JP6692026B2 - Blood vessel elasticity index value measuring device, blood pressure measurement device, and blood vessel elasticity index value measuring method - Google Patents

Description

  The present invention relates to a blood vessel elasticity index value measuring device or the like for measuring a blood vessel elasticity index value of an artery.

  As a non-pressurized blood pressure measuring method, a non-invasive blood pressure measuring method using ultrasonic waves is known. For example, Patent Document 1 discloses a method of capturing a blood pressure change and a blood vessel diameter as a non-linear relationship, and calculating blood pressure from a stiffness parameter β which is one of blood vessel elasticity index values and a blood vessel diameter.

JP, 2004-41382, A

  In blood pressure measurement, there is a desire to measure blood pressure accurately, even if it is non-invasive, and we want to realize accurate blood pressure measurement as continuous measurement for each beat (also called constant measurement or constant measurement). There is a request that. According to the blood pressure measurement method disclosed in Patent Document 1 described above, if the blood vessel diameter can be measured with high accuracy, it seems that high-accuracy continuous measurement of blood pressure can be realized. However, the practical application of highly accurate constant blood pressure measurement is not so simple.

  One of the factors that make practical application difficult is the blood vessel elasticity index value. For example, in the conventional blood pressure measurement method using the stiffness parameter β, which is one of the vascular elasticity index values, it is necessary to calibrate the stiffness parameter β in advance by performing a calibration process using a pressurization type sphygmomanometer. is there. The stiffness parameter β calibrated in advance was used as a fixed value while the blood pressure was measured without pressurization.

  However, since the hardness (elasticity) of the blood vessel changes due to the action of the autonomic nerve, etc., the accuracy of measuring the blood pressure is reduced in the conventional method in which the blood vessel elasticity index value must be a fixed value. That is, the reliability of the measured blood pressure value may decrease as time elapses from the calibration of the blood vessel elasticity index value. Therefore, there is a limit to the time during which the accuracy of constant measurement can be guaranteed.

  The problem of the conventional method is that the calibration process needs to be performed before performing the constant measurement, and the calibration process cannot be performed while performing the constant measurement. In the end, there was a problem that a calibration process for calculating the blood vessel elasticity index value using a pressurization type sphygmomanometer was necessary.

  The present invention has been devised to solve the above-described problems, and an object of the present invention is to eliminate the need for a pressurization type sphygmomanometer and to enable measurement of a vascular elasticity index value under non-pressurization. Is to propose.

  A first invention for solving the above-mentioned problem is to use a measurement result obtained by measuring a blood vessel diameter at a first position of an artery and a measurement result obtained by measuring a blood vessel diameter at a second position of the artery. Pulse wave velocity measuring unit for measuring the first pulse wave velocity at the first time and the second pulse wave velocity at the second time, which is the characteristic period of the vascular diameter variation of the artery, and the first pulse wave. Calculating the vascular elasticity index value of the artery using the propagation velocity, the second pulse wave propagation velocity, and the blood vessel diameter at the first position at each of the first time period and the second time period And a blood vessel elasticity index value measuring device.

  According to the first aspect of the present invention, the first pulse wave velocity of the first time period, the second pulse wave velocity of the second time period, and the first time period thereof, which are the characteristic periods of the fluctuation of the blood vessel diameter of the artery due to the pulsation. Also, the blood vessel elasticity index value can be calculated using the blood vessel diameter of each of the second periods. Since all of the first pulse wave velocity, the second pulse wave velocity, and the blood vessel diameter can be measured under non-pressurized condition, the measurement of the blood vessel elasticity index value under non-pressurized condition can be realized.

  In a second aspect, the pulse wave velocity measuring section determines the first pulse wave velocity and the second pulse wave velocity by setting the first time period and the second time period as different times within the same beat. It is a blood vessel elasticity index value measuring device of the first invention for measuring.

  According to the second aspect of the invention, the first pulse wave velocity and the second pulse wave velocity are measured as the pulse wave velocity at the first time and the second time which are different times within the same beat. That is, since the pulse wave velocity can be measured for each beat, the vascular elasticity index value can be calculated for each beat.

  3rd invention calculates the said 1st pulse wave propagation velocity and the said 2nd pulse wave propagation velocity by the said pulse wave propagation velocity measurement part performing the predetermined statistical calculation process of the pulse wave propagation velocity between several beats. The blood vessel elasticity index value measuring device according to the first invention.

  According to the third invention, the first pulse wave velocity and the second pulse wave velocity are calculated by performing a predetermined statistical calculation process on the pulse wave velocity between a plurality of beats. As the predetermined statistical calculation processing, for example, an average value or a median value can be adopted. Therefore, it is possible to more accurately measure the blood vessel elasticity index value while suppressing variations in the pulse wave propagation velocity.

  In a fourth invention, the pulse wave velocity measuring section sets one of the first period and the second period as a diastole and the other as an overlapping notch stage, and the first pulse wave velocity and the It is the blood vessel elasticity index value measuring device of any one of the first to third inventions, which measures the second pulse wave velocity.

  According to the fourth aspect, one of the first period and the second period is the diastole period and the other is the double notch stage, so that the first period and the second period can be relatively easily captured. You can As a result, the measurement accuracy of the first pulse wave propagation velocity and the second pulse wave propagation velocity is improved, and the measurement accuracy of the blood vessel elasticity index value can be improved.

  In a fifth aspect, the pulse wave velocity measuring unit measures the first pulse wave velocity and the second pulse wave velocity for each heartbeat, and the blood vessel elasticity index value calculating unit measures each heartbeat. The vascular elasticity index value measuring device according to any one of the first to fourth inventions, which calculates the vascular elasticity index value.

  According to the fifth aspect, since the first pulse wave velocity and the second pulse wave velocity are measured for each heartbeat, the calculation of the blood vessel elasticity index value for each beat can be realized.

  A sixth invention is the vascular elasticity index value measuring device according to any one of the first to fifth inventions, in which the blood vessel elasticity index value calculation unit does not use blood pressure in calculating the blood vessel elasticity index value.

  According to the sixth aspect of the present invention, blood pressure is not used for calculating the blood vessel elasticity index value, and therefore it is not necessary to measure blood pressure. That is, the blood vessel elasticity index value can be measured without performing the blood pressure measurement using the conventional pressurization sphygmomanometer.

  A seventh aspect of the present invention further includes a blood flow velocity measurement unit that measures a first blood flow velocity at the first time and a second blood flow velocity at the second time in the artery, and the blood vessel elasticity index value calculation unit. Is the velocity obtained by subtracting the first blood flow velocity from the first pulse wave velocity instead of the first pulse wave velocity, and the second pulse wave velocity from the second pulse wave velocity instead of the second pulse wave velocity. The vascular elasticity index value measuring device according to any one of the first to sixth inventions, wherein the vascular elasticity index value of the artery is calculated using a velocity obtained by subtracting the second blood flow velocity.

  According to the seventh aspect, in calculating the blood vessel elasticity index value, when the influence of the blood flow velocity appears on the pulse wave propagation velocity, the influence can be reduced.

