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EIS White paper

The EIS is a programmable electro medical system (PEMS) including: -
USB plug and play hardware devices including interface box  , disposable electrodes, reusable plates  and reusable cables
- Software installed on a computer.
The EIS (Electro Interstitial Scan) provides a signal corresponding to the status of a patient's physiological parameters.
The signal processing analysis displays the following parameters of the living tissue: 
- SDC and ESG HF, ESG LF and ESG VLF , according to the Electrical conductance analysis -
- EPA –SPA according to the Electrical dispersion analysis
The device is using the Bioimpedance technology in bipolar mode with a very low frequency.

EIS Features' diagram:

Figure 1

Comments of the EIS Signal processing Analysis
1. Measurement of 22 segments of the human body in bipolar mode
2. Sequence of measurement
3. Site of investigation according to the used frequency of 700 Hz: extracellular space.
4. Original signal transmitted to the software
5.ESG graph: real conductivity of the 22 measured segments
6. Calculation of the value A1 (mathematical average of the 22 segments’ value)
7. Second derivative ESG from the ESG graph and value A1 and calculation of the parameter SDC related to electrical conductance and the segmental interstitial fluid sodium concentration and segmental ATP pump activity.
8.  Dynamic processing analysis and calculation of the parameter EPA-SPA related the electrical distribution and to the parameter alpha of the Cole equation. This parameter is related to the interstitial fluid space morphology.
9.  Spectral analysis of the original signal (Discrete Fourier transformation) and calculation of the parameter ESG HF, ESG LF and ESG VLF related to the general interstitial fluid sodium concentration and general ATP pump activity.
10.  Cross Analysis of the segmental parameters SDC, EPA-SPA and general parameters HF/LF and VLF in order to estimate the living tissue state (hypoxia, ischemia/hypoxia and inflammatory process).

II.EIS process analysis description
A weak current with a very low frequency (700 Hz) is applied between six electrodes placed symmetrically on the forehead, hands, and feet of the study subject. Each electrode is alternatively cathode and anode (bipolar mode), which permits the electrical conductivity and the electrical dispersion records of 22 segments from the human body (Law of Ohm) and α parameter of the Cole equation (1) (2) (3) (4)).
Measurement sequence according to the Figure 1
12 segments are related to the body (5/6/7/8/11/12/13/14/19/20/21/22)
10 segments are related to the brain (1/2/3/4/9/10/15/16/17/18).

Figure 2

Real time Signals :

Each segment is measuring in one second, 32 times (with a start point SPA and end point EPA). Therefore, the total data is 704 pulses per measurements. The measured resistances are transmitted with a numeric form for each segment, to an informative program.

The measured parameters are transmitted with a numeric form for each segment, to an informative program.
The electrical conductivity values of the 22 segments are incorporated in a Graph. The graph is called an Electro Scan Gram (E.S.G) (Figure 4).
The abscissa is corresponding to the electrical conductivity in numeric form in scale 0-100 (Conversion table in software features in m.S-1)
The ordinate is corresponding to the 22 measured segments of the human body

Figure 4

b. Second Derivative ESG (SDESG)

The ESG is converting to the SDESG graph (Fig.5).
The average of the 22 electrical conductivity values named point A, will be considered as point 0  and therefore the ESG graphic can be convert to second derivative ESG in scale
-100/+100. The delta of the numeric value of each segment to the value 0 is called SDC (Standard Deviation of the Conductivity) and can be positive or negative.
The abscissa is corresponding to the conductivity in numeric values with a scale -100/+100.
The ordinate is corresponding to the 22 measured segments of the human body

Each segment value is measured with 32 pulses. 
The value EPA (End Point Analysis) – SPA (Start Point Analysis) represents the dynamic process value of the signal and the electrical dispersion (closely related to α parameter of the Cole equation). (Fig.6)

The Spectrum analysis and the Application of the Discrete Fast Fourier Transform (3) to the entire records provide 3 components where:

• ESG HF (High frequencies from 0.1875 to 0.50Hz), are corresponding to the percent of the high conductivities of the entire records.
• ESG LF (Low frequencies from 0.05 to 0.1875 Hz), are corresponding to the percent of the low conductivities of the entire records.
• ESG VLF (Very Low frequencies from 0 to 0.05 Hz), are corresponding to the percentage of the very low conductivities of the entire records

ESG HF/VLF ratio is corresponding to the high conductivities / very low conductivities ratio.
The abscissa is corresponding to the DFT amplitude with a scale 0/100
The ordinate is corresponding to range of frequencies used in DFT (from 0 to 0.50Hz).

