JP2012183214A - Blood vessel simulation sensor and pulse wave measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a signal similar to pure pulse wave by removing motion noise components including the body motion influence applied to the subcutaneous tissue in measuring pulse wave.SOLUTION: The pulse wave measuring apparatus includes a pseudo lymph vessel in which a pseudo lymph fluid simulating the subcutaneous tissue is enclosed on the outer side of a pseudo blood vessel for measuring body motion components of blood. A light emitting element and a light receiving element are attached to hold the pseudo lymph vessel between the elements. The light emitted from the light emitting element and passing through the pseudo lymph vessel and pseudo blood vessel is received by the light receiving element. A signal thus receiving the light is included in a pulse wave measuring signal, and has a high interrelation with a motion component representing the body motion influence applied to the blood vessel and the subcutaneous tissue. By removing the motion component represented by the signal, the motion components including the body motion influence applied to the subcutaneous tissue are removed from the pulse wave measuring signal, so that a pure pulse wave component is obtained.

Description

  The present invention relates to a blood vessel simulation sensor and a pulse wave measurement device.

  A pulse wave meter that measures a pulse wave and calculates the pulse rate from the waveform is often used as a device for obtaining human biological information. Some have a shape imitating a wristwatch and are worn on the subject's hand. Such a watch-type pulse meter is suitable for monitoring a subject's pulse wave over a long period of time. However, in a wristwatch-type pulsometer, when a subject wears a pulsometer and performs body movement such as walking, noise components generated by the body movement are mixed in the measurement result, and the S / N decreases. There is a case. Removing this body motion noise component from the measurement result and obtaining a pure pulse wave is an important technical problem in pulse wave measurement.

JP 2004-358271 A

In general, it is known that blood in veins is more susceptible to body movement than blood in arteries, and the waveform obtained by measuring venous blood is close to the body movement component.
The result of measuring venous blood by a non-invasive method is a measurement result through a subcutaneous tissue, from which it is difficult to obtain a pure movement component of venous blood. For this reason, a method has been considered in which a simulated vein is provided outside the body, and the effect of venous blood on body movements is directly measured.
In patent document 1, while measuring a photoelectric pulse wave, the tube tube which enclosed the simulated blood which has the viscosity equivalent to a venous blood is provided. Then, the change in the flow of the simulated blood caused by the body movement is measured as a photoelectric signal. The signal thus obtained is regarded as a body motion component of blood in the pulse wave signal separately measured simultaneously, and a pure pulse wave signal is obtained by subtracting this component from the pulse wave measurement signal.
However, the subcutaneous tissue contains a liquid such as lymph, and the body movement affects not only the blood in the blood vessel but also the flow of the liquid in the subcutaneous tissue. The conventional blood vessel simulation sensor does not take into account the influence of body movement on the subcutaneous tissue. For this reason, the result of removing the movement component of the simulated venous blood still includes body movement noise received by the liquid in the subcutaneous tissue. That is, the result of removing the motion component is not yet a pure pulse wave signal.
In this method, the body motion noise component is dominant in the pulse wave signal measured during body motion, and it is difficult to obtain the pulse wave component when the pulsation component is relatively weak. It is difficult to achieve the purpose of monitoring the onset of arrhythmia and the like (necessary to accurately measure the time interval of each pulse).

  The present invention has been made in view of such a problem, and removes motion noise components including the influence of body movement received by a subcutaneous tissue in pulse wave measurement, and obtains a signal closer to a pure pulse wave. Is at least one solution.

  In order to solve the above problems, the present invention can be realized as the following forms or application examples.

[Application Example 1]
The blood vessel simulation sensor according to this application example is a blood vessel simulation sensor that is mounted on a human body and simulates the behavior of blood. The blood vessel simulation sensor has a first casing filled with pseudo blood inside and a first casing outside. The second casing is filled with a pseudo lymph liquid, and the light emitting element and the light receiving element are provided with the first casing and the second casing interposed therebetween.

  According to this application example, since the first casing is filled with the pseudo blood inside and the second casing is outside the pseudo casing and filled with the pseudo lymph liquid, the casing is sandwiched during body movement. The signals measured by the light emitting element and the light receiving element provided in the above include a body motion component in which simulated blood is generated by body motion and a body motion component in which simulated lymph is generated. The body motion component measured for these simulated biological fluids is highly correlated with the body motion component in the pulse signal measured separately at the same time. When removing body motion noise from the pulse wave measurement signal, the body motion component obtained from these simulated biological fluids is used to remove the motion component including the body motion effect received by the subcutaneous tissue. A signal closer to the pulse wave can be obtained.

  Application Example 2 The second casing described in the application example described above is characterized in that it has a cylindrical shape with both ends closed or a mesh shape.

