JP2008183414A - Apparatus for measuring circulation movement, method for circulation movement, blood pressure measurement method, and sensor for circulation movement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for measuring circulation movement which can input a wave non-invasively from the surface of a living body to reflect on the body fluid circulating in the living body in order to analyze the state of blood from the movement and position, and estimate the state of health to accurately determine information about circulation no matter how strained a blood vessel may get at the determination site in the living body. <P>SOLUTION: The apparatus for measuring circulation movement comprises a circulation sensor for transmitting a wave from the surface to the inside of a living body, and a processor for using a received wave to analyze the circulation movement, wherein the circulation sensor has a means to determine blood pressure and bloodstream to make the processor calculate information about blood viscosity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a body fluid circulating in a living body and a tissue measuring device constituting a circulatory organ, sensor technology, and in particular, grasps the blood state at a peripheral site to evaluate health, diagnose a disease, evaluate a drug, etc. It relates to the technology to be performed.

  Conventionally, various methods using blood information have been performed in order to evaluate the health of a living body, diagnose a disease, grasp the influence of a drug on a living body, and the like. For example, medically, there is a method in which blood is collected from a living body, and the blood is applied to a component analyzer to obtain circulation information from the ratio of various blood components contained in the blood to evaluate the health state.

  Here, circulatory dynamics refers to the state in which blood and lymph fluid that moves inside the circulatory organ, gives oxygen and nutrients to living tissues and cells, and carries carbon dioxide and waste products continuously change over time. For example, the blood flow velocity, the blood flow change, the fluidity, the pulse wave, and the like correspond to this.

  However, with this method, it is necessary to puncture the living body with a needle when collecting blood, so if you want to measure the circulatory dynamics and evaluate the health condition when you are away from a medical institution such as a general household, It is not suitable for always wearing and measuring circulatory dynamics to constantly evaluate the health condition. Non-invasively input waves from the surface of the living body, reflect the body fluid flowing through the living body, especially blood, and the blood state from movement and position. A device has been developed to measure the circulatory dynamics and evaluate the health condition.

  On the other hand, as a conventional example of medical health assessment, in the specialized magazine “Food Research Result Information, NO.11 1999”, Mr. Shinji Kikuchi titled “Measurement of whole blood fluidity using capillary model” In other words, a method of measuring blood rheology from the passage time of blood flow under a constant pressure using a microchannel array manufactured by a lithographic technique is known. By using this method, blood rheology can be measured as circulation information, and the health condition can be evaluated from this value.

  In addition, as a conventional example for non-invasive health evaluation at home, etc., a form in which a wave such as light is transmitted from the skin surface of a living body and reflected light is received and the flow rate of blood flowing through the blood vessel is detected. There is. In this method, an acceleration pulse wave, which is one of circulation information, is obtained by differentiating the detected blood flow volume, and the health state is evaluated. FIG. 15 is a block diagram showing an internal configuration of the signal processing unit 600 of the conventional circulation information measuring apparatus and a connection state between the signal processing unit 600 and the circulation sensor unit 607.

  As shown in the figure, the signal processing unit 600 is roughly configured by a drive unit (light emission) 601, a reception unit (light reception) 602, a signal calculation unit 603, and an output unit 604. The drive unit (light emission) 601 turns on the light emitting element 605 installed in the circulation sensor 607 and transmits drive energy for irradiating light toward the blood vessel. A receiving unit (light receiving) 602 amplifies a signal generated when the light receiving element 606 installed in the circulation sensor 607 performs photoelectric conversion. The signal calculation unit 603 executes various processes related to the measurement of circulation information by executing a processing program stored in a storage area (not shown) provided therein, and outputs the processing result to the output unit 604. . And the signal calculating part 603 calculates | requires the acceleration pulse wave as circulation information by converting a received light signal level into the blood volume change amount and differentiating the value twice.

  FIG. 16 shows an example of a conventional system for quantitatively measuring blood flow. A flow velocity measurement system 702 and a blood vessel diameter measurement system 701 are configured. By placing the ultrasonic probe 706 at a right angle to the blood vessel 705, an ultrasonic beam is applied to the blood vessel 705, the blood vessel diameter is measured from the echo of the blood vessel wall, and the flow velocity is measured by the other two ultrasonic probes 707 and 708. Measure. By using two ultrasonic beams, the flow velocity can be measured from the angle between them regardless of the angle between the ultrasonic beam and the blood vessel. The measured blood vessel diameter and flow velocity are processed by the microcomputer 703 to obtain the blood flow rate. This is displayed on the display 704.

