ECG Analog Front-end Research Articles

Development of a Multi-Channel Wearable Heart Sound Visualization System.

A multi-channel wearable heart sound visualization system based on novel heart sound sensors for imaging cardiac acoustic maps was developed and designed. The cardiac acoustic map could be used to detect cardiac vibration and heart sound propagation. The visualization system acquired 72 heart sound signals and one ECG signal simultaneously using 72 heart sound sensors placed on the chest surface and one ECG analog front end. The novel heart sound sensors had the advantages of high signal quality, small size, and high sensitivity. Butterworth filtering and wavelet transform were used to reduce noise in the signals. The cardiac acoustic map was obtained based on the cubic spline interpolation of the heart sound signals. The results showed the heart sound signals on the chest surface could be detected and visualized by this system. The variations of heart sounds were clearly displayed. This study provided a way to select optimal position for auscultation of heart sounds. The visualization system could provide a technology for investigating the propagation of heart sound in the thoracic cavity.

Development of A Wearable and WBAN-Based Vital Signs Monitoring System for Low-cost Personal Healthcare in Qatar

Population aging is a worldwide phenomenon, but its impact on Qatar is unique. The proposed system aims at comprehensive and integrated vital signs (ECG, Saturation of Arterial Oxygen (SpO2), BP and Heart rate (HR)) monitoring using a wearable sensor platform without professional involvements or interfering the elderly's everyday activities. A novel wireless physiological sensor node with single highly-integrated board has been specifically designed and fabricated ( Fig.1(a) ). The new board comprises of a MCU, ECG analog front-end, LED driver and brightness adjustment circuit for photoplethysmograph (PPG) measurement, a CC2420 chip for wireless communication and a FTDI FT232RL chip for MCU programming and real-time debugging. A miniaturized wireless gateway was also designed ( Fig.1(b) ) to wirelessly receive the data from sensor node and further relay to the PC for ongoing research on ECG denoising and arrhythmia classification. A novel MEMS-based electrode has been designed and fabricated for ECG measurement as shown in Fig.2 . Compared with conventional ECG electrodes, micromachined electrode is more comfortable; no direct contact of gel with the human skin and imposes no side effects to human for continuous and long term measurement. A unique characteristic feature of the proposed electrode is that the microneedle array is made of heavily doped silicon, which is electrically conductive and eliminates the requirement to dope Ag/AgCl or metal layer on the microneedles for electric contact. The microneedles can directly pierce through the outer skin surface, lowering the electrode-skin-electrode impedance (ESEI) and eliminating the need for skin preparation which, is prerequisite for wet electrode. For long-term monitoring, mechanical failure of micro-needles may accidentally happen due to the axial loading during insertion process or transverse loading during the measurement. As a result, the broken silicon needles will become debris in the skin, which attracts healthy concern for the user. Therefore, critical buckling loads for fabricated micro-needle were investigated using both theoretical estimation and ANSYS simulation. The results show that the critical buckling load is much larger than theoretical insertion force thereby the buckling problem will not occur during the insertion process. This work is supported by Qatar National Research Funding (QNRF) under the grant NPRP 09-292-2-113.