JP2017127494A - Blood vessel elasticity index value measuring device, blood pressure measuring device, and blood vessel elasticity index value measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blood vessel elasticity index value measuring device allowing a highly accurate blood vessel elasticity index value to be measured with a reduction in oppression feeling.SOLUTION: A blood vessel elasticity index value measuring device 1 comprises: a cuff 20; a probe section 30 having a first ultrasonic sensor 31; and a main body device 10 having a first blood vessel elastic index value calculation section. The cuff 20 is mounted onto a prescribed portion of an examinee 3 where a blood vessel 5 being an artery runs, and can tighten the prescribed portion by a cuff pressure. The first ultrasonic sensor 31 percutaneously measures a blood vessel diameter of the blood vessel 5 in the prescribed portion tightened by the cuff 20. The first blood vessel elastic index value calculation section calculates a blood vessel elasticity index value of the blood vessel by using correspondence between the cuff pressure and the blood vessel diameter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vascular elasticity index value measuring apparatus for measuring a vascular elasticity index value of an artery.

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

JP 2004-41382 A

  In blood pressure measurement, there is a desire to accurately measure blood pressure even with non-invasive measurement, and accurate blood pressure measurement is to be realized as continuous measurement for each beat (also called constant measurement or constant measurement). There is a request. 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-precision constant measurement of blood pressure can be realized. However, the practical application of constant measurement of blood pressure is not so simple.

  One of the causes of difficulty in practical use is the vascular elasticity index value. For example, in the blood pressure measurement method using the stiffness parameter β that 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 sphygmomanometer. In this calibration process, it is possible to adopt the Korotkoff method or the oscillometric method, which are highly reliable blood pressure measurement methods. After the calibration process, the stiffness parameter β calibrated in advance can be used as a fixed value while the blood pressure is measured without pressure.

  However, since the hardness (elasticity) of the blood vessel changes due to the action of the autonomic nerve or the like, in the conventional method in which the blood vessel elasticity index value must be a fixed value, blood pressure measurement accuracy decreases. That is, as the time elapses from the calibration of the vascular elasticity index value, the reliability of the measured blood pressure value can be reduced. Therefore, there is a limit to the time that can guarantee the accuracy of constant measurement.

  However, this is also a problem when the calibration process is frequently performed by shortening the time interval of the calibration process. In principle, the Korotkoff method and the oscillometric method require pressurization control that pressurizes the measurement site with a pressure exceeding the systolic blood pressure, closes the blood vessel and interrupts the blood flow, and then gradually flows the blood flow. Therefore, there is a strong feeling of pressure over a certain amount of time. For this reason, if the calibration process during the continuous measurement is repeated, the subject who was expecting the non-invasive continuous measurement is given a heavy pressure, which may cause a burden on the subject. For example, if the calibration process is activated during bedtime, bedtime may be hindered by a strong sense of pressure, and the user may be awakened.

  The present invention has been devised in order to solve the above-described problems, and the object of the present invention is to propose a technique that enables highly accurate measurement of a vascular elasticity index value with a reduced feeling of pressure. is there.

  According to a first aspect of the present invention, there is provided a compression band that is attached to a predetermined part of a subject on which an artery runs and can tighten the predetermined part by cuff pressure, and the predetermined part that is tightened by the compression band. A first vascular elasticity index value of the artery is calculated using a first ultrasonic sensor for percutaneously measuring the vascular diameter of the artery at a site and a correspondence relationship between the cuff pressure and the vascular diameter. And a first vascular elasticity index value calculating unit.

  According to the first aspect of the invention, the predetermined region is tightened by the cuff pressure of the compression band attached to the predetermined region, and the vascular elasticity index value is measured, but is measured percutaneously by the ultrasonic sensor. Since the blood vessel elasticity index value is calculated using the correspondence relationship between the blood vessel diameter and the cuff pressure, a cuff pressure enough to interrupt the blood flow is not required. Moreover, since the fluctuation range of the blood vessel diameter accompanying pulsation increases by tightening with the cuff pressure, the measurement accuracy of the blood vessel elasticity index value can be improved from the blood vessel diameter blood pressure characteristics. Therefore, highly accurate measurement of the vascular elasticity index value with a reduced feeling of pressure can be realized.

  In a second aspect based on the first aspect, the first vascular elasticity index value calculation unit calculates the first vascular elasticity index value using the correspondence relationship at different cuff pressures. It is a blood vessel elasticity index value measuring apparatus.

  According to the second aspect of the present invention, the blood vessel elasticity index value can be calculated using the correspondence between the cuff pressure and the blood vessel diameter at different cuff pressures.

  According to a third aspect of the present invention, in the first or second aspect, the first vascular elasticity index value calculator calculates the correspondence between the vascular diameter and the cuff pressure according to a predetermined characteristic period in one cardiac cycle. The blood vessel elasticity index value measuring apparatus calculates the first blood vessel elasticity index value using a relationship.

  According to the third aspect of the invention, for example, the blood vessel elasticity index value can be calculated using the correspondence relationship between the blood vessel diameter and the cuff pressure in the characteristic period in one cardiac cycle such as systole, diastole, and double notch. it can.

  According to a fourth invention, in any one of the first to third inventions, the first vascular elasticity index value calculation unit includes at least three or more cuff pressures or different timings during one cardiac cycle. The vascular elasticity index value measuring apparatus calculates the first vascular elasticity index value using the correspondence relationship.

  According to the fourth aspect of the invention, as a correspondence relationship between the cuff pressure and the blood vessel diameter, the vascular elasticity index value is calculated using at least three correspondence relationships having different cuff pressures or timings during one cardiac cycle. Can do.

  In addition, in a fifth aspect based on any one of the first to fourth aspects, the first vascular elasticity index value calculation unit uses the correspondence relationship in which the cuff pressure is 90 mmHg or less. It is a vascular elasticity index value measuring device for calculating a first vascular elasticity index value.

  According to the fifth aspect of the invention, the cuff pressure when calculating the blood vessel elasticity index value is 90 [mmHg] or less. Since this cuff pressure is less than or equal to the upper limit of the normal value range of diastolic blood pressure, it does not give the subject a feeling of pressure like blood pressure measurement by the Korotkoff method or oscillometric method.

  The sixth invention provides the vascular elasticity index value measuring apparatus according to any one of the first to fifth inventions, the first vascular elasticity index value measured by the vascular elasticity index value measuring apparatus, and the vascular diameter. And a blood pressure calculation unit that calculates blood pressure using the blood pressure measurement device.

  According to the sixth aspect of the present invention, the vascular elasticity index value measured by the vascular elasticity index value measuring apparatus according to any one of the first to fifth aspects, and the vascular diameter based on the measurement result of the first ultrasonic sensor, It is possible to realize continuous blood pressure measurement (constant measurement) for each beat using the.

  The seventh invention further comprises a calibration determination unit for determining whether or not to calibrate the first vascular elasticity index value in the sixth invention, and when the determination by the calibration determination unit is affirmative, The blood pressure measurement device that causes the blood vessel elasticity index value measurement device to measure the first blood vessel elasticity index value, and wherein the blood pressure calculation unit calculates blood pressure using the latest calibrated first blood vessel elasticity index value. It is.

  According to the seventh aspect, when it is determined that the vascular elasticity index value needs to be calibrated during continuous blood pressure measurement (always measuring) for each beat using the vascular elasticity index value. The measurement of the vascular elasticity index value is performed by the vascular elasticity index value measuring device according to any one of the first to fifth inventions. For this reason, it is possible to reduce the feeling of pressure and pressure given to the subject with respect to the calibration process during the continuous measurement.

  The eighth invention is the blood pressure measurement device according to the seventh invention, wherein the calibration determination unit determines to calibrate when the blood pressure calculated by the blood pressure calculation unit satisfies a predetermined abnormal value condition. .

  According to the eighth aspect, it is possible to determine whether or not a calibration process is necessary based on the calculated blood pressure value.

  According to a ninth invention, in the seventh invention, the second ultrasonic sensor for measuring the blood vessel diameter of the artery percutaneously at a position different from the measurement position by the first ultrasonic sensor; The first pulse wave velocity of the first period and the second period of the second period, which are characteristic periods of the arterial blood vessel diameter variation accompanying pulsation, using the measurement results of the first and second ultrasonic sensors. A pulse wave velocity is measured, and the first pulse wave velocity, the second pulse wave velocity, and the blood vessel diameter at each of the first time period and the second time period A second vascular elasticity index value measuring unit for measuring a vascular elasticity index value, wherein the calibration determination unit is configured to measure the first vascular elasticity index value measured by the vascular elasticity index value measuring device; Second vascular elasticity measured by the vascular elasticity index value measuring unit 2 By comparing the target value, it determines whether to calibrate a blood pressure measurement device.

  According to the ninth aspect of the invention, the first pulse wave velocity of the first period, the second pulse wave velocity of the second period, which is the characteristic period of the blood vessel diameter fluctuation accompanying pulsation, the first period, The second blood vessel elasticity index value can be calculated using the blood vessel diameters of the second period. Since any of the first pulse wave propagation speed, the second pulse wave propagation speed, and the blood vessel diameter can be measured under non-pressurization, measurement of the vascular elasticity index value under non-pressurization can be realized. Based on the second vascular elasticity index value, it can be determined whether or not the vascular elasticity index value needs to be calibrated.