  However, in the blood rheology measurement method using a microchannel array, in order to collect blood from a subject, blood must be collected by inserting a needle into the elbow using an injection needle and going to a medical institution, etc. There is. In addition, when a wave is input from the surface of the living body as shown in the conventional example, the blood state is reflected from the body fluid flowing through the living body, the blood state is analyzed from the movement and position, and the health state is evaluated by obtaining circulation information, Since the influence of blood vessel tension and relaxation (change in blood vessel diameter) affects the blood flow state in the living body and changes the circulation information, it becomes difficult to measure the circulation information for evaluating the original health condition. ing. In addition, since the blood flow state changes depending on blood pressure fluctuations, it is necessary to consider changes in blood vessels and blood pressure when evaluating circulatory dynamics.

  Further, in a conventional blood flow measurement system, it is necessary to use an ultrasonic probe for measuring a blood vessel diameter and measuring a blood flow. If an independent probe is used, it is difficult to align the position, so it is difficult to measure the blood vessel diameter and blood flow velocity at the same location in the blood vessel, and there is a limit to miniaturization. Furthermore, since it is an independent probe, there are problems such as difficulty in adjusting sensitivity variations for each probe and unsuitability for mass production.

  In the measurement of the circulatory dynamics of a peripheral part of a living body (for example, a fingertip), the measurement area is small and the blood vessel diameter is small. There was also a problem that measurement was difficult.

  Furthermore, since the influence of blood pressure is not taken into account, accurate evaluation is impossible from the viewpoint of evaluation of circulatory dynamics.

  Therefore, the problem to be solved by the present invention is to input wave motion from the surface of the living body non-invasively, reflect it on the body fluid flowing through the living body, analyze the state of blood and the like from the movement and position, and seek circulation information Is to accurately measure circulatory information regardless of the degree of blood vessel tension at the measurement site in the living body.

  It is another object of the present invention to provide a circulatory dynamic sensor capable of accurately measuring circulatory dynamics even in a measurement site having a narrow measurement area and a small blood vessel diameter.

  Therefore, in the circulatory dynamics measuring device, the circulatory dynamics measuring method, the blood pressure measuring method and the circulatory dynamics sensor of the present invention, the circulatory dynamics are calculated from the circulatory sensor unit that transmits and receives waves from the surface of the living body to the inside of the living body, and the received waves. In the circulatory dynamics measuring apparatus having a processing unit, the circulation sensor unit has means for measuring blood flow and means for measuring blood pressure, and the processing unit calculates information on blood viscosity from the measured blood pressure and blood flow. The configuration is as follows.

  The present invention also relates to a circulatory dynamics measuring device having a circulatory sensor unit that transmits and receives waves from the surface of the living body to the inside of the living body and a processing unit that calculates the circulatory dynamics from the received waves. And means for measuring blood pressure, and the processing unit derives a resistance component related to the shape of the blood vessel from the blood viscosity value measured by collecting blood in advance and the measured blood pressure and blood flow volume. .

  The present invention also includes a procedure for deriving a resistance component related to the shape of a blood vessel from blood viscosity values, blood pressure, and blood flow measured in advance, and a procedure for calculating information related to blood viscosity from the blood pressure and blood flow.

  The present invention also includes a procedure for measuring a blood flow, a procedure for calculating the blood vessel resistance of the subject from the blood flow and the blood pressure value measured in advance, and a procedure for calculating the blood pressure value of the subject from the blood vessel resistance and the blood flow. .

  The present invention also includes at least two piezoelectric elements that transmit and receive ultrasonic waves, measures blood flow velocity with at least one piezoelectric element, and measures blood vessel diameter with at least one other piezoelectric element. In the sensor, the piezoelectric element for measuring the blood flow velocity and the piezoelectric element for measuring the blood vessel diameter are arranged on the same substrate.

  In the present invention, a plurality of piezoelectric elements for measuring a blood vessel diameter are provided. In the present invention, the driving frequency of the blood vessel diameter measurement piezoelectric element and the blood flow velocity measurement piezoelectric element are different.

  In the present invention, the piezoelectric element has a rectangular shape, and the piezoelectric element for blood flow velocity measurement and the piezoelectric element for blood vessel diameter measurement are arranged so that the extension lines in the longitudinal direction are orthogonal to each other.

