JP2004041482A - Pulse wave detector and biopotential detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse wave detector and a biopotential detector which can lower noises to be overlapped onto detection signals. <P>SOLUTION: A pulse wave detector 10 which noninvasively detects the pulse waves on a peripheral basis has a pulse wave detection probe 61 to be brought into contact with pulse wave detecting sites of subjects for detecting the pulse waves of the subjects, at least one biomedical ground electrode 63 to be brought into contact with the sites adjacent to the pulse wave detecting sites of the subjects for taking biomedical grounding and a mounting/holding member 62 which is arranged covering the pulse wave detection probe 61 and the biomedical ground electrode 63 to get the pulse wave detection probe 61 and the biomedical ground electrode 63 mounted on the subjects. The mounting/holding member 62 is made up of an electroconductive member and connected to the biomedical ground electrode 63. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pulse wave detection device and a biopotential detection device that can reduce noise of a detection signal.
[0002]
BACKGROUND ART AND PROBLEMS TO BE SOLVED BY THE INVENTION
2. Description of the Related Art A pulse wave detection device that is worn on a subject and invasively detects a peripheral pulse wave of the subject has been developed. The subject can know his or her own health condition from the pulse wave detected by the portable pulse wave detection device.
[0003]
In order to detect a pulse wave invasively, it is known to detect a pulse wave optically or to detect a pulse wave based on a pulse pressure.
[0004]
The pulse waveform detected as described above does not become a pure pulse waveform generated by blood flowing from the aorta to peripheral blood vessels based on the expansion and contraction of the heart. This is because noise is superimposed on the detected pulse waveform.
[0005]
Bioelectric potential detecting devices such as cardiac potential and myoelectric potential also have a problem of noise.
[0006]
As a result of studying this noise, the present inventor has found that there is room for improvement in how to ground the living body.
[0007]
An object of the present invention is to provide a pulse wave detection device and a biopotential detection device that can reduce noise superimposed on a detection signal.
[0008]
[Means for Solving the Problems]
A pulse wave detection device according to one embodiment of the present invention is a pulse wave detection device that non-invasively detects a peripheral pulse wave, wherein the pulse wave detection device detects a subject's pulse wave by contacting the subject's pulse wave detection site. A probe, at least one living body earth electrode that is in contact with a part of the subject adjacent to the pulse wave detection part and takes a living body earth, and is disposed to cover the pulse wave detection probe and the living body earth electrode, and the pulse wave detection is performed. A mounting member for mounting the probe and the living body earth electrode to a subject. The mounting and holding member is formed of a conductive member and is connected to the living body earth electrode.
[0009]
According to this configuration, it is considered that the S / N is improved by the following operation. First, the pulse wave detection probe and the biological earth electrode are covered with a conductive attachment holding member for attaching them to a subject. Moreover, the mounting and holding member is connected to the living body earth electrode. This reduces the influence of disturbance noise such as electromagnetic wave noise on the pulse wave detection probe. Next, a living body ground electrode is provided which is in contact with a part adjacent to the pulse wave detection part of the subject and which is always at a fixed distance from the pulse wave detection part. Here, the pulse wave is detected using the ground potential as a reference potential. For this reason, by setting the bio-ground potential at a position at a fixed distance near the detection site, the distance from the detection site is different from the conventional one, or the distance from the detection site is different each time the setting is made. The ground potential does not become unstable. Therefore, it is possible to prevent the adverse effects caused by the difference in the ground potential.
[0010]
The pulse wave detection probe can optically detect a pulse wave, and can include a light emitting element and a light receiving element. In this case, the living body earth electrode can be arranged on both sides of the light emitting element and the light receiving element. Alternatively, a living body earth electrode may be arranged so as to surround the light emitting element and the light receiving element.
[0011]
The pulse wave detection site can be set at a site corresponding to the radial artery of the finger. In this case, the mounting and holding member can be formed in a cylindrical finger sack shape to be inserted into the finger. The pulse wave detection site may be set at a site corresponding to the radial artery of the wrist. In this case, the mounting and holding member can be formed in the shape of a wristband that is wound and held around the wrist. The pulse wave detection site may be set at another peripheral site such as an ear, and the shape of the mounting and holding member may be set so as to match the detection site. It is to be noted that a housing containing a battery can be provided in a wristband as a mounting and holding member. At this time, the reference potential line of the battery can be connected to the housing, and the housing can be connected to the wristband. Thus, the housing for setting the reference potential of the battery can be connected to the living body earth electrode.
