Novel Noninvasive Method of Cerebrovascular Blood Volume Assessment Using Brain Bioimpedance

Mohamad H. Tiba, Brendan M. McCracken, Sardar Ansari, Ashwin Belle, Brandon C. Cummings, Venkatakrishna Rajajee, Parag G. Patil, Hasan B. Alam, Kevin R. Ward*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Cerebrovascular autoregulation (CAR) is the ability of vessels to modulate their tone in response to changes in pressure. As an auto-protective mechanism, CAR is critical in preventing secondary brain injury post-trauma. Monitoring of changes in cerebral blood volume might be valuable in evaluating CAR and response to various therapies. In this study, we utilized an ocular-brain bioimpedance interface to assess real time changes in cerebral blood volume in response to a number of physiological challenges. We hypothesize that changes in brain bioimpedance (dz) would track changes in cerebral blood volume. Anesthetized animals were instrumented for monitoring of intracranial pressure (ICP), mean arterial blood pressure, cerebral perfusion pressure (CPP) and cerebral blood flow (CBF). Bioimpedance was monitored continuously through electrocardiographic electrodes placed over the eyelids. Interventions such as hyperventilation, vasopressor administration, creation of an epidural hematoma, and systemic hemorrhage were used to manipulate levels of ICP, CPP, and CBF. The dz correlated with changes in ICP, CPP, and CBF (r = -0.72 to -0.88, p < 0.0001). The receiver operating characteristic for dz at different thresholds of CPP and CBF showed high impedance performance with area under the curve between 0.80-1.00 (p < 0.003) and sensitivity and specificity varying between 83%-100% and 70%-100%, respectively. Our preliminary tests show that brain bioimpedance as measured through the ocular-brain interface tracks changes in CPP and CBF with high precision and may prove to be valuable in the future in assessing changes in cerebral blood volume and CAR.

Original languageEnglish (US)
Pages (from-to)3089-3096
Number of pages8
JournalJournal of neurotrauma
Issue number22
StatePublished - Nov 15 2017
Externally publishedYes


  • CBF autoregulation
  • bioimpedance
  • blood flow
  • cerebral blood volume
  • traumatic brain injury

ASJC Scopus subject areas

  • Clinical Neurology


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