JP6060649B2 - Blood pressure measurement device and blood pressure measurement method - Google Patents

Description

  The present invention relates to an apparatus for measuring a blood pressure of a subject.

  Conventionally, an apparatus for measuring blood flow, blood vessel diameter, and blood pressure using ultrasonic waves has been devised. For example, Patent Document 1 discloses a method for estimating blood pressure from a stiffness parameter representing the hardness of a blood vessel and a blood vessel diameter, taking a change in blood vessel diameter and a change in blood pressure as a non-linear relationship.

JP 2004-41382 A

  The technique disclosed in Patent Document 1 is a technique for calculating blood pressure based on a correlation characteristic between a blood vessel diameter and blood pressure. However, in relatively thin arteries such as limb arteries, the blood vessels are stiff, and therefore the variation in blood vessel diameter with respect to changes in blood pressure is negligible.

  For example, in the radial artery flowing through the wrist, the change in blood pressure accompanying pulsation is about 50 [mmHg], while the change in blood vessel diameter is about 40 [μm]. Therefore, for example, in order to calculate the blood pressure with an accuracy of 10 [mmHg], a blood vessel diameter measuring method capable of measuring in a unit of at least 8 [μm] is required. However, a blood vessel diameter measuring method that achieves this accuracy is considered difficult in practice.

  The present invention has been made in view of the above-described problems, and an object thereof is to propose a new technique for improving blood pressure measurement accuracy.

  A first invention for solving the above problems is a blood vessel diameter measuring unit that measures a blood vessel diameter of a blood vessel to be measured in a measurement target portion, and a first state and a second state in which the internal and external pressure differences between the measurement target blood vessels are different. A blood vessel that is a difference between the first blood vessel diameter and the second blood vessel diameter measured by the blood vessel diameter measuring unit in the first state and the second state, and a state maintenance control unit that performs control for sequentially maintaining the measurement target region Using the difference in diameter, the correlation between the blood pressure and the blood vessel diameter of the blood vessel to be measured, and the differential pressure between the internal / external pressure difference in the first state and the internal / external pressure difference in the second state, the blood pressure of the subject A blood pressure measurement device comprising: a blood pressure estimation unit that estimates

  As another invention, the first blood vessel diameter measured at the time of measuring the blood vessel diameter of the blood vessel to be measured in the measurement target portion, and the first state and the second state in which the internal / external pressure difference of the blood vessel to be measured is different, and A blood vessel diameter difference that is a difference between the second blood vessel diameters, a correlation characteristic between blood pressure and a blood vessel diameter of the blood vessel to be measured, and a differential pressure between an internal / external pressure difference in the first state and an internal / external pressure difference in the second state It is good also as comprising the blood pressure measurement method including estimating the blood pressure of a subject using.

  According to the first invention and the like, the diameter of the measurement target blood vessel in the measurement target region is measured. And the blood vessel diameter difference that is the difference between the first blood vessel diameter and the second blood vessel diameter measured in the first state and the second state where the internal and external pressure differences of the measurement target blood vessels are different, and the blood pressure and the blood vessel diameter of the measurement target blood vessel By using the correlation characteristic and the differential pressure between the internal / external pressure difference in the first state and the internal / external pressure difference in the second state, the blood pressure of the subject can be estimated more accurately than in the past.

  Further, as a second invention, the blood pressure estimation unit in the blood pressure measurement device according to the first invention has a characteristic value matching the relationship between the blood pressure difference and the blood vessel diameter difference in which the differential pressure is regarded as a blood pressure difference. A blood pressure measurement device that includes a characteristic value search unit that searches from the correlation characteristic and estimates the blood pressure of the subject based on the searched characteristic value may be configured.

  According to the second aspect of the invention, a characteristic value that matches the relationship between the blood pressure difference and the blood vessel diameter difference, which is regarded as a blood pressure difference, is searched from the correlation characteristic. You can find out. The blood pressure estimation accuracy can be improved by estimating the blood pressure of the subject based on the characteristic value searched in this way.

  Further, as a third invention, the characteristic value search unit in the blood pressure measurement device according to the second invention is based on the blood vessel diameter measured by the blood vessel diameter measurement unit when the measurement target part is in a non-pressurized state. It is good also as comprising a blood pressure measuring device which has a search range setting part which sets a search range among the correlation characteristics, and searches for the characteristic value within the set search range.

  According to the third aspect of the invention, the search range is set based on the blood vessel diameter measured when the measurement target part is in the non-pressurized state. Then, the characteristic value is searched for within the set search range. The blood vessel diameter measured when the measurement target region is in the non-pressurized state can be considered as a value that can be trusted to some extent. Therefore, for example, a predetermined range centered on the blood vessel diameter is set as a search range, and a characteristic value is searched for within this search range. As a result, it is possible to appropriately search for the characteristic value while reducing the amount of calculation.

  As a fourth invention, in the blood pressure measurement device according to any one of the first to third inventions, the first blood vessel diameter and the second blood vessel diameter are diastolic blood vessel diameters, and Using the characteristic, the blood vessel diameter difference, and the differential pressure, the diastolic blood pressure estimation unit that estimates the diastolic blood pressure of the subject, the diastolic blood pressure, and the blood vessel diameter measured by the blood vessel diameter measurement unit A blood pressure measurement device having a systolic blood pressure estimation unit that estimates the systolic blood pressure of the subject using the fluctuation range associated with the pulsation and the correlation characteristic may be configured.

  According to the fourth aspect of the invention, the diastolic blood pressure of the subject is estimated using the correlation characteristic, the blood vessel diameter difference, and the differential pressure. Then, the systolic blood pressure of the subject is estimated using the diastolic blood pressure, the fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measuring unit, and the correlation characteristics. Therefore, if the diastolic blood pressure can be estimated, the systolic blood pressure of the subject can be derived from the fluctuation range accompanying the pulsation of the blood vessel diameter and the correlation characteristics.

  As a fifth invention, in the blood pressure measurement device according to any one of the first to third inventions, the first blood vessel diameter and the second blood vessel diameter are systolic blood vessel diameters, Using the characteristic, the blood vessel diameter difference, and the differential pressure, the systolic blood pressure estimating unit that estimates the systolic blood pressure of the subject, the systolic blood pressure, and the blood vessel diameter measured by the blood vessel diameter measuring unit The blood pressure measuring device may include a diastolic blood pressure estimation unit that estimates the diastolic blood pressure of the subject using the fluctuation range associated with the pulsation of the subject and the correlation characteristics.

  According to the fifth aspect of the invention, the systolic blood pressure of the subject is estimated using the correlation characteristic, the blood vessel diameter difference, and the differential pressure. Then, the diastolic blood pressure of the subject is estimated using the systolic blood pressure, the fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measuring unit, and the correlation characteristics. Therefore, if the systolic blood pressure can be estimated, the diastolic blood pressure of the subject can be derived from the fluctuation range accompanying the pulsation of the blood vessel diameter and the correlation characteristics.

  Further, as a sixth invention, in the blood pressure measurement device according to any one of the first to fifth inventions, a pressurizing unit that applies an external pressure to the measurement target part, and a pressure pressurized by the pressurizing unit are detected. A pressure detection unit, wherein the state maintenance control unit controls the pressurization unit, and the blood pressure estimation unit is a first detected by the pressure detection unit in the first state and the second state. A blood pressure measurement device having a differential pressure calculation unit that calculates the differential pressure using the pressure and the second pressure may be configured.

  According to the sixth aspect of the invention, the external pressure is applied to the measurement target portion by the pressurizing unit. Moreover, the pressure pressurized by the pressurization part is detected by the pressure detection part. Since the pressurizing unit applies an external pressure to the measurement target region, it is possible to easily create two states with different internal and external pressure differences of the measurement target blood vessel and estimate the blood pressure of the subject.

  Further, as a seventh invention, the state maintenance control unit in the blood pressure measurement device according to the sixth invention changes at least one of the first state and the second state based on an estimation result of the blood pressure estimation unit. The re-control of the pressurizing unit is executed, and the blood pressure estimating unit uses the blood vessel diameter difference and the differential pressure at the time of the first state and the second state changed by the re-control. A blood pressure measurement device that re-estimates blood pressure may be configured.