  An eighth invention is to measure the blood vessel elasticity index value calculating device according to any one of the first to sixth inventions, the blood vessel elasticity index value calculated by the blood vessel elasticity index value calculating device, and the blood vessel diameter of the artery. A blood pressure measurement device comprising: a blood pressure calculation unit that calculates blood pressure using the measurement result.

  According to the eighth aspect, the blood pressure can be calculated using the blood vessel elasticity index value calculated by the above-described blood vessel elasticity index value calculation device and the blood vessel diameter measured when calculating the blood vessel elasticity index value. That is, it becomes possible to measure the blood pressure under no pressure.

  In a ninth aspect, the blood pressure calculation unit is configured such that the blood pressure is proportional to a square of a pulse wave velocity measured by the pulse wave velocity measuring unit and is proportional to an inverse number of the blood vessel diameter. It is a blood pressure measurement device according to an eighth aspect of the present invention, which performs arithmetic processing to calculate the blood pressure.

  According to the ninth aspect, the blood pressure can be calculated by performing a predetermined calculation process that is proportional to the square of the pulse wave velocity and proportional to the reciprocal of the blood vessel diameter.

  A tenth invention uses the blood vessel elasticity index value calculating device of the seventh invention, the blood vessel elasticity index value calculated by the blood vessel elasticity index value calculating device, and the measurement result obtained by measuring the blood vessel diameter of the artery. , Proportional to the square of the velocity obtained by subtracting the blood flow velocity measured by the blood flow velocity measurement unit from the pulse wave velocity measured by the pulse wave velocity measurement unit, and proportional to the reciprocal of the blood vessel diameter And a blood pressure calculating unit that calculates a blood pressure by performing a predetermined calculation process.

  According to the tenth invention, the blood pressure is calculated using the blood vessel elasticity index value calculated by the blood vessel elasticity index value calculation device of the seventh invention and the blood vessel diameter measured when calculating the blood vessel elasticity index value. You can That is, it becomes possible to measure the blood pressure under no pressure. Further, in calculating the blood pressure, if the effect of the blood flow velocity on the pulse wave propagation speed is exhibited, the effect can be reduced.

  An eleventh aspect of the present invention uses the measurement result obtained by measuring the blood vessel diameter at the first position of the artery and the measurement result obtained by measuring the blood vessel diameter at the second position of the artery by the calculation processing unit incorporated in the calculation device. Measuring the first pulse wave velocity of the first time period and the second pulse wave velocity of the second time period, which is the characteristic period of the blood vessel diameter variation of the artery due to pulsation, and the first pulse wave velocity , Calculating the vascular elasticity index value of the artery using the second pulse wave velocity and the blood vessel diameter at the first position at each of the first time period and the second time period. This is a method of measuring the elasticity index value.

  According to the eleventh invention, it is possible to realize a blood vessel elasticity index value measuring method that exhibits the same effects as the first invention.

The figure for demonstrating the whole structure of a blood pressure measuring device. Sectional drawing in the attachment position of a 1st ultrasonic probe and a 2nd ultrasonic probe. It is a time-series waveform example of 1st blood-vessel diameter D1 and 2nd blood-vessel diameter D2, Comprising: (1) Blood-vessel diameter waveform, (2) Acceleration waveform which carried out the second-order differentiation of the blood-vessel diameter, (3) Diastolic acceleration waveform The figure which shows expansion. The graph which shows the example of the blood-vessel diameter blood pressure characteristic in a non-pressurized state. FIG. 3 is a block diagram showing a functional configuration example of a blood pressure measurement device. The figure which shows the data structural example of blood-vessel diameter log data. The figure which shows the data structural example of intermediate data. The figure which shows the data structural example of vascular elasticity index value log data. The figure which shows the data structural example of blood pressure log data. The flowchart for demonstrating the flow of the main processes in a blood-pressure measurement apparatus. The flowchart for demonstrating the flow of a pulse wave propagation velocity measurement process. The flowchart for demonstrating the flow of a blood pressure calculation process. The figure for demonstrating the structure of the probe part in a modification. The block diagram which shows the functional structural example of the blood pressure measurement apparatus in a modification. The figure which shows the data structural example of the intermediate data in a modification. The flowchart for demonstrating the flow of the main processes of the blood-pressure measuring apparatus in a modification. The flowchart for demonstrating the flow of the blood pressure calculation process in a modification.

  Hereinafter, one embodiment to which the present invention is applied will be described, but it goes without saying that the applicable modes of the present invention are not limited to the following embodiments.

FIG. 1 is a diagram for explaining the overall configuration of the blood pressure measurement device 1 according to this embodiment, and is a diagram showing a mounting state of the probe unit 30.
Since the blood pressure measurement device 1 has a configuration in which the main body device 10 and the probe unit 30 are electrically connected by a cable and has a function of measuring a blood vessel elasticity index value, it can also be referred to as a blood vessel elasticity index value measurement device.

The main body device 10 is a kind of computer control device, controls the probe unit 30, and measures the blood vessel diameter of the blood vessel 5 to be measured in real time. Then, the pulse wave propagation velocity is obtained from the measurement result, and the blood vessel elasticity index value of the blood vessel 5 is calculated using the measured blood vessel diameter and the pulse wave propagation velocity. The blood vessel elasticity index value can be calculated every beat. The main body device 10 also calculates the blood pressure using the calculated blood vessel elasticity index value and the measured blood vessel diameter. The calculation of blood pressure can also be performed every beat. That is, it is possible to realize constant measurement (or constant measurement) of continuously measuring the blood pressure of each beat while updating (calibrating) the blood vessel elasticity index value to the latest value for each heartbeat.
In the present embodiment, the blood vessel elasticity index value will be described below as the stiffness parameter β.

  A specific functional configuration of the main body device 10 will be described later with reference to FIG. Operation input unit 200, a display unit 400 having a liquid crystal screen or the like for displaying various information to the user, a sound output unit 430 such as a speaker, a communication unit 450 for communicating with an external device, a hard disk, a memory, etc. And a storage unit 500 for storing programs and data.

  The probe unit 30 has a first ultrasonic probe 31 and a second ultrasonic probe 32 as ultrasonic probes having the same specifications. The first ultrasonic probe 31 and the second ultrasonic probe 32 are thin probes that are attached to the skin of the subject 3, and emit and emit ultrasonic pulses to the subject 3 and receive their reflected waves. ..

[Explanation of the principle]
Next, the principle of blood vessel elasticity index value calculation and blood pressure measurement in the present embodiment will be described.
The first ultrasonic probe 31 and the second ultrasonic probe 32 are fixed to the adhesive pedestal 34 with the scanning planes parallel and separated by a predetermined inter-probe distance Lp (preferably about 10 mm to 30 mm), and the same blood vessel. 5 is configured to measure the blood vessel short-axis direction cross section.

  The adhesive pedestal 34 has a removable adhesive layer on the skin surface, and does not easily come off or peel off even when the subject 3 moves the body. The adhesive pedestal 34 allows the first ultrasonic probe 31 and the second ultrasonic probe 32 to visualize the short axis of the blood vessel 5 (the brachial artery in the present embodiment), and the first ultrasonic probe 31 is located on the heart side ( The second ultrasonic probe 32 is attached to the fingertip side (downstream side) on the upstream side.

