Desenvolvimento e implementação de um sensor hibrido não invasivo de eletromiografia e mecanomiografia para registros de potenciais de ação de uma unidade motora

Abstract

More than 40 types of muscular dystrophy are currently known, which in 2003 had affected more than 80,000 brazilians. One type of medical test used as an aid in the diagnosis of these muscular dystrophies is the electroneuromyography, which aims to evaluate muscle electrical activity. To performance this test needle electrodes are used, which analyze the morphology of muscle fibers action potentials and their recruitment pattern. Despite the invasive nature of the used electrodes, methods such as surface electromyography have not been effective in individual action potentials records. Thus, this study proposed to develop a hybrid electromyography and mechanomyography sensor which records a motor unit action potential through noninvasive methods. So, the EMG sensors are built up of two electrolytes prepared using an alloy of silver-silver chloride, 99% purity, area of 1mm ² (1mm side) and the inter-electrode distance of 3mm. The electrode is active and the configuration used is bipolar, with gain of 20 times and CMRR exceed 120dB. The mechanomyography sensor has an accelerometry transducer, whose used chip was Freescale MMA7260. It features 800mV/g of sensitivity, noise level of 350μg/Hz½ and 350Hz frequency band. The tests performed show the efficiency of the developed sensor to record motor unit action potentials in low muscle activity levels and superficial muscles.