Interactive determination of sleep stages

• US 4,776,345 A
• Filed: 09/04/1987
• Issued: 10/11/1988
• Est. Priority Date: 09/04/1987
• Status: Expired due to Term

• Current Assignee: Aequitron Medical, Inc. (Medtronic Plc)
• Original Assignee: CNS Incorporated (GSK plc)
• Inventors: Fitzgerald, Rihab, Cohen, Daniel E., Anderson, Milton W.
• Primary Examiner(s): Jaworski, Francis J.
• Application Number:
  US07/093,576
• Time in Patent Office: 403 Days
• Field of Search: 128/731-733, 364/415, 364/417
• US Class Current: 600/544
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles

Abstract

Such representations may include the average frequency value of electroencephalographic signals, the logarithm of the power of electromyographic signals, and eye movement indications from electrooculographic signals. Criteria for dividing the records of such representations in the system into stages of sleep can be set by a system operator reviewing these records based on accepted stage definition rules. In addition, transient events such as sleep spindles, etc., in these records can be selected therefrom by criteria set by the system operator also based on accepted rules therefor.

Claims

1. A method of determining whether waking or any of a plurality of defined types of sleep including first, second, third, fourth and fifth types of sleep occur in data gathered from a subject, said determinations being made based on such data gathered and various criteria, said method comprising:

obtaining electroencephalographic signal data and electromyographic signal data from said subject;

providing a representation of frequency content of said electroencephalographic signal data and presenting said electroencephalographic frequency content representation on a display means;

providing a representation of signal strength of said electromyographic signal data and presenting said electromyographic signal strength representation on said display means;

providing selected frequency and signal strength values at least one of which is greater than values of a portion and less than values of another portion of a corresponding one of said electroencephalographic frequency content representation and said electromyographic signal strength representation; and

determining, based on said electroencephalographic signal data and said electromyographic signal data and on said selected frequency and signal strength values, whether waking or which of any of said types of sleep have been experienced by said subject during said obtaining of said electroencephalographic signal data and electromyographic signal data.

2. The method of claim 1 further comprising obtaining electrooculographic signal data from said subject and providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal data.

3. The method of claim 2 wherein said obtaining of said electroencephalographic signal data, said electromyographic signal data, and said electrooculographic signal data comprises acquiring a first sequence of consecutive samples of amplitude values of said electroencephalographic signal data taken at a rate sufficient to represent that signal, acquiring a second sequence of consecutive samples of amplitude values of said electromyographic signal data taken at a rate sufficient to represent that signal, and acquiring a third sequence consecutive samples of amplitude values of said electrooculographic signal data taken at a rate sufficient to represent that signal.

4. The method of claim 3 wherein said first sequence of consecutive samples also comprises a plurality of successive, selected first sequence subsequences, said second sequence also comprises a plurality of successive, selected second sequence subsequences, and said third sequence of consecutive samples also comprises a plurality of successive, selected third sequence subsequences, and wherein said method further comprises forming a first succession of frequency domain power spectra with there being one of said frequency domain power spectra in said first succession thereof formed for each of selected ones of said first sequence subsequences, forming a second succession of frequency domain power spectra with there being one of said frequency domain power spectra in said second succession thereof formed for each of selected ones of said second sequence subsequences, forming a third succession of frequency domain power spectra with there being one of said frequency domain power spectra formed for each of selected ones of said third sequence subsequences.

5. The method of claim 4 wherein said method further comprises forming a succession of weighted averages with there being one of said weighted averages in said succession thereof found for those frequencies present in each of said first succession of frequency domain power spectra through finding the products of frequencies represented in a frequency domain power spectrum and spectral power at those frequencies divided by a totality of spectral powers of those frequencies represented in that said spectrum, and determining a succession of total powers with there being one of said total powers determined for each said frequency domain power spectrum in said second succession thereof, determining for each of selected said first sequence subsequences whether any sleep spindles or K-complexes have occurred therein, and determining for each of selected said third sequence subsequences whether any rapid eye movements have occurred therein.

