[Spectral analysis of cerebrospinal fluid pulse wave].

The change of the cerebrospinal pressure wave from during the continuous monitoring of intracranial 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, fundamental wave of cardiac origin and its 2nd and 3rd 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 fundamental 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.