Blood pressure estimation device and calibration method

Abstract

To provide a blood pressure estimation device capable of accurately estimating a blood pressure on the basis of a circulatory organ related feature amount.SOLUTION: A blood pressure estimation device comprises: a blood pressure estimation part for acquiring a feature amount related to a state of a circulatory organ, the feature amount being a circulatory organ related feature amount which is varied according to a beating of a heart, and calculating a blood pressure value on the basis of the circulatory organ related feature amount; a reference blood pressure measuring part including, a sound wave detecting part for detecting Korotkoff sound generated according to the beating, and measuring a reference blood pressure value using the Korotkoff sound. The blood pressure estimation prat comprises: a feature amount acquiring part for acquiring the circulatory organ related feature amount; a correspondence determining part for determining a correspondence between the reference blood pressure value, and an acquired value of the circulatory organ related feature amount corresponding to a specific beat corresponding to the Korotkoff sound in which the reference blood pressure value in the beating is measured; and an estimated blood pressure acquiring part for calculating the blood pressure value on the basis of the correspondence, from the circulatory organ related feature amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a blood pressure estimation device and a calibration method for calculating blood pressure based on circulatory system-related features. [Background technology]

[0002] Conventionally, an upper arm or wrist type blood pressure monitor using an oscillometric method has been used as a means for calibrating a blood pressure estimation device based on circulatory organ-related features (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 168790 Summary of the Invention [Problem to be solved by the invention]

[0004] The oscillometric method calculates a single blood pressure value from the entire time series of multiple pulse pressure amplitude values ​​measured while the cuff is inflated. Meanwhile, multiple circulatory system-related features used to estimate blood pressure are generally acquired while the cuff is inflated. Therefore, if the circulatory system-related features fluctuate during measurement of the reference blood pressure value used for calibration, the one-to-one correspondence between the circulatory system-related features and the reference blood pressure value will no longer be one-to-one, resulting in incorrect calibration and a deterioration in the accuracy of blood pressure value estimation.

[0005] In view of the above-mentioned problems of the conventional techniques, an object of the present invention is to provide a blood pressure estimation device and a calibration method that are capable of highly accurate blood pressure estimation based on circulatory system-related features. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides: a blood pressure estimation unit that acquires a feature related to a circulatory system state, the feature changing according to heartbeat, and calculates a blood pressure value from the feature; a reference blood pressure measuring unit including an ultrasonic wave detecting unit that detects Korotkoff sounds generated in response to the pulsation and that measures a reference blood pressure value using the Korotkoff sounds; A blood pressure estimation device comprising: The blood pressure estimation unit a feature acquisition unit that acquires the circulatory system-related feature; a correspondence relationship determining unit that determines a correspondence relationship between the reference blood pressure value and an acquired value of the circulatory organ-related feature corresponding to a specific beat corresponding to the Korotkoff sound at which the reference blood pressure value in the pulse is measured; an estimated blood pressure acquisition unit that calculates the blood pressure value from the circulatory system-related feature amount based on the correspondence relationship; The present invention is characterized by the following features.

[0007] According to this, the blood pressure value is calculated from the circulatory system-related feature quantity based on the correspondence between the reference blood pressure value measured using Korotkoff sounds generated in response to heartbeats and the acquired value of the circulatory system-related feature quantity corresponding to the specific beat corresponding to the Korotkoff sound at which the reference blood pressure value for that beat was measured, thereby enabling blood pressure to be calculated with high accuracy.

[0008] In addition, in the present invention, The feature amount acquiring unit may include a pulse wave detecting unit that detects a pulse wave.

[0009] This allows various indices that can be obtained based on the pulse wave to be used as circulatory organ-related feature amounts.

[0010] In addition, in the present invention, The feature acquisition unit may include a first pulse wave detection unit and a second pulse wave detection unit that detect pulse waves at two points where the pulse waves arrive at different times, and may acquire a pulse wave propagation time between the two points as the circulatory system-related feature.