[0012]
The mounting and holding member can be formed of a conductive mesh. The detection site does not get stuffy even after a long wearing, and the electromagnetic shielding effect can be exhibited. If the mounting / holding member is provided with a light blocking function, ventilation can be provided by forming a ventilation hole, a mesh, or the like in a place other than the light emitting / receiving element.
[0013]
A biopotential detection device according to another aspect of the present invention includes a biopotential detection electrode disposed in contact with a detection site of a subject, a signal potential extraction cable connected to the biopotential detection electrode, and the signal potential extraction A shielded cable that is electrically insulated and arranged around the cable, electrically connected to an end of the shielded cable, arranged so as to be in non-contact with the detection site, and And a shielding tubular part for covering.
[0014]
In this biopotential detecting device, the shielding cylinder covering the biopotential detecting electrode can reduce disturbance noise from entering the biopotential detecting electrode. Further, since the signal extraction cable is covered with the shielded cable, disturbance noise can be prevented from entering the signal extraction cable, and the S / N is improved.
[0015]
The biopotential detection electrode may include an electrode portion arranged to be in contact with a detection site of a subject, and a terminal connected to the electrode portion. In this case, the signal potential extraction cable is detachably connected to the terminal of the biopotential detection electrode. In this way, by making the biopotential detection electrode and the signal potential extraction cable detachable, the work of setting the biopotential detection electrode at the detection site becomes easy.
[0016]
The biopotential detection device according to another aspect of the present invention may further include a bioearth electrode that contacts a site where the extracted biopotential signal is inactive. The shield cable is connected to the living body earth electrode, so that the adverse effect of disturbance noise can be reduced.
[0017]
The signal potential extraction cable can be a cable for extracting a cardiac potential or a myoelectric potential, and the biopotential detection device of the present invention can be applied to an electrocardiogram measurement device, an electromyogram measurement device, and the like.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0019]
<First embodiment>
The first embodiment of the present invention is a pulse wave detecting device.
[0020]
(External configuration of pulse wave detector)
The pulse wave detection device according to the present embodiment is a portable type that is worn on, for example, a wrist of a subject, and has an external configuration as shown in FIGS. 1A, 1B, and 1C. Can be. The pulse wave detecting device 10 is provided on a device main body 12 having a wristwatch-like structure, a cable 58 connected to the connector section 20 of the device main body 12 via a connector piece 57, and provided on a distal end side of the cable 58. And a pulse wave detection unit 60. A wristband 56 is attached to the device main body 12, and the device main body 12 is attached to the wrist of the subject by the wristband 56.
[0021]
The apparatus main body 12 includes a connector section 20, and a connector piece 57 serving as an end of a cable 58 is detachably attached to the connector section 20.
[0022]
FIG. 1C shows the connector portion 20 from which the connector piece 57 has been removed, and includes, for example, a connection pin 21 for connecting to a cable 58, an LED 22 for performing data transfer, and a phototransistor 23.
[0023]
On the front side of the apparatus main body 12, a display unit 54 composed of a liquid crystal panel is provided. The display unit 54 has a segment display area, a dot display area, and the like, and displays an index that changes depending on the amount of water in a blood vessel in a pulse wave, a hemodialysis time determined based on the index, and the like. The display unit 54 may use another display device instead of the liquid crystal panel.
[0024]
A CPU (central processing unit) for controlling various calculations and conversions, and a memory for storing a program for operating the CPU and the like (not shown) are provided inside the apparatus main body 12 (not shown). And a button switch 14 for performing input.
[0025]
On the other hand, the pulse wave detection unit 60 has a pulse wave detection probe 61 and two earth electrodes 63, 63 arranged on both sides thereof, as shown in FIG. The pulse wave detection unit 60 is mounted near the base of the subject's index finger while being shielded from light by a finger-suck-shaped sensor fixing band (mounting and holding member) 62. As described above, when the pulse wave detection unit 60 is mounted near the base of the finger, the cable 58 can be shortened, so that the cable 58 does not become an obstacle even when mounted. Further, since the change in blood flow due to air temperature is smaller in the vicinity of the base of the finger than in the fingertip, the influence of the air temperature or the like on the detected pulse waveform is relatively small.