  The tenth aspect of the present invention further includes a blood flow velocity measuring unit that measures the first blood flow velocity at the first time and the second blood flow velocity at the second time of the artery, and the second blood vessel An elasticity index value measuring unit is a speed obtained by subtracting the first blood flow velocity from the first pulse wave propagation velocity instead of the first pulse wave propagation velocity, and the second pulse wave instead of the second pulse wave propagation velocity. The blood pressure measurement device according to a ninth aspect of the present invention measures the second vascular elasticity index value using a velocity obtained by subtracting the second blood flow velocity from a wave propagation velocity.

  According to the tenth aspect, when the second blood vessel elasticity index value is measured, when the influence of the blood flow velocity appears on the pulse wave propagation velocity, the influence can be reduced.

  In the eleventh aspect of the invention, the blood pressure calculation unit is measured by the blood flow velocity measurement unit from the first pulse wave propagation velocity using the first blood vessel elasticity index value and the blood vessel diameter. The blood pressure measurement device according to the tenth aspect of the present invention calculates a blood pressure by performing a predetermined calculation process proportional to the square of the velocity obtained by subtracting the blood flow velocity and proportional to the reciprocal of the blood vessel diameter.

  According to the eleventh aspect, the blood pressure is calculated by performing a predetermined calculation process proportional to the square of the velocity obtained by subtracting the blood flow velocity from the first pulse wave propagation velocity and proportional to the reciprocal of the blood vessel diameter. can do. This is useful because the influence of the blood flow velocity on the first pulse wave propagation velocity can be reduced.

  The twelfth invention controls the cuff pressure of a compression band attached to a predetermined part of a subject on which an artery runs to tighten the predetermined part, and the predetermined part tightened by the compression band Processing transcutaneously measuring the blood vessel diameter of the artery with ultrasound, and calculating a first blood vessel elasticity index value of the artery using a correspondence relationship between the cuff pressure and the blood vessel diameter. This is a blood vessel elasticity index value measurement method executed by the unit.

  According to the twelfth aspect of the invention, it is possible to realize a vascular elasticity index value measuring method that exhibits the same operational effects as the first aspect of the invention.

The figure for demonstrating the whole structure of a blood-pressure measuring device. The figure for demonstrating the whole outline | summary of the flow of a process. The graph which shows the example of the blood vessel diameter blood pressure characteristic. The graph which shows the example of the characteristic of the blood vessel diameter and the blood vessel wall internal / external pressure difference. The graph which shows the change of the blood vessel diameter when cuff pressure is enlarged gradually, and the blood pressure of the subject who does not change also when cuff pressure increases. The figure for demonstrating the positional relationship of the 1st ultrasonic sensor with respect to a compression belt, and a 2nd ultrasonic sensor. The figure for demonstrating the mode of the ultrasonic measurement by a 1st ultrasonic sensor and a 2nd ultrasonic sensor. It is an example of a time-series waveform of the first blood vessel diameter D1 and the second blood vessel diameter D2, and (1) a blood vessel diameter waveform, (2) an acceleration waveform obtained by second-order differentiation of the blood vessel diameter with time, and (3) an acceleration waveform in the diastole. The figure which shows expansion. The block diagram which shows the function structural example of a blood-pressure measurement apparatus. The figure which shows the data structural example of the blood vessel diameter log data. The figure which shows the data structural example of the cuff pressure log data at the time of pressurization. The figure which shows the data structural example of intermediate 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 blood-pressure calculation process. The figure which shows the structural example of the probe part in a modification. The block diagram which shows the function 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 which the blood-pressure measuring apparatus in a modification performs. The flowchart for demonstrating the flow of the blood-pressure calculation process which the blood-pressure measuring apparatus in a modification performs.

  Hereinafter, an embodiment to which the present invention is applied will be described, but it is needless to say that an applicable form of the present invention is not limited to the following embodiment.

FIG. 1 is a diagram for explaining the overall configuration of the blood pressure measurement device 1 according to the present embodiment, and shows a state in which the blood pressure measurement device 1 is attached. The compression band 20 is indicated by a broken line and is shown as a transmission diagram of the compression band 20.
The blood pressure measurement device 1 is a device that is attached to a predetermined part of a subject 3 in which a blood vessel 5 that is a predetermined artery travels, and is used for blood pressure measurement for every beat (always measurement). In the present embodiment, the predetermined portion is the upper arm and the blood vessel 5 is the brachial artery, but may be a portion other than the upper arm as long as the blood vessel diameter of the artery can be measured with ultrasound. . For example, a carotid artery, a subclavian artery, an aorta, or the like may be measured, and a portion where the artery travels may be set as a predetermined portion.

  In addition, the blood pressure measurement device 1 includes a compression band 20 called a manchette (or a cuff band or simply called a cuff) containing a cuff that expands with air pressure, a main body device 10 provided outside the compression band 20, and a compression band. An integrated configuration comprising an probe 20 for transmitting and receiving ultrasonic waves for transcutaneously measuring the blood vessel diameter of the blood vessel 5, located on the inner side of 20 (the side in contact with the skin surface of the subject 3). It has become. Of course, instead of the integrated type, the main body device 10 may be separated and connected in a wired or wireless manner, so that the weight of the attachment attached to the subject 3 can be reduced. The blood pressure measurement device 1 can also be called a blood vessel elasticity index value measurement device because it has a function of measuring a blood vessel elasticity index value.

  The compression band 20 is a manchette including a pressurizing unit 21 (see FIG. 9) for sending air into the cuff and a pressure sensor 22 (see FIG. 9) for measuring the cuff pressure. The pressurizing unit 21 increases the cuff pressure based on the control signal from the main body device 10, and uniformly tightens the upper arm part, which is the attachment site, from the entire circumference. The pressure sensor 22 outputs the current cuff pressure to the main body device 10 as needed.

  The probe unit 30 includes a first ultrasonic sensor 31 and a second ultrasonic sensor 32 as ultrasonic sensors having the same specifications. The first ultrasonic sensor 31 and the second ultrasonic sensor 32 are thin array sensors, which transmit and radiate ultrasonic pulses to the subject 3 and receive the reflected waves.

  The probe section 30 has a small and thin shape as a whole, and can be configured to be provided at a predetermined position of the compression band 20 or can be configured as a separate body from the compression band 20. In the latter example, for example, the probe unit 30 is configured to be affixed to the skin of the subject 3, and the compression band 20 is attached after the probe unit 30 is affixed to the skin. FIG. 1 shows the latter example, and shows an example in which a first ultrasonic sensor 31 and a second ultrasonic sensor 32 are provided on the adhesive pedestal 34.

  On the other hand, in the former example, for example, the probe unit 30 is disposed on the inner side of the compression band 20 (a contact surface that is in contact with the subject 3 or close to the contact surface). It can be set as the structure mounted | worn in a position. In this case, the adhesive pedestal 34 may be omitted. In any case, a configuration in which at least one ultrasonic sensor of the probe unit 30 is mounted on the mounting site so as to be positioned in the center in the width direction of the compression band 20 is preferable. One ultrasonic sensor is used for calibration of the vascular elasticity index value, and in the present embodiment, the first ultrasonic sensor 31 is used.

  The main body device 10 is a kind of computer control device having an operation input unit 200, a display unit 400, and the like (see FIG. 9), and controls the compression band 20 and the probe unit 30. The control of the compression band 20 is executed in the calibration process, and the pressure control of the compression band 20 is not performed in blood pressure measurement at every beat, that is, in continuous measurement. On the other hand, the control of the probe unit 30 is executed in calibration processing and blood pressure measurement at every beat. Based on the measurement result of the probe unit 30, the blood vessel diameter of the blood vessel 5 is measured in real time, and the blood pressure is calculated using the calibrated blood vessel elasticity index value and the measured blood vessel diameter.

In addition, the main body device 10 performs a process of determining whether or not the vascular elasticity index value needs to be calibrated when measuring blood pressure every beat. Specifically, the pulse wave velocity is obtained from the measurement result of the probe unit 30, and the blood vessel elasticity index value of the blood vessel 5 is calculated using the measured blood vessel diameter and pulse wave velocity. The vascular elasticity index value calculated here is a value for determining whether or not calibration is necessary. In the present embodiment, the vascular elasticity index value calculated for determining whether calibration is necessary is referred to as a “second vascular elasticity index value”, and the vascular elasticity index value used for blood pressure measurement is referred to as “first vascular elasticity index value”. Will be referred to as a “vascular elasticity index value”.
In the present embodiment, the vascular elasticity index value is described as the stiffness parameter β.

  The processing flow described above will be described with reference to FIG. 2. First, at the start of measurement, calibration processing for measuring the first vascular elasticity index value is performed (step A2). In the calibration process, the main body device 10 pressurizes the compression band 20 by injecting air into the cuff and tightens the upper arm portion. Then, the first blood vessel elasticity index value is measured based on the correspondence between the blood vessel diameter of the blood vessel 5 based on the measurement result of the probe unit 30 and the cuff pressure. The principle of measuring the first vascular elasticity index value will be described later in detail.

  After the calibration process, the pressure is released and measurement is performed under no pressure. First, a second vascular elasticity index value is calculated based on the measurement result of the probe unit 30 (step A4). The principle of the second vascular elasticity index value calculation method will be described later in detail.

