Blood pressure measurement device and blood pressure measurement system

Abstract

To provide a technique capable of optimizing the frequency of calibrating a blood pressure value calculation algorithm according to a user when estimating the blood pressure of a human body using a feature amount related to estimation of a blood pressure value.SOLUTION: Provided is a blood pressure measuring device that is characterized in having: a feature amount acquisition unit for acquiring one or more feature amounts related to estimating the blood pressure value of a human body; a blood pressure value calculating unit for calculating the estimated blood pressure value on the basis of the feature amount; a measured blood pressure value acquiring unit for acquiring the measured blood pressure value; a calibration assessing unit for assessing whether the feature amount acquired by the feature amount acquiring unit deviates from a prescribed reference value, and when assessed that there is a deviation, determining that the measured blood pressure value is to be acquired; and a calibration processing unit for calibrating an algorithm by which the blood pressure value calculating unit calculates the estimated blood pressure value, wherein the calibration processing unit alters the reference value on the basis of the measured blood pressure value acquired by the determination made by the calibration assessing unit and the estimated blood pressure value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a blood pressure measurement device and a blood pressure measurement system. [Background technology]

[0002] Conventionally, a technique for measuring human blood pressure has been known in which a blood pressure estimate is calculated based on a feature quantity that can be noninvasively acquired, and blood pressure is measured using the estimated value. Specifically, for example, it is known that there is a correlation between blood pressure and the pulse transit time (PTT), which is the time required for a pulse wave to propagate between two points on an artery, and a device that performs noninvasive continuous blood pressure measurement based on such correlation has been proposed (for example, Patent Document 1).

[0003] Patent Document 1 discloses a blood pressure measurement device that measures blood pressure by providing electrodes serving as an electrocardiographic (ECG) sensor and a pulse wave sensor such as a photoplethysmographic (PPG) sensor on a belt that is wrapped around a user's body part to be measured, and calculating PTT based on the time difference between characteristic points on the waveform of an electrocardiogram and a pulse wave signal. With this configuration, both the electrodes and the pulse wave sensor are provided on the belt, allowing the user to attach the electrodes and pulse wave sensor to the user by wrapping the belt around them. Therefore, the technology described in Patent Document 1 provides a blood pressure measurement device that is easy to wear and significantly reduces the burden on the user when performing noninvasive, continuous blood pressure measurement on a daily basis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-154864 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when blood pressure measurement (estimation) is performed based on the correlation with a feature amount that can be non-invasively acquired, as in the technology described in Patent Document 1, the correlation differs for each user and each blood pressure measurement situation, so it is necessary to measure accurate blood pressure values ​​at appropriate timing and frequency and calibrate the blood pressure estimation algorithm based on the measured values. Patent Document 1 also describes a method of determining whether or not a condition for recommending measuring the user's blood pressure for calibration is met, and outputting information instructing blood pressure measurement if the condition is met.

[0006] As described above, obtaining accurate blood pressure values ​​for calibration can be achieved using the oscillometric method or the Korotkoff method. However, the pressure exerted by the cuff on the measurement site is generally uncomfortable for users. Therefore, when blood pressure is measured continuously, frequent calibration blood pressure measurements are a burden to the user. On the other hand, when performing blood pressure measurement (estimation) based on feature quantities, in order to calculate reliable and highly accurate measured values ​​(estimated values), calibration must be performed appropriately in accordance with various usage conditions, such as the user's exercise status, environmental temperature, and nutritional status during continuous measurement. In other words, when calibrating a blood pressure calculation algorithm for each user, it is desirable to perform calibration at a frequency necessary to accurately estimate blood pressure values ​​while minimizing the burden on the user.

[0007] However, in actual usage environments, users intentionally try out various measurement conditions (exercise intensity, environmental temperature, nutritional status, etc.) to actually measure blood pressure under various conditions and perform calibration. It is difficult to perform the calibration. Furthermore, if calibration of the blood pressure calculation algorithm is required uniformly based on a predetermined threshold value of a predetermined feature amount as in the conventional technology, the frequency of calibration will remain unchanged regardless of whether the accuracy of blood pressure estimation is low (or conversely, whether sufficient accuracy is achieved). For this reason, it is not possible to reduce the number of calibrations to avoid unnecessary blood pressure measurements according to the characteristics of each user, measurement conditions, etc., or to increase the number of calibrations to calculate estimated blood pressure values ​​with higher accuracy. In other words, there is a problem in that calibration cannot be performed at an appropriate frequency.

[0008] In view of the above circumstances, the present invention aims to provide a technology that can optimize the frequency of calibration of a blood pressure calculation algorithm depending on the user when estimating human blood pressure using features related to blood pressure estimation. [Means for solving the problem]

[0009] a feature acquisition unit that acquires one or more feature amounts related to the estimation of a blood pressure value of a human body; a blood pressure value calculation unit that calculates an estimated blood pressure value based on the feature amount; an actual blood pressure value acquisition unit that acquires an actual blood pressure value measured by a method different from that calculated by the blood pressure value calculation unit; a calibration determination unit that determines whether the feature acquired by the feature acquisition unit deviates from a predetermined reference value, and, if it is determined that the feature deviates, determines to acquire the actual blood pressure value; a calibration processing unit that calibrates an algorithm for calculating the estimated blood pressure value by the blood pressure value calculation unit using the actually measured blood pressure value, The blood pressure measurement device is characterized in that the calibration processing unit changes the reference value based on the actual blood pressure value obtained by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount that deviates from the reference value.

[0010] The feature quantities referred to here include waveform-related data such as the height at the inflection points, the slope between inflection points, and the area of ​​a specific part of the waveform, which are obtained from the electrocardiogram (ECG) and pulse wave waveform, as well as PTT and pulse wave transit time (PAT). This includes, but is not limited to, biological information such as features calculated based on multiple waveform data such as pulse arrival time (PM) and other data related to heart rate. For example, it also includes information related to the attributes of individual patients, such as height, age, weight, and medication history, as well as environmental information such as season and temperature. Furthermore, "calculating an estimated blood pressure value based on features" does not only refer to calculating one estimated value from a specific feature, but also includes calculating an estimated blood pressure value by combining multiple features.

[0011] In this way, if the reference value for determining whether calibration is necessary is changed based on the actual blood pressure value and the estimated blood pressure value, the accuracy of blood pressure estimation can be improved by repeating the calibration of the blood pressure calculation algorithm according to differences in individual user characteristics, and the frequency of calibration of the blood pressure calculation algorithm can be optimized.

[0012] Furthermore, the calibration processing unit may change the reference value to a value that decreases the frequency with which the actual blood pressure value is determined to be acquired when the difference between the actual blood pressure value obtained by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount that deviates from the reference value is equal to or smaller than a predetermined threshold. Alternatively, the calibration processing unit may change the reference value to a value that increases the frequency with which the actual blood pressure value is determined to be acquired when the difference between the actual blood pressure value obtained by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount that deviates from the reference value exceeds a predetermined threshold.

[0013] When a calibration blood pressure measurement is performed, the greater the difference between the estimated blood pressure value and the measured blood pressure value, the less appropriate the blood pressure estimation algorithm was. Therefore, as described above, if the difference between the estimated blood pressure value and the measured blood pressure value is large, the reference value of the feature amount can be changed to increase the frequency of calibration (e.g., if it is set as an upper threshold, the value can be decreased). On the other hand, if the difference between the estimated blood pressure value and the measured blood pressure value is small and the blood pressure estimation is sufficiently accurate, the reference value can be changed to decrease the frequency of calibration (e.g., if it is set as an upper threshold, the value can be increased) to reduce the burden on the user. This makes it possible to easily optimize the number of calibration processes without performing complex processes.

[0014] The blood pressure measurement device may further include an output means, and when the calibration determination unit determines to acquire the actual blood pressure value, the output means may output information indicating that the actual blood pressure value should be acquired. The output means may be, for example, a liquid crystal display, but may also be other display means such as an LED light, or other output means such as a speaker or a vibration mechanism. With this configuration, the user can easily recognize that the actual blood pressure value needs to be acquired.

[0015] The blood pressure measurement device may further include a blood pressure measurement unit for measuring the actual blood pressure value, and the actual blood pressure value acquisition unit may acquire the actual blood pressure value by measuring the actual blood pressure value using the blood pressure measurement unit when the calibration determination unit determines to acquire the actual blood pressure value. By including the blood pressure measurement unit, the actual blood pressure value can be easily acquired by measuring the blood pressure value when it is necessary. This reduces the burden of measuring blood pressure using a separate device for actual measurement and the burden of data input.

[0016] The blood pressure measurement device further includes a blood pressure measurement unit and an operation input unit for measuring the actual blood pressure value, and the actual blood pressure value acquisition unit is configured to receive the operation input. means When an input instructing measurement of the actual blood pressure value is received via the blood pressure measuring means, the actual blood pressure value may be measured by the blood pressure measuring means, thereby obtaining the actual blood pressure value.

[0017] This allows the user to measure the actual blood pressure using the blood pressure measurement means in response to user operation, allowing the user to fully prepare for the actual blood pressure measurement before starting the blood pressure measurement, thereby preventing the actual blood pressure measurement from being performed at an unexpected or inconvenient time for the user.

[0018] The present invention can also be understood as a blood pressure measurement system having the following configuration: a feature acquisition means for acquiring one or more feature values ​​related to the estimation of a blood pressure value of a human body; a blood pressure value calculation means for calculating an estimated blood pressure value based on the feature amount; an actual blood pressure value acquisition means for acquiring an actual blood pressure value measured by a method different from that calculated by the blood pressure value calculation means; Acquisition of the feature amount means a calibration determination means for determining whether the acquired feature value deviates from a predetermined reference value, and determining to acquire the actual blood pressure value if it is determined that the feature value deviates from a predetermined reference value; The blood pressure value is calculated using the measured blood pressure value. means and a calibration processing means for calibrating the algorithm for calculating the estimated blood pressure value by The calibration processing means means and changing the reference value based on the actual blood pressure value obtained by determining the feature amount and the estimated blood pressure value calculated using the feature amount that deviates from the reference value.

