Blood pressure estimation device and correction 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 cardiovascular-related feature quantities.

Background Art

[0002] Conventionally, as a means for calibrating a blood pressure estimation device based on cardiovascular-related feature quantities, an upper arm or wrist-type sphygmomanometer using an oscillometric method has been used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The oscillometric method is a method for calculating one blood pressure value from the entire time-series transition of a plurality of pulse pressure amplitude values measured during pressurization of a cuff. On the other hand, a plurality of cardiovascular-related feature quantities used for estimating blood pressure are generally acquired during pressurization of the cuff. Therefore, if the cardiovascular-related feature quantities vary during measurement of the reference blood pressure value referred to during calibration, the correspondence relationship between the cardiovascular-related feature quantities and the reference blood pressure value will not be one-to-one, and calibration will not be correctly performed, resulting in deterioration of the estimation accuracy of the blood pressure value.

[0005] In view of the problems of the prior art as described above, an object of the present invention is to provide a blood pressure estimation device and a calibration method capable of highly accurate blood pressure estimation based on cardiovascular-related feature quantities.

Means for Solving the Problems

[0006] To solve the above problems, the present invention A blood pressure estimation unit that acquires cardiovascular-related features, which are characteristics related to the state of the circulatory system and change in accordance with the heartbeat, and calculates a blood pressure value from said cardiovascular-related features, The unit includes a sound wave detection unit that detects Korotkoff sounds generated in response to the aforementioned pulsation, and a reference blood pressure measurement unit that measures a reference blood pressure value using the Korotkoff sounds, A blood pressure estimation device equipped with, The blood pressure estimation unit is A feature acquisition unit that acquires the aforementioned cardiovascular-related features, A correspondence relationship determination unit that determines the correspondence between the reference blood pressure value and the acquired value of the cardiovascular-related feature corresponding to a specific beat corresponding to the Korotkoff sound in which the reference blood pressure value was measured during the pulse, A blood pressure estimation unit calculates the blood pressure value based on the correspondence between the cardiovascular-related features and the above-mentioned cardiovascular features, It is characterized by having the following features.

[0007] According to this method, blood pressure can be calculated with high accuracy because it is based on the correspondence between a reference blood pressure value measured using Korotkoff sounds generated in response to the heartbeat and the acquired values ​​of cardiovascular-related features corresponding to a specific beat in which the reference blood pressure value for that beat corresponds to the Korotkoff sound measured.

[0008] Furthermore, in the present invention, The feature acquisition unit may also include a pulse wave detection unit for detecting pulse waves.

[0009] According to this, various indicators obtainable based on pulse waves can be used as cardiovascular-related features.

[0010] Furthermore, 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 with different arrival times, and may acquire the pulse wave propagation time between the two points as the cardiovascular-related feature.

[0011] According to this, it is possible to estimate blood pressure values ​​with high accuracy using PTT (Pulse Transit Time), which indicates the pulse wave propagation time between two points with different arrival times of pulse waves, as a cardiovascular-related feature.

[0012] Furthermore, in the present invention, The feature acquisition unit may include an electrocardiogram detection unit for detecting an electrocardiogram and a vibration detection unit for detecting vibrations caused by the heartbeat, and may acquire pulse wave propagation time using the pulse wave, the electrocardiogram, and the vibration as the cardiovascular-related feature quantities.

[0013] According to this, blood pressure values ​​can be estimated with high accuracy using PTT, which can be obtained based on pulse waves, electrocardiograms, and vibrations caused by heartbeats, as cardiovascular-related features. Here, vibrations caused by heartbeats include, but are not limited to, sound waves and cardiac elasticity.

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

[0015] According to this, it is possible to estimate blood pressure values ​​with high accuracy using PTT, which can be obtained based on sound waves (vibrations caused by pulsation) detected by the vibration detection unit, pulse waves, and an electrocardiogram.

[0016] Furthermore, in the present invention, The blood pressure estimation unit and the reference blood pressure measurement unit may be configured as an integrated unit.

[0017] According to this, it is possible to provide an easy-to-use biological state estimation device in which a blood pressure estimation unit and a reference blood pressure measurement unit are integrated.