  In the present invention, the piezoelectric element is disposed on the back surface of the substrate on which the piezoelectric element is disposed. The present invention also provides a circulatory dynamics measuring device having a circulatory dynamics sensor, a drive circuit for driving a piezoelectric element, and a processing unit for processing a wave received from the piezoelectric element. And the operation timing of the piezoelectric element for measuring blood flow velocity are shifted.

  Details will be described in the following embodiments of the present invention.

  As described above, according to the circulatory dynamics measuring apparatus of the present invention, blood collection or the like is not required, and circulatory dynamics can be measured. Moreover, since blood flow volume and blood pressure can be measured simultaneously or both circulation information can be measured, the accuracy of the measured circulation dynamics can be improved.

  Furthermore, according to the circulation sensor of the present invention, a small and highly accurate sensor capable of simultaneously measuring the blood vessel diameter and the blood flow velocity can be provided. It becomes possible to measure the information.

  The measurement principle of the circulatory dynamics measuring apparatus of the present invention is to obtain circulatory information from time-dependent changes in circulation components such as blood flow velocity, blood pressure and blood vessel diameter that appear during the pulsation of a pulse. And the circulatory dynamics measuring device of the present invention is a circulatory dynamics measuring device having a circulatory sensor part that transmits and receives a wave from the surface of the living body to the inside of the living body and a processing part that calculates the circulatory dynamics from the received wave. The basic structure is a structure having means for measuring blood pressure and blood flow, and the health condition of the living body is evaluated from the circulation information.

  As an indicator of the circulation dynamics of the peripheral site of the living body, blood flow velocity and blood flow volume of the blood vessel of the peripheral site can be mentioned, but as described above, the blood vessel diameter changes depending on the tension state and temperature, and the blood pressure also determines Considering that the flow rate changes, these indicators alone are not sufficient. When the blood vessel at the peripheral site is replaced with an electric circuit, the blood flow rate Q corresponds to the current, and the blood pressure value between two different points in the blood vessel corresponds to the voltage V. The blood flow rate Q is the amount of blood that passes through a certain point in the blood vessel per unit time. Both the blood flow velocity and the blood flow described above are measurement results of a part of Q or the Q itself, and thus are insufficient as measurement information.

Here, considering the vascular resistance R as the ratio of V and Q,
Vascular resistance R = Blood pressure difference V / Blood flow rate Q Equation 1
This R can be considered as a resistance component of the electric circuit.

The vascular resistance R includes a shape factor such as the thickness of the blood vessel and a factor of blood viscosity. R is a shape factor (blood vessel shape resistance component), and ρ is a blood viscosity. As a factor,
R = r × ρ = blood pressure difference V / blood flow rate Q Equation 1 ′
It becomes.

  In the same subject, it is unlikely that r changes greatly every day, so R is considered to be greatly affected by the viscosity of blood. Therefore, in a relatively short period (several days), the change in R can be regarded as a change in blood viscosity ρ. Therefore, by measuring the vascular resistance R every day or measuring the vascular resistance R before and after ingesting a specific food, it is possible to know the change in the blood viscosity ρ.

  Since blood pressure V is a driving force for blood flow, a blood pressure difference between two points in the blood vessel acts as a driving force for blood flow. On the other hand, the vascular resistance R is a physical factor that hinders blood flow in the blood vessel. Resistance occurs because viscous blood moves through blood vessels of a limited diameter, and part of the energy is lost as heat.

  This vascular resistance R covers all the effects of blood vessel diameter, blood flow, and blood pressure, and is considered to be effective as an index of circulatory dynamics. The basic principle of the present invention is to use this R as an indicator of the circulation dynamics of the peripheral site.

  Since r is considered to be greatly influenced by age and sex, the average value of R values for each age and sex is stored as a database, and if the measured R value is larger than this average value, the viscosity of blood It is also possible to use an indicator that the viscosity of blood is low if the value is large or small.

  In addition, in order to keep blood pressure measured in advance and have the subject input it, or to keep the blood vessel dilated, the measurement part is heated, kept warm, etc. It can be used as an indicator of Note that an ultrasonic wave is generally used for the wave used for detecting the flow velocity, but other waves such as a laser can also be used.

Hereinafter, a circulating information measuring apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
(Embodiment 1)
An embodiment of a circulatory dynamics measuring apparatus according to the present invention will be described with reference to FIGS. In this embodiment, the basic configuration of the circulatory dynamics measuring apparatus of the present invention will be described.

