Method of utilizing an external defibrillator by replacing its electrodes

• US 20030023277A1
• Filed: 09/05/2002
• Published: 01/30/2003
• Est. Priority Date: 03/07/1997
• Status: Active Grant

• Current Assignee: Zoll Medical Corporation (Asahi Kasei Corporation)
• Original Assignee: Cardiac Science Operating Company (Cardica Incorporated)
• Inventors: Owen, James M., Totman, Mark H., Fincke, Randall W., OʼLeary, James P.
• Granted Patent: US 6,944,498 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61N 1/0452 Specially adapted for transcutaneous muscle stimulation [TMS]
• CPC Class Codes: A61N 1/0456 Specially adapted for transcutaneous electrical nerve stimulation [TENS]
• CPC Class Codes: A61N 1/046 Specially adapted for shock therapy, e.g. defibrillation
• CPC Class Codes: A61N 1/0468 Specially adapted for promoting wound healing
• CPC Class Codes: A61N 1/0472 Structure-related aspects
• CPC Class Codes: A61N 1/0476 Array electrodes (including any electrode arrangement with more than one electrode for at least one of the polarities)
• CPC Class Codes: A61N 1/0492 Patch electrodes A61N1/0412, A61N1/0428 take precedence
• CPC Class Codes: A61N 1/0496 characterised by using specific chemical compositions, e.g. hydrogel compositions, adhesives
• CPC Class Codes: A61N 1/3904 External heart defibrillators [EHD]
• CPC Class Codes: A61N 1/3918 characterised by shock pathway, e.g. by electrode configuration
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3937 Monitoring output parameters
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock
• CPC Class Codes: A61N 1/3993 User interfaces for automatic external defibrillators

Abstract

A method of treating a patient for ventricular tachycardia using a wearable defibrillator includes monitoring the patient for a predetermined condition via one or more electrodes on the defibrillator, sending a message to the patient in response to the predetermined condition, activating the defibrillator so that the defibrillator delivers defibrillation energy to the patient, and storing at least one of the results of the monitoring, sending and activating steps in a memory on the defibrillator. The method also includes downloading information stored in the memory of the defibrillator to a base station having an external interface, and transmitting the information downloaded from the memory of the base station to an external location via the external interface of the base station.

Claims

1. A wearable defibrillator adapted to deliver defibrillation energy to a patient, the wearable defibrillator comprising:

at least one electrode having a conductive surface in contact with the patient'"'"'s skin, the at least one electrode being adapted for long-term wear on the patient.

2. A wearable defibrillator according to claim 1, wherein the at least one electrode comprises one or more of the following types of electrodes:

a segmented electrode, a low-surface area electrode, a traditional defibrillation electrode, and a subcutaneous electrode.

3. A wearable defibrillator according to claim 1, wherein the at least one electrode is wearable for a period of greater than one week.

4. A wearable defibrillator according to claim 1, wherein the at least one electrode includes electrically-conductive hydrogel at a surface thereof with contacts to the patient'"'"'s skin, the electrically-conductive hydrogel having a predetermined ion concentration.

5. A wearable defibrillator according to claim 4, wherein the electrically-conductive hydrogel includes a therapeutic agent which promotes skin health.

6. A wearable defibrillator according to claim 1, wherein the at least one electrode includes a mesh at a surface thereof which contacts to the patient'"'"'s skin.

7. A wearable defibrillator according to claim 1, wherein the at least one electrode is periodically movable to different positions on the patient.

8. A wearable defibrillator for delivering defibrillation energy to a patient, the defibrillator comprising:

at least one electrode which attaches to the patient for transmitting the defibrillation energy to the patient and for receiving patient information from the patient;

a plurality of capacitors which are switchable so as to alter characteristics of the defibrillation energy; and

a controller which controls switching of the plurality of capacitors in accordance with the patient information received from the at least one electrode.

9. A wearable defibrillator according to claim 8, wherein the patient information comprises a thoracic impedance of the patient.

10. A wearable defibrillator according to claim 9, wherein the thoracic impedance is determined periodically by applying an AC signal through the at least one electrode, sampling data obtained from the at least one electrode in response to the AC signal, and analyzing the sampled data.

11. A wearable defibrillator according to claim 9, wherein the thoracic impedance is calculated each time the defibrillation energy is transmitted to the patient based on patient information received from the at least one electrode in response to the defibrillation energy.

12. A wearable defibrillator according to claim 9, wherein the controller controls switching of the capacitors in a case that the thoracic impedance of the patient is within a predetermined range.

13. A wearable defibrillator according to claim 8, wherein the patient information comprises an electrocardiogram of the patient.

