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Investigation of the relationship between transcranial impedance and intracranial pressure.

Abstract

Studies on piglets have shown that cranial bioimpedance (Z) measurements correlate well with invasively measured intracranial pressure (ICP). We have tested the feasibility of collecting transcranial impedance from a clinical device for measuring whole-body water content (ImpediMed SFB7). In the clinical study, 50 normal healthy volunteers had transcranial impedance measured using nine different head montages (forehead to mastoid (left/right), temporal to mastoid (left/right), forehead to temporal (left/right), forehead to occipital (left/right) and temporal to temporal). Impedance was measured 20 times over a frequency range per montage and ANOVA used to test for effects of electrode position upon recorded value. For the experimental study, five sedated and ventilated Marino sheep were instrumented for intraventricular ICP and transcranial impedance measurement. Measures of ICP were recorded while ICP was increased from baseline to greater than 50 mmHg in five steps using an intraventricular infusion of mock CSF. There is a significant effect of electrode position and gender upon transcranial impedance (p < 0.001). The temporal-mastoid electrode position had significantly lower impedance values in keeping with its shorter path length. ICP correlated with craniospinal compliance measurements and Impedance vs Freq by ICP step shows a clear ICP dependence (p = 0.007) across the sheep.

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  • Authors

    Shaw M, Piper I, Campbell P, McKeown C, Britton J, Oommen K, Stewart L, Whittle I, Gregson R, Clutton E

    Institution

    Department of Clinical Physics, Sothern General Hospital, Glasgow, UK. martin.shaw@nhs.net

    Source

    Acta neurochirurgica. Supplement 114: 2012 pg 61-5

    MeSH

    Adult
    Animals
    Diagnosis, Computer-Assisted
    Electric Impedance
    Electrodes
    Female
    Humans
    Intracranial Pressure
    Middle Aged
    Monitoring, Physiologic
    Regression Analysis
    Sheep
    Young Adult

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    22327665