Electrical Bioimpedance Cerebral Monitoring: Fundamental Steps towards Clinical Application

Sammanfattning: Neurologically related injuries cause a similar number of deaths ascancer, and brain damage is the second commonest cause of death in theworld and probably the leading cause of permanent disability. Thedevastating effects of most cases of brain damage could be avoided if itwere detected and medical treatment initiated in time. The passiveelectrical properties of biological tissue have been investigated for almost acentury and electrical bioimpedance studies in neurology have beenperformed for more than 50 years. Even considering the extensive effortsdedicated to investigating potential applications of electrical bioimpedancefor brain monitoring, especially in the last 20 years, and the specificallyacute need for such non-invasive and efficient diagnosis support tools,Electrical Bioimpedance technology has not made the expectedbreakthrough into clinical application yet. In order to reach this stage inthe age of evidence-based medicine, the first essential step is todemonstrate the biophysical basis of the method under study. The presentresearch work confirms that the cell swelling accompanying thehypoxic/ischemic injury mechanism modifies the electrical properties ofbrain tissue, and shows that by measuring the complex electricalbioimpedance it is possible to detect the changes resulting from braindamage. For the development of a successful monitoring method, after thevital biophysical validation it is critical to have available the properelectrical bioimpedance technology and to implement an efficient protocolof use. Electronic instrumentation is needed for broadband spectroscopymeasurements of complex electrical bioimpedance; the selection of theelectrode setup is crucial to obtain clinically relevant measurements, andthe proper biosignal analysis and processing is the core of the diagnosissupport system. This work has focused on all these aspects since they arefundamental for providing the solid medico-technological backgroundnecessary to enable the clinical usage of Electrical Bioimpedance forcerebral monitoring.