[0018] Furthermore, the present invention is A method for calibrating a blood pressure estimation device that calculates blood pressure values ​​from cardiovascular-related features, which are related to the state of the circulatory system and change in accordance with the heartbeat, based on the correspondence between said cardiovascular-related features and said blood pressure values, A step of detecting a Korotkoff sound generated in accordance with the pulsation; A step of measuring a reference blood pressure value using the Korotkoff sound; A step of obtaining the cardiovascular-related feature amount corresponding to a specific beat corresponding to the Korotkoff sound in which the reference blood pressure value in the pulsation is measured; A step of determining the correspondence between the reference blood pressure value and the obtained cardiovascular-related feature amount; A calibration method for a blood pressure estimation device, characterized by including the above.

[0019] According to this, when calibrating the correspondence used in a blood pressure estimation device that calculates a blood pressure value from a cardiovascular-related feature amount based on the correspondence between the cardiovascular-related feature amount and the blood pressure value, the reference blood pressure value referred to is measured using the Korotkoff sound generated in accordance with the pulsation of the heart, and the cardiovascular feature amount corresponding to a specific beat corresponding to the Korotkoff sound in which the reference blood pressure value is measured is calculated. In this way Since the correspondence between the reference blood pressure value and the calculated cardiovascular-related feature amount is determined, it is possible to provide a calibration method capable of realizing highly accurate blood pressure estimation from the cardiovascular-related feature amount.

Effect of the Invention

[0020] According to the present invention, highly accurate blood pressure estimation based on a cardiovascular-related feature amount becomes possible.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a functional block diagram of a blood pressure estimation device according to Example 1. [Figure 2] FIG. 2 is a flowchart for explaining the procedure of the calibration process according to Example 1. [Figure 3] FIG. 3 is a diagram for explaining the calibration process according to Example 1. [Figure 4] FIG. 4 is a diagram for explaining an example of the correspondence used in the calibration process according to Example 1. <000011..​​​ [Figure 6] Figure 6 is a diagram illustrating the calibration process according to Example 2. [Figure 7] Figure 7 illustrates an example of a correspondence relationship used in the calibration process according to Example 2. [Figure 8] Figure 8 is a functional block diagram of the blood pressure estimation device according to Example 3. [Figure 9] Figure 9 shows the external configuration of the blood pressure estimation device according to Example 3. [Modes for carrying out 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 is described below. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment are not intended to limit the scope of the present invention to those specifications only.

[0024] (Configuration of blood pressure estimation device) Figure 1 is a functional block diagram of the blood pressure estimation device 1 according to Example 1. The blood pressure estimation device 1 measures PTT (Pulse Transit Time) as a cardiovascular-related feature (hereinafter referred to as "cardiovascular-related feature") in order 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 comprises 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 PTT and calculates blood pressure from the acquired PTT, and the reference blood pressure measurement unit 200 is a functional unit that accurately measures blood pressure to be referenced when calibrating the correspondence between PTT and blood pressure, as 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 quantity calculation unit 103, a memory unit 104, a relationship determination unit 105, and an estimated blood pressure acquisition unit 106. The feature calculation unit 103, the memory unit 104, the relationship determination unit 105, and the estimated blood pressure acquisition unit 106 are actually composed of a processor such as a CPU and memory used as a workspace for the processor and a storage area for programs and data executed by the processor, and each of the above-mentioned functional units is realized when a predetermined program is executed by the processor.

[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 rate caused by the beating of the heart. Here, pulse waves include pressure pulse waves, which are waveforms of changes in the internal pressure of the artery, and volume pulse waves, which are waveforms of changes in the volume of the artery. Pulse wave sensors that detect pressure pulse waves include tonometry methods and piezoelectric methods using piezoelectric sensors. Yes, there are. Pulse wave sensors that detect volume pulse waves include impedance methods that detect changes in impedance, photoelectric methods that use light-emitting and light-receiving elements to detect volume changes by reflected or transmitted light, and radio wave irradiation methods that use a transmitting element that transmits radio waves and a receiving element that receives reflected waves to detect volume changes as a phase difference between transmitted and reflected waves. The location on the subject where the first pulse wave sensor 101 and the second pulse wave sensor 102 are to be placed can be set as appropriate, but the first pulse wave sensor 101 is placed closer to the heart and the second pulse wave sensor 102 is placed further away from the heart, that is, the first pulse wave sensor 101 is placed upstream of the artery and the second pulse wave sensor 102 is placed downstream thereof, so that the arrival times of the pulse waves for the same heartbeat are different. Here, the first pulse wave sensor 101 and the second pulse wave sensor 102 correspond to the first pulse wave detection unit and the 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 and second pulse wave sensors (referred to as the first and second pulse waves, 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 memory unit 104 stores the first and second pulse waves, associating them with the time when each pulse wave was detected. The memory 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, which will be described later.