  FIG. 1 is a diagram showing an external configuration of an embodiment of a circulatory dynamics measuring apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, FIG. 3 is a sectional view of a ring portion 1, and FIG. 4 is a signal processing unit, and FIG. 5 is an explanatory diagram showing waveforms of measured blood pressure, blood flow velocity, and blood vessel diameter. As shown in FIG. 1, the circulatory dynamics measuring device is divided into three parts: a ring part 1, a signal processing part 2, and a blood pressure measuring part 8.

  FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. As shown in FIG. 2, a circulation sensor 101 exists inside the ring part 1. FIG. 3 shows a transparent view of the inside of the ring viewed from the direction B shown in FIG. The circulation sensor 101 has a blood flow velocity measuring piezoelectric element 102, a blood flow velocity measuring piezoelectric element 103, and a blood vessel diameter measuring piezoelectric element 104 attached to the abdomen of the finger 6. A blood pressure sensor 105 is attached to the blood pressure measurement unit 8.

  In this embodiment, piezoelectric elements (PZT) are used as the blood flow velocity measuring piezoelectric elements 102 and 103 and the blood vessel diameter measuring piezoelectric element 104. The blood pressure measurement unit 8 is configured by a compression band (cuff), can tighten the finger 6 with a predetermined pressure, and measures blood pressure from the pressure when blood flows. The blood pressure sensor 105 only needs to measure blood flow, pulse wave, and the like. In this embodiment, the blood pressure sensor 105 measures the pulse wave. In addition, the ring part 1 itself is composed of a compression band, and blood pressure can be measured from blood flow information measured from the circulation sensor 101.

  Since the artery 5 in the finger 6 extends to the fingertip through both sides of the abdomen of the finger 6, the blood flow velocity measuring piezoelectric elements 102 and 103 are used to measure the blood flow in the artery. 2 is attached to a portion shifted to the left from the center of the belly of the finger 6 as shown in FIG. 2 so that ultrasonic waves can be accurately incident in the vicinity of the artery. As a result, reflection from the artery can be reliably captured, and blood flow measurement accuracy is improved. Although the first embodiment is shifted to the left, the effect is the same even if it is shifted to the right in the vicinity of the right artery.

  Ultrasound is harmless if it is set to a low intensity even if it enters the living body, and it is less affected by skin color and ambient light compared to light, etc. Yes.

  In addition, it is possible to use a sensor using light or the like by devising a structure such as a holding method for blocking disturbance light.

  The circulatory dynamics measuring apparatus according to the first embodiment can be always carried by, for example, wearing the ring part 1 on the finger 6 and carrying the signal processing part 2 and the blood pressure measurement part 8 on the arm. Further, for example, the signal processing unit 2 may be attached to the finger 6 similarly to the ring unit 1. The signal processing unit 2, the blood flow velocity measuring piezoelectric elements 102 and 103, and the blood vessel diameter measuring piezoelectric element 104 installed in the ring unit 1 are connected by a conducting wire, and from the signal processing unit 2 through this conducting wire. A driving voltage signal is input to the blood flow velocity measuring piezoelectric element 102, and a voltage signal measured from the blood flow velocity measuring piezoelectric element 103 is input to the signal processing unit 2.

  FIG. 4 is a block diagram showing an internal configuration of the signal processing unit 2 of the circulatory dynamics measuring apparatus according to the first embodiment and a connection state between the signal processing unit 2, the circulation sensor unit 101, and the blood pressure sensor 105. As shown in the figure, the signal processing unit 2 is roughly configured by drive units 302 and 305, reception units 301 and 303, a signal calculation unit 304, and an output unit 306.

  The drive units 302 and 305 according to the first embodiment vibrate the blood flow velocity measuring piezoelectric element 102 and the blood vessel diameter measuring piezoelectric element 104 installed in the circulation sensor 101 so that ultrasonic waves are incident on the blood vessel 5. Send drive voltage. The receiving units 303 and 301 receive voltages generated when the blood flow velocity measuring piezoelectric element 103 and the blood vessel diameter measuring piezoelectric element 104 installed in the circulation sensor 101 receive ultrasonic waves.

  The signal calculation unit 304 executes various processes related to the measurement of circulatory dynamics by executing a processing program stored in a storage area (not shown) provided therein, and outputs the processing results to the output unit 306. . In addition, the signal calculation unit 304 compares the frequency of the ultrasonic wave emitted from the blood flow velocity measuring piezoelectric element 102 with the frequency of the ultrasonic wave received by the blood flow velocity measuring piezoelectric element 103, thereby obtaining a blood flow. Calculate the Doppler effect. Then, the blood flow velocity flowing through the blood vessel 5 is calculated from the frequency change, and the time change of the velocity is obtained.

