Method and Apparatus for Detecting Seizures Including Loose Electrode Monitoring

• US 20160242668A1
• Filed: 10/22/2014
• Published: 08/25/2016
• Est. Priority Date: 10/23/2013
• Status: Active Grant

• Current Assignee: Novela Neurotechnologies, Inc.
• Original Assignee: Brain Sentinel, Inc.
• Inventors: Halleck, Michael E., Girouard, Michael R., Halleck, Michael D.
• Granted Patent: US 10,342,451 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/6844 Monitoring or controlling distance between sensor and tissue

Abstract

Apparatuses and methods for monitoring a patient for seizure activity and for verifying the contact integrity of electrodes included among an EMG sensor may include generating a test signal of known periodicity and applying the signal to at least one electrode in a sensor system. The test signal may be monitored to verify contact integrity of the electrodes.

Claims

1. A method of monitoring a patient for seizure activity by collecting data with an electromyographic sensor and for checking the contact integrity of electrodes included among the sensor comprising the steps of:

positioning one or more detection electrodes and a common electrode on the skin of a patient on or near at least one muscle;

applying a test signal to said common electrode;

collecting a signal from at least one of said detection electrodes;

wherein the positioned electrodes are configured such that when contact integrity is maintained between the skin and the positioned electrodes said applied test signal is included among said collected signal;

evaluating said collected signal for characteristics of seizure activity;

analyzing said collected signal for detection of said test signal; and

determining based on the detection of said test signal whether said contact integrity is maintained between the skin and the positioned electrodes.

2. The method of claim 1 wherein said determination of whether said contact integrity is maintained between the skin and the positioned electrodes includes establishing whether a threshold level of detection of said test signal is met.

3. The method of claim 1 wherein the positioned electrodes are configured such that when contact integrity between the skin and the positioned electrodes declines, the amplitude of said detected test signal decreases.

4. The method of claim 1 wherein said one or more detection electrodes includes a pair of detection electrodes connected to inputs of a differential amplifier.

5. The method of claim 1 further comprising configuring said electromyography sensor to maintain an imbalance potential at the inputs of an amplifier when said contact integrity is maintained;

and

amplification of said collected signal;

wherein the imbalance potential enhances the amplification of said collected signal.

6. The method of claim 5 wherein said imbalance potential is maintained because at least one of the detection electrodes is connected to a resistive element.

7. The method of claim 6 wherein said resistive element is an about 20Ω

to an about 200Ω

resistor.

8. The method of claim 5 wherein said imbalance is established because at least one of the detection electrodes is connected to a low pass filter.

9. The method of claim 1 wherein said one or more detection electrodes includes a pair of detection electrodes;

wherein said pair of detection electrodes have different impedance values, the impedance difference suitable to maintain an imbalance potential at the inputs of an amplifier when said contact integrity is maintained between the patient'"'"'s skin and the positioned electrodes.

10. The method of claim 9 wherein a first detection electrode among said pair of detection electrodes has an input impedance of about 2 KΩ

to about 20 KΩ

; and

wherein the other of said pair of detection electrodes has an input impedance that is about 1% to about 10% lower in magnitude than the first detection electrode.

11. The method of claim 9 wherein at least one of the impedance values for one of the detection electrodes among said pair of detection electrodes is frequency dependent.

12. The method of claim 9 wherein at least one of the impedance values for the detection electrodes among said pair of detection electrodes is greater for applied frequencies above about 1 KHz than for applied frequencies within a range of about 20 Hz to about 500 Hz.

13. The method of claim 1 further comprising directing the collected signal through an amplifier;

and

amplification of the collected signal by said amplifier;

wherein said positioning of electrodes is sufficient to create an imbalance potential at the inputs of said amplifier when said contact integrity is maintained between the skin and the positioned electrodes;

wherein the imbalance potential enhances the amplification of said collected signal.