6. The method of claim 5 further comprising determining selectively from each simultaneously acquired said first sequence subsequence and said second sequence subsequence jointly, and from each simultaneously acquired said second sequence subsequence and said third sequence subsequence jointly, whether an indication of a movement arousal is present.

7. The method of claim 5 further comprising forming a succession of epoch average frequency values with each said epoch average frequency value in said succession thereof comprising an arithmetic average of a selected plurality of said weighted averages from said succession thereof, and forming a succession of epoch average total powers with each said epoch average total power in said succession thereof comprising an arithmetic average of a selected plurality of said total powers from said succession thereof.

8. The method of claim 7 further comprising presenting said eye movement occurrence representation on said display means.

9. The method of claim 2 wherein said determining is preceded at least in part by finding occurrences of sleep spindles and K-complexes in said electroencephalographic signal data, and finding occurrences of rapid eye movements in said electrooculographic signal data, and wherein said determining is further based on said occurrences.

10. The method of claim 9 wherein said finding of occurrences further comprises finding occurrences of movement arousals selectively indicated jointly in said electromyographic signal data and said electroencephalographic signal data, and jointly in said electromyographic signal data and said selectrooculographic signal data, and wherein said determining is further based on such occurrences.

11. The method of claim 10 wherein said determining further comprises determining any incidences of at least one type of said types of sleep based both on giving effect to said occurrences and on giving no effect to said occurrences other than occurrences of rapid eye movements, followed by comparing incidences of that one type of sleep as determined on each basis to one another.

12. The method of claim 9 wherein said determining further comprises determining any incidences of at least one type of said types of sleep based both on giving effect to said occurrences and on giving no effect to said occurrences other than occurrences of rapid eye movements, followed by comparing incidences of that one type of sleep as determined on each basis to one another.

13. The method of claim 1 wherein said obtaining of said electroencephalographic signal data and said electromyographic signal data comprises acquiring a first sequence of consecutive samples of amplitude values of said electroencephalographic signal data taken at a rate sufficient to represent that signal, and acquiring a second sequence of consecutive samples of amplitude values of said electromyographic signal data taken at a rate sufficient to represent that signal.

14. The method of claim 13 wherein said first sequence of consecutive samples also comprises a plurality of successive, selected first sequence subsequences, and said second sequence also comprises a plurality of successive, selected second sequence subsequences, and wherein said method further comprises forming a first succession of frequency domain power spectra with there being one of said frequency domain power spectra in said first succession thereof formed for each of selected ones of said first sequence subsequences, and forming a second succession of frequency domain power spectra with there being one of said frequency domain power spectra in said second succession thereof formed for each of selected ones of said second sequence subsequences.

15. The method of claim 14 wherein said method further comprises forming a succession of weighted averages with there being one of said weighted averages in said succession thereof found for those frequencies present in each of said first succession of frequency domain power spectra through finding the products of frequencies represented in a frequency domain power spectrum and spectral power at those frequencies divided by a totality of spectral powers of those frequencies represented in that said spectrum, and determining a succession of total powers with there being one of said total powers determined for each said frequency domain power spectrum in said second succession thereof.

16. The method of claim 15 further comprising determining from each simultaneously acquired said first sequence subsequence and said second sequence subsequence jointly whether an indication of a movement arousal is present.

17. The method of claim 15 further comprising forming a succession of epoch average frequency values with each said epoch average frequency value in said succession thereof comprising an arithmetic average of a selected plurality of said weighted averages from said succession thereof, and forming a succession of epoch average total powers with each said epoch average total power in said succession thereof comprising an arithmetic average of a selected plurality of said total powers from said succession thereof.

18. The method of claim 1 wherein said providing of said electroencephalographic frequency content representation comprises obtaining a frequency power spectrum of said electroencephalographic signal data for a period of time and forming a weighted average of frequencies present in that spectrum by finding a totality of products of frequencies represented in said spectrum and spectral powers at those frequencies divided by a totality of spectral powers of those frequencies represented in said spectrum.

