Electrode Impedance in Neurophysiologic Recordings: 2. Role in Electromagnetic Interference

Abstract

ABSTRACT.Electromagnetic interference (EMI) is an important factor in producing a low signal-to-noise ratio during neurophysiologic recordings in electronically hostile environments such as the operating room. Using a controlled EMI generating source, both capacitative and inductive mechanisms of EMI were explored. The effects of electrode type, total electrode impedance, electrode impedance imbalance, inter-electrode distance, and electrode dipole orientation were also explored. The results of these studies indicate that although there are substantial differences in impedance between various types of electrodes, these have a significant but small effect on recorded EMI compared to other factor such as the electrode dipole orientation. From a practical perspective, the use of heterogeneous electrode combinations does not necessarily cause an increase in EMI and (after appropriate testing on an individual basis) may increase recording convenience in specialized environment such as the operating room.