[0026]
(Pulse wave detector)
The pulse wave detection probe 61 includes, for example, a light emitting element such as an LED 64 and a light receiving element such as a phototransistor 65 grounded by an earth electrode 63, as shown in FIG. 2, for example, and detects non-invasive pulse waves in the periphery without breaking the skin. It is configured so that it can be detected. The pulse wave detection probe 61 utilizes the fact that the pulse wave waveform is substantially the same as the fluctuation waveform of the blood flow (volume pulse wave waveform), and irradiates the capillary network with light and reflects the blood in the blood capillaries. A pulse wave (volume pulse wave) is detected by using an optical sensor formed to detect a change in light amount or a change in transmitted light amount.
[0027]
More specifically, the pulse wave detection probe 61 emits light from the LED 64 when the switch SW is turned on and a power supply voltage is applied. This irradiation light is received by the phototransistor 65 after being reflected by blood vessels and tissues of the subject. Therefore, a signal obtained by converting the photocurrent of the phototransistor 65 into a voltage is output as the signal PTG of the pulse wave detector 60.
[0028]
FIG. 3 is a plan view for explaining the arrangement of the pulse wave detection probe 61 and the two ground electrodes 63. The two earth electrodes 63, 63 approach the pulse wave detection probe 61 on both sides of the pulse wave detection probe 61 including the light emitting element 64 and the light receiving element 65, and are always at a fixed distance from the pulse wave detection probe 61. The living body earth electrodes 63, 63 are arranged only at positions apart from each other. Alternatively, a guard ring-shaped ground electrode may be provided so as to surround the light emitting element 64 and the light receiving element 65. Here, the pulse wave is detected using the ground potential as a reference potential. For this reason, by setting the bio-ground potential at a position at a fixed distance near the detection site, the distance from the detection site is different from the conventional one, or the distance from the detection site is different each time the setting is made. The potential of the ground electrode does not become unstable.
[0029]
Here, the sensor fixing band (mounting / holding member) 62 shown in FIGS. 1A and 1B is formed of a conductive member and is electrically connected to the two ground electrodes 63. As described above, since the sensor fixing band 62 covering the pulse wave detection probe 61 is connected to the ground electrodes 63, 63, it can be also used as a shield member for preventing disturbance noise from entering the pulse wave detection probe 61. it can.
[0030]
From the above configuration, the S / N of the pulse wave detected by the pulse wave detection probe 61 is improved.
[0031]
The emission wavelength of the LED 64 is selected near the absorption wavelength peak of hemoglobin in blood. Therefore, the light receiving level changes according to the blood flow. Accordingly, the pulse wave waveform is detected by detecting the light receiving level. For example, as the LED 64, an InGaN-based (indium-gallium-nitrogen-based) blue LED is suitable. The emission spectrum of this LED has an emission peak near 450 nm, and the emission wavelength range can be in a range from 350 nm to 600 nm.
[0032]
In the present embodiment, for example, a GaAsP-based (gallium-arsenic-phosphorus-based) phototransistor can be used as the phototransistor 65 corresponding to an LED having such light emission characteristics. In the light receiving wavelength region of the phototransistor 65, the main sensitivity region is in a range from 300 nm to 600 nm, and the sensitivity region can be 300 nm or less.
[0033]
When such a blue LED 64 and the phototransistor 65 are combined, a pulse wave can be detected in a wavelength region from 300 nm to 600 nm, which is an overlapping region thereof, and has the following advantages.
[0034]
First, among the light included in the external light, light having a wavelength region of 700 nm or less tends to hardly pass through the tissue of the finger, and therefore, the external light is applied to a part of the finger that is not covered with the sensor fixing band. However, only light in a wavelength region that does not affect detection does not reach the phototransistor 65 via the finger tissue, and reaches the phototransistor 65. On the other hand, light in a wavelength region longer than 300 nm is almost absorbed by the skin surface, so that even if the light reception wavelength region is set to 700 nm or less, the substantial light reception wavelength region is 300 nm to 700 nm. Therefore, the influence of external light can be suppressed without covering the finger with a large scale. Further, hemoglobin in blood has a large absorption coefficient for light having a wavelength of 300 nm to 700 nm, and is several times to about 100 times or more larger than the absorption coefficient for light having a wavelength of 880 nm. Therefore, as in this example, when light in a wavelength region (300 nm to 700 nm) having a large light absorption characteristic is used as detection light in accordance with the light absorption characteristic of hemoglobin, the detected value changes with high sensitivity according to a change in blood volume. Therefore, the SN ratio of the pulse waveform based on the change in blood volume can be increased.
