JP2017018384A - Sleep apnea diagnosis support device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide diagnosis support information of sleep apnea using a smart phone, based on a signal related to a respiratory movement and a signal related to a heart rate.SOLUTION: A sleep apnea diagnosis support device 1 is comprised of a sound sensor 11 and a main body device 12. The sound sensor 11 comprises a sub amplifier circuit for amplifying an analog acoustic signal from a sensing part. A combined gain characteristic of a gain characteristic of the sub amplifier circuit and a gain characteristic of a main amplifier circuit of the main body device 12 has a peak of a gain larger than a gain of 20 Hz-20 kHz in a range of 0.05 Hz-3 Hz. In the main body device 12, an A/D conversion circuit converts the analog acoustic signal which is amplified in the main amplifier circuit into a digital acoustic signal. A processing circuit extracts from the digital acoustic signal, a component related to a respiratory movement as a respiratory movement signal, then based on the respiratory movement signal, creates diagnosis support information about sleep apnea.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sleep apnea diagnosis support technique for acquiring diagnosis support information about sleep apnea using a sound sensor and a main device.

Conventionally, a system for detecting sleep apnea, which is referred to in Patent Document 1, is known.
In this system, physiological parameters of a living subject can be monitored at a detection station.
This system includes a plurality of sound sensors and transmission means provided in a detection station.
Each sound sensor detects, for example, a respiratory motion of the subject.
The data (acoustic signal) detected by each sound sensor is transmitted to the data receiving station by the transmitting means.
At the data receiving station, sleep apnea can be detected.
In this system, a so-called smart phone is used as a data receiving station from the viewpoint that measurement is familiar.

JP2013-541973 Special table 2013-531522

  By the way, in a smartphone, an acoustic signal acquired from an acoustic input terminal is input to an acoustic amplifier circuit. The human audible frequency is 20 Hz-20 kH, and the cut-off frequency on the low frequency side of a normal smartphone acoustic amplifier circuit is 20 Hz.

  Therefore, even if a sound sensor such as a microphone is attached to the acoustic input terminal to detect respiratory motion or heart sound, it is extremely difficult to acquire an acoustic signal having a respiratory motion frequency (for example, 0.2 Hz).

  In order to acquire an acoustic signal having a frequency of respiratory motion, the heart sound signal acquisition device described in Patent Document 2 transmits the acoustic signal from the sound sensor to a smartphone, for example, on a carrier signal of 6 kHz-20 kHz.

  In the technique of Patent Literature 2, the smartphone can demodulate an acoustic signal from a received signal and detect respiratory motion and heart sound from the demodulated acoustic signal. However, this technique requires a modulator and a transmitter in addition to the smartphone, so that there is a problem that the circuit configuration becomes complicated.

  The object of the present invention is to detect the sound of the subject's chest with a sound sensor and process it in a smartphone. By configuring the respiratory motion signal that is not detected or difficult to detect by the smartphone alone, It is to generate diagnostic support information about high sleep apnea.

Usually, in a smartphone having an input terminal for an analog sound signal, an analog amplifier circuit provided in the sound input unit has a frequency characteristic corresponding to an audible sound frequency.
For this reason, even if the acoustic signal of the chest acquired from the subject is detected by the sound sensor and processed by the smartphone, it is extremely difficult to extract a signal related to respiratory motion (for example, about 0.2 Hz) from the acoustic signal. is there.
The inventor enhances (or amplifies) the low-frequency component of the chest acoustic signal acquired from the subject before processing with the smartphone, and if the increased signal is processed with the smartphone, the inventor can easily breathe. The present invention has been made based on the knowledge that signals relating to motion can be extracted.

(1)
A sound sensor in which a sensing unit is disposed directly or indirectly in close contact with a subject's body, and a main amplifier circuit that amplifies an analog acoustic signal from the sound sensor, an A / D conversion circuit, and an arithmetic processing unit A sleep apnea diagnosis support device equipped with a main unit:
The sound sensor is
The sensing unit that detects sound and outputs an analog sound signal;
and,
A sub-amplifier circuit for amplifying the analog acoustic signal from the sensing unit;
Comprising:
The combined gain characteristic of the gain characteristic of the sub-amplifier circuit and the gain characteristic of the main amplifier circuit is
Exhibit characteristics with a gain peak between 0.05 Hz and 3 Hz, which is greater than the gain of 20 Hz-20 kHz;
In the main unit,
The A / D converter circuit converts the analog sound signal amplified by the main amplifier circuit into a digital sound signal,
The arithmetic processing unit includes:
A component related to respiratory motion is extracted from the digital acoustic signal as a respiratory motion signal, and diagnostic support information about sleep apnea is generated based on the respiratory motion signal;
Sleep apnea diagnosis support device.

Usually, the high-frequency cutoff frequency of the sub-amplifier circuit is smaller than the low-frequency cutoff frequency of the main amplifier circuit.
There may be a case where the low cutoff frequency of the main amplifier circuit is smaller than 20 Hz (for example, smaller than 3 Hz). In this case, the high-frequency cutoff frequency of the sub-amplifier circuit may be greater than the low-frequency cutoff frequency of the main amplifier circuit.

(2)
In the sleep apnea diagnosis support apparatus according to (1):
The arithmetic processing unit further extracts a component relating to a heart sound as a heart sound signal from the digital sound signal, and detects the presence or absence of respiratory effort,
Generating diagnostic support information on whether the sleep apnea is central apnea or obstructive apnea based on the respiratory motion signal, the heart sound signal, and the detection result of the presence or absence of the respiratory effort;
Sleep apnea diagnosis support device.
In the present invention, respiratory effort refers to the movement of respiratory muscles such as the intercostal muscles and the diaphragm without air entering and exiting.

(3)
In the sleep apnea diagnosis support apparatus according to (1):
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion signal as diagnosis support information;
Sleep apnea diagnosis support device.
(4)
In the sleep apnea diagnosis support apparatus according to (1):
The main unit further comprises a display;
On the display,
Display the number of times the apnea duration exceeds the specified duration as diagnostic support information;
Sleep apnea diagnosis support device.
The display also displays the length of apnea (for example, the total apnea time length during the operation period of the sleep apnea diagnosis support apparatus of the present invention, the length of apnea time per time). can do.

