Automated ECG lead impedance measurement integrated into ECG gating circuitry

• US 20080051845A1
• Filed: 08/25/2006
• Published: 02/28/2008
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Ivy Biomedical Systems Inc
• Original Assignee: Ivy Biomedical Systems Inc
• Inventors: Mentelos, Richard A.
• Granted Patent: US 7,818,058 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/28 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 8/543 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61N 1/3603 Control systems
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

The present invention relates to a system and method for determining the impedance of an electrode at the electrode-body interface. The electrode-body impedance of one of the electrodes may be calculated using the voltage difference between that electrode and a plurality of other electrodes, and the voltage and impedance of an alternating current generator in communication with the electrodes.

Claims

1. A system for measuring the impedance at the electrode-body interface comprising:

a processor;

an alternating current generator in communication with the processor, the alternating current generator having an output voltage and an output impedance; and

a plurality of electrodes in communication with the processor and the alternating current generator, each electrode having an electrode-body impedance,

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes.

2. The system of claim 1 wherein the alternating current generator provides a constant current output.

3. The system of claim 2 wherein the impedance at the electrode-body interface is linearly related to the voltage between two or more of the electrodes.

4. The system of claim 1 further comprising a plurality of switches, each switch associated with a respective electrode.

5. The system of claim 4 wherein the switches are field effect transistors.

6. The system of claim 1 further comprising a synchronous rectifier in electrical communication between the processor and the electrodes.

7. The system of claim 6 wherein the synchronous rectifier is further in communication with the alternating current generator and samples the peak amplitude of a waveform generated by the alternating current generator.

8. The system of claim 1 wherein the plurality of electrodes comprise three electrodes.

9. The system of claim 8 wherein the voltage between two or more of the electrodes is measured by paralleling two of the electrodes while measuring the voltage of the third electrode.

10. The system of claim 1 wherein the alternating current generator operates at a frequency of 10 Hz.

11. The system of claim 1 wherein the alternating current generator generates a current of less than 50 microamps RMS.

12. The system of claim 1 wherein the alternating current generator generates a current of 10 microamps RMS.

13. The system of claim 1 wherein the alternating current generator generates a triangular voltage waveform.

14. The system of claim 1 further comprising an analog to digital converter in electrical communication between the processor and the synchronous rectifier.

15. The system of claim 1 further comprising an analog to digital converter in electrical communication between the processor and the electrodes.

16. A gamma camera system comprising:

a gamma camera; and

an impedance measuring device in electrical communication with the gamma camera comprising;

a processor;

an alternating current generator in communication with the processor, the alternating current generator having an output voltage and an output impedance; and

a plurality of electrodes in communication with the processor and the alternating current generator, each electrode having an electrode-body impedance,

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes,

wherein the user of the gamma camera is notified of the electrode-body impedance of the plurality of electrodes.

17. A stress testing system comprising:

an ECG device for stress testing; and

an impedance measuring device in electrical communication with the ECG stress testing system comprising;

a processor;

an alternating current generator in communication with the processor, the alternating current generator having an output voltage and an output impedance; and

a plurality of electrodes in communication with the processor and the alternating current generator, each electrode having an electrode-body impedance,

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes,

wherein the user of the ECG stress testing system is notified of the electrode-body impedance of the plurality of electrodes.

18. A defibrillator system comprising:

a defibrillator; and

an impedance measuring device in electrical communication with the defibrillator comprising;

a processor;

an alternating current generator in communication with the processor, the alternating current generator having an output voltage and an output impedance; and

a plurality of electrodes in communication with the processor and the alternating current generator, each electrode having an electrode-body impedance,

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes,

wherein the user of the defibrillator is notified of the electrode-body impedance of the plurality of electrodes.

19. A EEG system comprising:

an EEG device; and

an impedance measuring device in electrical communication with the EEG device comprising;

a processor;

an alternating current generator in communication with the processor, the alternating current generator having an output voltage and an output impedance; and

a plurality of electrodes in communication with the processor and the alternating current generator, each electrode having an electrode-body impedance,

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes,

wherein the user of the EEG device is notified of the electrode-body impedance of the plurality of electrodes.

20. A clinical system comprising:

a plurality of electrodes for attachment to a body of a patient and each of said electrodes having electrode-body impedance;

a clinical device in communication with the electrodes; and

an impedance measuring device in electrical communication with the clinical device, the impedance measuring device comprising;

a processor in communication with the electrodes; and

an alternating current generator in communication with the processor and the plurality of electrodes, the alternating current generator having an output voltage and an output impedance;

wherein the processor calculates the impedance at the electrode-body interface in response to the output impedance of the alternating current generator, the output voltage of the alternating current generator and the voltage between two or more of the electrodes,

wherein the user of the clinical device is notified of the electrode-body impedance of the plurality of electrodes.

21. The system of claim 20 wherein the clinical device is a device for which skin electrodes are required for one of measurement or current delivery.

22. The system of claim 21 wherein the clinical device is selected from the group consisting of a transcutaneous nerve stimulator, a depth of anesthesia monitoring system, an EMG monitor, a CT scanner, a MRI, an ultrasound, or a lithotripter.

23. A method for measuring the impedance of the body-electrode interface in a system comprising an alternating current generator and a plurality of electrodes, the method comprising:

measuring an output impedance of the alternating current generator;

measuring an output voltage of the alternating current generator;

measuring a voltage between two or more electrodes of a plurality of electrodes in communication with the alternating current generator; and

calculating an impedance at the electrode-body interface using the output impedance of an alternating current generator, the output voltage of the alternating current generator and the voltage between two or more electrodes.

24. The method of claim 23 wherein the alternating current generator provides a constant current output.

25. The method of claim 24 wherein the impedance at the electrode-body interface is linearly related to the voltage between two or more of the electrodes.

26. The method of claim 23 wherein the plurality of electrodes comprises three electrodes.

27. The method of claim 26 wherein the voltage between two or more electrodes is measured by paralleling two of the electrodes while measuring the voltage between the paralleled electrodes and the third electrode.

28. The method of claim 23 wherein the alternating current generator operates at a frequency of 10 Hz.

29. The method of claim 23 wherein the alternating current generator generates a current of less than 50 microamps RMS.

30. The method of claim 23 wherein the alternating current generator generates a current of 10 microamps RMS.

31. The method of claim 23 wherein the alternating current generator generates a triangular voltage waveform.