Real-time monitoring of the state of the autonomous nervous system of a patient

• US 20060074333A1
• Filed: 09/29/2004
• Published: 04/06/2006
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Instrumentarium Dental Incorporated (Envista Holdings Corporation)
• Original Assignee: Instrumentarium Dental Incorporated (Envista Holdings Corporation)
• Inventors: Huiku, Matti
• Granted Patent: US 7,553,286 B2
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• 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 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system

Abstract

The invention relates to a method and arrangement for monitoring the state of the autonomous nervous system (ANS) of a patient. A first measurement signal is acquired from a patient, the first measurement signal representing a physiological signal measured from the patient. In order to enable real-time monitoring of the state of the ANS, a second measurement signal indicative of a respiration rhythm of the patient is acquired and at least one indicator signal is generated by means of the first and second measurement signals. The at least one indicator signal may then be used to obtain an indication of the state of the autonomous nervous system of the patient.

Claims

1. A method for monitoring the state of the autonomous nervous system of a patient, the method comprising the steps of:

acquiring a first measurement signal from a patient, the first measurement signal representing a physiological signal measured from the patient;

obtaining a second measurement signal indicative of a respiration rhythm of the patient; and

generating, based on the first and second measurement signals, at least one indicator signal for obtaining an indication of the state of the autonomous nervous system of the patient.

2. A method according to claim 1, wherein the generating step includes generating the at least one indicator signal, the at least one indicator signal being indicative of respiration modulation in the first measurement signal.

3. A method according to claim 1, wherein the generating step includes generating the at least one indicator signal, the at least one indicator signal being indicative of irregularity of respiration modulation in the first measurement signal.

4. A method according to claim 1, wherein the generating step includes dividing the first measurement signal into a low frequency component and to a residual signal.

5. A method according to claim 1, further comprising a step of deriving, based on the second measurement signal, at least one respiration-locked time series of the first measurement signal, the respiration-locked time series being locked to the respiration rhythm of the patient.

6. A method according to claim 4, further comprising a step of deriving, based on the second measurement signal, at least one respiration-locked time series of the first measurement signal, the respiration-locked time series being locked to the respiration rhythm of the patient.

7. A method according to claim 5, wherein the generating step includes deriving a difference time series, the difference time series including a predetermined number of difference values for each respiration cycle of the patient, each difference value representing the difference of two signal values which are one respiration cycle apart in the respiration-locked time series of the first measurement signal.

8. A method according to claim 7, wherein the generating step includes a step of defining a low frequency component of the first measurement signal based on the difference time series, the low frequency component serving as the at least one indicator signal.

9. A method according to claim 5, wherein the generating step includes calculating a correlation value between a first and second instance of the respiration-locked time series of the first measurement signal, wherein the first instance includes L latest signal values in the first measurement signal and the second instance includes L latest signal values in the first measurement signal delayed by an integer number of respiration cycles.

10. A method according to claim 7, wherein the generating step further includes calculating a variance for a predetermined number of difference values.

11. A method according to claim 8, wherein the defining step includes summing the difference values, thereby forming a time series representing the low frequency component of the first measurement signal.

12. A method according to claim 8, wherein the defining step includes:

filtering the difference values to form a time series of filtered difference values; and

summing the filtered difference values, thereby forming a time series representing the low frequency component of the first measurement signal.

13. A method according to claim 4, wherein the obtaining step includes obtaining the second measurement signal, the second measurement signal indicating the respiration rate of the patient.

14. A method according to claim 13, wherein the generating step includes controlling a filter bandwidth by means of the second measurement signal.

15. A method according to claim 4, wherein the generating step further includes dividing the residual signal into a regular signal component and an irregular signal component, wherein the regular signal component remains substantially constant from one respiration cycle to another and the irregular signal component varies from one respiration cycle to another.

16. A method according to claim 4, wherein the generating step further includes a sub-step of dividing the residual signal into a high frequency component and to a beat-to-beat component caused by beat-to-beat variations in the physiological signal.

17. A method according to claim 1, wherein the acquiring step includes the steps of:

measuring the physiological signal from the patient; and

calculating a time derivated signal of the physiological signal, the time derivated signal being the first measurement signal.

18. A method according to claim 1, wherein the acquiring step includes the steps of:

measuring the physiological signal from the patient; and

calculating a normalized signal of the physiological signal, the normalized signal being the first measurement signal.