[0019] With this configuration, the functions for solving the problems can be provided as an overall system, without the need for each means being integrated. This allows for flexible methods of reducing the burden on users, such as narrowing down the functions of the devices that users own and use.

[0020] Further, the blood pressure measurement system The apparatus may be configured to include a measuring instrument having at least one sensor for detecting the feature amount, and an information processing device having at least the calibration processing means.

[0021] With such a configuration, the component processing means that performs complex arithmetic processing can be made into a separate terminal dedicated to information processing, and by communicating with a server or the like installed in a remote location from the measuring equipment used by the user, it becomes possible to build a cloud system that can calibrate the algorithms of each user's measuring equipment.

[0022] The measuring device may further include a blood pressure measuring means for measuring the actual blood pressure value. The measuring device may be a wearable device that can be permanently attached to the human body. The present invention is suitable for performing non-invasive continuous blood pressure measurement on a daily basis using a system configured in this way.

[0023] The present invention can be achieved by combining the above-described configurations and processes as long as no technical contradiction occurs. [Effects of the Invention]

[0024] According to the present invention, when estimating human blood pressure using features related to blood pressure estimation, a technology can be provided that can optimize the frequency of calibration of the blood pressure calculation algorithm depending on the user. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a schematic diagram showing a blood pressure measurement device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a first diagram illustrating an external appearance of the blood pressure measurement device according to the first embodiment. [Figure 3] FIG. 3 is a second diagram illustrating the appearance of the blood pressure measurement device according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating a cross section of the blood pressure measurement device according to the first embodiment. [Figure 5] FIG. 5 is a block diagram illustrating the hardware configuration of the control system of the blood pressure measurement device according to the first embodiment. [Figure 6] FIG. 6 is a block diagram illustrating the software configuration of the blood pressure measurement device according to the first embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of processing by the blood pressure measurement device according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram showing a blood pressure measurement system according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram showing an outline of the functional configuration of each element of the blood pressure measurement system according to the second embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a blood pressure measurement system according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing an outline of the functional configuration of each element of the blood pressure measurement system according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] <Embodiment 1> Specific embodiments of the present invention will be described below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in the following embodiments may vary. However, it is not intended to limit the scope of the present invention to these examples.

[0027] (overview) 1 is a schematic diagram illustrating a blood pressure measurement device 10 according to one embodiment. The blood pressure measurement device 10 is a wearable device that is attached to the upper arm of a user, which is the measurement site. The blood pressure measurement device 10 generally includes a belt unit 120, a first blood pressure measurement unit 130, a second blood pressure measurement unit 140, a calibration determination unit 150, an instruction unit 160, and a calibration processing unit 170.

[0028] The belt unit 120 includes a belt 121 and a main body 122. The belt 121 refers to a band-like member worn around the upper arm, and may also be called a band or a cuff. The belt 121 has an inner circumferential surface and an outer circumferential surface. The inner circumferential surface is the surface that comes into contact with the user's upper arm when the user wears the blood pressure measurement device 10 (hereinafter simply referred to as the "worn state"), and the outer circumferential surface is the surface opposite the inner circumferential surface.

[0029] The main body 122 is attached to the belt 121. The main body 122 accommodates components such as an operation unit 1221, a display unit 1222, and a control unit 1501 (shown in FIG. 5) described later. The operation unit 1221 is an input device that enables a user to input instructions to the blood pressure measurement device 10. In the example of FIG. 1, the operation unit 1221 includes a plurality of push buttons. The display unit 1222 is a display device that displays information such as a message prompting the user to perform blood pressure measurement and blood pressure measurement results. As the display device, for example, a liquid crystal display (LCD) or an OLED (organic light emitting diode) display can be used. A touch screen that serves as both a display device and an input device may also be used. The main body 122 may be provided with a sound-generating body such as a speaker or a piezoelectric sounder. The main body 122 may also be provided with a microphone so that the user can input instructions by voice.

[0030] The first blood pressure measurement unit 130 noninvasively measures the user's pulse wave transit time (PTT) and calculates a blood pressure value based on the measured PTT. Hereinafter, the blood pressure value calculated based on the pulse wave transit time is also referred to as an estimated blood pressure value. The first blood pressure measurement unit 130 can perform continuous blood pressure measurement to obtain a blood pressure value for each heartbeat.

[0031] The second blood pressure measurement unit 140 measures blood pressure using a method different from that of the first blood pressure measurement unit 130. Specifically, the second blood pressure measurement unit 140 measures blood pressure at a specific timing, for example, in response to a user operation, using, for example, the oscillometric method or the Korotkoff method. The second blood pressure measurement unit 140 cannot measure blood pressure continuously, but can measure blood pressure more accurately than the first blood pressure measurement unit 130. Hereinafter, the blood pressure value measured by the second blood pressure measurement unit 140 is also referred to as the actual blood pressure value.

[0032] The first blood pressure measurement unit 130 includes the functional modules of an electrocardiogram acquisition unit 131, a pulse wave signal acquisition unit 132, a pulse wave transit time calculation unit 133, and a blood pressure value calculation unit 134.

[0033] The electrocardiogram acquisition unit 131 includes a plurality of electrodes and acquires an electrocardiogram (ECG) of the user using these electrodes. The electrocardiogram represents the electrical activity of the heart. The electrodes are provided on the belt unit 120. For example, the electrodes are arranged on the inner circumferential surface of the belt 121 so that the electrodes come into contact with the skin of the user's upper arm when worn.

[0034] Pulse wave signal acquisition unit 132 includes a pulse wave sensor and acquires a pulse wave signal representing the user's pulse wave using the pulse wave sensor. The pulse wave sensor is provided on belt unit 120. For example, the pulse wave sensor is disposed on the inner circumferential surface of belt 121, so that the pulse wave sensor can detect the user's pulse wave when worn. It should be noted that some types of pulse wave sensors, such as pulse wave sensors based on the Radio Law described below, do not need to be in contact with the skin of the user's upper arm when worn.

[0035] Pulse wave propagation time calculation unit 133 calculates the pulse wave propagation time based on the time difference between the waveform characteristic points of the electrocardiogram acquired by electrocardiogram acquisition unit 131 and the waveform characteristic points of the pulse wave signal acquired by pulse wave signal acquisition unit 132. For example, pulse wave propagation time calculation unit 133 calculates the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal, and outputs the calculated time difference as the pulse wave propagation time. In this embodiment, the pulse wave propagation time corresponds to the time required for the pulse wave to propagate through the artery from the heart to the upper arm (specifically, the position where the pulse wave sensor is located).

[0036] The blood pressure value calculation unit 134 calculates the blood pressure value based on the pulse wave transit time calculated by the pulse wave transit time calculation unit 133 and a blood pressure calculation formula. The blood pressure calculation formula is a relational expression that expresses the correlation between the pulse wave transit time and blood pressure. An example of the blood pressure calculation formula is shown below. SBP=A1 / PTT 2 +A2···(1) Here, SBP represents systolic blood pressure, PTT represents pulse wave transit time, and A1 and A2 are parameters.

[0037] The pulse wave transit time calculation unit 133 can calculate the pulse wave transit time for each heartbeat, and therefore the blood pressure value calculation unit 134 can calculate the blood pressure value for each heartbeat.

[0038] The calibration determination unit 150 monitors a predetermined feature value (for example, PTT in this embodiment) acquired by the first blood pressure measurement unit 130, and determines whether the feature value deviates from a predetermined reference value (for example, an upper or lower limit threshold value). If it determines that the feature value deviates from the predetermined reference value, it determines to acquire the user's actual blood pressure value.

[0039] When the calibration determination unit 150 determines to acquire the actual blood pressure value, the instruction unit 160 outputs information instructing the second blood pressure measurement unit 140 to perform blood pressure measurement. For example, the instruction unit 160 outputs a notification sound (e.g., a melody) through a sound generator and displays a message saying "Please perform blood pressure measurement" on the display unit 1222. When the user presses a predetermined button in response to the instruction from the instruction unit 160, the second blood pressure measurement unit 140 performs blood pressure measurement. Blood pressure measurement by the second blood pressure measurement unit 140 will be described later.

[0040] The calibration processing unit 170 calibrates the blood pressure calculation formula (1) based on the actual blood pressure values ​​measured by the second blood pressure measurement unit 140. Because the correlation between the pulse wave transit time and blood pressure expressed by the blood pressure calculation formula differs for each user, it is necessary to calibrate the blood pressure calculation formula for each user. The calibration of the blood pressure calculation formula (specifically, the determination of parameters A1 and A2) is performed based on the actual blood pressure values ​​obtained by the second blood pressure measurement unit 140. The calibration of the blood pressure calculation formula will be described in detail later.

[0041] As described above, in the blood pressure measurement device 10, the plurality of electrodes used to acquire an electrocardiogram and the pulse wave sensor used to acquire a pulse wave signal are both provided on the belt unit 120. This allows the electrodes and pulse wave sensor to be attached to the user simply by wrapping the belt unit 120 around the upper arm. This makes it easy for the user to wear the device, and reduces the user's objection to wearing the blood pressure measurement device 10.