  According to this application example, the second casing has a cylindrical shape in which both ends are closed or a mesh shape, so that pseudo lymph fluid can flow irregularly in multiple directions during body movement. This shape is suitable for simulating that the lymph fluid in the lymph vessels extending and distributed in multiple directions in the human subcutaneous tissue flows into the lymph vessels due to body movement. The simulated lymph fluid filled therein can simulate the effect of body movement on the subcutaneous tissue.

  Application Example 3 The second casing described in the application example is formed of a resin having transparency.

  According to this application example, since the second casing is formed of a resin having transparency, attenuation by the second casing with respect to light emitted from the light emitting element is minimized. As a result, it is possible to receive the maximum body movement effect received by the subcutaneous tissue by the light receiving element.

  Application Example 4 A pulse wave meter that is mounted on a human body and measures a pulse wave according to this application example has a pulse wave sensor and outputs a pulse wave detection signal, and any of the above application examples And a body motion removal unit that removes the pseudo body motion component output from the blood vessel simulation sensor from the pulse wave detection signal.

  According to this application example, a body motion component is measured by the blood vessel simulation sensor and output as a body motion signal, and at the same time, a pulse wave is also measured by the pulse wave sensor and output as a photoelectric pulse wave signal. The body motion removal unit removes the output signal of the blood vessel simulation sensor from the output signal of the pulse wave sensor by a signal processing method. This makes it possible to remove body motion components including the body motion effect received by the subcutaneous tissue.

  Application Example 5 The pulse wave sensor described in the application example is arranged in the vicinity of the blood vessel simulation sensor.

  According to this application example, since the pulse wave sensor is arranged in the vicinity of the blood vessel simulation sensor, the influence caused by body movement is not only caused by the blood vessel to be measured by the pulse wave sensor, but also by the blood vessel simulation sensor. Will receive. For this reason, the body motion component in the pulse wave measured by the pulse wave sensor is highly correlated with the body motion signal obtained by the blood vessel simulation sensor. Therefore, by subtracting the body motion component indicated by the signal obtained from the blood vessel simulation sensor from the pulse wave signal, the motion component including the body motion effect received by the subcutaneous tissue can be removed.

It is a figure which shows the external appearance of one Embodiment of the pulse-wave measuring apparatus of this invention. It is a schematic diagram showing a section of a pulse wave measuring device. It is a perspective view of the blood vessel simulation sensor built in a pulse wave measuring device. It is a block diagram which shows the functional structural example of a pulse wave measuring device.

Prior to describing the embodiment, the operation principle of the present invention will be described.
A waveform showing a change in volume of a blood vessel caused by blood flowing into a blood vessel in a certain part of the body is called a pulse wave. As a sensor for detecting this pulse wave, a method has been conventionally used in which a measurement site is irradiated with detection light from a light emitting element and the reflected light or transmitted light is detected by a light receiving element. In this method, the amount of light emitted from the light emitting element is made constant, and the change in the amount of light received on the light receiving element side is detected as a change in blood vessel volume. In general, an LED (Light Emitting Diode) is used as the light emitting element, and a PD (Photo Diode) is used as the light receiving element.

  In this method, the output of the pulse wave sensor at rest without body movement is a pulse wave component formed by blood that is periodically pushed from the heart to the aorta by contraction of the myocardium and flows into arterioles and capillaries. However, when there is a body motion, various body motion components are included in addition to the pulse wave component. It is known that this body movement component is caused by changes in the living body caused by various movements (exercise, daily movement) of the person who is the subject. As a method for non-invasively detecting the body movement component inside the living body, as in the conventional example, while measuring the pulse wave and providing a tube tube filled with simulated blood having the same viscosity as blood, The change in the flow of the simulated blood is measured in the same way as the pulse wave measurement, and the measurement result for this simulated blood is subtracted from the pulse wave mixed with body motion components using a signal processing method. There was a method for acquiring a pulse wave signal.

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)

  FIG. 1 is a diagram showing an appearance of a pulse wave measuring apparatus 1 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a cross section of the pulse wave measuring device 1. As shown in FIG. 1, the pulse wave measuring device 1 has a shape imitating a wristwatch. On the surface, a display unit 12 having a rectangular display surface is provided. The display unit 12 displays a pulse waveform that is a measurement result by the pulse wave measuring device 1, or a pulse interval and a pulse rate that are calculated based on the pulse waveform. A button switch 11 is provided on the outer periphery of the casing of the pulse wave measuring device 1. The button switch 11 is used to input various instructions such as pulse wave measurement start and measurement end, and measurement result reset. The display unit 12 and the button switch 11 are connected to an electronic circuit inside the apparatus shown in FIG.