14. A wearable defibrillator according to claim 13, wherein the controller controls switching of the capacitors in a case that the electrocardiogram indicates a cardiac arrhythmia and in a case that the patient is unconscious.

15. A wearable defibrillator according to claim 8, wherein the patient information comprises electrode-to-skin impedance, the electrode-to-skin impedance being used to determine connection of the at least one electrode to the patient.

16. A wearable defibrillator according to claim 8, wherein the patient information comprises artifact noise in the patient'"'"'s body.

17. A wearable defibrillator according to claim 8, further comprising a memory which stores the patient parameter, the patient parameters comprising at least one of the patient'"'"'s name;

the language used for voice and corresponding text messages;

a minimum audio level to which a patient responds a minimum tactile stimulation signal to which a patient responds, a maximum tactile stimulation signal for a patient, a pacing bradycardia rate, a pace current level, the patient'"'"'s ID number, a ventricular tachycardia rate at which defibrillation energy is to be delivered to the patient, the patient'"'"'s thoracic impedance range, a time and a date at which the defibrillator was issued to the patient, a name of a clinic at an external location, a name of a clinician at the external location, and an electrode-to-skin impedance range;

wherein the controller controls switching of the plurality of capacitors also in accordance with the patient parameters.

18. A wearable defibrillator according to claim 8, wherein the plurality of capacitors comprises five capacitors;

and

wherein the five capacitors are switchable in configurations of 221, 2111 and 1111.

19. A wearable defibrillator according to claim 8, wherein the at least one electrode is capable of transmitting a tactile stimulation signal from at least one of the plurality of capacitors to the patient.

20. A wearable defibrillator according to claim 19, wherein the tactile stimulation signal is transmitted to the patient in a case that the patient information indicates that the patient has suffered a cardiac arrhythmia.

21. A wearable defibrillator according to claim 8, wherein the wearable defibrillator includes a floating ground.

22. A wearable defibrillator for delivering defibrillation energy to a patient, the defibrillator comprising:

at least one electrode which attaches to the patient for transmitting the defibrillation energy to the patient; and

a signal generator for generating the defibrillation energy, wherein the defibrillation energy has a bi-phasic waveform with a peak amplitude that is below 23 amperes for a patient having a thoracic impedance which is at least 40 ohms.

23. A wearable defibrillator according to claim 22, wherein the bi-phasic waveform includes two phases having substantially identical durations.

24. A wearable defibrillator according to claim 22, wherein the bi-phasic waveform includes two phases in which a first phase has a duration which is greater than a duration of the second phase.

25. A wearable defibrillator according to claim 23, wherein the at least one electrode receives information from the patient which indicates a thoracic impedance of the patient;

and

wherein the signal generator varies the peak amplitude of the defibrillation energy in accordance with the thoracic impedance of the patient.

26. A wearable defibrillator according to claim 25, wherein the signal generator comprises a plurality of capacitors which are switchable in order to affect the amplitude of the defibrillation energy.

27. A wearable defibrillator according to claim 26, further comprising a resistor in series with the plurality of capacitors.

28. A wearable defibrillator according to claim 23, wherein an average amplitude of the defibrillation energy is below 17 amperes for a patient having a thoracic impedance which is at least 40 ohms.

29. A wearable defibrillator according to claim 23, wherein the bi-phasic waveform is truncated and delivered within a predetermined time period.

30. A wearable defibrillator according to claim 22, wherein each of electrode has a surface area which is less than 60 cm².

31. A wearable defibrillator according to claim 22, wherein each electrode has a surface area which is less than 50 cm².

32. A wearable defibrillator according to claim 22, wherein each electrode has a surface area which is less than 40 cm².

33. A wearable defibrillator according to claim 22, wherein each electrode has a surface area which is less than 30 cm².

34. A wearable defibrillator for delivering defibrillation energy to a patient, the defibrillator comprising:

a signal generator for generating the defibrillation energy; and

a plurality of segmented electrodes each having a conductive area for transmitting the defibrillation energy to the patient, wherein the plurality of segmented electrodes are divided into groups of two or more electrodes, each of the groups of electrodes having at least one line connected to the signal generator, each line having a length sufficient for each group of electrodes to be placed on the patient a predetermined distance away from others of the groups of electrodes, the electrodes in at least one of the groups being spatially arranged to have an effective conductive area which is greater than a total combined conductive area of the electrodes in the group.

35. A wearable defibrillator according to claim 34, further comprising a plurality of non-electrically conductive pads;

wherein each of the groups of two or more electrodes is mounted on one of the plurality of non-electrically conductive pads such that each electrode in the group of electrodes is mounted a predetermined distance away from at least one other electrode in the group of electrodes.