[0042] Furthermore, the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal related to the upper arm is calculated as the pulse wave propagation time. The pulse wave propagation time obtained by the blood pressure measurement device 10 is a larger value than when the pulse wave propagation time is measured between two points on the upper arm. In other words, a longer pulse wave propagation distance is ensured. Therefore, the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal is calculated as the pulse wave propagation time. This reduces the effect on the pulse wave propagation time of errors that occur when calculating the time difference between the two points, allowing for accurate measurement of the pulse wave propagation time. As a result, the reliability of blood pressure values ​​obtained by blood pressure measurements based on the pulse wave propagation time is improved.

[0043] (Configuration example) The blood pressure measurement device 10 will be described in more detail below. An example of the configuration of the blood pressure measurement device 10 according to this embodiment will be described with reference to Fig. 2 to Fig. 6. Fig. 2 and Fig. 3 are plan views illustrating the external appearance of the blood pressure measurement device 10. Specifically, Fig. 2 shows the blood pressure measurement device 10 as seen from the outer peripheral surface 1211 side of the belt 121 in an unfolded state, and Fig. 3 shows the blood pressure measurement device 10 as seen from the inner peripheral surface 1212 side of the belt 121 in an unfolded state. Fig. 4 shows a cross section of the blood pressure measurement device 10 in a worn state.

[0044] The belt 121 includes an attachment member that allows the belt 121 to be attached to and detached from the upper arm. In the example shown in FIGS. 2 and 3, the attachment member is a hook-and-loop fastener having a loop surface 1213 with numerous loops and a hook surface 1214 with multiple hooks. The loop surface 1213 is disposed on the outer peripheral surface 1211 of the belt 121 at an end 1215A in the longitudinal direction of the belt 121. The longitudinal direction corresponds to the circumferential direction of the upper arm when worn. The hook surface 1214 is disposed on the inner peripheral surface 1212 of the belt 121 at an end 1215B in the longitudinal direction of the belt 121. The end 1215B faces the end 1215A in the longitudinal direction of the belt 121. When the loop surface 1213 and the hook surface 1214 are pressed against each other, the loop surface 1213 and the hook surface 1214 are coupled together. Additionally, loop surface 1213 and hook surface 1214 can be pulled away from each other to separate them.

[0045] As shown in FIG. 3, an electrode group 1311 for measuring an electrocardiogram is arranged on the inner peripheral surface 1212 of the belt 121. In the example of FIG. 3, the electrode group 1311 has six electrodes 1312 aligned at regular intervals along the longitudinal direction of the belt 121. The spacing between the electrodes 1312 is set to, for example, one-fourth the circumference of the upper arm of an assumed user with the thinnest arms. With this arrangement, as shown in FIG. 4, for an assumed user with the thinnest arms, four of the six electrodes 1312 contact the upper arm UA when worn, and are positioned at equal intervals around the circumference of the upper arm, while the remaining two electrodes 1312 contact the outer peripheral surface of the belt 121. In FIG. 4, the humerus UAB and brachial artery UAA are shown. For an assumed user with the thickest arms, all six electrodes 1312 contact the upper arm UA when worn.

[0046] The number of electrodes 1312 is not limited to six, and may be two to five, or seven or more. When two or three electrodes 1312 are in contact with the upper arm, an electrocardiogram may not be measured properly depending on the wearing state. When an electrocardiogram cannot be measured properly, a message may be displayed on the display unit 1222, for example, to prompt the user to wear the blood pressure measurement device 10 again. To avoid a situation where an electrocardiogram cannot be measured, it is desirable that at least four electrodes 1312 be in contact with the upper arm when the device is worn.

[0047] The closer the electrode 1312 is positioned to the heart when worn, the larger the signal representing the electrical activity of the heart obtained using the electrode 1312, i.e., the higher the signal-to-noise ratio (SNR). Preferably, as shown in FIG. 3 , the electrode 1312 is positioned in the central portion 1217A of the belt 121. The central portion 1217A is a portion located more centrally (toward the shoulder) than the center line 1216 when worn. More preferably, the electrode 1312 is positioned in the central end portion 1218A of the belt 121. The central end portion 1218A is an end located centrally when worn, and the width of the central end portion 1218A is, for example, one-third of the overall width of the belt 121.

[0048] A sensor unit 1322 of a pulse wave sensor 1321 for measuring a pulse wave is further disposed on the inner circumferential surface 1212 of the belt 121. In the example of Fig. 3, the sensor unit 1322 includes a pair of electrodes 1323A and 1323D for applying current to the upper arm and a pair of electrodes 1323B and 1323C for detecting voltage. The electrodes 1323A, 1323B, 1323C, and 1323D are arranged in this order in the width direction of the belt 121. The width direction of the belt 121 is the direction along the brachial artery UAA when the belt 121 is worn.

[0049] Furthermore, the farther the sensor unit 1322 is positioned from the heart when worn, the longer the pulse wave propagation distance and the larger the measured value of the pulse wave propagation time. Therefore, the error that occurs when calculating the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal becomes smaller relative to the pulse wave propagation time, allowing for accurate measurement of the pulse wave propagation time. Preferably, the sensor unit 1322 is positioned in the peripheral portion 1217B of the belt 121. The peripheral portion 1217B is a portion located closer to the peripheral side (elbow side) than the center line 1216 when worn. More preferably, the sensor unit 1322 is positioned in the peripheral end 1218C of the belt 121. The peripheral end 1218C is an end located on the peripheral side when worn, and the width of the peripheral end 1218C is, for example, one-third of the overall width of the belt 121. The portion 1218B between the central end 1218A and the peripheral end 1218C is referred to as the intermediate portion.

[0050] As shown in FIG. 4, the belt 121 includes an inner cloth 1210A, an outer cloth 1210B, and a pressure cuff 1401 provided between the inner cloth 1210A and the outer cloth 1210B. The pressure cuff 1401 is a strip-shaped member that is long in the longitudinal direction of the belt 121 so as to be able to surround the upper arm. For example, the pressure cuff 1401 is configured as a fluid bag by placing two stretchable polyurethane sheets facing each other in the thickness direction and welding their peripheral edges together. The electrode group 1311 and the sensor unit 1322 are provided on the inner cloth 1210A so as to be located between the pressure cuff 1401 and the upper arm UA when the device is worn.

[0051] FIG. 5 illustrates an example of the hardware configuration of the control system of the blood pressure measurement device 10 according to this embodiment. In the example of FIG. 5, the main body 122 is equipped with, in addition to the operation unit 1221 and display unit 1222 described above, a control unit 1501, a storage unit 1505, a battery 1506, a switch circuit 1313, a subtraction circuit 1314, an analog front end (AFE) 1315, a pressure sensor 1402, a pump 1403, a valve 1404, an oscillator circuit 1405, and a pump drive circuit 1406. The pulse wave sensor 1321 is equipped with, in addition to the sensor unit 1322 described above, an energization and voltage detection circuit 1324. In this example, the energization and voltage detection circuit 1324 is mounted on the belt 121.

[0052] The control unit 1501 includes a central processing unit (CPU) 1502, a random access memory (RAM) 1503, a read-only memory (ROM) 1504, and the like, and controls each component in response to information processing. The storage unit 1505 is an auxiliary storage device such as a hard disk drive (HDD) or a semiconductor memory (e.g., flash memory), and stores programs executed by the control unit 1501 (e.g., including a pulse wave propagation time measurement program and a blood pressure measurement program), setting data required to execute the programs, blood pressure measurement results, and the like in a nonvolatile manner. The storage medium included in the storage unit 1505 is a medium that stores information such as programs electrically, magnetically, optically, mechanically, or chemically so that the information can be read by a computer or other device or machine. Note that part or all of the programs may be stored in the ROM 1504.

[0053] The battery 1506 supplies power to components such as the control unit 1501. The battery 1506 is, for example, a rechargeable battery.

[0054] Each of the electrodes 1312 included in the electrode group 1311 is connected to an input terminal of a switch circuit 1313. Two output terminals of the switch circuit 1313 are connected to two input terminals of a subtraction circuit 1314. The switch circuit 1313 receives a switch signal from the control unit 1501 and connects two electrodes 1312 designated by the switch signal to the subtraction circuit 1314. The subtraction circuit 1314 subtracts a potential input from one input terminal from a potential input from the other input terminal. The subtraction circuit 1314 outputs a potential difference signal representing the potential difference between the two connected electrodes 1312 to the AFE 1315. The subtraction circuit 1314 is, for example, an instrumentation amplifier. The AFE 1315 includes, for example, a low-pass filter (LPF), an amplifier, and an analog-to-digital converter. The potential difference signal is filtered by the LPF, amplified by the amplifier, and converted into a digital signal by the analog-to-digital converter. The potential difference signal converted into a digital signal is given to the control unit 1501. The control unit 1501 acquires the potential difference signal output in time series from the AFE 1315 as an electrocardiogram.

[0055] The current and voltage detection circuit 1324 passes a high-frequency constant current between electrodes 1323A and 1323D. For example, the current frequency is 50 kHz and the current value is 1 mA. While current is passing between electrodes 1323A and 1323D, the current and voltage detection circuit 1324 detects the voltage between electrodes 1323B and 1323C and generates a detection signal. The detection signal represents a change in electrical impedance due to a pulse wave propagating through the artery facing electrodes 1323B and 1323C. The current and voltage detection circuit 1324 performs signal processing on the detection signal, including rectification, amplification, filtering, and analog-to-digital conversion, and provides the detection signal to the control unit 1501. The control unit 1501 acquires the detection signal output in time series from the current and voltage detection circuit 1324 as a pulse wave signal.