[0035]
As described above, the pulse wave detection unit 60 recognizes a pulse wave, that is, a volume pulse wave, that changes in accordance with the blood flow as a change in the amount of red blood cells in the capillary network existing near the skin, and transmits the light irradiated to the skin. Since it can be detected as a change in the amount or the amount of reflection, it can be detected without adjusting the sensor to the position of a peripheral artery, for example, the radial artery or the lateral digital artery. Therefore, the pulse wave detecting unit 60 can stably detect a change in the amount of red blood cells in the capillaries near the skin as a pulse wave (volume pulse wave) in the peripheral artery.
[0036]
(Basic functional block configuration and low-frequency cutoff unit)
FIG. 4 is a functional block diagram of the pulse wave detection device 10 according to the embodiment. In FIG. 4, the pulse wave detection device 10 includes a low-frequency cutoff unit 70, an index extraction unit 80, and a notification unit 90 in addition to the above-described pulse wave detection unit 60. The low-frequency cutoff unit 80 is not always an essential component. It is preferable that the subject wearing the pulse wave detection device 10 determine the hemodialysis time when the subject is at rest or at least at rest. However, even in the resting state or the stationary state, the detected pulse wave maintains the low-frequency component caused by the fluctuation (excluding the movement of blood vessels) due to the activity of the subject's autonomic nervous system function or the stationary state. The low-frequency component caused by the fluctuation (body movement) of the subject's body during the operation is superimposed. These also become noises when detecting a pulse wave. By removing this noise in the low-frequency cutoff unit 70, the detection accuracy is further improved. Details of the low-frequency cutoff unit 70 will be described later.
[0037]
(Pulse wave waveform and index extraction unit)
FIG. 5 is a characteristic diagram showing a typical pulse wave waveform in an artery, for example, a radial artery. The pulse wave of one cycle shown in FIG. 5 includes a first rising point P0 of one cycle of the pulse wave, an ejection wave (Ejection Wave) P1, a retreating wave (Tidal Wave) P2, and a notch (Dicotic Notch) P3. , And a notch wave (Dicrotic Wave) P4.
[0038]
The index extracting unit 80 in FIG. 3 extracts an index based on a wave height or a wave height ratio of any of the indexes P0 to P4.
[0039]
The index extractor 70 may extract the index from the pulse wave shown in FIG. 5, but may also extract the index based on the second derivative waveform of the pulse wave. This is because the characteristics of the pulse wave shown in FIG. 5 are more apparent in the second derivative waveform. Therefore, as shown in FIG. 6, a primary differentiator 100 and a secondary differentiator 110 can be further provided in addition to the configuration of the basic functional blocks shown in FIG.
[0040]
FIG. 7A is a waveform diagram of an original waveform PTG of a pulse wave detected by the pulse wave detection unit 60 (or a pulse wave from which the low-frequency component has been removed by the low-frequency cutoff unit 70). FIG. 7B is a waveform diagram of a primary differential waveform FDPTG (velocity waveform) obtained by differentiating the original waveform PTG in the primary differentiating unit 100. FIG. 7C is a waveform diagram of a secondary differential waveform SDPTG (acceleration waveform) obtained by differentiating the primary differential waveform FDPTG by the secondary differentiating unit 110. As shown in FIG. 8, the second derivative waveform SDPTG has five more inflection points than the original waveform PTG, and their peak values are a to e, respectively.
[0041]
Here, the peak value a corresponds to the first rising point P0 of one cycle of the pulse wave, the peak value b corresponds to the ejection wave P1, the peak value c corresponds to the retreating wave P2, and the peak value d. Corresponds to the notch P3, and the peak value e corresponds to the notch wave P4. The index extracting unit 80 can extract any one of the peak values a to d or their peak ratio as an index.
[0042]
(Low frequency cutoff)
Next, the low-frequency cutoff unit 70 for further improving the detection accuracy will be described.
[0043]
The low-frequency cutoff unit 70 removes, from the pulse wave detected by the pulse-wave detection unit 60, low-frequency components caused by fluctuations (excluding movement of blood vessels) associated with the activity of the autonomic nervous system function. . This low frequency component is not a pure pulse frequency component generated by blood flowing from the aorta to peripheral blood vessels based on the expansion and contraction of the heart, but a lower frequency component than the frequency component in the pure pulse wave. is there. Since this low frequency component becomes noise superimposed on the pulse wave, the pulse wave can be stably detected by removing this noise.