  Next, it is determined whether or not calibration processing should be performed (step A6). For example, whether or not calibration processing is necessary is determined based on whether or not the difference between the first vascular elasticity index value and the second vascular elasticity index value satisfies a predetermined threshold value. When it is determined that the calibration process is necessary (step A6: YES), the calibration process is executed again, and the first vascular elasticity index value is updated. When it is determined that the calibration process is unnecessary (step A6: NO), the process proceeds to step A8, and the blood pressure measurement process is executed. This blood pressure measurement process is a process of calculating blood pressure for each beat using the latest calibrated first blood vessel elasticity index value and the blood vessel diameter based on the measurement result of the probe unit 30.

  The above processing is repeatedly executed until an instruction to end blood pressure measurement is given (steps A2 to A10). The second vascular elasticity index value calculation process in step A4 and the blood pressure measurement process in step A8 are executed every beat under no pressure.

[Principle of measurement of first vascular elasticity index value]
Next, the principle of measurement of the first vascular elasticity index value in the calibration process will be described.
It is known that the blood vessel diameter blood pressure characteristic in the non-pressurized state has a nonlinear characteristic as shown in FIG. 3, 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 relationship of Expression (1) and Expression (2) There is.

  Therefore, obtaining the blood vessel diameter blood pressure characteristic means calculating the stiffness parameter β. In order to calculate the stiffness parameter β, it is only necessary to know the two blood pressures of the systolic blood pressure Ps and the diastolic blood pressure Pd, and the systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd in each blood pressure (FIG. 3). Plot of white circle inside).

  Since the stiffness parameter β once calibrated is used as a first blood vessel elasticity index value for blood pressure measurement at every beat as shown in FIG. 2, it is necessary to calculate a more accurate stiffness parameter β.

  Here, considering the case where the upper arm portion of the subject 3 is pressed and pressurized by the compression band 20, the characteristics of the blood vessel diameter and the blood vessel wall internal / external pressure difference (Transmural pressure) are as shown in FIG. That is, the curve of the blood vessel diameter blood pressure characteristic itself does not change. However, the effective intravascular external pressure difference on the blood vessel wall decreases by the cuff pressure Pf from the systolic blood pressure Ps and the diastolic blood pressure Pd in both the systole and the diastole, and accordingly, along the curve of the blood vessel diameter blood pressure characteristic. The systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd also decrease. The white circle plots in FIG. 4 are the non-pressurized systolic and diastolic plots, and the black circle plots are the pressurized systolic and diastolic plots.

  It should be noted that the change width (pulsation width) of the blood vessel diameter D between the systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd, and the change width ΔD2 during pressurization rather than the change width ΔD1 during non-pressurization. Is bigger. The effective intra-vascular wall pressure difference applied to the blood vessel wall only decreases by the cuff pressure Pf from the systolic blood pressure Ps and the diastolic blood pressure Pd, and the change width ΔPds does not change. However, due to the non-linear characteristic of the difference between the blood vessel diameter and the blood vessel wall internal / external pressure difference, the change width of the blood vessel diameter D increases by pressurization. This works as a positive effect on the blood vessel diameter D that can be directly measured by the probe unit 30. That is, the measurement accuracy of the blood vessel diameter D by the probe unit 30 is the same whether it is in a pressurized state or in a non-pressurized state. However, since the blood vessel diameter D of the blood vessel 5 to be measured is greatly changed by pressurization, it means that the measurement accuracy of the blood vessel diameter D is improved as compared with the non-pressurization. Considering the characteristics of the blood vessel diameter and the blood vessel wall internal / external pressure difference, a slight difference in the blood vessel wall internal / external pressure difference appears as a large difference in the blood vessel diameter D at the time of pressurization as compared with the case of non-pressurization. Therefore, the calculation accuracy for the blood pressure P is improved by pressurization, and as a result, the calculation accuracy of the stiffness parameter β can be improved.

  FIG. 5 is a diagram showing the blood vessel diameter D together with the blood pressure P and the cuff pressure Pf when the cuff pressure Pf is gradually increased. The effective blood pressure difference between the blood vessel 5 at the measurement site (= blood pressure P−cuff pressure Pf) gradually decreases as the cuff pressure Pf increases. This is because, in the characteristics of the blood vessel diameter and the blood vessel wall internal / external pressure difference in FIG. 4, when the blood pressure P of the subject 3 is constant, the white circle plot points are effective blood vessel walls when the cuff pressure Pf is applied from outside the blood vessel. Since the internal / external pressure difference decreases from the blood pressure P by the cuff pressure Pf, this is the same phenomenon as moving to a black circle plot point on the characteristic curve.

  Returning to FIG. 5, with the pulsation, the blood pressure P pulsates, and the blood vessel diameter D also pulsates. However, when the cuff pressure Pf gradually increases, the blood pressure P does not change, but the effective pressure difference between the inside and outside of the blood vessel wall becomes small. Therefore, the blood vessel diameter D becomes small and the pulsation width (both amplitude) It can be said that it gradually increases. This is based on the non-linear characteristic of the blood vessel diameter blood pressure characteristic or the characteristic of the blood vessel diameter and the blood vessel wall internal / external pressure difference.

なお、式（３−１）において、カフ圧Ｐｆ（ｔ１）はゼロ（非加圧）のため、収縮期血管径Ｄｓ（ｔ１）ではなく、非加圧時の収縮期血管径Ｄｓとしている。 Here, the cuff pressures Pf (t1) to (t4) at the times t1 to t4 and the systolic blood vessel diameters Ds (t1) to (t4) at that time are sampled values, and the cuff pressures Pf are different. When substituted, the following equations (3-1) to (3-4) are obtained.

In Expression (3-1), since the cuff pressure Pf (t1) is zero (non-pressurized), the systolic blood vessel diameter Ds at the time of non-pressurization is used instead of the systolic blood vessel diameter Ds (t1).

  In equations (3-1) to (3-4), there are three unknowns: systolic blood pressure Ps, diastolic blood pressure Pd, and stiffness parameter β. Therefore, the systolic blood pressure Ps, the diastolic blood pressure Pd, and the stiffness parameter β can be obtained by solving the nonlinear simultaneous equations of Expressions (3-1) to (3-4).

  Arbitrary numerical analysis methods can be used as the arithmetic processing for solving the nonlinear simultaneous equations. Newton's method and Newton-Raphson's method are known as iterative root-finding algorithms suitable for numerical calculation by a computer, and these algorithms can also be adopted. Of course, other algorithms such as a non-linear least square method may be employed.

For example, the following numerical calculation can be adopted as an example.
By subtracting both sides of equation (3-2) from both sides of equation (3-1), the following equation (4) is obtained.

Similarly, the following equation (5) is obtained by subtracting both sides of equation (3-4) from both sides of equation (3-3).

When both sides of equation (4) are divided by both sides of equation (5), the following equation (6) is obtained.

Here, a value obtained by subtracting the right side from the left side of Equation (6) is defined as error Er.

  The candidate value of the stiffness parameter β is sequentially substituted for the error Er, and the candidate value with the smallest error Er becomes the stiffness parameter β. The stiffness parameter β obtained here becomes the first vascular elasticity index value, and the first vascular elasticity index value is calibrated.

  By substituting the obtained stiffness parameter β into the equation (4), the diastolic blood pressure Pd can be obtained. By substituting the stiffness parameter β and the diastolic blood pressure Pd into the equation (1), the systolic blood pressure Ps is obtained. Can be sought. Therefore, it is possible to measure the blood pressure in conjunction with the calibration of the first vascular elasticity index value.

  Since there are three unknowns, it is sufficient that there are at least three sampling values. That is, the stiffness parameter β, which is a vascular elasticity index value, can be calculated using a correspondence relationship of three or more between the cuff pressure Pf and the vascular diameter D.

  In the above calculation example, the sampling value is the blood vessel diameter D in the systole having different cuff pressure Pf, but may be the blood vessel diameter D in the diastole or overlapping notch with different cuff pressure Pf. Alternatively, the blood vessel diameter D at the same sampling time (for example, diastole, systole, overlap notch) may be used as the sampling value. In short, the sampling value is required to be a sampling value that satisfies a simultaneous equation that can be derived by substituting into Equation (1). Therefore, the stiffness parameter β as the first vascular elasticity index value is calculated by using at least the correspondence relationship between the cuff pressure Pf or three or more cuff pressures Pf having different timings during one cardiac cycle and the vascular diameter D. can do.

  Further, the sampling value is not limited to three or four, but may be five or more. In numerical calculation by a computer, the more equations, the faster the convergence by iterative calculation (convergence calculation).

  Furthermore, it is possible to end the calibration when the stiffness parameter β is obtained by the convergence calculation without fixing the number of samplings. Specifically, in the process of gradually applying the cuff pressure Pf, the iterative calculation for obtaining the sampling value and adding the equation to calculate the temporary value of the stiffness parameter β is repeated, and the calculated temporary value is predetermined. When it is determined that the convergence condition (for example, the convergence condition is that the difference between the past provisional value and the current provisional value is below a certain value) is satisfied, the provisional value is determined as the value of the stiffness parameter β. Then, the application of the cuff pressure Pf may be stopped to end the calibration. In this case, for example, if three sampling values can be acquired with one heartbeat, the equation obtained with the sampling value for one heartbeat immediately before the cuff pressure Pf is applied and a little cuff pressure Pf are applied. It is theoretically possible to calculate the stiffness parameter β from the data obtained for the total of two heartbeats with the equation obtained with the sampling value for one heartbeat.