[0011] This allows for highly accurate estimation of blood pressure values ​​using PTT (Pulse Transit Time), which indicates the pulse wave propagation time between two points where the pulse wave arrives at different times, as a circulatory system-related feature.

[0012] In addition, in the present invention, The feature acquisition unit may include an electrocardiogram detection unit that detects an electrocardiogram and a vibration detection unit that detects vibrations caused by the pulsation, and may acquire a pulse wave propagation time as the circulatory system-related feature using the pulse wave, the electrocardiogram, and the vibrations.

[0013] This allows for highly accurate estimation of blood pressure using PTT, which can be acquired based on the pulse wave, electrocardiogram, and vibrations caused by heartbeats as circulatory system-related features. Here, vibrations caused by heartbeats include, but are not limited to, sound waves and ballistocardiograms.

[0014] In addition, in the present invention, The vibration detection unit may be the sound wave detection unit.

[0015] This allows for highly accurate estimation of blood pressure values ​​using PTT, which can be obtained based on sound waves, which are vibrations caused by pulsation, detected by the vibration detection unit, pulse waves, and an electrocardiogram.

[0016] In addition, in the present invention, The blood pressure estimation unit and the reference blood pressure measurement unit may be integrally configured.

[0017] This makes it possible to provide an easy-to-use biological state estimation device in which the blood pressure estimation section and the reference blood pressure measurement section are integrated.

[0018] The present invention also provides A method for calibrating a blood pressure estimation device that calculates a blood pressure value from a circulatory organ-related feature quantity based on a correspondence relationship between the circulatory organ-related feature quantity, which is related to a state of the circulatory organ and changes according to heartbeat, and the blood pressure value, comprising: detecting Korotkoff sounds generated in response to the pulsation; measuring a reference blood pressure value using the Korotkoff sounds; acquiring the circulatory system-related feature corresponding to a specific beat corresponding to the Korotkoff sound at which the reference blood pressure value in the pulse is measured; determining a correspondence relationship between the reference blood pressure value and the acquired circulatory system-related feature; A method for calibrating a blood pressure estimation device, comprising:

[0019] According to this method, a reference blood pressure value, which is referred to when calibrating the correspondence used in a blood pressure estimation device that calculates blood pressure values ​​from circulatory organ-related features based on the correspondence between circulatory organ-related features and blood pressure values, is measured using Korotkoff sounds generated in response to heartbeats, and the circulatory organ feature corresponding to the specific beat corresponding to the Korotkoff sound at which the reference blood pressure value is measured is calculated. Then, the correspondence relationship between the reference blood pressure value and the calculated circulatory system-related feature is determined, so that a calibration method can be provided that can achieve highly accurate blood pressure estimation from the circulatory system-related feature. [Effects of the Invention]

[0020] According to the present invention, it is possible to estimate blood pressure with high accuracy based on circulatory system-related features. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a functional block diagram of a blood pressure estimation device according to a first embodiment. [Figure 2] FIG. 2 is a flowchart illustrating a procedure of the calibration process according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the calibration process according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a correspondence relationship used in the calibration process according to the first embodiment. [Figure 5] FIG. 5 is a flowchart illustrating a procedure of the calibration process according to the second embodiment. [Figure 6] FIG. 6 is a diagram illustrating the calibration process according to the second embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of a correspondence relationship used in the calibration process according to the second embodiment. [Figure 8] FIG. 8 is a functional block diagram of a blood pressure estimation device according to the third embodiment. [Figure 9] FIG. 9 is a diagram illustrating the external configuration of a blood pressure estimation device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0023] Example 1 An example of an embodiment of the present invention will be described below. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this example are not intended to limit the scope of the present invention to those only.

[0024] (Configuration of blood pressure estimation device) FIG. 1 is a functional block diagram of a blood pressure estimation device 1 according to a first embodiment. The blood pressure estimation device 1 measures PTT (Pulse Transit Time) as a characteristic quantity related to the circulatory system (hereinafter referred to as "circulatory system-related characteristic quantity") to calculate blood pressure. PTT is the propagation time of a pulse wave between two different points in an artery.