(5)
In the sleep apnea diagnosis support apparatus according to (2):
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion signal and the waveform of the heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device.

(6)
In the sleep apnea diagnosis support apparatus according to (2):
The main unit further comprises a display;
On the display,
Display the number of times the apnea time length exceeded the predetermined time length when respiratory effort is detected as diagnostic support information about obstructive apnea,
Display the number of times the apnea duration exceeds a predetermined duration when heart sounds are detected and respiratory effort is not detected as diagnostic support information for central apnea;
Sleep apnea diagnosis support device.

(7)
The sleep apnea diagnosis support apparatus according to claim 1, wherein the sub-amplifier circuit is supplied with power from the main unit.
The sub-amplifier circuit includes an impedance circuit provided between input terminals and an amplifier provided in the next stage of the impedance circuit;
The impedance circuit is low impedance when the frequency of the input signal is high and high impedance when the frequency of the input signal is low;
Sleep apnea diagnosis support device.

(8)
In the sleep apnea diagnosis support apparatus according to any one of (1) to (7):
The main unit is
An acoustic recording apparatus having the main amplification circuit and the A / D conversion circuit;
and,
A computer having the arithmetic processing unit;
A sleep apnea diagnosis support device comprising:

In the present invention, as shown in (1)-(8), the arithmetic processing unit
A component related to respiratory motion is extracted from the digital acoustic signal as a respiratory motion signal, and diagnostic support information about sleep apnea can be generated based on the respiratory motion signal.
Moreover, in this invention, as shown to (9)-(16), an arithmetic processing unit is as follows.
A component related to respiratory motion and heart sound is extracted as a respiratory motion / heart sound signal from the digital acoustic signal, and diagnostic support information about sleep apnea can be generated based on the respiratory motion / heart sound signal.

(9)
A sound sensor in which a sensing unit is disposed directly or indirectly in close contact with a subject's body, and a main amplifier circuit that amplifies an analog acoustic signal from the sound sensor, an A / D conversion circuit, and an arithmetic processing unit A sleep apnea diagnosis support device equipped with a main unit:
The sound sensor is
The sensing unit that detects sound and outputs an analog sound signal;
and,
A sub-amplifier circuit for amplifying the analog acoustic signal from the sensing unit;
Comprising:
The high-frequency cutoff frequency of the sub-amplifier circuit is smaller than the low-frequency cutoff frequency of the main amplifier circuit,
And,
A combined gain characteristic of the gain characteristic of the sub-amplifier circuit and the gain characteristic of the main amplifier circuit indicates a characteristic having a gain peak larger than a gain of 20 Hz-20 kHz between 0.05 Hz and 3 Hz;
In the main unit,
The A / D converter circuit converts the analog sound signal amplified by the main amplifier circuit into a digital sound signal,
The arithmetic processing unit includes:
A component relating to respiratory motion and heart sound is extracted from the digital acoustic signal as a respiratory motion / heart sound signal, and diagnostic support information about sleep apnea is generated based on the respiratory motion / heart sound signal;
Sleep apnea diagnosis support device.

(10)
In the sleep apnea diagnosis support apparatus according to (9):
The arithmetic processing unit detects the presence or absence of respiratory effort,
Generating diagnostic support information as to whether the sleep apnea is central apnea or obstructive apnea based on the respiratory motion / heart sound signal and the detection result of the presence or absence of the respiratory effort;
Sleep apnea diagnosis support device.

(11)
In the sleep apnea diagnosis support apparatus according to (9):
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion / heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device.

(12)
In the sleep apnea diagnosis support apparatus according to (9):
The main unit further comprises a display;
On the display,
Display the number of times the apnea duration exceeds the specified duration as diagnostic support information;
Sleep apnea diagnosis support device.

(13)
In the sleep apnea diagnosis support apparatus according to (10):
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion / heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device.

(14)
In the sleep apnea diagnosis support apparatus according to (10):
The main unit further comprises a display;
On the display,
Display the number of times the apnea time length exceeded the predetermined time length when respiratory effort is detected as diagnostic support information about obstructive apnea,
Display the number of times the apnea duration exceeds a predetermined duration when heart sounds are detected and respiratory effort is not detected as diagnostic support information for central apnea;
Sleep apnea diagnosis support device.

(15)
In the sleep apnea diagnosis support apparatus according to (9), wherein the sub-amplifier circuit is supplied with power from the main body apparatus:
The sub-amplifier circuit includes an impedance circuit provided between input terminals and an amplifier provided in the next stage of the impedance circuit;
The impedance circuit is low impedance when the frequency of the input signal is high and high impedance when the frequency of the input signal is low;
Sleep apnea diagnosis support device.

(16)
In the sleep apnea diagnosis support apparatus according to any one of (9) to (15):
The main unit is
An acoustic recording apparatus having the main amplifier circuit and the A / D conversion circuit;
and,
A computer having the arithmetic processing unit;
A sleep apnea diagnosis support device comprising:
The main unit is
An acoustic recording apparatus having the main amplifier circuit and the A / D conversion circuit;
and,
A computer having the arithmetic processing unit;
A sleep apnea diagnosis support device comprising:

If the frequency of the peak of the composite gain is too large or too small, the respiratory motion signal is not sufficiently amplified, and the respiratory motion signal is buried in a signal having a higher frequency than the respiratory motion signal, such as a heart sound signal.
Therefore, in the present invention, the peak of the composite gain is set so as to exist between 0.05 Hz and 3 Hz as described above.
A value of 0.08 Hz or 0.1 Hz can also be adopted as the lower limit of the region where the peak of the composite gain exists. Here, 0.1 Hz corresponds to the minimum apnea time of 10 seconds defined by the American Academy of Sleep Medicine (AASM).
A value of 1 Hz or 2 Hz can also be adopted as the upper limit of the region where the peak of the composite gain exists. Here, 1 Hz corresponds to 60 heartbeats / minute.
By setting the peak of the composite gain as described above, the composite gain exhibits a characteristic that a value of 2 Hz or less is higher than a value of 20 Hz or more.