[0044]
The low-frequency cutoff unit 70 can further remove low-frequency components caused by body motion of the subject at rest. Even if the subject is in a stationary state, the subject experiences fluctuations (body movement) due to maintaining the stationary state. This movement is not as if the limbs were consciously moved quickly, but rather a relatively slow movement. Therefore, a low frequency component is superimposed on the pulse wave due to the body motion, and this also becomes noise, so that it is removed.
[0045]
The low-frequency cutoff unit 70 sets the low-frequency cutoff frequency to 0.4 to 0 in order to remove fluctuations (excluding movement of blood vessels) associated with the activity of the autonomic nervous system function and low-frequency components caused by body motion. It is preferable to set a value in the range of 0.5 Hz. This is because the low frequency components below the low cutoff frequency do not include characteristics unique to the pulse wave, and these become noise. Fluctuations associated with the function of the autonomic nervous system include fluctuations associated with the activities of the sympathetic nervous system function and the accessory nervous system function. As the low-frequency components caused by the fluctuations associated with the activity of the sympathetic nervous system, for example, low-frequency components (for example, approximately 0.1 Hz) caused by fluctuations in the muscle pump function, which occur about once every 10 seconds, and the like. Can be. Examples of the low frequency components caused by the fluctuations associated with the activity of the parasympathetic nervous system include low frequency components (for example, about 0.15 Hz) caused by respiratory movement.
[0046]
The low-frequency cutoff unit 70 may be configured by a band-pass filter in which the high-frequency cutoff frequency is set to a value in a range of, for example, 16 to 30 Hz, in addition to the above-described low-frequency cutoff frequency. Thereby, in addition to the low frequency components, useless high frequency components exceeding the high frequency cutoff frequency can also be removed. It is sufficient that the high-frequency cutoff frequency is 30 Hz even with a margin, and the high-frequency cutoff frequency may be 20 Hz or 16 Hz.
[0047]
(Specific configuration example 1)
FIG. 9 is a block diagram more specifically showing the components from the pulse wave detector 60 to the second differentiator 110 in the functional blocks of FIG. 6, and FIG. 10 is a circuit diagram of the low-frequency cutoff unit. As illustrated in FIG. 9, the configuration example 1 includes a pulse wave detecting unit 60, an analog differentiating circuit 120, a quantizing unit 130, and a secondary differentiating unit 110. The analog differentiating circuit 120 has a function of a high-frequency cutoff unit in addition to the functions of the low-frequency cutoff unit 70 and the primary differentiating unit 100 shown in FIG. In other words, the analog differentiating circuit 120 has a band pass function. Instead, the analog differentiating circuit 120 may have a high-pass function. This is because in any case, a low frequency component lower than a cutoff frequency of 0.4 to 0.5 Hz can be cut off.
[0048]
As shown in FIG. 10, for example, the analog calculus circuit 120 can be configured to include elements C1 to C3 and R1 and R2 having a predetermined constant in a positive input terminal, a negative input terminal, and a negative feedback path of an operational amplifier 122. By setting the constants of these elements, the analog differentiating circuit 120 can have a band-pass function of passing a frequency component in a band such as 0.4 to 30 Hz, 0.4 to 20 Hz, or 0.4 to 16 Hz. . In any case, the low cutoff frequency is 0.4 to 0.5 Hz.
[0049]
The quantization unit 130 is an analog-to-digital converter that quantizes an analog signal from the analog differentiating circuit 120 and converts it into a digital signal as shown in FIG. Various known techniques can be used for the quantization technique. For example, when the light emitting element 64 is turned on and off by the switch SW shown in FIGS. 2 and 10, the output waveform is sampled by the switching, and therefore, sampling may be performed at the same sampling rate as the switching cycle. At this time, it is preferable that the quantization unit 130 amplify the output amplitude by an AGC (auto gain control) function so that the output amplitude becomes a certain level or more within the dynamic range. In the light transmission path between the light emitting element 64 and the light receiving element 65 of the pulse wave detection unit 60, there is a vascular bed in the skin of the subject. Therefore, it is necessary to appropriately amplify the output signal of the pulse wave detector 60 within the dynamic range.
