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Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
Mälardalen University. (Intelligent sensor systems department)
Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
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2013 (English)In: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, no 1, 61-71 p.Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

The aim of this study was to develop and evaluate a robust heartbeat detector for noisy electrocardiograms (ECGs) recorded with textile electrodes. We suggest a method based on weighted correlation in a multi-channel ECG to obtain a heartbeat detector. Signals were acquired during rest and at movements which simulate every day activities. From each recording a segment corresponding to a heartbeat was extracted and correlated with the whole signal. From the correlation data, heartbeat candidates were derived and weighted based on their variance similarity with the heartbeat model and previous heartbeats. Finally, the outputs of each channel were added to create the global output. The output was compared to the Pan Tompkins heartbeat detector. Results are promising for recordings at rest (sensitivity = 0.97, positive predictive value (PPV) = 0.97). For static muscle tension in the torso the results were much higher than the reference method (sensitivity = 0.77, PPV = 0.85). Corresponding values for the reference method were sensitivity = 0.96 and PPV = 0.95 at rest and sensitivity = 0.52 and PPV = 0.75 during muscle tension.

Place, publisher, year, edition, pages
IGI Global, 2013. Vol. 4, no 1, 61-71 p.
Keyword [en]
textile electrodes, multichannel ecg, noise suppression, heartbeat detector
National Category
Other Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-79772DOI: 10.4018/jehmc.2013010106OAI: oai:DiVA.org:liu-79772DiVA: diva2:544312
Conference
8th International Conference on Wearable Micro and Nano Technologies for Personalized Health
Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2015-03-20
In thesis
1. Smartware electrodes for ECG measurements: Design, evaluation and signal processing
Open this publication in new window or tab >>Smartware electrodes for ECG measurements: Design, evaluation and signal processing
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis work has been to study textile and screen printed smartware electrodes for electrocardiographic (ECG) measurements both in terms of their electrode properties and possibility to further improve their robustness to movement induced noise by using signal processing. Smartware electrodes for ECG measurements have previously been used in various applications but basic electrical electrode properties have not sufficiently been looked into. Furthermore, we believe that there is a possibility to reduce disturbances in the smartware ECG by adding redundant sensors and applying sensor fusion signal processing.

Electrical properties of conductive textiles have been evaluated in terms of stability and electrode impedance. Three yarns and textile electrode surfaces were tested. The electrodes made from pure stainless steel and 50\% stainless steel/ 50\% polyester showed acceptable stability of electrode potentials. All electrode measurements were performed on skin.

Furthermore, we produced six screen printed electrodes and their electrical performance was investigated in an electrochemical cell. The tested inks contained carbon or silver particles in the conduction lines, and Ag/AgCl particles in the electrode surface. Results show that all electrodes were stable in time, with a maximum drift of a few mV during 30 minutes. The silver ink is superior to the carbon based in terms of electrode impedance at the higher frequencies.

To extract viable physiological information from noisy signals, canonical correlation analysis (CCA) was applied on multi-channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intended to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to averaging of the ECG channels and to the independent component analysis method (ICA). In the dataset consisting of noisy ECG recordings, the signal was uninterpretable in 7% after CCABSS. Corresponding values for averaging and ICA were 33% and 17%, respectively.

Smartware applications often include heartbeat detection while moving, a measurement situation which is prone to produce noise corrupted ECG signals. To compensate for this, we used an event detector based on a multi-channel input, a model of the event and weighted correlation. For measurements at rest and static muscle tension, the sensitivity of the event detector was 97% and 77% respectively. Corresponding values for the golden standard detector Pan-Tompkins were 96% and 52%, respectively.

 

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 91 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1546
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-100134 (URN)10.3384/diss.diva-100134 (DOI)978-91-7519-507-0 (ISBN)
Public defence
2013-12-13, Eken, Campus US, Linköpings universitet, Linköping, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2013-10-30 Created: 2013-10-29 Last updated: 2013-11-04Bibliographically approved
2. Textile electrodes for ECG measurements in distributed care, performance and applications
Open this publication in new window or tab >>Textile electrodes for ECG measurements in distributed care, performance and applications
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis work has been to explore textile electrodes for electrocardiographic (ECG) measurements both in terms of their electrode properties and possibility to further improve their robustness to noise with signal processing techniques. Previous research within the field has shown that acquisition of ECG is possible with textile electrodes, but little attention has been focused on how they function and especially if movements are included in the measurement protocol.

In a first study, the electrical properties of conductive textiles were evaluated in the same manner as conventional Ag/AgCl ECG electrodes. Three yarns and textile electrode surfaces were tested. The electrodes made from pure stainless steel (A) and 20% stainless steel/ 80% polyester (B) showed acceptable stability of electrode potentials. The electrode made from silver plated copper (C) was less robust. The best electrode impedance characteristic had Electrode A and hence from an electrical properties point of view we recommend electrodes of type A to be used for ECG measurements.

The second paper contains an application of canonical correlation analysis (CCA) on multi channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intended to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to averaging of the ECG channels and to the independent component analysis method (ICA). Results show a loss of the ECG signal while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

A drawback with the CCABSS approach is however that it produces many outputs and that information regarding the wanted feature to detect is not included in the analysis. In the third article, an event detector based on a multichannel input, a model of the event and weighted correlation was used instead. For measurements at rest and upper body rotation, the sensitivity was 100% and 99% respectively. Muscle tension and walking were the hardest to detect with a sensitivity of 88% and 91% respectively.

Place, publisher, year, edition, pages
Linköping: Department of Biomedical Engineering, Linköpings universitet, 2010. 43 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1429
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-115838 (URN)LiU-TEK-LIC-2009:37 (Local ID)978-91-7393-447-3 (ISBN)LiU-TEK-LIC-2009:37 (Archive number)LiU-TEK-LIC-2009:37 (OAI)
Supervisors
Available from: 2015-03-20 Created: 2015-03-20 Last updated: 2015-03-20Bibliographically approved

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Rattfält, LindaHult, PeterAsk, PerBorga, Magnus

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