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Smartware electrodes for ECG measurements: Design, evaluation and signal processing
Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-100134DOI: 10.3384/diss.diva-100134ISBN: 978-91-7519-507-0 (print)OAI: oai:DiVA.org:liu-100134DiVA: diva2:660168
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
List of papers
1. Electrical characteristics of conductive yarns and textile electrodes for medical applications
Open this publication in new window or tab >>Electrical characteristics of conductive yarns and textile electrodes for medical applications
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2007 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 12, 1251-1257 p.Article in journal (Refereed) Published
Abstract [en]

Clothing with conductive textiles for health care applications has in the last decade been of an upcoming research interest. An advantage with the technique is its suitability in distributed and home health care. The present study investigates the electrical properties of conductive yarns and textile electrodes in contact with human skin, thus representing a real ECG-registration situation. The yarn measurements showed a pure resistive characteristic proportional to the length. The electrodes made of pure stainless steel (electrode A) and 20% stainless steel/80% polyester (electrode B) showed acceptable stability of electrode potentials, the stability of A was better than that of B. The electrode made of silver plated copper (electrode C) was less stable. The electrode impedance was lower for electrodes A and B than that for electrode C. From an electrical properties point of view we recommend to use electrodes of type A to be used in intelligent textile medical applications. © International Federation for Medical and Biological Engineering 2007.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-40953 (URN)10.1007/s11517-007-0266-y (DOI)54747 (Local ID)54747 (Archive number)54747 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
2. Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
Open this publication in new window or tab >>Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
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2013 (English)In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12Article in journal (Refereed) Published
Abstract [en]

Background

ECG (Electrocardiogram) measurements in home health care demands new sensor solutions. In this study, six different configurations of screen printed conductive ink electrodes have been evaluated with respect to electrode potential variations and electrode impedance.

Methods

The electrode surfaces consisted of a Ag/AgCl-based ink with a conduction line of carbon or Ag-based ink underneath. On top, a lacquer layer was used to define the electrode area and to cover the conduction lines. Measurements were performed under well-defined electro-chemical conditions in a physiologic saline solution.

Results

The results showed that all printed electrodes were stable and have a very small potential drift (less than 3 mV/30 min). The contribution to the total impedance was 2% of the set maximal allowed impedance (maximally 1 kΩ at 50 Hz), assuming common values of input impedance and common mode rejection ratio of a regular amplifier.

Conclusion

Our conclusions are that the tested electrodes show satisfying properties to be used as elements in a skin electrode design that could be suitable for further investigations by applying the electrodes on the skin.

Keyword
Screen printed electrodes, ECG, Electrode impedance, Electrode potential, Smartware electrodes
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96422 (URN)10.1186/1475-925X-12-64 (DOI)000321916300001 ()
Note

Funding Agencies|VINNOVA - Swedens Innovation Agency||NovaMedTech||Linkoping Initiative for Life Science Technologies (LIST)||

Available from: 2013-08-20 Created: 2013-08-19 Last updated: 2017-12-06
3. A Canonical correlation approach to heart beat detection in textile ECG measurements
Open this publication in new window or tab >>A Canonical correlation approach to heart beat detection in textile ECG measurements
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2006 (English)In: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, 1-4 p.Conference paper, Published paper (Refereed)
Abstract [en]

Research in textile sensors has lead to new ways to measure electrocardiograms (ECG). However, additional disturbances from e.g. muscular noise and high skin-electrode impedances often result in poor signal quality. The paper contains a simple 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 intend to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to simple averaging of the ECG channels and to the independent component analysis method (ICA). A heart beat detector was used to evaluate the signal quality. Results show that the signal was completely lost while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

Place, publisher, year, edition, pages
IEEE, 2006
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-34459 (URN)21497 (Local ID)08-6341-658-6 (e-book) (ISBN)978-08-6341-658-3 (ISBN)21497 (Archive number)21497 (OAI)
Conference
3rd International Conference on Advances in Medical Signal and Information Processing : MEDSIP 2006, July 17-19, 2006, Glasgow, Scotland
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2015-03-20Bibliographically approved
4. Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
Open this publication in new window or tab >>Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
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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
Keyword
textile electrodes, multichannel ecg, noise suppression, heartbeat detector
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-79772 (URN)10.4018/jehmc.2013010106 (DOI)
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

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