[0050]
The secondary differentiator 110 shown in FIG. 9 is a quantizer differentiator, and obtains the amount of change (slope) between two adjacent discrete values on the time axis in FIG. Specifically, as shown in FIG. 12, first and second storage units 114 and 116 in which data are alternately stored by switch 112, and data from first and second storage units 114 and 116 And a digital subtractor 128 that calculates the difference between the two. The secondary differential waveform, which is the amount of change in the data shown in FIG. 11A, is as shown in FIG.
[0051]
(Experimental example)
For three subjects A to C, the original waveform PTG, the first derivative waveform FDPTG, and the second derivative waveform SDPTG were collected by changing the band pass characteristics of the analog differentiating circuit 120. As the band pass band, the high cutoff frequency was set to 16 Hz in common, but the low cutoff frequencies were 0.1 Hz (Comparative Example 1), 0.2 Hz (Comparative Example 2), 0.43 Hz (Example 1), 0.6 Hz (Comparative Example 3).
[0052]
The index -b / a was calculated and observed for each of the secondary differential waveforms SDPTG thus detected. The index -b / a changes depending on the water content in the blood vessel of each subject as described above, and has a positive correlation with the age of the subject as shown in FIG. As a result of the above measurement, it was confirmed that the index -b / a (= 1.12) of the secondary differential waveform SDPTG shown in Example 1 for the subject A is a value most suitable for the age of the subject A.
[0053]
The same measurement was performed for the subject B who is older than the subject A and the subject C which is younger than the subject A. Index-b / a of subject B measured in Example 1 was -b / a = 1.18, and index-b / a of subject C was similarly -0.89, and the age of subject C <the age of subject A <the subject B And the correlation of the index of the subject C (0.89) <the index of the subject A (1.12) <the index of the subject B (1.18) was consistent with the age order. As a result, it was found that the low-frequency cutoff frequency of the band-pass characteristic of Example 1 was optimally 0.43 Hz in comparison with Comparative Examples 1 to 3. As described above, the low-frequency cutoff frequency is optimally 0.4 to 0.5 Hz. As in Comparative Examples 1 to 3, even if the low-frequency cutoff frequency is too low (0.1 Hz, 0.2 Hz). (0.6 Hz) is not preferable.
[0054]
(Specific configuration 2)
FIG. 13 shows a modification in which a quantization unit 130 is provided between the pulse wave detection unit 60 and the low-frequency cutoff unit 70. The function of the quantization unit 130 is the same as in FIG. Similarly, the functions of the primary / secondary differentiating units 100 and 110 are the same as those of the secondary differentiating unit 110 shown in FIG. Note that one of the primary and secondary differentiating units 100 and 110 may be an analog differentiating circuit.
[0055]
As shown in FIG. 14, a low-frequency cutoff unit 70 shown in FIG. 13 includes a Fourier transform unit 72 for performing Fourier transform on quantized data, a digital filter 74 for removing a frequency spectrum lower than a low-frequency cutoff frequency, and the digital filter And an inverse Fourier transform unit 76 for performing an inverse Fourier transform on the output of By removing the frequency spectrum lower than the predetermined cutoff frequency from the frequency spectrum obtained by the Fourier transform by the digital filter, the low frequency components can be removed.
[0056]
In addition, analog signal processing is performed up to the low-frequency cutoff unit 70, a quantization unit 130 is provided between the low-frequency cutoff unit 70 and the first-order differentiating circuit 100, and the first and second-order differentiating units 100 and 110 are used as digital differentiating circuits. You may comprise.
[0057]
(Modification of pulse wave detection site)
In the above-described embodiment, the pulse wave detection site is set to the finger, but may be another site, such as the wrist or the radial artery of the ear.
[0058]
The pulse wave detection device 200 shown in FIG. 16 includes a device main body 210 having a wristwatch-like structure as in FIG. 1A, and a wristband 212 for attaching the device main body 210 to a wrist of a subject. Although the pulse wave detector 60 shown in FIG. 3 is not shown in FIG. 16, it is disposed inside the wristband 212. The wristband 212 is also used as a mounting and holding member for the pulse wave detector 60. For this reason, the wristband 212 is formed of a conductive member, and is connected to the two ground electrodes 63 in FIG. Thus, the wristband 212 in FIG. 16 can function similarly to the sensor fixing band 62 in FIG.
[0059]
The apparatus main body 210 has a built-in battery (not shown). The reference potential line of this battery can be connected to the housing of the device main body 210. In addition, this housing can be set to the same potential as the ground electrode by being electrically connected to the wristband 212.
