Apparatus and method for time dependent power spectrum analysis of physiological signals

• US 5,797,840 A
• Filed: 02/28/1997
• Issued: 08/25/1998
• Est. Priority Date: 09/14/1994
• Status: Expired due to Fees

• Current Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Original Assignee: Ramot University Authority For Applied Research and Industrial Development Limited
• Inventors: Akselrod, Solange, Keselbrener, Laurence
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/793,583
• Time in Patent Office: 543 Days
• Field of Search: 600/300, 600/301, 600/483, 600/484
• US Class Current: 600/301
• CPC Class Codes: A61B 5/00 Measuring for diagnostic purposes radiation diagnosis A61B6/00; diagnosis by ultrasonic, sonic or infrasonic waves A61B8/00; Identification of persons
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• 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 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system. The apparatus includes a sensor for picking up a physiological signal modulated by the autonomic nervous system and a frequency selection apparatus for selecting at least one frequency inherent to the signal. The apparatus further includes a selective windowed time-frequency analysis processor for determining the power spectrum of the physiological signal within a window along the signal for the at least one frequency and an output apparatus for providing information associated with the functioning of the autonoinic nervous system as provided by the power spectrum of the physiological signal.

Claims

1. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency, said processor calculates the duration of said window as a function of said at least one frequency, thereby enabling the analysis of signals under non-steady state conditions; and

(d) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

2. The apparatus as in claim 1, wherein said sensor comprises one of the following:

an ECG recorder, a respiratory monitor, a blood pressure transducer, a Doppler flow meter, a tachometer, a finger plesthysmograph, a skin resistance galvanometer, cardiovascular monitoring equipment.

3. The apparatus as in claim 1, wherein said window has an aperture selected from one of the following:

a rectangular aperture, a Hamming aperture, a Hanning aperture, a Blackman aperture, a Gaussian window, a Lorentzian window, a sinc window, a power of a sine window and a power of a cosine window.

4. The apparatus as in claim 1, further comprising frequency selection apparatus for determining the frequency resolution of the apparatus.

5. The apparatus as in claim 1, further comprising timing selection apparatus for determining the time resolution of the apparatus.

6. The apparatus as in claim 1, further comprising a physiological signal selector for selecting the type of physiological signal picked up said sensor.

7. The apparatus as in claim 1, further comprising a type of perturbation selector for selecting the type of perturbation to be applied to a subject under investigation.

8. The apparatus as in claim 1, further comprising at least one frequency register for determining the range of frequency outputted on said output apparatus.

9. The apparatus as in claim 1, further comprising at least one timer for determining the onset and termination of the time dependent power spectrum of the physiological signal outputted on said output apparatus.

10. The apparatus as in claim 1, further comprising a detrending filter deployed between said sensor and said selective windowed time-frequency analysis processor.

11. The apparatus as in claim 1, wherein said selective windowed time-frequency analysis processor comprises a Wavelet processor.

12. The apparatus as in claim 11, further comprising a prototype function selector for selecting a prototype function applied by said Wavelet processor.

13. The apparatus as in claim 11, further comprising a scale parameters selector for selecting scale parameters applied by said Wavelet processor.

14. The apparatus as in claim 11, further comprising a shift parameters selector for selecting shift parameters applied by said Wavelet processor.

15. The apparatus as in claim 1, wherein said selective windowed time-frequency analysis processor comprises a selective discrete spectral transform algorithm processor.

16. The apparatus as in claim 15, further comprising a spectral transform selector for selecting a transform selected from one of the following:

the Fourier transform, the Haar transform, the Hartley transform, the sine transform, the cosine transform, and the Hadamard transform.

17. The apparatus as in claim 15, further comprising a window duration selector for selecting the duration of said window.

18. The apparatus as in claim 15, further comprising a window aperture selector for selecting the aperture of said window.

19. The apparatus as in claim 15, further comprising a number of points selector for selecting the number of data points within said window.

20. The apparatus as in claim 15, further comprising a decimation technique selector for selecting the decimation technique applied by said selective discrete spectral transform analysis processor.

21. A method of time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the method comprising the steps of:

(a) picking up a physiological signal modulated by the autonomic nervous system;

(b) selecting at least one frequency inherent to the signal;

(c) determining the power spectrum of the physiological signal within a window along said signal for the at least one frequency by using a selective windowed time frequency analysis processor, wherein said processor calculates the duration of said window as a function of said at least one frequency, thereby enabling the analysis of signals under non-steady state conditions; and

(d) providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

22. An apparatus for time dependent power spectrum analysis of a physiological signal, the apparatus comprising:

(a) a sensor for picking up a physiological signal;

(b) a frequency selector electrically connected to said sensor for selecting at least one frequency inherent to said signal;

(c) window generating apparatus electrically connected to said frequency selector for generating a window along said signal, the duration of said window being substantially inversely related to said at least one frequency;

(d) decimation apparatus electrically connected to said sensor and said window generating apparatus for providing data points within said window;

(e) spectral transform apparatus electrically connected to said decimation apparatus for determining the power spectrum of said signal within said window for said at least one frequency; and

(f) output apparatus electrically connected to said spectral transform apparatus for providing information associated with time dependent power spectrum of said signal.