[0025] The blood pressure estimation device 1 includes a blood pressure estimation unit 100 and a reference blood pressure measurement unit 200. The blood pressure estimation unit 100 is a functional unit that acquires a PTT and calculates blood pressure from the acquired PTT, and the reference blood pressure measurement unit 200 is a functional unit that measures with high accuracy a blood pressure that is referenced when calibrating the correspondence relationship between PTT and blood pressure, which will be described later.

[0026] (Blood pressure estimation section) The blood pressure estimation unit 100 includes a first pulse wave sensor 101, a second pulse wave sensor 102, a feature amount calculation unit 103, a storage unit 104, a relationship determination unit 105, and an estimated blood pressure acquisition unit 106. The feature calculation unit 103, the storage unit 104, the relationship determination unit 105, and the estimated blood pressure acquisition unit 106 are actually configured to include a processor such as a CPU, and a memory used as a working area for the processor and a storage area for programs and data executed by the processor, and the above-mentioned functional units are realized by the processor executing a predetermined program.

[0027] The first pulse wave sensor 101 and the second pulse wave sensor 102 are sensors that detect pulse waves, which are waveforms that capture changes in arterial pulse caused by heartbeats. Here, the pulse waves include a pressure pulse wave, which is a waveform of changes in internal pressure in the artery, and a volume pulse wave, which is a waveform of changes in arterial volume. Pulse wave sensors that detect pressure pulse waves include the tonometry type and the piezoelectric type that uses a piezoelectric sensor. Pulse wave sensors that detect volume pulse waves include the impedance type that detects changes in impedance, the photoelectric type that detects changes in volume from reflected or transmitted light using a light-emitting element and a light-receiving element, and the transmission type that uses a transmitting element that transmits radio waves and a receiving element that receives reflected waves. wave There are methods such as radio wave irradiation, which detects volume changes as a phase shift between the reflected wave and the measured volume. The locations on the subject where first pulse wave sensor 101 and second pulse wave sensor 102 should be placed can be set as appropriate, but they should be placed at locations where the pulse wave arrival times for the same beat are different, such as placing first pulse wave sensor 101 closer to the heart and second pulse wave sensor 102 farther from the heart, i.e., first pulse wave sensor 101 upstream of the artery and second pulse wave sensor 102 downstream. Here, first pulse wave sensor 101 and second pulse wave sensor 102 correspond to the first pulse wave detection unit and second pulse wave detection unit of the present invention, respectively, and both correspond to the pulse wave detection unit of the present invention.

[0028] The feature calculation unit 103 controls the first pulse wave sensor 101 and the second pulse wave sensor 102, and calculates the PTT by identifying the corresponding beat from the pulse waves detected by the first pulse wave sensor and the second pulse wave sensor (referred to as the first pulse wave and the second pulse wave, respectively) using a known method. Here, the first pulse wave sensor 101, the second pulse wave sensor 102, and the feature calculation unit 103 correspond to the feature acquisition unit of the present invention.

[0029] The storage unit 104 stores the first and second pulse waves in association with the times at which the pulse waves were detected. The storage unit 104 also acquires and stores data such as Korotkoff sounds, cuff pressure, systolic blood pressure, and diastolic blood pressure detected by the reference blood pressure measurement unit 200 (described later) from the reference blood pressure measurement unit 200.

[0030] The relationship determining unit 105 determines the correspondence relationship between the PTT and the systolic blood pressure (SBP) based on the systolic blood pressure (SBP) measured by the reference blood pressure measuring unit 200, as will be described later. (The PTT corresponding to the SBP is referred to as PTTsbp.) Here, the relationship determining unit 105 corresponds to the corresponding relationship determining unit of the present invention.

