Method for detecting physiological condition of sleeping patient based on analysis of pulse waves

• US 6,856,829 B2
• Filed: 08/24/2001
• Issued: 02/15/2005
• Est. Priority Date: 09/07/2000
• Status: Active Grant

• Current Assignee: DENSO Corporation, Junichiro Hayano, Toshiaki Shiomi
• Original Assignee: DENSO Corporation, Junichiro Hayano, Toshiaki Shiomi
• Inventors: Shiomi, Toshiaki, Hayano, Junichiro, Ohsaki, Rie, Nanba, Shinji, Kimura, Teiyuu
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US09/935,678
• Publication Number:
  US 20020029000A1
• Time in Patent Office: 1,271 Days
• Field of Search: 600/500, 600/501, 600/502, 600/503, 600/481, 600/483, 600/485, 600/490, 600/494, 600/508, 600/310, 600/476, 600/477, 600/479, 600/480, 600/484
• US Class Current: 600/479
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence

Abstract

A physiological condition detecting method detects pulse waves from the body of a patient, and creates the envelope of the pulse waves by connecting every peak of the pulse waves. It determines that the patient is in non-REM sleep, if the envelope fluctuates regularly. It determines that the patient is in REM sleep, if the envelope fluctuates irregularly. Further the method calculates and normalizes the amplitude and period of the envelope. It determines whether the patient has obstructive sleep apnea syndrome based on the normalized amplitude. It determines whether the patient has central sleep apnea syndrome based on the normalized period. It determines that the patient has mixed sleep apnea syndrome based on the normalized amplitude and the normalized period.

Claims

1. A method for detecting a physiological condition of a patient comprising the steps of:

emitting light into the body of the patient;

detecting pulse waves from the body of the patient from light reflected by the body of the patient;

creating an envelope of the pulse waves;

analyzing the envelope; and

determining whether the patient is in a specific physiological condition based on a result of the analysis.

2. A method for detecting a physiological condition of a patient as in claim 1,

wherein the step of analyzing includes the step of:

calculating for every regular time interval a statistical index which represents characteristics of the envelope over the time interval, and

wherein the step of determining includes using the statistical index.

3. A method for detecting a physiological condition of a patient comprising:

detecting pulse waves from the body of the patient;

calculating a pulse height of each of the pulse waves;

analyzing the pulse height; and

determining whether the patient is in a specific physiological condition based on a result of the analysis,

wherein the step of analyzing includes the step of;

calculating for every regular time interval a statistical index which represents characteristics of the pulse height over the time interval, and

wherein the step of determining includes using the statistical index.

4. A method for detecting a physiological condition of a patient comprising:

detecting pulse waves from the body of the patient;

calculating a pulse height of each of the pulse waves;

analyzing the pulse height; and

determining whether the patient is in a specific physiological condition based on a result of the analysis,

wherein the step of analyzing includes the steps of;

creating a baseline of the pulse waves by connecting middle points of the pulse height; and

calculating for every regular time interval a statistical index which represents characteristics of the baseline over the time interval, and

wherein the step of determining includes using the statistical index.

5. A method for detecting a sleep condition of a patient comprising the steps of:

emitting light into the body of the patient;

detecting pulse waves from the sleeping body of the patient from light reflected by the body of the patient;

creating an envelope of the pulse waves by connecting one of tops and bottoms of the pulse waves;

determining that the patient is in non-REM sleep if the envelope fluctuates regularly; and

determining that the patient is in REM sleep if the envelope fluctuates irregularly.

6. A method for detecting a sleep condition of a patient as in claim 5, further comprising the step of:

calculating for every regular time interval a statistical index which represents characteristics of the envelope over the time interval,

wherein the steps of determining include using the statistical index.

7. A method for detecting a sleep condition of a patient as in claim 6,

wherein the statistical index includes at least one of an average, a maximum value, a minimum value, a variance, a deviation of a level of the envelope.

8. A method for detecting a physiological condition of a patient as in claim 5,

wherein the pulse waves are detected from one of the wrist and forearm of the patient.

9. A method for detecting a sleep condition of a patient comprising the steps of:

detecting pulse waves from the sleeping body of the patient;

calculating a pulse height of each of the pulse waves;

determining that the patient is in non-REM sleep if the pulse height fluctuates regularly; and

determining that the patient is in REM sleep if the pulse height fluctuates irregularly.

10. A method for detecting a sleep condition of a patient as in claim 9, further comprising the step of:

calculating for every regular time interval a statistical index which represents characteristics of the pulse height over the time interval,

wherein the steps of determining include using the statistical index.

11. A method for detecting a sleep condition of a patient as in claim 10,

wherein the statistical index includes at least one of an average, a maximum value, a minimum value, a variance, a deviation of the pulse height.

12. A method for detecting a sleep condition of a patient as in claim 9,

wherein the pulse waves are detected from one of the wrist and forearm of the patient.