The first ultrasonic probe 31 and the second ultrasonic probe 32 may not be mounted on the integrated adhesive pedestal 34, but may be mounted on separate adhesive pedestals 34.
The blood vessel 5 to be measured is not limited to the brachial artery and may be another artery. When the measurement target is an artery in which the hardness (elasticity) of the blood vessel is relatively likely to change due to the action of the autonomic nerves, the action and effect of the present embodiment are greatly exerted. Of course, other arteries such as the carotid artery, the subclavian artery, and the aorta may be measured.

  FIG. 2 is a cross-sectional view of the first ultrasonic probe 31 and the second ultrasonic probe 32 at the attachment positions. The first ultrasonic probe 31 and the second ultrasonic probe 32 each send an ultrasonic pulse signal or a burst signal of several MHz to several tens of MHz toward the blood vessel 5 from the built-in transmitting unit, and the built-in receiving unit supplies blood vessels. The reflected wave is received from each of the front wall 5a and the rear wall 5p. Then, the main body device 10 determines the diameter of the blood vessel 5 from the arrival time difference between the reception wave from the front wall 5a and the reception wave from the rear wall 5p, that is, the first blood vessel diameter D1 measured by the first ultrasonic probe 31, The second blood vessel diameter D2 measured by the second ultrasonic probe 32 is calculated. The transmission of ultrasonic waves and the reception of reflected waves are continuously performed at extremely short time intervals. Therefore, the first blood vessel diameter D1 and the second blood vessel diameter D2 can be continuously calculated. As a result, a waveform whose blood vessel diameter changes in time series is obtained.

  FIG. 3 is a time-series waveform example of the first blood vessel diameter D1 and the second blood vessel diameter D2. (1) Blood vessel diameter waveform, (2) Acceleration waveform obtained by second-order differentiating blood vessel diameter with time, (3) Diastole Corresponds to an enlarged view of the acceleration waveform of. The waveform is simplified for easy understanding.

  According to FIG. 3 (1), the diastole Td, the systole Ts, and the overlapping notch Tn can be found from the changes in the first blood vessel diameter D1 and the second blood vessel diameter D2. Further, since the first ultrasonic probe 31 is arranged closer to the heart than the second ultrasonic probe 32, the pressure wave accompanying the contraction of the heart reaches the first ultrasonic probe 31 earlier. Therefore, the timing of expansion / contraction of the first blood vessel diameter D1 is earlier than that of the second blood vessel diameter D2.

  However, the actual change in the blood vessel diameter does not always clearly show the diastole Td, the systole Ts, and the double notch Tn as shown in FIG. In particular, the peak of the systolic period Ts cannot be clearly specified in many cases, and the influence of the murmur appears in the subject 3 who is concerned about, for example, heart disease.

  Therefore, in the present embodiment, not the peak of the systole Ts but the peaks of the diastole Td and the double notch Tn are detected. Specifically, the first blood vessel diameter D1 and the second blood vessel diameter D2 are secondarily differentiated at time t, and the accelerations of the respective diameter changes are obtained. Then, the diastolic period Td and the overlapping notch period Tn are detected by finding a peak whose second-order differential value satisfies a predetermined peak condition (for example, exceeding a reference value). According to this method, the diastolic period Td and the double notch period Tn can be reliably found. The second-order differential is an example of a predetermined differential operation.

  The use of the second-order differential value secondarily enhances the robustness of blood vessel diameter measurement. That is, when the direction of the ultrasonic waves sent from the first ultrasonic probe 31 and the second ultrasonic probe 32 (hereinafter referred to as “the sending line”) passes through the center of the cross section of the blood vessel 5 in the short axis direction, it appears on the sending line. Since the change in blood vessel diameter is the largest, the change in blood vessel diameter appears clearly in the waveform. However, if the delivery line deviates from the center of the cross section in the short axis direction, the fluctuation of the blood vessel diameter becomes small, and the waveform becomes blunt. In the configuration in which the diastolic period Td and the overlapping notch period Tn are found from the peak of the blood vessel diameter waveform without performing the differential calculation, the subject 3 moves the body to shift the delivery line to the blood vessel 5, and thus the blood vessel diameter waveform. It becomes difficult to expose the peak of, and the continuous measurement may be interrupted without finding the diastolic period Td and the double notch period Tn. However, if the delivery line does not pass through the center of the cross-section in the short axis direction of the blood vessel 5 when the second differentiation is performed as in this embodiment, the acceleration waveform is clear even if the wall of the blood vessel 5 is captured. Peaks appear. That is, high robustness against the body movement of the subject 3 is obtained. Even if the subject 3 moves his or her body, the possibility that continuous blood pressure measurement will be interrupted is much smaller than in the conventional technique.

  Although it is described that the second order differential is performed as the differential operation, the first stage differential may be performed to detect the diastolic period Td and the overlapping notch period Tn. Even with the first differentiation, the robustness against the body movement of the subject 3 is higher than that in the conventional technique.

  Now, the pulse wave transit time difference Δt is obtained from the difference between the peak times t1 and t2 of the second-order differential values of the first blood vessel diameter D1 and the second blood vessel diameter D2. When the pulse wave transit time difference Δt is obtained, the pulse wave transit velocity PWV is obtained from the pulse wave transit time difference Δt and the inter-probe distance Lp. The calculation of the pulse wave propagation velocity PWV is also performed for the difference between the peak times t3 and t4. The peak times t1 and t2 are times (periods) corresponding to the diastolic period Td, and the peak times t3 and t4 are times corresponding to the overlapping notch period Tn. When the diastolic pulse wave velocity PWVd and the double notch pulse wave velocity PWVn, which are the pulse wave velocity PWV of the diastolic period Td and the double notch period Tn, respectively, are calculated, next, the “vascular elasticity” of the present embodiment is calculated. The index value calculation formula is a blood vessel elasticity index value by substituting the diastolic blood vessel diameter Dd and the overlapping notch blood vessel diameter Dn, and the diastolic pulse wave propagation velocity PWVd and the overlapping notch pulse wave propagation velocity PWVn. Determine the stiffness parameter β.

  After obtaining the stiffness parameter β, the blood pressure P is obtained based on the pulse wave velocity PWV using the “blood pressure calculation formula” of this embodiment.

Next, the “blood pressure calculation formula” and the “vascular elasticity index value calculation formula” of the present embodiment will be described.
First, it is known that the blood vessel blood pressure characteristic in the non-pressurized state has a non-linear characteristic as shown in FIG. 4, for example. Between the measured blood pressure P, the systolic blood pressure Ps, the diastolic blood pressure Pd, the measured blood vessel diameter D, the systolic blood vessel diameter Ds, the diastolic blood vessel diameter Dd, and the stiffness parameter β, the relationships of the equations (1) and (2) are given. There is.