[0031] The estimated blood pressure acquisition unit 106 calculates blood pressure from the PTT calculated by the feature calculation unit 103, based on the correspondence between PTT and SBP acquired from the storage unit 104. Here, the estimated blood pressure acquisition unit 106 corresponds to the calibrated blood pressure acquisition unit of the present invention. And the blood pressure estimation unit 100 corresponds to the blood pressure estimation unit of the present invention.

[0032] (Reference blood pressure measurement unit) Reference blood pressure measuring unit 200 includes cuff 201, microphone 202, pressure sensor 203, valve 204, pump 205, systolic blood pressure determining unit 206, and diastolic blood pressure determining unit 207. Here, reference blood pressure measuring unit 200 corresponds to the reference blood pressure measuring unit of the present invention. Also, microphone 202 corresponds to the sound wave detecting unit of the present invention. The systolic blood pressure determination unit 206 and the diastolic blood pressure determination unit 207 are actually configured to include a processor such as a CPU, and a memory used as a working area for the processor and a storage area for programs and data executed by the processor, and the above-mentioned functional units are realized by the processor executing a predetermined program.

[0033] Reference blood pressure measurement unit 200 measures blood pressure by auscultation. In auscultation, Korotkoff sounds are generated when blood flow resumes after being inflated by cuff 201 and then depressurized, and are detected by microphone 202. Blood pressure is measured based on these Korotkoff sounds. By identifying the beats at which Korotkoff sounds are generated, it is possible to identify the time at which a beat corresponding to SBP occurred, making it possible to accurately measure blood pressure values ​​at each time point, even for very short-term blood pressure fluctuations such as respiratory fluctuations. The part of the subject where the cuff 201 should be placed is set to an appropriate part such as the wrist or upper arm. It can be determined.

[0034] Cuff 201 is a bag-shaped member capable of storing air therein. With a valve closed, air is sent into cuff 201 from pump 205 to pressurize cuff 201, and when the valve is opened while cuff 201 is in a pressurized state, air is discharged from cuff 201, thereby depressurizing cuff 201. Inside cuff 201, there are provided microphone 202 for detecting Korotkoff sounds and pressure sensor 203 for detecting the pressure inside cuff 201.

[0035] The systolic blood pressure determining unit 206 and the diastolic blood pressure determining unit 207 control the valve 204 and the pump 205, acquire the Korotkoff sounds detected by the microphone 202 and the cuff pressure detected by the pressure sensor 203, and determine the systolic blood pressure and the diastolic blood pressure, respectively, by a known auscultatory method.

[0036] In the blood pressure estimation device 1, the blood pressure estimation unit 100 and the reference blood pressure measurement unit 200 may be configured as an integrated unit or as separate units. The blood pressure estimation unit 100 and the reference blood pressure measurement unit 200 are connected by an appropriate wired or wireless communication means. For example, the blood pressure estimation device 1 can be configured with the blood pressure estimation unit 100 as a belt-like device worn around the upper arm and the reference blood pressure measurement unit 200 as a watch-like device worn around the wrist.

[0037] (Calibration procedure) FIG. 2 is a flowchart illustrating the procedure for calibrating the blood pressure estimation device 1 according to the first embodiment. FIG. 3 is a diagram illustrating the relationship between Korotkoff sounds, cuff pressure, and the first and second pulse waves. In FIG. 3, the time course of the horizontal axis is the same for Korotkoff sounds and cuff pressure, but the time course of these sounds and the time course of the horizontal axis for the first and second pulse waves are not necessarily the same, and the relative time relationship is shown. The calibration process shown in FIG. 2 corresponds to the calibration method of the present invention. In this embodiment, the correspondence between PTT and blood pressure is assumed to be a linear relationship expressed by a linear function as shown in Figure 4. The correspondence is determined by finding pairs of PTT and SBP at two points and fitting a straight line L1 connecting these two points.

