Correlation of rheoencephalography and laser Doppler flow: a rat study

Michael Bodo, Ryan Sheppard, Aaron Hall, Martin Baruch, Melissa Laird, Shravalya Tirumala, Richard Mahon


Measuring brain electrical impedance (rheoencephalography) is a potential technique for noninvasive, continuous neuro-monitoring of cerebral blood flow autoregulation in humans.    In the present  rat study,  we compared   changes in cerebral  blood flow autoregulation  during  CO2 inhalation measured by  rheoencephalography to changes measured by  laser Doppler  flowmetry,  an invasive continuous monitoring modality.    Our hypothesis was that both modalities would reflect  cerebral blood flow autoregulation. 

   Male Sprague-Dawley rats (n=28; 28 control and 82 CO2 challenges) were measured  under anesthesia. The surgical preparation involved implantation of intracerebral REG electrodes and an LDF probe into the brain. Analog waveforms were stored in a  computer.    

    CO2 inhalation caused transient, simultaneous increases  in the signals of  both laser Doppler flow   (171.99 ± 46.68 %) and  rheoencephalography  (329.88 ± 175.50%).  These results showed a correlation between the two measured modalities;  the  area under the receiver operating characteristic curve was 0.8394.

    The similar results obtained  by measurements  made with  laser Doppler flowmetry and rheoencephalography  indicate  that rheoencephalography, like laser Doppler flowmetry,  reflects cerebral blood flow autoregulation.  Rheoencephalography therefore shows  potential for use as a continuous neuro-monitoring technique.   


neuro-monitoring, laser Doppler flow, rheoencephalogram, CO2 inhalation, animal study (rat)

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