  According to the seventh aspect of the invention, re-control of the pressurizing unit that changes at least one of the first state and the second state is executed based on the estimation result of the blood pressure estimation unit. Then, the blood pressure of the subject is re-estimated using the blood vessel diameter difference and the differential pressure in the first state and the second state changed by re-control. For example, when the estimation result of the blood pressure estimation unit clearly shows an incorrect value, at least one of the first state and the second state is changed, re-control is executed, and the blood pressure of the subject is Re-estimated. For this reason, a user's effort at the time of calculating | requiring more probable blood pressure can be skipped.

The schematic block diagram of an ultrasonic sphygmomanometer. Explanatory drawing of the correlation characteristic of a blood vessel diameter and blood pressure. Explanatory drawing of the principle of blood pressure estimation. Explanatory drawing of the principle of blood pressure estimation. The block diagram which shows an example of a function structure of an ultrasonic sphygmomanometer. The flowchart which shows the flow of a main process. The flowchart which shows the flow of an ultrasonic blood pressure measurement process. The flowchart which shows the flow of a blood-pressure estimation process. The figure which shows the modification of the function part of a process part. The flowchart which shows the flow of a 2nd blood pressure estimation process. The flowchart which shows the flow of a 3rd blood pressure estimation process. The flowchart which shows the flow of a 2nd ultrasonic blood pressure measurement process.

  As an embodiment to which the present invention is applied, an embodiment of a blood pressure measurement device that measures the blood pressure of a subject using the subject's upper arm as a measurement target region and the measurement target blood vessel as a brachial artery will be described. In the present embodiment, the blood pressure measurement device is calibrated by calculating a parameter related to blood pressure estimation (hereinafter referred to as “blood pressure estimation parameter”). In the present specification, calculating the value of the blood pressure estimation parameter is referred to as calibration of the blood pressure estimation parameter.

1. Schematic Configuration FIG. 1 is a configuration diagram of a system related to blood pressure measurement according to the present embodiment. This blood pressure measurement system includes an ultrasonic sphygmomanometer 1 that can be used by being attached to the upper arm of one arm, and a cuff sphygmomanometer 3 that is wound around the upper arm of the other arm and used. It is comprised.

  The cuff type sphygmomanometer 3 wraps a cuff that senses blood pressure around the upper arm of the subject and measures the blood pressure of the brachial artery. In the present embodiment, the cuff sphygmomanometer 3 is used for calibrating the ultrasonic sphygmomanometer 1. After the calibration, the cuff type sphygmomanometer 3 is removed, and the blood pressure is measured using the ultrasonic sphygmomanometer 1 alone.

  The ultrasonic sphygmomanometer 1 includes a pressurizing unit 30 having a cuff belt and a pressurizing mechanism for sending air into the cuff belt to pressurize the upper arm, and isotropically pressurizes a measurement target portion of the subject. It is configured to be possible. The main body of the ultrasonic sphygmomanometer 1 is provided with an operation button 12, a liquid crystal display 13, and a speaker 14.

  The operation button 12 is used by the subject to input a blood pressure measurement start instruction and various amounts related to blood pressure measurement.

  The liquid crystal display 13 displays the blood pressure measurement result by the ultrasonic sphygmomanometer 1. As a display method, the blood pressure measurement value may be displayed as a numerical value, or may be displayed as a graph or the like.

  From the speaker 14, various kinds of voice guidance related to blood pressure measurement are output as sound. In the present embodiment, it is necessary to measure blood pressure with the cuff type sphygmomanometer 3 in order to calibrate the ultrasonic sphygmomanometer 1. Therefore, for example, a voice guidance for instructing attachment / detachment of the cuff type sphygmomanometer 3 may be output from the speaker 14.

  An ultrasonic sensor 20 is provided inside the main body of the ultrasonic sphygmomanometer 1 and on the left side of the main body as viewed from the subject side. When the ultrasonic sphygmomanometer 1 is attached, the ultrasonic sensor 20 is positioned so that the ultrasonic sensor 20 is positioned immediately above the brachial artery of the subject. The ultrasonic sensor 20 is an ultrasonic transmission / reception unit in which ultrasonic transducers are arranged in an array, and transmits an ultrasonic pulse signal or burst signal of several MHz to several tens of MHz toward the brachial artery from the transmission unit. . Then, reflected waves from the anterior wall and the posterior wall of the brachial artery are received by the receiving unit, and the blood vessel diameter of the brachial artery is measured from the reception time difference between the reflected waves of the anterior wall and the posterior wall.

  Although not shown, the main body of the ultrasonic sphygmomanometer 1 incorporates a control board for controlling the devices in an integrated manner. On the control board, a microprocessor, a memory, a circuit for transmitting and receiving ultrasonic waves, a power supply circuit, and the like are mounted.

  The ultrasonic sphygmomanometer 1 and the cuff sphygmomanometer 3 are configured to be able to exchange measurement data using, for example, short-range wireless communication. Specifically, the blood pressure measured at the upper arm using the cuff type sphygmomanometer 3 is transmitted to the ultrasonic sphygmomanometer 1 using short-range wireless communication. Then, the ultrasonic sphygmomanometer 1 calibrates its own device by calculating the value of the blood pressure estimation parameter using the blood vessel diameter measured using the ultrasonic wave and the blood pressure received from the cuff type sphygmomanometer 3.

2. Principle The upper arm of the subject is pressurized by the pressurizing unit 30 of the ultrasonic sphygmomanometer 1, and the brachial artery is isotropically compressed. With the compression of the brachial artery, the internal / external pressure difference of the brachial artery changes. In this embodiment, paying attention to this characteristic, the pressurizing unit 30 is controlled so that two different external pressures are applied to the brachial artery. And the pressure pressurized by the pressurization part 30 is detected, and the differential pressure | voltage of the 1st pressure detected in this case and a 2nd pressure is calculated. Then, a correlation characteristic between a blood vessel diameter difference that is a difference between the first blood vessel diameter and the second blood vessel diameter measured using ultrasonic waves when the first pressure and the second pressure are applied, and the blood pressure and the blood vessel diameter of the brachial artery. The blood pressure of the subject is estimated using the calculated differential pressure.

FIG. 2 is a diagram illustrating an example of a correlation characteristic between a blood vessel diameter and blood pressure. The blood vessel diameter and blood pressure can be linked with a certain nonlinear correlation characteristic. Specifically, using the pressure applied to the blood vessel and the blood vessel diameter at each blood pressure, for example, the correlation characteristic can be expressed by a correlation equation such as the following equation (1).
P = Pd · exp [β (D / Dd−1)] (1)
Where β = ln (Ps / Pd) / (Ds / Dd−1)

  However, “Ps” is systolic blood pressure (maximum blood pressure), and “Pd” is diastolic blood pressure (minimum blood pressure). “Ds” is a systolic blood vessel diameter that is a blood vessel diameter at the time of systolic blood pressure, and “Dd” is a diastolic blood vessel diameter that is a blood vessel diameter at the time of diastolic blood pressure. “Β” is a vascular elasticity index value called a stiffness parameter. In the present embodiment, this stiffness parameter “β” will be described as a blood pressure estimation parameter.

  In FIG. 2, the coordinate value composed of the diastolic blood vessel diameter and blood pressure in a state where the measurement target blood vessel is pressurized with the first pressure (hereinafter, referred to as “first state”) is correlated as a black circle coordinate value P1. Plot on the formula. In addition, a coordinate value composed of a diastolic blood vessel diameter and blood pressure in a state where the measurement target blood vessel is pressurized with the second pressure (hereinafter referred to as “second state”) is expressed as a white circle coordinate value P2 in the correlation equation. Is plotted. Here, the second pressure is described as a pressure higher than the first pressure. That is, the second state will be described as a state in which the measurement target blood vessel is strongly pressurized compared to the first state.

  In the second state, compared to the first state, a stronger pressure is applied to the measurement target blood vessel from the outside, and therefore the internal pressure of the measurement target blood vessel becomes lower. Therefore, the blood pressure at point P2 is lower than that at point P1. This decrease in blood pressure corresponds to the differential pressure “ΔPo” between the first pressure and the second pressure. “ΔDHd” includes a diastolic blood vessel diameter “Dd1” in the first state (hereinafter referred to as “first diastolic blood vessel diameter”) and a diastolic blood vessel diameter “Dd2” in the second state (hereinafter referred to as “ (Referred to as “second diastolic blood vessel diameter”) (hereinafter referred to as “diastolic blood vessel diameter difference”). The diastolic blood vessel diameter difference “ΔDHd” can be measured using ultrasonic waves.