Figure 7

III. Summary of the peer reviews about the Bioimpedance technology and application to the EIS Technology.
1. Electrical Conductance of Living Tissue
a. At low frequencies, near DC, the cell membrane acts as an insulator and the current is not able to penetrate the cell, and most of the current flows around the cell. (12)
b. Considering the extremely low conductivity of the cell membrane, the value of the resistance R of the cell membraneis very high. (1) (12)
c. We can consider living tissue electrically and macroscopically as an ionic conductor. The total ionic conductivity of a solution depends on the concentration, activity, charge and mobility of all free ions in the solution. Ionic conductance is a transfer of charges accompanied by movement of a substance, producing changes in the bulk of the electrolyte. (11) (27)
2. Efflux of the Na+ and ATP production
The ATP production is engaged by the efflux of 3 Na+ ions and the influx of 2 K+ ions. (13)
Application to the EIS Technology (items 1 and 2)
The EIS Technology is using a very low frequency close to the DC, therefore:

1. The current flows around the cells very close to the cell membrane in the area of the interstitial fluid and does not penetrate the cell
2. The EIS measurements are in KOhms and the normal range average of the measured resistance is high , about 100 KOhms and the conductivity around 24 10-6 S.m-1.
3. The segmental and the percent of  high, low and very low conductivity are proportional to the interstitial fluid Na+ ions concentration (parameter SDC, ESG HF , ESGLF and ESG VLF) and according to the Na+/ K+ ATPase pump principle; the conductivity is proportional to the mitochondrial ATP production.

3. Electrical Dispersion and dielectric properties
Any material with the ability to store capacitive energy can be classified as a dielectric.
The cell membrane is the cellular structure has the main contribution to the dielectric behavior of living tissue. (5) (10)
Living tissue is considered as a dispersive medium (10): In the case of living tissues, the spectral width of the electrical Bioimpedance dispersions (related with α parameter in the Cole equation) is related with the morphology of the extracellular spaces. (20)

Application to the EIS Technology (items 3)
The electrical Bioimpedance dispersions (parameter EPA-SPA of the ESG table closely related with α parameter in the Cole equation) is related with the morphology of the extra-cellular spaces.

