Breath monitor

• US 20050113711A1
• Filed: 09/28/2004
• Published: 05/26/2005
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yanai, Kenichi, Ozaki, Noriyuki, Nakatani, Hiroto
• Granted Patent: US 7,306,564 B2
• Time in Patent Office: Days
• US Class Current: 600/534
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/4806 Sleep evaluation A61B5/4821 takes precedence; devices for inducing sleep A61M21/02
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured

Abstract

A breath monitor includes: a plurality of sensors for detecting a load derived from a human lying on a bed and for outputting a sensor signal corresponding to the load; and breath signal computation means. The sensors are disposed under the human with a predetermined arrangement. The breath signal computation means converts each sensor signal to a frequency domain so that a spectrum of each sensor signal is obtained, selects the sensors on the basis of the converted sensor signals, and computes a breath signal on the basis of the sensor signals outputted from the selected sensors.

Claims

1. A breath monitor comprising:

a plurality of sensors for detecting a load derived from a human lying on a bed and for outputting a sensor signal corresponding to the load; and

breath signal computation means,

wherein the sensors are disposed under the human with a predetermined arrangement, and

wherein the breath signal computation means converts each sensor signal to a frequency domain so that a spectrum of each sensor signal is obtained, selects the sensors on the basis of the converted sensor signals, and computes a breath signal on the basis of the sensor signals outputted from the selected sensors.

2. The breath monitor according to claim 1,

wherein the sensor is a pressure sensor so that the sensor detects the load derived from a weight of the human.

3. The breath monitor according to claim 1,

wherein the sensor is a vibration sensor so that the sensor detects the load derived from a vibration of a body movement of the human.

4. The breath monitor according to claim 1,

wherein the breath signal computation means converts the sensor signals by using a fast Fourier transform method.

5. The breath monitor according to claim 1,

wherein the spectrum is a power spectrum having a relationship between an intensity and a frequency of the sensor signal.

6. The breath monitor according to claim 1,

wherein the spectrum is an amplitude spectrum having a relationship between an amplitude and a frequency of the sensor signal.

7. The breath monitor according to claim 1,

wherein the breath signal computation means selects the sensors in such a manner that a peak frequency in the spectrum of each sensor signal is determined, a maximum frequency range having a predetermined frequency width, in which the largest number of peak frequencies of the sensor signals are disposed, is determined, and the sensor signals having the peak frequency disposed in the maximum frequency range are selected.

8. The breath monitor according to claim 7,

wherein the breath signal computation means determines the maximum frequency range by using only the peak frequencies disposed in a predetermined breath frequency range.

9. The breath monitor according to claim 7,

wherein the breath signal computation means computes the breath signal in such a manner that the sensor signals outputted from the selected sensors are classified into a plurality of phase groups having a predetermined phase width on the basis of a phase of the sensor signal, a maximum phase group having the largest number of classified sensor signals is determined, an opposite phase group having the phase shifted by a half period from a center phase of the maximum phase group is determined, all phases of the sensor signals disposed in one of the maximum phase group and the opposite phase group are inverted, and the inverted sensor signals in the one of the phase groups are added to the sensor signals in the other one of the phase groups so that the breath signal is obtained.

10. The breath monitor according to claim 1, further comprising:

determination means for determining a quick movement of the human,

wherein the breath signal includes a plurality of cycles, the number of which is predetermined, and each of which corresponds to one cycle of breathing of the human, and

wherein the determination means arbitrarily selects one cycle of the breath signal, compares an amplitude of the one cycle of the breath signal to an amplitude of another cycle of the breath signal, and determines the quick movement when the amplitude of the one cycle is larger by a predetermined reference value than the amplitude of the other cycle.

11. The breath monitor according to claim 1, further comprising:

determination means for determining a slight movement of the human,

whether the breath signal computation means converts the sensor signals, each of which has a signal intensity larger than a predetermined value so that the sensor signal only derived from the load of the human is selected,

wherein the determination means determines the number of the sensor signals having the signal intensity larger than the predetermined value, and

wherein the determination means determines the slight movement when the number of the sensor signals changes by a predetermined number as time advances.

12. The breath monitor according to claim 1,

whether the breath signal computation means computes the breath signal by using only the sensor signals having a peak frequency in the spectrum disposed in a breath frequency range.

13. The breath monitor according to claim 1, further comprising:

a resistance branch circuit having a sensitivity resistor,

wherein each sensor includes the resistance branch circuit.

