JP2016043094A - Ultrasonic blood pressure measuring instrument and blood pressure measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable blood pressure measurement even when measurement accuracy of a blood vessel diameter is reduced in the blood pressure measurement using an ultrasonic wave.SOLUTION: An ultrasonic blood pressure measuring instrument 10 performs transmission of an ultrasonic wave toward a blood vessel and reception of a reflection wave and measures a blood pressure. In the ultrasonic blood pressure measuring instrument 10, a storage section 300 stores a β blood pressure calculation expression being a first relation between a blood vessel diameter D of the blood vessel and a blood pressure P, a pulse wave velocity calculation section 208 measures a pulse wave velocity PWV of the blood vessel, a β blood pressure calculation expression change section 214 calculates a β blood pressure calculation changing expression being a first change relation obtained by changing the β blood pressure calculation expression using the pulse wave velocity PWV, a blood vessel diameter measurement section 206 measures the blood vessel diameter D of the blood vessel by the ultrasonic wave, and a temporary blood pressure calculation section 220 determines the blood pressure P from the β blood pressure calculation changing expression.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an ultrasonic blood pressure measurement device that measures blood pressure using ultrasonic waves.

  As a technique for noninvasively measuring the blood pressure of a subject, a technique is known in which the blood vessel diameter of a subject's blood vessel is measured using ultrasonic waves, and the blood pressure is estimated from the blood vessel diameter. For example, Patent Document 1 discloses a method of calculating a blood pressure from a stiffness parameter β indicating the hardness of a blood vessel and a blood vessel diameter, taking the relationship between the blood vessel diameter and the blood pressure as a nonlinear function.

JP 2004-41382 A

  When calculating blood pressure from the blood vessel diameter, it is necessary to accurately measure the blood vessel diameter. However, the measurement accuracy of the blood vessel diameter may be reduced due to the change in the position of the blood vessel due to the body movement of the subject such as muscle contraction or joint movement. For example, when the relative positional relationship between the blood vessel and the ultrasonic probe changes, the ultrasonic signal used for measuring the blood vessel diameter cannot measure the diameter without passing through the center of the blood vessel, or the reflected wave of the ultrasonic wave This is a case where the reception intensity becomes weak and the blood vessel diameter cannot be measured.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to enable blood pressure measurement even when blood vessel diameter measurement accuracy is reduced in blood pressure measurement using ultrasonic waves. It is.

  A first invention for solving the above-described problem is an ultrasonic blood pressure measurement device that measures blood pressure by transmitting an ultrasonic wave toward a blood vessel and receiving a reflected wave, and includes a blood vessel diameter and a blood pressure of the blood vessel. A first relationship storage unit for storing the first relationship, a pulse wave velocity measuring unit for measuring the pulse wave velocity of the blood vessel, and a first change in which the first relationship is changed using the pulse wave velocity. A first change relationship calculation unit that calculates a relationship; and a blood pressure determination unit that measures a blood vessel diameter of the blood vessel using the ultrasonic waves and determines a blood pressure from the blood vessel diameter based on the first change relationship. This is a sonic blood pressure measurement device.

  Further, as a fifth invention, there is provided a blood pressure measurement method for measuring blood pressure by transmitting an ultrasonic wave toward a blood vessel and receiving a reflected wave, and measuring the pulse wave propagation velocity of the blood vessel; Calculating a first change relationship in which a first relationship between a predetermined blood vessel diameter and blood pressure is changed using a wave propagation velocity, measuring the blood vessel diameter of the blood vessel using the ultrasonic wave, A blood pressure measurement method including determining blood pressure from the blood vessel diameter based on the first change relationship may be configured.

  According to the first or fifth aspect of the present invention, the first change relationship in which the first relationship between the blood vessel diameter and the blood pressure is changed is calculated using the pulse wave velocity of the blood vessel, and the blood vessel of the blood vessel is obtained by ultrasound. The blood pressure can be determined from the first change relationship by measuring the diameter. Therefore, even when the measurement accuracy of the blood vessel diameter by the ultrasonic wave is low, the blood pressure can be determined using the first change relationship in which the first relationship is changed.

  As a second invention, the ultrasonic blood pressure measurement device according to the first invention, comprising the second relationship storage unit for storing the second relationship between the pulse wave velocity and the blood pressure is configured. You may do it.

  As a sixth invention, a blood pressure measurement method according to the fifth invention, further comprising storing a second relationship between the pulse wave propagation velocity and blood pressure may be configured.

  According to the second or sixth invention, the second relationship between the pulse wave velocity and the blood pressure is stored. Thereby, for example, the blood pressure can be calculated from the pulse wave velocity using the second relationship.

  As a third invention, in the ultrasonic measurement device according to the second invention, the second relationship is a correspondence relationship between the pulse wave propagation velocity and systolic blood pressure, and the first change relationship calculation unit includes: The systolic blood pressure is obtained from the pulse wave propagation velocity measured by the pulse wave propagation velocity measurement unit and the second relationship, and the systolic blood pressure and the systolic blood vessel diameter of the blood vessel measured by the ultrasound are used. An ultrasonic blood pressure measurement device that calculates the first change relationship by changing the first relationship may be configured.