REFERENCES

1. Schwan, H. P. (1957). Electrical properties of tissue and cell suspensions. Adv Biol. Med Phys, 5, 147-209.
2. Schwan, H. P. (1963). Determination of Biological Impedances. In W. L. Nasduk (Ed.), Physical Techniques in Biological Research (Vol. VI, pp. 323- 407). New York: Academic Press.
3. Schwan, H. P. (1994). Electrical properties of tissues and cell suspensions: mechanisms and models. Paper presented at the Proceedings of 16th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Baltimore, MD, USA.
4. S. Gabriel, R. W. Lau, and C. Gabriel, "The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues," Physics in Medicine and Biology, pp. 2271-2293, 1996.
5. C. Gabriel, S. Gabriel, and E. Corthout, "The dielectric properties of biological tissues: I. Literature survey," Physics in Medicine and Biology, pp. 2231-2249, 1996.
6. Schwan, H. P. & Takashima, S. (1993). Electrical conduction and dielectric behavior in biological systems. In G. L. Trigg (Ed.), Encyclopedia of Applied Physics (Vol. Biophysics and Medical Physics). New York and Weinheim: VCH publishers.
7. Seoane, F., Lindecrantz, K., Olsson, T. & Kjellmer, I. (2004). Bioelectrical impedance during hypoxic cell swelling: Modeling of tissue as a suspension of cells. Paper presented at the Conference Proceedings - XII International Conference Electrical Bioimpedance, Jun 20-24 2004, Gdansk, Poland.
8. Seoane, F., Lindecrantz, K., Olsson, T., Kjellmer, I., Flisberg, A. & Bagenholm, R. (2004b). Brain electrical impedance at various frequencies: The effect of hypoxia. Paper presented at the 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2004, Sep 1-5 2004, San Francisco, CA.
9. Seoane, F., Lindecrantz, K., Olsson, T., Kjellmer, I., Flisberg, A. &
Bagenholm, R. (2005). Spectroscopy study of the dynamics of the transencephalic electrical impedance in the perinatal brain during hypoxia. Physiological Measurement, 26 :(5), 849-863.
10. Foster, K. R. & Schwan, H. P. (1989). Dielectric Properties of Tissues and Biological Materials: A Critical Review. CRC Critical Reviews in Biomedical Engineering, 17:(1), 25-104.
11. Grimmes, S. & Martinsen, Ø. G. (2000). Electrolytics. In Bioimpedance & Bioelectricity Basics: Academic Press.
12. J. R. Bourne, "Bioelectrical impedance techniques in medicine," in Crit. Rev. Biomed. Eng. vol. 24, 1996, p. 680.
13. Guyton, A. C. & Hall, J. E. (2001). Textbook of Medical Physiology (10th ed.). Philadelphia: W.B.Saunders Company.
14. Hansen, A. J. (1984). Ion and membrane changes in the brain during anoxia. Behavioral Brain Research, 14 :(2), 93-98.
15. Hansen, A. J. (1985). Effect of anoxia on ion distribution in the brain. Physiol. Rev., 65:(1), 101-148.
16. Cole, K. S. (1928). Electric impedance of suspensions of spheres. Journal of General Physiology, 12, 29-36.
17. Cole, K. S. (1932). Electric phase angle of cell membranes. Journal of General Physiology, 15, 641-649.
18. Cole, K. S., Li, C. L. & Bak, A. F. (1969). Electrical analogues for tissues. Exp Neurol, 24 :(3), 459-473.
19. K. S. Cole and R. H. Cole, "Dispersion and absorption in dielectrics. I. Alternating-current characteristics," Journal of Chemical Physics, vol. 9, pp. 341-51, 1941.
20. Antoni Ivorra, Meritxell, Genesca, Anna Sola, Luis Palacios, Rosa Villa, Georgina Hotter and Jordi Aguilo: Bioimpedance dispersion width as a parameter to monitor living tissues Physiol. Meas. 26 (2005) 1–9
21. Peyman Mirtaheri*, Sverre Grimnes, and Orjan G. Martinsen, Member, IEEE. Electrode Polarization Impedance in Weak NaCl Aqueous Solutions. IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 52, NO. 12, DECEMBER 2005
22. Kumar, V. (2005). Cellular Adaptations, Cell Injury, and Cell Death. In S. L.
23. Olsson, T., Broberg, M., et al. (2006). Cell swelling, seizures and spreading depression: An impedance study. Neuroscience, 140:(2), 505-515.
24. Pethig, R. & Kell, B. D. (1987). The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology. Physics in medicine and biology, 32:(8), 933-970.
25. Ischemia and Hypoxia. Journal of Theoretical Biology, 220 :(1), 83-106. Ackmann J J and Seitz MA 1984 Methods of complex impedance measurements in biologic tissue Crit. Rev. Biomed. Eng. 11 281–311
26. Foster K R and Schwan H P 1989 Dielectric properties of tissues and biological materials: a critical review CRC Crit. Rev. Biomed. Eng. 17 25–104
27. Grimnes S and Martinsen Ø G 2000 Bioimpedance and Bioelectricity Basics (London: Academic)
28. Haemmerich D, Ozkan O R, Tsai J Z, Staelin S T, Tungjitkusolmun S, Mahvi D M and Webster J G 2002 Changes in electrical resistivity of swine liver after occlusion and postmortem Med. Biol. Eng. Comput. 40 29–33
29. Raicu V, Saibara T, Enzan H and Irimajiri A 1998 Dielectric properties of rat liver in vivo: analysis by modeling hepatocytes in the tissue architecture Bioelectrochem. Bioenerg. 47 333–42
30. Raicu V, Saibara T and Irimajiri A 2000 Multifrequency method for dielectric monitoring of cold-preserved organs Phys. Med. Biol. 45 1397–407
31. Schwan H P 1957 Electrical properties of tissue and cell suspensions Advances in Biological and Medical Physics vol. 5 ed J H Lawrence and C A Tobias (New York: Academic)
32. Walker D C, Brown B H, Hose D R and Smallwood R H 2000 Modeling the electrical impedivity of normal and premalignant cervical tissue Electron. Lett. 36 1603–4
33. H. P. Schwan, "The Practical Success of Impedance Techniques from an Historical Perspective," Ann N Y Acad Sci, vol. 873 pp. 1-12, 1999.
34. . V. G. Alexeev , L. V. Kuznekova: EIS System (Galvanic Skin responses measurement device) in adjunct to Treatments’ monitoring .Final Report 09.25.2009
35. John E. Lewis, Angelica B. Melillo, Evan Long, Yaima Alonso, Elizabeth Ko,Soyona Rafatjah, Janet Konefal, and Judi M. Woolger. Comparing theAccuracy of the Electro Interstitial Scan-Body Composition (EIS-BC) Device between a BC Module and a Valid Assessment of BC and between an EIS Module and a Standard Assessment of Heart Rate Variability. Final Report 01.12.2010