19. The method of claim 18 wherein said providing of said electromyographic signal strength representation comprises obtaining a logarithm of that signal strength present occurring in said electromyographic signal data.

20. The method of claim 19 further comprising obtaining electrooculographic signal data from said subject, providing a representation of numbers of occurrences of selected eye movements indicated in said electrooculographic signal data, and presenting said eye movement representation of numbers of occurrences on said display means.

21. The method of claim 1 wherein said providing of said electromyographic signal strength representation comprises obtaining a logarithm of that signal strength present in said electromyographic signal data.

22. The method of claim 21 wherein said signal strength is found by determining that power contained in at least a portion of said electromyographic signal data.

23. The method of claim 1 wherein said providing of said selected frequency and signal strength values comprises:

entering into a memory means a selected first frequency value chosen such that taking a portion of said electroencephalographic frequency content representation having frequency values related in a selected manner to said first frequency value, if any, is consistent with said fourth type of sleep;

entering into said memory means a selected second frequency value chosen such that taking a portion of said electroencephalographic frequency content representation having frequency values related in a selected manner to said second frequency value and to said first frequency value, if any, is consistent with said third type of sleep;

entering into said memory means a selected third frequency value chosen such that taking a portion of said electroencephalographic frequency representation having frequency values related in a selected manner to said third frequency value is consistent with said waking; and

entering into said memory means a selected first signal strength value chosen such that taking a portion of said electromyographic signal strength representation having signal strength values related in a selected manner to said first signal strength value, if any, is consistent with said fifth type of sleep.

24. The method of claim 23 wherein said entering into a memory means of a selected first frequency value comprises estimating along said electroencephalographic frequency content representation an initial first frequency value, reviewing representations of portions of said electroencephalographic signal data from which those portions of said electroencephalographic frequency content representation having values near said initial first frequency value were obtained, determining wherein said electroencephalographic signal data transition region occurs between a portion of said electroencephalographic signal data consistent with said fourth type of sleep and another portion thereof consistent with said third type of sleep, and entering in said memory means as said selected first frequency value that frequency value at which said transition region occurs.

25. The method of claim 24 wherein said reviewing of representations comprises displaying said representations of portions of said electroencephalographic signal data on said display means.

26. The method of claim 24 further comprising obtaining electrooculographic signal data from said subject, providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal data, and presenting said eye movement occurrence representation on said display means, and wherein said reviewing of representations of portions of said electroencephalographic data is accompanied by reviewing representations of simultaneously obtained portions of said electromyographic signal data and said electrooculographic signal data.

27. The method of claim 23 wherein said entering into a memory means of a selected second frequency value comprises estimating along said electroencephalographic frequency content representation an initial second frequency value, reviewing representations of portions of said electroencephalographic signal data from which those portions of said electroencephalographic frequency content representation having values near said initial second frequency value were obtained, determining where in said electroencephalographic signal data a transition region occurs between a portion of said electroencephalographic signal data consistent with said third type of sleep and another portion thereof consistent with other types of sleep excluding said fourth type of sleep, and entering in said memory means as said selected second frequency value that frequency value at which said transition region occurs.

28. The method of claim 27 wherein said reviewing of representations comprises displaying said representations of portions of said electroencephalographic signal data on said display means.

29. The method of claim 27 further comprising obtaining electrooculographic signal data from said subject, providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal data, and presenting said eye movement occurrence representation on said display means, and wherein said reviewing of representations of portions of said electroencephalographic data is accompanied by reviewing representations of simultaneously obtained portions of said electromyographic signal data and said electrooculographic signal data.

30. The method of claim 23 wherein said entering into a memory means of a selected third frequency value comprises estimating along said electroencephalographic frequency content representation an initial third frequency value, reviewing representations of portions of said electroencephalographic signal data from which those portions of said electroencephalographic frequency content representation having values near said initial third frequency value were obtained, determining where in said electroencephalographic signal data a transition region occurs between a portion of said electroencephalographic signal data consistent with each said type of sleep and another portion thereof consistent with waking, and entering in said memory means as said third frequency value that frequency value at which said transition region occurs.