Equations (1) and (2) are conventional equations for blood pressure calculation and calibration of the stiffness parameter β disclosed in the above-mentioned Patent Document 1.
When the blood pressure is calculated using the formula (1), the measured value of the blood vessel diameter D acts as an exponent (also referred to as a power), so that a small measurement error of the blood vessel diameter D is measured. The blood pressure P value is greatly affected. Therefore, the robustness against the body movement of the subject is inferior, and therefore the formula (1) is not suitable for continuous measurement for each beat (constant measurement). Further, since the formula (2) is a formula for calibrating the stiffness parameter β by obtaining a more accurate blood pressure in advance with a pressurization type sphygmomanometer such as a cuff type sphygmomanometer, there is the problem as described above, and the present embodiment Can not be adopted in.

Now, as the relationship between the pulse wave velocity PWV and the blood vessel elasticity, the equation (3), which is the equation of Mains-Cortebake, is known. However, the wall thickness h of the blood vessel, the blood vessel radius r, the blood density ρ, and the incremental elastic coefficient Einc. The incremental elastic modulus Einc is expressed by the equation (4).

Here, by substituting equation (4) into equation (3) and rearranging, equation (5) is obtained.

Further, when the equation (1) is differentiated by D and rearranged, the equation (6) is obtained.

式（８）において血液密度ρの変化は極めて小さいため、定数として扱うことができる。 Then, when the expression (6) is substituted into the expression (5), the expression (7) is obtained. By modifying the expression, the expression (8) which is the “blood pressure calculation expression” of the present embodiment is obtained. The “blood pressure calculation formula” of the present embodiment is a formula showing the relationship among the stiffness parameter β, the blood vessel diameter D, and the pulse wave velocity PWV.

Since the change in the blood density ρ is extremely small in the equation (8), it can be treated as a constant.

Next, the “vascular elasticity index value calculation formula” of this embodiment will be described.
If the blood vessel diameter D ₁ and the pulse wave propagation velocity PWV ₁ at a certain first time T1 and the blood vessel diameter D ₂ and the pulse wave propagation velocity PWV ₂ at the second time T2 can be obtained, these values Substituting into equation (8), the relational expressions of equations (9) and (10) are obtained.

Here, when Expression (10) is divided by Expression (9), Expression (11) is obtained.

The expression (2) is not limited to the systole / diastole and is established at any time phase. That is, by substituting the equation (11) into the equation (2), the equation (12) is obtained.

  This formula (12) is the “vascular elasticity index value calculation formula” of this embodiment. The “vascular elasticity index value calculation formula” of the present embodiment indicates that the stiffness parameter β can be calculated from the blood vessel diameter D and the pulse wave velocity PWV at two times. Although two timings can be set arbitrarily, in the present embodiment, two timings, that is, a characteristic change portion that clearly appears in the blood vessel diameter waveform, that is, a diastolic time Td and an overlapping notch time Tn are used. That is, the first period T1 is the diastolic period Td, the second period T2 is the double notch period Tn, and the diastolic blood vessel diameter Dd and the double notch period blood vessel diameter Dn are the diastolic pulse wave velocity PWVd and the double notch period. By substituting the pulse wave velocity PWVn into the “vascular elasticity index value calculation formula”, the stiffness parameter β, which is a blood vessel elasticity index value, can be calculated. Of course, the first time period T1 may be the double notch period Tn and the second time period may be the diastolic period Td.

The diastolic period Td and the double notch period Tn can be adopted as the period within the same beat, so that the stiffness parameter β can be continuously measured (constantly measured) for each beat. That is, the blood vessel elasticity index value can be measured every beat under non-pressurization (that is, non-invasive) without using a pressurization blood pressure monitor such as a cuff blood pressure monitor.
This means that the stiffness parameter β of the “blood pressure calculation formula” in the formula (8) can be updated (calibrated) to the latest value every beat.

  Therefore, in the present embodiment, continuous blood pressure measurement (constant measurement) for each beat can be realized under non-pressurization while concurrently performing the process of updating the blood vessel elasticity index value to the latest value. ..

  Moreover, since the blood pressure is measured based on the equation (8), the robustness against the body movement of the subject 3 can be enhanced. That is, in the conventional technique based on the formula (1), the value of the blood vessel diameter D acts as an exponent of power. Therefore, when the subject 3 moves his / her body and an error is mixed in the measurement of the blood vessel diameter D, the influence on the calculated blood pressure value becomes great. On the other hand, in the equation (8) of the present embodiment, the value of the blood vessel diameter D is not used as an exponent of power, nor is it a value to be raised to a power. Therefore, the influence of the measurement error of the blood vessel diameter D on the calculated blood pressure value is much smaller than in the conventional case, and thus the robustness of the subject 3 against body movement can be enhanced.

[Description of functional configuration]
Next, a functional configuration for realizing the present embodiment will be described.
FIG. 5 is a block diagram showing a functional configuration example of the blood pressure measurement device 1 of the present embodiment. The blood pressure measurement device 1 includes a main body device 10 and a probe unit 30, and the main body device 10 includes a processing unit 100, an operation input unit 200, a display unit 400, a sound output unit 430, and a communication unit 450. And a storage unit 500.

  The probe unit 30 has a first ultrasonic probe 31 and a second ultrasonic probe 32. The first ultrasonic probe 31 and the second ultrasonic probe 32 perform transmission and irradiation of ultrasonic waves for ultrasonic measurement and reception of reflected waves thereof based on the transmission control signal output from the processing unit 100. .. For example, it is realized by an ultrasonic vibration element or a driver circuit of the element.

  The processing unit 100 centrally controls the blood pressure measurement device 1 to perform various arithmetic processes related to measurement of biological information of the subject 3. The processing unit 100 includes, for example, a microprocessor such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), and an IC (Integrated Circuit) memory. It is realized by electronic parts. Then, data input / output control is performed with each functional unit, and various arithmetic processes are executed based on a predetermined program or data, an operation input signal from the operation input unit 200, etc. Information (in this embodiment, blood vessel elasticity index value and blood pressure) is calculated.

  The processing unit 100 includes an ultrasonic measurement control unit 102, a blood vessel diameter measurement unit 104, a characteristic period determination unit 106, a heartbeat determination unit 108, a pulse wave velocity measurement unit 110, and a blood vessel elasticity index value calculation unit 122. A blood pressure calculation unit 124, a display information generation unit 132, and a clock unit 134.

  The ultrasonic measurement control unit 102 integrally controls ultrasonic measurement. Specifically, the control of the transmission and reception of ultrasonic waves by the first ultrasonic probe 31 and the second ultrasonic probe 32, the process of amplifying the received signal of the reflected wave and converting it to a digital signal, and the like are performed.

  The blood vessel diameter measurement unit 104 continuously measures the blood vessel diameter of the blood vessel 5 (the brachial artery in this embodiment) based on the received signal of the ultrasonic waves. By this continuous measurement, the time change waveform of the blood vessel diameter can be obtained. In the present embodiment, the first blood vessel diameter D1 is measured from the reception signal of the first ultrasonic probe 31, and the second blood vessel diameter D2 is measured from the reception signal of the second ultrasonic probe 32. In measuring the blood vessel diameter, the front wall 5a and the rear wall 5p of the blood vessel 5 are detected from the received signal (see FIG. 2), and the distance difference from the front wall 5a to the rear wall 5p is obtained. The blood vessel diameter may be measured.