  According to the third aspect of the invention, the second relationship is a correspondence relationship between the pulse wave propagation velocity and the systolic blood pressure, and the first change relationship is the systolic blood pressure obtained from the pulse wave propagation velocity and the second relationship. And the systolic vascular diameter of the blood vessel measured by ultrasonic waves, and the first relationship is changed and calculated.

  As a fourth invention, in the ultrasonic measurement device according to any one of the first to third inventions, when the blood vessel diameter measurement of the blood vessel by the ultrasonic wave satisfies a predetermined reliability condition, the measured blood vessel An ultrasonic blood pressure measurement device that includes a blood pressure determination unit that determines blood pressure from a diameter and the first relationship, and that functions when the predetermined reliability condition is not satisfied, may be configured. .

  According to the fourth invention, when the blood vessel diameter measurement satisfies a predetermined reliability condition, the blood pressure is determined from the measured blood vessel diameter and the first relationship, and when the reliability condition is not satisfied, the measurement is performed. The blood pressure is determined from the blood vessel diameter and the first change relationship.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Explanatory drawing of blood vessel diameter measurement. Correspondence between blood vessel diameter and blood pressure. Explanatory drawing of calculation of a pulse wave velocity. Correlation between pulse wave velocity and systolic blood pressure. Explanatory drawing of the change of the correspondence of a blood vessel diameter and blood pressure. The functional block diagram of an ultrasonic blood pressure measuring device. The flowchart of a blood-pressure measurement process.

[overall structure]
FIG. 1 is a diagram for explaining an outline of an ultrasonic blood pressure measurement apparatus 10 to which the present invention is applied. The ultrasonic blood pressure measurement device 10 is a device that measures blood pressure of a subject non-invasively using ultrasonic waves, and is used for a main body device 20, an ultrasonic probe 30 used for ultrasonic measurement, and electrocardiographic measurement. Two electrocardiographic electrodes 40 are provided.

  The ultrasonic probe 30 includes an ultrasonic transducer that transmits and receives an ultrasonic pulse signal or burst signal of several MHz to several tens of MHz, for example. For example, the ultrasonic probe 30 is attached to the left neck so that the ultrasonic transducer is located immediately above the carotid artery of the subject 2. Here, “directly above” is used in the expression of an operation manual for operating the ultrasonic probe 30 for easy understanding. To be precise, the ultrasonic probe 30 is used. This is a positional relationship in which the carotid artery is positioned on the ultrasonic irradiation line irradiated from the ultrasonic transducers arranged in a row.

  One of the two electrocardiographic electrodes 40 is formed integrally with the ultrasound probe 30, and the other electrocardiographic electrode 40 is attached to the lower part of the right clavicle of the subject 2.

  The main body device 20 is wired to the ultrasonic probe 30 and the electrocardiographic electrode 40, and measures the blood pressure of the subject 2 non-invasively using the ultrasonic probe 30 and the electrocardiographic electrode 40. Specifically, an ultrasonic wave is transmitted toward the blood vessel of the subject 2 using the ultrasonic probe 30, the blood vessel diameter is measured based on the received signal of the reflected wave, and the subject 2 is based on the measured blood vessel diameter. Blood pressure can be calculated. The method for calculating blood pressure from the blood vessel diameter is hereinafter referred to as “β method” as appropriate.

  In addition, the electrocardiogram waveform (ECG waveform) of the subject 2 is measured using the electrocardiogram electrode 40, the pulse wave propagation velocity PWV is calculated based on the measured electrocardiogram waveform, and based on the calculated pulse wave propagation velocity. The blood pressure of the subject 2 can also be calculated. The method for calculating the blood pressure from the pulse wave propagation velocity PWV is hereinafter referred to as “PWV method” as appropriate.

  As a feature of the present embodiment, the blood pressure is usually calculated from the blood vessel diameter (β method). However, when the measurement accuracy of the blood vessel diameter by the ultrasonic wave is low or lowered due to the body movement of the subject, the pulse is Switching to a method for calculating blood pressure from the wave propagation velocity PWV (PWV method).

  In calculating blood pressure based on the blood vessel diameter using ultrasonic waves, it is necessary to measure blood pressure for calibration separately from the blood vessel diameter. In this embodiment, a pressure sphygmomanometer 50 that can be connected to the ultrasonic blood pressure measurement device 10 is used for the calibration blood pressure measurement. The pressurized sphygmomanometer 50 wraps a cuff 52 for pressurization around the upper arm of the subject 2 to measure the blood pressure of the brachial artery of the subject 2 and transmits the measured value to the ultrasonic blood pressure measurement device 10. After the calibration, the cuff 52 is removed from the subject, and thereafter, the noninvasive blood pressure measurement of the subject 2 is performed using the ultrasonic probe 30.

