Proceedings of the 2005 IEEE Engineering in Medicine and Biology 27th Annual Conference Shanghai, China, September 1-4, 2005
MagIC System: a New Textile-Based Wearable Device for Biological Signal Monitoring. Applicability in Daily Life and Clinical Setting Marco Di Rienzo, Member IEEE, Francesco Rizzo, Gianfranco Parati, Gabriella Brambilla, Maurizio Ferratini and Paolo Castiglioni
Abstract— The paper presents a new textile-based wearable system for the unobtrusive recording of cardiorespiratory and motion signals during spontaneous behavior along with the first results concerning the application of this device in daily life and in a clinical environment. The system, called MagIC (Maglietta Interattiva Computerizzata), is composed of a vest, including textile sensors for detecting ECG and respiratory activity, and a portable electronic board for motion detection, signal preprocessing and wireless data transmission to a remote monitoring station. The MagIC system has been tested in freely moving subjects at work, at home, while driving and cycling and in microgravity condition during a parabolic flight. Applicability of the system in cardiac in-patients is now under evaluation. Preliminary data derived from recordings performed on patients in bed and during physical exercise showed 1) good signal quality over most of the monitoring periods, 2) a correct identification of arrhythmic events, and 3) a correct estimation of the average beat-by-beat heart rate. These positive results supports further developments of the MagIC system, aimed at tuning this approach for a routine use in clinical practice and in daily life.
I. INTRODUCTION
M
UCH effort is currently devoted to design smart wearable devices capable to detect vital signs while the subject is at work, during sport activities, at home or in a clinical environment without interfering with his/her spontaneous behavior nor limiting his/her comfort. Addressing this issue, however, implies to cope with major problems related to the design of new sensors, handling of possible noisy data, reduction in size, power consumption and costs of the new systems. A significant step forward in this area dates back to 1996 when at the MIT, researchers foresaw the development of garments capable to provide an
M. Di Rienzo (corresponding author), F. Rizzo and P. Castiglioni are with the Centro di Bioingegneria, Fondazione Don Carlo Gnocchi ONLUS, Via Capecelatro 66, 20148 Milano, Italy (Phone: +39-02-40308305; fax: +39-02-4048919; e-mail:
[email protected] ,
[email protected],
[email protected] ). G. Parati is with the Department of Clinical Medicine, Prevention and Applied Biotechnology, University of Milan-Bicocca - Cardiology II S. Luca Hospital, Istituto Auxologico Italiano, 20149 Milano, Italy (e-mail:
[email protected]). M Ferratini and G Brambilla are with the Cardiovascular Rehabilitative Unit of Santa Maria Nascente Center IRCCS, Fondazione Don Carlo Gnocchi ONLUS, 20148 Milano (Italy) (e-mail:
[email protected] [email protected] ).
0-7803-8740-6/05/$20.00 ©2005 IEEE.
unobtrusive monitoring of biological signals through textile sensors [1]. Since then, several research groups in the world [2, 3, 4], including our technological laboratory, have been working in the attempt to translate this innovative concept into a real device. The prototype of our wearable system for the unobtrusive recording of cardiorespiratory and motion signals during spontaneous behavior, is now available. In this paper the main features of the new device, called MagIC (Maglietta Interattiva Computerizzata) System, are presented along with the first results concerning its application in daily life and in a clinical environment. II. SYSTEM DESCRIPTION The MagIC System is composed of a sensorized vest and a portable electronic board (see fig.1). The vest is mainly made of cotton and lycra and is fully washable. At the thorax level the vest includes two woven electrodes made by conductive fibers so to obtain an ECG lead. The contact between textile electrodes and the thorax is guaranteed by the elastic properties of the garment, without requiring application of gel or of any other medium. The vest also includes a textile-based transducer for measurement of respiratory frequency through the assessment of the changes in the thorax volume. Via connections made of conductive fibers, ECG and respiratory signals fed an electronic board (having the size of a small cell phone) placed on the vest through a velcro strip. The electronic board detects also the subject’s movement through a 2-axis accelerometer and transmits all signals via a wireless connection to a remote computer which visualize and store data on disk.