  Further, the characteristic period determination unit 106 determines the first time period and the second time period based on the time change waveform of the blood vessel diameter measured by the blood vessel diameter measurement unit 104. In the present embodiment, the first period is the diastolic period Td and the second period is the overlapping notch period Tn, but it goes without saying that they may be reversed. The characteristic stage determination unit 106 determines a diastole Td and an overlapping notch period Tn corresponding to the first blood vessel diameter D1, and a diastole Td and an overlapping notch period Tn corresponding to the second blood vessel diameter D2. The blood vessel diameter measuring unit 104 identifies the blood vessel diameter in the characteristic period determined by the characteristic period determining unit 106. Specifically, of the changing first blood vessel diameter D1, the diastolic blood vessel diameter Dd corresponding to the diastolic time Td and the overlapping notch stage blood vessel diameter Dn corresponding to the overlapping notch period Tn are specified. Further, of the second blood vessel diameter D2, the diastolic blood vessel diameter Dd corresponding to the diastole and the double notch stage blood vessel diameter Dn corresponding to the double notch stage are specified.

  The characteristic period determination unit 106 performs a predetermined differential operation on the time-varying waveform of the blood vessel diameter to determine the diastolic period Td and the overlapping notch period Tn, which are the characteristic periods of the pulse wave. In the present embodiment, the characteristic stage is determined by performing the second-order differentiation and detecting the time point (time) when the second-order differential value satisfies the peak condition indicating that the peak is equal to or higher than the reference peak.

  The heartbeat determination unit 108 determines a heartbeat segment in the ultrasonic measurement result from the result of the characteristic period determination unit 106. A function for calculating the heart rate may be included.

  The pulse wave velocity measurement unit 110 measures the pulse wave velocity PWV in the blood vessel 5. In the present embodiment, for each of the diastole Td and the overlapping notch stage Tn, the pulse wave propagation time difference Δt in the characteristic period is calculated, and the pulse wave propagation velocity PWV is obtained from the time difference Δt and the inter-probe distance Lp. That is, the diastolic pulse wave velocity PWVd and the double-notch pulse wave velocity PWVn are obtained.

  The blood vessel elasticity index value calculation unit 122 (1) is either the diastolic blood vessel diameter Dd and the overlapping notch blood vessel diameter Dn related to the first blood vessel diameter D1 specified by the blood vessel diameter measurement unit 104, or the second blood vessel diameter D2. The diastolic blood vessel diameter Dd and the double-notch blood vessel diameter Dn, and (2) the diastolic pulse wave velocity PWVd and the double-notch pulse wave velocity PWVn measured by the pulse wave velocity measuring unit 110. , The value of the stiffness parameter β, which is the blood vessel elasticity index value, is obtained.

  The blood pressure calculation unit 124 calculates the blood vessel diameter D measured by the blood vessel diameter measurement unit 104, the pulse wave velocity PWV measured by the pulse wave velocity measurement unit 110, and the stiffness calculated by the blood vessel elasticity index value calculation unit 122. The blood pressure is calculated by performing a predetermined calculation process using the parameter β and the variable. In the present embodiment, the blood pressure is calculated by performing the arithmetic processing according to the equation (8) in which the blood pressure is proportional to the square of the pulse wave propagation velocity and is proportional to the reciprocal of the blood vessel diameter D.

  More specifically, although the diastolic blood pressure Pd and the double-notch blood pressure Pn are obtained using the equation (8), when obtaining the diastolic blood pressure Pd, the blood pressure calculation unit 124 uses the measured diastole. The diastolic blood pressure Pd is obtained by substituting the blood vessel diameter Dd, the diastolic pulse wave velocity PWVd, and the stiffness parameter β into the equation (8). At this time, the value of the measured diastolic blood vessel diameter Dd is substituted for the blood vessel diameter D in the equation (8).

  When obtaining the double-notch blood pressure Pn, the blood pressure calculator 124 measures the measured double-notch blood vessel diameter Dn, the double-notch pulse wave velocity PWVn, the stiffness parameter β, and the diastolic blood vessel diameter Dd. By substituting into the equation (8), the double-notch stage blood pressure Pn is obtained. At this time, the value of the measured overlapping notch stage blood vessel diameter Dn is substituted for the blood vessel diameter D in the equation (8).

  The value to be substituted for the blood vessel diameter D in the equation (8) may be either the first blood vessel diameter D1 or the second blood vessel diameter D2.

  In the present embodiment, the stiffness parameter β included in the equation (8) is used as a variable that is a value calculated by the blood vessel elasticity index value calculation unit 122, and is updated to the latest value for each beat. However, the update interval may be set to a predetermined number of beats (for example, 100 beats) or a predetermined time (for example, 10 minutes) instead of every beat, and the update interval may be treated as a constant.

  Further, the blood pressure calculation unit 124 causes the blood vessel diameter measurement unit 104 to specify the systolic blood vessel diameter Ds which is the systolic blood vessel diameter D, and substitutes this systolic blood vessel diameter Ds into the equation (1) to obtain the systolic blood pressure. Find Ps. However, the diastolic blood vessel diameter Dd and the diastolic blood pressure Pd in the equation (1) used at this time are determined by using the diastolic blood vessel diameter Dd and the equation (8) substituted into the above equation (8). Pd can be used.

  It should be noted that, instead of the diastolic blood vessel diameter Dd and the diastolic blood pressure Pd in the formula (1), the double notch blood vessel diameter Dn and the double notch blood pressure Pn may be used.

  Alternatively, the systolic blood pressure Ps may be obtained using another method. For example, the systolic blood pressure Ps is calculated by performing a predetermined systolic blood pressure estimation calculation using the diastolic blood pressure Pd and the double notch blood pressure Pn. Specifically, the double notch blood pressure Pn is regarded as the mean arterial pressure, and the systolic blood pressure Ps is obtained from the diastolic blood pressure Pd and the double notch blood pressure Pn.

  The display information generation unit 132 generates images for displaying various operation screens and measurement results necessary for blood pressure measurement, and outputs the images to the display unit 400. The display unit 400 is a device that displays the image data from the display information generation unit 132.

  The timer unit 134 measures the measurement time. The time counting method can be selected as appropriate, but for example, the system clock can be used.

  The operation input unit 200 receives various operation inputs from the user and outputs an operation input signal corresponding to the operation input to the processing unit 100. The operation input unit 200 includes a button switch, a lever switch, a dial switch, a track pad, a mouse, a touch panel, and the like.

  The sound output unit 430 is a device that emits a sound based on the audio signal output from the processing unit 100, and is a speaker. It is preferable to generate a notification sound when the blood pressure reaches a predetermined abnormal value.

  The communication unit 450 is a communication device for communicating with an external device of the blood pressure measurement device 1. The communication may be wired or wireless. Various measurement data can be transmitted to an external device.

  The storage unit 500 is realized by a storage medium such as an IC memory, a hard disk, and an optical disk, and stores various programs and various data such as data of the calculation process of the processing unit 100. Note that the processing unit 100 and the storage unit 500 may be provided separately, and may be connected by communication via a communication line such as a LAN (Local Area Network) or the Internet. For example, in that case, the storage unit 500 can also be realized as a storage device of a server connected to the Internet.

