Electrosurgical dispersive electrodes heat cutaneous and subcutaneous skin layers

Electrosurgical return electrodes can produce heating, and occasionally burns, of cutaneous and subcutaneous skin layers. Up to now, only limited aspects of modern, dispersive, polymer electrodes have been studied using infrared thermography and thermocouples. This report presents new results on a quantitative infrared study, and adds the aspects of subcutaneous effects using microwave thermography as a third dimension. In agreement with previous work in infrared thermography, average cutaneous temperature increases observed in a dozen human volunteers were 1.5 degrees C for the normal mode, and 5.7 degrees C at near-fault (with partial contact). The intradermal and/or subcutaneous microwave thermographic images exhibited slightly lower, but still significant temperature elevations which were located at a more leading location, and were more widespread. This significant heating of subcutaneous layers, particularly of the sensitive stratum germinativum, clearly suggests the need for multiple-depth (microwave and infrared) thermography in order to evaluate the thermal performance of dispersive electrosurgical return electrodes.