  According to the present invention, an analog acoustic signal is detected by a sensing unit arranged in close contact with a subject's body directly or indirectly, and the main unit (the main unit is configured from a smartphone, or configured from an acoustic recording device and a computer. )), Signal components related to respiratory motion are extracted. Then, sleep apnea diagnosis support information with high reliability is generated from the extracted signal, and this information is provided to a doctor or the like.

  According to the present invention, sleep apnea diagnosis support information regarding whether sleep apnea is obstructive apnea or central apnea is also provided to a doctor or the like.

FIG. 1 is a diagram showing a use state of the sleep apnea diagnosis support apparatus of the present invention. FIG. 2 is an overall view of the sleep apnea diagnosis support apparatus of the present invention. FIG. 3 is a diagram illustrating a sensing unit of the sound sensor of FIG. FIG. 3A is a diagram showing the tip (plug) of the cable drawn from the sensing unit. FIG. 3B is a diagram illustrating an example of a sub-amplifier circuit incorporated in the plug. FIG. 3C shows another example of the sub-amplifier circuit built in the plug. FIG. 4 is a diagram showing an example of a main device used in the sleep apnea diagnosis support apparatus of the present invention. FIG. 4A is an explanatory diagram of an internal circuit of the main device. FIG. 4B is a diagram illustrating a display provided in the main device. FIG. 5 is a diagram showing a basic configuration of a processing circuit in the sleep apnea diagnosis support apparatus of the present invention. FIG. 6A is a diagram illustrating an example of a processing circuit in the sleep apnea diagnosis support apparatus of the present invention. FIG. 6B is a diagram showing another example of the processing circuit in the sleep apnea diagnosis support apparatus of the present invention. FIG. 7A is a diagram showing the frequency characteristics of the main amplifier circuit incorporated in the internal circuit of the main unit of FIG. FIG. 7B is a diagram showing frequency characteristics of the sub-amplifier circuit built in the plug shown in FIG. FIG. 8 is a diagram illustrating the frequency characteristics of the main amplifier circuit, the frequency characteristics of the sub amplifier circuit, and the combined frequency characteristics of the frequency characteristics of the main amplifier circuit and the frequency characteristics of the sub amplifier circuit. FIG. 9 is a flowchart showing a flow for detecting sleep apnea. FIG. 10 is a flowchart showing a flow for detecting whether sleep apnea is central apnea or obstructive apnea. FIG. 11 is a flowchart showing a flow for detecting whether the patient has central apnea or obstructive apnea by taking in the determination of the presence or absence of snoring. FIG. 12 is a flowchart showing a flow for detecting whether there is central apnea or obstructive apnea by taking in the determination of the presence or absence of body movement. FIG. 13A shows a respiratory motion signal RMS without respiratory effort. FIG. 13B is a diagram showing a respiratory motion signal RMS with respiratory effort. FIG. 14A shows a respiratory motion signal without sleep apnea. FIG. 14B is a diagram showing a respiratory motion signal having sleep apnea. FIG. 15 is an overall view of the sleep apnea diagnosis support apparatus according to the present invention, in which the main body apparatus includes a voice recording terminal and a computer. FIG. 16A is an explanatory diagram of an internal circuit of the acoustic recording device used in the sleep apnea diagnosis support apparatus of FIG. FIG. 16B is a diagram showing the tip (plug) of the cable drawn out from the sensing unit. FIG. 17 is an explanatory diagram of an internal circuit of a computer used in the sleep apnea diagnosis support apparatus of FIG.

FIG. 1 is a diagram illustrating a use state of the sleep apnea diagnosis support apparatus 1 according to the present invention, and FIG. 2 is a diagram illustrating the entire sleep apnea diagnosis support apparatus.
As shown in FIG. 2, the sound sensor 11 includes a sensing unit 111, an output terminal unit 112, a sub amplification circuit 113, and a cable 114.

The sensing unit 111 can detect an analog acoustic signal AS (which includes a respiratory motion signal and a heart sound signal, or further includes a respiratory sound signal BSS).
As shown in FIG. 1, the sensing unit 111 is used by being placed in close contact with the body of the subject M directly or indirectly (through a sheet or a subject's clothes).

In the present embodiment, the sensing unit 111 has an elongated plate shape, and the sensing unit 111 is provided with a plurality of ventilation holes.
A piezoelectric element 1111 is provided at the center of the sensing unit 111. The piezoelectric element 1111 can detect an analog acoustic signal AS (including a respiratory motion signal and a heart sound signal, or further including a respiratory sound signal BSS) propagating through the plate 1112.

  As shown in FIG. 3A, the output terminal portion 112 is a plug formed at the end of the cable 114 drawn from the piezoelectric element 1111. A sub-amplifier circuit 113 is accommodated in this plug. When a capacitive sound sensor is used as in the present embodiment, a high input impedance sub-amplifier circuit is usually used.

  In FIG. 3A, the plug (output terminal portion 112) terminal includes a speaker LEFT terminal SP_LT, a speaker RIGHT terminal SP_RT, a ground (earth) terminal GND_T, and a microphone terminal MIC_T from the tip.

  An acoustic signal line (SGN) drawn from the piezoelectric element 1111 is connected to an input terminal of the sub-amplifier circuit 113. The output terminal of the sub amplifier circuit 113 is connected to the microphone terminal MIC_T. The ground terminal (GND) of the sub-amplifier circuit 113 is connected to the ground line (GND_LINE).

FIG. 3B illustrates an example of the sub amplifier circuit 113. In FIG. 3B, a grounded-emitter bipolar transistor TR is used as an amplifying element. Although not illustrated, a Darlington-connected transistor can be used as the sub-amplifier circuit 113.
An analog acoustic signal AS (a signal from the piezoelectric element 1111) given between the terminals a1 and a2 is amplified with an amplification factor determined by the values of the resistors R1-R4 (the amplified signal is denoted by AS_A).
The operation of the sub-amplifier circuit 113 will be described later (see FIG. 7).
Note that a field effect transistor (FET) can also be used as the sub-amplifier circuit 113.