[principle]
(A) Measurement of blood vessel diameter First, measurement of a blood vessel diameter using ultrasonic waves will be described. The blood vessel diameter can be calculated from the position of the blood vessel wall viewed from the ultrasonic probe 30, more specifically from the depth positions of the front wall and the rear wall of the blood vessel.

  FIG. 2 is a diagram for explaining the measurement of the position of the blood vessel wall and the diameter of the blood vessel by ultrasonic waves, and shows a cross-sectional view of the blood vessel 4 in the long axis direction. As shown in FIG. 2, in the measurement, the ultrasonic probe 30 is attached to the neck of the subject 2 so that the ultrasonic transducer 32 is in close contact with the skin surface directly above the blood vessel 4. Ultrasonic waves are transmitted from the ultrasonic transducer 32 in a downward direction (depth direction) in FIG. Ultrasonic waves have the property of being largely reflected at the boundary surface of the medium. That is, when the blood vessel 4 is located immediately below the ultrasonic transducer 32, a part of the ultrasonic wave transmitted from the ultrasonic transducer 32 is reflected on the front wall 4 a and the rear wall 4 b of the blood vessel 4. In the reflected wave signal in the ultrasonic transducer 32, strong reflected waves reflected by the front wall 4a and the rear wall 4b appear. The position of each of the front wall 4a and the rear wall 4b can be measured from the time difference from the transmission timing of the ultrasonic wave until the reflected waves of the front wall 4a and the rear wall 4b of the blood vessel 4 appear and the propagation speed of the ultrasonic wave. it can. And the blood vessel diameter D is calculated | required because the position of the front wall 4a and the rear wall 4b became clear.

(B) Correspondence Relationship between Blood Vessel Diameter and Blood Pressure Next, calculation of blood pressure based on the blood vessel diameter by the β method will be described. FIG. 3 is a graph showing the correspondence between the blood vessel diameter D and the blood pressure P. As shown in FIG. 3, there is a non-linear relationship between the blood vessel diameter D and the blood pressure P, which is expressed by the following equation (1). It is known that
P = Pd × exp [β (D / Dd−1)] (1)
However, β = ln (Ps / Pd) / (Ds / Ds−1) (2)
In equations (1) and (2), “Pd” is the diastolic blood pressure (minimum blood pressure), “Dd” is the diastolic blood vessel diameter, which is the blood vessel diameter at the time of the diastolic blood pressure, and “Ps” is the systolic blood pressure (maximum). Blood pressure), “Ds” is a systolic blood vessel diameter which is a blood vessel diameter at the time of systolic blood pressure, and “β” is a blood vessel elasticity index value called a stiffness parameter.

  That is, the blood pressure P can be calculated by substituting the blood vessel diameter D measured by the ultrasonic wave into the equation (1). This equation (1) is called a β blood pressure calculation equation. This β blood pressure calculation formula corresponds to the first relationship.

  However, in order to calculate the blood pressure P from the blood vessel diameter D using this equation (1), the constant diastolic blood pressure Pd, diastolic blood vessel diameter Dd, systolic blood pressure Ps, systolic blood vessel diameter Ds, and It is necessary to obtain a stiffness parameter β and perform calibration to define the equation (1). In the present embodiment, the diastolic blood vessel diameter Dd and the systolic blood vessel diameter Ds are measured using the ultrasonic probe 30, and the diastolic blood pressure Pd and the systolic blood pressure are measured using the pressurized sphygmomanometer 50. Ps is measured, and the stiffness parameter β defined by the equation (2) is obtained from the measured diastolic blood vessel diameter Dd, systolic blood vessel diameter Ds, diastolic blood pressure Pd, and systolic blood pressure Ps. Define. It should be noted that the blood pressure Pd and Ps for calibration need not be measured by the pressurized sphygmomanometer 50, and may of course be measured by another measuring means.

(C) Pulse Wave Propagation Speed Next, calculation of the pulse wave propagation speed will be described. FIG. 4 is a diagram for explaining the calculation of the pulse wave velocity PWV. FIG. 4 (1) is a fluctuation waveform of the vascular diameter of the carotid artery blood vessel during one heartbeat period, and FIG. 4 (2) is an electrocardiogram waveform during one heartbeat period, both of which are shown together with the time axis.

  One heartbeat period is composed of a systole and a diastole. In the systole period, the blood vessel diameter expands and swells, and in the diastole period, the blood vessel diameter gradually contracts and returns to its original thickness. As shown in FIG. 4 (1), the fluctuation of the blood vessel diameter is repeated for each heartbeat. Further, as shown in FIG. 4B, the electrocardiographic waveform sequentially includes a P wave due to atrial contraction, a Q wave due to ventricular contraction, an R wave and an S wave, and a T wave due to ventricular dilation.

