Detection of abnormal and induction of normal heart rate variability

• US 5,891,044 A
• Filed: 01/10/1997
• Issued: 04/06/1999
• Est. Priority Date: 10/06/1992
• Status: Expired due to Fees

• Current Assignee: GW Scientific Incorporated
• Original Assignee: GW Scientific Incorporated
• Inventors: Golosarsky, Boris, Wood, Nicholas
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US08/781,330
• Time in Patent Office: 816 Days
• Field of Search: 128/696, 128/697, 128/702, 128/704, 128/705, 128/708, 128/903, 128/904, 607/14, 607/17, 607/27, 600/509, 600/510, 600/515, 600/517, 600/518, 600/521
• US Class Current: 600/509
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system
• CPC Class Codes: A61N 1/3625 External stimulators
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability
• CPC Class Codes: A61N 1/39 Heart defibrillators

Abstract

A microprocessor (300) with a date and time clock gathers time interval data (80, 86). The duration of the time intervals in an electrocardiogram, or pulses are recorded. Stress data accumulated for the user are down loaded to a PC (301). The battery power pack (303) supplies electricity to operate the components (80-318). The user'"'"'s stress status is displayed on a liquid crystal diode (302), and the voice microprocessor (318) broadcasts from a microspeaker CPR instructions. If the battery (303) has less than a 20% charge, a buzzer (304) notifies the user.

Claims

1. A method of detecting abnormal heart rate variability comprising:

A) recording a first subject'"'"'s time interval between heart beats for a plurality of heart beats in a first Time Segment;

B) identifying a characteristic of a histogram of said first subject'"'"'s recorded time interval between heart beats, said characteristic including at least one of a Mode of said histogram, an Amplitude of said Mode (AMo), which is expressed as a percentage, and a difference between substantially a largest and substantially a smallest time interval between heart beats in said first Time Segment (DX);

C) recording a second subject'"'"'s time interval between heart beats for a plurality of heart beats in a second Time Segment;

D) identifying a characteristic of a histogram of said second subject'"'"'s recorded time interval between heart beats, said characteristic including at least one of a Mode of said histogram, an Amplitude of said Mode (AMo), which is expressed as a percentage, and a difference between substantially a largest and substantially a smallest instantaneous heart rate or RR interval in said second Time Segment (DX); and

E) determining if said characteristic of said histogram of said second subject deviates from predetermined limits derived from said histogram of said first subject.

2. The method defined in claim 1, wherein said first and said second Time Segments include substantially no less than 50 to substantially no more than 300 heart beats and said intervals between heart beats are measured as a time between RR peaks.

3. A method of detecting abnormal heart rate variability, comprising:

A) recording a subject'"'"'s time interval between heart beats for a plurality of heart beats in a baseline Time Segment in which said subject'"'"'s heart rate variability is normal B) recording said subject'"'"'s time interval between heart beats for a plurality of heart beats in a current Time Segment; and

C) identifying at least one characteristic of a baseline histogram, which is a histogram of said baseline Time Segment, and at least one characteristic of a current histogram, which is a histogram of said current Time Segment, if said characteristic of said current histogram differs by more than a predetermined percentage from said baseline histogram for a predetermined period of time, then said subject is deemed to be experiencing ectopic stress.

4. The method defined in claim 3, wherein said characteristic of said baseline and said current histograms includes at least one of a Mode, an Amplitude of a Mode (AMo), an Amplitude of a Median (AM), an Amplitude of a Mean, a difference between substantially a largest and substantially a smallest interval between heart beats in a Time Segment (DX), a ratio between AMo and DX, a flatness parameter, a Full Width at Half Maximum, and a standard deviation of said histogram.

5. The method defined in claim 3, wherein said characteristic of said baseline and said current histograms includes a number for a User'"'"'s Value (UV), which is defined as follows:

##EQU3## where DX is a flatness parameter and AMo is an Amplitude of a Mode of the respective histogram, further comprising a step of generating a mixed sympathetic/parasympathetic alarm long term responsive to said UV for said current histogram differing from said UV for said baseline histogram by a predetermined amount for a first predetermined period of time, with no periods lasting a second predetermined period of time occurring during said first predetermined period of time in which said UV does not so differ.

