Method and device for stable impedance plethysmography
First Claim
1. A method for monitoring the internal electrical impedance of a biological object, with compensation for skin-electrode resistance drift, during an extended monitoring period, comprising the steps of:
- (a) placing a first measurement electrode and a second measurement electrode on the biological object, said first measurement electrode and said second measurement electrode being part of a measurement circuit;
(b) placing a first reference electrode and a second reference electrode on the biological object, substantially adjacent to said first measurement electrode, said first measurement electrode and said first reference electrode being part of a first reference circuit, said first measurement electrode and said second reference electrode being part of a second reference circuit, said first reference electrode and said second reference electrode being part of a third reference circuit;
(c) at least once during the monitoring period;
(i) measuring a first electrical impedance of said measurement circuit;
(ii) measuring a second electrical impedance of said first reference circuit;
(iii) measuring a third electrical impedance of said second reference circuit; and
(iv) measuring a fourth electrical impedance of said third reference circuit.
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Accused Products
Abstract
A method and device for impedance plethysmography, with relative immunity to skin-electrode contact resistance drift are provided. The method comprises: (a) placing: (i) first and second measurement electrodes on a biological object; (ii) first and second reference electrodes on opposite sides of the first measurement electrode; and (iii) third and fourth reference electrodes on opposite sides of the second measurement electrode, so as to define a measurement electrical circuit and six reference electrical circuits; (b) measuring: (i) a first electrical impedance of the measurement circuit; (ii) a second, third and fourth electrical impedances of three reference circuits which include the first measurement electrode, the first reference electrode and the second reference electrode; (iii) a fifth, sixth and seventh electrical impedances of three reference circuits which include the second measurement electrode, the third reference electrode and the fourth reference electrode; (c) calculating: (i) the skin-electrode resistance drift of the first measurement electrode based on the second, third and fourth electrical impedances; (ii) the skin-electrode resistance drift of the second measurement electrode based on the fifth, sixth and seventh electrical impedances; and (d) calculating the internal impedance of the biological object by subtracting the skin-electrode resistance drifts of the first and second measurement electrodes from the first electrical impedance.
156 Citations
23 Claims
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1. A method for monitoring the internal electrical impedance of a biological object, with compensation for skin-electrode resistance drift, during an extended monitoring period, comprising the steps of:
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(a) placing a first measurement electrode and a second measurement electrode on the biological object, said first measurement electrode and said second measurement electrode being part of a measurement circuit; (b) placing a first reference electrode and a second reference electrode on the biological object, substantially adjacent to said first measurement electrode, said first measurement electrode and said first reference electrode being part of a first reference circuit, said first measurement electrode and said second reference electrode being part of a second reference circuit, said first reference electrode and said second reference electrode being part of a third reference circuit; (c) at least once during the monitoring period; (i) measuring a first electrical impedance of said measurement circuit; (ii) measuring a second electrical impedance of said first reference circuit; (iii) measuring a third electrical impedance of said second reference circuit; and (iv) measuring a fourth electrical impedance of said third reference circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for monitoring the internal electrical impedance of a biological object, with compensation for skin-electrode resistance drift, during an extended monitoring period, comprising the steps of:
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(a) placing a first measurement electrode and a second measurement electrode on the biological object, said first measurement electrode and said second measurement electrode being part of a measurement circuit; (b) placing a first reference electrode and a second reference electrode on the biological object, substantially adjacent to said first measurement electrode, said first measurement electrode and said first reference electrode being part of a first reference circuit, said first measurement electrode and said second reference electrode being part of a second reference circuit, said first reference electrode and said second reference electrode being part of a third reference circuit; (c) at least once during the monitoring period; (i) imposing an alternating electrical current between said first measurement electrode and said second measurement electrode and obtaining a first voltage signal representative of a voltage drop in said measurement circuit; (ii) imposing an alternating electrical current between said first measurement electrode and said first reference electrode and obtaining a second voltage signal representative of a voltage drop in said first reference circuit; (iii) imposing an alternating electrical current between said first measurement electrode and said second reference electrode and obtaining a third voltage signal representative of a voltage difference in said second reference circuit; (iv) imposing an alternating electrical current between said first reference electrode and said second reference electrode and obtaining a fourth voltage signal representative of a voltage drop in said third reference circuit. - View Dependent Claims (14)
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15. An impedance plethysmography device, comprising:
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(a) a first measurement electrode; (b) a second measurement electrode; (c) a first reference electrode; (d) a second reference electrode; (e) a measurement electrical circuit including said first measurement electrode, said second measurement electrode, and a first impedance measurement means for measuring a first electrical impedance; (f) a first reference electrical circuit including said first measurement electrode, said first reference electrode, and a second impedance measurement means for measuring a second electrical impedance; (g) a second reference electrical circuit including said first measurement electrode, said second reference electrode, and a third impedance measurement means for measuring a third electrical impedance; (h) a third reference electrical circuit including said first reference electrode, said second reference electrode, and a fourth impedance measurement means for measuring a fourth electrical impedance. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A medical monitoring system comprising an impedance plethysmography device, said impedance plethysmography device further comprising:
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(a) a first measurement electrode; (b) a second measurement electrode; (c) a first reference electrode; (d) a second reference electrode; (e) a measurement electrical circuit including said first measurement electrode, said second measurement electrode, and a first impedance measurement means for measuring a first electrical impedance; (f) a first reference electrical circuit including said first measurement electrode, said first reference electrode, and a second impedance measurement means for measuring a second electrical impedance; (g) a second reference electrical circuit including said first measurement electrode, said second reference electrode, and a third impedance measurement means for measuring a third electrical impedance; (h) a third reference electrical circuit including said first reference electrode, said second reference electrode, and a fourth impedance measurement means for measuring a fourth electrical impedance. - View Dependent Claims (23)
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Specification