INTRACRANIAL PRESSURE: SPECTRAL CHARACTERISTICS OF B-WAVES AND OTHER LOW-FREQUENCY ACTIVITY.
INTRACRANIAL PRESSURE: SPECTRAL CHARACTERISTICS OF B-WAVES AND
OTHER LOW-FREQUENCY ACTIVITY. Michael L. Daley, Dien Nguyen, Matthew J.
L. Connolly, Shelley Timmons, John Angel, and Charles W. Leffler, The
University of Memphis, Memphis, Tennessee (MLD, DN, MJLC), and The
University of Tennessee, Memphis, Memphis, Tennessee (ST, JA, CWL). Low
frequency oscillations of intracranial pressure (ICP) in the range of
0.5 to 2.0 cycles/min have been termed B-waves. Such oscillations may or
may not be synchronized with ventilation and/or arterial blood pressure.
The objectives of this study were to: 1) describe the low frequency
spectral characteristics of ICP and ABF recordings with a mathematical
model based on pleural pressure modulation of the vasculature, and 2)
classify B-waves and other slow wave activity according to their
spectral properties. The linear modulation model predicted the frequency
location of spectra associated ventilation of six clinical pressure
recordings with B-waves to within a 1% error. Var iation of heart-rate
was not associated with the occurrence of B-waves. It is concluded that
the low frequency spectra of ICP recordings containing waves
synchronized with ventilation can be accurately described by a
mathematical model of modulation by pleural pressure.