon dioxide concentration are related to but precede electroencephalographic slowing. The abnormalities persist for at least 3 minutes after hyperventilation and this must be taken into account in clinical electroencephalography. Transcranial Doppler sonography is well suited to monitoring short-term changes in the cerebral circulation.
过度通气会导致二氧化碳浓度下降、脑血流量减少以及脑电图活动减慢。这些反应的时间关系和持续时间尚不确定，本研究通过同时监测脑血流速度、脑电图，并监测呼气末二氧化碳来进行探究。研究对象包括16例患者和9名正常志愿者。在过度通气3分钟及随后3分钟的恢复期间，使用经颅多普勒超声测量大脑中动脉的脑血流速度。脑电图记录通过视觉评分和测量优势后频率进行评估。在志愿者进行相同过度通气方案的过程中，监测呼气末二氧化碳分压。在主动过度通气期间，血流速度迅速下降。脑电图减慢与血流速度下降密切相关（r = 0.86），但滞后于血流速度下降。在健康志愿者中，二氧化碳波形图记录显示呼气末二氧化碳浓度与血流速度之间存在非常紧密的耦合（r = 0.94）。过度通气3分钟后，二氧化碳浓度、脑血流速度和脑电图活动仍未恢复到静息状态。脑血流速度和二氧化碳浓度的下降与脑电图减慢有关，但先于脑电图减慢出现。这些异常在过度通气后至少持续3分钟，在临床脑电图检查中必须考虑到这一点。经颅多普勒超声非常适合监测脑循环的短期变化。