  The storage unit 500 stores the blood pressure measurement program 510, blood vessel diameter log data 520, intermediate data 530, blood vessel elasticity index value log data 550, and blood pressure log data 560. Of course, in addition to these, flags for various determinations, counter values for timing, and the like can be stored as appropriate.

  The blood pressure measurement program 510 is executed by the processing unit 100 so that the ultrasonic measurement control unit 102, the blood vessel diameter measurement unit 104, the characteristic period determination unit 106, the heartbeat determination unit 108, the pulse wave velocity measurement unit 110, the blood vessel elasticity index. The functions of the value calculation unit 122, the blood pressure calculation unit 124, the display information generation unit 132, the clock unit 134, etc. are realized. Note that any of these functional units can be realized by hardware such as an electronic circuit.

  Further, the blood pressure measurement program 510 includes, as a subroutine program, a blood vessel elasticity index value measurement program 512 for realizing a blood vessel elasticity index value measurement method for measuring a blood vessel elasticity index value.

  The blood vessel diameter log data 520 is various data relating to the blood vessel diameter of the blood vessel 5 obtained by transmitting the ultrasonic wave and receiving the reflected wave by the probe unit 30 continuously performed at extremely short time intervals from the start to the end of the measurement. To store. Specifically, as shown in FIG. 6, in association with the measurement time 521 in each ultrasonic measurement cycle, a beat number 522 (for example, the number of beats from the start of measurement is used to identify the beat at that time. A value indicating whether or not it is dynamic), the first blood vessel diameter 523 and the second blood vessel diameter 524 measured at that time, the first blood vessel diameter second-order differential value 525, and the second blood vessel diameter second-order differential value 526 are stored. .. Of course, data other than these can also be stored as appropriate. In FIG. 6, the measurement time 521 gradually elapses to “t001”, “t002”, “t003”, “t004”, but since the beat number 522 is “1”, the same beat It indicates that the data is related to. By observing the first blood vessel diameter 523 and the second blood vessel diameter 524 in time series, a temporal change waveform of the blood vessel diameter can be obtained. Further, at “t001” and “t002”, the first blood vessel diameter second-order differential value 525 and the second blood vessel diameter second-order differential value 526 are “NULL” because the data is before time “t001”. This is because the data necessary for calculating the second derivative is not obtained.

  The pulsation number 522 is stored based on the determination of the heartbeat by the heartbeat determining unit 108, and the first blood vessel diameter 523 and the second blood vessel diameter 524 store the measurement results of the blood vessel diameter measuring unit 104. The first blood vessel diameter second-order differential value 525 and the second blood vessel diameter second-order differential value 526 are values calculated when the characteristic period determination unit 106 determines the characteristic period.

  The intermediate data 530 stores data relating to the characteristic period determined by the characteristic period determination unit 106. Specifically, as shown in FIG. 7, in association with the pulsation number 531 corresponding to the pulsation number 522 of the blood vessel diameter log data 520, the diastolic blood vessel diameter 541a relating to the first blood vessel diameter D1 in the pulsation is associated. And a double-notch stage blood vessel diameter 541b, a diastolic blood vessel diameter 542a and a double-notch stage blood vessel diameter 542b related to the second blood vessel diameter D2, a diastolic pulse wave velocity 543a, and a double-notch pulse wave velocity 543b. And are stored.

  The diastolic blood vessel diameter 541a and the overlapping notch blood vessel diameter 541b related to the first blood vessel diameter D1, and the diastolic blood vessel diameter 542a and the duplication notch blood vessel diameter 542b related to the second blood vessel diameter D2 are the blood vessel diameter measuring unit 104. The blood vessel diameter of the characteristic period specified by is stored. The diastolic pulse wave velocity 543a and the double-notch pulse wave velocity 543b store the pulse wave velocity calculated by the pulse wave velocity measuring unit 110.

  As shown in FIG. 8, the blood vessel elasticity index value log data 550 includes the blood vessel elasticity index value 552 calculated by the blood vessel elasticity index value calculation unit 122 (the stiffness parameter β value in this embodiment) as the blood vessel diameter log data 520. It is stored in association with the beat number 551 corresponding to the beat number 522. That is, the blood vessel elasticity index value 552 for each beat is stored.

  In the blood pressure log data 560, as shown in FIG. 9, the diastolic blood pressure 562, the systolic blood pressure 563, and the double notch blood pressure 564 calculated by the blood pressure calculation unit 124 are assigned to the pulsation number 522 of the blood vessel diameter log data 520. It is stored in association with the corresponding beat number 561. That is, the blood pressure for each beat is stored.

[Explanation of processing flow]
Next, the operation of the blood pressure measurement device 1 will be described.
FIG. 10 is a flowchart for explaining a main processing flow in the blood pressure measurement device 1 according to the present embodiment, and shows a processing flow realized by executing the blood pressure measurement program 510. The first ultrasonic probe 31 and the second ultrasonic probe 32 are preliminarily attached to predetermined positions of the subject 3.

  First, the processing unit 100 starts ultrasonic measurement using the probe unit 30 and starts measurement and recording of the blood vessel diameter D (step S2). Further, the calculation and recording of the second-order differential value of the blood vessel diameter D depending on time are started (step S4). Data is stored in the blood vessel diameter log data 520 through steps S2 and S4.

  Further, the processing unit 100 determines a heartbeat segment based on the variation of the blood vessel diameter D, and starts the heartbeat determination (step S6). The determined heartbeat identification information is stored in the pulsation number 522 of the blood vessel diameter log data 520 as the heartbeat number from the start of measurement.

Next, the processing unit 100 performs pulse wave velocity measurement processing (step S8).
FIG. 11 is a flowchart for explaining the flow of pulse wave velocity measurement processing in this embodiment.
In the pulse wave velocity measurement process, the processing unit 100 determines the diastole related to the first blood vessel diameter D1 and the diastole related to the second blood vessel diameter D2 based on the blood vessel diameter log data 520 (step S10). S12). In addition, the blood vessel diameter in this diastole is specified. Then, the time difference between these two diastoles, that is, the diastolic pulse wave transit time Δtd is obtained, and the diastolic pulse wave velocity PWVd is calculated from the diastolic pulse wave transit time Δtd and the inter-probe distance Lp known in advance. (Step S14).

Subsequently, the processing unit 100 determines, based on the blood vessel diameter log data 520, an overlapping notch period related to the first blood vessel diameter D1 and an overlapping notch period related to the second blood vessel diameter D2 (steps S16 to S18). ). In addition, the diameter of the blood vessel at this double notch stage is specified. Then, the time difference between these two overlapping notch periods, that is, the overlapping notch period pulse wave propagation time Δtn is obtained, and the overlapping notch period is calculated from the overlapping notch period pulse wave propagation time Δtn and the inter-probe distance Lp known in advance. The pulse wave velocity PWVn is calculated (step S20). Each data calculated in the pulse wave velocity measurement process is stored in the intermediate data 530.
This completes the pulse wave velocity measurement process and returns to FIG.