[0060]
<Second embodiment>
Next, an embodiment in which the present invention is applied to a biopotential detection device will be described. An example of the biopotential detecting device is an electrocardiogram (electrocardiogram) measuring device. This electrocardiogram measuring apparatus requires electrodes for detecting a cardiac potential in order to graphically record a cardiac activity current with an electrocardiograph.
[0061]
FIG. 17 shows a signal potential detection unit 300 of the electrocardiogram measurement device according to the present embodiment. The signal potential detection unit 300 includes a biopotential detection electrode 310 disposed in contact with a detection part 302 of a subject, a signal potential extraction cable 320 connected to the biopotential detection electrode 310, and a signal potential extraction cable 320. A shielded cable 330 that is electrically insulated and arranged, and is electrically connected to an end of the shielded cable 330 and is arranged so as to be in non-contact with the detection site 302 and covers the biopotential detection electrode 310 And a cylindrical portion 340. The biopotential detection electrode 310 includes an electrode part 312 arranged in contact with the detection part 302 of the subject, and a terminal 314 connected to the electrode part 312. The signal potential extraction cable 320 is detachably connected to the terminal 312 of the biopotential detection electrode 310 and has, for example, a fitting portion 322 fitted therein.
[0062]
In order to install the biopotential detection electrode 310 at the detection site 302, the signal potential extraction cable 320, the shield cable 330, and the shield cylinder 340 are separated from the biopotential detection electrode 310. Therefore, the bioelectric potential detection electrode 310 alone can be installed at the detection site 302. As the biopotential detection electrode 310, an insulating tape 318 having an insulating adhesive layer 316 can be used to fix the electrode unit 312 to the detection site 302.
[0063]
According to this configuration, it is possible to reduce disturbance noise from entering the biopotential detection electrode 310 by the shield cylinder 340 covering the biopotential detection electrode 310. Further, since the signal extraction cable 320 is covered with the shielded cable 330, it is possible to prevent disturbance noise from entering the signal extraction cable 330, and the S / N is improved.
[0064]
Although the electrode shown in FIG. 17 is used in the monopole method using one utilization electrode, it can also be applied to an electrode used in the bipolar method using two utilization electrodes.
[0065]
In addition, the biopotential detection device is not limited to a device for measuring an electrocardiogram, and can be similarly applied to an electromyogram measurement device for measuring an electromyogram. This is because the electromyogram measuring device records the action potential generated when the muscle contracts and tensions, and the same surface electrode (skin electrode) as the electrocardiogram measuring device is used. The electromyogram measuring apparatus includes a monopole method and a bipolar method, and the present invention can be applied to both of them.
[0066]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, the sensor fixing band 62 shown in FIG. 1B or the wrist band 212 shown in FIG. 16 which is a mounting and holding member may secure air permeability so that a detection site does not become stuffy even when worn for a long time. For example, a mesh shape may be used. In the case where the pulse wave detector 60 is shielded from light by the mounting and holding member, the position of the ventilation portion may be devised so that external light does not enter the light emitting / receiving element.
[Brief description of the drawings]
FIGS. 1A, 1B and 1C are external views of a pulse wave detection device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of a circuit configuration of a pulse wave detector shown in FIG.
FIG. 3 is a plan view showing the pulse wave detection probe shown in FIG. 1 (B) and two living body earth electrodes.
FIG. 4 is a basic functional block diagram of the embodiment of the present invention.
FIG. 5 is a waveform diagram of one pulse of a pulse wave detected by a pulse wave detection unit.
FIG. 6 is a functional block diagram obtained by adding a primary / secondary differentiator to the basic functional block of FIG. 3;
7A is an original waveform of a detected pulse wave, FIG. 7B is a first derivative waveform of FIG. 7A, and FIG. 7C is a second derivative of FIG. 7A. It is a waveform diagram which shows a waveform respectively.
FIG. 8 is a schematic explanatory diagram for explaining the characteristics of the secondary differential waveform.
FIG. 9 is a block diagram showing a specific configuration 1 of a circuit after the low-frequency cutoff circuit.
FIG. 10 is a circuit diagram of the analog differentiating circuit in FIG. 9;
FIG. 11A is a waveform diagram showing a quantized waveform, and FIG. 11B is a waveform diagram showing a differential waveform thereof.
12 is a block diagram illustrating a configuration example of a secondary differentiator illustrated in FIG. 9;
FIG. 13 is a block diagram showing a specific configuration 2 of a circuit after the low-frequency cutoff circuit.