Next, the method for measuring circulatory dynamics according to Embodiment 1 will be described. FIG. 5 shows a graph of changes over time of the blood flow velocity v, the blood vessel diameter d, and the blood pressure V with the pulsation. Here, if the blood flow is Q,
Q = 1/2 * [pi] * (d / 2) 2 * v = 1/8 * [pi] d2v Equation 2
And the vascular resistance R can be determined by referring to Equation 1 ′
R = ρ × r = V / Q = 8V / πd2v Equation 3
It becomes.

  Here, it is desirable to measure the blood pressure difference between two different points in the blood vessel 5 (the left and right parts across the ring part 1 in FIG. 3), but the internal pressure of the vein is as low as 5 to 15 mmHg. Since the internal pressure of the artery is as high as about 100 mmHg, the blood pressure value on one side is regarded as 0 mmHg and the blood pressure on only one side of the artery is measured this time. In Equation 2, the blood flow rate is derived from the blood vessel diameter d and the blood flow velocity v. However, it is also possible to use a photoelectric volume pulse wave waveform. In this case, the amplitude of the pulse wave corresponds to the blood flow rate. To do. In this case, since the amount of attenuation of light differs depending on the living body, it is difficult to obtain the absolute value of the blood flow, but it is possible to derive a relative change in the subject.

  There is a correlation between R calculated by using Equation 3 for the diameter d and blood pressure V at the time when the blood flow at each pulse becomes the maximum blood flow velocity vmax in FIG. It was confirmed that it can be used. Therefore, by measuring the blood flow velocity v, the blood vessel diameter d, and the blood pressure V, it is possible to accurately grasp the circulation state.

  For example, when this R is large, it can be said that the blood rheology is high and the viscosity of the blood is high.

  As for blood pressure V, it is desirable to use the highest blood pressure value minus the lowest blood pressure value. However, when measurement is difficult, it is confirmed that only the highest blood pressure value can be used as a certain index.

  The vascular resistance R changes depending on the viscosity of the blood. If it is assumed that it is almost constant for each subject, once the vascular resistance R is calculated by Equation 3, the vascular diameter d and the blood flow velocity v are measured thereafter. It is also possible to estimate the blood pressure V.

Furthermore, once blood is collected and the viscosity ρ of the blood is measured and the blood vessel shape resistance component r of the subject is derived, r is unlikely to fluctuate greatly every day. The blood viscosity component ρ can be measured more accurately by measuring the blood pressure V. Moreover, since the value of r is a blood vessel shape resistance component, it can also be used as an index such as the degree of arteriosclerosis.
(Embodiment 2)
The second embodiment is an embodiment in which the structure of the circulation sensor 101 used in the circulatory dynamics measuring apparatus of the present invention is modified.

  6 is an explanatory view showing the arrangement of the finger 6, blood vessel 5 and circulation sensor 101, FIG. 7 is an explanatory view of the configuration of the circulation sensor 101, and FIGS. 8 and 9 are states in which ultrasonic waves are transmitted by the circulation sensor 101. It is explanatory drawing of.

  As shown in FIG. 7, the circulation sensor 101 includes blood flow rate measuring piezoelectric elements 102 and 103, a blood vessel diameter measuring piezoelectric element 104, and a substrate 200. It should be noted that wiring for connecting to a drive circuit for vibrating the piezoelectric elements 102, 103, and 104, electrodes provided on the piezoelectric element, and for easily transmitting ultrasonic waves to the inside of the living body and for the piezoelectric element The acoustic matching layer provided for the purpose of protecting the electrodes is not shown.

  As shown in FIG. 8, ultrasonic waves are transmitted into the living body by the blood flow measurement piezoelectric element 102. The ultrasonic beam 110 is reflected by the blood vessel 5, tendon 15, vein 16, and bone 17, which are tissues inside the living body, and is received by the blood flow measurement piezoelectric element 103. At this time, the transmitted ultrasonic wave is reflected by blood (red blood cells) flowing in the blood vessel 5. Since the red blood cells are moving, the frequency of the received ultrasonic waves is changed by the Doppler effect corresponding to the moving speed. The blood flow rate can be measured by this Doppler shift frequency.

