Bioelectrical impedance ECG measurement and defibrillator implementing same

• US 6,625,487 B2
• Filed: 07/17/2001
• Issued: 09/23/2003
• Est. Priority Date: 07/17/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Herleikson, Earl C.
• Primary Examiner(s): Evanisko, George R.
• Application Number:
  US09/908,293
• Publication Number:
  US 20030032989A1
• Time in Patent Office: 798 Days
• Field of Search: 607/8, 607/28, 600/547
• US Class Current: 607/8
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

A multivariate impedance (Z) measurement module, for use in an electrotherapy device, that accurately measures patient impedance. The Z measurement module implements a resistive network model of the patient'"'"'s body defined by one or more equations each including resistive elements that represent the impedance of a current paths through the patient. The Z measurement module utilizes at least three electrodes placed at predetermined relative locations on the patient'"'"'s body, and measures the voltage across different electrode pairs while an applying an alternating current through certain electrodes. The applied current and measured voltages are used to solve the patient model equations for the individual resistive elements. Thus, each individual impedance component is separately and accurately determined.

Claims

1. A multivariate impedance measurement module, for use in an electrotherapy device, said module comprising:

a multiple electrode pair control circuit adapted to provide an alternating current, said control circuit connected to at least three electrodes, the electrodes external to the control circuit and adapted to be placed at predetermined relative locations on a patient'"'"'s body;

a controller for controlling said multiple electrode pair control circuit to

(a) successively apply the alternating current to all possible pairs of the at least three electrodes, and, during each such application of alternating current, successively measure a voltage across all remaining electrode pairs other than the electrode pair to which the current is being applied; and

(b) short each combination of two of the at least three electrodes and apply the alternating current and measure a voltage across each combination of shorted electrodes and the remaining non-shorted electrode,

wherein said controller further comprises a resistive network model of the patient'"'"'s body, said model defined by voltage/current equations having terms representing an impedance of each current path between the at least three electrodes through the patient, wherein the controller solves the equations for the terms representing the impedance of each current path between the at least three electrodes with information obtained by said controller in (a) and (b).

2. The multivariate impedance measurement module of claim 1, wherein said measurement module is adapted for the electrotherapy device selected from the group consisting of a cardioverter, a defibrillator and a pacemaker.

3. The multivariate impedance measurement module of claim 1, wherein said resistive network model includes resistive elements each representing an impedance of a current path that connects nodes of the network model, said nodes respectively comprising a point at which alternating current delivered by each of said at least three electrodes enters the patient'"'"'s body.

4. The multivariate impedance measurement module of claim 3, wherein said resistive elements comprise:

a plurality of resistive elements each representing an electrode/skin impedance between each of said at least three electrodes and a corresponding location at which current delivered by each said electrode is adapted to be delivered into the patient'"'"'s body.

5. The multivariate impedance measurement module of claim 4, wherein said resistive elements further comprise:

an impedance of each current path from the corresponding location at which current is delivered into the patient'"'"'s body and a geometric center of said resistive network model.

6. The multivariate impedance measurement module of claim 5, wherein said resistive elements further comprise:

an impedance of a current path from a first location at which current is delivered into the patient'"'"'s body to a second location at which current exits the patient'"'"'s body.

7. The multivariate impedance measurement module of claim 1, wherein said controller is adapted to solve the voltage/current equations for the impedance of current paths utilizing said applied currents and measured voltages.

8. The multivariate impedance measurement module of claim 7, wherein said multiple electrode pair control circuit further comprises:

an electrode selection switch network configured to apply the alternating current to successive electrode pairs, and to measure a voltage across each electrode pair other than a selected electrode pair.

9. The multivariate impedance measurement module of claim 7, wherein said multiple electrode pair control circuit further comprises:

a DC-to-AC converter for converting DC current from an external DC current source to alternating current having a first frequency.

10. The multivariate impedance measurement module of claim 9, wherein said multiple electrode pair control circuit further comprises:

an AC-to-DC converter for converting an AC voltage signal across an electrode pair to a DC voltage signal.