Motion Artifacts in Capacitive ECG Measurements: Reducing the Combined Effect of DC Voltages and Capacitance Changes Using an Injection Signal

Abstract

Link to publication Citation for published version (APA):Serteyn, A. A. M., Vullings, R., Meftah, M., & Bergmans, J. W. M. (2015). Motion artifacts in capacitive ECG measurements : reducing the combined effect of DC voltages and capacitance changes using an injection signal. IEEE Transactions on Biomedical Engineering, 62(1), 264-273. DOI: 10.1109/TBME.2014.2348178 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract-Capacitive electrodes are a promising alternative to the conventional adhesive electrodes for ECG measurements. They provide more comfort to the patient when integrated in everyday objects (e.g., beds or seats) for long-term monitoring. However, the application of capacitive sensors is limited by their high sensitivity to motion artifacts. For example, motion at the body-electrode interface causes variations of the coupling capacitance which, in the presence of a dc voltage across the coupling capacitor, create strong artifacts in the measurements. The origin, relevance, and reduction of this specific and important type of artifacts are studied here. An injection signal is exploited to track the variations of the coupling capacitance in real time. This information is then used by an identification scheme to estimate the artifacts and subtract them from the measurements. The method was evaluated in simulations, lab environments, and in a real-life recording on an adult's chest. For the type of artifact under study, a strong artifact reduction ranging from 40 dB for simulated data to 9 dB for a given reallife recording was achieved. The proposed method is automated, does not require any knowledge about the measurement system parameters, and provides an online estimate for the dc voltage across the coupling capacitor.

Sensitivity analysis of Heuer's method for motion-artifacts reduction in capacitive biopotential measurements

“…Estimation of the additive MA by approximating the dynamic highpass filter with a LTI high-pass filter [6]. Two inputs denoted by solid arrows are time-variant, the other two denoted by hollow arrows are time-invariant.…”

“…1(b), six parameters were needed to generate V o (t). The settings of these parameters (Table I) were in line with those in [6]. The biopotential signal was an ECG constructed by concatenating identical heart beats.…”

“…This signal could be captured by e.g. accelerators [5], or an injection signal [6]. K Other methods include those based on the wavelet [7] or a reconstruction equation [8].…”

“…Among these methods, the two proposed by Heuer et al [8] and Serteyn et al [6] analyzed the time-domain behavior of the measurement system. This provides a new insight into the MA (i.e.…”

Correction of the Unobtrusive ECG Using System Identification

“…For the cECG in particular, several hardware-based approaches have been proposed to improve the quality, but they have also increased the complexity of the circuits [14][15][16]. Furthermore, the morphology of the cECG differs slightly from that of the standard ECG, which is important…”