A quantitative analysis of intraventricular bioimpedance in an in vivo pilot study with contextual pressure measurements

Hydrocephalus is a neurological condition characterized by disturbed cerebrospinal fluid (CSF) dynamics and is typically treated with shunt systems that drain excessive CSF out of the ventricular system. Continuous monitoring of ventricular CSF volume, however, remains a major unmet need in the clinical management of this condition. While intraventricular bioimpedance (BI) has been proposed as a potential marker of CSF volume, prior investigations have been limited to simulations, in vitro phantoms, and small animal models. This work presents the development of a measurement system for intraventricular BI and its evaluation in a large animal model. The measurement system was first validated in vitro using a mechatronic test bench replicating physiological CSF dynamics and subsequently applied in an in vivo pilot study with concurrent CSF and blood pressure monitoring. Time series analysis of the recorded signals revealed physiological BI waveform components linked to the cardiac and respiratory cycles. In addition, changes in BI following CSF volume alterations induced through intrathecal bolus infusions of artificial CSF were observed and found to be correlated to changes in CSF and blood pressures. These results provide the first in vivo evidence in a large animal model that BI reflects CSF dynamics as well as cerebral hemodynamics. Complementing intracranial pressure and CSF drainage measurements in smart shunt systems with BI could enable more comprehensive patient monitoring and physiologically informed control of hydrocephalus therapy.