DEVELOPMENT OF FLEXIBLE ELECTRODE-BASED SEMG INSTRUMENTATION SYSTEM FOR SUPRAHYOID MUSCLE SIGNAL EVALUATION IN SWALLOWING ACTIVITY

• Main Author: Ridwan Heru Santoso, Rengganis
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84263
• Institution: Institut Teknologi Bandung

Dysphagia is a swallowing dysfunction that often occurs in stroke patients. Vide- ofluoroscopy Swallow Study (VFSS) is considered as gold standard in dysphagia evaluation. However, the usage of x-ray in VFSS limits its usage frequency to reduce radiation-related risk for both patients and operators. Surface electromyography (sEMG) can be used as a supportive tools in dysphagia evaluation. This method utilizes no ionic radiation and operated at low power. Even so, the conventional electrode made of Ag/AgCl has a rigid structure and large adhesive foam. This often made it diflcult to adhere into various neck profile. It is also occured that the electrolyte gel in Ag/AgCl electrode causes irritation on several patients. As a solution for problems related to conventional electrode, a flexible electrode has been developed by using caraagenan-based bioplastic as a substrate that is mixed with graphite and silver nanoparticles (graphite-AgNP). The flexible electrode is a dry-type electrode with an adjustable size. It is also integrated with a snap button that is compatible with commercially-available sEMG instrumentation system. Impedance analysis has been performed to both electrodes using Digilent Analog Discovery 2 with a sweeping frequency from 10 to 1000 Hz and input signal amplitude of 10 mV. The analysis were repeated 30 times for each electrode. As the results, both electrodes have a capacitive characteristics and similar impedance curve trends. Both have largest impedance magnitude at 10 Hz and exponentially decreased until reach their lowest value at 1000 Hz. The flexible electrode has a parallel resistance value ranging from 612.65 ± 2.06 ? to 13578 ± 97.47 ? and parallel capacitance 2.29 ± 0.00 ????F to 0.17 ± 0.00 ????F. As a comparison, the conventional electrode has a parallel resistance value of 129.71 ± 0.50 ? to 1213 ± 17.61 ? and parallel capacitance value of 0.53 ± 0.00 ????F to 8.10 ± 0.16 ????F. A flexible electrode-based sEMG instrumentation system prototype has been developed by using ESP-32 as the mainboard and BioAmp EXG Pill from Upside Down Labs as the biosignal amplifier. The system prototype has ADC resolution of 12-bit with a sampling frequency of 500 Hz. Signal filtering were performed on-board in real-time using IIR digital filters. A bandpass filter was implemented with a passband frequency of 10 to 248 Hz. Several bandstop filters were implemented T 50, 100, 150, and 200 Hz to eliminate power-grid interference. This system is an open-source system and all source code used on this system can be accessed online. A sEMG instrumentation system FlexComp Infiniti from Thought Technology Ltd. (2048 Hz sampling frequency, 14-bit) with Ag/AgCl electrode was used as the gold standard in this thesis. Performance tests were conducted by measuring sEMG signals on left and right suprahyoid muscles. Subjects were instructed to swallow 10 ml of water in one swallowing act, repeated 30 times for each system. The performances were evaluated in time and frequency domain. Signal-to-noise ratio (SNR) and contraction duration (DUR) were used as evaluation parameters in time domain, while mean and median frequency (MNF and MDF) were used in frequency domain. The developed system had a SNR value of 20.04 0.38 dB which was comparable with the SNR of gold standard at 20.22 0.38 dB. Both systems had DUR value of 0.97 0.09 s for the developed system and 0.91 0.02 s. Using paired t-test, there was no statistically significant difference between both DUR value (???? > 0.05). In frequency domain, the developed system had MNF and MDF value of 89.11 1.03 Hz and 76.89 1.18 Hz, while the gold standard had 105.75 0.88 Hz and 95.96 1.79 Hz. By comparing the power spectrum of both system statistically, there were a similarity in performance for both systems at 25–29 Hz, 42–77 Hz, 85–94 Hz, 115–124 Hz, 130–134 Hz, and 160–164 Hz (???? > 0.05). Overall, the developed system has a promising potential towards clinical application, especially in dysphagia evaluation. The open-source nature of the developed system and its modularity enhances the developed system’s potential to be integrated in various application. Keywords: dysphagia, sEMG, flexible electrode, impedance analysis, ESP-32.