  From the peak of the R wave in the electrocardiogram waveform of FIG. 4 (2) to the minimum blood vessel diameter in the blood vessel diameter fluctuation waveform of FIG. Time to reach (pulse wave propagation time) PTT. The pulse wave propagation speed PWV (= L / PTT) can be calculated from the pulse wave propagation time PTT and the distance L from the attachment location of the electrocardiographic electrode 40 to the attachment location of the ultrasonic probe 30.

(D) Correspondence Relationship between Pulse Wave Propagation Speed and Blood Pressure Next, calculation of blood pressure based on the pulse wave propagation speed by the PWV method will be described. FIG. 5 is a graph showing a correspondence relationship between the pulse wave velocity PWV and the blood pressure Ps. As shown in FIG. 5, it can be seen that the pulse wave velocity PWV and the systolic blood pressure Ps have a linear relationship. This relationship can be expressed by a linear expression shown in the following expression (3).
Ps = A × PWV + B (3)
In Expression (3), A and B are constants. That is, the systolic blood pressure Ps can be calculated by substituting the pulse wave velocity PWV obtained from the electrocardiogram waveform and the blood vessel diameter fluctuation waveform into this equation (3). This formula (3) is called a PWV blood pressure calculation formula. This PWV blood pressure calculation formula corresponds to the second relationship.

  For example, the least square method can be used for the calculation of the linear expression (3). In FIG. 5, only five points of sampling data are plotted, but more accurate relational expressions can be derived by obtaining more sampling data.

  However, the systolic blood pressure Ps is obtained by the PWV method. Diastolic blood pressure Pd cannot be obtained. Therefore, the diastolic blood pressure Pd is calculated using a formula obtained by changing the β blood pressure calculation formula (hereinafter referred to as “β blood pressure calculation change formula”). This β blood pressure calculation change formula corresponds to the first change relationship.

  FIG. 6 is a diagram for explaining the β blood pressure calculation change formula, and shows the correspondence between the blood vessel diameter D and the blood pressure P. In FIG. 6, a curve C1 is a β blood pressure calculation formula before the change. The measurement error (diameter error) is included in each of the expanded blood vessel diameter Dd1 and the contracted blood vessel diameter Ds1 by ultrasonic measurement, and the PWV method is used when the blood vessel diameter measurement accuracy is low. At this time, although the measurement accuracy of the blood vessel diameter is low, it can be estimated that the variation ΔD (= Ds1−Dd1) of the blood vessel diameter being tracked is relatively accurate. That is, it can be estimated that the measurement errors included in each of the expanded blood vessel diameter Dd1 and the contracted blood vessel diameter Ds1 are approximately the same. Therefore, the curve C1 is translated so as to pass through the intersection of the systolic blood pressure Ps obtained by the PWV method and the systolic blood vessel diameter Ds1 including an error. This is curve C2.

Therefore, the curve C2 is expressed by the following formula (4).
P = Ps1 × exp [β (D / Ds1-1)] (4)
In Expression (4), Ps1, Ds1, and β are constants, Ps1 is a systolic blood pressure calculated by substituting the pulse wave velocity PWV into Expression (3), and Ds1 is a systolic blood vessel obtained by ultrasonic measurement. The diameter, β, is a stiffness parameter defined by the equation (2). When the measurement accuracy of the blood vessel diameter is low, the blood pressure can be calculated by defining the equation (4) and substituting the blood vessel diameter (including the error) by the ultrasonic measurement into the equation (4). it can.

[Function configuration]
FIG. 7 is a functional configuration diagram of the ultrasonic blood pressure measurement device 10. According to FIG. 7, the ultrasonic blood pressure measurement device 10 includes an ultrasonic probe 30, electrocardiographic electrodes 40, 40, an operation unit 110, a display unit 120, a sound output unit 130, a communication unit 140, and a processing. Unit 200 and storage unit 300.

  The operation unit 110 is realized by an input device such as a button switch, a touch panel, or various sensors, and outputs an operation signal corresponding to the performed operation to the processing unit 200. The display unit 120 is realized by a display device such as an LCD (Liquid Crystal Display), and performs various displays according to display signals from the processing unit 200. The sound output unit 130 is realized by a sound output device such as a speaker, and outputs various sounds based on the sound signal from the processing unit 200. The communication unit 140 is realized by a wireless communication device such as a wireless local area network (LAN) or Bluetooth (registered trademark), and performs communication with an external device (mainly the pressurized sphygmomanometer 50).

  The processing unit 200 is realized by a microprocessor such as a CPU (Central Processing Unit) or DSP (Digital Signal Processor), an electronic component such as an ASIC (Application Specific Integrated Circuit) or an IC (Integrated Circuit) memory, and is stored in the storage unit 300. Various arithmetic processes are executed based on the programmed program and data, an operation signal from the operation unit 110, and the like, and the operation of the ultrasonic blood pressure measurement device 10 is controlled. In addition, the processing unit 200 includes an ultrasonic measurement control unit 202, an electrocardiogram measurement control unit 204, a blood vessel diameter measurement unit 206, a pulse wave propagation velocity calculation unit 208, a β blood pressure calculation formula generation unit 210, and a PWV blood pressure. The calculation formula generation unit 212, the β blood pressure calculation formula change unit 214, the reliability determination unit 216, the normal blood pressure calculation unit 218, and the temporary blood pressure calculation unit 220 are included.

