髄液脈波のスペクトル分析

SPECTRAL ANALYSIS OF CEREBROSPINAL FLUID PULSE WAVE

　抄録　頭蓋内圧の持続モニターにおいて圧上昇につれて圧波形が正弦波に似てくる事はしばしば経験される。この現象の機序を解明するため，フーリエ変換によるスペクトル分析を用いて髄液圧の変化とスペクトル成分との関係を解析した。髄液脈波には呼吸運動および心拍由来の成分が含まれ，さらに心拍性成分は心拍と同じ周波数の基礎波およびその2倍，3倍の周波数をもつ2つの高調波から成り立っていることが示された。腰椎クモ膜下腔にラクテートリンゲル液を注入して圧を上昇させた時のこれら心拍性成分の変化を見たところ，いずれの成分の振幅も圧上昇とともに直線的に増大し，有意の相関が示された。ところが各々の振幅の増大率は基礎波が最大で，3倍の周波数をもつ高調波で最小であり，圧上昇は高周波成分の相対的減少を起こすことが認められた。これは髄液システムが高周波成分の伝達を妨げる「high-cut filter」としての作用を持つことを意味している。このような作用が生じるメカニズムについて，電気回路モデル等を参考にして検討した。

The change of the cerebrospinal pressure wave form during the continuous monitoring of intra-cranial pressure is often experienced. We supposed that this phenomenon would be the result of the change of transmission of spinal fluid pulse through the cerebrospinal fluid (CSF) system. Our study was performed to determine the change of auto power spectrum of CSF pulse when CSF pressure was increased by the slow infusion of lactate linger solution. The spectrum of CSF pulse was found to be composed of four main waves ; wave derived from the respiratory movement, funda-mental wave of cardiac origin and its 2nd and 3 rd harmonic waves. The power of waves derived from the cardiac beats were increased when CSF pressure was elevated by the slow infusion, but the degree of increment was larger in the funda-mental wave than harmonic waves. Elevation of CSF pressure caused relative attenuation of the harmonic waves included in CSF pulse. From the result of this study we found that CSF system would have the function of "high-cut filter" and its cut-off frequency was lowered by the slow infusion of lactate linger solution.