Determination of the clinical state of a subject

• US 20060217614A1
• Filed: 03/24/2005
• Published: 09/28/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Takala, Panu, Huiku, Matti
• Granted Patent: US 8,715,193 B2
• Time in Patent Office: Days
• US Class Current: 600/481
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61B 5/4824 Touch or pain perception evaluation A61B5/4821 takes precedence

Abstract

The invention relates to the determination of the clinical state of a subject. In order to bring about an uncomplicated method for monitoring the clinical state of a subject and for accomplishing a diagnostic scale, such as a nociception scale, on which a certain reading corresponds to the same level for all patients, a normalization transform is applied to a measurement signal containing physiological data obtained from a patient, whereby a normalized measurement signal having a predetermined value range is obtained. The normalization transform is dependent on predetermined history data, such as previous signal data of said measurement signal. A diagnostic index dependent on the normalized measurement signal is then formed, the diagnostic index serving as a measure of the clinical state of the patient. The diagnostic index may be formed based on one or more normalized measurement signals.

Claims

1. A method for ascertaining a clinical state of a subject, the method comprising the steps of:

acquiring a first measurement signal containing desired of physiological data reflecting the clinical state of the subject;

applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previously acquired history data, whereby a first normalized measurement signal having a predetermined value range is obtained; and

forming a diagnostic index which is dependent on the first normalized measurement signal, the diagnostic index serving as a measure of the clinical state of the subject.

2. A method according to claim 1, wherein the forming step includes forming the diagnostic index, in which the diagnostic index is proportional to the first normalized measurement signal.

3. A method according to claim 2, wherein the forming step includes employing the first normalized measurement signal directly as the measure of the clinical state of the subject.

4. A method according to claim 1, wherein the previously acquired history data includes previous signal data of the first measurement signal.

5. A method according to claim 1, wherein the acquiring step, is further defined as acquiring a first measurement signal containing a first type of physiological data;

and previously acquired history data includes physiological data of the first type obtained from a group of subjects.

6. A method according to claim 1, wherein the acquiring step is further defined as acquiring a first measurement signal containing a first type of physiological data;

and previously acquired history data includes both previous physiological data of the first type from the first measurement signal and physiological data of the first type of obtained from a group of subjects.

7. A method according to claim 1, further comprising the steps of:

determining at least one subject-specific value for at least one predetermined parameter of the first measurement signal; and

substituting the at least one subject-specific value for at least one parameter in a predetermined parameterized transform to obtain the first normalization transform.

8. A method according to claim 1, wherein the applying step includes applying a histogram transform to the first measurement signal.

9. A method according to claim 8, wherein the applying step includes the sub-steps of:

forming an input array for the first measurement signal, the input array including a predetermined number of input elements storing input values sorted in a desired order;

creating an output array comprising output elements storing a predetermined number of index values sorted in a desired order;

for an incoming signal value of the first measurement signal, determining the input element that corresponds to said incoming signal value in the input array; and

transforming the incoming signal value to the index value stored in the output element corresponding to the determined input element.

10. A method according to claim 1, wherein the acquiring step includes a sub-step of deriving the first measurement signal from a first physiological signal indicative of the cardiovascular functioning of the subject.

11. A method according to claim 10, wherein the deriving sub-step includes deriving the first measurement signal from a first physiological signal comprising a plethysmographic signal measured from the subject.

12. A method according to claim 10, wherein the deriving sub-step includes deriving the first measurement signal from a first physiological signal comprising a blood pressure signal measured from the subject.

13. A method according to claim 10, wherein the forming step includes forming the diagnostic index, in which the diagnostic index serves as an index of nociception.

14. A method according to claim 10, wherein the deriving sub-step includes generating a time series indicative of the amplitude of the first physiological signal, the time series comprising the first measurement signal.

15. A method according to claim 13, further comprising a step of producing a second measurement signal containing signal data indicative of pulse intervals in a second physiological signal measured from the subject.

16. A method according to claim 15, further comprising a step of applying a second normalization transform to the second measurement signal, the second normalization transform being dependent on previously history data, whereby a second normalized measurement signal having a predetermined value range is obtained.

17. A method according to claim 16, wherein the forming step includes calculating a weighted average of the first normalized measurement signal and the second normalized measurement signal.

18. A method according to claim 15, wherein the second physiological signal is indicative of the cardiovascular functioning of the subject.

19. A method according to claim 18, wherein the second physiological signal and said first physiological signal are the same.

20. A method according to claim 15, further comprising a step of producing a third measurement signal containing signal data indicative of variability in a third physiological signal obtained from the subject.