[0056] Pressure sensor 1402 is connected to pressure cuff 1401 via piping, and pump 1403 and valve 1404 are also connected to pressure cuff 1401 via piping. These piping may be a single common piping or separate piping. Pump 1403 is, for example, a piezoelectric pump, and supplies air as a fluid to pressure cuff 1401 through the piping to increase the pressure inside pressure cuff 1401. Valve 1404 is mounted on pump 1403 and is configured such that its opening and closing is controlled in accordance with the operating state (on / off) of pump 1403. Specifically, when pump 1403 is turned on, valve 1404 is closed, and when pump 1403 is turned off, valve 1404 is open. When valve 1404 is open, pressure cuff 1401 communicates with the atmosphere, and air inside pressure cuff 1401 is discharged into the atmosphere. The valve 1404 functions as a check valve to prevent backflow of air. The pump drive circuit 1406 drives the pump 1403 based on a control signal received from the control unit 1501.

[0057] The pressure sensor 1402 detects the pressure in the pressure cuff 1401 (also referred to as cuff pressure) and generates an electrical signal representing the cuff pressure. The cuff pressure is, for example, a pressure based on atmospheric pressure. The pressure sensor 1402 is, for example, a piezo-resistive pressure sensor. The oscillator circuit 1405 oscillates based on the electrical signal from the pressure sensor 1402 and outputs a frequency signal having a frequency corresponding to the electrical signal to the control unit 1501. In this example, the output of the pressure sensor 1402 is used to control the pressure in the pressure cuff 1401 and to calculate blood pressure values ​​(including systolic blood pressure and diastolic blood pressure) by an oscillometric method.

[0058] The pressure cuff 1401 may be used to adjust the state of contact between the electrode 1312 or the sensor unit 1322 of the pulse wave sensor 1321 and the upper arm UA. For example, when blood pressure measurement based on the pulse wave transit time is performed, the pressure cuff 1401 is kept in a state in which a certain amount of air is contained. This ensures that the electrode 1312 and the sensor unit 1322 of the pulse wave sensor 1321 are in reliable contact with the upper arm UA.

[0059] In the example shown in FIGS. 2 to 5, the electrode group 1311, the switch circuit 1313, the subtraction circuit 1314, and the 1 , and the pulse wave sensor 1321 (electrodes 1323 and current-carrying and voltage detection circuit 1324) corresponds to the pulse wave signal acquisition unit 132 of the first blood pressure measurement unit 130. In addition, the pressure cuff 1401, the pressure sensor 1402, the pump 1403, the valve 1404, the oscillation circuit 1405, and the pump drive circuit 1406 correspond to the second blood pressure measurement unit 140.

[0060] Note that, with regard to the specific hardware configuration of the blood pressure measurement device 10, components can be omitted, replaced, or added as appropriate depending on the embodiment. For example, the control unit 1501 may include multiple processors. The blood pressure measurement device 10 may include a communication unit 1507 for communicating with an external device such as a user's mobile terminal (e.g., a smartphone). The communication unit 1507 includes a wired communication module and / or a wireless communication module. For example, Bluetooth (registered trademark), BLE (Bluetooth Low Energy), etc. can be adopted as the wireless communication method.

[0061] Fig. 6 illustrates an example of the software configuration of the blood pressure measurement device 10 according to this embodiment. In the example of Fig. 6, the blood pressure measurement device 10 includes an electrocardiogram measurement control unit 1601, an electrocardiogram storage unit 1602, a pulse wave measurement control unit 1603, a pulse wave signal storage unit 1604, a pulse wave transit time calculation unit 133, a blood pressure value calculation unit 134, a blood pressure calculation formula storage unit 1605, an estimated blood pressure value storage unit 1606, a calibration determination unit 150, an instruction unit 160, a blood pressure measurement control unit 1608, an actual blood pressure value storage unit 1609, a display control unit 1607, an instruction input unit 1610, a calibration processing unit 170, and a calibration determination reference value storage unit 1611. The electrocardiogram measurement control unit 1601, pulse wave measurement control unit 1603, pulse wave transit time calculation unit 133, blood pressure value calculation unit 134, calibration determination unit 150, instruction unit 160, blood pressure measurement control unit 1608, display control unit 1607, instruction input unit 1610, and calibration processing unit 170 perform the following processing by the control unit 1501 of the blood pressure measurement device 10 executing a program stored in the storage unit 1505. When the control unit 1501 executes a program, the control unit 1501 loads the program into the RAM 1503. Then, the control unit 1501 interprets and executes the program loaded into the RAM 1503 using the CPU 1502 to control each component. The electrocardiogram storage unit 1602 , pulse wave signal storage unit 1604 , blood pressure calculation formula storage unit 1605 , estimated blood pressure value storage unit 1606 , measured blood pressure value storage unit 1609 , and calibration determination reference value storage unit 1611 are realized by the storage unit 1505 .

[0062] The electrocardiogram measurement control unit 1601 controls the switch circuit 1313 to acquire an electrocardiogram. Specifically, the electrocardiogram measurement control unit 1601 generates a switch signal for selecting two of the six electrodes 1312, and provides this switch signal to the switch circuit 1313. The electrocardiogram measurement control unit 1601 acquires a potential difference signal obtained using the two selected electrodes 1312, and stores time-series data of the acquired potential difference signal as an electrocardiogram in the electrocardiogram storage unit 1602.

[0063] When the user wears the blood pressure measurement device 10 on the upper arm, the electrocardiogram measurement control unit 1601 determines the optimal electrode pair for obtaining an electrocardiogram. For example, the electrocardiogram measurement control unit 1601 obtains an electrocardiogram for each of all electrode pairs and determines the electrode pair that provides an electrocardiogram with the largest R wave amplitude as the optimal electrode pair. Thereafter, the electrocardiogram measurement control unit 1601 measures an electrocardiogram using the optimal electrode pair.

[0064] The pulse wave measurement control unit 1603 controls the current application and voltage detection circuit 1324 to acquire a pulse wave signal. Specifically, the pulse wave measurement control unit 1603 controls the electrodes 1323A, 1323 The current supply and voltage detection circuit 1324 is instructed to supply a current between the electrodes 1323A and D. 1323 A detection signal indicating the voltage detected between electrodes 1323B and 1323C when a current is flowing between electrodes 1323B and 1323C is acquired. Pulse wave measurement control section 1603 converts the time series data of the detection signal into a pulse wave signal. The code is stored in the code storage unit 1604.

[0065] Pulse wave transit time calculation unit 133 reads an electrocardiogram from electrocardiogram storage unit 1602 and a pulse wave signal from pulse wave signal storage unit 1604, and calculates the pulse wave transit time based on the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal. For example, pulse wave transit time calculation unit 133 detects the time (time) of the peak point corresponding to the R wave from the electrocardiogram, detects the time (time) of the rising point from the pulse wave signal, and calculates the difference obtained by subtracting the time of the peak point from the time of the rising point as the pulse wave transit time.

[0066] The pulse wave transit time calculation unit 133 may correct the time difference based on the pre-ejection period (PEP) and output the corrected time difference as the pulse wave transit time. For example, the pre-ejection period may be considered to be constant, and the pulse wave transit time calculation unit 133 may calculate the pulse wave transit time by subtracting a predetermined value from the time difference.

[0067] A peak point corresponding to an R wave is an example of a waveform characteristic point of an electrocardiogram. A waveform characteristic point of an electrocardiogram may be a peak point corresponding to a Q wave or a peak point corresponding to an S wave. Because an R wave appears as a clearer peak than a Q wave or an S wave, the time of the R wave peak point can be determined more accurately. For this reason, the R wave peak point is preferably used as the waveform characteristic point of an electrocardiogram. Furthermore, a rising point is an example of a waveform characteristic point of a pulse wave signal. A waveform characteristic point of a pulse wave signal may be a peak point. Because a pulse wave signal changes gradually over time, errors are likely to occur when determining the time of a waveform characteristic point in a pulse wave signal.

[0068] 6, the blood pressure value calculation unit 134 calculates an estimated blood pressure value based on the pulse wave transit time calculated by the pulse wave transit time calculation unit 133 and the blood pressure calculation formula. The blood pressure value calculation unit 134 uses an algorithm for calculating blood pressure values ​​(specifically, for example, the above formula (1)) stored in the blood pressure calculation formula storage unit 1605 as the blood pressure calculation formula. The blood pressure value calculation unit 134 associates the calculated blood pressure value with time information and stores it in the estimated blood pressure value storage unit 1606.

[0069] The blood pressure calculation formula is not limited to the above formula (1). For example, the blood pressure calculation formula may be the following formula. SBP=B1 / PTT 2 +B2 / PTT+B3×PTT+B4...(2) Here, B1, B2, B3, and B4 are parameters.

[0070] The calibration determination unit 150 determines whether the conditions for recommending measurement of the user's blood pressure are met based on a predetermined feature related to blood pressure estimation, such as the pulse wave transit time calculated by the pulse wave transit time calculation unit 133, and a predetermined reference value for the feature stored in the calibration determination reference value storage unit 1611. Even if the blood pressure calculation formula has been calibrated when the device is first used, the accuracy of the calculated estimated blood pressure value may be low if the feature related to the estimated blood pressure value calculation deviates from a predetermined reference value (upper or lower limit threshold). Therefore, in such a case, it is desirable to perform accurate blood pressure measurement using the second blood pressure measurement unit 140 and compare the estimated blood pressure value with the actual blood pressure value to confirm the accuracy of the estimated blood pressure value. If the accuracy is low (i.e., the difference between the actual blood pressure value and the estimated blood pressure value is large), it is desirable to calibrate the blood pressure calculation formula.