36. A wearable defibrillator according to claim 35, wherein each electrode in the groups of electrodes includes electrically-conductive hydrogel at a surface thereof with contacts to the patient'"'"'s skin, the electrically-conductive hydrogel having a predetermined ion concentration.

37. A wearable defibrillator according to claim 36, wherein each non-electrically conductive pad includes therapeutic hydrogel at a surface thereof which contacts to the patient'"'"'s skin.

38. A wearable defibrillator according to claim 35, wherein each non-electrically conductive pad is flexible.

39. A wearable defibrillator according to claim 34, wherein the groups of electrodes are arrangeable on different areas of the patient in predetermined geometric patterns such that the defibrillation energy transmitted from the plurality of electrodes covers a predetermined area of the patient'"'"'s myocardium.

40. A wearable defibrillator according to claim 39, wherein the groups of electrodes in predetermined geometric patterns are movable relative to the patient such that the predetermined geometric patterns are substantially retained but are at different orientations relative to the patient.

41. A wearable defibrillator according to claim 34, wherein each of the plurality of segmented electrodes is shaped so that each electrode has a perimeter which is greater than a circumference corresponding to a radius of the electrode.

42. A wearable defibrillator according to claim 34, wherein the signal generator includes a power supply which supplies power to the signal generator so as to enable the signal generator to generate the defibrillation energy;

and

wherein each line corresponding to each group of electrodes is non-removably connected to the power supply.

43. A wearable defibrillator according to claim 42, wherein the power supply is sealed with a membrane.

44. A wearable defibrillator according to claim 34, further comprising:

a speaker for providing auditory messages to the patient; and

a controller for monitoring each of the segmented electrodes;

wherein the controller monitors a duration of use of each of the segmented electrodes and, when the controller determines that an electrode has been in use for greater than a predetermined period of time, the controller issues a signal to the speaker alerting the patient which electrode has been in use for greater than the predetermined period of time.

45. A wearable defibrillator according to claim 34, wherein each of the plurality of segmented electrodes is capable of transmitting defibrillation energy having a bi-phasic waveform.

46. A wearable defibrillator according to claim 34, wherein each of the plurality of segmented electrodes is capable of transmitting defibrillation energy having a truncated exponential waveform.

47. A wearable defibrillator according to claim 34, wherein each of the plurality of segmented electrodes is capable of transmitting defibrillation energy having a mono-phasic waveform.

48. A wearable defibrillator according to claim 34, wherein the segmented electrodes are separated from each other on the patient by between 0.5 and 3 times an effective diameter of each electrode.

49. A wearable defibrillator according to claim 34, wherein each of the segmented electrodes includes an adhesive on a surface thereof which contacts the patient'"'"'s skin.

50. A wearable defibrillator for delivering defibrillation energy to a patient, the defibrillator comprising:

an external interface, over which patient information is transmitted to an external location;

a patient interface, over which the defibrillation energy is transmitted to the patient, and over which the patient information is received;

a processor which analyzes the patient information received over the patient interface and which controls transmission of the defibrillation energy to the patient based on at least a first portion of the patient information; and

a memory which stores at least a second portion of the patient information prior to transmission of the second portion of the patient information over the external interface.

51. A wearable defibrillator according to claim 50, wherein the external interface is capable of interfacing to a base station, the base station for receiving the second portion of the patient information from the memory and for transmitting defibrillator programming information to the defibrillator via the external interface, the processor using the defibrillator programming information to reprogram the wearable defibrillator.

52. A wearable defibrillator according to claim 51, further comprising a power supply which supplies power to the wearable defibrillator and which is capable of interfacing to the external interface.

53. A wearable defibrillator according to claim 50, wherein the at least the second portion of the patient information comprises a log, for a predetermined period, which includes at least one of abnormal heart activity of the patient, an electrocardiogram of the patient, and artifact noise in the patient.

54. A wearable defibrillator according to claim 53, further comprising a user interface by which the user interacts with the wearable defibrillator;

wherein the memory further stores a response of the wearable defibrillator to the abnormal heart activity and information concerning patient interaction with the wearable defibrillator.

55. A wearable defibrillator according to claim 54, further comprising an accelerometer which the processor monitors to determine motion of the patient;

wherein the memory further stores data from the accelerometer relating to motion of the patient.

56. A wearable defibrillator according to claim 55, wherein the processor detects defibrillator operational errors and stores the defibrillator operational errors in the memory;

wherein the external interface is capable of interfacing to both a base station and a power supply; and

wherein, in a case that the external interface is interfaced to the base station, the processor transmits, over the external interface, the abnormal heart activity of the patient, the electrocardiogram of the patient, the artifact noise in the patient, the response of the wearable defibrillator to the abnormal heart activity, the information concerning patient interaction with the wearable defibrillator, the data from the accelerometer relating to motion of the patient, and the defibrillator operational errors.

