Pulse Detection Method and Apparatus Using Patient Impedance

• US 20070288060A1
• Filed: 04/19/2007
• Published: 12/13/2007
• Est. Priority Date: 09/30/1999
• Status: Active Grant

• Current Assignee: Cynthia Jayne, David Hampton, James Taylor, Patricia O'Hearn, Paula Lank, Ronald Stickney
• Original Assignee: Physio-Control Incorporated (Stryker Corporation)
• Inventors: O'Hearn, Patricia, Lank, Paula, Taylor, James, Stickney, Ronald, Hampton, David, Jayne, Cynthia
• Granted Patent: US 8,092,392 B2
• Time in Patent Office: Days
• US Class Current: 607/8
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

The presence of a cardiac pulse in a patient is determined by evaluating fluctuations in an electrical signal that represents a measurement of the patient'"'"'s transthoracic impedance. Impedance signal data obtained from the patient is analyzed for a feature indicative of the presence of a cardiac pulse. Whether a cardiac pulse is present in the patient is determined based on the feature in the impedance signal data. Electrocardiogram (ECG) data may also be obtained in time coordination with the impedance signal data. Various applications for the pulse detection of the invention include detection of PEA and prompting PEA-specific therapy, prompting defibrillation therapy and/or CPR, and prompting rescue breathing depending on detection of respiration.

Claims

1. A method of determining the presence of a cardiac pulse in a patient, comprising:

(a) obtaining data derived from an impedance-sensing signal that has been communicated through the patient;

(b) analyzing the obtained impedance signal data for a feature indicative of the presence of a cardiac pulse, wherein analyzing the impedance signal data includes evaluating energy in the impedance signal data; and

(c) determining whether a cardiac pulse is present in the patient based on the feature in the impedance signal data.

2. The method of claim 1, wherein evaluating energy in the impedance signal data includes:

(a) selecting data from the obtained impedance signal data for an energy calculation; and

(b) calculating an energy in the selected impedance signal data.

3. The method of claim 2, wherein the calculated energy is the feature indicative of the presence of a cardiac pulse, the method further comprising comparing the feature to a predetermined energy threshold to determine whether a cardiac pulse is present in the patient.

4. The method of claim 1, further comprising prompting delivery of chest compressions of cardiopulmonary resuscitation to the patient if a cardiac pulse is determined not present in the patient.

5. The method of claim 1, further comprising:

(a) obtaining electrocardiogram (ECG) data from the patient; and

(b) determining the presence of a QRS complex in the ECG data, wherein analyzing the obtained impedance signal data for a feature indicative of the presence of a cardiac pulse further includes determining whether a QRS complex occurred in the ECG data.

6. The method of claim 5, further comprising locating a QRS complex in the ECG data and selecting impedance signal data for the energy calculation based on the located QRS complex.

7. The method of claim 1, wherein analyzing the obtained impedance signal data further includes determining cardiac output in terms of a stroke volume or rate of output, wherein the determined cardiac output is used as an additional feature indicative of the presence of a cardiac pulse, and wherein the cardiac output feature is compared to a predetermined output threshold to determine whether a cardiac pulse is present in the patient.

16. The medical device of claim 1S, wherein the processing unit is configured to evaluate energy in the impedance signal data by selecting impedance signal data for an energy calculation and calculating the energy in the selected impedance signal data.

17. The medical device of claim 16, wherein the calculated energy is the feature indicative of the presence of a cardiac pulse, the processing unit being further configured to compare the feature to a predetermined energy threshold to determine whether a cardiac pulse is present in the patient.

8. A method of determining the presence of a cardiac pulse in a patient, comprising:

(a) obtaining data derived from an impedance-sensing signal that has been communicated through the patient;

(b) analyzing the obtained impedance signal data for a feature indicative of the presence of a cardiac pulse, wherein analyzing the impedance signal data includes comparing the impedance signal data to a previously-identified impedance signal data pattern known to predict the presence of a cardiac pulse; and

(c) determining whether a cardiac pulse is present in the patient based on the feature in the impedance signal data.