[0071] As another example, the calibration determination unit 150 may determine whether or not the blood pressure change rate exceeds a threshold as a predetermined characteristic amount. The blood pressure change rate is, for example, the amount of change in blood pressure value per unit time. Specifically, the calibration determination unit 150 determines whether or not the difference obtained by subtracting the blood pressure value from the latest blood pressure value unit time ago exceeds a threshold. Let the latest systolic blood pressure value be SBP0, the systolic blood pressure value unit time ago be SBP1, and the threshold be V. th Then, the calibration determination unit 150 determines whether SBP0-SBP1>V th It is determined whether the following conditional expression is satisfied. The unit time is, for example, 30 seconds, and the threshold is, for example, 20 [mmHg]. If the latest pulse wave transit time value is PTT0 and the pulse wave transit time value unit time ago is PTT1, the above conditional expression can be transformed using equation (1) to obtain A1(1 / PTT0) 2 -1 / PTT1 2 )>V th This becomes:

[0072] That is, the calibration determination unit 150 may use the pulse wave transit time itself, or may use a blood pressure value calculated based on the pulse wave transit time. The calibration determination unit 150 may also determine whether the difference between the latest blood pressure value and the blood pressure value a predetermined number of heartbeats before (e.g., 30 heartbeats before) exceeds a threshold value. In another example, the calibration determination unit 150 determines whether the latest systolic blood pressure value exceeds a threshold value (e.g., 150 mmHg). This threshold value may be fixed or variable. For example, the higher the user's mean blood pressure, the higher the threshold value is set.

[0073] When the calibration determination unit 150 determines to acquire the actual blood pressure value, the instruction unit 160 outputs information instructing the second blood pressure measurement unit 140 to perform blood pressure measurement. For example, the instruction unit 160 provides an instruction signal to the display control unit 1607 to cause the display unit 1222 to display a message prompting the user to perform blood pressure measurement. Furthermore, the instruction unit 160 outputs a control signal to control a drive circuit that drives a sound generator to generate a notification sound. Note that the instruction unit 160 may also transmit an instruction signal to the user's mobile device via the communication unit 1507, thereby prompting the user to perform blood pressure measurement via the mobile device.

[0074] The instruction input unit 1610 accepts instructions input by the user using the operation unit 1221. For example, when an operation to instruct execution of blood pressure measurement is performed, the instruction input unit 1610 gives an instruction to start blood pressure measurement to the blood pressure measurement control unit 1608. The instruction input unit 1610 and the operation unit 1221 correspond to the operation input unit according to the present invention.

[0075] The blood pressure measurement control unit 1608 controls the pump drive circuit 1406 to perform blood pressure measurement. Upon receiving a command to start blood pressure measurement from the command input unit 1610, the blood pressure measurement control unit 1608 drives the pump 1403 via the pump drive circuit 1406. This starts the supply of air to the pressure cuff 1401. The pressure cuff 1401 inflates, thereby compressing the user's upper arm. The blood pressure measurement control unit 1608 monitors the cuff pressure using the pressure sensor 1402. During the pressurization process of supplying air to the pressure cuff 1401, the blood pressure measurement control unit 1608 calculates blood pressure values ​​using the oscillometric method based on the pressure signal output from the pressure sensor 1402. The blood pressure values ​​include, but are not limited to, systolic blood pressure (SBP) and diastolic blood pressure (DBP). The blood pressure measurement control unit 1608 associates the calculated blood pressure values ​​with time information and stores them in the measured blood pressure value storage unit 1609. The blood pressure measurement control unit 1608 can calculate the pulse rate at the same time as the blood pressure value. When the calculation of the blood pressure value is completed, the blood pressure measurement control unit 1608 stops the pump 1403 via the pump drive circuit 1406. This causes air to be exhausted from the pressure cuff 1401 through the valve 1404.

[0076] The display control unit 1607 controls the display unit 1222. For example, the display control unit 1607 receives an instruction signal from the instruction unit 160 and causes the display unit 1222 to display a message included in the instruction signal. In addition, the display control unit 1607 causes the display unit 1222 to display the blood pressure measurement result after the blood pressure measurement control unit 1608 has completed blood pressure measurement.

[0077] The calibration processing unit 170 calibrates the blood pressure calculation formula based on the estimated blood pressure value obtained by the blood pressure value calculation unit 134 and the actually measured blood pressure value obtained by the blood pressure measurement control unit 1608. In addition to this, the calibration of the blood pressure calculation formula by the calibration processing unit 170 may be performed as an initial setting, for example, when the user wears the blood pressure measurement device 10. The correlation between the pulse wave transit time and the blood pressure value differs for each individual. Furthermore, the correlation changes depending on the state in which the blood pressure measurement device 10 is worn on the user's upper arm. For example, even for the same user, the correlation changes when the blood pressure measurement device 10 is placed closer to the shoulder and when it is placed closer to the elbow. In order to reflect such a change in the correlation, the calibration of the blood pressure calculation formula A calibration is performed.

[0078] The calibration processing unit 170 also changes the reference value stored in the calibration determination reference value storage unit 1611. Specifically, for example, the calibration processing unit 170 calculates the difference between the estimated blood pressure value when the calibration determination unit 150 decides to acquire the actual blood pressure value and the actual blood pressure value, and if the difference is large, the calibration processing unit 170 changes the reference value so that the frequency of calibration increases, and if the difference is small, the calibration processing unit 170 changes the reference value so that the frequency of calibration decreases.

[0079] In the present embodiment, an example is described in which all of the functions of the blood pressure measurement device 10 are implemented by a general-purpose processor. However, some or all of the functions may be implemented by one or more dedicated processors.

[0080] (Example of operation) Next, an example of the operation of the blood pressure measurement device 10 according to this embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing an example of the flow of processing performed by the blood pressure measurement device 10. First, when a user uses the blood pressure measurement device 10 for the first time, an initial calibration of the blood pressure calculation formula is performed (S101). In this process, the control unit 1501 operates as the calibration processing unit 170. If the number of parameters included in the blood pressure calculation formula is N, N or more pairs of measured values ​​of pulse wave transit time and blood pressure are required. The above blood pressure calculation formula (1) has two parameters A1 and A2. In this case, for example, the control unit 1501 acquires pairs of measured values ​​of pulse wave transit time and blood pressure while the user is at rest, and then has the user exercise and acquires pairs of measured values ​​of pulse wave transit time and blood pressure after the exercise. As a result, two pairs of measured values ​​of pulse wave transit time and blood pressure are acquired. The control unit 1501 determines the parameters A1 and A2 based on the two pairs of measured values ​​of pulse wave transit time and blood pressure.

[0081] Subsequently, a reference value for determining whether or not the actual blood pressure measurement value needs to be acquired is set (S102). The reference value may be calculated based on the determined parameters A1 and A2, or a general-purpose reference value may be set. The reference value set here is stored in the calibration determination reference value storage unit 1611.

[0082] After the initial calibration is completed, blood pressure measurement (estimation) based on the pulse wave transit time becomes possible, and continuous, non-invasive blood pressure measurement is performed by repeating the following loop process L1 until a predetermined termination condition is met.

[0083] In loop processing L1, the following processing is repeatedly executed. First, the control unit 1501 continuously calculates the pulse wave transit time to calculate an estimated blood pressure value (S103). Furthermore, the control unit 1501 calculates an estimated blood pressure value based on the calculated pulse wave transit time and the blood pressure calculation formula stored in the blood pressure calculation formula storage unit (S104). Next, the control unit 1501 performs processing to determine whether the calculated pulse wave transit time deviates from the reference value stored in the calibration determination reference value storage unit 1611 (S105). The reference value may be, for example, an upper or lower threshold value of the pulse wave transit time. Alternatively, it may be upper or lower limit thresholds that define a predetermined numerical range. That is, in step S105, it is determined whether the reference value exceeds the upper limit threshold, or whether the reference value exceeds the lower limit threshold. If the reference value is a value, it is determined whether it is less than the reference value, and if the reference value is an upper or lower limit threshold, it is determined whether it falls within a predetermined numerical range between them.

[0084] If it is determined in step S105 that the blood pressure does not deviate from the reference value, the process returns to step S103 and repeats the subsequent steps. On the other hand, if it is determined in step S105 that the blood pressure deviates from the reference value, the process proceeds to step S106 and determines that an actual blood pressure value measured by second blood pressure measurement unit 140 should be acquired for the calibration of the blood pressure calculation formula. In the process of step S105, control unit 1501 functions as calibration determination unit 150.

[0085] In step S106, control unit 1501 executes control for outputting information instructing second blood pressure measurement unit 140 to perform blood pressure measurement. In step S106, control unit 1501 operates as instruction unit 160. Then, upon receiving a command to start blood pressure measurement from the user via operation unit 1221, processing is performed to acquire the actual blood pressure value measured by second blood pressure measurement unit 140 (S107). In step S107, control unit 1501 operates as blood pressure measurement control unit 1608.

[0086] When the actual blood pressure value is acquired, the control unit 1501 calibrates the blood pressure calculation formula stored in the blood pressure calculation formula storage unit 1605 based on the acquired value (S108), and also executes a process to determine whether the difference between the estimated blood pressure value and the actual blood pressure value is equal to or greater than a predetermined threshold value (S109).

[0087] If the difference is equal to or greater than the threshold, the reference value stored in the calibration determination reference value storage unit 1611 is changed so that the frequency with which the instructing unit 160 instructs the acquisition of measured blood pressure values ​​increases (S110). Specifically, if the reference value is the upper and lower thresholds for the pulse wave transit time, the upper threshold is decreased and the lower threshold is increased, i.e., the numerical range determined by the upper and lower thresholds is narrowed. In this way, the calculated pulse wave transit time is more likely to deviate from the upper and lower thresholds than before the reference value was changed, and as a result, the instructing unit 160 instructs the acquisition of measured blood pressure values ​​more frequently.

