Bioimpedance of Soft Tissue Under Compression and Applications to Electrosurgery.

Abstract

This research studies the impact of compression on the electrical impedance of soft tissue. Soft tissue compression occurs in many ways, either physiologically or through forces imposed by the outside world. While much work has been done in characterizing the electrical properties of soft tissues, little work has been done in correlating the compression of tissue to the subsequent changes in the electrical properties. This lack of knowledge has lead to the use of less than ideal instrumentation within electrosurgery resulting in unnecessary quality of life reduction in patients post-operatively. This research aims to quantify the impact of compression on the bioimpedance of tissue. First, a baseline for understanding thermal spread is developed by documenting the thermal history of tissue during energized surgical procedures. Then, a finite element model of the bipolar electrosurgical procedure is performed and analyzed to suggest various mechanisms that can be at play during this procedure that affect the resulting thermal profile. Next, a new instrument design is developed and tested based on these findings to eliminate thermal spread. To perform more detailed research on electrical impedance changes in compressed tissue, a bioimpedance measurement system is then developed and validated. Finally, basic tissue compression tests are performed where mechanical and electrical properties of the tissue are monitored during the tissue compression. These findings are finally correlated to suggest a mechanism for the process of tissue compression.