  The ultrasonic measurement control unit 202 controls transmission / reception of ultrasonic waves in the ultrasonic probe 30. Specifically, ultrasonic waves are transmitted from the ultrasonic probe 30 at a transmission timing of a predetermined period. Also, amplification of the reflected wave signal of the ultrasonic wave received by the ultrasonic probe 30 is performed. Based on the reception signal of the reflected wave from the ultrasonic probe 30, ultrasonic measurement data 304 of each mode such as A mode, B mode, and M mode is generated.

  The electrocardiogram measurement control unit 204 measures electrocardiogram, which is an electrical fluctuation accompanying the heartbeat. Specifically, the potential difference between the two electrocardiographic electrodes 40 is amplified, converted into a digital signal, and the like. The electrocardiogram measured by the electrocardiogram measurement control unit 204 is stored as electrocardiogram measurement data 306.

  The blood vessel diameter measuring unit 206 calculates the blood vessel diameter based on the reception signal of the ultrasonic wave reflected by the ultrasonic probe 30. That is, reception of reflected waves from the front wall and the rear wall of the blood vessel is determined from the signal intensity of the received signal. The position (depth position) of each of the front wall and the rear wall is calculated using a time difference from the transmission timing of the ultrasonic wave to the reception timing of the reflected wave on each of the front wall and the rear wall. Then, the blood vessel diameter is calculated from the positions of the front wall and the rear wall (see FIG. 2).

  The calculation of the blood vessel diameter is performed at any time since transmission of ultrasonic waves and reception of reflected waves by the ultrasonic probe 30 is performed, so that a time interval that can be said to be almost real time of, for example, several milliseconds to tens of milliseconds. ) Repeat every time. Thereby, the waveform (refer FIG. 4 (1)) which shows the fluctuation | variation of the blood vessel diameter is obtained. The blood vessel diameter calculated by the blood vessel diameter measuring unit 206 is accumulated and stored as blood vessel diameter measurement data 308 in association with the measurement time.

  The pulse wave velocity calculation unit 208 calculates a pulse wave velocity PWV from the blood vessel diameter measured by the blood vessel diameter measurement unit 206 and the electrocardiogram waveform measured by the electrocardiogram measurement control unit 204. That is, the time from when the peak of the R wave appears in the electrocardiogram waveform measured by the electrocardiogram measurement control unit 204 until the minimum value appears in the fluctuation waveform of the blood vessel diameter measured by the blood vessel diameter measurement unit 206 Calculated as the wave propagation time PTT. Then, the pulse wave propagation speed PWV (= L / PTT) is calculated from the pulse wave propagation time PTT and a predetermined distance L between the ultrasonic probe 30 and the electrocardiographic electrode 40 (see FIG. 4). ). The pulse wave propagation velocity calculated by the pulse wave propagation velocity calculation unit 208 is accumulated and stored as pulse wave propagation velocity data 310.

  The β blood pressure calculation formula generation unit 210 generates a β blood pressure calculation formula for calculating the blood pressure P from the blood vessel diameter D. That is, from the systolic blood pressure Ps and the diastolic blood pressure Pd measured by the pressurized sphygmomanometer 50, the systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd measured by the blood vessel diameter measuring unit 206, an expression is obtained. By calculating the stiffness parameter β determined in (2), the equation (1) indicating the correspondence between the blood vessel diameter D and the blood pressure P is defined.

  The blood pressure measurement by the pressurized sphygmomanometer 50 requires several seconds to several tens of seconds. In addition, the systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd are obtained from the blood vessel diameter calculated by the blood vessel diameter measuring unit 206 in parallel with the blood pressure measurement by the pressurized sphygmomanometer 50. That is, the maximum value and the minimum value of the blood vessel diameter for each heartbeat are detected, the maximum value is set as the systolic blood vessel diameter Ds, and the minimum value is set as the diastolic blood vessel diameter Dd.

  The β blood pressure calculation formula calculated by the β blood pressure calculation formula generation unit 210 is stored as β blood pressure calculation formula data 314. Specifically, the β blood pressure calculation formula data 314 stores values of parameters β, Ds, Pd, and Dd that define the β blood pressure calculation formula (formula (1)).

  The PWV blood pressure calculation formula generation unit 212 generates a PWV blood pressure calculation formula for calculating the systolic blood pressure Ps from the pulse wave propagation speed PWV. That is, from the sampling data of the correspondence (PWV, Ps) between the plurality of pulse wave propagation speeds PWV and the systolic blood pressure Ps stored as the PWV blood pressure calculation formula generation database 318, the linear equation is obtained by the least square method or the like. An approximate expression is calculated. The PWV blood pressure calculation formula generated by the PWV blood pressure calculation formula generation unit 212 is stored as PWV blood pressure calculation formula data 316. Specifically, the PWV blood pressure calculation formula data 316 stores values of parameters A and B that define the PWV blood pressure calculation formula (formula (3)).