  In FIG. 2, the coordinate value composed of the blood vessel diameter and blood pressure in the systole in the first state is plotted on the correlation equation as the coordinate value Q1 of the black triangle. Also, the coordinate value composed of the diastolic blood vessel diameter and blood pressure in the second state is plotted on the correlation equation as the coordinate value Q2 of the white triangle. Regarding the systolic blood pressure, the systolic blood pressure in the second state is lower by the differential pressure “ΔPo”.

  “ΔDHs” includes a systolic blood vessel diameter “Ds1” (hereinafter referred to as “first systolic blood vessel diameter”) in the first state and a systolic blood vessel diameter “Dd2” (hereinafter referred to as “first systolic blood vessel diameter”). (Referred to as “second systolic blood vessel diameter”) (hereinafter referred to as “systolic blood vessel diameter difference”). The systolic blood vessel diameter difference “ΔDHs” can be measured using ultrasonic waves.

  The purpose of this embodiment is to estimate the blood pressure of the subject. As a blood pressure estimation method, (A) firstly estimating diastolic blood pressure and estimating systolic blood pressure using the estimated diastolic blood pressure; and (B) first estimating and estimating systolic blood pressure. There is a method for estimating diastolic blood pressure using systolic blood pressure. Here, a case where blood pressure is estimated using the method (A) will be described. Although details will be described later in a modification, it is a matter of course that blood pressure may be estimated using the method (B).

  FIG. 3 is an explanatory diagram of a method for estimating diastolic blood pressure. Consider an L-shaped pattern having the diastolic blood vessel diameter difference “ΔDHd” described in FIG. 2 as a base and the differential pressure “ΔPo” as a height. Specifically, consider a pattern as shown at the top of the graph of FIG. At this time, the vertex of the line segment having the height of the differential pressure “ΔPo” is defined as the characteristic value R, and the value corresponding to the leftmost point of the line segment having the base of the diastolic blood vessel diameter difference “ΔDHd” as the characteristic value S. .

  At this time, for example, while the characteristic value R is slid on the correlation equation, the characteristic value R and the characteristic value S that minimize the error in the blood vessel radial direction are searched. That is, a characteristic value that matches the relationship between the blood pressure difference and the blood vessel diameter difference in which the differential pressure is regarded as a blood pressure difference is searched from the correlation characteristics. Then, the blood pressure of the subject is estimated based on the searched characteristic value.

  This will be specifically described. The blood vessel diameter corresponding to the characteristic value R is “Dd1”, and the blood vessel diameter corresponding to the characteristic value S is “Dd2”. The blood pressure corresponding to the characteristic value R is “P”. Further, the blood vessel diameter corresponding to the coordinate value obtained by substituting the blood pressure “P−ΔPo” obtained by subtracting the differential pressure “ΔPo” from the blood pressure “P” into the correlation equation is set to “Dd3”. At this time, the diastolic error is defined by “Ed = Dd2−Dd3”, and the characteristic value R is slid on the correlation equation so as to reduce the diastolic error “Ed”.

  In FIG. 3, the characteristic value R1 is the diastolic error “Ed> 0”, and the absolute value thereof is also relatively large. When the characteristic value is slid from R1 to R2, the absolute value of the diastolic error “Ed” becomes smaller than that of the characteristic value R1. Further, when the characteristic value is slid from R2 to R3, the diastolic error “Ed” becomes almost zero. When the characteristic value is slid further upward from this state, the diastolic error “Ed” becomes a negative value. When the characteristic value is slid upward along the correlation formula (R4 and R5), the absolute value of the diastolic error “Ed” gradually increases.

  Thus, by searching for a characteristic value that minimizes the absolute value of the diastolic error “Ed” while changing the blood pressure value on the correlation equation, the differential pressure “ΔPo” and the diastolic blood vessel diameter difference “ΔDHd” are obtained. ”Can be obtained. In FIG. 3, the characteristic values R3 and S3 are characteristic values that minimize the absolute value of the diastolic error “Ed”. Therefore, in this case, the blood pressure corresponding to the characteristic value R3 is estimated as the diastolic blood pressure.

  In the above description, the diastolic error is defined as “Ed = Dd2−Dd3” with respect to the blood vessel radial direction (horizontal axis direction in FIG. 3), and the blood pressure difference and the blood vessel diameter difference are defined using the diastolic error as an index value. Although a characteristic value that matches the relationship is searched from the correlation characteristic, the index value is not limited to this. For example, the diastolic error is similarly defined for the blood pressure direction (vertical axis direction in FIG. 3) instead of the blood vessel diameter direction, and a characteristic value that minimizes the diastolic error defined for the blood pressure direction is searched. Also good.

  FIG. 4 is an explanatory diagram of a method for estimating systolic blood pressure. If the diastolic blood pressure is estimated according to the principle described in FIG. 3, the blood vessel diameter corresponding to the estimated diastolic blood pressure estimated value, which is the estimated diastolic blood pressure, is obtained from the correlation formula and is set as the diastolic blood vessel diameter. Next, the blood vessel diameter fluctuation amount “ΔD” accompanying pulsation is measured using ultrasonic waves. The blood vessel diameter obtained by adding the blood vessel diameter fluctuation amount “ΔD” to the diastolic blood vessel diameter is defined as the systolic blood vessel diameter. Finally, the blood pressure obtained by substituting the systolic blood vessel diameter into the correlation equation is estimated as the systolic blood pressure, and this is used as the systolic blood pressure estimated value.

3. Functional Configuration FIG. 5 is a block diagram illustrating an example of a functional configuration of the ultrasonic sphygmomanometer 1. The ultrasonic sphygmomanometer 1 includes a processing unit 100, an ultrasonic sensor 20, a pressurizing unit 30, an operation unit 200, a display unit 300, a sound output unit 400, a communication unit 500, a clock unit 600, And a storage unit 800.

  The ultrasonic sensor 20 is an ultrasonic transmission / reception unit and includes an ultrasonic transmission / reception circuit. For example, according to the transmission / reception control signal output from the transmission / reception control unit 120, the transmission / reception circuit transmits and receives ultrasonic waves by switching between the ultrasonic transmission mode and the reception mode in a time division manner.

  The transmission / reception circuit includes an ultrasonic oscillation circuit that generates a pulse signal of a predetermined frequency, a transmission delay circuit that delays the generated pulse signal, and the like as a configuration for transmission. The reception configuration includes a reception delay circuit that delays the reception signal, a filter that extracts a predetermined frequency component from the reception signal, an amplifier that amplifies the reception signal, and the like.

  The pressurizing unit 30 pressurizes the measurement target site of the subject. In the present embodiment, the pressurizing unit 30 includes a cuff belt and a pressurizing mechanism for sending air into the cuff belt and compressing the measurement target region. The pressurization unit 30 performs a pressurization operation according to the pressurization control signal output from the processing unit 100, and outputs a pressurization signal indicating a pressurization state to the processing unit 100.

  The processing unit 100 is a control device and an arithmetic device that comprehensively control each unit of the ultrasonic sphygmomanometer 1, and is a microprocessor such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), or an ASIC (Application Specific Integrated). Circuit) and the like.

  The processing unit 100 includes a transmission / reception control unit 120, a blood vessel diameter calculation unit 130, a blood pressure estimation unit 140, a pressurization control unit 150, and a pressure detection unit 160 as main functional units. However, these functional units are only described as one embodiment, and all the functional units are not necessarily required as essential components. It is also possible to add functional units other than these as essential components.

  The transmission / reception control unit 120 controls transmission / reception of ultrasonic waves by the ultrasonic sensor 20. Specifically, a transmission / reception control signal is output to the ultrasonic sensor 20, and control for switching between the transmission mode and the reception mode is performed.