21. A method according to claim 20, further comprising a step of applying a third normalization transform to the third measurement signal, whereby a third normalized measurement signal having a predetermined value range is obtained.

22. A method according to claim 21, wherein the forming step includes calculating a weighted average of the first normalized measurement signal, the second normalized measurement signal, and the third normalized measurement signal.

23. A method according to claim 22, further comprising a step of selecting a temporally invariant transform as the third normalization transform.

24. A method according to claim 20, wherein the third physiological signal is indicative of the cardiovascular functioning of the subject.

25. A method according to claim 24, wherein the third physiological signal and said first physiological signal are the same.

26. A method according to claim 24, wherein the third physiological signal and said second physiological signal are the same.

27. A method according to claim 15, further comprising a step of producing a third measurement signal containing signal data indicative of the respiration rate of the subject.

28. A method according to claim 27, further comprising a step of applying a third normalization transform to the third measurement signal, whereby a third normalized measurement signal having a predetermined value range is obtained.

29. A method according to claim 28, wherein the forming step includes calculating a weighted average of the first normalized measurement signal, the second normalized measurement signal, and the third normalized measurement signal.

30. A method according to claim 21, further comprising a step of producing a fourth measurement signal containing signal data indicative of the respiration rate of the subject.

31. A method according to claim 30, further comprising a step of applying a fourth normalization transform to the fourth measurement signal, whereby a fourth normalized measurement signal having a predetermined value range is obtained.

32. A method according to claim 31, wherein the forming step includes calculating a weighted average of the first, second, third and fourth normalized measurement signals.

33. A method according to claim 1, further comprising a step of determining, based on the diagnostic index, at least one reference value serving as an instruction for administering a drug to the subject.

34. A method according to claim 13, further comprising a step of controlling administration of at least one analgesic drug to the patient, the controlling step being performed based on the index of nociception.

35. An apparatus for ascertaining a clinical state of a subject, the apparatus comprising:

means for acquiring a first measurement signal containing desired physiological information data reflecting the clinical state of the subject;

first transform means for applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previously acquired history data, whereby the first transform means are configured to output a first normalized measurement signal having a predetermined value range; and

indicator means for indicating the clinical state of the subject as an index which is dependent on the first normalized measurement signal.

36. An apparatus according to claim 35, wherein the index is proportional to the first normalized measurement signal.

37. An apparatus according to claim 35, wherein the previously acquired history data includes previous signal data of the first measurement signal.

38. An apparatus according to claim 35, wherein the first measurement signal contains a first type of physiological data and the previously acquired history data includes the physiological data of the first type obtained from a group of subjects.

39. An apparatus according to claim 35, wherein the first measurement signal contains a first type of physiological data and the previously acquired history data includes both previous physiological data of the first type from the first measurement signal and physiological data of the first type obtained from a group of subjects.

40. An apparatus according to claim 35, wherein the indicator means are configured to indicate the value of the first measurement signal as said index.

41. An apparatus according to claim 35, further comprising:

measurement means for determining at least one subject-specific value for at least one predetermined parameter of the first measurement signal; and

means for substituting the at least one subject-specific value for at least one parameter in a predetermined parameterized transform to obtain the first normalization transform.

42. An apparatus according to claim 35, wherein the first transform means are configured to apply a histogram transform to the first measurement signal.

43. An apparatus according to claim 42, wherein the first transform means are provided with

an input array for the first measurement signal, the input array including a predetermined number of input elements storing input values;

and

an output array comprising output elements storing a predetermined number of index values sorted in a desired order.

44. An apparatus according to claim 43, wherein the first transform means are further provided with means for sorting the input values in a desired order.

45. An apparatus according to claim 35, wherein said means for acquiring the first measurement signal are configured to derive the first measurement signal from a first physiological signal indicative of the cardiovascular functioning of the subject.

46. An apparatus according to claim 45, wherein said index serves as an index of nociception.

47. An apparatus according to claim 45, further comprising means for producing a second measurement signal containing signal data indicative of pulse intervals in a second physiological signal obtained from the subject.

48. An apparatus according to claim 47, further comprising second transform means for applying a second normalization transform to the second measurement signal, the second normalization transform being dependent on previously acquired history data, whereby the second transform means are configured to output a second normalized measurement signal having a predetermined value range.

49. An apparatus according to claim 48, wherein the previously acquired history data includes previous signal data of said second measurement signal.

50. An apparatus according to claim 48, further comprising first calculation means for calculating a weighted average of the first normalized measurement signal and the second normalized measurement signal.

51. An apparatus according to claim 50, wherein the indicator means are configured to indicate the weighted average as said index.

52. An apparatus according to claim 49, further comprising means for producing a third measurement signal containing signal data indicative of variability in a third physiological signal obtained from the subject.