Fig.1- The MagIC System. In the inset a detail of the textile electrode
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An example of output obtained by the system is shown in fig.2.
Fig.2 – Typical output available from the MagIC System III. APPLICATIONS So far the system has been tested in freely moving subjects at work, at home, while driving, during incremental exercise at the cycloergometer (i.e. while pedalling with a workload that progressively increases until volitional exhaustion or until a certain fraction of the subject’s maximal heart rate is reached), and in microgravity condition during a parabolic flight. Fig.3 shows the tachograms simultaneously obtained from the MagIC System and a traditional ECG recorder (Cardioline Delta1 Plus, REMCO Italia, S. Pedrino di Vignate, Italy) in one subject during the incremental exercise test. The close similarity between the two profiles indicates a correct estimation of RR interval from the MagIC System also during exercise.
The system has been also used in the frame of a more complex experiment to evaluate the cardiovascular steady state from the analysis of beat-by-beat RRI during and after the incremental exercise test [5]. Applicability of the MagIC System in a clinical setting is now under investigation. Indeed, a specific study is in progress to validate the use of the system on cardiac inpatients within the Cardiac Rehabilitation Unit of Fondazione Don Gnocchi. In the first part of the study we are focusing on the capability of the system to identify the features of cardiac rhythm and the occurrence of arrhythmic events while the subject is in the bed and while is performing a physical exercise on a cycloergometer as part of his/her rehabilitation program. Data so far collected from simultaneous ECG recordings obtained by our system and a traditional ECG recorder (Cardioline Delta 1 Plus) showed that MagIC provided readable signals for more than 99% and 95% of the time while the subjects where lying supine and on the cycloergometer respectively; in all instances the recorded signal allowed the identification of all the arrhythmic events and a correct estimation of the average beat-by-beat heart rate. Fig.4 illustrates two segments of ECG signal simultaneously recorded by the MagIC System and the traditional ECG recorder during the above validation study.
Fig. 4 – Comparison of ECG complexes simultaneously recorded by the MagIC System and the traditional ECG recorder.
IV. CONCLUSIONS Fig. 3 – Tachograms simultaneously recorded in one subject during incremental exercise test. Upper panel: RRI profile derived from the MagIC System. Lower panel: RRI profile from traditional ECG recorder.
A new wearable device for the assessment of vital signs based on textile sensors has been developed and is currently under test. The first positive results obtained from the clinical application of the MagIC System on cardiac patients do encourage the further development and tuning of the
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system for a routine use in the clinical setting and in daily life conditions. From a methodological point of view, our results also indicate that textile technology may provide an effective contribution in designing innovative devices for the assessment of biological signals. ACKNOWLEDGMENT The Authors thank Prof. Giuseppe Andreoni and Dr. Luca Piccini (Dept. of Biomedical Engineering, Politecnico di Milano) for their contribution in the early stage of the system design. REFERENCES [1]
[2] [3] [4]
[5]
E. R. Post., M. Orth, ‘Smart Fabric, or “Wearable Clothing”’, Proc. of International Symposium on Wearable Computers. October 13 - 14, 1997. Cambridge, Massachusetts, p. 167-168G. SmartShirt™, Sensatex, USA. Available: www.sensatex.com. LifeShirt, VivoMetrics, USA. Available: www.vivometrics.com/site/index.html. Della Santa A, Mazzoldi A, De Rossi D. Dressware: wearable hardware. Mater Sci Eng 1999;C7:31–37. P Castiglioni, G Merati, M Di Rienzo. Identification of Steady States and Quantification of Transition Periods from Beat-by-Beat Cardiovascular Time Series: Application to Incremental Exercise Test, Proc. Computers in Cardiology, IEEE Computer Society, Chicago, USA, 2004.
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