14. The method of claim 1 wherein said one or more detection electrodes includes a pair of detection electrodes connected to inputs of an amplifier, and further comprising:

amplification of the collected signal by connecting said pair of detection electrodes to said amplifier;

wherein said pair of detection electrodes have different impedance values, the impedance difference suitable to maintain an imbalance potential at the inputs of said amplifier in magnitude sufficient to enhance the detection of the test signal when said contact integrity is maintained between the skin and the positioned electrodes.

15. The method of claim 1 wherein said one or more detection electrodes includes a pair of detection electrodes connected to inputs of an amplifier, and further comprising:

amplification of the collected signal by said amplifier;

wherein at least one of said pair of detection electrodes is connected to an element with sufficient impedance to create an imbalance potential at the inputs of said amplifier when said contact integrity is maintained between the skin and the positioned electrodes; and

wherein the imbalance potential enhances the detection of said test signal.

16. The method of claim 15 wherein said element is an about 20Ω

to an about 200Ω

resistor.

17. The method of claim 1 wherein the test signal is a time-varying test signal within the frequency range of about 1 KHz to about 5 KHz;

and

wherein evaluating said collected signal analyzed for seizure activity includes evaluating the collected signal for muscle electrical activity in a frequency range between about 20 Hz to about 500 Hz.

18. The method of claim 1 wherein said evaluating said collected signal analyzed for seizure activity includes determining whether said collected signal meets a threshold value of a characteristic related to muscle electrical activity.

19. The method of claim 18 wherein said threshold value is a T-squared statistical value

calculated from an EMG power spectrum.

20. The method of claim 18 wherein said threshold value comprises detection of a plurality of EMG data bursts.

21. The method of claim 18 wherein said threshold value comprises detection of a characteristic GTC waveform.

22. The method of claim 1 wherein the test signal is a time-varying test signal with a controlled period.

23. The method of claim 22 wherein said analyzing the collected signal for detection of said test signal comprises:

partitioning the collected signal into an analysis window;

wherein the analysis window is an integral number of multiples of the test signal period; and

determining whether the analysis window includes one or more repetitive characteristics that match the periodicity of the test signal.

24. The method of claim 23 wherein a phase delay between the analysis window and the applied test signal is constant.

25. The method of claim 23 wherein said analysis window is some integral multiple of oscillations of a clock or oscillator;

and

wherein the test signal period is determined using said clock or oscillator.

26. The method of claim 23 wherein said repetitive characteristic is selected from the group of characteristics including phase delay, amplitude of signal, number of positive amplitude peaks, or number of negative amplitude peaks.

27. The method of claim 23 wherein said analyzing the collected signal for said detection of said test signal comprises:

partitioning the collected signal into an analysis window;

wherein the analysis window is an integral number of multiples of the test signal period; and

determining whether the amplitude of the collected signal meets a threshold detection level for sensing of the test signal.

28. The method of claim 22 wherein said analyzing the collected signal for said detection of said test signal comprises:

partitioning the collected signal into an analysis window;

wherein the analysis window is an integral number of multiples of the test signal period;

determining a number of positive and/or negative amplitude peaks; and

determining whether the number of positive and/or negative amplitude peaks matches an expected value.

29. The method of claim 1 wherein said one or more detection electrodes includes a pair of detector electrodes, and further comprising:

amplification of the collected signal by connecting said pair of detection electrodes to an amplifier;

evaluating the output of said amplifier for both said characteristics of seizure activity and for said detection of said test signal.

30. The method of claim 1 wherein said one or more detection electrodes includes a pair of detector electrodes, and further comprising:

amplification of the collected signal by connecting said pair of detection electrodes to a detection amplifier and connecting at least one detection electrode among said pair of detection electrodes to a second amplifier;

evaluating the output of said detection amplifier for said characteristics of seizure activity; and

evaluating the output of said second amplifier for the detection of said test signal.

31. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35. (canceled)

36. (canceled)

37. (canceled)

38. (canceled)

39. (canceled)

40. (canceled)

41. (canceled)

42. (canceled)

43. (canceled)

44. (canceled)

45. (canceled)