[0038] First, the systolic blood pressure determination unit 206 determines SBP by auscultation (step S1). More specifically, the pump 205 is operated to inflate the cuff 201 to a predetermined pressure. This predetermined pressure is, for example, a value that exceeds the systolic blood pressure by a predetermined amount. In this way, inflating the cuff 201 to the predetermined pressure stops blood flow. From this state in which blood flow has stopped, the cuff 201 is gradually depressurized. When the cuff pressure decreases and blood flow resumes, Korotkoff sounds begin to occur. The first Korotkoff sound after this restart of blood flow is detected by a microphone (indicated by K1 in FIG. 3). The cuff pressure Cp1 when the Korotkoff sound K1 is detected is the SBP, so the SBP is determined based on the time the Korotkoff sound K1 is detected, as indicated by the dashed arrow A11 in FIG. 3. This SBP corresponds to the reference blood pressure value of the present invention.

[0039] Next, the relationship determining unit 105 determines the beat corresponding to the SBP from the first and second pulse waves stored in the storage unit 104, as indicated by the dashed arrow A12 in Fig. 3 (step S2). Here, the beat corresponding to the SBP is the beat closest to the time when the Korotkoff sound K1 was detected.

[0040] Next, the relationship determining unit 105 obtains the pulse wave interval PTTsbp between the first and second pulse waves for the beat determined in step S2, i.e., the time interval between Pw11 of the first pulse wave and Pw12 of the second pulse wave (step S3). The pulse wave interval obtained in this manner corresponds to SBP and is therefore referred to as PTTsbp. Here, PTTsbp corresponds to the obtained value of the circulatory system-related feature of the present invention.

[0041] Next, the relationship determining unit 105 determines whether or not PTTsbp corresponding to the two SBPs have been acquired (step S4). If only a PTTsbp corresponding to one SBP has been acquired, the process returns to step S1. Tori If it is obtained, the process proceeds to step S5.

[0042] Next, the relationship determining unit 105 fits a line L1 passing through two SBP points and corresponding PTTsbp to a pair (step S5). FIG. 4 is a graph illustrating an example of fitting, with SBP on the horizontal axis and PTTsbp on the vertical axis. As shown in FIG. 4, P11 indicates a point on which the SBP and PTTsbp obtained by the first processing of steps S1 to S3 are plotted, and P12 indicates a point on which the SBP and PTTsbp obtained by the second processing of steps S1 to S3 are plotted. The correspondence between SBP and PTTsbp can be represented, for example, by a line L1 passing through two points P11 and P12, as shown in FIG. 4.

[0043] By storing the fitted correspondence relationship (straight line L1) between SBP and PTTsbp in the memory unit 104 in this manner, the estimated blood pressure acquisition unit 106 can refer to this correspondence relationship and continuously calculate highly accurate SBP from the calculated PTT values ​​continuously obtained by the feature calculation unit 103. Furthermore, by using auscultation to obtain the SBP corresponding to a specific beat as a reference for calibrating the relationship between PTT and SBP, an accurate reference can be obtained at each time point even in the presence of blood pressure fluctuations such as respiratory fluctuations, enabling calibration processing to be completed in a short time.

[0044] The above-mentioned calibration of the relationship between PTT and SBP may be performed, for example, every 30 minutes to 1 hour, but the timing of the calibration is not limited to this. The calibration of the relationship between PTT and SBP may also be performed in response to a user instruction.

[0045] <Example 2> A blood pressure estimation device 2 according to a second embodiment of the present invention will be described below. The same reference numerals are used for the components common to the first embodiment, and detailed descriptions thereof will be omitted.

[0046] The functional block diagram of the blood pressure estimation device 2 is the same as that of the blood pressure estimation device 1 shown in Fig. 1. In Example 1, the correspondence relationship between PTT and blood pressure was calibrated using the systolic blood pressure SBP measured by auscultation, but in Example 2, the correspondence relationship between PTT and blood pressure is calibrated using the diastolic blood pressure DBP measured by auscultation.

