Bio-impedance signal decomposer: enhanced accuracy and reduced latency solution; pp. 201–219Full article in PDF format
| doi: 10.3176/eng.2011.3.03
The paper presents an overview of the electrical bio-impedance (EBI) signal decomposition into its cardiac and respiratory components. This problem mainly originates from the nonstationarity of the signal components and overlapping of their harmonic spectra. In the introductory part of the paper, an overview of the bio-impedance signal decomposer (BISD), as a solution of the problem, is accompanied with an introduction to a cardiac BI signal model, which is constructed from the components of the application-specific orthonormal basis. In the main part of the paper a semi-synchronous cardiac signal amplitude estimator, which is based on the cardiac signal model and on the proposed extrema searching algorithm, is proposed. After that, the cardiac signal lock-in detection algorithm is proposed. Finally, a conditioning of the estimated cardiac signal frequency is discussed. The proposed amplitude estimator, lock-in detector and frequency conditioning increase twice the reaction speed of the BISD to the input EBI signal. The proposed version of the BISD estimates the cardiac signal amplitude during only a few cardiac periods, even if very large difference between amplitudes exists in different conditions. As a result, the entire BISD becomes locked during 8 s (including 4 s of soft start). The proposed improvements allowed reducing the latency of the BISD from 2 to 1 s.
1. Atzler, E. and Lehmann, G. Über ein neues Verfahren zur Darstellung der Herztätigkeit (Dielektrographie). Arbeitsphysiol, 1932, 6, 636–680.
2. Nyboer, J., Bagno, S., Barmett, A. and Halsey, R. H. Radiocardiograms: electrical impedance changes in heart in relation to electrocardiograms and heart sounds. J. Clin. Invest., 1940, 19, 963.
3. Zlochiver, S., Freimark, D., Arad, M., Adunsky, A. and Abboud, S. Parametric EIT for monitoring cardiac stroke volume. J. Physiol. Meas., 2006, 27, S139–S146.
4. Newman, D. G. and Callister, R. The non-invasive assessment of stroke volume and cardiac output by impedance cardiography: a review. Aviat. Space Environ. Med., 1999, 70, 780–789.
5. Cotter, G., Schachner, A., Sasson, L., Dekel, D. and Moshkovitz, Y. Impedance cardiology revisited. J. Physiol. Meas., 2006, 27, 817–827.
6. Mond, H. L., Stratmore, N., Kertes, P., Hunt, D. and Baker, G. Rate responsive pacing using a minute ventilation sensor. Pace, 1988, 11(suppl. II), 1866–1874.
7. West, J. B. Respiratory Physiology: The Essentials. Mir, Moscow, 1988 (in Russian).
8. Dell’Orto, S., Valli, P. and Greco, M. E. Sensors for rate adaptive pacing. Indian Pacing and Electrophysiology J., 2004, 4, 137–145.
9. Min, M., Parve, T. and Kink, A. Thoracic bioimpedance as a basis for pacing control. In Electrical Bioimpedance Methods: Applications to Medicine and Biotechnology. Annals of the NY Acad. Sci., 1999, 873, 155–166.
10. Webster, J. G. Design of Cardiac Pacemakers. IEEE Press, NJ, 1995.
11. Muzi, M., Jeutter, D. C. and Smith, J. J. Computer-automated impedance-derived cardiac indexes. IEEE Trans. Biomed. Eng., 1986, 33, 42–47.
12. Wang, X., Sun, H. H. and Van De Water, J. M. An advanced signal processing technique for impedance cardiography. IEEE Trans. Biomed. Eng., 1995, 42, 224–230.
13. Zhang, Y., Qu, M., Webster, J. G., Tompkins, W. J., Ward, B. A. and Bassett, D. R. Cardiac output monitoring by impedance cardiography during treadmill exercise. IEEE Trans. Biomed. Eng., 1986, 33, 1037–1042.
14. Woltjer, H. H., Bogaard, H. J. and M. de Vries, P. M. J. The intra- and interobserver variability of impedance cardiography in patients at rest and during exercise. J. Physiol. Meas., 1996, 17, 171–178.
15. Kim, D. W., Song, C. G. and Lee, M. H. A new ensemble averaging technique in impedance cardiography for estimation of stroke volume during treadmill exercise. Frontiers Med. Biol. Eng., 1992, 4, 179–188.
16. Hu, W., Sun, H. H. and Wang, X. A study on methods for impedance cardiography. In Proc. 19th International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE/EMBS 97. Chicago, IL, USA, 1997, 2074–2077.
17. Yamamoto, Y., Mokushi, K., Tamura, S., Mutoh, Y., Miyashita, M. and Hamamoto, H. Design and implementation of a digital filter for beat-by-beat impedance cardiography. IEEE Trans. Biomed. Eng., 1988, 35, 1086–1090.
18. Chen, J. Z., Lin, Z. and McCallum, R. W. Cancelation of motion artefacts in electrogastrogram – a comparison of time-, transform- and frequency-domain adaptive ﬁltering. In Proc. IEEE SoutheastCon 1993. Charlotte, NC, USA, 1993, 7.
19. Pandy, V. K. and Pandey, P. C. Cancellation of respiratory artifact in impedance cardiography. In Proc. 27th Annual Conference on Engineering in Medicine and Biology. Shanghai, China, 2005, 5503–5506.
20. Barros, A. K., Yoshizawa, M. and Yasuda, Y. Filtering noncorrelated noise in impedance cardiography. IEEE Trans. Biomed. Eng., 1995, 42, 324–327.
21. Ouyang, J., Gao, X. and Zhang, Y. Wavelet-based method for reducing respiratory interference in thoracic electrical bioimpedance. In Proc. 20th Annual International Conference of IEEE Engineering in Medicine and Biology Society, 1998, 20, 1446–1449.
22. Pandy, V. K. and Pandey, P. C. Wavelet based cancellation of respiratory artifacts in impedance cardiography. In Proc. 15th International Conference on Digital Signal Processing. Cardiff, UK, 2007, 191–194.
23. Krivoshei, A. Decomposition of the Electrical Bio-impedance Signal: A Signal Model Based Method for Separation of the Cardiac and Respiratory Components. LAMBERT Acad. Publ., Saarbrücken, 2010.
24. Krivoshei, A., Min, M., Parve, T. and Ronk, A. An adaptive filtering system for separation of cardiac and respiratory components of bioimpedance signal. In Proc. International Workshop on Medical Measurements and Applications. Benevento, Italy, 2006, 10–15.
25. Krivoshei, A., Min, M. and Kukk, V. Signal-shape locked loop (SSLL) as an adaptive separator of cardiac and respiratory components of bio-impedance signal. In Proc. International Workshop on Medical Measurements and Applications. Warsaw, Poland, 2007, 47–52.
26. Krivoshei, A., Kukk, V. and Min, M. An adaptively tunable model of the cardiac signal for the bio-impedance signal decomposer (BISD). In Proc. International Workshop on Medical Measurements and Applications. Ottawa, Canada, 2008, 49–52.
27. Krivoshei, A., Kukk, V. and Min, M. Decomposition method of electrical bio-impedance signal into cardiac and respiratory components. J. Physiol. Meas.
, 2008, 29
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