Next, the processing unit 100 causes the diastolic blood vessel diameter Dd and the overlapping notch blood vessel diameter Dn (the blood vessel diameter of the first blood vessel diameter D1 and the blood vessel of the second blood vessel diameter D2) calculated in the preceding pulse wave velocity measurement processing. Diameter), the diastolic pulse wave velocity PWVd and the double notch pulse wave velocity PWVn are used to calculate the value of the stiffness parameter β, which is the vascular elasticity index value, from the equation (12) (step S30). The calculated value of the stiffness parameter β is stored in the blood vessel elasticity index value log data 550.
The processing of steps S8 to S30 is processing related to the blood vessel elasticity index value measurement program 512 for realizing the blood vessel elasticity index value measurement method.

Then, the processing unit 100 performs blood pressure calculation processing (step S40).
FIG. 12 is a flowchart for explaining the flow of blood pressure calculation processing in this embodiment.
The processing unit 100 uses the stiffness parameter β calculated in step S30, the diastolic blood vessel diameter Dd determined in step S10 (or step S12), and the diastolic pulse wave velocity PWVd calculated in step S14. Then, the diastolic blood pressure Pd is calculated from the equation (8) (step S42). The diastolic blood vessel diameter Dd is substituted for the blood vessel diameter D which is a variable of the blood pressure calculation equation of the equation (8).

  The processing unit 100 also determines the stiffness parameter β calculated in step S30, the diastolic blood vessel diameter Dd determined in step S10 (or step S12), and the overlapping notch determined in step S16 (or step S18). Using the period blood vessel diameter Dn and the double-notch pulse wave velocity PWVn calculated in step S20, the double-notch blood pressure Pn is calculated from the equation (8) (step S44). The blood vessel diameter D, which is a variable of the blood pressure calculation equation of the equation (8), is substituted with the blood vessel diameter Dn at the double notch stage.

  Further, the processing unit 100 calculates the systolic blood pressure Ps (step S46). The systolic blood pressure Ps is calculated, for example, based on the blood vessel diameter log data 520, the systolic period is determined from the data of the pulsation number 522 that is currently measured, and the systolic blood vessel diameter Ds is specified. The systolic blood pressure Ps can be obtained by substituting the systolic blood vessel diameter Ds into the equation (1). Alternatively, the double-notch blood pressure Pn obtained in step S44 may be regarded as the mean arterial pressure, and the double-notch blood pressure Pn and the diastolic blood pressure Pd or the systolic blood pressure Ps obtained in step S42 may be obtained. ..

  The processing unit 100 stores the diastolic blood pressure Pd, the double-notch blood pressure Pn, and the systolic blood pressure Ps obtained in steps S42 to S46 in the blood pressure log data 560 and causes the display unit 400 to display them (step S48). At this time, information such as the heart rate, blood vessel diameter, and blood vessel elasticity index value may be displayed together. Further, the display of the double-notch stage blood pressure Pn may be omitted.

  Returning to FIG. 10, the processing unit 100 repeatedly executes the processing of steps S8 to S60 for each heartbeat until the blood pressure measurement is completed.

  As described above, according to the present embodiment, the vascular elasticity index value is obtained by using the diastolic pulse wave velocity PWVd and the double notch pulse wave velocity PWVn, and the diastolic blood vessel diameter Dd and the double notch blood vessel diameter Dn. Can be calculated. Since the diastolic pulse wave velocity PWVd, the double notch pulse wave velocity PWVn, the diastolic blood vessel diameter Dd, and the double notch blood vessel diameter Dn can all be measured under non-pressurization, Measurement of the vascular elasticity index value can be realized.

  The form to which the present invention can be applied is not limited to the above-described embodiment, and appropriate addition, omission, and change of the constituent elements can be made.

(A)
For example, although the blood pressure measurement device 1 has been described as being also a blood vessel elasticity index value measurement device, it may be configured as a dedicated device for measuring a blood vessel elasticity index value without measuring blood pressure. In that case, the function of the blood pressure calculation unit 124 in the functional configuration diagram of FIG. 5 may be deleted.

(B)
The pulse wave propagation velocity PWV is said to be about 10 times the blood flow velocity V, but the influence of the blood flow velocity V on the pulse wave propagation velocity PWV depends on the difference in the blood vessels to be measured, the measurement position, and the degree of elasticity of the blood vessels. Can reach. That is, the blood flow velocity V affects the pulse wave propagation velocity PWV used in the equation (8) which is the “blood pressure calculation equation” and the equation (12) which is the “vascular elasticity index value calculation equation” in the above-described embodiment. There is a case.

Therefore, instead of the pulse wave velocity PWV, the equation (13) defining the “blood pressure calculation equation” using the velocity obtained by subtracting the blood flow velocity V from the pulse wave velocity PWV and the “vascular elasticity index value calculation equation” It has been found that it may be better to adopt the equation (14) that defines That is, the blood vessel diameter D ₁ and the pulse wave propagation velocity PWV ₁ and the blood flow velocity V _{1 at} a certain first time T ₁ , and the blood vessel diameter D ₂ and the pulse wave propagation velocity PWV ₂ and the blood flow at the second time T _2. When the velocity V ₂ can be obtained, by substituting these values into the equation (14), the stiffness parameter β which is the blood vessel elasticity index value can be calculated.

A modified example in this case will be described with reference to FIGS. The same components and the same processing steps as those in the above-described embodiment are designated by the same reference numerals.
FIG. 13 is a diagram showing a configuration example of the probe unit 300 in this modification. It is shown as a diagram corresponding to FIG. The probe unit 300 includes a third ultrasonic probe 33 for measuring the blood flow velocity V of the blood flowing in the blood vessel 5 between the first ultrasonic probe 31 and the second ultrasonic probe 32. The blood flow velocity V can be measured, for example, by using the ultrasonic Doppler method.

  FIG. 14 is a block diagram showing a functional configuration example of the blood pressure measurement device 2 according to the present modification. The main body device 12 has a configuration in which the processing unit 100 further includes a blood flow velocity measurement unit 112. In the blood pressure measurement device 2, the ultrasonic measurement control unit 102 controls the transmission and reception of ultrasonic waves by the third ultrasonic probe 33 in addition to the first ultrasonic probe 31 and the second ultrasonic probe 32. The blood flow velocity measurement unit 112 uses the ultrasonic Doppler method to perform blood flow based on the frequency of the ultrasonic waves transmitted from the third ultrasonic probe 33 and the frequency of the received ultrasonic waves under the control of the ultrasonic measurement control unit 102. Measure the velocity V. The blood flow velocity V is measured at the same timing as the blood vessel diameter measurement time 521 (see FIG. 6), and is stored in the blood flow velocity log data 529 as the blood flow velocity V at each measurement time.

  Further, the blood flow velocity V related to the characteristic period determined by the characteristic period determination unit 106 is selected from the blood flow velocity log data 529 and stored in the intermediate data 532. FIG. 15 is a diagram showing an example of the data structure of the intermediate data 532. In addition to the data structure of the intermediate data 530 (see FIG. 7) of the above-described embodiment, the diastolic blood flow velocity 544a and the duplication notch are set as the blood flow velocity V in the diastole and duplication notch which is an example of the characteristic period. The period blood flow velocity 544b is stored in the intermediate data 532 for each beat in association with the beat number 531.