23. The apparatus as in claim 22, wherein said sensor comprises one of the following:

an ECG recorder, a respiratory monitor, a finger plesthysmograph, a Doppler flow meter, a tachometer, a blood pressure transducer, a skin resistance galvanometer, an EEG monitor, an EMG monitor.

24. The apparatus as in claim 22, wherein said window having an aperture selected from one of the following:

a rectangular aperture, a Hamming aperture, a Hanning aperture, a Blackman aperture, a Gaussian window, a Lorentzian window, a sinc window, a power of a sine window, and a power of a cosine window.

25. The apparatus as in claim 22, further comprising frequency selection apparatus for determining the frequency resolution of the apparatus.

26. The apparatus as in claim 22, further comprising timing selection apparatus for determining the time resolution of the apparatus.

27. The apparatus as in claim 22, further comprising a physiological signal selector for selecting the type of physiological signal picked up said signal.

28. The apparatus as in claim 22, further comprising a type of perturbation selector for selecting the type of perturbation to be applied to a subject under investigation.

29. The apparatus as in claim 22, further comprising at least one frequency register for determining the range of frequency outputted on said output apparatus.

30. The apparatus as in claim 22, further comprising at least one timer for determining the onset and termination of the time dependent power spectrum of the physiological signal outputted on said output apparatus.

31. The apparatus as in claim 22, further comprising a detrending filter deployed between said sensor and said selective windowed time-frequency analysis processor.

32. The apparatus as in claim 22, further comprising a spectral transform selector for selecting a transform selected from one of the following:

the Fourier transform, the Haar transform, the Hartley transform, the sine transform, the cosine transform, and the Hadamard transform.

33. The apparatus as in claim 22, further comprising a window duration selector for selecting the duration of said window.

34. The apparatus as in claim 22, further comprising a window aperture selector for selecting the aperture of said window.

35. The apparatus as in claim 22, further comprising a number of points selector for selecting the number of data points within said window.

36. The apparatus as in claim 22, further comprising a decimation technique selector for selecting the decimation technique applied by said selective discrete spectral transform analysis processor.

37. A method of time dependent power spectrum analysis of a physiological signal, the method comprising the steps of:

(a) picking up a physiological signal;

(b) selecting at least one frequency inherent to the signal;

(c) generating a window along the signal by using a window generating apparatus, said window generating apparatus calculates the duration of the window to be substantially inversely related to the at least one frequency so as to enable the analysis of signals under non-steady state conditions;

(d) providing data points within the window;

(e) determining the power spectrum of the signal within the window for the at least one frequency; and

(f) providing information associated with time dependent power spectrum of the signal.

38. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency, said window has an aperture selected from one of the following;

a rectangular aperture, a Hamming aperture, a Hanning aperture, a Blackman aperture, a Gaussian window, a Lorentzian window, a sinc window, a power of a sine window and a power of a cosine window; and

(d) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

39. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency, said selective windowed time-frequency analysis processor comprises a Wavelet processor; and

(d) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

40. The apparatus of claim 39, further comprising a prototype function selector for selecting a prototype function applied by said Wavelet processor.

41. The apparatus of claim 39, further comprising a scale parameters selector for selecting scale parameters applied by said Wavelet processor.

42. The apparatus as in claim 39, further comprising a shift parameters selector for selecting shift parameters applied by said Wavelet processor.

43. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) a physiological signal selector electrically connected to said sensor for selecting the type of physiological signal picked up by said sensor;

(c) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(d) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency; and

(e) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

44. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency;

(d) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal; and

(e) a type of perturbation selector for selecting the type of perturbation to be applied to a subject under investigation.

45. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency;

(d) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal; and

(e) a detrending filter deployed between said sensor and said selective windowed time-frequency analysis processor.

46. An apparatus for time dependent power spectrum analysis of a physiological signal modulated by the autonomic nervous system, the apparatus comprising:

(a) a sensor for picking up a physiological signal modulated by the autonomic nervous system;

(b) frequency selection apparatus for selecting at least one frequency inherent to said signal;

(c) a selective windowed time-frequency analysis processor for determining the power spectrum of said physiological signal within a window along said signal for said at least one frequency, said selective windowed time-frequency analysis processor comprises a selective discrete spectral transform algorithm processor;

(d) a window duration selector for selecting the duration of said window;

(e) output apparatus for providing information associated with the functioning of the autonomic nervous system as provided by the power spectrum of the physiological signal.

47. The apparatus of claim 46, further comprising a spectral transform selector for selecting a transform selected from one of the following:

the Fourier transform, the Haar transform, the Hartley transform, the sine transform, the cosine transform, and the Hadamard transform.

48. The apparatus of claim 46, further comprising a window aperture selector for selecting the aperture of said window.

49. The apparatus of claim 46, further comprising a number of points selector for selecting the number of data points within said window.

50. The apparatus of claim 46, further comprising a decimation technique selector for selecting the decimation technique applied by said selective discrete spectral transform analysis processor.