9. The method of claim 8, wherein the comparison produces a pattern match statistic that is the feature indicative of the presence of a cardiac pulse, the method further comprising comparing the feature to a predetermined pattern match threshold to determine whether a cardiac pulse occurred in the patient.

10. The method of claim 8, further comprising analyzing the impedance signal data for two or more features indicative of the presence of a cardiac pulse, wherein one of the features is determined from the comparison of the impedance signal data with a previously-identified impedance signal data pattern and wherein one of the other features is determined from an evaluation of an amplitude of the impedance signal data or an energy in the impedance signal data.

11. The method of claim 8, further comprising prompting delivery of chest compressions or cardiopulmonary resuscitation to the patient if a cardiac pulse is determined not present in the patient.

12. The method of claim 8, further comprising:

(a) obtaining electrocardiogram (ECG) data from the patient; and

(b) determining the presence of a QRS complex in the ECG data, wherein analyzing the obtained impedance signal data for a feature indicative of the presence of a cardiac pulse further includes determining whether a QRS complex occurred in the ECG data.

13. The method of claim 12, further comprising locating a QRS complex in the ECG data and selecting impedance signal data for the pattern match comparison based on the located QRS complex.

14. The method of claim 8, wherein analyzing the obtained impedance signal data further includes determining cardiac output in terms of a stroke volume or rate of output, wherein the determined cardiac output is used as an additional feature indicative of the presence of a cardiac pulse, and wherein the cardiac output feature is compared to a predetermined output threshold to determine whether a cardiac pulse is present in the patient.

15. A medical device, comprising:

(a) electrodes adapted for placement on a patient to sense an impedance-sensing signal that has been communicated through the patient;

(b) a conversion circuit in communication with the electrodes for converting the sensed impedance-sensing signal into digital impedance signal data;

(c) a processing unit in communication with the conversion circuit for processing the impedance signal data, wherein the processing unit is configured to

(i) analyze the impedance signal data for a feature indicative of the presence of a cardiac pulse in the patient by evaluating energy in the impedance signal data, and

(ii) determine whether a cardiac pulse is present in the patient based on the feature in the impedance signal data.

18. The medical device of claim 15, wherein the conversion circuit and the processing unit are implemented in a defibrillator.

19. The medical device of claim 18, wherein the defibrillator is an automated external defibrillator.

20. The medical device of claim 15, wherein the processing unit is further configured to analyze the impedance signal data by determining cardiac output in terms of a stroke volume or rate of output and use the determined cardiac output as an additional feature indicative of the presence of a cardiac pulse, the processing unit being further configured to compare the additional feature to a predetermined cardiac output threshold to determine whether a cardiac pulse is present in the patient.

21. The medical device of claim 15, further comprising a display in communication with the processing unit, wherein the processing unit is further reconfigured to prompt a message on the display reporting whether a cardiac pulse is present in the patient.

22. The medical device of claim 15, further comprising a display in communication with the processing unit, wherein the processing unit is further configured to provide a graph on the display showing a representation of the impedance signal data.

23. The medical device of claim 15, further comprising electrodes adapted to sense electrocardiogram (ECG) signals in the patient, wherein the conversion circuit further converts the ECG signal received from the patient into digital ECG data, and wherein the processing unit is further configured to analyze the ECG data, determine the presence of a QRS complex in the ECG data, and select impedance signal data corresponding in time with the QRS complex for the analysis of the impedance signal data.

24. A medical device, comprising:

(a) electrodes adapted for placement on a patient to sense an impedance-sensing signal that has been communicated through the patient;

(b) a conversion circuit in communication with the electrodes for converting the sensed impedance-sensing signal into digital impedance signal data; and

(c) a processing unit in communication with the conversion circuit for processing the impedance signal data, wherein the processing unit is configured to

(i) analyze the impedance signal data for a feature indicative of the presence of a cardiac pulse by comparing the impedance signal data to a previously-identified impedance signal data pattern known to predict the presence of a cardiac pulse, and

(ii) determine whether a cardiac pulse is present in the patient based on the feature in the impedance signal data.

