DETECTION OF REDUCED DEFIBRILLATION PAD CONTACT

• US 20140257422A1
• Filed: 03/06/2014
• Published: 09/11/2014
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Zoll Medical Corporation (Asahi Kasei Corporation)
• Original Assignee: Zoll Medical Corporation (Asahi Kasei Corporation)
• Inventors: Herken, Ulrich
• Granted Patent: US 9,427,597 B2
• Time in Patent Office: Days
• US Class Current: 607/8
• CPC Class Codes: A61N 1/046 Specially adapted for shock therapy, e.g. defibrillation
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3931 Protecting, e.g. back-up systems
• CPC Class Codes: A61N 1/3993 User interfaces for automatic external defibrillators

Abstract

A system and method of detecting a loss of electrical contact between a pair of electrodes that are electrically coupled to skin of a subject. The method includes monitoring parameters of a transthoracic impedance between the pair of electrodes in at least one of a low frequency regime and a high frequency regime, detecting an occurrence of chest compressions based on a signal indicative of chest compressions, establishing baseline levels of the parameters in at least one of the low and high frequency regimes, detecting whether changes in at least one parameter exceeds the baseline level by a threshold, determining that at least one electrode of the pair of electrodes is losing electrical contact with the skin responsive to the at least one parameter exceeding the baseline level by the threshold, and issuing an alert in response to a determination that the at least one electrode is losing electrical contact.

Claims

1. A life support device, comprising:

a pair of electrodes configured to be attached to a skin of a subject;

a therapy interface electrically coupled to the pair of electrodes; and

a transthoracic impedance monitor electrically coupled to the therapy interface, the transthoracic impedance monitor being configured to monitor transthoracic impedance parameters of a transthoracic impedance between the pair of electrodes in at least one a low frequency regime below a set frequency and a high frequency regime at or above the set frequency, to detect CPR chest compressions based on a signal indicative of the CPR chest compressions, to establish baseline levels of the transthoracic impedance parameters corresponding to the at least one of the low frequency regime and the high frequency regime, to detect whether changes in at least one transthoracic impedance parameter exceeds the baseline level by a threshold, to determine that at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject in response to detecting that the changes in the at least one transthoracic impedance parameter exceeds the baseline level by the threshold, and to issue an alert in response to a determination that the at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject.

2. The life support device of claim 1, wherein the transthoracic impedance monitor is further configured to monitor the transthoracic impedance parameters in both the low frequency regime and the high frequency regime.

3. The life support device of claim 2, further comprising:

a user interface including at least one of an audio output device and a video output device; and

at least one processor, electrically coupled to the therapy interface, the transthoracic impedance monitor, and user interface, the at least one processor being configured to present a message on the at least one of the audio output device and the video output device in response to receiving the alert.

4. The life support device of claim 3, wherein the message indicates that the at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject.

5. The life support device of claim 4, wherein the transthoracic impedance has a high frequency component that corresponds to a frequency of the CPR chest compressions, and wherein the transthoracic impedance parameters in the high frequency regime include at least one of a slope of the high frequency component, an amplitude of the high frequency component, and a shape of the high frequency component.

6. The life support device of claim 5, wherein the transthoracic impedance monitor is configured to identify the frequency of the CPR chest compressions based on a fundamental frequency of the transthoracic impedance.

7. The life support device of claim 5, wherein the transthoracic impedance monitor is configured to receive the signal indicative of the frequency of the CPR chest compressions from one of a compression sensor and a mechanical chest compression device and to identify the frequency of the CPR chest compressions based on the signal.

8. The life support device of claim 7, wherein the transthoracic impedance monitor is further configured to correlate at least one of the slope of the high frequency component, the amplitude of the high frequency component, and the shape of the high frequency component with the frequency of the CPR chest compressions.

9. The life support device of claim 8, further comprising:

a filter electrically coupled to the therapy interface, the filter being configured to filter out frequencies of the high frequency component of the transthoracic impedance that do not correspond to the frequency of the CPR chest compressions and harmonics thereof.

10. The life support device of claim 9, wherein the parameters in the high frequency regime range further include an energy level of the high frequency component and an energy level at harmonics of the high frequency component.

11. The life support device of claim 10, wherein the transthoracic impedance parameters in the high frequency regime further include an amount of background noise at frequencies other than a frequency of the high frequency component and harmonics of the high frequency component.

12. The life support device of claim 11, wherein the transthoracic impedance parameters in the low frequency regime include an amplitude of the transthoracic impedance.

13. The life support device of claim 1, wherein the transthoracic impedance has a high frequency component that corresponds to a frequency of the CPR chest compressions, and wherein the transthoracic impedance parameters in the high frequency regime include at least one of a slope of the high frequency component, an amplitude of the high frequency component, and a shape of the high frequency component.