[0030] As will be described later, the relationship determination unit 105 determines the correspondence between PTT and SBP based on the systolic blood pressure (SBP) measured by the reference blood pressure measurement unit 200. The relationship is determined (the PTT corresponding to SBP is referred to as PTTsbp). Here, the relationship determination unit 105 corresponds to the relationship determination 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 memory unit 104. Here, the estimated blood pressure acquisition unit 106 corresponds to the calibrated blood pressure acquisition unit of the present invention. The blood pressure estimation unit 100 corresponds to the blood pressure estimation unit of the present invention.

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

[0033] The reference blood pressure measurement unit 200 measures blood pressure using the auscultation method. The auscultation method involves detecting the Korotkoff sounds produced when blood flow resumes after the cuff 201 has been depressurized from a state where blood flow has stopped due to pressurization by the cuff 201, using the microphone 202. Blood pressure is then measured based on these Korotkoff sounds. By identifying the beat in which the Korotkoff sounds occurred, it is possible to determine at which time a beat corresponding to SBP existed, thus enabling accurate measurement of blood pressure values ​​at each time point, even for very short-term blood pressure fluctuations such as respiratory variability. The cuff 201 should be placed on an appropriate part of the subject, such as the wrist or upper arm. It can be determined.

[0034] The cuff 201 is a bag-shaped component capable of storing air inside. The cuff 201 is pressurized by pumping air into it from the pump 205 with the valve closed, and the cuff 201 is depressurized by opening the valve from the pressurized state to release the air inside the cuff 201. Inside the cuff 201 are a microphone 202 for detecting Korotkoff sounds and a pressure sensor 203 for detecting the pressure inside the cuff 201.

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

[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 appropriate wired or wireless communication means. For example, the blood pressure estimation device 1 can be configured as a belt-shaped device worn on the upper arm and a wristwatch-type device worn on the wrist as the blood pressure estimation unit 100.

[0037] (Calibration Procedure) Figure 2 is a flowchart illustrating the procedure for calibrating the blood pressure estimation device 1 according to Example 1. Figure 3 shows the relationship between Korotkoff sounds, cuff pressure, and the first and second pulse waves. In Figure 3, the time progression on the horizontal axis is the same for Korotkoff sounds and cuff pressure, but the time progression of these sounds is not necessarily the same as the time progression of the first and second pulse waves on the horizontal axis, indicating a relative time relationship. The calibration process shown in Figure 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 represented by a linear function, as shown in Figure 4. The correspondence is determined by finding pairs of PTT and SBP values ​​for two points and fitting a straight line L1 connecting these two points.

[0038] First, the systolic blood pressure determination unit 206 determines the SBP by auscultation (step S1). More specifically, it operates the pump 205 to pressurize 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. By pressurizing the cuff 201 to this predetermined pressure, blood flow stops. From this state where blood flow has stopped, the cuff 201 is gradually depressurized. As the cuff pressure decreases and blood flow resumes, Korotkoff sounds begin to occur, and the first Korotkoff sound after the resumption of blood flow is detected by a microphone (shown as K1 in Figure 3). Since the cuff pressure Cp1 at the time the Korotkoff sound K1 is detected is the SBP, the SBP is determined based on the time the Korotkoff sound K1 is detected, as shown by the dashed arrow A11 in Figure 3. This SBP corresponds to the reference blood pressure value of the present invention.

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

[0040] Next, the relationship determination unit 105 acquires the pulse wave interval PTTsbp of the first and second pulse waves for the beat determined in step S2, that is, the time interval between Pw11 of the first pulse wave and Pw12 of the second pulse wave (step S3). The pulse wave interval acquired in this way corresponds to SBP and is therefore denoted as PTTsbp. Here, PTTsbp corresponds to the acquired value of the cardiovascular-related feature quantity of the present invention.