25. The medical device of claim 24, wherein the comparison produces a pattern match statistic that is the feature indicative of the presence of a cardiac pulse, the processing unit being further configured to compare the feature to a predetermined pattern match threshold to determine whether a cardiac pulse is present in the patent.

26. The medical device of claim 24, wherein the conversion circuit and the processing unit are implemented in a defibrillator.

27. The medical device of claim 26, wherein the defibrillator is an automated external defibrillator.

28. The medical device of claim 24, wherein the processing unit is further configured to analyze the impedance signal data by determining a cardiac output in terms of a stroke volume or rate of output and use the determined cardiac output as an additional feature indicative of the presence of a cardiac pulse, the processing unit being further configured to compare the additional feature to a predetermined cardiac output threshold to determine whether a cardiac pulse is present in the patient.

29. The medical device of claim 24, further comprising a display in communication with the processing unit, wherein the processing unit is further configured to prompt a message on the display reporting whether a cardiac pulse is present in the patient.

30. The medical device of claim 24, further comprising a display in communication with the processing unit, wherein the processing unit is further configured to provide a graph on the display showing a representation of the impedance signal data.

31. The medical device of claim 24, further comprising electrodes adapted to sense electrocardiogram. (ECG) signals in the patient, wherein the conversion circuit further converts the ECG signal received from the patient into digital ECG data, and wherein the processing unit is further configured to analyze the ECG data, determine the presence of a QRS complex in the ECG data, and select impedance signal data corresponding in time with the QRS complex for the analysis of the impedance signal data.

32. The medical device of claim 24, wherein the processing unit is configured to analyze the impedance signal data for two or more features indicative of the presence of cardiac pulse, wherein one of the features is determined from the comparison of the impedance signal data with a previously-identified impedance signal data pattern and wherein one of the other features is determined from an evaluation of an amplitude of the impedance signal data or an energy in the impedance signal data.

33. An electrotherapy device, comprising:

(a) electrodes adapted to sense an electrocardiogram (ECG) signal from the patient;

(b) an electrotherapy generator in communication with the electrodes for delivering electrotherapy to the patient; and

(c) processing circuitry in communication with the electrodes and the electrotherapy generator and configured to;

analyze the patient'"'"'s ECG signal for asystole, and if the patient is determined to be in an asystole condition, prompt a user for delivery of chest compressions.

34. The electrotherapy device of claim 33, wherein the electrotherapy generator and the processing circuitry are implemented in a defibrillator.

35. The electrotherapy device of claim 34, wherein the defibrillator is an automated external defibrillator.

36. The electrotherapy device of claim 33, wherein the electrotherapy generator and the processing circuitry are implemented in an automated external defibrillator and wherein the electrodes are adapted to communicate an impedance-sensing signal through the patient and the processing circuitry is further configured to analyze the impedance-sensing signal to determine the presence of respiration in the patient, the processing circuitry prompting the delivery of rescue breathing therapy to the patient if respiration is determined not present in the patient.

37. The electrotherapy device of claim 33, wherein the electrotherapy generator and the processing circuitry are implemented in an automated external defibrillator and wherein the electrodes are adapted to communicate an impedance-sensing signal through the patient and the processing circuitry is further configured to analyze the impedance-sensing signal to determine the presence of respiration in the patient, the processing circuitry prompting the delivery of rescue breathing therapy to the patient if respiration is determined not present in the patient.

38. The electrotherapy device of claim 33 wherein the electrotherapy generator and the processing circuitry are implemented in an automated external defibrillator and wherein the electrodes are adapted to communicate an impedance-sensing signal through the patient and the processing circuitry is further configured to analyze the impedance-sensing signal to determine the presence of chest compressions being delivered to the patient, the processing circuitry prompting the delivery of chest compressions to the patient if chest compressions are not detected during a CPR period.