  As shown in the schematic cross-sectional view of the apparatus in FIG. 2, the surface 24 where the pulse wave measuring device 1 and the arm of the attachment site are in contact is provided with an LED 23 that irradiates the arm with measurement light and a PD 22 that receives the reflected light A pulse wave sensor 20 is attached. The LED 23 of the pulse wave sensor 20 irradiates light with a wavelength that is easily absorbed by blood (for example, blue) toward the measurement site with an intensity corresponding to the supplied current. The irradiated light passes through the epidermis at the measurement site and reaches the capillaries of the dermis behind it. Part of the light that reaches the blood vessel is absorbed by the blood flowing in the blood vessel. Further, of the light that has reached the blood vessel, a part of the light that has not been absorbed by the blood in the blood vessel passes through the measurement site, and the rest passes through the measurement in the subcutaneous tissue and then reaches the PD 22 as reflected light. The PD 22 is a photodiode matched to the wavelength of the LED 23, and a current having a magnitude corresponding to the intensity of the reflected light flows. Here, the blood vessel at the measurement site repeats expansion and contraction in the same cycle as the heartbeat. Then, the amount of light absorption increases and decreases in the same cycle as the blood vessel expansion and contraction, and the intensity of the reflected light also changes accordingly. For this reason, the current flowing through the PD 22 has a component indicating a change in the volume of the blood vessel at the measurement site. The blood vessel simulation sensor 21 is attached to the upper part of the pulse wave sensor 20 inside the apparatus.

  FIG. 3 is a perspective view of the blood vessel simulation sensor 21 built in the pulse wave measuring device 1. The blood vessel simulation sensor 21 has a tubular tube tube whose both ends that become the pseudo blood vessel 30 are closed. In the pseudo blood vessel 30, pseudo blood 34, which is a liquid having a viscosity and color equivalent to blood, is enclosed. The pseudo blood vessel 30 has a mesh-like pseudo lymphatic vessel 31 formed of a transparent resin and closed. A pseudo lymph fluid (not shown) is sealed inside the pseudo lymph vessel 31. The simulated lymph fluid is a fluid having the same viscosity and color as the lymph fluid. An LED 32 serving as a light emitting element and a PD 33 serving as a light receiving element are attached to the outside of the pseudo lymph duct 31 so as to sandwich the pseudo lymph duct 31.

  The LED 32 of the blood vessel simulation sensor 21 irradiates light having the same wavelength as the PD 22 of the pulse wave sensor 20 toward the pseudo lymphatic vessel 31 and the pseudo blood vessel 30 in the back thereof with a constant light emission intensity. A part of the irradiated light is absorbed by the pseudo blood in the pseudo blood vessel 30, but a part of the light passes through the pseudo lymph vessel 31 and the pseudo blood vessel 30 and reaches the PD 33. The PD 33 is a photodiode matched to the wavelength of the LED 32, and a current having a magnitude corresponding to the intensity of transmitted light flows. At rest, the pseudo blood 34 in the pseudo blood vessel 30 and the pseudo lymph fluid in the pseudo lymph vessel 31 have no wave and the thickness of the pseudo blood and the pseudo lymph fluid in the optical path of the transmitted light does not change. The intensity of the received light is constant. On the other hand, when the body is moving, the pseudo blood 34 flows into the pseudo blood vessel 30 and the pseudo lymph fluid flows into the pseudo lymph vessel 31 in response to the movement. Since these waves change the thickness of the pseudo blood 34 and the pseudo lymph fluid on the optical path of the transmitted light, the intensity of the light received by the PD 33 changes. When the peak of the wave is in the optical path of the transmitted light, the irradiation light absorbed by the pseudo blood vessel or the pseudo lymph fluid increases, and the intensity of the transmitted light reaching the PD 33 decreases. On the other hand, when the wave valley is in the optical path of the transmitted light, the irradiation light absorbed by the pseudo blood vessel or the pseudo lymph is reduced, and the intensity of the transmitted light reaching the PD 33 is increased. The change in the current flowing through the PD 33 that occurs in response to the change in the intensity of the transmitted light represents the movement of the simulated blood 34 and the simulated lymph fluid that are caused by the movement. What shows this movement is considered to be very close to the body motion component of the blood vessel and subcutaneous tissue contained in the pulse wave measured by the pulse wave sensor 20 during body motion and to have a high correlation.

  FIG. 4 is a block diagram showing a functional configuration example of the present embodiment. As shown in FIG. 4, the pulse wave measuring device 1 includes a body motion signal amplification circuit 40 that amplifies an output signal from the blood vessel simulation sensor 21 and a pulse wave signal amplification circuit 41 that amplifies the output signal from the pulse wave sensor. An A / D conversion circuit 42, an MPU 43, a RAM 44, a ROM 45, and a display unit 12.

