Selecting electrotherapy dosage

• US 20040111124A1
• Filed: 12/04/2002
• Published: 06/10/2004
• Est. Priority Date: 12/04/2002
• Status: Active Grant

• Current Assignee: Physio-Control Incorporated (Stryker Corporation)
• Original Assignee: Medtronic Emergency Response Systems Inc (Stryker Corporation)
• Inventors: Sullivan, Joseph L., Walker, Robert G.
• Granted Patent: US 7,047,072 B2
• Time in Patent Office: Days
• US Class Current: 607/7
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A dosage for electrotherapy delivered to a patient, such as a defibrillation pulse delivered by an external defibrillator, is selected based on an age-related classification, such as adult or child, and a measured electrical parameter, such as the transthoracic impedance, of the patient. For example, a nominal voltage level for an energy storage circuit may be determined based on a nominal dosage. The nominal voltage level may be adjusted by applying a function that relates voltage level adjustment to impedance to the measured impedance. The function may be selected based on the age-related classification of the patient. The dosage of the defibrillation pulse delivered based on the adjusted voltage level, i.e., the selected dosage, may have a substantially equivalent probability of success for the patient as the nominal dosage would provide for a reference patient with an average transthoracic impedance for the class of which the patient is a member.

Claims

1. A method comprising:

selecting a dosage based on an age-related classification of a patient and a measured electrical parameter of the patient; and

delivering electrotherapy at the selected dosage to the patient.

2. The method of claim 1, in which selecting a dosage comprises receiving an indication of the age-related classification of the patient.

3. The method of claim 2, in which selecting a dosage comprises determining whether the patient is one of a child and an adult based on the received indication.

4. The method of claim 2, in which receiving an indication of the age-related classification comprises receiving an input from a user that indicates the classification.

5. The method of claim 2, in which receiving an indication of the age-related classification comprises:

detecting an electrode type; and

determining the age-related classification based on the electrode type.

6. The method of claim 2, in which receiving an indication of the age-related classification comprises:

receiving a nominal dosage selected by a user; and

determining the age-related classification based on the nominal dosage.

7. The method of claim 6, in which determining the age-related classification based on the nominal dosage comprises:

comparing the nominal dosage to a threshold value; and

identifying the patient as one of a child and an adult based on the comparison.

8. The method of claim 7, in which the threshold value is approximately 30 joules.

9. The method of claim 1, in which selecting a dosage includes:

identifying a nominal dosage; and

adjusting the nominal dosage based on the age-related classification and the measured impedance

10. The method of claim 9, in which identifying a nominal dosage comprises receiving a dosage selected by a user.

11. The method of claim 9, in which identifying a nominal dosage comprises:

storing preprogrammed progressions of dosages;

selecting one of the preprogrammed progressions based on the age-related classification; and

selecting a dosage from the selected progression.

12. The method of claim 9, in which adjusting the identified energy level comprises:

determining a nominal voltage level based on the nominal dosage;

adjusting the nominal voltage level; and

charging an energy storage circuit to the adjusted voltage level.

13. The method of claim 12, in which adjusting the nominal voltage level comprises:

selecting one of a set of functions that describe relationships between the electrical parameter and voltage level adjustment based on the age-related classification;

applying the selected function to the measured electrical parameter to determine a voltage level adjustment; and

adjusting the nominal voltage level as a function of the determined voltage adjustment.

14. The method of claim 13, in which selecting one of a set of functions comprises selecting one of a set that includes at least one of equations and look-up tables.

15. The method of claim 13, in which selecting one of a set of functions comprises:

determining whether the patient is one of a child and an adult; and

selecting one of a first function and a second function from the set based on the determination.

16. The method of claim 13, in which the patient comprises a first patient, the nominal dosage comprises a first nominal dosage, and the electrotherapy delivered to the patient comprises a first electrotherapy, the method further comprising:

identifying a second nominal dosage;

determining whether a current patient is the first patient;

applying the selected function to adjust the second nominal dosage based on the determination; and

delivering a second electrotherapy at the adjusted second dosage to the current patient.

17. The method of claim 9, in which selecting a dosage comprises selecting a dosage to provide a first probability of successful electrotherapy for the patient based on the measured electrical parameter that is substantially equivalent to a second probability of successful electrotherapy provided by the nominal dosage based on an average value for the electrical parameter that corresponds to the age-related classification of the patient.

18. The method of claim 9, in which selecting a dosage comprises selecting a dosage that is one of greater than the nominal dosage if the measured electrical parameter is greater than an average value of the electrical parameter for the age-related classification, less than the nominal dosage if the measured electrical parameter is less than the average value, and equal to the nominal dosage if the measured electrical parameter is equal to the average value.

19. The method of claim 1, in which selecting a dosage comprises selecting an energy level for a defibrillation pulse, and delivering electrotherapy comprises delivering the defibrillation pulse.