  In the example shown in FIG. 5, the cuff pressure Pf is increased at a constant speed. However, the cuff pressure Pf may be gradually increased stepwise (stepped). In that case, for example, during a plurality of beats, the same cuff pressure Pf is used to measure a plurality of blood vessel diameters D in the same characteristic period (systolic period, diastole period, overlapping notch stage) with different beats, and the average value is calculated. It is good also as using as one sampling value.

  One of the characteristic points in this principle is that the blood vessel diameter D is measured in a state where the cuff pressure Pf does not exceed the diastolic blood pressure Pd. This is because, even when the cuff pressure Pf does not exceed the diastolic blood pressure Pd, the pulsation width of the blood vessel diameter D changes greatly, so that the above-described effect of improving the calculation accuracy of the stiffness parameter β works (FIG. 5). reference). In principle, the Korotkoff method and the oscillometric method perform pressurization control that pressurizes the measurement site with a pressure exceeding the systolic blood pressure Ps, closes the blood vessel and interrupts the blood flow, and then gradually flows the blood flow. Necessary. However, according to the principle of the present embodiment, the cuff pressure Pf is not limited to the systolic blood pressure Ps, as long as the cuff pressure Pf can increase the pulsation width of the blood vessel diameter D compared to the non-pressurization. There is no need to exceed the diastolic blood pressure Pd.

  More specifically, even if the upper limit of the cuff pressure Pf is set to 90 [mmHg] or less, which is the normal value range of the diastolic blood pressure, the effect of the present principle can be obtained. Since the air chamber pressure by the air massager is about 130 [mmHg] at maximum, the cuff pressure Pf according to this principle is the pressure below that of the air massager, with a weak tightening force that is not comparable to the Korotkoff method or the oscillometric method. is there.

  Therefore, the feeling of pressure / heavy pressure given to the subject 3 at the time of calibration of the first vascular elasticity index value can be significantly reduced as compared with the Korotkoff method or the oscillometric method.

  As described above, the measurement site is lightly tightened by controlling the cuff pressure Pf, and the blood vessel diameter D of the blood vessel 5 at the measurement site is measured percutaneously with ultrasound, and the correspondence between the cuff pressure Pf and the blood vessel diameter D is measured. The stiffness parameter β that is the first vascular elasticity index value can be calculated and calibrated using the relationship.

[Principle of Calculation of Second Vascular Elasticity Index Value and Blood Pressure Calculation]
Next, the principle of calculating the second vascular elasticity index value will be described.
In FIG. 1, a first ultrasonic sensor 31 and a second ultrasonic sensor 32 are fixed at a predetermined inter-sensor distance Lp (preferably about 10 mm to 30 mm) with the scanning plane in parallel, and the same blood vessel. 5 is configured to measure a cross-section in the minor axis direction of the blood vessel.

  The case where the adhesive pedestal 34 is provided will be described. The adhesive pedestal 34 has a removable adhesive layer on the skin surface, and is not easily displaced or peeled even when the subject 3 moves his / her body. The adhesive pedestal 34 allows the first ultrasonic sensor 31 and the second ultrasonic sensor 32 to depict the short axis of the blood vessel 5 (brachial artery in this embodiment), and the first ultrasonic sensor 31 is on the heart side ( The second ultrasonic sensor 32 is pasted on the fingertip side (downstream side) on the upstream side. Even when the first ultrasonic sensor 31 and the second ultrasonic sensor 32 are provided on the inner side of the compression band 20 (the side in contact with the skin of the subject 3) without providing the adhesive pedestal 34, the first ultrasonic wave is also provided. The sensor 31 and the second ultrasonic sensor 32 are provided in such a posture as to measure the cross section in the blood vessel short axis direction of the blood vessel 5 with a distance Lp between the sensors.

  The first ultrasonic sensor 31 and the second ultrasonic sensor 32 may be mounted on separate adhesive pedestals 34 without being mounted on the integral adhesive pedestal 34.

  FIG. 6 schematically shows the positional relationship between the first ultrasonic sensor 31 and the second ultrasonic sensor 32 with respect to the compression band 20 in the cross section of the blood vessel 5 in the longitudinal direction of the blood vessel. As shown in FIG. 6, in the present embodiment, at least the first ultrasonic sensor 31 is positioned at the center of the compression band 20 in the width direction (the left-right direction toward FIG. 6). A sensor 31 and a second ultrasonic sensor 32 are arranged. This is because the first ultrasonic sensor 31 is used at the time of calibration of the first vascular elasticity index value described above, and the tightening force by the compression band 20 of the blood vessel 5 is evenly and sufficiently applied from the surroundings. This is for measuring the blood vessel diameter at the position.

  In contrast, the calculation of the second vascular elasticity index value is performed without pressure. Therefore, as long as the second ultrasonic sensor 32 is a position where the blood vessel diameter of the blood vessel 5 can be measured, the relative position with respect to the compression band 20 is not limited.

  FIG. 7 is a cross-sectional view showing a state of ultrasonic measurement by the first ultrasonic sensor 31 and the second ultrasonic sensor 32. The first ultrasonic sensor 31 and the second ultrasonic sensor 32 each send an ultrasonic pulse signal or burst signal of several MHz to several tens of MHz toward the blood vessel 5 from a built-in transmission unit, and a blood vessel in the built-in reception unit. 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 received wave from the front wall 5a and the received wave from the rear wall 5p, that is, the first blood vessel diameter D1 measured by the first ultrasonic sensor 31; The second blood vessel diameter D2 measured by the second ultrasonic sensor 32 is calculated. Transmission of ultrasonic waves and reception of reflected waves are continuously performed at extremely short time intervals. For this reason, the calculation of the first blood vessel diameter D1 and the second blood vessel diameter D2 can also be performed continuously. As a result, a waveform in which the blood vessel diameter changes in time series is obtained.

  FIG. 8 is an example of time-series waveforms of the first blood vessel diameter D1 and the second blood vessel diameter D2, and (1) blood vessel diameter waveform, (2) acceleration waveform obtained by second-order differentiation of blood vessel diameter with time, and (3) diastole. Is an enlarged view of the acceleration waveform. The waveform is simplified for easy understanding.

  According to FIG. 8 (1), the diastole Td, the systole Ts, and the overlapping notch period Tn are known from the changes in the first blood vessel diameter D1 and the second blood vessel diameter D2. Further, since the first ultrasonic sensor 31 is disposed on the heart side with respect to the second ultrasonic sensor 32, the first ultrasonic sensor 31 detects the pressure wave accompanying the cardiac contraction 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, as shown in FIG. 8 (1), the actual change in the blood vessel diameter does not always clearly show the diastole Td, the systole Ts, and the overlapping notch Tn. In particular, there are cases where the peak of systolic phase Ts cannot be clearly identified.

  Therefore, in the present embodiment, in calculating the second vascular elasticity index value, not the peak of the systolic period Ts but the peak of the diastolic period Td and the overlapping notch period Tn is detected and used. Specifically, the first blood vessel diameter D1 and the second blood vessel diameter D2 are subjected to second order differentiation at time t, and the acceleration of each diameter change is obtained. Then, the diastole 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 overlapping notch period Tn can be reliably found. Second order differentiation is an example of a predetermined differentiation operation.

  Note that the use of the second-order differential value secondarily increases the robustness of blood vessel diameter measurement. In other words, when the direction of the ultrasonic wave transmitted from the first ultrasonic sensor 31 or the second ultrasonic sensor 32 (hereinafter referred to as “transmission line”) passes through the center of the cross section in the short axis direction of the blood vessel 5, it appears on the transmission line. Since the fluctuation of the blood vessel diameter becomes the largest, the change of the blood vessel diameter clearly appears in the waveform. However, if the delivery line deviates from the center of the cross section in the minor axis direction, the fluctuation in blood vessel diameter becomes small, and the waveform becomes distorted. In the configuration in which the diastole Td and the overlapping notch period Tn are found from the peak of the blood vessel diameter waveform without performing the differential operation, the subject 3 moves the body, thereby causing the delivery line to the blood vessel 5 to be shifted, and the blood vessel diameter waveform. It is difficult to express the peak of, and continuous measurement may be interrupted without finding the diastolic period Td and the overlapping notch period Tn. However, when second-order differentiation is performed as in the present embodiment, even if the delivery line does not pass through the center of the cross-section in the short axis direction of the blood vessel 5, the acceleration waveform is clear as long as the wall portion of the blood vessel 5 is captured. A strong peak appears. That is, the high robustness with respect to the body movement of the subject 3 is obtained. Even if the subject 3 moves his / her body, the possibility that continuous blood pressure measurement is interrupted is much smaller than in the prior art.

  Although described as performing a second-order differentiation as the differentiation operation, it is also possible to detect the diastole period Td and the overlapping notch period Tn by performing a single differentiation. Even if it is a single differentiation, the robustness with respect to the body movement of the subject 3 is higher than in the conventional technique.

  Now, a pulse wave propagation time difference Δt is obtained from the difference between the peak times t11 and t12 of the second-order differential values of the first blood vessel diameter D1 and the second blood vessel diameter D2. If the pulse wave propagation time difference Δt is obtained, the pulse wave propagation speed PWV is obtained from the pulse wave propagation time difference Δt and the inter-sensor distance Lp. The pulse wave velocity PWV is also calculated for the difference between peak times t13 and t14. The peak times t11 and t12 are times (time periods) corresponding to the diastole period Td, and the peak times t13 and t14 are times corresponding to the overlap 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 diastole Td and the double notch phase Tn, are calculated, The second vascular elasticity index value by substituting the diastolic blood vessel diameter Dd and the double notch blood vessel diameter Dn, the diastole pulse wave velocity PWVd and the double notch pulse wave velocity PWVn into the “value calculation formula” A second stiffness parameter βj is obtained.

