Dependency on thermal and electrical conductivity in monopolar coagulation

Abstract

High-frequency surgery is a commonly used surgical procedure to mainly achieve hemostasis. Evidence for the safety and effectiveness of these applications is based on empirical data, but this is time- and cost-intensive. A reliable and validated model can remedy this situation and contribute to a better understanding of the physical processes taking place. One technique is monopolar coagulation, where tissue is slowly heated so that tissue water evaporates, the tissue shrinks, and consequently, bleeding stops. The heating of the tissue by applying high-frequency alternating current is due to Joule heating, in which the flow of current through a conductor converts some of the electrical energy into thermal energy. Based on a previous investigation, a monopolar coagulation model with a ball electrode was used to analyze the global change in current and tissue resistance. Different initial parameter values for the thermal and electrical conductivity of biological tissue were used to analyze their impact on the simulation results. The results show that a change in electrical conductivity leads to a significant change in the current flow and tissue resistance when the applied direct voltage is constant. On the other hand, a change in thermal conductivity leads to only minor changes in the results. How the changes in global current flow or tissue resistance can be used to control applied voltage or assess tissue coagulation remains to be investigated further.