The body motion signal amplification circuit 40 converts the current signal output from the blood vessel simulation sensor 21 into a voltage signal, further amplifies the signal with a predetermined amplification factor, and outputs the amplified body motion signal MA to the A / D conversion circuit 42. .
The pulse wave signal amplifier circuit 41 converts the pulse wave current signal output from the pulse wave sensor into a voltage signal, further amplifies it with a predetermined amplification factor, and outputs it as an amplified pulse wave signal PA to the A / D converter circuit 42. To do.
The A / D conversion circuit 42 individually performs analog / digital conversion on the input amplified body motion signal MA and amplified pulse wave signal PA, and outputs them to the MPU 43 as a body motion detection signal MS and a pulse wave detection signal PS.
The MPU 43 stores the input body motion detection signal MS and pulse wave detection signal PS in the RAM 44, and first performs body motion component removal processing on the pulse wave detection signal PS based on the program stored in the ROM 45. Then, a pure pulse wave signal P is obtained.
Body motion component removal processing uses a known adaptive noise removal algorithm such as an nLMS (normalized least mean square) algorithm using the pulse wave detection signal PS as a learning signal and the body motion detection signal MS as an input signal. The body motion component in the signal PS is subtracted. The result is a pure pulse wave signal P with the body motion component removed.

  Next, the pulse wave attributes (pulse interval length, pulse rate, etc.) corresponding to the display request input by the measurement subject are calculated and output to the display unit 12 for display. If the display request input by the person being measured is a pulse interval, the program detects the pulse wave peak in time series for the pulse wave signal P, and calculates the time difference between the peak and the previous peak. To display. If pulse rate display is required, the number of pulse wave peaks within a predetermined time (for example, from one minute before to the present) is counted and output and displayed on the display unit 12 or the pulse wave signal P On the other hand, the FFT calculation is performed, and the frequency having the strongest power among the frequency components of the pulse wave is regarded as the pulse frequency, which is converted into the pulse rate within a predetermined time and displayed on the display unit 12.

(Modification of embodiment)
Although the embodiment of the present invention has been described above, it is needless to say that the following modifications may be added to this embodiment.
(1) In the above embodiment, the emission color of the pulse wave sensor 20 and the blood vessel simulation sensor 21 is blue, but the emission color may be green or other colors.
(2) In the above-described embodiment, the pseudo lymphatic vessel is a mesh, but the pseudo lymphatic vessel may be a closed cylinder covering the outside of the pseudo blood vessel.
(3) In the above embodiment, the blood vessel simulation sensor is attached to the upper part of the pulse wave sensor, but the blood vessel simulation sensor may be attached to a position near the pulse wave sensor other than the upper part.
(4) In the above-described embodiment, the pulse wave measuring device 1 has a built-in function for processing signals output from the pulse wave sensor and the blood vessel simulation sensor. The function may be provided in an external device such as a mobile phone, and the pulse wave measuring device 1 may be configured by only a pulse wave sensor, a blood vessel simulation sensor, and a wireless communication unit that communicates with the external device. In this case, since functions such as signal processing, pulse wave attribute calculation, and display can use the CPU and display function of the external device, measurement costs can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Pulse wave measuring device, 11 ... Button switch, 12 ... Display part, 13 ... Wristband, 20 ... Pulse wave sensor, 21 ... Blood vessel simulation sensor, 22 ... Light receiving element of pulse wave sensor, 23 ... Light emission of pulse wave sensor Element 30 ... Pseudo blood vessel 31 ... Pseudo lymphatic vessel 32 ... Light emitting element of blood vessel simulation sensor 33 ... Light receiving element of blood vessel simulation sensor 40 ... Body motion signal amplification circuit 41 ... Pulse wave signal amplification circuit 42 ... A / D conversion circuit, 43 ... MPU, 44 ... RAM, 45 ... ROM.

Claims (5)

A blood vessel simulation sensor that is attached to the human body and simulates the behavior of venous blood,
A first casing filled with pseudo blood inside;
A second casing outside the first casing and filled with a pseudo-lymph liquid;
A light emitting element and a light receiving element provided across the first casing and the second casing;
A blood vessel simulation sensor characterized by comprising: The blood vessel simulation sensor according to claim 1, wherein
The blood vessel simulation sensor, wherein the second casing has a cylindrical shape in which both ends are closed or a mesh shape. The blood vessel simulation sensor according to claim 1, wherein
The blood vessel simulation sensor, wherein the second casing is formed of a resin having transparency. In the plethysmograph that is worn on the human body and measures the pulse wave
A pulse wave detector having a pulse wave sensor and outputting a pulse wave signal;
The blood vessel simulation sensor according to any one of claims 1 to 3,
A body motion removal unit that removes an output signal from the blood vessel simulation sensor from the pulse wave detection signal;
A pulse wave meter characterized by comprising: The pulse wave meter according to claim 4, wherein
The pulse wave meter, wherein the blood vessel simulation sensor is disposed in the vicinity of the pulse wave sensor.

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