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Scientific Research

Introduction:

Bioelectric impedance measurements (BIM) represents a wide range of old and new non-invasive technologies and methods where a very small electric current is applied to the body via one or more surface electrode and the resultant current passing through the body is detected at other surface electrodes placed elsewhere on the body. A drop in voltage occurs as the current encounters impedance or resistance inherent in the fluids and tissues it passes through as it courses through the various physiological “compartments” of the body.1-3 These compartments include the bloodstream, the intracellular space, the lymphatic system, the interstitial space, and others.4,5 This drop in voltage provides indirect information about the physical and chemical properties of the compartment(s) that the current passed through.

Alternating Current Bioelectric Impedance Methods:

The most familiar form of BIM uses an alternating current (A.C.) system. There are dozens of readily available commercial and custom-built A.C. BIM systems differing widely in design and complexity.6 Most systems are used to indirectly estimate the fat content of the body by measuring total body water.7,8 These systems typically employ A.C. electricity with a wide range of currents, frequencies, and voltage. The amount of electricity delivered to the body is usually imperceptible and far below the level that would cause cellular or tissue damage.9,10 Studies of A.C. BIM systems operating at 50 MHz or higher, have revealed that these high frequency A.C. electric currents flow non-selectively through both intracellular and extra cellular spaces11 (see image below), and thus provide relatively non-specific information regarding the physical properties and chemical composition of total body water.

Bioelectric Impedance Analysis in Cardiology and Oncology

Direct Current Bioelectric Impedance Methods: Unlike A.C. bioelectric impedance, the electric current produced by D.C. bioelectric impedance methods specifically passes through the interstitial fluid compartment 23 (see image below). The interstitial fluid compartment represents approximately 16% of the body’s total water.24-26 Interstitial fluid is extra cellular water and solutes surrounding cells, but outside of the bloodstream and lymphatic system. Interstitial fluid forms the microscopic interface between cells and capillaries. Interstitial fluid differs from whole blood by the absence of red blood cells, and it differs from blood plasma in that there are far fewer proteins. Any substance passing between cells and the bloodstream must traverse the interstitial space. These substances include oxygen, carbon dioxide, glucose, as well as thousands of other compounds.27,28 The interstitial fluid’s role as a metabolic conduit and its proximity to the collective intracellular space of nearby cells suggests that the chemical composition of the interstitial fluid may reflect the physiology (or pathophysiology) of nearby cells.29-31 Since D.C. electric current primarily passes through the interstitial fluid, it has been proposed that an abnormality in the chemical composition of the interstitial fluid could be detected with an adequately sensitive D.C. BIM device.

D.C. Bioelectric Impedance Device : EIS System

The EIS system is the only commercially available BIM system utilizing direct current (D.C.) technology (patent N°06/09878) The device uses a PC to control, coordinate, and direct a specific pre-programmed sequence of brief, barely perceptible D.C. current pulses (microampere strength) through an array of 6 symmetrically placed surface electrodes: left and right forehead, left and right hands (palms), and left and right feet (soles). This 6-electrode array forms 22 electrode pairs, or “volumes” .
The D.C. current passes through the interstitial space in the body and voltage is measured at the other 6 electrodes. The change in voltage/impedance between the anode and cathode reflects some aspect of the physical and chemical properties of the interstitial fluid space. The spatial array of the electrodes also provides some degree of anatomical localization.

The Pre-Programmed Sequence of Electrode Pairs

	Anode	Cathode
2.	L hand	L forehead
10.	R forehead	L forehead
4.	R hand	R forehead
11.	L hand	R hand
6.	L foot	L hand
14.	R foot	L foot
7.	R hand	R foot
16.	L forehead	R hand
17.	L hand	R forehead
19.	R foot	L hand
22	R hand	L foot
1.	L forehead	L hand
9.	L forehead	R forehead
3.	R forehead	R hand
12	R hand	L hand
5.	L hand	L foot
13.	L foot	R foot
8.	R foot	R hand
15.	R hand	L forehead
18.	R forehead	L hand
20.	L hand	R foot
21.	L foot	R hand

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