FIG. 14 is a circuit diagram of a low-frequency cutoff unit in FIG.
FIG. 15 is a characteristic diagram showing a correlation between the index (−b / a) and the age of the subject.
FIG. 16 is an external view of a pulse wave detection device using a pulse wave detection site as a wrist.
FIG. 17 is a schematic cross-sectional view of a signal detection unit of the biopotential detection device according to the second embodiment of the present invention.
[Explanation of symbols]
10 pulse wave detecting device 60 pulse wave detecting section 61 pulse wave detecting probe 62 band for fixing sensor (mounting and holding member)
63 Bio-earth electrode 64 Light-emitting element 65 Light-receiving element 70 Low-frequency cutoff section 72 Fourier transform section 74 Digital filter 76 Inverse Fourier transform section 80 Index extraction section 90 Notification section 100 Primary differentiation section 110 Secondary differentiation section 112 Switches 114, 116 First , Second storage section 118, digital subtracter 120, analog differentiating circuit (low-frequency cutoff section + primary differential circuit + high-frequency cutoff section)
122 Operational amplifier 130 Quantization unit 200 Pulse wave detection device 210 Device main body 212 Wrist band (attachment holding member)
300 Signal potential detecting section 302 Detection section 310 Signal potential detecting electrode 312 Electrode section 314 Terminal 316 Adhesive layer 318 Insulating tape 320 Signal extraction cable 322 Fitting section 330 Shield cable 340 Shield cylinder section PTG Original waveform FDPTG First derivative waveform SDPTG Second derivative Waveform

Claims (12)

In a pulse wave detection device that non-invasively detects a peripheral pulse wave,
A pulse wave detection probe that is in contact with the subject's pulse wave detection site and detects the subject's pulse wave,
At least one living body earth electrode that is in contact with a part adjacent to the pulse wave detection part of the subject and takes a living body earth,
An attachment holding member that is arranged to cover the pulse wave detection probe and the living body earth electrode, and attaches the pulse wave detection probe and the living body earth electrode to a subject.
Has,
A pulse wave detection device wherein the mounting and holding member is formed of a conductive member and is connected to the living body earth electrode. In claim 1,
The pulse wave detection probe includes a light emitting element and a light receiving element,
A pulse wave detecting device, wherein the living body earth electrode is disposed on both sides of the light emitting element and the light receiving element. In claim 1,
The pulse wave detection probe includes a light emitting element and a light receiving element,
The pulse wave detecting device, wherein the living body earth electrode is arranged so as to surround the light emitting element and the light receiving element. In any one of claims 1 to 3,
The pulse wave detection site is a site corresponding to the radial artery of the finger,
A pulse wave detecting device, wherein the mounting and holding member is formed in a cylindrical finger sack shape to be inserted into a finger. In any one of claims 1 to 3,
The pulse wave detection site is a site corresponding to the radial artery of the wrist,
The pulse wave detection device, wherein the mounting and holding member is formed in the shape of a wristband wound and held around a wrist. In claim 5,
A pulse wave detecting device in which a housing containing a battery is provided in the wristband, a reference potential line of the battery is connected to the housing, and the housing is connected to the wristband. In any one of claims 1 to 6,
The pulse wave detecting device, wherein the mounting and holding member is formed of a conductive mesh. A biopotential detection electrode arranged in contact with the detection site of the subject,
A signal potential extraction cable connected to the biopotential detection electrode,
A shielded cable arranged electrically insulated around the signal potential extraction cable,
Electrically connected to the end of the shielded cable, disposed so as to be in non-contact with the detection site, and a shielding tubular portion that covers the biopotential detection electrode,
A bioelectric potential detection device having the same. In claim 8,
The biopotential detection electrode includes an electrode portion disposed in contact with a detection site of a subject, and a terminal connected to the electrode portion,
The biopotential detection device, wherein the signal potential extraction cable is detachably connected to the terminal of the biopotential detection electrode. In claim 8 or 9,
The bioelectric potential signal to be taken out further has a bioearth electrode that is brought into contact with an inactive site,
The bioelectric potential detection device, wherein the shielded cable is connected to the bio-earth electrode. In any one of claims 8 to 10,
A biopotential detecting device, wherein the signal potential extracting cable extracts a cardiac potential. In any one of claims 8 to 10,
The bioelectric potential detection device, wherein the signal potential extraction cable is for extracting a myoelectric potential.

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