  The second vascular elasticity index value is a determination index value for determining whether or not calibration (update) of the first vascular elasticity index value is required. For example, the necessity of the calibration process is determined by, for example, a stiffness parameter β that is a first vascular elasticity index value (hereinafter, the stiffness parameter β that is a first vascular elasticity index value is appropriately referred to as a “first stiffness parameter β”. ) And the second stiffness parameter βj satisfy the predetermined permissible condition, it is determined that the calibration process is unnecessary, and if the permissible condition is not satisfied, it is determined that the calibration process is necessary. The allowable condition may be, for example, a threshold condition for the difference between the first stiffness parameter β and the second stiffness parameter βj, or the difference between the first stiffness parameter β and the second stiffness parameter βj A threshold condition for the ratio divided by the stiffness parameter β of 1 may be used.

  If it is determined that the calibration process is unnecessary (step A6: NO in FIG. 2), the “first blood pressure calculation formula” is calculated using the latest first stiffness parameter β that has been calibrated and the pulse wave velocity PWV. The blood pressure P is obtained based on the above.

Next, the “blood pressure calculation formula” and the “second vascular elasticity index value calculation formula” of the present embodiment will be described.
As described above, the blood vessel diameter blood pressure characteristic in the non-pressurized state is expressed by the equation (1). Although the blood pressure can be calculated using this equation (1), when the blood pressure is calculated using equation (1), the measured value of the blood vessel diameter D is an exponent of the power (also called a power). Therefore, a slight measurement error of the blood vessel diameter D greatly affects the value of the measured blood pressure P. For this reason, since it is inferior in the robustness with respect to the body movement of the subject 3, Formula (1) is unsuitable for the continuous measurement (always measuring) for every beat.

As a relation between the pulse wave propagation velocity PWV and the blood vessel elasticity, a formula (8) which is a Maynes-Cortebeek formula is known. However, the wall thickness h of the blood vessel, the blood vessel radius r, the blood density ρ, and the incremental elastic modulus Einc. The incremental elastic modulus Einc is expressed by equation (9).

Here, when Expression (9) is substituted into Expression (8) and rearranged, Expression (10) is obtained.

Further, when Expression (1) is differentiated by D and arranged, Expression (11) is obtained.

式（１３）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 Expression (11) is substituted into Expression (10), Expression (12) is obtained, and Expression (13) which is the “blood pressure calculation expression” of the present embodiment is obtained by modifying the expression. The “blood pressure calculation formula” in the present embodiment is an expression showing the relationship among the first stiffness parameter β, the blood vessel diameter D, and the pulse wave propagation velocity PWV.

In Expression (13), the change in blood density ρ is extremely small and can be treated as a constant.

Next, the “second vascular elasticity index value calculation formula” of the present embodiment will be described.
A vessel diameter _{D 1} and the pulse-wave propagation velocity PWV ₁ in a given first time T1, where it was able to determine the vessel diameter _{D 2} and pulse-wave propagation velocity PWV ₂ in the second period T2, the values Is substituted into Expression (13), the relational expressions of Expression (14) and Expression (15) are obtained.

Here, when equation (15) is divided by equation (14), equation (16) is obtained.

Expression (2) is established in an arbitrary time phase without being limited to the systole and the diastole. That is, when Expression (16) is substituted into Expression (2), Expression (17) is obtained.

  This formula (17) is the “second vascular elasticity index value calculation formula” of the present embodiment. The “second vascular elasticity index value calculation formula” of the present embodiment indicates that the second stiffness parameter βj can be calculated from the vascular diameter D and the pulse wave propagation velocity PWV at two periods. Two timings can be arbitrarily determined. In the present embodiment, two timings of the diastolic period Td and the overlapping notch period Tn are used in the blood vessel diameter waveform. That is, assuming that the first time T1 is the diastole Td and the second time T2 is the double notch phase Tn, the diastole blood vessel diameter Dd and the double notch blood vessel diameter Dn, the diastole pulse wave propagation velocity PWVd and the double notch phase By substituting the pulse wave propagation velocity PWVn into the “second vascular elasticity index value calculation formula”, the second stiffness parameter βj, which is the second vascular elasticity index value, can be calculated. Of course, the first period T1 may be the overlap notch period Tn and the second period may be the expansion period Td. Moreover, it is good also as the systole Ts instead of the overlap notch period Tn or the diastole Td.

  The diastolic period Td and the overlapping notch period Tn can be adopted as the period within the same beat, so that the second stiffness parameter βj for each beat can be continuously measured (constant measurement). That is, the second vascular elasticity index value serving as a reference (reference value) for determining whether or not the first vascular elasticity index value needs to be calibrated can be measured every beat under no pressure.

  Moreover, since blood pressure is measured based on Formula (13), the robustness with respect to the body movement of the subject 3 can be improved. That is, when blood pressure is measured based on the formula (1), the value of the blood vessel diameter D acts as a power exponent. For this reason, if 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 enormous. On the other hand, in the expression (13) of the present embodiment, the value of the blood vessel diameter D is not used as a power exponent and is not a power value. Therefore, since the influence of the measurement error of the blood vessel diameter D on the calculated blood pressure value is much smaller than before, the robustness to the body movement of the subject 3 can be improved.

[Description of functional configuration]
Next, a functional configuration for realizing the present embodiment will be described.
FIG. 9 is a block diagram illustrating a functional configuration example of the blood pressure measurement device 1 according to the present embodiment. The blood pressure measurement device 1 includes a main body device 10, a compression band 20, and a probe unit 30. The main device 10 includes a processing unit 100, an operation input unit 200, a display unit 400, a sound output unit 430, a communication unit 450, and a storage unit 500.

  The compression band 20 is a manchette having a cuff (or simply referred to as a cuff), a pressurizing unit 21 that controls the cuff pressure Pf in accordance with a control signal from the processing unit 100, and measures the cuff pressure as needed to the processing unit 100. And a pressure sensor 22 for outputting. The upper limit of the cuff pressure Pf by the pressurizing unit 21 is 140 [mmHg] or less, or 90 [mmHg] or less.

  The probe unit 30 includes a first ultrasonic sensor 31 and a second ultrasonic sensor 32. The first ultrasonic sensor 31 and the second ultrasonic sensor 32 perform transmission / irradiation of ultrasonic waves for ultrasonic measurement and reception of reflected waves based on transmission control signals 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 performs overall control of the blood pressure measurement device 1 and performs 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. Realized by electronic components. Then, input / output control of data is performed with each function unit, and various arithmetic processes are executed based on predetermined programs and data, operation input signals from the operation input unit 200, etc. Information (in this embodiment, vascular 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 feature period determination unit 106, a heart rate determination unit 108, and a calibration control unit 110 including a first vascular elasticity index value calculation unit 112. The pulse wave velocity measuring unit 116, the second vascular elasticity index value calculating unit 122, the blood pressure calculating unit 124, the calibration determining unit 127, the display information generating unit 132, and the time measuring unit 134.

  The ultrasonic measurement control unit 102 controls ultrasonic measurement in an integrated manner. Specifically, transmission and reception control of ultrasonic waves by the first ultrasonic sensor 31 and the second ultrasonic sensor 32, a process of amplifying the received signal of the reflected wave and converting it into a digital signal, and the like are performed.

  The blood vessel diameter measuring unit 104 continuously measures the blood vessel diameter of the blood vessel 5 (the brachial artery in this embodiment) based on the ultrasonic reception signal. By this continuous measurement, a time-varying waveform of the blood vessel diameter is obtained. In the present embodiment, the first blood vessel diameter D1 is measured from the received signal of the first ultrasonic sensor 31 and the second blood vessel is received from the received signal of the second ultrasonic sensor 32 regardless of whether the calibration process is being executed. The diameter D2 is to be measured. 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 difference in distance from the front wall 5a to the rear wall 5p is obtained. The blood vessel diameter may be measured.

  Further, based on the time-varying waveform of the blood vessel diameter measured by the blood vessel diameter measuring unit 104, the feature period determining unit 106 determines the first time, the second time, and the third time. In this embodiment, the first period is the diastole Td, the second period is the overlap notch period Tn, and the third period is the systole period Ts, but the first to third periods may be any characteristic period. Of course. The characteristic period determination unit 106 includes a diastole Td, an overlap notch period Tn, and a systole Ts corresponding to the first blood vessel diameter D1, and a diastole Td, an overlap notch period Tn, and a systole corresponding to the second blood vessel diameter D2. Ts is determined. The blood vessel diameter measuring unit 104 specifies the blood vessel diameter of the characteristic period determined by the characteristic period determining unit 106. Specifically, among the changing first blood vessel diameter D1, the diastole blood vessel diameter Dd corresponding to the diastole phase Td, the double notch blood vessel diameter Dn corresponding to the double notch phase Tn, and the systole Ts. The systolic blood vessel diameter Ds is specified. Of the second blood vessel diameter D2, the diastole blood vessel diameter Dd corresponding to the diastole, the double notch blood vessel diameter Dn corresponding to the double notch phase, and the systolic blood vessel diameter Ds corresponding to the systole Ts Is identified.

