Proc. XXVI International Scientific Conference Electronics - ET2017, September 13 - 15, 2017, Sozopol, Bulgaria 978-1-5386-1752-6 /17/$31.00 ©2017 IEEE Arduino Based Module for Return Electrode Contact Quality Monitoring in the Electrosurgical Instruments Galidiya Petrova 1 , Georgi Yanev 1 , Grisha Spasov 2 1 Department of Electronics, 2 Department of Computer Systems and Technologies, Faculty of Electronics and Automation Technical University of Sofia, Plovdiv branch 25, TzankoDjustabanovStr , 4000 Plovdiv, Bulgaria gip@tu-plovdiv.bg, georgi.d.yanev@gmail.com,gvs@tu-plovdiv.bg Abstract – The paper describes the development and realization of an Arduino based module for monitoring the contact quality of the patient returned electrode in the electrosurgical instrument. The module is designed in accordance with the requirements of the standard IEC 60601- 2-2:209 for protection against electrical hazards from medical equipment. The experimental results of performed tests with 3 patients are presented and discussed. Keywords– Electrosurgery, Patient return electrode, Contact quality monitoring. I. INTRODUCTION Electrosurgery employs application of high radio frequency electrical current to a surgical site to cut, coagulate, ablate or seal tissue. In monopolar electrosurgery, the active electrode as part of electrosurgical instrument (ESI) is held by the surgeon and applied to the patient surface to be treated. Usually it has very small surface area as compared to the passive electrode. The smaller the electrode, the higher the current density around it, and the more localized the heating effect. In contrast, the passive electrode has a large contact surface area with patient to minimize heating at that site. The passive electrode is placed remotely from the active electrode to carry back the electrical current to the high frequency generator and safely disperse current applied by the active electrode [1]. The isolated electrosurgical instruments used in today practice eliminate many of hazards inherent in grounded systems, most importantly current division and alternative site burns. As shown on Fig. 1, the isolated generator does not include ground in the circuit, thus the high frequency (therapeutic) current can only flow through the passive electrode, called patient return electrode (PRE) [2]. Fig. 1. Isolated electrosurgical instrument [2]. However, isolation does not take care of pad site burns due to loss of contact with the patient return electrode, which leads to the problem with loss of electrical contact at patient return electrode. Even though the patient return electrode is made of highly conductive material, it needs to maintain good electrical contact, as shown on Fig. 2a, with the patient's body during the whole surgical operation in order to avoid pad site burns. If the PRE shifts or peels off, the impedance in the circuit increases, generating enough current density even at the return electrode site as it is shown on Fig. 2b [2]. Heating and burns are caused by high current densities which directly depend on the surface area. a) b) Fig. 2. Current concentration at the PRE site. According to the requirements of sub-clause 201.8.4.101 of the standard EN 60601-2-2:209 for protection against electrical hazards from medical equipment, the electrosurgical equipment should be provided with Contact Quality Monitor (CQM) of PRE. The Contact Quality Monitoring Systems work by inactivating the high- frequency generator of ESI if dangerously high impedance is detected at the return electrode/patient interface. High impedance implies the surface area in contact with the patient has decreased. In order to measure this impedance the patient return electrode is included in a separate, impedance monitoring circuit (REM), shown on Fig. 3, by dividing the electrode in two plates and measuring the voltage generated across the two parts. Such PRE, also known as 'split plate return electrode', is composed from conductive layer, usually metallic foil, split into two areas and covered in a conductive adhesive. A conductive tab provides a separate means of connection from the two areas to the high frequency generator of ESI – Fig. 4 [3]. Several REM systems based on US patents have been developed and incorporated in the commercial ESI which monitor if the measured impedance is within the predefined upper and lower limits range [4, 5]. However, the 11