  The blood vessel diameter calculation unit 130 calculates the blood vessel diameter of the blood vessel to be measured based on the signal processing result input from the ultrasonic sensor 20. Specifically, the blood vessel diameter of the measurement target blood vessel is calculated by detecting the reception time difference between the reflected waves of the ultrasonic waves from the front wall and the rear wall of the measurement target blood vessel.

  The ultrasonic sensor 20, the transmission / reception control unit 120, and the blood vessel diameter calculation unit 130 constitute a blood vessel diameter measurement unit 110 that measures the blood vessel diameter of the measurement target blood vessel in the measurement target region. The blood vessel diameter measuring unit 110 is configured to continuously measure the blood vessel diameter. As a technique for continuously measuring the blood vessel diameter, for example, a phase difference tracking method can be applied. In addition, since the phase difference tracking method itself is conventionally well-known, description is abbreviate | omitted for the detail.

  The blood pressure estimation unit 140 uses the blood vessel diameter measured by the blood vessel diameter measurement unit 110 and the correlation equation 821 representing the correlation characteristic between the blood pressure and the blood vessel diameter stored in the calibration data 820 to calculate the blood pressure of the subject. presume. The blood pressure estimation unit 140 includes a diastolic blood pressure estimation unit 141 that estimates diastolic blood pressure, and a systolic blood pressure estimation unit 143 that estimates systolic blood pressure. Further, a differential pressure calculation unit 145 that calculates a differential pressure between the internal and external pressures using the first pressure and the second pressure detected by the pressure detection unit 160 in the first state and the second state, and a blood pressure difference and a blood vessel diameter difference And a characteristic value search unit 147 that searches for a characteristic value that matches the relationship from the correlation characteristic.

  The pressurization control unit 150 controls pressurization of the measurement target portion by the pressurization unit 30. Specifically, a pressurization control signal is output to the pressurization unit 30 to control the start, stop, and end of the pressurization operation by the pressurization unit 30. The pressurization control unit 150 can be said to be a kind of state maintenance control unit that performs control to sequentially maintain the measurement target region in the first state and the second state in which the internal and external pressure differences of the measurement target blood vessels are different.

  The pressure detector 160 detects the pressure pressurized by the pressurization unit 30 in accordance with the pressurization signal output from the pressurization unit 30.

  The operation unit 200 is an input device having a button switch or the like, and outputs a signal of a pressed button to the processing unit 100. By operating the operation unit 200, various instructions such as a blood pressure measurement start instruction are input. The operation unit 200 corresponds to the operation button 12 in FIG.

  The display unit 300 includes an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on a display signal input from the processing unit 100. Information such as an estimated value of blood pressure estimated by the blood pressure estimation unit 140 is displayed on the display unit 300. The display unit 300 corresponds to the liquid crystal display 13 of FIG.

  The sound output unit 400 is a sound output device that outputs various sounds based on the sound output signal input from the processing unit 100. The sound output unit 400 corresponds to the speaker 14 of FIG. The estimated value of blood pressure may be output from the sound output unit 400 as sound.

  The communication unit 500 is a communication device for transmitting and receiving information used inside the device to and from an external information processing device under the control of the processing unit 100. As a communication method of the communication unit 500, a form of wired connection via a cable compliant with a predetermined communication standard, a form of connection via an intermediate device also used as a charger called a cradle, or short-range wireless communication is used. Various systems such as a wireless connection type can be applied. In the present embodiment, the communication unit 500 transmits and receives data to and from the cuff sphygmomanometer 3 using short-range wireless communication.

  The clock unit 600 includes a crystal oscillator including a crystal resonator and an oscillation circuit, and is a time measuring device that measures time. The time measured by the clock unit 600 is output to the processing unit 100 as needed.

  The storage unit 800 includes a storage device such as a ROM (Read Only Memory), a flash ROM, and a RAM (Random Access Memory). The storage unit 800 stores a system program for the ultrasonic sphygmomanometer 1, various programs for realizing various functions such as a transmission / reception control function, a blood vessel diameter measurement function, and a blood pressure estimation function, data, and the like. In addition, it has a work area for temporarily storing data being processed and results of various processes.

  The storage unit 800 stores a main program 810 that is read by the processing unit 100 and executed as a main process (see FIG. 6), for example. The main program 810 includes an ultrasonic blood pressure measurement program 811 executed as an ultrasonic blood pressure measurement process (see FIG. 7) and a blood pressure estimation program 813 executed as a blood pressure estimation process (see FIG. 8) as subroutines. These processes will be described later in detail using a flowchart.

  The storage unit 800 stores calibration data 820, blood vessel diameter data 830, and blood pressure data 840 as data.

  The calibration data 820 is data in which the correlation characteristic between the blood vessel diameter and the blood pressure obtained by performing the calibration processing is stored, and includes, for example, a correlation formula 821 between the blood vessel diameter and the blood pressure.

  The blood vessel diameter data 830 is data in which the blood vessel diameter measured by the blood vessel diameter measuring unit 110 is stored. This includes diastolic vessel diameter and systolic vessel diameter.

  The blood pressure data 840 is data in which the blood pressure measured by the blood pressure estimation unit 140 is stored. This includes diastolic blood pressure and systolic blood pressure.

4). Process Flow FIG. 6 is a flowchart showing a main process flow executed by the processing unit 100 in accordance with the main program 810 stored in the storage unit 800.

  First, the transmission / reception control unit 120 outputs an ultrasonic transmission / reception control signal to the ultrasonic sensor 20, thereby starting ultrasonic transmission / reception control (step A1). Then, the processing unit 100 instructs the subject to wear the cuff sphygmomanometer 3 (step A3). The mounting instruction may be realized by displaying a predetermined message or the like on the display unit 300 or may be realized by outputting a predetermined voice guidance or the like from the sound output unit 400.

  Next, the processing unit 100 acquires the diastolic blood pressure “Pd” and the systolic blood pressure “Ps” from the cuff sphygmomanometer 3 via the communication unit 500 and stores them in the storage unit 800 (step A5). The blood vessel diameter calculation unit 130 calculates the diastolic blood vessel diameter “Dd” and the systolic blood vessel diameter “Ds” based on the reflected wave of the ultrasonic wave received by the ultrasonic sensor 20, and the blood vessels in the storage unit 800. The diameter data 830 is stored (step A7).

  Next, the processing unit 100 determines a correlation equation 821 indicating the correlation characteristic between the blood vessel diameter and the blood pressure, and stores it in the calibration data 820 of the storage unit 800 (step A9). Specifically, using the diastolic blood pressure “Pd” and the systolic blood pressure “Ps” acquired in step A5, and the diastolic blood vessel diameter “Dd” and the systolic blood vessel diameter “Ds” calculated in step A7, The value of the stiffness parameter “β” in equation (1) is calculated. Then, using the calculated value of the stiffness parameter “β”, the diastolic blood pressure “Pd”, and the diastolic blood vessel diameter “Dd”, the correlation equation of Expression (1) is determined. Thereafter, the processing unit 100 instructs the subject to remove the cuff sphygmomanometer 3 (step A11).

  Next, the processing unit 100 determines whether or not it is the blood pressure measurement timing (step A13). And when it determines with it being measurement timing (step A13; Yes), an ultrasonic blood pressure measurement process is performed according to the ultrasonic blood pressure measurement program 811 memorize | stored in the memory | storage part 800 (step A15).

FIG. 7 is a flowchart showing the flow of ultrasonic blood pressure measurement processing.
First, the pressurization control unit 150 performs control so as to start the pressurization operation of the pressurization unit 30 (step B1). After a certain time has elapsed, the pressurization control unit 150 performs control so as to temporarily stop the pressurization operation of the pressurization unit 30 (step B3). And the pressure detection part 160 detects the pressure at that time according to the pressurization signal of the pressurization part 30, and makes this memorize | store temporarily in the memory | storage part 800 as a 1st pressure (step B5).

  The blood vessel diameter measuring unit 110 sets this state as the first state, and measures the blood vessel diameter D using ultrasonic waves in the first state. The measurement results are stored in the blood vessel diameter data 830 of the storage unit 800 as a first diastolic blood vessel diameter “Dd1” and a first systolic blood vessel diameter “Ds1”, respectively (step B7).