  The feature period determination unit 106 performs a predetermined differential operation on the time-varying waveform of the blood vessel diameter, and determines the diastolic period Td, the overlapping notch period Tn, and the systole period Ts, which are the characteristic periods of the pulse wave. In the present embodiment, the second-order differentiation is performed, and the characteristic period of the diastolic period Td and the overlap notch period Tn is detected by detecting the time point (time) when the peak condition indicating that the second-order differential value is a peak that is equal to or higher than the reference is detected. judge. Further, the systolic period Ts is determined by detecting a peak value that appears periodically from the time-varying waveform of the blood vessel diameter.

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

  The calibration control unit 110 is a functional unit for executing a calibration process, and executes the calibration process at the start of blood pressure measurement and when the calibration determination unit 127 determines that calibration is necessary. The calibration control unit 110 increases the cuff pressure Pf of the compression band 20 to tighten the measurement site of the subject 3, and the first vascular elasticity index value calculation unit 112 determines the correspondence between the cuff pressure Pf and the vascular diameter D. Is used to calculate the first stiffness parameter β which is the first vascular elasticity index value of the blood vessel 5, thereby calibrating the first vascular elasticity index value.

  The pulse wave velocity measuring unit 116 measures the pulse wave velocity PWV in the blood vessel 5. In the present embodiment, the pulse wave propagation time difference Δt in the characteristic period is calculated for each of the diastole Td, the overlap notch period Tn, and the systolic period Ts, and the pulse wave propagation speed PWV is calculated from the time difference Δt and the inter-sensor distance Lp. Ask for. That is, the diastolic pulse wave velocity PWVd, the overlapping notch pulse wave velocity PWVn, and the systolic pulse wave velocity PWVs are obtained.

  The second vascular elasticity index value calculation unit 122 is either (1) 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 Diastolic blood vessel diameter Dd and overlapping notch blood vessel diameter Dn related to blood vessel diameter D2, (2) Diastolic pulse wave propagation velocity PWVd and overlapping notch pulse wave velocity measured by pulse wave velocity measuring unit 116 By substituting PWVn into equation (17), the value of the second stiffness parameter βj, which is the second vascular 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 propagation velocity PWV measured by the pulse wave velocity measurement unit 116, and the first blood vessel elasticity index value calculation unit 112. The blood pressure is calculated by performing a predetermined calculation process using the first stiffness parameter β as a variable. In the present embodiment, the blood pressure is calculated by performing arithmetic processing according to the equation (13) in which the blood pressure is proportional to the square of the pulse wave propagation velocity and is proportional to the inverse of the blood vessel diameter D.

  More specifically, the diastolic blood pressure Pd and the overlapping notch blood pressure Pn are obtained using the equation (13). When obtaining the diastolic blood pressure Pd, the blood pressure calculation unit 124 determines the measured diastolic pressure. The diastolic blood pressure Pd is obtained by substituting the blood vessel diameter Dd, the diastolic pulse wave velocity PWVd, and the first stiffness parameter β into the equation (13). At this time, the value of the measured diastolic blood vessel diameter Dd is substituted into the blood vessel diameter D in the equation (13).

  When determining the double notch blood pressure Pn, the blood pressure calculation unit 124 determines the measured double notch blood vessel diameter Dn, the double notch pulse wave velocity PWVn, the first stiffness parameter β, the diastole. By substituting the blood vessel diameter Dd into the equation (13), the double notch blood pressure Pn is obtained. At this time, the value of the measured double notch blood vessel diameter Dn is substituted into the blood vessel diameter D in the equation (13).

  The value to be substituted for the blood vessel diameter D in equation (13) may be either the first blood vessel diameter D1 or the second blood vessel diameter D2.

  Further, the blood pressure calculation unit 124 obtains the systolic blood pressure Ps by substituting the systolic blood vessel diameter Ds into the equation (1). However, the diastolic blood vessel diameter Dd and the diastolic blood pressure Pd in the equation (1) used at this time are obtained by using the diastolic blood vessel diameter Dd and the equation (13) substituted in the equation (13). Pd can be used.

  In addition, 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 overlapping 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 calibration determination unit 127 is a functional unit that determines whether calibration of the first vascular elasticity index value is necessary. In the present embodiment, the first stiffness parameter β, which is the first vascular elasticity index value, is compared with the second stiffness parameter βj, which is the second vascular elasticity index value calculated every beat, and the calibration is performed. The necessity is determined. The comparison method includes a method of determining whether or not an allowable condition (threshold condition) based on a difference between the first stiffness parameter β and the second stiffness parameter βj is satisfied, the first stiffness parameter β, It is possible to adopt a method for determining whether or not an allowable condition (threshold condition) based on a ratio obtained by dividing the difference from the stiffness parameter βj by the first stiffness parameter β is satisfied.

  As another method, the necessity of calibration may be determined based on whether or not the blood pressure has greatly changed based on the blood pressure history calculated by the blood pressure calculation unit 124.

  The display information generation unit 132 generates images for displaying various operation screens and measurement results necessary for blood pressure measurement, and outputs them 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 134 measures the measurement time. The timing method can be selected as appropriate, but for example, a 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 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. 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, or an optical disk, and stores various programs and various data such as calculation process data of the processing unit 100. Note that the processing unit 100 and the storage unit 500 may be separated from each other and realized by a communication connection via a communication line such as a LAN (Local Area Network) or the Internet. For example, in this case, the storage unit 500 can be realized as a storage device of a server connected to the Internet.

  The storage unit 500 stores the blood pressure measurement program 510, the blood vessel diameter log data 520, the pressurization cuff pressure log data 530, the intermediate data 540, the first blood vessel elasticity index value 561, and the second blood vessel elasticity. The index value 562 and blood pressure log data 570 are stored. Of course, in addition to these, flags for various determinations, counter values for timing, etc. can be stored as appropriate.

  When the processing unit 100 executes the blood pressure measurement program 510, the ultrasonic measurement control unit 102, the blood vessel diameter measurement unit 104, the feature period determination unit 106, the heart rate determination unit 108, and the first blood vessel elasticity index value calculation unit 112 are displayed. The functions of the calibration control unit 110, the pulse wave velocity measuring unit 116, the second blood vessel elasticity index value calculating unit 122, the blood pressure calculating unit 124, the calibration determining unit 127, the display information generating unit 132, the time measuring unit 134, and the like are realized. . Any one of these functional units can be realized by hardware such as an electronic circuit.

  The blood pressure measurement program 510 includes a first vascular elasticity index value for realizing a first vascular elasticity index value measurement process (also referred to as a calibration process) for measuring the first vascular elasticity index value as a subroutine program. A measurement program 512 and a second vascular elasticity index value measurement program 514 for realizing a second vascular elasticity index value measurement process for measuring a second vascular elasticity index value are included.

  The blood vessel diameter log data 520 is a variety of data relating to the blood vessel diameter of the blood vessel 5 obtained by sending out ultrasonic waves and receiving reflected waves by the probe unit 30 continuously performed at extremely short time intervals from the start to the end of measurement. Is stored. Specifically, as shown in FIG. 10, a pulse number 522 for identifying the pulse at the time in association with the measurement time 521 for each ultrasonic measurement cycle (for example, how many beats from the start of measurement) And a first blood vessel diameter 523 and a second blood vessel diameter 524 measured at that time, a first blood vessel diameter second-order differential value 525, and a second blood vessel diameter second-order differential value 526 are stored. . Of course, other data can be stored as appropriate. In FIG. 10, the measurement time 521 gradually elapses as “t001”, “t002”, “t003”, and “t004”, but since the pulsation number 522 is “1”, the same pulsation occurs. It is shown that it is the data concerning. By looking at the first blood vessel diameter 523 and the second blood vessel diameter 524 in time series, a time-varying waveform of the blood vessel diameter can be obtained. Further, in “t001” and “t002”, the first vascular diameter second-order differential value 525 and the second vascular diameter second-order differential value 526 are “NULL” because the data is before the 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 determination unit 108, and the measurement result of the blood vessel diameter measurement unit 104 is stored in the first blood vessel diameter 523 and the second blood vessel diameter 524. 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 feature period determination unit 106 determines the feature period.

  The cuff pressure log data 530 during pressurization is detected by the pressure sensor 22 when the cuff pressure Pf of the compression band 20 is controlled in the calibration process (first blood vessel elasticity index value measurement process) by the calibration control unit 110. Data on the cuff pressure Pf is stored. Specifically, as shown in FIG. 11, the pulse number 532 (blood vessel diameter log data 520 at that time is associated with the measurement time 531 corresponding to the measurement time 521 (see FIG. 10) of the blood vessel diameter log data 520. And the cuff pressure Pf at that time are stored.

  The intermediate data 540 stores data related to the feature period determined by the feature period determination unit 106. Specifically, as shown in FIG. 12, the diastolic blood vessel diameter 551a associated with the first blood vessel diameter D1 in the pulsation in association with the pulsation number 541 corresponding to the pulsation number 522 of the blood vessel diameter log data 520 , The diastolic blood vessel diameter 551b and the systolic blood vessel diameter 551c, the diastolic blood vessel diameter 552a related to the second blood vessel diameter D2, the double notch blood vessel diameter 552b and the systolic blood vessel diameter 552c, and the diastolic pulse wave propagation velocity. 553a, overlapping notch pulse wave velocity 553b and systolic pulse wave velocity 553c are stored.