FIG. 3C illustrates another example of the sub amplifier circuit 113.
In the sub-amplifier circuit 113 of FIG. 3C, a low frequency gain enhancer 1132 (LFGE: Low Frequency Gain) is placed in front of the amplifier (AMP 1131) including the bipolar transistor TR and resistors R1-R4 shown in FIG. 3B. Enhancer) is provided.
The low frequency gain enhancer 1132 includes a series circuit (impedance Zx) of a capacitance Cx and a resistor Rx.
The impedance Zx is represented by RX + 1 / (jωCx), and decreases as the signal frequency increases.
Therefore, the high frequency component of the analog acoustic signal AS easily flows into the impedance Zx, the base current of the transistor TR decreases, and the gain of the sub-amplifier circuit 113 decreases. On the other hand, the low frequency component of the analog acoustic signal AS does not easily flow into the impedance Zx, the base current of the transistor TR increases, and the gain of the sub-amplifier circuit 113 increases.

  An analog acoustic signal AS (a signal from the piezoelectric element 1111) given between the terminals a1 and a2 is amplified at an amplification factor determined by the values of the resistors R1 to R4. The sub-amplifier circuit 113 amplifies the low frequency inaudible frequency component of the analog acoustic signal AS from the sensing unit 111 and outputs the analog acoustic signal AS_A.

The terminal b1 (microphone terminal MIC_T) functions as an output terminal of the sub-amplifier circuit 113 and also functions as a power supply terminal (drive voltage V_DRV) of the sub-amplifier circuit 113. Reference numerals a2 and b2 denote ground terminals GND_T, which are connected to the ground (earth) GND of the sub-amplifier circuit 113.
Although not shown, the sub-amplifier circuit 113 can also be driven by a battery.

FIG. 4A is an explanatory diagram of an internal circuit of the main device 12.
4A, the main body device 12 includes an input terminal portion 121 for an analog acoustic signal AS_A. The main unit 12 includes a main amplifier circuit 122, an A / D conversion circuit 123, a processing circuit (arithmetic processing unit in the present invention) 124, a memory 125, and a display circuit 126, and includes a display 127.
In FIG. 4A, the power supply voltage VB of the main device 12 is supplied as the drive voltage V_DRV to the terminal b1 in FIG. 3B through the resistor Rb.
The input terminal portion 121 is a jack formed on the upper edge of the main body device 12 and is connected to the output terminal portion 112 (plug) of the sound sensor 11.

The main amplifier circuit 122 amplifies the audible frequency component (20 Hz-20 kHz) of the analog acoustic signal AS_A and outputs it as an analog acoustic signal AS_AA having a frequency characteristic that attenuates a non-audible frequency component (frequency component lower than 20 Hz).
The A / D conversion circuit 123 converts the analog acoustic signal AS_AA output from the main amplifier circuit 122 into a digital acoustic signal DS. In the present embodiment, the digital acoustic signal DS is stored in the memory 125 (RAM).

The processing circuit 124 processes the digital acoustic signal DS stored in the memory 125 (RAM). The processing circuit 124 is a circuit including a CPU in this embodiment. The processing circuit 124 can include other processors in addition to the CPU.
In the present embodiment, a program for operating the processing circuit 124 is stored in the memory 125 (ROM).
In FIG. 4B, the display 127 displays the digital acoustic signal DS and the respiratory motion / heart sound signal (RM / HB_S).

FIG. 5 is a diagram showing a basic configuration of the processing circuit 124 in the sleep apnea diagnosis support apparatus of the present invention.
As shown in FIG. 5, the processing circuit 124 performs preprocessing on the digital acoustic signal DS (A1). This pre-processing includes filtering processing, and the filtering processing is, for example, extraction processing of a respiratory motion / heart sound signal (RM / HB_S) for the digital audio signal DS. For this extraction process, refer to S120 in FIG. 9, S220 in FIGS. 10 and 12, and S320 in FIG.
Next, the processing circuit 124 performs analysis processing (A2).
This analysis process consists of measuring the non-breath detection time that does not depend on sleep apnea, measuring the number of sleep apneas (or measuring the number of central apneas and obstructive apneas), and measuring the number of snores This is processing related to measurement of body movement time (and the number of body movements).
For these measurements, refer to S130 to S180 in FIG. 9, S230 to S290 in FIG. 10, S330 to S340 in FIG. 11, and S211 to S217 and S230 to S290 in FIG.

Further, the processing circuit 124 performs output information generation processing (A3).
The output information generation process includes measured non-sleep apnea detection time, sleep apnea count (or central apnea count and obstructive apnea count), snore count, body It is the movement time (and the number of body movements).
For the output information generation processing, refer to S170 and S180 in FIG. 9, S270 to S290 in FIG. 10, S340 in FIG. 11, and S217 and S270 to S290 in FIG.
It should be noted that the event, that is, the above-described sleep non-apnea non-detection state (eg, sputum), sleep apnea, snoring, body movement occurrence time, duration, etc. as diagnostic support information INF as necessary It can be displayed on the display 127.

A specific example in which the functional blocks in FIG. 5 are simplified will be described with reference to FIGS.
The functional block in FIG. 6A shows the processing for transferring the data related to the respiratory motion / heart sound signal (RM / HB_S) to the display circuit 126 by the processing circuit 124.
In FIG. 6A, the respiratory motion / heart sound signal (RM / HB_S) is extracted from the digital acoustic signal DS, and the waveforms of these signals are displayed.
The processing circuit 124 performs a low-pass filtering process on the digital acoustic signal DS, and extracts a respiratory motion / heart sound signal (RM / HB_S) from which the high-frequency component has been removed from the digital acoustic signal DS (B1).

Then, the processing circuit 124 performs a transfer process of the respiratory motion / heart sound signal (RM / HB_S) to the display circuit 126 (B2).
The processing circuit 124 can display the waveform related to the respiratory motion / heart sound signal (RM / HB_S) on the display 127 as the diagnosis support information INF. In this case, the waveform of the digital acoustic signal DS can also be displayed on the display 127.
The processing circuit 124 can store the respiratory motion / heart sound signal (RM / HB_S) in the memory 125 (RAM).
The processing circuit 124 can read the respiratory motion / heart sound signal (RM / HB_S) from the memory 125 and transfer the respiratory motion / heart sound signal (RM / HB_S) to the display circuit 126.
A doctor or the like can make a diagnosis about sleep apnea by referring to the diagnosis support information INF.