  Note that the correspondence (PWV, Ps) between the pulse wave velocity PWV and the systolic blood vessel diameter Ps stored in the PWV blood pressure calculation formula generation database 318 is determined by the reliability determination unit 216 as described below. It is a value calculated when it is determined that the condition is satisfied.

  The β blood pressure calculation formula change unit 214 changes the β blood pressure calculation formula generated by the β blood pressure calculation formula generation unit 210 to generate a β blood pressure calculation change formula. That is, the systolic blood pressure Ps1 calculated by substituting the pulse wave propagation velocity PWV calculated by the pulse wave propagation velocity calculation unit 208 into the PWV blood pressure calculation equation generation unit 212 and the blood vessel diameter The systolic blood vessel diameter Ds1 measured by the measuring unit 206 is replaced with the constants Pd and Dd in the β blood pressure calculation formula to obtain a β blood pressure calculation change formula. This β blood pressure calculation change unit corresponds to a first change relationship calculation unit.

  The reliability determining unit 216 determines whether or not the accuracy of the blood vessel diameter measured by the blood vessel diameter measuring unit 206 satisfies a given reliability condition. The reliability condition is a condition that the measurement accuracy of the blood vessel diameter by the ultrasonic wave is “good”. Specifically, the reception level (signal intensity) of the reflected wave of the ultrasonic wave from the vascular intima is a predetermined level or more. Suppose that

  When the reliability determination unit 216 determines that the reliability condition is satisfied, the normal blood pressure calculation unit 218 calculates the blood pressure from the blood vessel diameter by ultrasonic measurement. For example, the blood pressure is determined by substituting the blood vessel diameter measured by the blood vessel diameter measuring unit 206 into the β blood pressure calculation formula generated by the β blood pressure calculation formula generating unit 210. The normal blood pressure calculation unit 218 corresponds to a blood pressure determination unit. If the desired blood pressure is only the systolic blood pressure Ps and the diastolic blood pressure Pd, the β blood pressure calculation formula with the maximum blood vessel diameter of one heartbeat as the systolic blood vessel diameter Ds and the minimum blood vessel diameter as the diastolic blood vessel diameter Dd. By substituting into, systolic blood pressure Ps and diastolic blood pressure Pd can be determined. The blood pressures Ps and Pd calculated by the normal blood pressure calculation unit 218 are accumulated and stored as blood pressure calculation data 312 in association with the measurement time.

  The temporary blood pressure calculation unit 220 determines that the reliability condition is not satisfied by the reliability determination unit 216. However, when the fluctuation ΔD of the tracking blood vessel diameter can be measured and determined to be substantially constant, the pulse wave Blood pressure is calculated from the propagation speed. That is, for each heartbeat, the pulse wave propagation velocity PWV calculated by the pulse wave propagation velocity calculation unit 208 is substituted into the PWV blood pressure calculation equation generated by the PWV blood pressure calculation equation generation unit 212, and the systolic blood pressure Ps is calculated. calculate. Next, the minimum value of the blood vessel diameter measured by the blood vessel diameter measuring unit 206 is detected and set as the diastolic blood vessel diameter Dd, and this diastolic blood vessel diameter Dd is changed by the β blood pressure calculation formula changing unit 214. Substituting into the equation, diastolic blood pressure Pd is calculated. This temporary blood pressure calculation unit 220 corresponds to a blood pressure determination unit. The blood pressures Ps and Pd calculated by the temporary blood pressure calculation unit 220 are stored and stored as blood pressure calculation data 312 in association with the measurement time.

  The storage unit 300 is realized by a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a hard disk, and stores programs and data for the processing unit 200 to control the ultrasonic blood pressure measurement device 10 in an integrated manner. In addition to being stored, it is used as a work area of the processing unit 200, and temporarily stores calculation results executed by the processing unit 200, operation data from the operation unit 110, and the like. In this embodiment, the blood pressure measurement program 302, the ultrasonic measurement data 304, the electrocardiogram measurement data 306, the blood vessel diameter measurement data 308, the pulse wave velocity data 310, and the blood pressure calculation data 312 are stored in the storage unit 300. , Β blood pressure calculation formula data 314, PWV blood pressure calculation formula data 316, and PWV blood pressure calculation formula generation database 318 are stored. The storage unit 300 corresponds to a first relationship storage unit and a second relationship storage unit.

[Process flow]
FIG. 8 is a flowchart for explaining the flow of blood pressure measurement processing. This process is a process executed by the processing unit 200 according to the blood pressure measurement program 302, and is started when the start of blood pressure measurement is instructed by an external instruction or the like.

  First, the ultrasonic measurement control unit 202 starts ultrasonic measurement that causes the ultrasonic probe 30 to transmit and receive ultrasonic waves, and the blood vessel diameter measurement unit 206 measures the blood vessel diameter based on the received signal of the reflected ultrasonic wave. Start (step S1).