  Diastolic blood vessel diameter 551a, overlapping notch blood vessel diameter 551b and systolic blood vessel diameter 551c related to the first blood vessel diameter D1, and diastolic blood vessel diameter 552a, overlapping notch blood vessel diameter 552b and contraction related to the second blood vessel diameter D2. The term blood vessel diameter 552c stores the blood vessel diameter of the characteristic phase identified by the blood vessel diameter measuring unit 104. The diastolic pulse wave velocity 553a, the overlapping notch pulse wave velocity 553b, and the systolic pulse wave velocity 553c store the pulse wave velocity calculated by the pulse wave velocity measuring unit 116.

  The first vascular elasticity index value 561 stores the latest first vascular elasticity index value calculated by the first vascular elasticity index value calculation unit 112 (the value of the stiffness parameter β in this embodiment). The first vascular elasticity index value 561 is updated every time the calibration process is executed.

  The second vascular elasticity index value 562 stores the latest second vascular elasticity index value calculated by the second vascular elasticity index value calculation unit 122 (the value of the second stiffness parameter βj in this embodiment). . The second vascular elasticity index value 562 is updated every beat.

  Note that log data recorded historically in association with the first vascular elasticity index value 561 and the second vascular elasticity index value 562 are associated with the pulsation number (corresponding to the pulsation number 522 of the vascular diameter log data 520). Further, it may be stored in the storage unit 500.

  As shown in FIG. 13, the blood pressure log data 570 includes the diastolic blood pressure 572, the systolic blood pressure 573, and the double notch blood pressure 574 calculated by the blood pressure calculation unit 124 in the pulsation number 522 of the blood vessel diameter log data 520. It stores in association with the corresponding pulsation number 571. That is, the blood pressure for each beat is stored.

[Description of process flow]
Next, the operation of the blood pressure measurement device 1 will be described.
FIG. 14 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. It is assumed that the compression band 20 and the probe unit 30 are installed at predetermined positions of the subject 3 in advance.

  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, calculation and recording of the second-order differential value of the blood vessel diameter D is started (step S4). Data is stored in the blood vessel diameter log data 520 through steps S2 and S4.

  Further, the processing unit 100 starts a process of determining the characteristic period of the first blood vessel diameter D1 and the second blood vessel diameter D2 based on the blood vessel diameter log data 520 (step S6), and the first blood vessel diameter D1 and the second blood vessel. For each of the diameters D2, the heart rate determination for determining the heart rate break based on the fluctuation of the blood vessel diameter D is started (step S8). The determined heartbeat identification information is stored in the heartbeat number 522 of the blood vessel diameter log data 520 as the heartbeat number from the start of measurement. Further, the first blood vessel diameter D1 and the second blood vessel diameter D2 of each feature period are stored in the intermediate data 540.

  Next, the processing unit 100 executes a first vascular elasticity index value measurement process that is a calibration process (steps S12 to S16). That is, the cuff pressure control for increasing the cuff pressure Pf to the pressurizing unit 21 is started (step S12), and the cuff pressure Pf obtained from the pressure sensor 22 is stored in the cuff pressure log data 530 during pressurization. When the data necessary for calculating the first vascular elasticity index value is obtained, the cuff pressure control is terminated (step S14), and the pressure is returned to non-pressurization. Then, with reference to the cuff pressure log data 530 and the blood vessel diameter log data 520 during pressurization, the first vascular elasticity index value is determined using the correspondence relationship between the cuff pressure Pf and the first blood vessel diameter D1 at the same measurement time. The stiffness parameter β is calculated (step S16). The calculated value of the stiffness parameter β is updated and stored in the first vascular elasticity index value 561.

  Next, the processing unit 100 executes a process of measuring the second vascular elasticity index value for determining whether or not the calibration of the first vascular elasticity index value is necessary (steps S22 to S26). That is, the processing unit 100 obtains the time difference between the diastole related to the first blood vessel diameter D1 and the diastole related to the second blood vessel diameter D2, that is, the diastole pulse wave propagation time Δtd, and the diastole pulse wave propagation time Δtd The diastolic pulse wave velocity PWVd is calculated from the sensor-to-sensor distance Lp (step S22).

  Further, the processing unit 100 obtains a time difference between the overlap notch period related to the first blood vessel diameter D1 and the overlap notch period related to the second blood vessel diameter D2, that is, the overlap notch period pulse wave propagation time Δtn. The overlapping notch pulse wave propagation velocity PWVn is calculated from the imprint pulse wave propagation time Δtn and the sensor-to-sensor distance Lp (step S22). These calculated pulse wave propagation velocities are stored in the intermediate data 540.

  Next, the processing unit 100 may have 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 or the blood vessel diameter of the second blood vessel diameter D2) related to the same pulsation number. ) And the diastolic pulse wave velocity PWVd and the overlapping notch pulse wave velocity PWVn, the value of the second stiffness parameter βj, which is the second vascular elasticity index value, is calculated from equation (17). (Step S26). The calculated value of the second stiffness parameter βj is updated and stored in the second vascular elasticity index value 562.

  Then, the processing unit 100 compares the first vascular elasticity index value 561 and the second vascular elasticity index value 562 to determine whether calibration is necessary (step S32). If it is determined that calibration is necessary (step S32: YES), the process proceeds to step S12, and the first vascular elasticity index value 561 is measured again.

  If it is determined that calibration is unnecessary (step S32: NO), the processing unit 100 performs a blood pressure calculation process (step S40).

FIG. 15 is a flowchart for explaining the flow of blood pressure calculation processing in the present embodiment.
The processing unit 100 uses the first stiffness parameter β that is the first vascular elasticity index value 561, the diastolic blood vessel diameter Dd and the diastolic pulse wave propagation velocity PWVd in the beat (beat number) of the blood pressure measurement target. Thus, the diastolic blood pressure Pd is calculated from the equation (13) (step S42). The diastolic blood vessel diameter Dd is substituted into the blood vessel diameter D, which is a variable in the blood pressure calculation formula of Expression (13).

  In addition, the processing unit 100 includes the first stiffness parameter β that is the first vascular elasticity index value 561, the diastolic blood vessel diameter Dd and the overlapping notch blood vessel diameter Dn in the beat (beat number) of the blood pressure measurement target. And the double notch period blood pressure Pn is calculated from the equation (13) using the notch pulse wave velocity PWVn (step S44). In addition, the overlapping notch stage blood vessel diameter Dn is substituted for the blood vessel diameter D which is a variable of the blood pressure calculation formula of Expression (13).

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

  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 570 and causes the display unit 400 to display them (step S48). At this time, information such as a heart rate, a blood vessel diameter, and a first blood vessel elasticity index value may be displayed together. Further, the display of the overlapping notch period blood pressure Pn may be omitted.

  Returning to FIG. 14, the processing unit 100 repeatedly executes the processes of steps S22 to S40 for each heartbeat until the blood pressure measurement is completed.

  As described above, according to the present embodiment, the measurement site is tightened by the cuff pressure Pf of the compression band 20, and the correspondence between the blood vessel diameter D measured percutaneously by the probe unit 30 and the cuff pressure Pf is used. One vascular elasticity index value is measured and calibrated. However, this cuff pressure Pf does not exceed 140 [mmHg], which is the upper limit value of the normal value range of systolic blood pressure, and of course exceeds 90 [mmHg], which is the normal value range of diastolic blood pressure. There is no need for pressure. Therefore, the feeling of pressure and pressure given to the subject 3 at the time of calibration of the first vascular elasticity index value can be greatly reduced as compared with the Korotkoff method or the oscillometric method.

  Moreover, since the fluctuation range of the blood vessel diameter accompanying the pulsation is increased by tightening with the cuff pressure, the measurement accuracy of the blood vessel elasticity index value can be improved. Therefore, highly accurate measurement of the vascular elasticity index value with a reduced feeling of pressure can be realized.

  In addition, the form which can apply this invention is not restricted to embodiment mentioned above, The addition, omission, and change of a component can be performed suitably.

(A)
For example, although the blood pressure measurement device 1 has been described as being a blood vessel elasticity index value measurement device, it may be configured as a dedicated device that measures 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. 9 may be deleted.

(B)
The pulse wave velocity PWV is said to be about 10 times the blood flow velocity V, but the influence of the blood velocity V on the pulse wave velocity PWV depends on the difference in blood vessel to be measured, the measurement position, and the degree of elasticity of the blood vessel. May reach. That is, the blood flow velocity V is equal to the pulse wave propagation velocity PWV used in the equation (13) that is the “blood pressure calculation equation” and the equation (17) that is the “second blood vessel elasticity index value calculation equation” in the above-described embodiment. May be affected.

Therefore, instead of the pulse wave velocity PWV, the equation (18) defining the “blood pressure calculation equation” using the velocity obtained by subtracting the blood flow velocity V from the pulse wave velocity PWV, or “second blood vessel elasticity index value” It has been found that it may be better to adopt the formula (19) defining the “calculation formula”. That is, the blood vessel diameter _{D 1} and the pulse-wave propagation velocity PWV ₁ and blood flow velocity _{V 1} of the first period _{T 1} in vascular diameter _{D 2} and pulse-wave propagation velocity PWV ₂ and blood flow in the second period _{T 2} When the velocity V ₂ can be obtained, the second stiffness parameter βj, which is the second vascular elasticity index value, can be calculated by substituting these values into the equation (19).