31. The method of claim 30 wherein said reviewing of representations comprises displaying said representations of portions of said electroencephalographic signal data on said display means.

32. The method of claim 30 further comprising obtaining electrooculographic signal data from said subject, providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal data, and presenting said eye movement occurrence representation on said display means, and wherein said reviewing of representations of portions of said electroencephalographic data is accompanied by reviewing representations of simultaneously obtained portions of said electromyographic signal data and said electrooculographic signal data.

33. The method of claim 23 wherein said entering into a memory means of a selected first signal strength value comprises estimating along said electromyographic signal strength content representation an initial first signal strength value, reviewing representations of portions of said electromyographic signal data from which those portions of said electromyographic signal strength representation having values near said initial first signal strength value were obtained, determining where in said electromyographic signal data a transition region occurs between a portion of said electromyographic signal data consistent with said fifth type of sleep and another portion thereof consistent with other types of sleep, and entering in said memory means as said selected first signal strength value that signal strength value at which said transition region occurs.

34. The method of claim 33 wherein said reviewing of representations comprises displaying said representations of portions of said electromyographic signal data on said display means.

35. The method of claim 33 further comprising obtaining electrooculographic signal data from said subject, providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal data, and presenting said eye movement occurrence representation on said display means, and wherein said reviewing of representations of portions of said electromyographic data is accompanied by reviewing representations of simultaneously obtained portions of said electroencephalographic signal data and said electrooculographic signal data.

36. The method of claim 1 wherein said determining is preceded at least in part by finding occurrences of sleep spindles and K-complexes in said electroencephalographic signal data, and wherein said determining is further based on such occurrences.

37. The method of claim 36 wherein said finding of occurrences further comprises finding occurrences of movement arousals indicated jointly in said electromyographic signal data and said electroencephalographic signal data, and wherein said determining is further based on such occurrences.

38. The method of claim 37 wherein said determining further comprises determining any incidences of at least one of said types of sleep based both on giving effect to said occurrences and on giving no effect to said occurrences in such determination, followed by comparing incidences of that one said type of sleep as determined on each basis to one another.

39. The method of claim 36 wherein said determining further comprises determining any incidences of at least one of said types of sleep based both on giving effect to said occurrences and on giving no effect to said occurrences in such determination, followed by comparing incidences of that one said type of sleep as determined on each basis to one another.

40. A sleep stage monitoring system for providing determination of whether waking or any of a plurality of defined types of sleep, including first, second, third, fourth and fifth types of sleep, occur in data gathered from a subject, said system comprising:

a signal acquiring means for acquiring an electroencephalographic signal, an electromyographic signal and an electrooculographic signal;

an analog-to-digital converter means connected to said signal acquiring means for providing a first sequence of consecutive digitized samples of amplitude values of said electroencephalographic signal, a second sequence of consecutive digitized samples of amplitude values of said electromyographic signal, and a third sequence of consecutive digitized samples of amplitude values of said electrooculographic signal;

a display and input means capable of providing displays of representations of said electroencephalographic signal, said electromyographic signal and said electrooculographic signal provided at inputs thereof, and capable of providing selected values at outputs thereof; and

a signal processing means connected to said analog-to-digital converter means and to said inputs and outputs of said display and input means, and capable of providing a representation of frequency content of said electroencephalographic signal from said first sequence, of providing a representation of signal strength of said electromyographic signal from said second sequence, and of providing a representation of occurrences of selected eye movements indicated in said electrooculographic signal from said third sequence, and further capable of accepting selected frequency and signal strength values at outputs of said display and input means to provide a determination, based on said first sequence, said second sequence and said third sequence and on said frequency and signal strength values, whether waking or which of any of said types of sleep have been experienced by said subject as indicated in said electroencephalographic, said electromyographic and said electrooculographic signals.

41. The apparatus of claim 40 wherein said display and input means can display representations of said first sequence, said second sequence and said third sequence received at inputs thereof from said signal processing means.