[0047] (Calibration procedure) FIG. 5 shows a flowchart illustrating the procedure for calibrating the blood pressure estimation device 2 according to the second embodiment. FIG. 6 shows the relationship between Korotkoff sounds, cuff pressure, and the first and second pulse waves. In FIG. 6, the time course of the horizontal axis is the same for the Korotkoff sounds and cuff pressure, but the time course of these sounds and the time course of the horizontal axis for the first and second pulse waves are not necessarily the same, and the relative time relationship is shown. The calibration process shown in FIG. 5 corresponds to the calibration method of the present invention. In this embodiment, the correspondence between PTT and blood pressure is assumed to be a linear relationship expressed by a linear function as shown in Fig. 7. The correspondence is determined by finding pairs of PTT and DBP at two points and fitting a straight line L2 connecting these two points.

[0048] First, the diastolic blood pressure determining unit 207 determines DBP by auscultation (step S11). More specifically, the cuff is gradually depressurized from a predetermined pressure. This predetermined pressure can be set appropriately, but For example, the cuff pressure can be set to a value that is a predetermined value below the systolic blood pressure and at which Korotkoff sounds are generated. In this way, gradually reducing the pressure of the cuff from the predetermined pressure reduces the volume of the Korotkoff sounds detected by the microphone. Further reducing the pressure of the cuff causes the Korotkoff sounds to disappear (indicated by K2 in FIG. 6). Since the cuff pressure Cp2 at which the Korotkoff sounds K2 disappear is the DBP, the DBP is determined based on the time at which the Korotkoff sounds K2 disappear, as indicated by the dashed arrow A21 in FIG. 6. This DBP corresponds to the reference blood pressure value of the present invention.

[0049] Next, the relationship determining unit 105 determines the beat corresponding to the DBP from the first pulse wave and the second pulse wave stored in the storage unit 104, as indicated by the dashed arrow A22 in Fig. 6 (step S12). Here, the beat corresponding to the DBP is the beat closest to the time when the Korotkoff sound K2 disappeared.

[0050] Next, for the beat determined in step S12, the pulse wave interval PTTdbp between the first and second pulse waves, i.e., the time interval between Pw21 of the first pulse wave and Pw22 of the second pulse wave, is obtained (step S13). The pulse wave interval thus obtained corresponds to DBP and is therefore referred to as PTTdbp. Here, PTTdbp corresponds to the obtained value of the circulatory system-related feature of the present invention.

[0051] Next, the relationship determination unit 105 determines whether or not PTTdbp corresponding to two DBPs has been acquired (step S14). If only PTTdbp corresponding to one DBP has been acquired, the process returns to step S11. If PTTdbp corresponding to two DBPs has been acquired, the process proceeds to step S15.

[0052] Next, the relationship determining unit 105 fits a line L2 passing through two points to a pair of DBPs and corresponding PTTdbps (step S15). FIG. 7 is a graph illustrating an example of fitting, with DBP on the horizontal axis and PTTdbp on the vertical axis. As shown in FIG. 7, P21 denotes a point on which the DBPs and PTTdbps obtained by the first processing of steps S11 to S13 are plotted, and P22 denotes a point on which the DBPs and PTTdbps obtained by the second processing of steps S11 to S13 are plotted. The correspondence between DBPs and PTTdbps can be represented, for example, by a line L2 passing through two points P21 and P22, as shown in FIG. 7.

[0053] This is how it was fitted D BP and PTT d By storing the correspondence relationship (straight line L2) with bp in the memory unit 104, the estimated blood pressure acquisition unit 106 can refer to this correspondence and continuously calculate highly accurate DBP from the calculated PTT values ​​continuously obtained by the feature calculation unit 103. Furthermore, by using auscultation to obtain DBP corresponding to a specific beat as a reference for calibrating the relationship between PTT and DBP, an accurate reference can be obtained at each time point even in the presence of blood pressure fluctuations such as respiratory fluctuations, enabling calibration processing to be completed in a short time.