A modification in this case will be described with reference to FIGS. The same components as those in the above-described embodiment and the same processing steps are denoted by the same reference numerals.
FIG. 16 is a diagram illustrating a configuration example of the probe unit 300 in the present modification. It is shown as a diagram corresponding to FIG. The probe unit 300 includes a third ultrasonic sensor 33 for measuring a blood flow velocity V of blood flowing in the blood vessel 5 between the first ultrasonic sensor 31 and the second ultrasonic sensor 32. The blood flow velocity V can be measured by using, for example, an ultrasonic Doppler method.

  FIG. 17 is a block diagram illustrating a functional configuration example of the blood pressure measurement device 2 in the present modification. The main device 12 has a configuration in which the processing unit 100 further includes a blood flow velocity measuring unit 118. In the blood pressure measurement device 2, the ultrasonic measurement control unit 102 controls transmission and reception of ultrasonic waves by the third ultrasonic sensor 33 in addition to the first ultrasonic sensor 31 and the second ultrasonic sensor 32. The blood flow velocity measurement unit 118 controls the blood flow by the ultrasonic Doppler method based on the ultrasonic frequency transmitted from the third ultrasonic sensor 33 and the received ultrasonic frequency under the control of the ultrasonic measurement control unit 102. Velocity V is measured. The blood flow velocity V is measured at the same timing as the blood vessel diameter measurement time 521 (see FIG. 10), and is stored in the blood flow velocity log data 542 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 542 and stored in the intermediate data 543. FIG. 18 is a diagram illustrating an example of the data configuration of the intermediate data 543. In addition to the data structure of the intermediate data 543 (see FIG. 12) of the above-described embodiment, the diastolic blood flow velocity 544a, as the blood flow velocity V of the diastolic phase, the double notch phase, and the systolic phase, which are examples of the characteristic phase, The overlapping notch blood flow velocity 544b and the systolic blood flow velocity 554c are stored in the intermediate data 543 for each beat in association with the beat number 541.

  FIG. 19 is a flowchart for explaining the main processing flow executed by the blood pressure measurement device 2. Instead of step S2 in the flowchart shown in FIG. 14, measurement and recording of the blood vessel diameter and blood flow velocity V are started (step S3).

  In the calculation of the second vascular elasticity index value in step S26, the vascular elasticity index value is calculated using Expression (19). That is, instead of the diastole pulse wave velocity PWVd, a velocity obtained by subtracting the diastole blood flow velocity Vd from the diastole pulse wave velocity PWVd is used, and instead of the double notch pulse wave velocity PWVn, the double notch pulse wave velocity PWVd is used. A second stiffness parameter βj, which is a second vascular elasticity index value, is calculated using a speed obtained by subtracting the overlapping notch stage blood flow speed Vn from the period pulse wave propagation speed PWVn (step S26). By doing in this way, in calculating the second vascular elasticity index value, when the blood flow velocity affects the pulse wave propagation velocity, the influence can be reduced.

FIG. 20 is a flowchart for explaining the flow of blood pressure calculation processing executed by the blood pressure measurement device 2. Steps S42 and S44 in the flowchart shown in FIG. 15 are replaced with steps S43 and S45, respectively.
That is, in step S43, the first stiffness parameter β and the speed obtained by subtracting the diastolic blood flow velocity Vd from the diastolic blood vessel diameter Dd and the diastolic pulse wave velocity PWVd in the beat (beat number) of the blood pressure measurement target. Is used to calculate the diastolic blood pressure Pd (step S43). The calculation formula used at this time is Formula (18).

  In step S45, the first stiffness parameter β, the diastolic blood vessel diameter Dd, the double notch blood vessel diameter Dn, and the double notch pulse wave velocity PWVn in the beat (beat number) of the blood pressure measurement target are obtained. The double-notch blood pressure Pn is calculated using the speed obtained by subtracting the double-notch blood flow velocity Vn from (step S45). The calculation formula used at this time is also formula (18).

  In other words, the expression (18) is obtained by performing a predetermined calculation process proportional to the square of the velocity obtained by subtracting the blood flow velocity V from the pulse wave propagation velocity PWV and proportional to the reciprocal of the blood vessel diameter D to obtain the blood pressure. This is a formula to be calculated. By doing in this way, in calculating blood pressure, it is possible to reduce the influence of blood flow velocity on pulse wave propagation velocity.

  DESCRIPTION OF SYMBOLS 3 ... Subject, 5 ... Blood vessel, 1 ... Blood pressure measuring device, 10 ... Main body device, 20 ... Compression band, 30 ... Probe part, 31 ... 1st ultrasonic sensor, 32 ... 2nd ultrasonic sensor, 100 ... Processing , 102 ... Ultrasound measurement control unit, 104 ... Blood vessel diameter measurement unit, 106 ... Characteristic period determination unit, 108 ... Heart rate determination unit, 110 ... Calibration control unit, 112 ... First vascular elasticity index value calculation unit, 116 ... Pulse wave velocity measurement unit, 122 ... second vascular elasticity index value calculation unit, 124 ... blood pressure calculation unit, 127 ... calibration determination unit

Claims (12)

A compression band that is attached to a predetermined site of a subject on which an artery runs and can tighten the predetermined site by cuff pressure;
A first ultrasonic sensor for percutaneously measuring a blood vessel diameter of the artery at the predetermined site tightened by the compression band;
A first vascular elasticity index value calculating unit that calculates a first vascular elasticity index value of the artery using a correspondence relationship between the cuff pressure and the vascular diameter;
A blood vessel elasticity index value measuring apparatus. The first vascular elasticity index value calculation unit calculates the first vascular elasticity index value using the correspondence relationship at different cuff pressures.
The vascular elasticity index value measuring apparatus according to claim 1. The first vascular elasticity index value calculation unit calculates the first vascular elasticity index value by using the correspondence relationship between the vascular diameter and the cuff pressure related to a predetermined characteristic period in one cardiac cycle.
The blood vessel elasticity index value measuring apparatus according to claim 1 or 2. The first vascular elasticity index value calculation unit calculates the first vascular elasticity index value using at least the cuff pressure or the three or more correspondences having different timings during one cardiac cycle.
The vascular elasticity index value measuring apparatus according to any one of claims 1 to 3. The first vascular elasticity index value calculating unit calculates the first vascular elasticity index value using the correspondence relationship when the cuff pressure is 90 [mmHg] or less.
The vascular elasticity index value measuring apparatus according to any one of claims 1 to 4. The vascular elasticity index value measuring device according to any one of claims 1 to 5,
A blood pressure calculation unit for calculating blood pressure using the first blood vessel elasticity index value measured by the blood vessel elasticity index value measuring apparatus and the blood vessel diameter;
A blood pressure measuring device. A calibration determination unit for determining whether or not to calibrate the first vascular elasticity index value;
And when the affirmative determination is made by the calibration determination unit, the vascular elasticity index value measuring device measures the first vascular elasticity index value, and the blood pressure calculation unit Blood pressure is calculated using the vascular elasticity index value of
The blood pressure measurement device according to claim 6. The calibration determination unit determines to calibrate when the blood pressure calculated by the blood pressure calculation unit satisfies a predetermined abnormal value condition,
The blood pressure measurement device according to claim 7. A second ultrasonic sensor for percutaneously measuring a blood vessel diameter of the artery at a position different from a measurement position by the first ultrasonic sensor;
Using the measurement results obtained by the first and second ultrasonic sensors, the first pulse wave velocity of the first period and the second pulse of the second period, which are characteristic periods of the blood vessel diameter variation of the artery due to pulsation A second blood vessel of the artery using the first pulse wave velocity, the second pulse wave velocity, and the blood vessel diameter at each of the first time period and the second time period. A second vascular elasticity index value measuring unit for measuring an elasticity index value;
Further comprising
The calibration determination unit compares the first vascular elasticity index value measured by the vascular elasticity index value measuring device and the second vascular elasticity index value measured by the second vascular elasticity index value measuring unit. To determine whether or not to calibrate,
The blood pressure measurement device according to claim 7. A blood flow velocity measuring unit for measuring the first blood flow velocity at the first time and the second blood flow velocity at the second time of the artery;
Further comprising
The second vascular elasticity index value measurement unit replaces the first pulse wave propagation velocity by subtracting the first blood flow velocity from the first pulse wave propagation velocity, instead of the first pulse wave propagation velocity. Measuring the second vascular elasticity index value using a velocity obtained by subtracting the second blood flow velocity from the second pulse wave velocity.
The blood pressure measurement device according to claim 9. The blood pressure calculation unit uses the first blood vessel elasticity index value and the blood vessel diameter to calculate a velocity obtained by subtracting the blood flow velocity measured by the blood flow velocity measurement unit from the first pulse wave propagation velocity. Blood pressure is calculated by performing a predetermined calculation process proportional to the square and proportional to the inverse of the blood vessel diameter;
The blood pressure measurement device according to claim 10. Controlling the cuff pressure of the compression band attached to the predetermined part of the subject where the artery runs, and tightening the predetermined part;
Measuring the blood vessel diameter of the artery percutaneously with ultrasound at the predetermined site tightened by the compression band;
Calculating a first vascular elasticity index value of the artery using the correspondence between the cuff pressure and the blood vessel diameter;
The blood vessel elasticity index value measuring method executed by the processing unit.

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