19. A method according to claim 1, wherein in the acquiring step includes the steps of:

measuring the physiological signal from the patient;

calculating a time derivated signal of the physiological signal; and

calculating a normalized signal of the time derivated signal, the normalized signal being the first measurement signal.

20. A method according to claim 6, wherein the generating step includes forming the residual signal by subtracting the time series representing the low frequency component from the respiration-locked time series of the first measurement signal.

21. A method according to claim 4, further comprising a step of filtering the residual signal to obtain a high frequency component of the first measurement signal.

22. A method according to claim 1, further comprising a step of determining, based on the at least one indicator signal, a sympatho-vagal balance of the patient.

23. A method according to claim 1, further comprising a step of determining, based on the at least one indicator signal, a first variable representing power of sympathetical activation of the autonomous nervous system and a second variable representing power of a signal component representing regular respiration modulation in the first measurement signal.

24. A method according to claim 1, further comprising a step of determining, based on the at least one indicator signal, an index indicative of adequacy of analgesia.

25. A method according to claim 1, further comprising a step of determining, based on the at least one indicator signal, an index indicative of depth of anesthesia.

26. A method according to claim 1, wherein the obtaining step includes obtaining the second measurement signal from a respirator.

27. A method according to claim 1, wherein the obtaining step includes obtaining the second measurement signal from a transducer attached to the patient.

28. A method according to claim 5, wherein deriving step comprises deriving the at least one respiration-locked time series, in which the at least one respiration-locked time series includes a predetermined number of signal values for each respiration cycle of the patient and information about the respiration rhythm of the patient.

29. An arrangement for monitoring the state of the autonomous nervous system of a patient, the arrangement comprising:

first means for acquiring a first measurement signal from a patient, the first measurement signal representing a physiological signal measured from the patient;

second means for obtaining a second measurement signal indicative of a respiration rhythm of the patient; and

third means for generating, by means of the first and second measurement signals, at least one indicator signal for obtaining an indication of the state of the autonomous nervous system of the patient.

30. An arrangement according to claim 29, wherein the at least one indicator signal is indicative of respiration modulation in the first measurement signal.

31. An arrangement according to claim 29, wherein the at least one indicator signal is indicative of irregularity of respiration modulation in the first measurement signal.

32. An arrangement according to claim 29, further comprising fourth means for deriving, based on the second measurement signal, at least one respiration-locked time series of the first measurement signal, the respiration-locked time series being locked to the respiration rhythm of the patient.

33. An arrangement according to claim 32, wherein the third means are configured to derive a difference time series, the difference time series including a predetermined number of difference values for each respiration cycle, each difference value representing the difference of two signal values, which are one respiration cycle apart in the respiration-locked time series of the first measurement signal.

34. An arrangement according to claim 32, wherein the third means are configured to calculate a correlation value between a first and second instance of the respiration-locked time series of the first measurement signal, wherein the first instance includes L latest signal values in the first measurement signal and the second instance includes L latest signal values in the first measurement signal delayed by one respiration cycle.

35. An arrangement according to claim 33, wherein the third means are further configured to calculate a variance value based on a predetermined number of difference values.

36. An arrangement according to claim 33, wherein the third means are further configured to filter the difference values for obtaining filtered difference values, to form a time series of the filtered difference values, and to sum the filtered difference values.

37. An arrangement according to claim 29, further comprising means for calculating a sympatho-vagal balance based on the at least one indicator signal.

38. An arrangement for monitoring the state of the autonomous nervous system of a patient, the arrangement comprising:

a measurement device configured to acquire a first measurement signal from a patient, the first measurement signal representing a physiological signal measured from the patient;

an input configured to receive a second measurement signal indicative of respiration rhythm of the patient;

a first controller configured to generate, by means of the first and second measurement signals, at least one indicator signal to obtain an indication of the state of the autonomous nervous system of the patient.

39. An arrangement according to claim 38, further comprising a second controller configured to provide an indication of the state of the autonomous nervous system of the patient based on the at least one indicator signal.

40. A computer program embodied on a computer-readable medium for monitoring the state of the autonomous nervous system of a patient, the computer-readable program code comprising:

a first computer-readable program code portion for receiving first measurement signal data, the first measurement signal data representing a physiological signal measured from the patient;

a second computer-readable program code portion for receiving second measurement signal data indicative of a respiration rhythm of the patient; and

a third computer-readable program code portion for generating, by means of the first and second measurement signal data, at least one indicator signal for obtaining an indication of the state of the autonomous nervous system of the patient.