  Since other tissues have not moved, in this case, even if the range of the ultrasonic beam 110 is wide, the measurement result is not greatly affected. Conversely, as the ultrasonic beam 110 is wider, the alignment with the blood vessel 5 is increased. It becomes easier and easier to measure.

  On the other hand, in the case of blood vessel diameter measurement, if the ultrasonic beam is wide as shown in FIG. 8, unnecessary reflection occurs from the bone 17, the tendon 15, and the vein 16, and the measurement result is adversely affected.

  Therefore, as shown in FIG. 9, it is desirable to narrow the range of the ultrasonic beam 110 of the blood vessel diameter measuring piezoelectric element 104 and not irradiate tissues other than the blood vessel 5. The blood vessel diameter can be measured by measuring the time difference between the ultrasonic waves reflected by the inner wall of the blood vessel.

  At this time, since the spread of the ultrasonic beam 110 is narrow, alignment with the blood vessel 5 becomes difficult. However, as shown in FIG. This can be dealt with by selecting and using the blood vessel diameter measuring piezoelectric element 104 at the obtained position.

  In the case of the present embodiment, the blood flow velocity measuring piezoelectric elements 102 and 103 both use PZT having an outer shape of 0.5 × 8 mm, a thickness of 0.2 mm, and a driving frequency of 9.6 MHz. As P 104, PZT having an outer shape of 2 × 2 mm, a thickness of 0.2 mm, and a driving frequency of 9.6 MHz was used.

  As for the driving frequency, the frequencies suitable for the blood flow velocity measuring piezoelectric elements 102 and 103 and the blood vessel diameter measuring piezoelectric element 104 are different.

The Doppler shift frequency Δf due to the blood flow velocity v is expressed by Δf = 2vf · cos θ / c Equation 4 where c is the sound velocity in the living body, θ is the ultrasonic incident angle, and f is the drive frequency.
Therefore, Δf increases as the drive frequency f increases, and there is a great advantage in later signal processing. However, the relationship between the driving frequency f and the attenuation coefficient of the ultrasonic wave inside the living body is
H = H0e-2αlf
l: Distance to blood vessel α: Attenuation rate H0: Amplitude at distance 0 Equation 5 is satisfied. The higher the frequency f, the lower the intensity of the ultrasonic wave.

  Furthermore, when the blood flow also flows into the vein 16 and the speed is taken into consideration (desirable to be separated), the speed of the blood flowing through the vein 16 is slower than that of the artery, so the difference in Doppler shift frequency due to the difference in blood flow velocity is reduced. Separation is possible by increasing the size, and for this purpose, it is necessary to increase the driving frequency.

  Considering the above, the driving frequency of the blood flow velocity measuring piezoelectric elements 102 and 103 is optimally about 5 to 10 MHz.

  On the other hand, in the case of the blood vessel diameter measuring piezoelectric element 104, the wavelength of the ultrasonic wave has a resolution in the distance direction. For example, when the driving frequency is 10 MHz and the sound speed of the living body is 1500 m / s, the wavelength is 150 μm. This wavelength is the resolution.

  Assuming that the blood vessel diameter of the artery at the fingertip is about 1 mm and the change is about 200 μm, considering that it is desirable that the attenuation of the ultrasonic wave is small, the optimum driving frequency is about 7.5 MHz.

  In addition, since the blood vessel diameter and blood flow velocity of the artery differ depending on the measurement site (radial artery, carotid artery, capillary artery), the driving frequency is different.

  In the present embodiment, the blood flow velocity measuring piezoelectric elements 102 and 103 are separately used for ultrasonic transmission and reception, but this may be performed by one.

  Further, in the circulation sensor 101 as shown in FIG. 7, if the blood flow velocity measuring piezoelectric element 102 is used for transmission, the timing for driving the blood flow velocity measuring piezoelectric element 102 and the timing for driving the blood vessel diameter measuring piezoelectric element 104 are as follows. In the same case, ultrasonic waves influence each other through the substrate 200, causing noise. Therefore, it is necessary to shift the drive timing. In the case of the present embodiment, the sound velocity of the substrate 200 is 2500 m / s, and the distance between the blood flow velocity measuring piezoelectric element 102 and the blood vessel diameter measuring piezoelectric element 104 is 5 mm. The time for which the ultrasonic wave propagated to the blood vessel diameter measuring piezoelectric element 104 is 2 μs. Therefore, it is necessary to shift the drive timing more than this time difference.