  When the measurement is completed, the pressurization control unit 150 performs control so that the pressurization operation of the pressurization unit 30 is resumed from the first state (step B9). After a certain time has elapsed, the pressurization control unit 150 performs control so as to temporarily stop the pressurization operation of the pressurization unit 30 (step B11). And the pressure detection part 160 detects the pressure at that time according to the pressurization signal of the pressurization part 30, and memorize | stores it temporarily in the memory | storage part 600 as a 2nd pressure (step B13).

  The blood vessel diameter measuring unit 110 sets this state as the second state, and measures the blood vessel diameter D using the ultrasonic wave in the second state. Then, the measurement results are stored in the blood vessel diameter data 830 of the storage unit 800 as the second diastolic blood vessel diameter “Dd2” and the second systolic blood vessel diameter “Ds2”, respectively (step B15).

  In the present embodiment, since it is only necessary to create two states with different pressures and measure the blood vessel diameter, the first state is the non-pressurized state (state where the applied pressure is 0 mmHg), and the blood vessel diameter (first blood vessel diameter) And the blood vessel diameter (second blood vessel diameter) may be measured with the second state being pressurized with a predetermined pressure (for example, 20 mmHg).

  Further, it is effective to continuously measure the blood vessel diameter of the blood vessel to be measured by using, for example, a phase difference tracking method during the period from the first state to the second state. When the first blood vessel diameter and the second blood vessel diameter are measured independently, the measurement accuracy of the blood vessel diameter using ultrasonic waves may not be sufficient. That is, if the absolute value of the blood vessel diameter in each pressurized state is used, there is a possibility that the blood vessel diameter difference cannot be calculated correctly. However, if the blood vessel diameter is continuously measured during a series of controls for changing the pressurization state, it is possible to capture a relative change in the blood vessel diameter and correctly calculate the blood vessel diameter difference. .

  Next, the differential pressure calculation unit 145 calculates a differential pressure “ΔPo” between the first pressure and the second pressure (step B17). Then, the blood pressure estimation unit 140 performs a blood pressure estimation process according to the blood pressure estimation program 813 stored in the storage unit 800 (step B19).

  FIG. 8 is a flowchart showing the flow of blood pressure estimation processing. This blood pressure estimation process can also be referred to as a characteristic value search process for searching for a characteristic value that matches the relationship between the blood pressure difference and the blood vessel diameter difference in which the differential pressure “ΔPo” is regarded as a blood pressure difference from the correlation characteristic.

  First, the characteristic value search unit 147 calculates a diastolic blood vessel diameter difference “ΔDHd” (step C1). Specifically, using the first diastolic blood vessel diameter “Dd1” calculated in step B7 and the second diastolic blood vessel diameter “Dd2” calculated in step B15, diastole is performed according to “ΔDHd = Dd1−Dd2”. The blood vessel diameter difference is calculated.

  Next, the characteristic value search unit 147 initially sets the blood pressure to “Pn” (step C3). As an initial value of blood pressure, an arbitrary value can be set in the first blood pressure measurement, and the blood pressure value measured last time can be set in the second and subsequent measurements.

  Thereafter, the characteristic value search unit 147 calculates the blood vessel diameter “Dn1” corresponding to “Pn” using the correlation equation 821 stored in the calibration data 820 (step C5). Further, the blood vessel diameter “Dn2” corresponding to “Pn−ΔPo” is calculated using the correlation equation 821 (step C7).

  Next, the characteristic value search unit 147 uses the diastolic blood vessel diameter difference “ΔDHd” calculated in Step C1, the blood vessel diameter “Dn1” calculated in Step C5, and the blood vessel diameter “Dn2” calculated in Step C7. The diastolic error “Ed = (Dn1−Dn2) −ΔDHd” is calculated (step C9).

  After that, the characteristic value search unit 147 determines whether or not the sign of the diastolic error “Ed” calculated in Step C9 is inverted (Step C11), and when it is determined that it has not been inverted (Step C11; No), the sign of the diastolic error “Ed” is determined (step C13).

  If it is determined that the sign is positive (step C13; positive), characteristic value search unit 147 adds 1 [mmHg] to the current blood pressure setting value “Pn” to update the setting value “Pn”. (Step C15). If it is determined that the sign is negative (step C13; negative), 1 [mmHg] is subtracted from the current blood pressure setting value “Pn” to update the setting value “Pn” (step C17). . After these steps, the process returns to Step C5.

  If it is determined in step C11 that the positive / negative sign of the diastolic error “Ed” has been inverted (step C11; Yes), the diastolic blood pressure estimation unit 141 before and after the positive / negative sign is inverted. The smaller absolute value of “Pn” is estimated as the diastolic blood pressure and stored in the blood pressure data 840 of the storage unit 800 (step C19).

  Next, the systolic blood pressure estimation unit 143 calculates a blood vessel diameter fluctuation range “ΔD” accompanying pulsation (step C21). Specifically, using the second diastolic blood vessel diameter “Dd2” and the second systolic blood vessel diameter “Ds2” obtained in step B9, the blood vessel diameter fluctuation width is calculated as “ΔD = Ds2−Dd2” (step C21).

  Thereafter, the systolic blood pressure estimation unit 143 estimates and stores the systolic blood pressure using the correlation equation 821, the diastolic blood pressure estimated in step C19, and the vascular diameter fluctuation range “ΔD” calculated in step C21. The blood pressure data 840 of the unit 800 is stored (step C23). Then, the blood pressure estimation unit 140 ends the blood pressure estimation process.

  Returning to the ultrasonic blood pressure measurement process of FIG. 7, after performing the blood pressure estimation process, the pressurization control unit 150 performs control so as to end the pressurization by the pressurization unit 30 (step B <b> 21). Then, the processing unit 100 ends the ultrasonic blood pressure measurement process.

  Returning to the main process of FIG. 6, after performing the ultrasonic blood pressure measurement process, the processing unit 100 uses the latest diastolic blood pressure estimated value and systolic blood pressure estimated value stored in the storage unit 800, and The display is updated (step A17).

  Thereafter, the processing unit 100 determines whether or not to end the blood pressure measurement (step A19). If it is determined that the measurement is not yet ended (step A19; No), it is determined whether or not it is the calibration timing. (Step A21). Various timings can be set as the calibration timing in this case. For example, it may be determined that it is the calibration timing when the time measured by the clock unit 600 reaches a predetermined time (for example, 8:00 in the morning).

  If it determines with it being a calibration timing (step A21; Yes), the process part 100 will return to step A3. Then, calibration using the cuff type sphygmomanometer 3 is performed again. If it is determined that it is not the calibration timing (step A21; No), the processing unit 100 returns to step A13. If it determines with complete | finishing the measurement of blood pressure in step A19 (step A19; Yes), the process part 100 will complete | finish a main process.

5. Operational Effect The ultrasonic sphygmomanometer 1 includes a pressurizing unit 30 that applies an external pressure to the measurement target site, and the pressure detecting unit 160 detects the pressure pressurized by the pressurizing unit 30. Then, the pressurization control unit 150 controls the pressurization unit 30, and the differential pressure calculation unit 145 detects the first detected by the pressure detection unit 160 in the first state and the second state where the internal and external pressure differences of the measurement target blood vessels are different. Using the first pressure and the second pressure, the differential pressure between the internal and external pressure differences is calculated. The blood pressure estimation unit 140 includes a blood vessel diameter difference that is a difference between the first blood vessel diameter and the second blood vessel diameter measured by the blood vessel diameter measuring unit 110 in the first state and the second state, and the blood pressure and the blood vessel diameter of the blood vessel to be measured. The blood pressure of the subject is estimated using the correlation equation 821 indicating the correlation characteristic with the differential pressure calculated by the differential pressure calculation unit 145.

  By controlling the operation of the pressurizing unit 30 so as to pressurize the measurement target region from the body surface with different pressures and compressing the measurement target blood vessel, the internal / external pressure difference of the measurement target blood vessel can be changed. Using this characteristic, a correlation characteristic between the blood pressure and the blood vessel diameter of the blood vessel to be measured, a blood vessel diameter difference between the first blood vessel diameter and the second blood vessel diameter, and a differential pressure between the first pressure and the second pressure are used. Thus, by estimating the blood pressure, it is possible to correctly estimate the blood pressure of the subject as compared with the conventional method.