[0054] The above-mentioned calibration of the correspondence relationship between PTT and DBP may be performed, for example, every 30 minutes to 1 hour, but the timing of the calibration is not limited to this. The calibration of the correspondence relationship between PTT and DBP may also be performed in response to a user instruction.

[0055] Example 3 8 shows a functional block diagram of a blood pressure estimation device 3 according to Example 3. The same reference numerals are used for the components common to the blood pressure estimation device 1 according to Example 1, and detailed description thereof will be omitted. The blood pressure estimation device 3 has a configuration in which an electrocardiogram sensor 107 and a vibration sensor 108 are added to the blood pressure estimation device 1 according to the first embodiment. Although the pulse wave sensor 101 includes the motion sensor 108, it may be configured to include at least one of the electrocardiogram sensor 107 and the vibration sensor 108. Here, the first pulse wave sensor 101 (and the second pulse wave sensor 102), the electrocardiogram sensor 107, the vibration sensor 108, and the feature amount calculation unit 103 correspond to the feature amount acquisition unit of the present invention.

[0056] FIG. 9 shows a specific configuration example of the blood pressure estimation device 3. This blood pressure estimation device 3 is in the form of a belt worn around the upper arm, and the blood pressure estimation unit 100 and reference blood pressure measurement unit 200 are integrally configured. The electrocardiogram sensor 107 is placed on the subject-side surface along the shoulder-side edge of the blood pressure estimation device 3, which is worn around the upper arm. The vibration sensor 108 is also placed on the subject-side surface along the shoulder-side edge. The pulse wave sensor 101 (or the second pulse wave sensor 102) is placed on the subject-side surface along the elbow-side edge of the blood pressure estimation device 3. The cuff 201 is placed along the belt, and mechanical units such as the pump 205 and functional units such as the systolic blood pressure determination unit 206 and feature calculation unit 103 are housed in a main body 301.

[0057] The electrocardiogram sensor 107 and the pulse wave sensor 101 can be used to measure PAT (Pulse Arrival Time). PAT stands for pulse wave arrival time, and cardiac function can be evaluated by PAT. The electrocardiogram sensor 107 corresponds to the electrocardiogram detection unit of the present invention.

[0058] The PAT can be calculated as the interval between the time of the R wave of the electrocardiogram caused by the heartbeat detected by the electrocardiogram sensor 107 and the time of the rise of the pulse wave generated by the heartbeat detected by the pulse wave sensor.

[0059] The vibration sensor 108 is a sensor that detects vibrations caused by the beating of the heart, that is, vibrations that occur on the body surface when the vibrations caused by the beating of the heart are transmitted. As a cardiac sound sensor that detects sound waves that occur on the body surface when the vibrations caused by the beating of the heart are transmitted, the vibration sensor 108 can be specifically configured with a microphone. Also, as a ballistocardiogram sensor that detects a ballistocardiogram that is vibrations caused by the beating of the heart, the vibration sensor 108 can be specifically configured with an acceleration sensor, a piezoelectric sensor, or a strain gauge. The vibration detection method is not limited to this. The vibration sensor 108 can measure the PEP (Pulse-Ejection Period). PEP is the time it takes for the left ventricle to contract and open. The pre-ejection time is the time from the start of the pulse to the start of ejection into the aorta, and is also called the pre-ejection time. Furthermore, when a microphone is used as vibration sensor 108, it can be substituted for microphone 202, so by providing vibration sensor 108, microphone 202 can also be omitted. Vibration sensor 108 corresponds to the vibration detection unit of the present invention, and when a microphone is used as vibration sensor 108, it corresponds to the sound wave detection unit of the present invention.

