Iterative sleep evaluation

• US 5,520,176 A
• Filed: 06/23/1993
• Issued: 05/28/1996
• Est. Priority Date: 06/23/1993
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: Aequitron Medical, Inc. (Medtronic Plc)
• Inventors: Cohen, Daniel E.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/081,586
• Time in Patent Office: 1,070 Days
• Field of Search: 364/413.02-413.06, 128/670, 128/671, 128/731, 128/732, 128/733, 128/716, 128/630
• US Class Current: 600/300
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/372 Analysis of electroencephalograms
• CPC Class Codes: A61B 5/4806 Sleep evaluation A61B5/4821 takes precedence; devices for inducing sleep A61M21/02
• 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

Abstract

A sleep analysis system for analyzing a sleep episode of a subject based on measured values of a plurality of parameters characterizing that subject. Portions of the measured parameter signals are classified as significant events, and the significant events are segregated based on parameter signal criteria and time correlation as a basis for the analysis.

Claims

1. A method for analyzing a sleep episode of a subject based on measured values of a plurality of parameters characterizing physiological activity of that subject during such an episode, said method comprising:

acquiring from said subject a plurality of parameter signals each representing values occurring during at least parts of said episode of a corresponding one of said plurality of parameters;

classifying portions of each of said plurality of parameter signals as significant events for that said parameter corresponding thereto based on selected signal criteria including classifying such significant events of a first parameter signal, corresponding to a first parameter, into a plurality of ranks having among them an initial rank of those first parameter significant events corresponding to portions of said first parameter signal having values beyond an initial first parameter threshold; and

segregating from said first parameter significant events those (i) which (a) are said initial rank first parameter significant events, and those which (b) are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of a first selection of significant events of another of said plurality of parameters to form a first tier of said first parameter significant events in a plurality of tiers of said first parameter significant events, and those (ii) which are in said plurality of ranks of said first parameter significant events without being in said first tier of first parameter significant events to form at least a second tier in said plurality of tiers of said first parameter significant events.

2. The method of claim 1 further comprising counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and providing a visual display in which representations of said total counts of said first and second tiers of said first parameter significant events are provided.

3. The method of claim 2 wherein said first tier of said first parameter significant events includes those said first parameter significant parameter events which are in one of said plurality of ranks other than said initial rank but occur within a selected time of one of a first selection of significant parameter events of a second parameter;

and further comprising counting said selected second parameter significant parameter events to provide a total count thereof, and providing a representation of said total count of said selected second parameter significant parameter events in said visual display.

4. The method of claim 3 further comprising counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and displaying representations of said total counts of said first and second tiers of said first parameter significant events on said visual display.

5. The method of claim 1 wherein said first tier of said first parameter significant events includes those said first parameter significant events which are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of a first selection of significant events of a second parameter, and wherein said segregating from said first parameter significant events further comprises segregating those which are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of selected said significant events of a third parameter.

6. The method of claim 5 further comprising counting said selected second and third parameter significant events to provide total counts thereof, and providing a representation of said total counts of said selected second and third parameter significant events in a visual display.

7. The method of claim 6 further comprising indicating on said visual display those fractions of said second and third count totals which occur within said selected times of any of said first parameter significant events.

8. The method of claim 7 further comprising counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and displaying representations of said total counts of said first and second tiers of said first parameter significant events on said visual display.

9. The method of claim 6 further comprising counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and displaying representations of said total counts of said first and second tiers of said first parameter significant events on said visual display.

10. The method of claim 5 wherein said segregating from said first parameter significant events includes segregating, from among those said first parameter significant events that occur within selected times of any of said selected second and third parameter significant events, just those occurring within a second parameter selected time of a said second parameter significant event and within a third parameter selected time of a said third parameter significant event.

11. The method of claim 1 wherein said classifying of said significant events of a first parameter signal corresponding to a first parameter into a plurality of ranks further includes having among said plurality of ranks a baseline rank of those first parameter significant events corresponding to portions of said first parameter signal having values beyond a baseline first parameter threshold but within said initial first parameter threshold.

12. The method of claim 11 wherein said classifying of said significant events of a first parameter signal corresponding to a first parameter into a plurality of ranks further includes having those of said plurality of ranks of first parameter significant events other than said initial and baseline ranks contain first parameter significant events corresponding to portions of said first parameter signal having values beyond a corresponding one of an ordered set of interpolated first parameter thresholds ordered by magnitude and within that next in order one of said interpolative first parameter thresholds, said set of interpolative first parameter thresholds all being beyond said baseline first parameter threshold in magnitude and within said initial first parameter threshold in magnitude.

13. The method of claim 1 wherein said segregating from said first parameter significant events includes forming said first tier of said first parameter significant events with all of said first parameter significant events which are in one of said plurality of ranks other than said initial rank.

14. The method of claim 1 further comprising changing said first tier of said first parameter significant events to form a revised first tier of said first parameter significant events by selecting one of a further set of steps comprising an addition thereto of other selected said first parameter significant events and an exclusion therefrom of selected said first parameter significant events previously included therein.

15. The method of claim 1 wherein said first tier of said first parameter significant events includes those said first parameter significant events which are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of a first selection of significant parameter events of a second parameter;

and further comprising counting said second parameter significant events to provide a total count thereof and providing a visual display in which a representation of said total count of said second parameter significant events is provided so as to indicate that fraction thereof which occurs within said selected time of any of said first parameter significant events.