57. A wearable defibrillator according to claim 50, wherein the external interface comprises a non-contact interface over which the patient information is transmitted to a personal computer.

58. A wearable defibrillator according to claim 57, wherein the patient information comprises an electrocardiogram and impedance information for the patient.

59. A wearable defibrillator according to claim 57, wherein the non-contact interface comprises an infrared (“

IR”

) interface.

60. A wearable defibrillator according to claim 57, wherein the non-contact interface comprises a radio frequency (“

RF”

) interface.

61. A wearable defibrillator according to claim 50, wherein the memory comprises a flash EPROM;

and

wherein the second portion of the patient information is stored in the flash EPROM as compressed data.

62. A wearable defibrillator according to claim 61, wherein the processor compresses data using a lossless compression technique.

63. A wearable defibrillator according to claim 50, wherein the patient interface comprises a plurality of sensing electrodes, the defibrillation energy has a bi-phasic waveform that is transmitted over each of the sensing electrodes, the first patient information comprises an electrocardiogram and thoracic impedance of the patient, and the second patient information comprises an operational history of the wearable defibrillator;

and

wherein both the first patient information and the second patient information are stored in the memory and both the first patient information and the second patient information are transmitted over the external interface.

64. A wearable defibrillator according to claim 50, further comprising one or more indicators which provide the patient with indications relating to at least one of the patient information and operability of the wearable defibrillator.

65. A wearable defibrillator according to claim 64, wherein the one or more indicators comprises an auditory indicator which provides the patient with auditory prompts for using the wearable defibrillator.

66. A wearable defibrillator according to claim 65, wherein at least one of the auditory prompts is provided in a case that the processor analyzes the patient information and determines that abnormal heart activity has occurred in the patient.

67. A wearable defibrillator according to claim 66, further comprising a user interface for providing a response signal to the processor in response to user activation;

wherein the processor waits a predetermined period of time after the at least one of the auditory prompts has been provided to the patient and, in a case that the processor does not detect the response signal, the processor causes immediate transmission of the defibrillation energy to the patient.

68. A wearable defibrillator according to claim 65, wherein the patient interface comprises one or more sensing electrodes which are attached to the patient;

wherein the patient information comprises electrode-to-skin impedance from the patient, the electrode-to-skin impedance from the patient being indicative of whether the one or more sensing electrodes is attached to the patient; and

wherein the processor causes the auditory indicator to provide an indication to the patient that the at least one electrode has become detached in a case that the electrode-to-skin impedance from the patient is below a predetermined level.

69. A wearable defibrillator according to claim 65, further comprising a power supply for supplying power to the wearable defibrillator;

wherein the processor monitors the power supply and causes the auditory indicator to provide an auditory message to the patient in a case that the power supply is below a predetermined level.

70. A wearable defibrillator according to claim 64, wherein the one or more indicators comprises a visual display and an auditory indicator which echos information displayed on the visual display.

71. A wearable defibrillator according to claim 50, further comprising a user interface for providing a response signal to the processor in response to user activation;

wherein the patient interface comprises at least one electrode which is capable of transmitting a tactile stimulation signal to the patient; and

wherein the processor waits a predetermined period of time after the tactile stimulation signal has been transmitted to the patient and, in a case that the processor does not detect the response signal, the processor causes transmission of the defibrillation energy to the patient.

72. A wearable defibrillator for delivering defibrillation energy to a patient, the defibrillator comprising:

a patient interface, over which patient information is received from the patient, and over which the defibrillation energy is transmitted to the patient; and

a processor which operates in a normal mode and a low-power consumption mode, wherein, during the normal mode, the processor receives the patient information and controls transmission of the defibrillation energy in accordance with the patient information.

73. A wearable defibrillator according to claim 72, wherein the processor enters the low-power consumption mode periodically for predetermined periods of time.

74. A wearable defibrillator according to claim 73, wherein the predetermined periods of time are variable based on the patient information.

75. A wearable defibrillator according to claim 74, further comprising a memory which stores a log of the patient information for a span of time;

wherein the processor varies the predetermined periods based on the log of patient information stored in the memory.

76. A wearable defibrillator according to claim 72, further comprising a user interface by which a user may place the processor in the normal mode manually.

77. A wearable defibrillator according to claim 72, further comprising a plurality of hardware components for use in outputting the defibrillation energy and for communicating with the patient;

wherein the processor causes each of the plurality of hardware components to be selectively powered-up and powered-down at predetermined time intervals.