[0088] On the other hand, if it is determined in step S108 that the difference is less than the threshold, the reference value is changed so that the frequency with which the instructing unit 160 instructs the acquisition of measured blood pressure values ​​decreases (S111). Specifically, contrary to the case of step S110, if the reference value is the upper and lower thresholds of the pulse wave transit time, the upper threshold is increased and the lower threshold is decreased, that is, the numerical range determined by the upper and lower thresholds is expanded. In this way, the calculated pulse wave transit time is less likely to deviate from the upper and lower thresholds than before the reference value was changed, and as a result, the frequency with which the instructing unit 160 instructs the acquisition of measured blood pressure values ​​decreases.

[0089] When the process of step S110 or step S111 is executed, the series of loop processes L1 ends, and the process returns to the start point of the loop process L1 (i.e., step S103) and a new loop process L1 is executed. In the processes of steps S108 to S111, the control unit 1501 functions as the calibration processing unit 170.

[0090] 7 is an example, and the order of the processes or the content of each process can be changed as appropriate. For example, in the above process, after the blood pressure calculation formula is calibrated in step S108, the process proceeds to step S109 to determine whether the difference between the actual blood pressure value and the estimated blood pressure value is equal to or greater than a predetermined threshold. However, this order may be reversed, and the process to determine whether the difference between the actual blood pressure value and the estimated blood pressure value is equal to or greater than a predetermined threshold may be performed first. If the difference is less than the predetermined threshold, the calibration of the blood pressure calculation formula may not be performed.

[0091] In the above processing procedure, if the difference is equal to or greater than a predetermined threshold in step S109, the reference value is changed to increase the frequency of calibration, and if not, the reference value is changed to decrease the frequency of calibration, but upper and lower thresholds may be set. That is, if the difference is equal to or greater than an upper threshold, the reference value may be changed to increase the frequency of calibration, if the difference is equal to or less than a lower threshold, the reference value may be changed to decrease the frequency of calibration, and the reference value may not be changed unless the difference deviates from the upper or lower threshold.

[0092] (effect) As described above, in the blood pressure measurement device 10 according to this embodiment, the electrode group 1311 and the pulse wave sensor The electrode group 1311 and the sensor unit 1322 of the pulse wave sensor 1321 are both provided on the belt 121. Therefore, by simply wrapping the belt 121 around the upper arm, both the electrode group 1311 and the pulse wave sensor 1321 are attached to the user. This allows the user to easily wear the blood pressure measurement device 10. Because the user only needs to wear one device, the user is less likely to be reluctant to wear the blood pressure measurement device 10.

[0093] Furthermore, because the blood pressure measurement device 10 is worn on the upper arm, blood pressure measurement is performed at approximately the same height as the heart. This eliminates the need for height correction of the acquired blood pressure measurement results. Furthermore, when the blood pressure measurement device 10 is an upper arm type, the blood pressure measurement device 10 can be hidden by the sleeve of clothing, making it less noticeable that the blood pressure measurement device 10 is being worn.

[0094] Furthermore, since the pulse wave transit time is calculated based on the electrocardiogram and the pulse wave signal obtained for the upper arm, the pulse wave transit time can be obtained over a long distance, from the heart to the upper arm. This improves robustness against errors that occur when calculating the time difference between the waveform feature points of the electrocardiogram and the waveform feature points of the pulse wave signal. Furthermore, the electrode group 1311 is disposed in the central portion 1217A of the belt 121, and the sensor unit 1322 of the pulse wave sensor 1321 is disposed in the peripheral portion 1217B of the belt 121. This arrangement ensures a longer pulse wave transit distance and obtains an electrocardiogram with a high signal-to-noise ratio. This further improves robustness. As a result, the pulse wave transit time can be measured accurately, improving the reliability of the blood pressure value calculated based on the pulse wave transit time.

[0095] Furthermore, in this embodiment, blood pressure measurement based on pulse wave transit time and blood pressure measurement by the oscillometric method can be performed with a single device, which is highly convenient for the user. Furthermore, since the second blood pressure measurement unit 140 is integrated with the first blood pressure measurement unit 130 and the blood pressure calculation formula is calibrated based on the measured blood pressure values ​​obtained by the second blood pressure measurement unit 140, the blood pressure measurement device 10 can calibrate the blood pressure calculation formula by itself. Therefore, the blood pressure calculation formula can be easily calibrated.

[0096] Then, based on the results of continuous blood pressure measurement by the first blood pressure measurement unit 130, it is determined whether or not the user's actually measured blood pressure value should be acquired (i.e., whether or not the algorithm for calculating blood pressure values ​​needs to be calibrated), and if the condition is met, the user is notified that blood pressure measurement should be performed by the second blood pressure measurement unit 140. This allows the user to perform accurate blood pressure measurement under circumstances where blood pressure measurement is recommended.

[0097] Furthermore, the reference value of a predetermined feature, which is the criterion for determining whether or not to acquire an actual blood pressure value, is changed according to the difference between the actual blood pressure value and the estimated blood pressure value (i.e., the accuracy of the estimated blood pressure value), thereby optimizing the frequency of acquiring the actual blood pressure value. This makes it possible to provide a technology that can improve the accuracy of blood pressure estimation depending on the user by repeating the calibration of the blood pressure calculation algorithm and can optimize the frequency of calibration of the blood pressure calculation algorithm.

[0098] (Variation) In the above-described embodiment, the pulse wave sensor employs an impedance method that detects changes in impedance due to changes in arterial volume. However, the pulse wave sensor may employ other measurement methods, such as a photoelectric method, a piezoelectric method, or a radio wave method. In an embodiment employing the photoelectric method, the pulse wave sensor comprises a light-emitting element that irradiates light toward the artery passing through the measurement site, and a photodetector that detects reflected or transmitted light of the light, thereby detecting changes in light intensity due to changes in arterial volume. In an embodiment employing the piezoelectric method, the pulse wave sensor comprises a piezoelectric element attached to a belt that contacts the measurement site, thereby detecting changes in pressure due to changes in arterial volume. In an embodiment employing the radio wave method, the pulse wave sensor comprises a transmitting element that transmits radio waves toward the artery passing through the measurement site, and a photodetector that receives the reflected waves of the radio waves. and a receiving element for receiving the transmitted wave and the reflected wave, which detects a phase shift between the transmitted wave and the reflected wave that accompanies a change in the volume of the artery.

[0099] Blood pressure measurement device 10 may further include a pressure cuff for adjusting the contact state between sensor unit 1322 of pulse wave sensor 1321 and the upper arm, a pump for supplying air to this pressure cuff, a pump drive circuit for driving this pump, and a pressure sensor for detecting the pressure inside this pressure cuff. This pressure cuff is provided at distal end 1218C of belt 121. In this case, pressure cuff 1401 is provided at intermediate portion 1218B of belt 121, for example.

[0100] The components involved in measuring the pulse wave transit time may be implemented as a separate device. In one embodiment, a pulse wave transit time measuring device is provided that includes a belt unit 120, an electrocardiogram acquisition unit 131, a pulse wave signal acquisition unit 132, and a pulse wave transit time calculation unit 133. This pulse wave transit time measuring device may further include a calibration determination unit 150 and an instruction unit 160. The pulse wave transit time measuring device may further include a pressure cuff, a pump, and a pump drive circuit for pressing the electrode 1312 and the pulse wave sensor 1321 against the upper arm.

[0101] The blood pressure measurement device 10 does not have to include the second blood pressure measurement unit 140. In an embodiment in which the blood pressure measurement device 10 does not include the second blood pressure measurement unit 140, it is necessary to input blood pressure values ​​obtained by measurement with another sphygmomanometer into the blood pressure measurement device 10 in order to calibrate the blood pressure calculation formula.

[0102] <Embodiment 2> In the first embodiment, the present invention is applied to a blood pressure measurement device in which all functions, including a memory unit, a blood pressure value calculation unit, and a display unit, are integrated into a single device, but the present invention can also be applied to a blood pressure measurement system in which some of these components and functions are separated. Examples of such blood pressure measurement systems are shown in Figures 8 and 9.

[0103] FIG. 8 shows an outline of a blood pressure measurement system 2 according to this embodiment. As shown in FIG. 8, the blood pressure measurement system 2 includes a sensor device 21 worn on the upper arm of a user and an information processing terminal 22 that processes biological information acquired by the sensor device 21. The sensor device 21 is a wearable device that includes a plurality of electrodes (electrocardiogram sensors) and a pulse wave sensor (not shown), and is used by being fixed to the upper arm of the user by a fixing means such as a belt. The information processing terminal 22 may be any device that can communicate with the sensor device 21. For example, as shown in FIG. 8, a smartphone can be used as the information processing terminal 22.

[0104] 9 is a block diagram showing the functional configuration of the sensor device 21 and the information processing terminal 22 of the blood pressure measurement system 2. The sensor device 21 has functional units, namely, an electrode unit 211, a pulse wave sensor unit 212, a control unit 210, a storage unit 213, an operation unit 214, a power supply unit 215, and a communication unit 216. The control unit 210 also has, as its functional modules, an electrocardiogram acquisition unit 201 and a pulse wave signal acquisition unit 202.

[0105] The pulse wave sensor unit 212 and pulse wave signal acquisition unit 202 in the sensor device 21 may employ, for example, a photoelectric method. Specifically, the sensor device 21 includes a light-emitting element that irradiates light toward an artery passing through the measurement site, and a photodetector that detects the reflected or transmitted light, and detects changes in light intensity associated with changes in the arterial volume (neither is shown). The electrode unit 211 and electrocardiogram acquisition unit 201 may have the same configuration as those in the blood pressure measurement device 10 of the first embodiment, and therefore detailed description thereof will be omitted.