20. The method of claim 1, in which the measured electrical parameter comprises a measured transthoracic impedance.

21. A device comprising:

a set of electrodes for coupling to a patient;

a measuring circuit that measures an electrical parameter of the patient via the electrodes; and

a processor to select a dosage based on an age-related classification of the patient and the measured electrical parameter, and control delivery of electrotherapy at the selected dosage to the patient via the electrodes.

22. The device of claim 21, in which the processor determines whether the patient is one of a child and an adult.

23. The device of claim 21, further comprising a user interface, wherein the processor receives an indication of the age-related classification of the patient from a user via the user interface.

24. The device of claim 21, further comprising an interface circuit to couple the electrode set to the processor, wherein the processor detects an electrode set type via the interface circuit and determines the age-related classification of the patient based on the electrode set type.

25. The device of claim 21, further comprising a user interface, wherein the processor receives a nominal dosage selected by a user via the user interface and determines the age-related classification of the patient based on the nominal dosage.

26. The device of claim 25, further comprising a memory to store a threshold value, wherein the processor determines the age-related classification of the patient by comparing the nominal dosage to the threshold value and identifying the patient as one of a child and an adult based on the comparison.

27. The device of claim 26, in which the threshold value is approximately 30 joules.

28. The device of claim 21, in which the processor selects a dosage by identifying a nominal dosage and adjusting the nominal dosage based on the age-related classification and the measured electrical parameter.

29. The device of claim 28, further comprising a user interface, wherein the processor identifies the nominal dosage by receiving a dosage selected by a user via the user interface.

30. The device of claim 28, further comprising a memory to store preprogrammed progressions of dosages, wherein the processor identifies the nominal dosage by selecting one of the preprogrammed progressions based on the age-related classification of the patient and selecting a dosage from the selected progression.

31. The device of claim 28, further comprising an energy storage circuit to store energy for delivery of the electrotherapy to the patient, wherein the processor adjusts the nominal dosage by determining a nominal voltage level that corresponds to the nominal dosage, adjusting the nominal voltage level, and controlling the charging of the energy storage circuit to the adjusted voltage level.

32. The device of claim 31, further comprising a memory to store a set of functions that describe relationships between voltage level adjustment and the electrical parameter, wherein the processor adjusts the nominal voltage level by selecting one of the set of functions based on the age-related classification of the patient, applying the selected function to the measured electrical parameter to determine a voltage level adjustment, and adjusting the nominal voltage level as a function of the determined voltage level adjustment.

33. The device of claim 32, in which the set of functions within the memory includes at least one of equations and look-up tables.

34. The device of claim 32, in which the processor selects one of a set of functions by determining whether the patient is one of a child and an adult and selecting one of a first function and a second function based on the determination.

35. The device of claim 32, in which the patient comprises a first patient, the nominal dosage comprises a first nominal dosage, the electrotherapy delivered to the patient comprises a first electrotherapy, and the processor identifies a second nominal dosage, determines whether a current patient is the first patient, applies the selected function to adjust the second nominal dosage based on the determination, and controls the delivery of a second electrotherapy at the adjusted second nominal dosage to the current patient.

36. The device of claim 28, in which the processor selects the dosage to provide a first probability of successful electrotherapy for the patient based on the measured electrical parameter that is substantially equivalent to a second probability of successful electrotherapy provided by the nominal dosage based on an average value for the electrical parameter that corresponds to the age-related classification of the patient.

37. The device of claim 28, in which the processor selects a dosage by selecting a dosage that is one of greater than the nominal dosage if the measured electrical parameter is greater than an average value of the electrical parameter for the age-related classification, less than the nominal dosage if the measured electrical parameter is less than the average value, and equal to the nominal dosage if the measured electrical parameter is equal to the average value.

38. The device of claim 21, in which the device comprises an external defibrillator, the processor selects a dosage by selecting an energy level for a defibrillation pulse, and the processor delivers electrotherapy by delivering the defibrillation pulse.

39. The device of claim 21, in which the measuring circuit comprises an impedance measuring circuit, and the measured electrical parameter comprises a measured transthoracic impedance.

40. A computer-readable medium comprising instructions that cause a processor to:

select a dosage based on an age-related classification of a patient and a measured electrical parameter of the patient; and

control the delivery of electrotherapy at the selected dosage to the patient.

41. The computer-readable medium of claim 40, in which the instructions that cause a processor to select a dosage comprise instructions that cause a processor to receive an indication of the age-related classification of the patient.

42. The computer-readable medium of claim 41, in which the instructions that cause a processor to select a dosage comprise instructions that cause a processor to determine whether the patient is one of a child and an adult based on the received indication.

43. The computer-readable medium of claim 41, in which the instructions that cause a processor to receive an indication of the age-related classification comprise instructions that cause a processor to receive an input from a user that indicates the classification.

44. The computer-readable medium of claim 41, in which the instructions that cause a processor to receive an indication of the age-related classification comprise instructions that cause a processor to:

detect an electrode type; and

determine the age-related classification based on the electrode type.

