A Low-Cost, Low-Power Flexible Single-Lead ECG Textile Sensor for Continuous Monitoring of Cardiac Signals
N. Sriraam, Avvaru Srinivasulu, V. S. Prakash
Abstract
Wearable continuous monitoring systems (WCMSs) ensure remote monitoring of vital signs of the human day-to-day routine to assess the level of criticality. The use of dry textile electrodes further increases the comfortness and flexibility of WCMS, and its ultralow power technology with miniaturized sensors reduces the overall manufacturing cost. This research shows the performance evaluation of ultralow power flexible single-lead silver-plated nylon woven (Ag-NyW) dry ECG sensors. The system was assessed in terms of reusability, wet, wash, treadmill, and activity tests. A total of 144 healthy volunteers participated in this study. It was observed that the regular use of dry textile electrodes increases the skin–electrode contact impedance over a period of three months. Furthermore, after rinsing the textile electrode with the salt water, saline solution, and normal water separately, its impedance was found to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${22}.{4}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${7}.{99} \text {k}\Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${734}.{6} \Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{55} \text {k}\Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{95}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{87} \text {k}\Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> , respectively, which were found significantly less compared with that of the dry condition ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${68}.{36}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${5}.{18} \text {k}\Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> ) in the frequency range of 4–100 Hz. Though incremental impedance was observed after four to five wash cycles, the results were within the limits ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ < {5} \text {M}\Omega /\text {Cm}^{{2}}$ </tex-math></inline-formula> ). The fiducial points of the proposed system during the treadmill tests were found to be matched with single-lead ActiWave Cardio system. The resultant fiducial points from the designed system for various activities were found to be within the normal range. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> -peak detection sensitivity of signal acquired from males and females during different activities was >95%. Furthermore, the proposed system consumes a low power of 330 mW with 3.3-V Li-Po batteries.