脳血流動態とImpedance Plethysmography

INTRACEREBRAL IMPEDANCE PLETHYSMOGRAPHY AND CEREBRAL HEMODYNAMICS

緒言

　脳循環血流量の測定は，種々の脳疾患の病態生理を研究するためには，欠くべからざる情報である。

　動物における脳循環測定の歴史は，1928年Forbes^1）の行つた頭蓋骨窓法に始まり，以後髄液圧plethysmogra—ph法^2）等が考案されたが，1956年Ingvar and Söder—bergによりVenous Outflow Measuringのtechniqueが開発され^3），電磁流量計^4）の利用と共に，動物における脳全体での血流量が測定されるようになつた。また脳局所循環測定法としてはThermocoupleを使用したGibbs^5）のThermodilution TechniqueあるいはThe—rmistor法^16）等がある。

A method of the impedance plethysmography in intracerebral blood flow measurements has been reported as a powerfull tool. But the origen of the impedance change has not been clarified theo-retically. In this paper, the electrode impedance in physiological saline, in blood plasma, in blood and in cerebral subcortex of a dog are studied in detail. And it is found that the intracerebral impedance plethysmography, in which needle type electrodes are generally used, almost always does not reflect the regional cerebral blood flow. The impedance change of the electrodes in subcortex shows only the mechanical movements of the elect-rodes, which are induced by brain displacements relating to the heart cycle, or to the respiration.

The blood flow rate in narrow vessels may be observed directly as impedance change, when fine electrodes are inserted into vessel

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