The functional block in FIG. 6B shows an operation for detecting the presence or absence of respiratory motion by the processing circuit 124.
In FIG. 6B, the processing circuit 124 extracts a respiratory motion / heart sound signal (RM / HB_S) from the digital acoustic signal DS, displays the waveform of these signals, and outputs a result of determination of the presence or absence of respiratory effort. .
The processing circuit 124 performs low-pass filtering processing on the digital acoustic signal DS, and performs extraction processing of the respiratory motion / heart sound signal (RM / HB_S) from which the high-frequency component has been removed from the digital acoustic signal DS (C1).
The processing circuit 124 performs FFT processing on the respiratory motion / heart sound signal (RM / HB_S), and integrates the power spectral density (PSD) of the respiratory effort during the apnea period (C2).

The processing circuit 124 monitors the integrated value of the power spectral density (PSD), and performs a process for determining whether there is respiratory effort (C3). Specifically, the processing circuit 124 determines that there is respiratory effort when the integrated value of the power spectral density (PSD) exceeds a preset value within a predetermined time.
When the processing circuit 124 determines that there is respiratory effort, the processing circuit 124 can also output the number of respiratory efforts as diagnosis support information INF on the display.
A doctor or the like can make a diagnosis about sleep apnea with reference to the diagnosis support information INF.
In this case, the display circuit 126 can display the respiratory motion / heart sound signal (RM / HB_S) or the digital acoustic signal DS.

FIG. 7A shows the frequency characteristics of the main amplifier circuit 122.
In this embodiment, the main amplifier circuit 122 has a cutoff frequency of 20 Hz on the low frequency side.
FIG. 7B shows frequency characteristics of the sub-amplifier circuit 113 of the sound sensor 11. In the present embodiment, the cutoff frequency on the high frequency side of the sub-amplifier circuit 113 is about 2 Hz.

FIG. 8 shows the frequency characteristic (solid line) of the main amplifier circuit 122, the frequency characteristic (broken line) of the sub-amplifier circuit 113, and the combined frequency characteristic (dashed line).
As can be seen from the composite frequency characteristic (dashed line) in FIG. 8, the main amplifier circuit 122 and the sub-amplifier circuit 123 cooperate to increase the respiratory motion gain of, for example, a frequency of about 0.2 Hz. The gain is increased by about 20 dB.

FIG. 9 is a flowchart showing a first operation example of the processing circuit 124, and is applied to detection of sleep apnea.
The processing circuit 124 is driven by a program stored in the ROM of the memory 125.

For example, when the processing circuit 124 acquires the digital acoustic signal DS (S110), the processing circuit 124 performs filtering processing on the digital acoustic signal DS, and performs extraction processing of the respiratory motion / heart sound signal (RM / HB_S) on the digital acoustic signal DS (S120). ).
In the present embodiment, the digital acoustic signal DS acquired in S110 is data detected by the sound sensor 11 in real time, but may be past data stored in the memory 125.
Next, the processing circuit 124 detects the respiration non-detection time (S130), and determines whether or not the respiration non-detection time continues for a predetermined time (S140).
The non-breathing detection time may be an apnea time or may be a time when the sound sensor 11 is not placed in close contact with the subject's body.

In S140, when the respiration non-detection time does not continue for a certain time (“NO” in S140), the processing circuit 124 ends the process.
When the apnea time continues for a certain time (“YES” in S140), the processing circuit 124 determines whether or not a respiratory effort waveform has been detected (S150).
When the respiratory effort waveform is detected in S150 (“YES” in S150), the processing circuit 124 increments the value of the counter for counting the number of sleep apneas (not shown) by “1”, and the display 127 supports diagnosis. Information INF is displayed (S180).

  When the respiratory effort waveform is not detected in S150 (“NO” in S150), the processing circuit 124 determines whether or not the heart sound signal HBS is detected in the respiratory motion / heart sound signal (RM / HB_S) (S160). ).

In S160, when the heart sound signal HBS is detected during the respiratory motion / heart sound signal (RM / HB_S) (“YES” in S160), the processing circuit 124 determines the value of the counter for counting the number of sleep apneas (not shown). Is incremented by "1" and displayed as diagnosis support information INF on the display 127 (S180).
In S160, when the heart sound signal HBS is not detected in the respiratory motion / heart sound signal (RM / HB_S) (“NO” in S160), the breathing non-detection time not due to sleep apnea is displayed on the display 127 as diagnostic support information INF. Is integrated and displayed (S170).
“Respiration non-detection time that does not depend on sleep apnea” is, for example, the time of midway awakening or the time when the sensor is not in close contact with the subject's body (eg, wrinkles). These are times that should be excluded from sleep time.

Note that the value of the counter for counting described above may be the total number of times within a predetermined time or the number of times per unit time.
Although not shown, by measuring body movement, the time from the time when the subject enters the sleep state (sleep onset time) to the time when the subject leaves the sleep state (wakeup time) is measured. To do. Then, the total sleep time is obtained by subtracting the above-mentioned “breath non-detection time not dependent on sleep apnea” from this measurement time. Thereby, the total number of times in the sleep state and / or the number of times per unit time can be obtained, and these can be displayed on the display 127.

FIG. 10 is a flowchart showing a second operation example of the processing circuit 124. When sleep apnea is detected, it is detected whether the sleep apnea is central apnea or obstructive apnea. Applied.
The processing circuit 124 is driven by a program stored in the ROM of the memory 125.

For example, when the processing circuit 124 acquires the digital acoustic signal DS (S210), the processing circuit 124 performs filtering processing on the digital acoustic signal DS and performs extraction processing of the respiratory motion / heart sound signal (RM / HB_S) from the digital acoustic signal DS (S220). ). The digital acoustic signal DS acquired in S210 may be data detected by the sound sensor 11 in real time.
Next, the processing circuit 124 detects the apnea time (S230), and determines whether or not the apnea time continues for a certain time (S240).
In S240, when it does not continue for a certain period of time ("NO" in S240), the process ends.
When the apnea time continues for a certain time (“YES” in S240), it is determined whether or not a breathing effort waveform is detected (S250).
When a respiratory effort waveform is detected in S250 (“YES” in S250), it is counted as obstructive apnea, and the value of a counter for counting the number of obstructive apneas not shown is displayed as diagnosis support information INF on the display 127. It is displayed (S290).