14. The life support device of claim 13, wherein the transthoracic impedance monitor is further configured to correlate at least one of the slope of the high frequency component, the amplitude of the high frequency component, and the shape of the high frequency component with the frequency of the CPR chest compressions.

15. The life support device of claim 13, wherein the transthoracic impedance parameters in the high frequency regime range further include an energy level of the high frequency component and an energy level at harmonics of the high frequency component.

16. The life support device of claim 1, wherein the transthoracic impedance has a high frequency component that corresponds to a frequency of the CPR chest compressions, and wherein the transthoracic impedance parameters in the high frequency regime include an energy level of the high frequency component and an energy level at harmonics of the high frequency component.

17. A method of detecting a loss of electrical contact between a pair of electrodes that are electrically coupled to a skin of a subject, comprising acts of:

monitoring transthoracic impedance parameters of a transthoracic impedance between the pair of electrodes in at least one of a low frequency regime below a set frequency and a high frequency regime at or above the set frequency;

detecting an occurrence of CPR chest compressions based upon a signal indicative of the CPR chest compressions;

establishing baseline levels of the transthoracic impedance parameters in at least one of the low frequency regime and the high frequency regime;

detecting whether changes in at least one transthoracic impedance parameter exceeds the baseline level by a threshold;

determining that at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject in response to the at least one transthoracic impedance parameter exceeding the baseline level by the threshold; and

issuing an alert in response to a determination that the at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject.

18. The method of claim 17, wherein the act of monitoring includes monitoring the transthoracic impedance parameters in both the low frequency regime and the high frequency regime.

19. The method of claim 18, wherein the transthoracic impedance has a high frequency component that corresponds to a frequency of the CPR chest compressions, and wherein the act of monitoring transthoracic impedance parameters in the high frequency regime includes monitoring at least one of a slope of the high frequency component, an amplitude of the high frequency component, and a shape of the high frequency component.

20. The method of claim 19, wherein the act of detecting an occurrence of CPR chest compressions includes one of analyzing the transthoracic impedance to identify the frequency of the CPR chest compressions based on a fundamental frequency of the transthoracic impedance and receiving the signal indicative of the frequency of the CPR chest compressions from one of a compression sensor and a mechanical chest compression device and identifying the frequency of the CPR chest compressions based on the signal.

21. The method of claim 20, further comprising an act of:

correlating at least one of the slope of the high frequency component, the amplitude of the high frequency component, and the shape of the high frequency component with the frequency of the CPR chest compressions.

22. The method of claim 21, further comprising an act of:

filtering frequencies of the high frequency component of the transthoracic impedance that do not correspond to the frequency of the CPR chest compressions and harmonics thereof.

23. The method of claim 22, wherein the act of monitoring transthoracic impedance parameters in the high frequency regime further includes monitoring an energy level of the high frequency component and an energy level at harmonics of the high frequency component.

24. The method of claim 23, wherein the act of monitoring transthoracic impedance parameters in the high frequency regime further includes monitoring an amount of background noise at frequencies other than a frequency of the high frequency component and harmonics of the high frequency component.

25. The method of claim 17, wherein the act of monitoring transthoracic impedance parameters in the low frequency regime includes monitoring an amplitude of the transthoracic impedance.

26. The method of claim 17, wherein the act of monitoring transthoracic impedance parameters in the high frequency regime includes monitoring a proportion of an amount of energy at a frequency of the CPR chest compressions relative to amounts of energy at frequencies other than the frequency of the CPR chest compressions.

27. The method of claim 17, further comprising acts of:

determining whether the signal indicative of the CPR compressions is from one of a compression sensor and a mechanical chest compression device; and

adjusting the threshold in response to a determination that the signal is from one of the compression sensor and the mechanical chest compression device.

28. A life support device, comprising:

a pair of electrodes configured to be attached to a skin of a subject;

a therapy interface electrically coupled to the pair of electrodes; and

a transthoracic impedance monitor electrically coupled to the therapy interface, the transthoracic impedance monitor being configured to monitor transthoracic impedance parameters of a transthoracic impedance between the pair of electrodes in at least one a low frequency regime below a set frequency and a high frequency regime at or above the set frequency, to establish baseline levels of the transthoracic impedance parameters corresponding to the at least one of the low frequency regime and the high frequency regime, to detect whether changes in at least one transthoracic impedance parameter exceeds the baseline level by a threshold, to determine that at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject in response to detecting that the changes in the at least one transthoracic impedance parameter exceeds the baseline level by the threshold, and to issue an alert in response to a determination that the at least one electrode of the pair of electrodes is losing electrical contact with the skin of the subject.