45. The computer-readable medium of claim 41, in which the instructions that cause a processor to receive an indication of the age-related classification comprise instructions that cause a processor to:

receive a nominal dosage selected by a user; and

determine the age-related classification based on the nominal dosage.

46. The computer-readable medium of claim 40, in which the instructions that cause a processor to select an energy level comprise instructions that cause a processor to:

identify a nominal dosage; and

adjust the nominal dosage based on the age-related classification and the measured electrical parameter.

47. The computer-readable medium of claim 46, in which the instructions that cause a processor to identify a nominal dosage comprise instructions that cause a processor to receive a dosage selected by a user.

48. The computer-readable medium of claim 46, in which the instructions that cause a processor to identify a nominal dosage comprise instructions that cause a processor to:

store preprogrammed progressions of dosages;

select one of the preprogrammed progressions based on the age-related classification of the patient; and

select a dosage from the selected progression.

49. The computer-readable medium of claim 46, in which the instructions that cause a processor to adjust the nominal dosage comprise instructions that cause a processor to:

determine a nominal voltage level based on the nominal dosage;

adjust the nominal voltage level; and

control the charging of an energy storage circuit to the adjusted voltage level.

50. The computer-readable medium of claim 49, in which the instructions that cause a processor to adjust the voltage value comprise instructions that cause a processor to:

select one of a set of functions that describe relationships between the electrical parameter and voltage level adjustment based on the age-related classification;

apply the selected function to the measured electrical parameter to determine a voltage level adjustment; and

adjust the nominal voltage level as a function of the determined voltage level adjustment.

51. A method comprising:

receiving an indication of an age-related classification of a patient;

measuring an impedance of the patient;

selectively applying one of a set of functions to the measured impedance based on the indicated age-related classification to determine a voltage level adjustment;

identifying a nominal defibrillation pulse energy level;

determining a nominal voltage level based on the nominal defibrillation pulse energy level;

adjusting the nominal voltage level as a function of the determined voltage level adjustment; and

delivering a defibrillation pulse at an energy level that is a function of the adjusted voltage level to the patient.

52. The method of claim 51, in which the set of functions includes at least one of equations and look-up tables.

53. The method of claim 51, in which receiving an indication of an age-related classification comprises determining whether the patient is one of a child and an adult based on the indication, and selectively applying one of a set of functions comprises:

selecting one of a first function and a second function from the set based on the determination; and

applying the selected function to the measured impedance.

54. A method comprising:

creating a model that describes a relationship between voltage level, impedance, and cardiac response;

determining average impedance values for each of a plurality of age-related classifications of patients; and

determining a function that describes a relationship between voltage level adjustment and impedance for each of the classifications based on the model and the average impedance for the classification.

55. The method of claim 54, further comprising:

storing a set of the determined functions in memory;

receiving an indication of an age-related classification of a patient;

selecting one of the set of functions based on the indicated age-related classification;

measuring an impedance of the patient;

applying the selected function to the measured impedance to determine a voltage level adjustment;

identifying a nominal defibrillation pulse energy level;

determining a nominal voltage level that corresponds to the nominal defibrillation pulse energy level;

adjusting the nominal voltage level as a function of the determined voltage level adjustment.

delivering a defibrillation pulse at an energy level that is a function of the adjusted voltage level to the patient.

56. The method of claim 55, in which the set includes a first functions for children and a second function for adults, receiving an indication of an age-related classification of a patient comprises determining whether the patient is one of a child and an adult, and selecting a function comprises selecting one of the first and second function based on the determination.

57. A method comprising:

identifying a nominal dosage;

selecting a dosage based on a measured electrical parameter of a patient that is a child and the nominal dosage to provide a first probability of successful electrotherapy for the patient based on the measured electrical parameter that is substantially equivalent to a second probability of successful electrotherapy provided by the nominal dosage based on an average value for the electrical parameter for children; and

delivering electrotherapy at the selected dosage to the patient.

58. The method of claim 57, in which selecting a dosage comprises selecting an energy level for a defibrillation pulse, and delivering electrotherapy comprises delivering the defibrillation pulse.

59. The method of claim 57, in which the measured electrical parameter comprises a measured transthoracic impedance.

60. A method comprising:

identifying a nominal dosage;

selecting a dosage based on a measured electrical parameter of a patient that is a child and the nominal dosage; and

delivering electrotherapy at the selected dosage to the patient, in which selecting a dosage comprises selecting a dosage that is one of greater than the nominal dosage if the measured electrical parameter is greater than an average value of the electrical parameter for children, less than the nominal dosage if the measured electrical parameter is less than the average value, and equal to the nominal dosage if the measured electrical parameter is equal to the average value.

61. The method of claim 60, in which selecting a dosage comprises selecting an energy level for a defibrillation pulse, and delivering electrotherapy comprises delivering the defibrillation pulse.

62. The method of claim 60, in which the measured electrical parameter comprises a measured transthoracic impedance.