In S250, when the respiratory effort waveform is not detected (“NO” in S250), it is determined whether or not the heart sound signal HB is detected (S260).
When the heart sound signal HBS is detected in the respiratory motion / heart sound signal (RM / HB_S) in S260 (“YES” in S260), it is counted as a central apnea and is used for counting the number of central apneas not shown. The counter value is displayed on the display 127 as diagnosis support information INF (S270).
In S260, when the heart sound signal HBS is not detected in the respiratory motion / heart sound signal (RM / HB_S) (“NO” in S260), the respiratory non-detection time not due to sleep apnea is displayed on the display 127 as diagnostic support information INF. Is integrated and displayed (S280).
Note that the value of the counter for counting described above may be the total number of times within a predetermined time or the number of times per unit time.

  Although not shown, by measuring body movement, the time from the time when the subject enters the sleep state (sleep onset time) to the time when the subject leaves the sleep state (wakeup time) is measured. To do. Then, the total sleep time is obtained by subtracting the above-mentioned “breath non-detection time not dependent on sleep apnea” from this measurement time. Thereby, the total number of times in the sleep state and / or the number of times per unit time can be obtained, and these can be displayed on the display 127.

When a doctor or the like determines whether the patient has central apnea or obstructive apnea, the presence or absence of snoring can be incorporated.
FIG. 11 is a flowchart for detecting the presence or absence of snoring.
For example, when the processing circuit 124 acquires the digital sound signal DS (S310), the processing circuit 124 performs filtering processing on the digital sound signal DS, and performs extraction processing of the breathing sound signal BSS on the digital sound signal DS (S320).
In the present embodiment, the digital acoustic signal DS acquired in S310 is data detected by the sound sensor 11 in real time, but may be past data stored in the memory 125.
Next, the processing circuit 124 determines whether a snoring waveform has been detected (S330).
When the snoring waveform is detected in S330, the processing circuit 124 counts as snoring, and displays the value of the counter for counting the number of snoring (not shown) on the display 127 as diagnosis support information INF (S340).
If the snoring waveform is not detected in S330 ("NO" in S330), the snoring detection process is terminated.
Note that the value of the counter for counting described above may be the total number of times within a predetermined time or the number of times per unit time.

FIG. 12 is a flowchart showing a fourth operation example of the processing circuit 124.
In the fourth operation example, when the digital audio signal exceeds a predetermined value, the body movement can be recognized, so that the processing circuit 124 can stop the operation related to generation of support information related to sleep apnea.

For example, when the processing circuit 124 acquires the digital acoustic signal DS (S210), the processing circuit 124 detects the amplitude of the digital acoustic signal DS (S211), and determines whether the amplitude exceeds a predetermined value (S212). Specifically, based on the average value of the amplitude of the digital acoustic signal DS, it is determined that the amplitude of the digital acoustic signal DS exceeds a predetermined value.
When the amplitude of the digital acoustic signal DS exceeds the predetermined value T1 in S212 (“YES” in S212), the measurement of the body movement time measurement timer is started (S213).

Then, the amplitude of the digital audio signal is detected after a certain time (S214), and it is determined whether the amplitude of the digital audio signal is equal to or smaller than a predetermined value T2 (T2: T2 ≦ T1) (S215).
In S215, when the amplitude of the digital audio signal is not equal to or less than the predetermined value T2, the process returns to S214, and after detecting a certain period of time again, the amplitude of the digital audio signal is detected. Is determined (S215).
In S215, when the amplitude of the digital audio signal is equal to or smaller than the predetermined value T2, the time measurement of the body movement time measurement timer is ended (S216), the body movement is counted, and the value of the counter for counting the number of body movements (not shown) Is displayed on the display 127 as diagnosis support information INF (S217).
The value of the counter for counting described above may be the total number of times within a predetermined time or the number of times per unit time.
The time when the subject enters the sleeping state (sleeping time) can be detected, and the total number of times and / or the number of times per unit time in the sleeping state can be displayed as “number of times per unit time”.

Although not shown, by measuring body movement, the time from the time when the subject enters the sleep state (sleep onset time) to the time when the subject leaves the sleep state (wakeup time) is measured. To do. Then, the total sleep time is obtained by subtracting the above-mentioned “breath non-detection time not dependent on sleep apnea” from this measurement time. Thereby, the total number of times in the sleep state and / or the number of times per unit time can be obtained, and these can be displayed on the display 127.
Note that the processing of S220 to S290 is the same as the third operation example shown in FIG.

13 and 14 show actual measurement examples in the present invention.
FIG. 13A is a diagram showing an example of the digital acoustic signal DS and the respiratory motion / heart sound signal (RM / HB_S) detected by the sound sensor 11 having the sub-amplifier circuit 113 shown in FIG. .
FIG. 13B is a diagram showing an example of the digital acoustic signal DS and the respiratory motion / heart sound signal (RM / HB_S) detected by the sound sensor 11 having the sub-amplifier circuit 113 shown in FIG. .
The sub-amplifier circuit 113 shown in FIG. 3C includes an amplifier 1131 and a low-frequency gain enhancer 1132 provided in the preceding stage.
In FIG. 13B, the low frequency component of the respiratory motion / heart sound signal (RM / HB_S) is enhanced, and the difference between the respiratory motion and the heart sound clearly appears in the waveform diagram of RM / HB_S. Note the difference in amplitude ratio between RMS and HBS in RM / HB_S in FIG. 13A and RM / HB_S in FIG.

FIG. 14A is a diagram illustrating an example of a digital acoustic signal DS and a respiratory motion / heart sound signal (RM / HB_S) of a subject who does not have sleep apnea.
FIG. 14B is a diagram showing an example of a digital acoustic signal DS and a respiratory motion / heart sound signal (RM / HB_S) of a subject who exhibits a central sleep apnea symptom.
FIG. 14C is a diagram illustrating an example of a digital acoustic signal DS and a respiratory motion / heart sound signal (RM / HB_S) of a subject who exhibits symptoms of obstructive sleep apnea.
In FIG. 14C, since respiratory effort appears in the respiratory movement / heart sound signal (RM / HB_S) (see the downward arrow in RM / HB_S), it can be seen that sleep apnea is obstructive.