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

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

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

[0044] The calibration of the correspondence between PTT and SBP as described above may be performed, for example, every 30 minutes to 1 hour, but the timing of calibration is not limited to this. Calibration of the correspondence between PTT and SBP may also be performed according to the user's instructions.

[0045] <Example 2> The blood pressure estimation device 2 according to Embodiment 2 of the present invention will be described below. Components common to Embodiment 1 will be referred to using the same reference numerals, and detailed explanations will be omitted.

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

[0047] (Calibration Procedure) Figure 5 shows a flowchart illustrating the procedure for calibrating the blood pressure estimation device 2 according to Example 2. Figure 6 shows the relationship between Korotkoff sounds, cuff pressure, and the first and second pulse waves. In Figure 6, the time progression on the horizontal axis is the same for Korotkoff sounds and cuff pressure, but the time progression of these sounds is not necessarily the same as the time progression of the first and second pulse waves on the horizontal axis, indicating a relative time relationship. The calibration process shown in Figure 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 represented by a linear function, as shown in Figure 7. The correspondence is determined by finding pairs of PTT and DBP values ​​for two points and fitting a straight line L2 connecting these two points.

[0048] First, the diastolic blood pressure determination unit 207 determines the DBP by auscultation (step S11). More specifically, the cuff pressure is gradually reduced from a predetermined pressure. This predetermined pressure can be set as appropriate, For example, the cuff pressure can be set to a value that is a predetermined amount below the systolic blood pressure, at a pressure at which Korotkoff sounds are produced. In this way, by gradually reducing the cuff pressure from the predetermined pressure, the Korotkoff sounds detected by the microphone become quieter. Further reduction of the cuff pressure causes the Korotkoff sounds to disappear (shown as K2 in Figure 6). Since the cuff pressure Cp2 at which the Korotkoff sound K2 disappears is the DBP, the DBP is determined by the time the Korotkoff sound K2 disappears, as shown by the dashed arrow A21 in Figure 6. This DBP corresponds to the reference blood pressure value of the present invention.

[0049] Next, the relationship determination unit 105 determines the beat corresponding to DBP from the first and second pulse waves stored in the memory unit 104, as shown by the dashed arrow A22 in Figure 6 (step S12). Here, the beat corresponding to DBP is the beat closest to the time when the Korotkoff tone 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 obtained in this way corresponds to DBP and is therefore denoted as PTTdbp. Here, PTTdbp corresponds to the obtained value of the cardiovascular-related feature quantity of the present invention.

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

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

[0053] By storing the correspondence between the fitted SBP and PTTsbp (linear line L2) 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 PTT calculation values ​​continuously obtained by the feature calculation unit 103. Furthermore, by using auscultation to obtain DBP corresponding to a specific single beat as a reference for calibrating the correspondence between PTT and DBP, accurate references can be obtained at each time point even when there are blood pressure fluctuations such as respiratory variability, enabling calibration processing in a short time.

[0054] The calibration of the PTT and DBP correspondence described above may be performed, for example, every 30 minutes to 1 hour, but the timing of calibration is not limited to this. Calibration of the PTT and DBP correspondence may also be performed according to the user's instructions.

[0055] <Example 3> Figure 8 shows a functional block diagram of the blood pressure estimation device 3 according to Example 3. Components common to the blood pressure estimation device 1 according to Example 1 are referred to with the same reference numerals, and detailed explanations are omitted. The blood pressure estimation device 3 is configured by adding an electrocardiogram sensor 107 and a vibration sensor 108 to the blood pressure estimation device 1 according to Example 1. The blood pressure estimation device 3 shown in Figure 8 has an electrocardiogram sensor 107 and a vibration sensor 108. Although it includes a motion sensor 108, it is possible to have a configuration that includes at least one of the electrocardiogram sensor 107 and the vibration sensor 108. In this case, the first pulse wave sensor 101 (and the second pulse wave sensor 102), the electrocardiogram sensor 107, the vibration sensor 108, and the feature quantity calculation unit 103 correspond to the feature quantity acquisition unit of the present invention.