[0060] By providing the electrocardiogram sensor 107, the vibration sensor 108, and the first pulse wave sensor 101, it is possible to calculate the PAT and PEP as described above. Since the relationship between PAT and PEP=PTT exists, the electrocardiogram sensor 107, the vibration sensor 108, and the first pulse wave sensor 101 can calculate the PTT as a circulatory system-related feature. When calculating SBP or DBP from the calculated PTT value, the SBP or DBP corresponding to a specific beat can be obtained using auscultation, as in the first or second embodiment, as a reference for calibrating the correspondence between PTT and SBP or DBP. This allows an accurate reference to be obtained at each time point, even in the presence of blood pressure fluctuations such as respiratory fluctuations, and enables calibration processing in a short time. Furthermore, since the PTT can be measured without providing two pulse wave sensors, one pulse wave sensor can be reduced, thereby enabling power saving.

[0061] <Modification> In the first, second and third embodiments, PTT, PAT and PEP are described as the circulatory organ-related feature quantities, but the circulatory organ-related feature quantities are not limited to these. As the quantities, PWV (Pulse Wave Velocity), AI (Augmentation Index), LVET (Left Ventricular Ejection Time), blood pressure, heart rate, and heartbeat interval can also be applied. where PPWV is pulse wave velocity, AI is augmentation index, and LVET is left ventricular ejection time. [Explanation of symbols]

[0062] 1, 2, 3... Blood pressure estimation device 100 Blood pressure estimation section 200 Reference blood pressure measurement unit 101: First pulse wave sensor 102 Second pulse wave sensor 103 Feature calculation unit 105 Relationship determination unit 106 Estimated blood pressure acquisition unit 108 Vibration sensor

Claims

1. a blood pressure estimation unit that acquires a feature related to a circulatory system state, the feature changing according to heartbeat, and calculates a blood pressure value from the feature; a reference blood pressure measuring unit including an ultrasonic wave detecting unit that detects Korotkoff sounds generated in response to the pulsation and that measures a reference blood pressure value using the Korotkoff sounds; A blood pressure estimation device comprising: The blood pressure estimation unit a feature acquisition unit that acquires the circulatory system-related feature; a correspondence relationship determining unit that determines a correspondence relationship between the reference blood pressure value and an acquired value of the circulatory organ-related feature acquired for the beat that generated the Korotkoff sound and for which the reference blood pressure value in the beat was measured; an estimated blood pressure acquisition unit that calculates the blood pressure value from the circulatory system-related feature amount based on the correspondence relationship; A blood pressure estimation device comprising:

2. The blood pressure estimation device according to claim 1 , wherein the feature acquisition unit includes a pulse wave detection unit that detects a pulse wave.

3. 3. The blood pressure estimation device according to claim 2, wherein the feature amount acquisition unit includes a first pulse wave detection unit and a second pulse wave detection unit that detect pulse waves at two points where the pulse waves arrive at different times, and acquires a pulse wave propagation time between the two points as the circulatory system-related feature amount.

4. 3. The blood pressure estimation device according to claim 2, wherein the feature acquisition unit includes an electrocardiogram detection unit that detects an electrocardiogram and a vibration detection unit that detects vibrations caused by the pulsation, and acquires a pulse wave transit time as the circulatory system-related feature using the pulse wave, the electrocardiogram, and the vibration.

5. 5. The blood pressure estimation device according to claim 4, wherein the vibration detection unit is the ultrasonic wave detection unit.

6. 6. The blood pressure estimation device according to claim 1, wherein the blood pressure estimation unit and the reference blood pressure measurement unit are integrally configured.

7. A method for calibrating a blood pressure estimation device that calculates a blood pressure value from a circulatory organ-related feature quantity based on a correspondence relationship between the circulatory organ-related feature quantity, which is related to a state of the circulatory organ and changes according to heartbeat, and the blood pressure value, comprising: detecting Korotkoff sounds generated in response to the pulsation; measuring a reference blood pressure value using the Korotkoff sounds; acquiring the circulatory system-related feature amount acquired for the pulse that generated the Korotkoff sound and for which the reference blood pressure value in the pulse was measured; determining a correspondence relationship between the reference blood pressure value and the acquired circulatory system-related feature; A method for calibrating a blood pressure estimation device, comprising:

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