Assessment of Cerebral Blood Flow Autoregulation (CBF AR) with Rheoencephalography (REG): Studies in Animals

The ability of cerebral vasculature to regulate cerebral blood flow (CBF) in the face of changes in arterial blood pressure (SAP) or intracranial pressure (ICP) is an important guard against secondary ischemia in acute brain injuries, and official guidelines recommend that therapeutic decisions be guided by continuous monitoring of CBF autoregulation (AR). The common method for CBF AR monitoring, which rests on real-time derivation of the correlation coefficient (PRx) between slow oscillations in SAP and ICP is, however, rarely used in clinical practice because it requires invasive ICP measurements. This study investigated whether the correlation coefficient between SAP and the pulsatile component of the non-invasive transcranial bioimpedance signal (rheoencephalography, REG) could be used to assess the state and lower limit of CBF AR. The results from pigs and rhesus macaques affirm the utility of REG; however, additional animal and clinical studies are warranted to assess selectivity of automatic REG-based evaluation of CBF AR. Presented at the XV Int. Conf. on Electrical Bio-Impedance & XIV Conf. on Electrical Impedance Tomography. Published in the Journal of Physics: Conference Series, v434 article ID 012042, 2013. Prepared in collaboration with Walter Reed National Military Medical Center, Bethesda, MD and in cooperation with Advanced Brain Monitoring, Inc., Carlsbad, CA.