6. The method defined in claim 3, wherein said characteristic of said baseline and said current histograms includes a number for a User'"'"'s Value (UV), which is defined as follows:

##EQU4## where DX is a flatness parameter and AMo is an Amplitude of a Mode of the respective histograms, further comprising a step of generating a mixed sympathetic/parasympathetic alarm long term responsive to said UV for said current histogram differing from said UV for said baseline histogram by a predetermined amount for a first predetermined time period during a second predetermined time period that is longer than said first predetermined period of time.

7. The method defined in claim 3, further comprising the step of providing an indication responsive to said characteristic of said current histogram exceeding a predetermined limit.

8. The method defined in claim 7, further comprising the step of generating a sympathetic alarm if said characteristic of said current histogram differs from an associated characteristic of said baseline histogram by a predetermined amount in any of a first number of current Time Segments within any of a second number of contiguous Time Segments.

9. The method defined in claim 8, wherein said predetermined amount is at most 0.125 times said associated characteristic of said baseline histogram.

10. The method defined in claim 8, wherein said predetermined amount is approximately 0.425 times said associated characteristic for said baseline histogram.

11. The method defined in claim 7, wherein said characteristic of said current histogram is selected from the group consisting of UV, AMo, DX, and DX divided by one of M and AMo.

12. The method defined in claim 3, further comprising the step of generating a parasympathetic alarm signal if a flatness parameter (DX) of said current histogram is not less than approximately 0.05 in any of a first number of Time Segments within any of a second number of contiguous Time Segments.

13. The method defined in claim 3, further comprising the step of generating a parasympathetic alarm signal if said subject'"'"'s AMo in said current histograms is not greater than approximately ten in any of a first number of Time Segments within any of a second number of contiguous Time Segments.

14. The method defined in claim 3, further comprising the step of generating a sympathetic caution-long term alarm signal if a difference between substantially a largest and substantially a smallest interval between heart beats (DX) in said current histogram is not greater than approximately 0.06 for a first period of time that is not less than approximately one hour.

15. The method defined in claim 3, further comprising the step of generating a caution-short term alarm signal if said subject'"'"'s AMo and DX for a plurality of current histograms vary directly with each other for approximately one hour.

16. A method of indicating cardiac distress comprising:

recording a user'"'"'s baseline value for a characteristic selected from the group consisting of AMo and DX;

recording a user'"'"'s current value for a characteristic selected from the group consisting of AMo and DX; and

generating an alarm responsive to said user'"'"'s current value of said characteristic differing from said baseline value of said characteristic by a predetermined amount for a first period of time with no second periods of time occurring during said first period of time where said characteristic does not so differ.

17. The method defined in claim 16, wherein an AMo sympathetic alarm is generated responsive to said current value of AMo being greater than said baseline value of AMo.

18. The method defined in claim 16, wherein an AMo parasympathetic alarm is generated responsive to said current value of AMo being less than said baseline value of AMo.

19. A method of indicating cardiac distress comprising:

recording a user'"'"'s baseline value of;

recording said user'"'"'s current value of DX;

generating a first alarm signal responsive to said user'"'"'s current value of DX differing from said baseline value by a predetermined amount for a first period of time with no second periods of time occurring during said first period of time where said characteristic does not so differ, and

recording said user'"'"'s baseline value of AMo;

recording said user'"'"'s current value of AMo; and

generating a second alarm signal responsive to said user'"'"'s current value of AMo differing from said baseline value by a predetermined amount for a third period of time with no fourth periods of time occurring during said third period of time where said characteristic does not so differ.

20. The method defined in claim 19, further comprising the step of generating a mixed sympathetic/parasympathetic alarm long term responsive to said first and said second alarm signals being provided in an alternating manner for a fifth period of time with no sixth periods of time occurring during said fifth period of time where no first or second alarm signal occurs.

21. The method defined in claim 20, further comprising the step of generating a mixed sympathetic/parasympathetic alarm long term responsive to said first and said second alarm signals being provided in an alternating manner for a seventh period of time within an eighth time period that is longer than said seventh time period.