  Next, the processing unit 200 determines whether or not the β blood pressure calculation formula needs to be calibrated. For example, it is determined that calibration is necessary when the subject 2 performs blood pressure measurement with the apparatus for the first time or when a predetermined time has elapsed since the previous calibration.

  If calibration is necessary (step S3: YES), a message is displayed on the display unit 120, etc., the cuff 52 is attached to the subject 2, and blood pressure measurement by the pressurization sphygmomanometer 50 is instructed. The blood pressure measurement of the subject 2 by 50 is started, and the maximum blood pressure (systolic blood pressure) Ps and the minimum blood pressure (diastolic blood pressure) Pd are measured (step S5). Further, the blood vessel diameter measuring unit 206 calculates the systolic blood vessel diameter Ds and the diastolic blood vessel diameter Dd from the measured blood vessel diameter (step S7). When the blood pressure measurement by the pressurization sphygmomanometer 50 is completed, the β blood pressure calculation formula generation unit 210 determines the stiffness parameter from the blood vessel diameters Ds and Dd by the ultrasonic measurement and the blood pressures Ps and Pd measured by the pressurization sphygmomanometer 50. β is obtained, and the corresponding relational expression (1) between the blood vessel diameter and the blood pressure is calculated (step S9). This is the calibration.

  Subsequently, the electrocardiogram measurement control unit 204 starts electrocardiogram measurement (step S11). Further, the blood vessel diameter measuring unit 206 calculates the systolic blood vessel diameter Ds1 and the diastolic blood vessel diameter Dd1 for each heartbeat from the measured blood vessel diameter (step S13). Further, the pulse wave velocity calculation unit 208 calculates the pulse wave velocity PWV from the measured blood vessel diameter waveform and electrocardiogram waveform (step S15).

  Next, the reliability determination unit 216 determines whether it is possible to calculate blood pressure to which the β method is applied. Whether the β method is applicable is determined depending on whether the reliability condition is satisfied. If the β method can be applied (step S17: YES), the normal blood pressure calculation unit 218 substitutes the calculated systolic blood vessel diameter Ds1 and diastolic blood vessel diameter Dd1 into the β blood pressure calculation formula to perform contraction. The systolic blood pressure Ps1 and the diastolic blood vessel diameter Pd1 are calculated (step S19). The calculated blood pressures Ps1 and Pd1 are displayed together with the calculation method (in this case, the “β method”) (step S21). Further, the normal blood pressure calculation unit 218 accumulates and stores the calculated pulse wave propagation velocity PWV and the systolic blood pressure Ps1 in the PWV blood pressure calculation formula generation database 318 as new sampling data (step S23). .

  On the other hand, if the β method is not applicable (step S17: NO), it is subsequently determined whether it is possible to calculate blood pressure using the PWV method. Whether or not the PWV method is applicable is determined based on whether or not the blood vessel diameter variation ΔD can be measured by phase difference tracking or the like.

  If the PWV method is applicable (step S27: YES), the temporary blood pressure calculation unit 220 calculates the systolic blood pressure Ps2 by substituting the calculated systolic blood vessel diameter Ds1 into the PWV blood pressure calculation formula (step S29). ). Next, the β blood pressure calculation formula changing unit 214 changes the β blood pressure calculation formula using the calculated systolic blood vessel diameter Ds1 and the systolic blood pressure Ps2, thereby generating a β blood pressure calculation changing formula (step S31). ). Subsequently, the extraordinary blood pressure calculation unit 220 calculates the diastolic blood pressure Pd2 by substituting the calculated diastolic blood vessel diameter Dd1 into the generated β blood pressure calculation change formula (step S33). The calculated blood pressures Ps2 and Pd2 are displayed and controlled together with a calculation method (in this case, “PWV method”) (step S35).

  Thereafter, the processing unit 200 determines whether or not blood pressure measurement is to be terminated by an external instruction or the like, and if not (step S37: NO), returns to step S13. If the blood pressure measurement is to be ended (step S37: YES), the ultrasonic measurement control unit 202 ends the ultrasonic measurement, the blood vessel diameter measurement unit 206 ends the blood vessel diameter measurement (step S39), and the electrocardiogram measurement. The control unit 204 ends the electrocardiogram measurement (step S41). When the above process is performed, the blood pressure measurement process ends.

[Function and effect]
As described above, according to the ultrasonic blood pressure measurement device 10 of the present embodiment, when the measurement accuracy of the blood vessel diameter by ultrasonic waves is reduced, the pulse wave velocity PVW and the β blood pressure calculation formula (formula (1)) are calculated. The blood pressure can be calculated using the changed β blood pressure calculation change formula (formula (4)).

