Impedance measurement apparatus for assessment of biomedical electrode interface quality

• US 20070038257A1
• Filed: 08/11/2005
• Published: 02/15/2007
• Est. Priority Date: 08/11/2005
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gray, James
• Granted Patent: US 7,340,294 B2
• Time in Patent Office: Days
• US Class Current: 607/8
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/063 using impedance measurements
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/68 Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61N 1/3931 Protecting, e.g. back-up systems

Abstract

Apparatus for assessing the electrical properties of patient-electrode interfaces has a carrier signal source injecting two carrier signals comprising an AC signal with a DC offset to the electrodes. The carrier signals are out of phase. The outputs from the electrodes are formed into electrocardiographic lead signals in a pre-amplifier circuit. Signal processing circuit is coupled to the pre-amplifier circuit and provides a first signal comprising the AC carrier signal contained in an ECG lead signal and a second signal containing a DC offset signal. The first and second signals are provided to a microprocessor to obtain an output indicative of the electrical properties of electrode interfaces for the ECG lead signal.

Claims

1. Apparatus for assessing the electrical properties of an interface between a patient and electrodes applied to the patient, said apparatus comprising:

a carrier signal source couplable to the electrodes, said carrier signal source receiving DC energization and AC energization and outputting two carrier signals comprising an AC signal with a DC offset, the two carrier signals being out of phase with each other by a pre-selected amount, one of said output signals being suppliable to a selected one of said electrodes, the other of said output signals being suppliable to others of said electrodes;

amplifier means comprising at least one amplifier each having a pair of inputs, one of said inputs being couplable to the selected one of the electrodes, the other input being couplable to another of said electrodes, said amplifier producing an output lead signal in which AC and DC offset characteristics result from the electrical properties of the patient interfaces at the electrodes; and

signal processing means coupled to said amplifier means and receiving said output lead signal of said amplifier, said signal processing means having means for obtaining and providing a first signal comprising the AC signal characteristics of the output lead signal and for providing a second signal comprising the DC characteristics in the output lead signal, said signal processing means having means employing said first and second signals to provide an output indicative of the electrical properties of an interface between a patient and electrodes applied to the patient.

2. The apparatus according to claim 1 wherein said carrier signal source is further defined as providing two carrier signals phase shifted by 180°

from each other.

3. The apparatus according to claim 1 wherein said carrier signal source comprises a pair of cascaded amplifiers.

4. The apparatus according to claim 3 wherein said amplifiers receive AC energization to inverting input terminals and DC energization to non-inverting input terminals.

5. The apparatus according to claim 1 wherein said carrier signal source provides carrier signals incorporating AC energization having a frequency between about 240 - 800 Hz.

6. The apparatus according to claim 1 wherein said amplifier means includes a plurality of amplifiers.

7. The apparatus according to claim 1 wherein said signal processing means further provides signals containing physiological data from the patient.

8. The apparatus according to claim 7 wherein said signal processing means provides signals containing electrocardiographic data from the patient.

9. The apparatus according to claim 1 wherein said signal processing means further includes filter means for obtaining and providing said first and second signals, digital signal processing means for digitizing said first and second signals and wherein said means employing said first and second signals comprises a microprocessor.

10. The apparatus according to claim 1 wherein said means providing said first and second signals comprises a signal separator and a digital signal processor and wherein said means employing said first and second signals comprises a microprocessor.

11. The apparatus according to claim 1 wherein said means providing said first and second signals comprises a signal separator/digital signal processor for obtaining and providing said first and second signals and wherein said means employing said first and second signals comprises a microprocessor.

12. The apparatus according to claim 1 wherein said means employing said first and second signals is further defined as providing a measurement of electrode connection quality.

13. The apparatus according to claim 12 further comprising a display means coupled to said means providing said first and second signals for displaying said measurement of electrode connection quality.

14. The apparatus according to claim 13 wherein said display means provides a categorical gradation of electrode connection quality.

15. The apparatus according to claim 12 wherein said signal processing means provides an output indicating changes in electrode connection quality with respect to time to indicate potential for electrode connection failure.

16. The apparatus according to claim 1 wherein said carrier signal source includes means for selectively removing the AC energization from said carrier signals.

17. Apparatus for assessing the electrical properties of an interface between a patient and electrodes applied to the patient to obtain an ECG signal, said apparatus comprising:

a carrier signal source couplable to the electrodes, said carrier signal source receiving DC energization and AC energization and outputting two carrier signals comprising an AC signal with a DC offset, the two carrier signals being 180°

out of phase with each other, one of said output signals being suppliable to a selected one of said electrodes, the other of said output signals being suppliable to others of said electrodes;

amplifier means comprising [at least one] a plurality of amplifiers, each having a pair of inputs, one of which is couplable to the selected one of the electrodes, the other of which is couplable to another of said electrodes, said amplifiers producing output ECG lead signals in which AC and DC offset characteristics result from the electrical properties of the patient interfaces at the electrodes; and

signal processing means coupled to said amplifier means and receiving said output ECG lead signals of said amplifiers, said signal processing means having digital signal processing means for obtaining and providing first signals comprising the AC signal characteristics of the output lead signals and for providing second signals comprising the DC characteristics in the output lead signals, said signal processing means having a microprocessor employing said first signals and second signals to provide an output indicative of the electrical properties of an interface between a patient and electrodes applied to the patient.