FIG. 15 is an explanatory view showing another embodiment of the sleep apnea diagnosis support apparatus of the present invention using a computer having an IC recorder and a display as the main apparatus.
In the present embodiment, the sleep apnea diagnosis support device 2 includes a sound sensor 21 and a main device 22, and the main device 22 includes an acoustic recording device 221 and a computer 222.
The sound sensor 21 includes a sensing unit 211, an output terminal unit 212, a sub-amplifier circuit 213, and a cable 214.

The sound sensor 21 has the same configuration as that of the sound sensor 11 described in FIGS. 2 and 3, and the sensing unit 211, the output terminal unit 212, the sub-amplifier circuit 213, and the cable 214 are the same as the sensing unit described in FIGS. 111, the output terminal unit 112, the sub-amplifier circuit 113, and the cable 114, respectively.
Further, the piezoelectric element 2111 and the plate 2112 in the present embodiment correspond to the piezoelectric element 1111 and the plate 1112 shown in FIGS.
The sub-amplifier circuit 213 amplifies the inaudible frequency component of the analog acoustic signal AS (signal from the piezoelectric element 2111), and outputs the analog acoustic signal AS_A.
In this embodiment, the sub-amplifier circuit 213 receives power from a battery (not shown) (see reference numeral 215 in FIG. 16B).

As shown in FIG. 16A, the acoustic recording device 221 includes an input terminal portion 2211 for an analog acoustic signal AS_A, and includes a main amplification circuit 2212, an A / D conversion circuit 2213, a processing device 2214, and an external memory slot 2215. doing.
The input terminal portion 2211, the main amplification circuit 2212, and the A / D conversion circuit 2213 correspond to the input terminal portion 121, the main amplification circuit 122, and the A / D conversion circuit 123 in FIGS.
Note that the processing circuit 2214 operates according to a control program in a ROM (not shown).

  The analog acoustic signal AS_A is input to the main amplifier circuit 2212 through the input terminal portion 2211. The main amplifier circuit 2212 amplifies the audible frequency component of the analog acoustic signal AS_A and outputs it as an analog acoustic signal AS_AA having frequency characteristics for attenuating the non-audible frequency component.

The analog acoustic signal AS_AA is converted into a digital acoustic signal DS by the A / D conversion circuit 2213.
The digital acoustic signal DS is stored in the external memory EX_MEM inserted in the external memory slot 2215.

As shown in FIG. 16B, the output terminal portion 212 of the sound sensor 21 is a plug formed at the tip end of the cable 214 drawn from the piezoelectric element 2111 (see FIG. 15). The plug accommodates a sub-amplifier circuit 213 and a battery 215. When a capacitive sound sensor is used as in the present embodiment, a high input impedance sub-amplifier circuit is usually used.
In FIG. 16B, the plug (output terminal portion 212) terminal includes a ground (earth) terminal GND_T and microphone terminals MIC_RT and MIC_LT from the tip.

  The acoustic signal line (SGN) drawn from the piezoelectric element 2111 is connected to the input terminal of the sub-amplifier circuit 213. The output terminal of the sub amplifier circuit 213 is connected to the microphone terminal MIC_LT via MIC_LLINE. Note that the ground terminal (GND) of the sub-amplifier circuit 213 is connected to the ground line (GND_LINE). The sub-amplifier circuit 213 is supplied with power from the battery 215 via the power supply line BS_LINE.

As shown in FIG. 17, the computer 222 includes a processing circuit 2221, a memory 2222 (RAM, ROM), and a display circuit 2223, and includes an external memory slot 2224 and a display 2225.
The external memory EX_MEM can be inserted into the external memory slot 2224. The processing circuit 2221 takes in the digital acoustic signal DS stored in the external memory EX_MEM into the memory 2222 (RAM), and performs the processing described in FIGS.
Note that the digital acoustic signal DS stored in the RAM of the memory 2222 of the acoustic recording device 221 or the external memory EX_MEM can be sent to the computer 222 by wire or wirelessly.

The processing circuit 2221 is a circuit including a CPU in this embodiment. The processing circuit 2221 can include other processors in addition to the CPU. When signal processing is performed by an external circuit including a DSP (for example, provided by an extension circuit board), the processing circuit 2221 includes the external circuit.
The display circuit 2223 can display the digital acoustic signal DS and the respiratory motion / heart sound signal (RM / HB_S) on the display 2225.

  In the sleep apnea diagnosis support apparatus 2, the processing circuit 2221 can generate diagnosis support information about sleep apnea and display the diagnosis support information on the display 2225.

Moreover, in the sleep apnea diagnosis support apparatus 2, a person (such as a doctor) can detect sleep apnea based on the waveform of the respiratory motion / heart sound signal (RM / HB_S).
When sleep apnea is detected, a person (such as a doctor) can detect whether sleep apnea is central apnea or obstructive apnea from a component (RMS) related to respiratory motion.

In the above embodiment, the case where the processing circuit 124 of FIGS. 1 to 6 or the processing circuit 2221 of FIGS. 15 to 16 performs the extraction process of the respiratory motion / heart sound signal (RM / HB_S) for the digital acoustic signal DS will be described. did.
The processing circuit 124 of FIGS. 1-6 and the processing circuit 2221 of FIGS. 15-16, from the digital acoustic signal DS, the waveform of the respiratory motion component (respiratory motion signal RMS), the component of the heart sound (heart sound signal HBS). These waveforms may be extracted respectively.
The heart sound signal HBS can be used to determine whether or not a heart sound signal is detected in FIG. 9 (S160) and to determine whether or not a heart sound signal is detected in FIGS. 10 and 12 (S260).