14. The breath monitor according to claim 13, further comprising:

a switch for switching a connection between the resistance branch circuit and the sensor.

15. The breath monitor according to claim 14, further comprising:

sensitivity resistance changing means for changing a resistance of the sensitivity resistor in accordance with a sensor characteristic of each sensor to be connected to the resistance branch circuit.

16. Detection equipment for detecting an apnea syndrome, comprising:

breath signal computation means for computing a breath signal on the basis of a change of a load, which corresponds to a body movement of breathing of a person; and

determination means for determining an apnea symptom and a hypopnea symptom of the person on the basis of a periodicity of extremums of an amplitude envelope curve of the breath signal.

17. The detection equipment according to claim 16,

wherein the amplitude envelope curve of the breath signal is obtained from a frequency signal calculated from the breath signal.

18. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

TIMIN(k)<

C1;


TIMAX(k)<

C2;


TIMIN(k−

1)<

C1; and


TIMAX(k−

1)<

C2, and

wherein C1 and C2 are predetermined constant values.

19. The detection equipment according to claim 18,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) have an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) have an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1 and C2 are defined as;

C1=AVMIN+α

; and


C2=AVMAX+α

, and

wherein α

is a predetermined constant value.

20. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

TIMIN(k)<

C1;


TIMAX(k)<

C2;


TIMIN(k+1)<

C1; and


TIMAX(k+1)<

C2, and

wherein C1 and C2 are predetermined constant values.

21. The detection equipment according to claim 20,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) have an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) have an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1 and C2 are defined as;

C1=AVMIN+α

; and


C2=AVMAX+α

, and

wherein α

is a predetermined constant value.

22. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

TIMIN(k+1)<

C1;


TIMAX(k+1)<

C2;


TIMIN(k+2)<

C1; and


TIMAX(k+2)<

C2, and

wherein C1 and C2 are predetermined constant values.

23. The detection equipment according to claim 22,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) have an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) have an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1 and C2 are defined as;

C1=AVMIN+α

; and


C2=AVMAX+α

, and

wherein α

is a predetermined constant value.

24. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

C3<

TIMIN(k)<

C1;


C4<

TIMAX(k)<

C2;


C3<

TIMIN(k−

1)<

C1; and


C4<

TIMAX(k−

1)<

C2, and

wherein C1, C2, C3 and C4 are predetermined constant values.

25. The detection equipment according to claim 24,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) has an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) has an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1, C2, C3 and C4 are defined as;

C1=AVMIN+α

;


C2=AVMAX+α

;


C3=AVMIN−

β

; and


C4=AVMAX−

β

, and

wherein α and

β

are predetermined constant values.

26. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

C3<

TIMIN(k)<

C1;


C4<

TIMAX(k)<

C2;


C3<

TIMIN(k+1)<

C1; and


C4<

TIMAX(k+1)<

C2, and

wherein C1, C2, C3 and C4 are predetermined constant values.

27. The detection equipment according to claim 26,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) has an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) has an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1, C2, C3 and C4 are defined as;

C1=AVMIN+α

;


C2=AVMAX+α

;


C3=AVMIN−

β

; and


C4=AVMAX−

β

, and

wherein α and

β

are predetermined constant values.

28. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time intervals of TIMIN(k) and TIMAX(k) satisfy a condition of;

C3<

TIMIN(k+1)<

C1;


C4<

TIMAX(k+1)<

C2;


C3<

TIMIN(k+2)<

C1; and


C4<

TIMAX(k+2)<

C2, and

wherein C1, C2, C3 and C4 are predetermined constant values.

29. The detection equipment according to claim 28,

wherein the time intervals of TIMIN(k) of the minimum values of MIN(k) has an average time interval defined as

$\mathrm{AVMIN}=\sum _{}^{}$

k=1N⁢

TIMIN⁡

(k)/N,

wherein the time intervals of TIMAX(k) of the maximum values of MAX(k) has an average time interval defined as

$\mathrm{AVMAX}=\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>\mathrm{TIMAX}<br><br>\left(k\right)/N,$

wherein the predetermined constant values of C1, C2, C3 and C4 are defined as;

C1=AVMIN+α

;


C2=AVMAX+α

;


C3=AVMIN−

β

; and


C4=AVMAX−

β

, and

wherein α and

β

are predetermined constant values.

