This paper goes through the process of first designing a feedback system that allows for the measuring of impedance while using the hot snare polypectomy method. The electrosurgical unit used in this study was the Olympus PSD-30. After the impedance-controlled feedback system was completed, the device was tested under a range of power settings from 10 W–50 W. The test was performed ex vivo using porcine colon samples. Using the information gathered from these tests, a technique of determining the threshold of perforation and implementing a system to automatically stop the applied current from the PSD-30 was developed. The data showed that after an increase in impedance of 25% from that of the initially measured impedance, perforation ensued in the tissue samples. Using this information, the device was programmed to interrupt the PSD-30 at this threshold point. This final design was tested and proved able to automatically prevent the event of perforation from occurring, resulting in the ability to prevent serious complications.

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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.