New Chronic EEG Electrode for Critical/Intensive Care Unit Monitoring

The main limiting factor of EEG monitoring in the critical/intensive care environments is, and always has been, the recording electrode. The electrode and its application to the scalp has changed very little since EEG was first discovered and developed as a clinical tool. However, the evolution of amplifiers and data acquisition systems have made tremendous strides. Modern-day EEG recording systems now have the capability to record for days and weeks with little intervention, whereas the EEG electrode requires constant attention and skilled adjustment every 10 to 24 hours. If one surveys the vast array of electrodes used now and in the past, the only electrode that, once placed, never needed any further adjustment for days and weeks on end, was the chronic silver-silver/chloride (Ag-Ag/Cl) sphenoidal (Sp) electrode. This Sp electrode has now been modified to permit it to be placed subdermally, similar to that of a subdermal needle electrode, but now the needle is removed to leave in place a fine, flexible, durable, chronic Ag-Ag/Cl electrode. Once placed, this subdermal wire electrode (SWE, patent pending) starts to record immediately with a low impedance of 3 to 4 K&OHgr;. This electrode can record any biopotential, in humans and in animals, and in most recording environments; it never needs adjustment, and records high-quality biopotential signals for as long as it is left in place. The SWE is also MRI and computed-tomography compatible. It takes less than half the time to place the SWE, and placement can now be performed by any medically trained personnel to obtain a low-maintenance, high-quality EEG recording.