30. The detection equipment according to claim 16, further comprising:

a plurality of sensors for detecting a load derived from a human lying on a bed and for outputting a sensor signal corresponding to the load,

wherein the sensors are disposed under the human with a predetermined arrangement, and

wherein the breath signal computation means converts each sensor signal to a frequency domain so that a spectrum of each sensor signal is obtained, selects the sensors on the basis of the converted sensor signals, and computes the breath signal on the basis of the sensor signals outputted from the selected sensors.

31. The detection equipment according to claim 30,

wherein the spectrum is a power spectrum having a relationship between an intensity and a frequency of the sensor signal.

32. The detection equipment according to claim 30,

wherein the breath signal computation means selects the sensors in such a manner that a peak frequency in the spectrum of each sensor signal is determined, a maximum frequency range having a predetermined frequency width, in which the largest number of peak frequencies in the sensor signals are disposed, is determined, and the sensor signal having the peak frequency disposed in the maximum frequency range is selected.

33. The detection equipment according to claim 32,

wherein the breath signal computation means computes the breath signal in such a manner that the sensor signals outputted from the selected sensors are classified into a plurality of phase groups having a predetermined phase width on the basis of a phase of the sensor signal, a maximum phase group having the largest number of classified sensor signals is determined, an opposite phase group having the phase shifted by a half period from a center phase of the maximum phase group is determined, all phases of the sensor signals disposed in one of the maximum phase group and the opposite phase group are inverted, and the inverted sensor signals in the one of the phase groups are added to the sensor signals in the other one of the phase groups so that the breath signal is obtained.

34. The detection equipment according to claim 16,

wherein the breath signal includes a plurality of cycles, the number of which is predetermined, and each of which corresponds to one cycle of breathing of the person and has an amplitude, and

wherein the amplitude envelope curve is obtained in such a manner that all amplitudes of cycles in the breath signal are interpolated so that the amplitude envelope curve is computed.

35. The detection equipment according to claim 16,

wherein the extremums in the amplitude envelope curve are determined in such a manner that an amplitude envelope curve function is differentiated.

36. The detection equipment according to claim 16,

wherein the extremums in the amplitude envelope curve are determined in such a manner that a difference of the amplitude is changed from positive to negative or from negative to positive at the extremum.

37. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of minimum values, which are defined as MIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMIN(k) satisfies a condition of;

C3<

TIMIN(k)<

C1; and


C3<

TIMIN(k−

1)<

C1, and

wherein C1 and C3 are predetermined constant values.

38. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of minimum values, which are defined as MIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMIN(k) satisfies a condition of;

C3<

TIMIN(k)<

C1; and


C3<

TIMIN(k+1)<

C1, and

wherein C1 and C3 are predetermined constant values.

39. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of minimum values, which are defined as MIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) and the temporally adjacent minimum value of MIN(k−

1) provide a time interval defined as TIMIN(k)=TMIN(k)−

TMIN(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMIN(k) satisfies a condition of;

C3<

TIMIN(k+1)<

C1; and


C3<

TIMIN(k+2)<

C1, and

wherein C1 and C3 are predetermined constant values.

40. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMAX(k) satisfies a condition of;

C4<

TIMAX(k)<

C2; and


C4<

TIMAX(k−

1)<

C2, and

wherein C2 and C4 are predetermined constant values.

41. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMAX(k) satisfies a condition of;

C4<

TIMAX(k)<

C2; and


C4<

TIMAX(k+1)<

C2, and

wherein C2 and C4 are predetermined constant values.

42. The detection equipment according to claim 16,

wherein the amplitude envelope curve includes a plurality of pairs of a maximum value and a minimum value, a pair of which is temporally adjacent each other, and defined as MAX(k) and MIN(k) (k=0, 1, 2, . . . , N), respectively,

wherein the maximum value of MAX(k) is occurred at a time defined as TMAX(k) (k=0, 1, 2, . . . , N),

wherein the minimum value of MIN(k) is occurred at a time defined as TMIN(k) (k=0, 1, 2, . . . , N),

wherein the maximum value of MAX(k) and the temporally adjacent maximum value of MAX(k−

1) provide a time interval defined as TIMAX(k)=TMAX(k)−

TMAX(k−

1),

wherein the determination means determines the apnea symptom and the hypopnea symptom occurred at the time of TMIN(k) in a case where the time interval of TIMAX(k) satisfies a condition of;

C4<

TIMAX(k+1)<

C2; and


C4<

TIMAX(k+2)<

C2, and

wherein C2 and C4 are predetermined constant values.