1, 2 Sleep apnea diagnosis support device 11, 21 Sound sensor 12, 22 Main unit 222 Computer 111, 211 Sensing unit 112, 212 Output terminal unit 113, 213 Sub-amplifier circuit 114, 214 Cable 121, 2112 Input terminal unit 122 , 2212 Main amplifier circuit 123, 2213 A / D converter circuit 124, 2314 Processing circuit 125, 2315 Memory 126, 2223 Display circuit 127, 2225 Display 215 Battery 2221 Processing device (CPU)
2224 External memory slot 1111, 2111 Piezoelectric element 1112, 2112 Plate a1, a2, b1, b2 Terminal AS, AS_A, AS_AA Analog acoustic signal BS_LINE Power line DS Digital acoustic signal EX_MEM External memory GND, GND_T Ground terminal GND_LINE Ground line HBS Heart sound MIC_T Microphone terminal MIC_LT Microphone terminal (LEFT)
MIC_LT Microphone terminal (RIGHT)
RM / HB_S Respiratory motion / heart sound signal RMS Respiratory motion signal SGN Acoustic signal line SP_LT Speaker terminal (LEFT)
SP_RT Speaker terminal (RIGHT)
TR Bipolar transistor V_DRV Drive voltage

Claims (16)

A sound sensor in which a sensing unit is disposed directly or indirectly in close contact with a subject's body, and a main amplifier circuit that amplifies an analog acoustic signal from the sound sensor, an A / D conversion circuit, and an arithmetic processing unit A sleep apnea diagnosis support device equipped with a main unit:
The sound sensor is
The sensing unit that detects sound and outputs an analog sound signal;
and,
A sub-amplifier circuit for amplifying the analog acoustic signal from the sensing unit;
Comprising:
The combined gain characteristic of the gain characteristic of the sub-amplifier circuit and the gain characteristic of the main amplifier circuit is
Exhibit characteristics with a gain peak between 0.05 Hz and 3 Hz, which is greater than the gain of 20 Hz-20 kHz;
In the main unit,
The A / D converter circuit converts the analog sound signal amplified by the main amplifier circuit into a digital sound signal,
The arithmetic processing unit includes:
A component related to respiratory motion is extracted from the digital acoustic signal as a respiratory motion signal, and diagnostic support information about sleep apnea is generated based on the respiratory motion signal;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 1:
The arithmetic processing unit further extracts a component relating to a heart sound as a heart sound signal from the digital sound signal, and detects the presence or absence of respiratory effort,
Generating diagnostic support information on whether the sleep apnea is central apnea or obstructive apnea based on the respiratory motion signal, the heart sound signal, and the detection result of the presence or absence of the respiratory effort;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 1:
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion signal as diagnosis support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 1:
The main unit further comprises a display;
On the display,
Display the number of times the apnea duration exceeds the specified duration as diagnostic support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 2:
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion signal and the waveform of the heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 2:
The main unit further comprises a display;
On the display,
Display the number of times the apnea time length exceeded the predetermined time length when respiratory effort is detected as diagnostic support information about obstructive apnea,
Display the number of times the apnea duration exceeds a predetermined duration when heart sounds are detected and respiratory effort is not detected as diagnostic support information for central apnea;
Sleep apnea diagnosis support device. The sleep apnea diagnosis support apparatus according to claim 1, wherein the sub-amplifier circuit is supplied with power from the main unit.
The sub-amplifier circuit includes an impedance circuit provided between input terminals and an amplifier provided in the next stage of the impedance circuit;
The impedance circuit is low impedance when the frequency of the input signal is high and high impedance when the frequency of the input signal is low;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to any one of claims 1 to 7:
The main unit is
An acoustic recording apparatus having the main amplification circuit and the A / D conversion circuit;
and,
A computer having the arithmetic processing unit;
A sleep apnea diagnosis support device comprising: A sound sensor in which a sensing unit is disposed directly or indirectly in close contact with a subject's body, and a main amplifier circuit that amplifies an analog acoustic signal from the sound sensor, an A / D conversion circuit, and an arithmetic processing unit A sleep apnea diagnosis support device equipped with a main unit:
The sound sensor is
The sensing unit that detects sound and outputs an analog sound signal;
and,
A sub-amplifier circuit for amplifying the analog acoustic signal from the sensing unit;
Comprising:
The high-frequency cutoff frequency of the sub-amplifier circuit is smaller than the low-frequency cutoff frequency of the main amplifier circuit,
And,
A combined gain characteristic of the gain characteristic of the sub-amplifier circuit and the gain characteristic of the main amplifier circuit indicates a characteristic having a gain peak larger than a gain of 20 Hz-20 kHz between 0.05 Hz and 3 Hz;
In the main unit,
The A / D converter circuit converts the analog sound signal amplified by the main amplifier circuit into a digital sound signal,
The arithmetic processing unit includes:
A component relating to respiratory motion and heart sound is extracted from the digital acoustic signal as a respiratory motion / heart sound signal, and diagnostic support information about sleep apnea is generated based on the respiratory motion / heart sound signal;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 9:
The arithmetic processing unit detects the presence or absence of respiratory effort,
Generating diagnostic support information as to whether the sleep apnea is central apnea or obstructive apnea based on the respiratory motion / heart sound signal and the detection result of the presence or absence of the respiratory effort;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 9:
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion / heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 9:
The main unit further comprises a display;
On the display,
Display the number of times the apnea duration exceeds the specified duration as diagnostic support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 10:
The main unit further comprises a display;
On the display,
Displaying the waveform of the respiratory motion / heart sound signal as diagnosis support information;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to claim 10:
The main unit further comprises a display;
On the display,
Display the number of times the apnea time length exceeded the predetermined time length when respiratory effort is detected as diagnostic support information about obstructive apnea,
Display the number of times the apnea duration exceeds a predetermined duration when heart sounds are detected and respiratory effort is not detected as diagnostic support information for central apnea;
Sleep apnea diagnosis support device. The sleep apnea diagnosis support apparatus according to claim 9, wherein the sub-amplifier circuit is supplied with power from the main device.
The sub-amplifier circuit includes an impedance circuit provided between input terminals and an amplifier provided in the next stage of the impedance circuit;
The impedance circuit is low impedance when the frequency of the input signal is high and high impedance when the frequency of the input signal is low;
Sleep apnea diagnosis support device. In the sleep apnea diagnosis support apparatus according to any one of claims 9 to 15:
The main unit is
An acoustic recording apparatus having the main amplifier circuit and the A / D conversion circuit;
and,
A computer having the arithmetic processing unit;
A sleep apnea diagnosis support device comprising: