An Experimental Study on Bipolar Tissue Hemostasis and Its Dynamic Impedance

Abstract

Bipolar tissue hemostasis is a medical procedure where high frequency alternating current is applied to biological tissue for wound closing and blood vessel sealing through heating. The process is often performed with a set of laparoscopic forceps in a minimal invasive surgery to achieve less bleeding and shorter recovery time. However, problems such as tissue sticking, thermal damage, and seal failure often occur and need to be solved before the process can be reliably used in more surgical procedures. In this study, experiments were conducted to examine process parameters and the dynamic behavior of bipolar heating process through electrical impedance measurements. The effects of electrode compression level, heating power, and time are analyzed. Heating energy and bio-impedance are evaluated for quality prediction. Tissue sticking levels were correlated to the size of denatured tissue zone. It is found that tissue denaturation starts from the center of the heated region. Dynamic impedance reveals the stages of tissue hemostasis process. However, it is strongly affected by the compression level and heating power. Existing criteria for quality prediction and control using the heating energy and minimal impedance are not reliable. The size of denatured tissue zone can be predicted with the heating energy; however, the prediction is strongly dependent on the compression level. To avoid sticking, a low power and low compression level should be used for the same denatured tissue zone size.