  The blood pressure estimation unit 140 searches the correlation value for a characteristic value that matches the relationship between the blood pressure difference and the blood vessel diameter difference in which the differential pressure is regarded as a blood pressure difference, and determines the blood pressure of the subject based on the searched characteristic value. presume. Specifically, the diastolic blood pressure estimation unit 141 correlates a pattern (a relationship between a blood pressure difference and a blood vessel diameter difference) determined by the blood pressure difference in which the differential pressure is regarded as a blood pressure difference and the blood vessel diameter difference in the diastole. Which part of the equation 821 is suitable for is searched while shifting the characteristic value based on the diastolic error. Then, the diastolic blood pressure of the subject is estimated from the characteristic value that minimizes the diastolic error. The method of sequentially searching for a portion where the pattern matches along the correlation equation can easily and appropriately estimate the diastolic blood pressure of the subject.

  If the diastolic blood pressure is estimated as described above, the systolic blood pressure estimation unit 143 correlates the diastolic blood pressure with the fluctuation width associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measurement unit 110. 821 is used to estimate the systolic blood pressure of the subject. The systolic blood pressure of the subject can be easily estimated from the fluctuation range associated with the pulsation of the blood vessel diameter and the correlation equation 823.

  The blood vessel diameter measuring unit 110 is configured to be able to continuously measure the blood vessel diameter. Then, the blood pressure estimation unit 140 calculates the blood vessel diameter difference from the difference between the first blood vessel diameter when the measurement target region is pressurized with the first pressure and the second blood vessel diameter when the measurement target region is pressurized with the second pressure. To do. Rather than looking at the absolute value of the blood vessel diameter when each pressure is applied, the difference in blood vessel diameter from the difference between the first blood vessel diameter and the second blood vessel diameter obtained by continuously measuring the blood vessel diameter. By calculating, the calculation accuracy of the blood vessel diameter difference can be improved, and thus the accuracy of blood pressure estimation can be improved.

6). Modifications Embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit of the present invention. Hereinafter, modified examples will be described. In addition, about the same structure as the said embodiment, and the same step of a flowchart, the same code | symbol is attached | subjected and description for the second time is abbreviate | omitted.

6-1. Measurement target blood vessel In the above embodiment, the measurement target blood vessel has been described as the brachial artery, but other blood vessels may be used as the measurement target blood vessel. Since the technique of this embodiment is particularly effective when a relatively hard blood vessel is a measurement target, for example, a limb artery (such as a radial artery or a femoral artery) other than the brachial artery may be used as a measurement target blood vessel.

6-2. Ultrasound sphygmomanometer An ultrasonic sphygmomanometer does not necessarily have to be configured as a device worn on the upper arm of a subject. For example, it may be an ultrasonic sphygmomanometer that is wound around the wrist using the radial artery as a blood vessel to be measured. Moreover, it is good also as an ultrasonic blood pressure meter used by wrapping around a thigh or an ankle.

  Further, the ultrasonic sphygmomanometer 1 and the cuff sphygmomanometer 3 do not necessarily have to be mounted on different arms for measurement. It is also possible to use the same arm for wearing the ultrasonic sphygmomanometer 1 and the cuff sphygmomanometer 3. For example, the ultrasonic sphygmomanometer 1 is attached to the upper arm of one arm, the wrist cuff sphygmomanometer 3 is attached to the wrist of the same arm, and measurement may be performed in the same procedure as in the above embodiment. Good.

  Both the ultrasonic sphygmomanometer 1 and the cuff type sphygmomanometer 3 have a pressurizing mechanism using a cuff. For this reason, the ultrasonic sphygmomanometer 1 and the cuff sphygmomanometer 3 can be configured integrally. In this case, calibration of the sphygmomanometer and estimation of the blood pressure can be performed with a single device.

6-3. Blood vessel diameter measurement method In the above-described embodiment, a blood vessel diameter measurement method using ultrasonic waves has been exemplified. However, the blood vessel diameter measurement method is not limited to this. For example, a method of measuring a blood vessel diameter based on reflected light from a light emitting element that emits light of a predetermined wavelength toward an artery to be measured (a method for measuring a blood vessel diameter using light) may be employed. Good.

6-4. Correlation Characteristics In the above embodiment, the case where the correlation equation represented by the formula (1) is applied as the correlation characteristic between the blood vessel diameter and the blood pressure has been described as an example. However, the correlation formula of the formula (1) is merely described as an example, and it is needless to say that other correlation formulas may be applied. If it is a non-linear correlation equation, it is possible to estimate the blood pressure of the subject in the same procedure as in the above embodiment.

  Note that the storage unit 800 does not necessarily store correlation formula data, and data (lookup table) that defines correlation characteristics between blood vessel cross-sectional index values (blood vessel diameter or blood vessel cross-sectional area) and blood pressure in a table format. May be stored.

  Further, when determining the correlation formula, each of the continuously measured systolic vessel diameter and diastolic vessel diameter is averaged, and the correlation formula is calculated using the average value of the systolic vessel diameter and the average value of the diastolic vessel diameter May be determined. In this case, since a more accurate correlation equation can be obtained as the correlation characteristic between the blood vessel diameter and the blood pressure, the blood pressure measurement accuracy can be further improved by estimating the blood pressure using the correlation equation. .

6-5. Calibration timing In the embodiment described above, the ultrasonic sphygmomanometer 1 is calibrated at a timing such as the first time of blood pressure measurement or a predetermined time. However, the timing for calibration (calibration timing) can be set as appropriate. .

  Specifically, for example, the property of the blood vessel to be measured of the subject may change due to a sudden change in temperature. Therefore, a temperature sensor is built in and the temperature at the time of blood pressure measurement is stored, and the timing at which the temperature difference between the temperature at the previous measurement and the temperature at the current measurement exceeds a predetermined threshold may be used as the calibration timing. Of course, the timing at which calibration is instructed by the user may be used as the calibration timing.

6-6. Communication Method In the above-described embodiment, the communication method between the ultrasonic sphygmomanometer 1 and the cuff type sphygmomanometer 3 is wireless communication, but may be wired communication by connecting using a cable. Alternatively, the subject may be configured to perform blood pressure measurement using the cuff type sphygmomanometer 3 so that the subject manually inputs the measured value to the ultrasonic sphygmomanometer 1.

6-7. Blood pressure estimation method 6-7-1. Method for Determining Characteristic Values by Narrowing the Search Range In the above embodiment, the characteristic value search unit 147 calculates the difference between the blood pressure difference and the blood vessel diameter difference, where the differential pressure between the first pressure and the second pressure is regarded as a blood pressure difference. Although the method of sequentially searching for the characteristic value matching the relationship from the correlation characteristic has been illustrated, the method of searching for the characteristic value is not limited to this. Instead of exhaustively searching for characteristic values, it is possible to narrow down the search range.

  Specifically, the characteristic value search unit 147 sets a search range of the correlation characteristics based on the blood vessel diameter measured by the blood vessel diameter measurement unit 110 when the measurement target part is in the non-pressurized state, and the setting is performed. The characteristic value may be searched for within the specified search range. In this case, as shown in FIG. 9, the characteristic value search unit 147 has a search range setting unit 147A as a functional unit, and the search range setting unit 147A is in a state where no pressurization by the pressurization unit 30 (no addition). The search range may be set based on the blood vessel diameter measured by the blood vessel diameter measuring unit 110 in the pressure state.

  FIG. 10 is a flowchart showing the flow of the second blood pressure estimation process executed in this case by the blood pressure estimation unit 140 of the processing unit 100 instead of the blood pressure estimation process of FIG. As a premise of this process, in the ultrasonic blood pressure measurement process of FIG. 7, the blood vessel diameter is measured by setting the first state to the non-pressurized state, and the measurement result is used as the first diastolic blood vessel diameter “Dd1” and the first systolic blood vessel. It is assumed that the diameter is stored as “Ds1”.

  After step C1, the blood pressure estimation unit 140 calculates a blood vessel diameter error range based on the first diastolic blood vessel diameter Dd1 and the blood vessel diameter measurement accuracy (step E2). Specifically, the measurement error of the blood vessel diameter measuring unit 110 is set to ± ε, and the first diastolic blood vessel diameter Dd1 is set as a reference blood vessel diameter. Then, a blood vessel diameter range of ± ε centered on the reference blood vessel diameter is calculated as an error range. In the following description, the range from Dd1 to (Dd1 + ε) is referred to as “upper error range”, and the range from (Dd1−ε) to Dd1 is described as “lower error range”.