[0106] The storage unit 213 only has a main storage device such as a RAM or a ROM, and has a limited storage capacity. The operation unit 214 also has a limited configuration such as a power switch, and is simply configured. The power supply unit 215 can be, for example, a rechargeable secondary battery. The communication unit 216 includes a wired communication module and / or a wireless communication module. The connection terminal for wired communication may also serve as a charging terminal for the power supply unit 215.

[0107] As described above, sensor device 21 in this embodiment has only a very limited function for acquiring biological information for calculating an estimated blood pressure value. Therefore, the electrocardiogram signal and pulse wave signal measured by each sensor unit are transmitted in real time to information processing terminal 22 via communication unit 216.

[0108] The information processing terminal 22 includes functional units such as a control unit 220, a display unit 225, an operation unit 226, a communication unit 227, and a memory unit 228. The control unit 220 also includes functional modules such as a blood pressure value calculation unit 221, a calibration determination unit 222, an actual blood pressure value acquisition unit 223, and a calibration processing unit 224.

[0109] The information processing terminal 22 communicates with the sensor device 22 via the communication unit 227, and receives the electrocardiogram signal and pulse wave signal of the user measured by the sensor device 21. There are no particular limitations on the communication standard, but communication can be performed using wireless communication standards such as Bluetooth (registered trademark), Wi-Fi (registered trademark), and infrared communication. The hardware configuration of the information processing terminal 22 is the same as that of a smartphone, and for example, a touch panel display serves as both the display unit 225 and the operation unit 226.

[0110] The biological information received from the sensor device 21 via the communication unit 227 is stored in the storage unit 228, and various processes such as calculation of an estimated blood pressure value are performed based on the stored information. Note that, like the storage unit 1505 of the blood pressure measurement device 10 of the first embodiment, the storage unit 228 stores not only electrocardiogram and pulse wave signals but also information such as an algorithm for calculating blood pressure values, a reference value for determining whether calibration is required, estimated blood pressure values, and actually measured blood pressure values.

[0111] The blood pressure value calculation unit 221, the calibration determination unit 222, and the calibration processing unit 224 are functional modules that perform the calculation process of an estimated blood pressure value, the determination process of whether or not algorithm calibration is necessary using the actually measured blood pressure value, the calibration process of the algorithm for blood pressure calculation, and the reference value change process for determining whether or not calibration is necessary, similar to the blood pressure measurement device 10 of embodiment 1. These processes are the same as those of embodiment 1, so further explanation will be omitted here.

[0112] The actual blood pressure value acquiring unit 223 executes a process of acquiring the actual blood pressure value when the calibration determining unit 222 determines that calibration of the blood pressure calculation algorithm using the actual blood pressure value is necessary. In this embodiment, the user is notified to input the actual blood pressure value, for example, via the display unit 225 or a speaker (not shown). The user measures the actual blood pressure value using another device (not shown) capable of accurate blood pressure measurement, such as an oscillometric method, and inputs the blood pressure value into the information processing terminal 22 by operating the operation unit 226. That is, the actual blood pressure value acquiring unit 223 acquires the actual blood pressure value via the operation unit 226. The acquired actual blood pressure value is stored in the storage unit 228.

[0113] In the blood pressure measurement system 2 of this embodiment, sensing of biological information (e.g., electrocardiogram and pulse wave signals) for continuously calculating estimated blood pressure values ​​is performed by a sensor device 21, and actual blood pressure value calculation processing, calibration necessity determination processing, algorithm calibration processing, etc. are performed by an information processing terminal 22. This configuration simplifies the configuration of the wearable device and further reduces the burden on the user associated with wearing the device. Furthermore, since it is possible to utilize an already existing information processing terminal such as a smartphone, the cost of introducing the system to the user can be reduced.

[0114] <Embodiment 3> In the above embodiment, an example was described in which blood pressure is measured continuously on a daily basis using a wearable dedicated blood pressure measurement device, but the present invention can also be implemented without using such a dedicated blood pressure measurement device. Figures 10 and 11 show examples of blood pressure measurement systems in such cases.

[0115] FIG. 10 shows an outline of a blood pressure measurement system 3 according to this embodiment. As shown in FIG. 10, the blood pressure measurement system 3 is configured such that a body composition monitor 31, a blood pressure measurement device 32, and a server 33 are connected via a communication network N. The communication network N may be, for example, a WAN (Wide Area Network), which is a global public communication network such as the Internet. The communication network N may include a telephone communication network such as a mobile phone network, or a wireless communication network such as Wi-Fi (registered trademark).

[0116] Body composition monitor 31 generally comprises a main body 31A and a handle 31B. Although not shown, it also includes a communication means for communication, as well as sensors (e.g., strain gauges, electrodes, velocity sensors, etc.) for acquiring various types of biological information such as body weight, body fat percentage, electrocardiogram, pulse wave signal, and ballistocardiogram (BCG), an output unit such as a liquid crystal display, an input unit such as operation buttons, a power supply, etc.

[0117] The blood pressure measuring device 32 is a typical home blood pressure measuring device having a main body 32A and a cuff 32B, and is equipped with various elements for measuring blood pressure by the oscillometric method, such as a pressure sensor, a pressure cuff, and a pump, as well as an output unit such as a liquid crystal display and an input unit such as operation buttons.

[0118] The server 33 is configured by a general server computer, and includes a processor such as a CPU, a main storage device such as a RAM or a ROM, and an auxiliary storage device such as an EPROM, a HDD, or a removable medium.

[0119] 11 is a block diagram showing the functional configuration of blood pressure measurement system 3. The body composition monitor includes electrocardiogram acquisition unit 311, pulse wave signal acquisition unit 312, pulse wave transit time calculation unit 313, blood pressure value calculation unit 314, calibration determination unit 315, storage unit 316, and communication unit 317.

[0120] The electrocardiogram acquisition unit 311 acquires an electrocardiogram of the user via electrodes arranged on the top surface of the main body 31A and the handle 31B of the body composition monitor 31. The pulse wave signal acquisition unit 312 acquires a pulse wave signal ( peripheralThe pulse wave sensor may be of an impedance type or a photoelectric type. The acquired electrocardiogram and pulse wave signals are stored in the storage unit 316. In addition to this biological information, the storage unit 316 also stores a blood pressure calculation algorithm, a determination reference value for whether calibration is required, and the like, as in the blood pressure measurement device 10 of the first embodiment.

[0121] The pulse wave transit time calculation unit 313 reads out the electrocardiogram and pulse wave signal from the storage unit 316 and calculates the pulse wave transit time based on the time difference between the waveform characteristic points of the electrocardiogram and the waveform characteristic points of the pulse wave signal. The blood pressure value calculation unit 314 calculates the blood pressure value based on the calculated pulse wave transit time and the blood pressure calculation algorithm stored in the storage unit 316. The calibration determination unit 315 determines whether or not the blood pressure calculation algorithm should be calibrated based on the calculated pulse wave transit time and a predetermined reference value stored in the storage unit 316. These processes are the same as those in the blood pressure measurement device 10 of embodiment 1, so detailed description thereof will be omitted here.

[0122] When the calibration determination unit 315 determines that calibration of the blood pressure calculation algorithm is necessary, it notifies the user of this fact via a display unit (not shown) and transmits the estimated blood pressure value when it is determined that calibration is necessary to the server 33 via the communication unit 317 and the network N. do.

[0123] The blood pressure measurement device 32 includes, as functional units, a blood pressure measurement unit 321 and a communication unit 322. The blood pressure measurement unit 321 is a functional unit that performs accurate blood pressure measurement using a method such as an oscillometric method. implementation The second blood pressure measurement unit 321 can have the same configuration as the second blood pressure measurement unit 140 in the blood pressure measurement device 10 of Form 1, and therefore description thereof will be omitted here. The actual blood pressure values ​​measured by the blood pressure measurement unit 321 are transmitted to the server 33 via the communication unit 322 and the network N.

[0124] The server 33 includes functional units, such as a calibration processing unit 331, a storage unit 332, and a communication unit 333. Information (such as estimated blood pressure values ​​and measured blood pressure values) transmitted from the body composition monitor 31 and the blood pressure measurement device 32 and received by the communication unit 333 is stored in the storage unit 332. The calibration processing unit 331 performs processing for calibrating the blood pressure calculation algorithm of the body composition monitor 31 based on the estimated blood pressure values ​​and measured blood pressure values ​​stored in the storage unit 332. Specifically, the calibration processing unit 331 calculates more appropriate parameter values ​​based on the estimated blood pressure values ​​and measured blood pressure values, and transmits data of the new parameters calculated in this way to the body composition monitor 31 via the communication unit 333 and the network N. The blood pressure calculation algorithm stored in the storage unit 316 of the body composition monitor 31 is then updated to a new algorithm using the new parameters, thereby calibrating the blood pressure calculation algorithm.

[0125] As in the first and second embodiments, the calibration processing unit 331 also executes a process of changing the reference value used in the determination process performed by the calibration determination unit 315. In this case, as in the calibration of the algorithm, the server 33 calculates a new reference value, transmits the calculated new reference value to the body composition monitor 31, and stores the new reference value in the storage unit 316, thereby changing the reference value.

[0126] As described above, in the blood pressure measurement system 3 of this embodiment, the acquisition of biological information for calculating estimated blood pressure values ​​is performed using a general-purpose body composition monitor 31 rather than a dedicated device. Furthermore, the function of the calibration processing unit 331 is not provided in the body composition monitor 31 but is instead executed by the server 33. This eliminates the need for complex arithmetic processing for algorithm calibration on the measurement device side, allowing blood pressure measurements (estimations) to be performed using a general-purpose body composition monitor, and the algorithm can also be calibrated as needed. In other words, high accuracy of estimated blood pressure values ​​can be maintained even when using a general-purpose body composition monitor. In this embodiment, the body composition monitor 31 is configured to include a handle 31B, but it is also possible to use a body composition monitor that does not include a handle 31B.