FIG. 16 is a flowchart for explaining the flow of main processing executed by the blood pressure measurement device 2. Instead of step S2 of the flowchart shown in FIG. 10, measurement and recording of the blood vessel diameter and the blood flow velocity V are started (step S3).
Further, in the calculation of the blood vessel elasticity index value in step S30, the blood vessel elasticity index value is calculated using the equation (14). That is, if the first time period T1 is the diastolic period Td and the second time period T2 is the overlapping notch period Tn, the diastolic pulse wave velocity is used instead of the diastolic pulse wave velocity PWVd (which can be called the first pulse wave velocity). The wave propagation velocity PWVd minus the diastolic blood flow velocity Vd is used, and the double notch pulse wave velocity PWVn is used instead of the double notch pulse wave velocity PWVn (which can be called the second pulse wave velocity). The stiffness parameter β, which is the vascular elasticity index value, is calculated by using the velocity obtained by subtracting the blood flow velocity Vn in the double notch stage from (step S30). By doing so, in calculating the blood vessel elasticity index value, when the blood flow velocity affects the pulse wave propagation velocity, the influence can be reduced.

FIG. 17 is a flowchart for explaining the flow of blood pressure calculation processing executed by blood pressure measurement device 2. Steps S42 and S44 of the flowchart shown in FIG. 12 are replaced with steps S43 and S45, respectively.
That is, in step S43, the stiffness parameter β calculated in step S30, the diastolic blood vessel diameter Dd determined in step S10 (or step S12), and the diastolic pulse wave velocity PWVd calculated in step S14 are expanded. The diastolic blood pressure Pd is calculated using the velocity obtained by subtracting the in-phase blood flow velocity Vd (step S43). The calculation formula used at this time is formula (13).

  In step S45, the stiffness parameter β calculated in step S30, the diastolic blood vessel diameter Dd determined in step S10 (or step S12), and the double notch stage determined in step S16 (or step S18). The double nick blood pressure Pn is calculated using the blood vessel diameter Dn and the speed obtained by subtracting the double nick blood flow velocity Vn from the double nick pulse wave velocity PWVn calculated in step S20 (step S45). ). The calculation formula used at this time is also the formula (13).

  The expression (13) is, so to speak, proportional to the square of the velocity obtained by subtracting the blood flow velocity V from the pulse wave velocity PWV, and is also proportional to the reciprocal of the blood vessel diameter D. It is a formula to calculate. By doing so, it is possible to reduce the influence of the blood flow velocity on the pulse wave velocity when the blood pressure is calculated.

  3 ... Subject, 5 ... Blood vessel, 1 ... Blood pressure measuring device, 10 ... Main body part, 30 ... Probe part, 31 ... First ultrasonic probe, 32 ... Second ultrasonic probe, 100 ... Processing part, 102 ... Ultra Sound wave measurement control unit, 104 ... Blood vessel diameter measurement unit, 106 ... Characteristic period determination unit, 108 ... Heartbeat determination unit, 110 ... Pulse wave propagation velocity measurement unit, 122 ... Blood vessel elasticity index value calculation unit, 124 ... Blood pressure calculation unit

Claims (11)

Using the measurement result obtained by measuring the blood vessel diameter at the first position of the artery and the measurement result obtained by measuring the blood vessel diameter at the second position of the artery, which is a characteristic period of the blood vessel diameter variation of the artery with pulsation. A pulse wave velocity measuring unit for measuring a first pulse wave velocity at one time and a second pulse wave velocity at a second time;
A vascular elasticity index value of the artery is calculated using the first pulse wave velocity, the second pulse wave velocity, and the blood vessel diameter at the first position at each of the first time period and the second time period. A vascular elasticity index value calculation unit,
A blood vessel elasticity index value measuring device comprising: The pulse wave velocity measuring section measures the first pulse wave velocity and the second pulse wave velocity with the first time period and the second time period as different times within the same beat,
The blood vessel elasticity index value measuring device according to claim 1. The pulse wave velocity measuring section calculates the first pulse wave velocity and the second pulse wave velocity by performing a predetermined statistical calculation process on the pulse wave velocity between a plurality of beats.
The blood vessel elasticity index value measuring device according to claim 1. The pulse wave velocity measuring unit sets the first pulse wave velocity and the second pulse wave velocity as one of the first period and the second period as a diastole and the other as a double notch period. To measure,
The blood vessel elasticity index value measuring device according to any one of claims 1 to 3. The pulse wave velocity measuring section measures the first pulse wave velocity and the second pulse wave velocity for each heartbeat,
The blood vessel elasticity index value calculation unit calculates the blood vessel elasticity index value for each heartbeat,
The blood vessel elasticity index value measuring device according to any one of claims 1 to 4. The blood vessel elasticity index value calculation unit is characterized in that blood pressure is not used in the calculation of the blood vessel elasticity index value.
The blood vessel elasticity index value measuring device according to any one of claims 1 to 5. A blood flow velocity measuring unit for measuring a first blood flow velocity of the first stage and a second blood flow velocity of the second stage of the artery,
Further equipped with,
The blood vessel elasticity index value calculation unit may calculate a velocity obtained by subtracting the first blood flow velocity from the first pulse wave velocity instead of the first pulse wave velocity, and the second pulse wave velocity instead of the second pulse wave velocity. 2. A vascular elasticity index value of the artery is calculated using a velocity obtained by subtracting the second blood flow velocity from the pulse wave velocity.
The blood vessel elasticity index value measuring device according to any one of claims 1 to 6. A blood vessel elasticity index value measuring device according to any one of claims 1 to 6,
A blood vessel elasticity index value calculated by the blood vessel elasticity index value measuring device, and using the measurement result of measuring the blood vessel diameter of the artery, a blood pressure calculation unit for calculating blood pressure,
Blood pressure measurement device. The blood pressure calculation unit performs the predetermined arithmetic processing in which the blood pressure is proportional to the square of the pulse wave velocity measured by the pulse wave velocity measuring unit, and is proportional to the reciprocal of the blood vessel diameter. Calculate blood pressure,
The blood pressure measurement device according to claim 8. A blood vessel elasticity index value measuring device according to claim 7;
Using the blood vessel elasticity index value calculated by the blood vessel elasticity index value measuring device and the measurement result obtained by measuring the blood vessel diameter of the artery, the blood is calculated from the pulse wave velocity measured by the pulse wave velocity measuring unit. A blood pressure calculation unit that calculates blood pressure by performing a predetermined calculation process that is proportional to the square of the velocity obtained by subtracting the blood flow velocity measured by the flow velocity measurement unit, and that is proportional to the reciprocal of the blood vessel diameter;
Blood pressure measurement device. The arithmetic processing unit built into the arithmetic unit
Using the measurement result obtained by measuring the blood vessel diameter at the first position of the artery and the measurement result obtained by measuring the blood vessel diameter at the second position of the artery, which is a characteristic period of the blood vessel diameter variation of the artery with pulsation. Measuring the first pulse wave velocity of the first period and the second pulse wave velocity of the second period;
A vascular elasticity index value of the artery is calculated using the first pulse wave velocity, the second pulse wave velocity, and the blood vessel diameter at the first position at each of the first time period and the second time period. That
A method for measuring a vascular elasticity index value for executing the method.

Images