  Next, the search range setting unit 147A sets the lower error range as the search range (step E3). Although the blood vessel diameter measured in the non-pressurized state may include a measurement error, the value can be considered to be a reliable value to some extent. That is, the true value of the blood vessel diameter should exist in the vicinity of the blood vessel diameter measured in the non-pressurized state. Therefore, the characteristic value is searched using the upper error range and the lower error range as the search range. The search may be started from either error range, but here, the description will be made assuming that the lower error range is set as the search range first.

  The blood pressure estimation unit 140 sets an initial value of the blood pressure Pn within the search range (step E4). The initial value of the blood pressure Pn may be, for example, the blood pressure corresponding to the reference blood vessel diameter Dd1, or may be the blood pressure corresponding to the blood vessel diameter at the boundary opposite to the reference blood vessel diameter Dd1 in the search range. Then, while changing the blood pressure Pn at a predetermined step size, a point where the positive / negative sign of the diastolic error Ed changes within the search range is searched.

  If it is determined in step C11 that the sign of the diastolic error Ed has not changed (step C11; No), the blood pressure estimation unit 140 determines whether or not the absolute value of the diastolic error Ed has changed in a decreasing direction. Is determined (step E13). If the absolute value of the diastolic error Ed changes in a decreasing direction, a point where the sign of the diastolic error Ed will change over time should be found. However, if the absolute value of the diastolic error Ed changes in the increasing direction, the search direction is incorrect. Therefore, in this case, the search target is changed to the reverse search range.

  That is, if it is determined that the absolute value of the diastolic error Ed has changed in a decreasing direction (step E13; Yes), the blood pressure estimation unit 140 updates the blood pressure Pn by a predetermined increment (step E15). . Then, the blood pressure estimation unit 140 determines whether or not the blood vessel diameter corresponding to the updated blood pressure Pn is included in the search range (step E17), and if it is determined that it is included (step E17; Yes), step Return to C5. On the other hand, if it is determined that it is not included (step E17; No), the process proceeds to step E19.

  If it is determined in step E13 that the absolute value of the diastolic error Ed has not changed in the decreasing direction (step E13; No), the blood pressure estimation unit 140 has performed a search for both the upper and lower error ranges. Whether or not (step E19). If it is determined that the search has not yet been performed for the upper error range (step E19; No), the blood pressure estimation unit 140 switches the search range from the lower error range to the upper error range (step E21). Then, the process returns to step E4.

  On the other hand, if it is determined in step E19 that both error ranges have been searched (step E19; Yes), the blood pressure estimation unit 140 determines that the absolute value of the diastolic error Ed is within the upper and lower error ranges. The minimum blood pressure Pn is estimated as the diastolic blood pressure (step E23). Then, the process proceeds to step C21.

  In this way, by searching for a characteristic value within an error range set in the vicinity of a blood vessel diameter measured in a non-pressurized state, compared to a case where a characteristic value is sequentially searched by setting an arbitrary initial value Thus, the amount of calculation related to the search for the characteristic value can be reduced. In addition, since the true value of the blood vessel diameter should exist in the vicinity of the blood vessel diameter measured in the non-pressurized state, it is possible to obtain the correct value as the characteristic value by performing a search within the above error range. It becomes.

  Note that the error range does not have to be set around the blood vessel diameter (reference blood vessel diameter) measured in the non-pressurized state, but a range with different error widths before and after the reference blood vessel diameter (upper and lower) is searched. It may be set as a range. The error width may not be determined based on the measurement accuracy of the blood vessel diameter, but may be determined with an arbitrarily set value (fixed width). Further, when performing the search, instead of performing the search in order for the lower error range and the upper error range, the entire error range may be sequentially used as the search range.

6-7-2. Method of estimating diastolic blood pressure and systolic blood pressure at the same time In addition, after estimating the blood pressure of either one of diastolic blood pressure or systolic blood pressure, the blood pressure and the blood vessel diameter are not estimated. The diastolic blood pressure and the systolic blood pressure of the subject are measured using the characteristics, the blood vessel diameter difference relating to each of the diastolic blood vessel diameter and the systolic blood vessel diameter, the fluctuation range accompanying the pulsation of the blood vessel diameter, and the differential pressure. It is also possible to estimate at the same time.

  FIG. 11 is a flowchart showing the flow of the third blood pressure estimation process executed in this case by the blood pressure estimation unit 140 of the processing unit 100 instead of the blood pressure estimation process of FIG.

  First, the blood pressure estimation unit 140 sets a plurality of diastolic blood pressure candidate values (step D1). The method for setting the candidate values for diastolic blood pressure is arbitrary, but a predetermined number (for example, 20) of candidate values are set in increments of 1 [mmHg], for example.

  Next, the blood pressure estimation unit 140 calculates a diastolic blood vessel diameter difference according to “ΔDHd = Dd1−Dd2” (step D3). Then, the blood pressure estimation unit 140 executes the process of loop A for each candidate value of diastolic blood pressure set in step D1 (steps D5 to D17).

  In the process of loop A, the blood pressure estimation unit 140 calculates the blood vessel diameter “Dn1” corresponding to the candidate value “Pdn” using the correlation equation 821 stored in the calibration data 820 (step D7). The blood pressure estimation unit 140 calculates a blood vessel diameter “Dn2” corresponding to the blood pressure of “Pdn−ΔPo” using the correlation equation 821 (step D9).

  Next, the blood pressure estimation unit 140 uses the diastolic blood vessel diameter difference “ΔDHd” calculated in step D3, the blood vessel diameter “Dn1” calculated in step D7, and the blood vessel diameter “Dn2” calculated in step D9. The diastolic error “Ed = (Dn1−Dn2) −ΔDHd” is calculated (step D11).

  Thereafter, the blood pressure estimation unit 140 calculates a blood vessel diameter fluctuation range “ΔD = Ds2−Dd2” accompanying pulsation (step D13). Then, the blood pressure estimation unit 140 calculates the systolic blood pressure “Psn” using the correlation equation 821, the candidate value “Pn”, and the blood vessel diameter fluctuation range “ΔD”, and the candidate value of the systolic blood pressure (Step D15). Then, the process proceeds to the next candidate value. If these steps have been performed for all candidate values for diastolic blood pressure, the processing of loop A is terminated (step D17).

  Next, the blood pressure estimation unit 140 calculates a systolic blood vessel diameter difference according to “ΔDHs = Ds1−Ds2” (step D19). And the blood pressure estimation part 140 performs the process of the loop B about each candidate value of systolic blood pressure (steps D21-D29).

  In the process of loop B, the blood pressure estimation unit 140 calculates the blood vessel diameter “Ds1” corresponding to the candidate value “Psn” using the correlation equation 821 (step D23). Moreover, the blood pressure estimation unit 140 calculates the blood vessel diameter “Ds2” corresponding to the blood pressure of “Psn−ΔPo” using the correlation equation 821 (step D25).

  Next, the blood pressure estimation unit 140 uses the systolic blood vessel diameter difference “ΔDHs” calculated in step D19, the blood vessel diameter “Ds1” calculated in step D23, and the blood vessel diameter “Ds2” calculated in step D25. The systolic error “Es = (Ds1−Ds2) −ΔDHs” is calculated (step D27). Then, the blood pressure estimation unit 140 shifts the process to the next candidate value. If these steps have been performed for all candidate values for systolic blood pressure, the processing of loop B is terminated (step D29).

  Thereafter, the blood pressure estimation unit 140 calculates the diastolic error “Ed” calculated for each candidate value “Pdn” of diastolic blood pressure and the systolic error “Es” calculated for each candidate value “Psn” of systolic blood pressure. Is calculated between the combinations of corresponding candidate values (step D31). Then, the blood pressure estimation unit 140 uses the combination of candidate values with the smallest sum of calculated errors as the estimated value of the diastolic blood pressure and the systolic blood pressure, and stores it in the blood pressure data 840 of the storage unit 800 (step D33). . Then, the blood pressure estimation unit 140 ends the third blood pressure estimation process.

