Current Density Imaging and Electrically Induced Skin Burns Under Surface Electrodes

Abstract

Abstract-The origin of electrical burns under gel-type surface electrodes is a controversial topic that is not well understood. To investigate the phenomenon, we have developed an excised porcine skin-gel model, and used low-frequency current density imaging (LFCDI) to determine the current density (CD) distribution through the skin before and after burns were induced by application of electrical current (200 Hz, 70% duty cycle, 20-35 mA monophasic square waveform applied to the electrodes for 30-135 min). The regions of increased CD correlate well with the gross morphological changes (burns) observed. The measurement is sensitive enough to show regions of high current densities in the pre-burn skin, that correlate with areas were burn welts were produced, thus predicting areas where burns are likely to occur. Statistics performed on 28 skin patches revealed a charge dependency of the burn areas and a relatively uniform distribution. The results do not support a thermal origin of the burns but rather electro-chemical mechanisms. We found a statistically significant difference between burn area coverage during anodic and cathodic experiments.

Impacts of selected stimulation patterns on the perception threshold in electrocutaneous stimulation

“…A previous study based on ultrasonic imaging techniques demonstrated that the skin is thicker on the dorsal than volar forearm [26]. Even within the skin area under a surface gel-type electrode, the electrical current density is distributed unevenly due to uneven skin resistivity [27]. The result that E1 and E2 (ventral side) had lower PTs while E4 (dorsal side) had a higher PT, assists to strengthen our speculation that lower skin impedance led to lower PT.…”

The Effects of Concentric Ring Electrode Electrical Stimulation on Rat Skin

“…Surface electrodes are the most commonly used electrodes clinically, in applications as diverse as functional electrical stimulation for the restoration of motor functions, pain relief, transcutaneous electrical nerve stimulation, defibrillation, surface cardiac pacing, and advanced drug delivery systems 27. Common to these applications are occasional reports of pain, tissue damage, erythema, rash, or burns on the skin at the point where electrodes are placed 1,3,11,18,19,24,28,30,31,33.…”

“…In a review by Merrill et al ,20 although mainly for implantable stimulation techniques, several possible mechanisms of injury are discussed which are still pertinent for noninvasive electrical stimulation. A common factor contributing to all the above mentioned mechanisms are regions of high current density 13,17,22,26,27. Overmyer et al 24 modeled this phenomenon and found from experimental observations that the area of the highest temperature increase, or burns, was usually at the edge of the electrode.…”

Current density imaging sequences with separation of mobile-ion current from immobile-ion current

“…A few of these applications are defibrillation [15], electroporation [16], bone fracture healing by currents [17], studying electrically induced skin burns [18], specific radiofrequency absorption rate (SAR) distribution measurements [19] and studying brain conductivity changes during transcranial stimulation [20] or spreading depression [21]. Additionally, CDI has become a complimentary method in the verification and development of new electrical impedance tomography (EIT) methods [22,23].…”