For the ultrasonic waves reflected by the blood vessel 5, the distance between the blood flow velocity measuring piezoelectric element 102 and the blood vessel diameter measuring piezoelectric element 104 is separated by about 5 mm. Although it was not necessary to consider the mutual interference of the waves, this effect must also be considered when the distance between the two piezoelectric elements is reduced.
(Embodiment 3)
The third embodiment is an embodiment in which the circulation sensor used in the circulatory dynamics measuring device of the present invention is modified.

  FIG. 10 shows an example of the circulation sensor 101. FIG. 11 is an explanatory diagram of the positional relationship between the circulation sensor 101 and a blood vessel. The blood pressure measurement unit and the processing unit are not shown.

In general, the smaller the area of PZT, the closer it is to a spherical wave, so the angle at which the ultrasonic beam spreads becomes wider. (Low directivity) Therefore, if the area is made too small, reflection from living tissue other than blood vessels increases, and the measurement accuracy decreases significantly. In addition, when the ultrasonic beam becomes wider, the intensity of the ultrasonic wave reflected and received by the same piezoelectric element also decreases, so the piezoelectric element has a shape that is as wide as possible and that is not easily irradiated with ultrasonic waves other than blood vessels. Is desirable.

  Furthermore, when the width w and length L of the piezoelectric element in FIG. 10 are reduced, the vibration mode in the length direction of the piezoelectric element becomes close to the vibration mode in the thickness direction, and the vibration is effectively vibrated at a desired frequency in the thickness direction. Can not be made. Therefore, a certain length is required in the length direction and the width direction.

  FIG. 10 shows a circulation sensor 101 in which the blood vessel diameter measuring piezoelectric element 104 is rectangular and arranged so as to be orthogonal to the blood flow velocity measuring piezoelectric elements 102 and 103.

  By making the width W of the piezoelectric element slightly narrower than the diameter of the blood vessel, the width of the ultrasonic radiation area and the blood vessel can be made substantially equal, and the measurement sensitivity can be increased. In this embodiment, since the finger blood vessel is targeted, the width W is set to about 0.8 mm.

  Further, if the width L of the piezoelectric element is about 6 mm, the ultrasonic wave does not spread too much, and the blood vessel can be effectively irradiated with the ultrasonic wave.

It is also possible to provide a lens for converging the ultrasonic wave on the blood vessel diameter measuring piezoelectric element 104, and in this case, the restraint conditions are slightly gentler than the shape of the piezoelectric element described above.
(Embodiment 4)
The fourth embodiment is an embodiment in which the circulation sensor 101 used in the circulatory dynamics measuring apparatus of the present invention is modified.

  FIG. 12 is an explanatory diagram showing an example of the circulation sensor 101, and FIG. 13 is an explanatory diagram of a state in which the circulation sensor 101 is held on the fingertip 6. The blood pressure measurement unit and the processing unit are not shown.

  The circulation sensor 101 of FIG. 12 has a configuration in which blood flow velocity measuring piezoelectric elements 102 and 103, a blood vessel diameter measuring piezoelectric element 104, a substrate 200, and a pressure pulse wave measuring piezoelectric element 150 are provided on the back surface of the substrate 200. .

As shown in FIG. 13, by supporting the circulation sensor 101 with the support portion 111, the pressure fluctuation due to blood vessel contraction can be measured as a pressure pulse wave by the pressure pulse wave measurement piezoelectric element 150. With such a configuration, once the blood pressure is measured by a blood pressure measurement unit (not shown), it is possible to estimate blood pressure fluctuations by measuring the pressure pulse wave thereafter, and finger tightening with a cuff is performed every time. This eliminates the need to perform the measurement and makes it easier to use.
(Embodiment 5)
The fifth embodiment is an embodiment in which the circulation sensor used in the circulatory dynamics measuring device of the present invention is modified.

FIG. 14 is an explanatory diagram showing an example of the circulation sensor 101.
As shown in Expression 4, the blood flow velocity measuring piezoelectric elements 102 and 103 have a larger frequency change due to the Doppler effect as the angle θ with respect to the blood vessel is smaller. Therefore, as shown in FIG. 14, the blood flow velocity measuring piezoelectric elements 102 and 103 are provided on the inclined surface of the substrate 201 provided with a predetermined angle (π / 2−θ). On the other hand, the blood vessel diameter measuring piezoelectric element 104 cannot accurately measure a blood vessel diameter unless an ultrasonic wave is incident perpendicularly to the blood vessel. Therefore, as shown in FIG. 14, the blood vessel diameter measuring piezoelectric element 104 is provided on the flat portion of the substrate 201. Furthermore, if the sensor surface is uneven, a gap is formed between the sensor surface and the ultrasonic wave may be significantly attenuated by the gap. For this reason, by providing the acoustic matching layer 202 on the sensor surface and eliminating the irregularities, the contact state with the skin can be kept good.

