Optimal Electrode Designs for Electrosurgery, Defibrillation, and External Cardiac Pacing

We have developed a simple and easily modifiable two-dimensional finite element computer model of the human torso, which allows us to predict current delivery from arbitrarily placed and designed electrodes. Using this model, the performance of many variations from the commonly used gelled-pad electrode, applied to a torso of uniform and isotropic resistivity, has been examined by independently varying the thickness, width, and resistivity of the gel layer, as well as the width of the conducting plate. We compared the electrode performances on the basis of their ability to maintain a uniform current density at the electrode-body interface, which is thought to be of critical concern in avoiding burn, pain, and other complications in electrosurgery, external cardiac pacing, and defibrillation. In addition to studying the effects of geometric and electrical design variations, we have isolated two electrode designs of particular importance: 1) a simple plate electrode with a uniformly high resistivity gel layer and intermediate conducting plate width, which could be used for low-energy applications such as external cardiac pacing, and 2) an annular electrode in which the resistivity of the gel varies as a function of distance to the electrode center, which could be used for high-energy applications such as electrosurgery and defibrillation, as well as for external cardiac pacing.