[Modification]
It should be noted that embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

(A) Pulse wave velocity PWV
For example, the systolic blood pressure Ps may be calculated using the pulse wave propagation time PTT instead of the pulse wave propagation speed PWV. In this case, instead of the correspondence equation (3) between the pulse wave propagation velocity PWV and the systolic blood pressure Ps, a correspondence relationship between the pulse wave propagation time PTT and the systolic blood pressure Ps is determined, and this correspondence relationship and the pulse wave propagation time are determined. The systolic blood pressure Ps is calculated from the PTT.

(B) ECG electrode 40
In the above-described embodiment, one of the two electrocardiographic electrodes 40 is formed to be the same as the ultrasonic probe 30, but may not be formed to be the same as the ultrasonic probe 30. In that case, the two electrocardiographic electrodes 40 and 40 are configured separately from the ultrasonic probe 30.

(C) PWV blood pressure calculation formula In addition, although the corresponding relational expression (formula (3)) between the pulse wave propagation velocity PWV and the systolic blood pressure Ps is a linear function (primary formula) (see FIG. 5), a nonlinear function (approximate) Curve).

(D) PWV Blood Pressure Calculation Formula In addition, the PWV blood pressure calculation formula is determined using the correspondence between the pulse wave velocity PWV and the systolic blood pressure Ps, but not the systolic blood pressure Ps but the diastolic blood pressure Pd or the average. The PWV blood pressure calculation formula may be determined using the correspondence relationship with the blood pressure.

(E) Measurement target blood vessel The blood vessel to be subjected to ultrasonic measurement is the carotid artery, but other blood vessels such as the brachial artery, radial artery, femoral artery, subclavian artery, aorta, etc. are measured blood vessels. Also good.

2 subjects, 4 blood vessels, 4a front wall, 4b rear wall, 10 ultrasonic measuring device, 20 main body device, 30 ultrasonic probe, 32 ultrasonic transducer, 40 electrocardiographic electrode, 110 operation unit, 120 display unit, 130 sound Output unit, 140 communication unit, 200 processing unit, 202 ultrasound measurement control unit, 204 electrocardiogram measurement control unit, 206 blood vessel diameter measurement unit, 208 pulse wave propagation velocity calculation unit, 210 β blood pressure calculation formula generation unit, 212 PWV blood pressure Calculation formula generation unit, 214 β blood pressure calculation formula change unit, 216 reliability determination unit, 218 normal blood pressure calculation unit, 220 temporary blood pressure calculation unit, 300 storage unit, 302 blood pressure measurement program, 304 ultrasound measurement data, 306 electrocardiogram measurement Data, 308 blood vessel diameter measurement data, 310 pulse wave velocity data, 312 blood pressure calculation data, 314 β blood pressure calculation formula data, 316 WV blood pressure calculation formula data, 318 PWV blood pressure calculation formula generating database, 50 pressure sphygmomanometer, 52 cuff

Claims (6)

An ultrasonic blood pressure measurement device that measures blood pressure by transmitting ultrasonic waves toward a blood vessel and receiving reflected waves,
A first relationship storage unit for storing a first relationship between the blood vessel diameter and blood pressure of the blood vessel;
A pulse wave velocity measuring unit for measuring the pulse wave velocity of the blood vessel;
A first change relationship calculation unit that calculates a first change relationship in which the first relationship is changed based on the pulse wave velocity;
A blood pressure determining unit that measures a blood vessel diameter of the blood vessel by the ultrasonic wave, and determines a blood pressure from the blood vessel diameter based on the first change relationship;
An ultrasonic blood pressure measurement device comprising: A second relationship storage unit that stores a second relationship between the pulse wave velocity and the blood pressure;
The ultrasonic blood pressure measurement device according to claim 1, further comprising: The second relationship is a correspondence relationship between the pulse wave velocity and systolic blood pressure,
The first change relationship calculating unit obtains systolic blood pressure from the pulse wave propagation velocity measured by the pulse wave velocity measuring unit and the second relationship, and measured by the systolic blood pressure and the ultrasound. Calculating the first change relationship by changing the first relationship using the systolic vessel diameter of the blood vessel;
The ultrasonic blood pressure measurement device according to claim 2. A blood pressure determination unit that determines a blood pressure from the measured blood vessel diameter and the first relationship when the blood vessel diameter measurement of the blood vessel by the ultrasonic wave satisfies a predetermined reliability condition;
With
The blood pressure determination unit functions when the predetermined reliability condition is not satisfied.
The ultrasonic blood pressure measurement device according to any one of claims 1 to 3. A blood pressure measurement method for measuring blood pressure by transmitting an ultrasonic wave toward a blood vessel and receiving a reflected wave,
Measuring the pulse wave velocity of the blood vessel;
Using the pulse wave propagation velocity to calculate a first change relationship in which a first relationship between a predetermined blood vessel diameter and blood pressure is changed;
Measuring a blood vessel diameter of the blood vessel by the ultrasonic wave, and determining a blood pressure from the blood vessel diameter based on the first change relationship;
Blood pressure measurement method including Storing a second relationship between the pulse wave velocity and blood pressure;
The blood pressure measurement method according to claim 5, comprising:

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