6-7-3. Method for Estimating Diastolic Blood Pressure from Systolic Blood Pressure In the blood pressure estimating method of the above embodiment, first, the diastolic blood pressure estimating unit 141 uses the correlation formula, the diastolic blood vessel diameter difference, and the differential pressure to determine the subject. Estimate diastolic blood pressure. Then, after that, the systolic blood pressure estimation unit 143 correlates the diastolic blood pressure estimated by the diastolic blood pressure estimation unit 141 with the fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measurement unit 110. As described above, it is assumed that the systolic blood pressure of the subject is estimated. However, this procedure can be reversed. That is, it is possible to estimate the blood pressure using the method (B) instead of the method (A) described in the above embodiment.

  Specifically, the systolic blood pressure estimation unit 143 first estimates the systolic blood pressure of the subject using the correlation formula, the systolic blood vessel diameter difference, and the differential pressure. Then, after that, the diastolic blood pressure estimation unit 141 uses the systolic blood pressure estimated by the systolic blood pressure estimation unit 143, the fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measurement unit 110, and a correlation formula. May be used to estimate the diastolic blood pressure of the subject.

  In this case, in accordance with the principle described with reference to FIG. 3, a characteristic value that matches the pattern determined by the systolic blood vessel diameter difference “ΔDHs” and the differential pressure “ΔPo” is determined by the correlation equation, and is determined by the determined characteristic value. Blood pressure is estimated as systolic blood pressure. Then, following the principle explained in FIG. 4, the blood vessel diameter (systolic blood vessel diameter) corresponding to the estimated systolic blood pressure is obtained from the correlation equation, and the blood vessel diameter fluctuation width “ΔD” is subtracted from the systolic blood vessel diameter. To calculate the diastolic blood vessel diameter. Then, the diastolic blood pressure may be estimated by substituting the calculated diastolic blood vessel diameter into the correlation equation.

6-7-4. Method for Reestimating Blood Pressure In the above embodiment, the blood pressure estimation process has been described as being executed once. However, the blood pressure of the subject is not necessarily estimated by one blood pressure estimation process, and therefore the blood pressure of the subject is re-estimated when the estimation result of the blood pressure estimation unit 140 is considered uncertain. You may do it.

  FIG. 12 is a flowchart showing the flow of the second ultrasonic blood pressure measurement process executed in this case by the blood pressure estimation unit 140 of the processing unit 100 instead of the ultrasonic blood pressure measurement process of FIG.

  After performing the blood pressure estimation process in step B19, the processing unit 100 performs a blood pressure estimation accuracy determination process (step F21). Specifically, the accuracy (accuracy) of the blood pressure estimated in the current blood pressure estimation process is determined based on, for example, a history of past blood pressure estimation results. In this case, the average value of the estimated values of blood pressure for the past predetermined number of times (for example, the past 10 times) is calculated. Then, the calculated average value is compared with the estimated value of the current blood pressure, and when the difference exceeds a predetermined threshold, it is determined that the estimated accuracy of the current blood pressure is low.

  If it is determined that the blood pressure estimation accuracy is low (step F23; low), the processing unit 100 returns to step B9. That is, the pressurization control unit 150 performs control so that the pressurization operation of the pressurization unit 30 is resumed, and the operation control is performed so as to pressurize the measurement target portion with a pressure stronger than the second pressure detected in the previous measurement. To do. When a series of processing in steps B9 to F23 is repeated and a highly accurate estimated value of blood pressure is obtained (step F23; high), the process proceeds to step B21 in FIG.

  Note that the above-described method for determining the accuracy of blood pressure estimation is merely an example and can be changed as appropriate. For example, if the subject is prompted to input an approximate blood pressure value at the time of his / her calmness, and the estimated value of the blood pressure deviates from the input value by a certain level or more, the blood pressure estimation accuracy is You may determine with low.

  In the above processing flow, the pressurization control unit 150 has been described as executing the recontrol of the pressurization unit 30 that changes the second state based on the estimation result of the blood pressure estimation unit 140. However, the first state It is good also as performing re-control of the pressurization part 30 which changes these, and it is good also as performing re-control of the pressurization part 30 which changes the state of both a 1st state and a 2nd state. That is, re-control of the pressurizing unit 30 that changes at least one of the first state and the second state may be executed based on the estimation result of the blood pressure estimation unit 140.

  DESCRIPTION OF SYMBOLS 1 Ultrasonic sphygmomanometer, 3 Cuff type | mold sphygmomanometer, 12 Operation button, 13 Liquid crystal display, 14 Speaker, 20 Ultrasonic sensor, 30 Pressurization part, 100 Processing part, 200 Operation part, 300 Display part, 400 Sound output part , 500 communication unit, 600 clock unit, 800 storage unit

Claims (8)

A blood vessel diameter measuring unit for measuring a blood vessel diameter of a measurement target blood vessel in a measurement target part;
A pressurizing unit that applies external pressure to the measurement target region so that the internal and external pressure differences of the measurement target blood vessels are different from each other in a first state and a second state;
Correlation characteristics between the blood vessel diameter difference, which is the difference between the first blood vessel diameter and the second blood vessel diameter measured by the blood vessel diameter measuring unit in the first state and the second state, and the blood vessel diameter of the blood vessel to be measured When the blood pressure estimation section for estimating the blood pressure using a differential pressure between the inner external pressure difference at the second state and the inner external pressure difference at the first state,
A blood pressure measurement device comprising: The blood pressure estimation unit includes a characteristic value search unit that searches the correlation characteristic for a characteristic value that matches the relationship between the blood pressure difference and the blood vessel diameter difference in which the differential pressure is regarded as a blood pressure difference. Estimating the blood pressure of the subject based on the value,
The blood pressure measurement device according to claim 1. The characteristic value search unit includes a search range setting unit that sets a search range of the correlation characteristics based on a blood vessel diameter measured by the blood vessel diameter measurement unit when the measurement target region is in a non-pressurized state. And searching for the characteristic value within the set search range,
The blood pressure measurement device according to claim 2. The first blood vessel diameter and the second blood vessel diameter are diastolic blood vessel diameters,
The blood pressure estimation unit
A diastolic blood pressure estimation unit that estimates the diastolic blood pressure of the subject using the correlation characteristic, the blood vessel diameter difference, and the differential pressure;
A systolic blood pressure estimation unit that estimates the systolic blood pressure of the subject using the diastolic blood pressure, a fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measuring unit, and the correlation characteristics When,
Having
The blood pressure measurement device according to any one of claims 1 to 3. The first blood vessel diameter and the second blood vessel diameter are systolic blood vessel diameters,
The blood pressure estimation unit
A systolic blood pressure estimating unit that estimates the systolic blood pressure of the subject using the correlation characteristic, the blood vessel diameter difference, and the differential pressure;
The diastolic blood pressure estimation unit that estimates the diastolic blood pressure of the subject using the systolic blood pressure, the fluctuation range associated with the pulsation of the blood vessel diameter measured by the blood vessel diameter measurement unit, and the correlation characteristic When,
Having
The blood pressure measurement device according to any one of claims 1 to 3. A pressure detection unit for detecting the pressure pressurized by the pressurization unit;
Further comprising
The blood pressure estimation unit includes a differential pressure calculation unit that calculates the differential pressure using the first pressure and the second pressure detected by the pressure detection unit in the first state and the second state.
The blood pressure measurement device according to any one of claims 1 to 5. The pressing portion, on the basis of the estimation result of the blood pressure estimation unit, the first state and pressed to change at least one of the pressure conditions in the second state,
The blood pressure estimation unit, using the vascular diameter difference and the differential pressure when the change has been the first state and a second state, to re-estimate the blood pressure of the subject,
The blood pressure measurement device according to claim 6. Measuring the blood vessel diameter of the measurement target blood vessel in the measurement target region;
A blood vessel diameter difference that is a difference between the first blood vessel diameter and the second blood vessel diameter measured in the first state and the second state in which the internal and external pressure differences of the measurement target blood vessels are different, blood pressure, and the blood vessel diameter of the measurement target blood vessel Estimating the blood pressure of the subject using the correlation characteristics of the difference between the internal and external pressure difference in the first state and the internal and external pressure difference in the second state;
Blood pressure measurement method including

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