16. The method of claim 15 further comprising counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and displaying representations of said total counts of said first and second tiers of said first parameter significant events on said visual display.

17. The method of claim 1 wherein said acquiring of a plurality of parameter signals is accomplished through sensing said parameters with corresponding sensors that are positioned on said subject so as to provide a corresponding sensor signal.

18. The method of claim 17 wherein said sensor signals are analog signals, and further comprises converting said analog signals to digital signals.

19. A sleep analysis system for analyzing a sleep episode of a subject based on measured values of a plurality of parameters characterizing that subject during such an episode, said system comprising:

a signal acquiring means for acquiring a plurality of parameter signals each representing values of a corresponding one of said plurality of parameters occurring during at least parts of said episode;

an analog-to-digital converter means coupled to said signal acquiring means for providing corresponding sequences of digitized samples amplitude values of said parameter signals;

a display and input means for providing displays of representations of said parameter signals provided at inputs thereof, and capable of providing selected values at outputs thereof;

a signal processing means coupled to said analog-to-digital converter means and to said inputs and outputs of said display and input means, and capable of classifying portions of each of said plurality of parameter signals as significant events for that said parameter corresponding thereto based on selected signal criteria including classifying such significant events of a first parameter signal, corresponding to a first parameter, into a plurality of ranks having among them an initial rank of those first parameter significant events corresponding to portions of said first parameter signal having values beyond an initial first parameter threshold, and of segregating from said first parameter significant events those (i) which (a) are said initial rank first parameter significant events, and those which (b) are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of a first selection of significant events of at least one other of said plurality of parameters to form a first tier of said first parameter significant events in a plurality of tiers of said first parameter significant events, and those (ii) which are in said plurality of ranks of said first parameter significant events without being in said first tier of first parameter significant events to form at least a second tier in said plurality of tiers of said first parameter significant events.

20. The apparatus of claim 19 wherein said display and input means further comprises a visual display, and wherein said signal processing means is capable of counting said first parameter significant events in said plurality of tiers to provide total counts thereof, and of displaying representations of said total counts of said first and second tiers of said first parameter significant events on said visual display.

21. The apparatus of claim 20 wherein said first tier of said first parameter significant events includes those said first parameter significant events which are in one of said plurality ranks other than said initial rank but occur within a selected time of any of a first selection of significant parameter events of a second parameter;

and wherein said signal processing means is further capable of counting said second parameter significant events to provide a total count thereof and providing a representation of said total count of said second parameter events in said visual display.

22. The apparatus of claim 19 wherein said first tier of first parameter significant events includes those said first parameter significant events which are in one of said plurality of ranks other than said initial rank but occur within a selected time of any of a first selection of significant events of a second parameter, and wherein said signal processing means is further capable of segregating from said first parameter significant events those which are in one of said plurality of ranks other than said initial rank but that occur within a selected time of any of selected said significant events of a third parameter.

23. The apparatus of claim 22 further wherein said signal processing means is further capable of counting said selected second and third parameter significant events to provide total counts thereof and providing a representation of said total counts of said selected second and third parameter significant events in said visual display.

24. The apparatus of claim 23 wherein there is indicated on said visual display those fractions of said second and third count totals which occur within said selected times of one of said first parameter significant events.

25. The apparatus of claim 22 wherein said signal processing means is further capable of segregating, from among those said first parameter significant events that occur within selected times of any of said selected second and third parameter significant events, just those occurring within a second parameter selected time of a said second parameter significant event and within a third parameter selected time of a said third parameter significant event.

26. The apparatus of claim 19 wherein said plurality of ranks includes a baseline rank of those first parameter significant events corresponding to portions of said first parameter signal having values beyond a baseline first parameter threshold but within said initial first parameter threshold.

27. The apparatus of claim 26 wherein those of said plurality of ranks of first parameter significant events other than said initial and baseline ranks contain first parameter significant events corresponding to portions of said first parameter signal having values beyond a corresponding one of an ordered set of interpolated first parameter thresholds ordered by magnitude and within that next in order one of said interpolative first parameter thresholds, said set of interpolative first parameter thresholds all being beyond said baseline first parameter threshold in magnitude and within said initial first parameter threshold in magnitude.

28. The apparatus of claim 19 wherein said signal processing means is further capable of forming said first tier of said first parameter significant events with all of said first parameter significant events which are in one of said plurality of ranks other than said initial rank.

29. The apparatus of claim 19 wherein said signal processing means is further capable of changing said first tier of said first parameter significant events to form a revised first tier of said first parameter significant events by selecting one of a further set of steps comprising in addition thereto of other selected said first parameter significant events and an exclusion therefrom of selected said first parameter significant events previously included therein.

30. The apparatus of claim 19 wherein said first tier of said first parameter significant events includes those said first parameter significant events which are in one of said plurality ranks other than said initial rank but occur within a selected time of any of a first selection of significant parameter events of a second parameter;

and wherein said signal processing means is further capable of counting said second parameter significant events to provide a total count thereof and providing a representation of said total count of said second parameter events in said visual display so as to indicate that fraction thereof which occurs within said selected time of any of said first parameter significant events.