22. An apparatus comprising:

A) means for recording a subject'"'"'s time interval between heart beats for a plurality of heart beats;

B) means for identifying at least one characteristic of a histogram of said recorded time intervals between heart beats and

C) means for determining if said at least one characteristic of said histogram exceeds a predetermined limit.

23. The apparatus as defined in claim 22, further comprising a module adapted to be carried by said subject, said module containing said means for recording, said means for identifying at least one characteristic, and said means for determining if said at least one characteristic of said histogram exceeds a predetermined limit.

24. The apparatus as defined in claim 23, wherein said module further comprises:

a) a motion sensor;

b) means responsive to said motion sensor to distinguish between states of coma, sleep, wakefulness, and physical activity;

c) a galvanic skin sensor; and

d) means responsive to said galvanic skin sensor to determine whether said module is contacting said subject'"'"'s skin.

25. The apparatus as defined in claim 22, wherein said characteristic of said histogram includes at least one of UV, AMo, DX, and DX divided by one of M and AMo.

26. The apparatus as defined in claim 22, wherein said predetermined limit is determined based on at least one of a characteristic of a baseline histogram, which is a histogram of said subject'"'"'s time intervals between heart beats for a plurality of heart beats having normal variability, and a characteristic of a model histogram, which is a histogram of time intervals between heart beats for a plurality of heart beats in an individual having at least one characteristic approximating an associated characteristic of said subject.

27. The apparatus as defined in claim 22, further comprising at least one of the following:

means for transmitting data output by at least one of said means for recording, said means for identifying at least one characteristic of said histogram, and said means for determining if said at least one characteristic of said histogram exceeds said predetermined limit; and

means for displaying in a human perceivable format data output by at least one of said means for recording, said means for identifying at least one characteristic of said histogram, and said means for determining if said at least one characteristic of said histogram exceeds said predetermined limit.

28. The apparatus as defined in claim 22, further comprising means for transmitting first data output by at least one of said means for recording, said means for identifying at least one characteristic of said histogram, and said means for determining if said at least one characteristic of said histogram exceeds said predetermined limit;

a base station adapted to receive said first data, wherein said base station includes means for outputting, in a human perceivable format, at least one of said first data and information based on said first data.

29. A method of detecting abnormal heart rate variability, comprising:

recording a subject'"'"'s time interval between heart beats for a plurality of heart beats;

identifying at least one characteristic of a histogram of said recorded time intervals between heart beats; and

determining if at least one characteristic of said histogram exceeds a predetermined limit.

30. The method defined in claim 29, further comprising:

distinguishing, based on motion of said subject, between states of coma, sleep, wakefulness, and physical activity; and

determining whether said step of recording a subject'"'"'s time interval between heart beats is taking place properly based on a determination of whether sensors for detecting heart beats are contacting said subjects skin.

31. The method defined in claim 30, wherein said step of identifying a characteristic of said histogram includes identifying at least one of UV, AMo, DX, and DX divided by one of M and AMo.

32. The apparatus as defined in claim 30, wherein said step of determining if at least one characteristic of said histogram exceeds a predetermined limit includes setting said predetermined limit as at least one of a characteristic of a baseline histogram, which is a histogram of said subject'"'"'s time intervals between heart beats for a plurality of heart beats having normal variability, and a characteristic of a model histogram, which is a histogram of time intervals between heart beats for a plurality of heart beats in an individual having at least one characteristic approximating an associated characteristic of said subject.

33. The apparatus as defined in claim 30, further comprising at least one of the following steps:

transmitting data produced in at least one of said steps of recording, identifying at least one characteristic of said histogram, and determining if said at least one characteristic of said histogram exceeds said predetermined limit; and

displaying in a human perceivable format data produced by at least one of said steps of recording, identifying at least one characteristic of said histogram, and determining if said at least one characteristic of said histogram exceeds said predetermined limit.

34. The apparatus as defined in claim 33, further comprising transmitting to a base station first data produced in least one of said steps of recording, identifying at least one characteristic of said histogram, and determining if said at least one characteristic of said histogram exceeds said predetermined limit;

and

outputting in a human perceivable format at least one of said first data and information produced based on said first data.