13. A method for detecting a sleep condition of a patient comprising the steps of:

detecting pulse waves from the sleeping body of the patient;

calculating a pulse height of each of the pulse waves;

creating a baseline of the pulse waves by connecting middle points of the pulse height;

determining that the patient is in non-REM sleep if the baseline fluctuates regularly; and

determining that the patient is in REM sleep if the baseline fluctuates irregularly.

14. A method for detecting a sleep condition of a patient as in claim 13, further comprising the step of:

calculating for every regular time interval a statistical index which represents characteristics of the baseline over the time interval,

wherein the steps of determining include using the statistical index.

15. A method for detecting a sleep condition of a patient as in claim 14,

wherein the statistical index includes at least one of an average, a maximum value, a minimum value, a variance, a deviation of a level of baseline.

16. A method for detecting a sleep condition of a patient as in claim 13,

wherein the pulse waves are detected from one of the wrist and forearm of the patient.

17. A method for diagnosing whether a sleeping patient has sleep apnea syndrome comprising the steps of:

detecting pulse waves from the sleeping body of the patient;

analyzing the pulse waves; and

determining whether the patient has sleep apnea syndrome based on a result of the analysis.

18. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 17, further comprising the step of:

determining whether a type of the sleep apnea syndrome is obstructive sleep apnea based on the result of the analysis.

19. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing creates an envelope of the pulse waves by connecting one of tops and bottoms of the pulse waves and calculates a degree of fluctuation of the envelope, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the fluctuation of the envelope exceeds a predetermined level.

20. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing calculates a degree of fluctuation of peaks of the pulse waves, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the fluctuation of the peaks exceeds a predetermined level.

21. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing calculates a pulse height of each of the pulse wave and a degree of fluctuation of the pulse height, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the fluctuation of the pulse height exceeds a predetermined level.

22. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing calculates a pulse area which is defined by each of the pulse waves, and a degree of variation of the pulse area, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the variation of the pulse area exceeds a predetermined level.

23. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing calculates a pulse length which is a length of each of the pulse waves, and a degree of variation of the pulse length, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the variation of the pulse length exceeds a predetermined level.

24. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the steps of determining include using fluctuation of the pulse waves.

25. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 24,

wherein the step of analyzing calculates a difference between the fluctuation of the pulse waves and fluctuation of pulse waves detected from the patient in an eupneic condition, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the degree of the difference exceeds a predetermined level.

26. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 18,

wherein the step of analyzing creates a first envelope of the pulse wave which connects tops of the pulse waves and a second envelope of the pulse waves which connects bottoms of the pulse waves,

wherein the step of analyzing further calculates a closeness of one of bottoms of the first envelope and corresponding one of tops of the second envelope, and

wherein the steps of determining indicate that the patient has obstructive sleep apnea syndrome if the closeness exceeds a predetermined level.

27. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 17, further comprising the step of:

determining whether a type of the sleep apnea syndrome is central sleep apnea based on the result of the analysis.

28. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 27,

wherein the step of analyzing creates an envelope of the pulse waves by connecting one of tops and bottoms of the pulse waves, and calculates a period of fluctuation of the envelope, and

wherein the steps of determining indicate that the patient has central sleep apnea syndrome if the period exceeds a predetermined length.

29. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 17, further comprising the step of:

determining whether a type of the sleep apnea syndrome is mixed sleep apnea.

30. A method for diagnosing whether a sleeping patient has sleep apnea syndrome as in claim 19,

wherein the step of determining whether the patient has sleep apnea syndrome detects obstructive sleep apnea condition and central sleep apnea condition based on the result of analysis, and

wherein the step of determining the type of the sleep apnea syndrome indicates that the patient has mixed sleep apnea syndrome if the obstructive sleep apnea condition is detected after the central sleep apnea condition is detected.

31. An apparatus for detecting a physiological condition of a patient comprising:

a light emitter for emitting light into the body of the patient;

a pulse sensor for detecting light reflected by the body of the patient and therefore detecting pulse waves from the body of the patient;

a drive circuit for driving the pulse sensor;

a data processing unit for executing a program for creating and analyzing an envelope of the pulse waves and detecting a physiological condition based on a result of the analysis; and

a display unit for displaying a result of the detection.

32. An apparatus for detecting a physiological condition of a patient as in claim 31,

wherein the pulse sensor is designed to be worn on one of the wrist and finger of the patient.

33. An apparatus for detecting a physiological condition of a patient as in claim 31,

wherein the pulse waves are detected from the patient, and

wherein the data processing unit executes the program for detecting a sleep condition of the patient based on the result of the analysis.

34. An apparatus for detecting a physiological condition of a sleeping patient comprising:

a pulse sensor for detecting pulse waves from the patient body, wherein the pulse waves are detected from the sleeping patient;

a drive circuit for driving the pulse sensor;

a data processing unit for executing a program for creating and analyzing an envelope of the pulse waves and detecting a physiological condition based on a result of the analysis, wherein the data processing unit executes the program for detecting a respiratory condition of the patient based on the result of the analysis; and

a display unit for displaying a result of the detection.