Impedance Controlled Hot Snare Polypectomy

This paper explores the ability to measure the impedance of a system consisting of the biological system of the patient combined with the mechanical system of the hot snare and, given a specified impedance threshold value, turn off the firing of an electrosurgical device before serious injury occurs. In electrosurgery, the tissue damage is caused by the thermal energy generated from the resistance in the cells. An impedance feedback control system is designed and tested to minimize the effects of too much thermal damage. This design is based on measuring the impedance of the system and implementing a microcontroller to coordinate the activity and to interrupt the electrosurgical device preventing further firing. The feedback control system was proven to automatically stop the electrosurgical device for three given impedance values of 500Ω, 750Ω, and 1000Ω with an accuracy of ±5Ω. The auto-stop system is able to measure and fire at 5.4 times a second with a duty cycle of 41%. This successfully minimizes the thermal injury sustained from electrosurgery.