[0127] <Other> The above-described embodiments merely exemplify the present invention, and the present invention is not limited to the specific embodiments described above. Various modifications and combinations of the present invention are possible within the scope of the technical concept thereof. For example, in the above examples, the feature used to determine whether calibration of the blood pressure calculation algorithm is necessary is the pulse wave transit time. However, the determination of whether calibration of the algorithm is necessary may be based on other feature values. For example, in the third embodiment, information such as weight, BMI, ballistocardiogram, and pulse wave velocity (PWV) can be acquired from various sensors provided in the body composition monitor 31, and these feature values ​​can also be used to estimate blood pressure. In other words, these feature values ​​can also be used to determine whether calibration of the algorithm is necessary. Other feature values ​​that may be used to determine whether calibration of the algorithm are necessary include the height of the inflection points of the pulse wave or electrocardiogram, the slope between two inflection points, the area between the two inflection points, and the ratio of these. Heartbeat-related information (e.g., the difference from the previous beat, the average value of the beat, and the like) can also be used. of The features may include the user's personal attribute information (height, age, medication history, etc.), information related to the situation at the time of measurement (user's activity level, posture, etc.), and environmental information (season, external temperature, etc.).

[0128] Furthermore, in the above-described first embodiment, when the reference value is the upper and lower thresholds for the pulse wave propagation time, both the upper and lower limit values ​​are changed. However, the change of the reference value is not limited to this, and various patterns can be set. For example, the reference value can be set as only the upper threshold or only the lower threshold. When the reference value is set as the lower threshold, increasing the reference value can increase the frequency of calibration, and decreasing the reference value can decrease the frequency of calibration. Furthermore, when the reference value is the upper and lower thresholds, only the upper threshold or only the lower threshold may be changed. Even in such a case, the width of the numerical range in which the feature should fall can be changed, and the frequency of calibration can be changed accordingly.

[0129] Furthermore, the device for measuring biological information is not limited to those exemplified in the above embodiments, and may be, for example, a device such as a so-called smart watch. Furthermore, the measurement site is not limited to the upper arm or wrist, and measuring devices that can be worn on other sites such as the thigh or ankle may also be used. [Explanation of symbols]

[0130] 10...blood pressure measuring device, 120...belt portion, 121...belt, 122...main body, 130...first blood pressure measurement unit, 131...electrocardiogram acquisition unit, 132...pulse wave signal acquisition unit, 133...pulse wave transit time calculation unit, 134...blood pressure value calculation unit, 140... second blood pressure measurement unit, 150... calibration determination unit, 160... instruction unit, 1210A...inner cloth, 1210B...outer cloth, 1213...loop surface, 1214...hook surface, 1221...operation unit, 1222...display unit, 1311...electrode group, 1312...electrodes, 1313...switch circuit, 1314...subtraction circuit, 1315...analog front end, 1321...pulse wave sensor, 1322...sensor unit, 1323A to 1323D...electrodes, 1324...energization and voltage detection circuit, 1401...pressure cuff, 1402...pressure sensor, 1403...pump, 1404...valve, 1405...oscillating circuit, 1406...pump drive circuit, 1501...control unit, 1502...CPU, 1503...RAM, 1504...ROM, 1505...storage unit, 1506...battery, 1507...communication unit, 1601...Electrocardiogram measurement control unit, 1602...Electrocardiogram storage unit, 1603...Pulse wave measurement control unit, 1604...Pulse wave signal storage unit, 1605...Blood pressure calculation formula storage unit, 1606...Estimated blood pressure value storage unit, 1607...Display control unit, 1608...Blood pressure measurement control unit, 1609...Actual blood pressure value storage unit, 1610...Instruction input unit, 1611...Calibration judgment reference value storage unit UA...brachial artery, UAA...brachial artery, UAB...humerus 2, 3...Blood pressure measurement system 21...sensor device, 22 information processing terminal 31...body composition monitor, 31A...main body, 31B...handle 32...blood pressure measuring device, 32A...main body, 32B...cuff 33...Server N...Network

Claims

1. a feature acquisition unit that acquires one or more feature amounts related to the estimation of a blood pressure value of a human body; a blood pressure value calculation unit that calculates an estimated blood pressure value based on at least one of the feature amounts; an actual blood pressure value acquisition unit that acquires an actual blood pressure value measured by a method different from that calculated by the blood pressure value calculation unit; a calibration determination unit that determines whether the feature acquired by the feature acquisition unit deviates from a predetermined reference value, and, if it is determined that the feature deviates, determines to acquire the actual blood pressure value; a calibration processing unit that calibrates the calculation algorithm by changing parameters of the calculation algorithm of the estimated blood pressure value using the actual blood pressure value so that the estimated blood pressure value calculated by the blood pressure value calculation unit becomes a value closer to the actual blood pressure value, the calibration processing unit changes the reference value based on a difference between the actual blood pressure value acquired by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount deviating from the reference value, and a predetermined threshold value related to the difference, so as to increase or decrease the frequency of acquiring the actual blood pressure value in accordance with a relationship between the threshold value and the difference; the feature amount acquired by the feature amount acquiring unit includes at least a pulse wave transit time, and the blood pressure value calculating unit calculates the estimated blood pressure value based on at least the pulse wave transit time; A blood pressure measuring device.

2. When a difference between the actual blood pressure value acquired by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount deviating from the reference value is equal to or less than a predetermined threshold, the calibration processing unit changes the reference value to a value that reduces the frequency with which the actual blood pressure value is determined to be acquired.

2. The blood pressure measuring device according to claim 1 .

3. The calibration processing unit If the reference value is an upper limit threshold for the feature amount, the value of the reference value is increased; If the reference value is the lower limit threshold for the feature, the value of the reference value is decreased. height, If the reference value is an upper or lower threshold that defines a numerical range for the feature amount, increasing the upper threshold and / or decreasing the lower threshold.

3. The blood pressure measuring device according to claim 2.

4. When a difference between the actual blood pressure value acquired by the determination of the calibration determination unit and the estimated blood pressure value calculated using the feature amount deviating from the reference value exceeds a predetermined threshold, the calibration processing unit changes the reference value to a value that increases the frequency with which the actual blood pressure value is determined to be acquired.

2. The blood pressure measuring device according to claim 1 .

5. The calibration processing unit If the reference value is an upper threshold value for the feature amount, the reference value is decreased; If the reference value is a lower limit threshold for the feature amount, the value of the reference value is increased; If the reference value is an upper or lower threshold that defines a numerical range for the feature amount, the upper threshold is decreased and / or the lower threshold is increased.

5. The blood pressure measuring device according to claim 4.

6. further comprising an output means, When the calibration determination unit determines to acquire the measured blood pressure value, the output unit outputs information indicating that the measured blood pressure value should be acquired. The blood pressure measuring device according to any one of claims 1 to 5.

7. further comprising a blood pressure measuring means for measuring the actual blood pressure value, When the calibration determination unit determines to acquire the actual blood pressure value, the actual blood pressure value acquisition unit acquires the actual blood pressure value by measuring the actual blood pressure value using the blood pressure measurement means.

7. The blood pressure measuring device according to claim 1, wherein the blood pressure measuring device comprises: a first electrode;

8. The blood pressure measuring device further includes a blood pressure measuring means for measuring the actual blood pressure value and an operation input means, the actual blood pressure value acquisition unit, when receiving an input instructing measurement of the actual blood pressure value via the operation input means, acquires the actual blood pressure value by measuring the actual blood pressure value using the blood pressure measurement means; 7. The blood pressure measuring device according to claim 1, wherein the blood pressure measuring device comprises: a first electrode;

9. a feature acquisition means for acquiring one or more feature values ​​related to the estimation of a blood pressure value of a human body; a blood pressure value calculation means for calculating an estimated blood pressure value based on at least one of the feature amounts; an actual blood pressure value acquisition means for acquiring an actual blood pressure value measured by a method different from that calculated by the blood pressure value calculation means; a calibration determination means for determining whether the feature acquired by the feature acquisition means deviates from a predetermined reference value, and for determining to acquire the actual blood pressure value if it is determined that the feature has deviated; and a calibration processing means for calibrating the calculation algorithm by changing parameters of the calculation algorithm of the estimated blood pressure value using the actual blood pressure value so that the estimated blood pressure value calculated by the blood pressure value calculation means becomes a value closer to the actual blood pressure value, The calibration processing means calculates the actual blood pressure value in accordance with a relationship between the threshold and the difference, based on a difference between the actual blood pressure value obtained by the determination of the calibration determination means and the estimated blood pressure value calculated using the feature amount deviating from the reference value, and a predetermined threshold related to the difference. changing the reference value so as to increase or decrease the frequency of obtaining the the feature amount acquired by the feature amount acquiring means includes at least a pulse wave transit time, and the blood pressure value calculating means calculates the estimated blood pressure value based on at least the pulse wave transit time; A blood pressure measurement system comprising:

10. The blood pressure measurement system includes: a measuring device including one or more sensors for detecting at least the feature amount; and an information processing device including at least the calibration processing means.

10. The blood pressure measurement system according to claim 9.

11. The measuring device further includes a blood pressure measuring means for measuring the actual blood pressure value.

11. The blood pressure measurement system according to claim 10.

12. The measuring device is a wearable device that can be permanently attached to the human body.

12. The blood pressure measurement system according to claim 10 or 11.

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