  It is also possible to perform transmission / reception with one piezoelectric element, and to arrange the substrate 201 in two steps, one for each inclination, and measure the absolute flow velocity from the difference in Doppler shift frequency. is there.

4 is an explanatory diagram illustrating configurations of a ring unit, a signal processing unit, and a blood pressure measurement unit according to Embodiment 1. FIG. It is explanatory drawing of the AA 'cross section in FIG. It is sectional drawing seen from the B direction in FIG. 4 is an explanatory diagram of a processing unit according to Embodiment 1. FIG. It is explanatory drawing which showed the fluctuation | variation of the blood flow velocity, the blood pressure, and the blood vessel diameter. It is the figure which showed the positional relationship of the circulation sensor 101 which concerns on Embodiment 2, and a blood vessel. It is explanatory drawing of the circulation sensor 101 of Embodiment 2. FIG. It is a schematic diagram of the radiation state of an ultrasonic wave. It is a schematic diagram of the radiation state of an ultrasonic wave. It is explanatory drawing of the circulation sensor of Embodiment 3. FIG. It is explanatory drawing which shows the positional relationship of the circulation sensor of Embodiment 3, and a blood vessel. It is explanatory drawing of the circulation sensor of Embodiment 4. It is explanatory drawing which showed the relationship between a holding | maintenance part, a circulation sensor, and a finger | toe. FIG. 10 is an explanatory diagram of a circulation sensor according to a fifth embodiment. It is a block diagram of the drive circuit of the conventional circulatory dynamics measuring apparatus. It is a block diagram of the conventional blood flow rate measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ring part 2 Signal processing part 8 Blood pressure measurement part 101 Circulation sensor 102, 103 Blood flow velocity measurement piezoelectric element 104 Blood vessel diameter measurement piezoelectric element 105 Blood pressure sensor 110 Ultrasonic beam 111 Support part 150 Pressure pulse wave measurement piezoelectric element 5 Blood vessel 6 fingertip 301 receiving unit 302 driving unit 303 receiving unit 304 signal calculating unit 305 driving unit 306 output unit 600 processing unit 601 driving unit 602 receiving unit 603 signal calculating unit 604 output unit 605 light emitting element 606 light receiving element 701 blood vessel diameter measuring system 702 Flow velocity measurement system 703 Microcomputer 704 Display 705 Blood vessel 706, 707, 708 Ultrasonic probe 709 Body surface

Claims (6)

In a circulatory dynamic sensor having at least two piezoelectric elements for transmitting and receiving ultrasonic waves, measuring a blood flow velocity with at least one of the piezoelectric elements, and measuring a blood vessel diameter with at least one other piezoelectric element,
A circulatory dynamic sensor, wherein the piezoelectric element for measuring the blood flow velocity and the piezoelectric element for measuring the blood vessel diameter are arranged on the same substrate. The circulatory dynamic sensor according to claim 1, comprising a plurality of piezoelectric elements for measuring the blood vessel diameter. 3. The circulatory dynamic sensor according to claim 1, wherein driving frequencies of the piezoelectric element for measuring a blood vessel diameter and the piezoelectric element for measuring a blood flow velocity are different. The piezoelectric element has a rectangular shape, and the piezoelectric element for measuring blood flow velocity and the piezoelectric element for measuring blood vessel diameter are arranged so that extension lines in the longitudinal direction are orthogonal to each other. The circulatory dynamic sensor according to any one of claims 1 to 3. The circulatory dynamic sensor according to any one of claims 1 to 4, wherein a piezoelectric element is disposed on a back surface of the substrate on which the piezoelectric element is disposed. A circulatory dynamics measuring apparatus comprising the circulatory dynamic sensor according to any one of claims 1 to 5, a driving circuit that drives the piezoelectric element, and a processing unit that processes a wave received from the piezoelectric element. ,
An apparatus for measuring circulatory dynamics, wherein the operation timing of the piezoelectric element for measuring blood vessel diameter and the piezoelectric element for measuring blood flow velocity are shifted.

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