53. An apparatus according to claim 52, further comprising third transform means for applying a third normalization transform to the third measurement signal, wherein the third transform means are configured to output a third normalized measurement signal having a predetermined value range.

54. An apparatus according to claim 52, wherein at least two of the first, second, and third physiological signals are the same signal.

55. An apparatus according to claim 53, further comprising second calculation means for calculating a weighted average of the first normalized measurement signal, the second normalized measurement signal, and the third normalized measurement signal.

56. An apparatus according to claim 55, wherein the indicator means are configured to indicate the weighted average as said index.

57. An apparatus according to claim 53, wherein the third transform means are configured to select a temporally invariant transform as the third normalization transform.

58. An apparatus according to claim 48, further comprising means for producing a third measurement signal containing signal data indicative of the respiration rate of the subject.

59. An apparatus according to claim 58, further comprising third transform means for applying a third normalization transform to the third measurement signal, wherein the third transform means are configured to output a third normalized measurement signal having a predetermined value range.

60. An apparatus according to claim 59, further comprising second calculation means for calculating a weighted average of the first normalized measurement signal, the second normalized measurement signal, and the third normalized measurement signal.

61. An apparatus according to claim 59, further comprising means for producing a fourth measurement signal containing signal data indicative of variability in a third physiological signal obtained from the subject.

62. An apparatus according to claim 61, further comprising fourth transform means for applying a fourth normalization transform to the fourth measurement signal, wherein the fourth transform means are configured to output a fourth normalized measurement signal having a predetermined value range.

63. An apparatus according to claim 53, further comprising means for producing a fourth measurement signal containing signal data indicative of variability in a third physiological signal obtained from the subject;

fourth transform means for applying a fourth normalization transform to the fourth measurement signal to output a fourth normalized measurement signal; and

second calculation means for calculating a weighted average of the first, second, third, and fourth normalized measurement signals.

64. An apparatus according to claim 46, further comprising control means for controlling administration of at least one analgesic drug to the patient based on the index of nociception.

65. An apparatus for ascertaining a Clinical state of a subject, the apparatus comprising:

a measurement unit configured to acquire a first measurement signal from a subject, the first measurement signal containing desired physiological data reflecting the clinical state of the subject;

a data processing unit configured to apply a first normalization transform to the first measurement signal, the first normalization transform being dependent on previously acquired history data, wherein the data processing unit is configured to output a first normalized measurement signal having a predetermined value range; and

a display unit configured to display the clinical state of the subject as an index dependent on the first normalized measurement signal.

66. An apparatus according to claim 65, wherein the previously acquired history data includes previous signal data of the first measurement signal.

67. An apparatus according to claim 65, wherein the previously acquired history data includes physiological data obtained from a group of subjects.

68. An apparatus according to claim 65, wherein the predetermined history data includes both previous signal data of the first measurement signal and physiological data obtained from a group of subjects.

69. A computer program product for ascertaining a clinical state of a subject, the computer program product comprising:

a first program code portion configured to retrieve physiological data reflecting the clinical state of the subject;

a second program code portion configured to apply a first normalization transform to the physiological data, wherein the second program code portion is configured to output a first normalized measurement signal having a predetermined value range; and

a third program code portion configured to indicate the clinical state of the subject as an index which is dependent on the first normalized measurement signal.

70. A method for controlling a clinical state of a subject, the method comprising the steps of:

acquiring a first measurement signal containing physiological data reflecting the clinical state of the subject;

applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previously acquired history data, whereby a first normalized measurement signal having a predetermined value range is obtained;

forming a diagnostic index which is dependent on the first normalized measurement signal, the diagnostic index serving as a measure of the clinical state of the subject; and

controlling administration of at least one drug to the patient, the controlling step being performed based on the diagnostic index.

71. A method according to claim 70, wherein

the forming step includes forming the diagnostic index, in which the diagnostic index serves as an index of nociception;

and

the controlling step includes controlling the administration of the at least one drug to the patient, wherein the at least one drug is an analgesic drug.

72. A method according to claim 71, wherein the forming step includes forming the diagnostic index, in which the diagnostic index is proportional to the first normalized measurement signal.

74. A system according to claim 72, wherein the at least one drug is an analgesic drug.

73. A system for controlling a Clinical state of a subject, the system comprising:

means for acquiring a first measurement signal containing first physiological data reflecting the clinical state of the subject;

first transform means for applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previously acquired history data, whereby the first transform means are configured to output a first normalized measurement signal having a predetermined value range;

drug delivery means for administering at least one drug to the patient; and

control means for controlling the drug delivery means based on an index dependent which is on the first normalized measurement signal.