[0056] Figure 9 shows a specific configuration example of the blood pressure estimation device 3. This blood pressure estimation device 3 is belt-shaped and worn around the upper arm, with the blood pressure estimation unit 100 and the reference blood pressure measurement unit 200 integrated into one unit. The electrocardiogram sensor 107 is positioned on the subject-facing side along the shoulder-side edge of the blood pressure estimation device 3, which is worn along the upper arm, and the vibration sensor 108 is similarly positioned on the subject-facing side along the shoulder-side edge. The pulse wave sensor 101 (or second pulse wave sensor 102) is positioned on the subject-facing side along the elbow-side edge of the blood pressure estimation device 3. The cuff 201 is positioned along the belt, and the mechanical parts such as the pump 205, and the functional parts such as the systolic blood pressure determination unit 206 and the feature quantity calculation unit 103 are housed in the main body 301.

[0057] The electrocardiogram sensor 107 and the pulse wave sensor 101 can be used to measure PAT (Pulse Arrival Time). PAT is the 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] PAT can be calculated as the interval between the time of the R wave in the electrocardiogram caused by the heartbeat detected by the electrocardiogram sensor 107 and the time of the rising edge of the pulse wave, which is detected by the pulse wave sensor as a result of that heartbeat.

[0059] The vibration sensor 108 is a sensor that detects vibrations generated by the heartbeat, that is, vibrations transmitted from the heartbeat that occur on the body surface. As a heart sound sensor that detects sound waves, which are vibrations transmitted from the heartbeat that occur on the body surface, the vibration sensor 108 can be specifically configured as a microphone. Furthermore, as a cardiac dyscardiogram sensor that detects cardiac dyscardiograms, which are vibrations generated by the pulsation of such vibrations, the vibration sensor 108 can be specifically configured as an acceleration sensor, a piezoelectric sensor, or a strain gauge. The method of vibration detection is not limited to these. The vibration sensor 108 can measure PEP (Pulse-Ejection Period). PEP refers to the period of left ventricular contraction. This is the time from the start to the commencement of ejection into the aorta, and is also called the pre-ejection time. Furthermore, if a microphone is used as the vibration sensor 108, the microphone 202 can be replaced, so by providing the vibration sensor 108, the microphone 202 can be omitted. The vibration sensor 108 corresponds to the vibration detection unit of the present invention, and if a microphone is used as the vibration sensor 108, it corresponds to the sound wave detection unit of the present invention.

[0060] By providing an electrocardiogram sensor 107, a vibration sensor 108, and a first pulse wave sensor 101, PAT and PEP can be calculated as described above. At this time, since PAT-PEP=PTT, PTT can be calculated as a cardiovascular feature using the electrocardiogram sensor 107, vibration sensor 108, and first pulse wave sensor 101. When calculating SBP or DBP from the calculated PTT value, as a reference for calibrating the correspondence between PTT and SBP or DBP, the SBP or DBP corresponding to a specific single beat can be obtained using the auscultation method, similar to Example 1 or 2. This allows for accurate reference at each time point, even in the case of blood pressure fluctuations such as respiratory fluctuations, and enables calibration processing in a short time. Furthermore, since PTT can be measured without providing two pulse wave sensors, the number of pulse wave sensors can be reduced by one, resulting in power savings.

[0061] <Variation> In Examples 1, 2, and 3, PTT, PAT, and PEP were described as cardiovascular-related features, but cardiovascular-related features are not limited to these. For example, cardiovascular-related features In terms of quantity, PWV (Pulse Wave Velocity), AI (Augmentation Index), LVET (Left Ventricular Ejection Time), blood pressure, heart rate, and heart rate interval can also be applied. Here, PPWV is the pulse wave propagation velocity, AI is the pulse wave augmentation factor, and LVET is the left ventricular ejection time. [Explanation of Symbols]

[0062] 1, 2, 3... Blood pressure estimation device 100... Blood pressure estimation unit 200...Reference blood pressure measurement unit 101...First pulse wave sensor 102...Second pulse wave sensor 103...Feature Calculation Unit 105...Related Decision-Making Department 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 in accordance with heartbeat, and calculates a blood pressure value from the feature; a reference blood pressure measuring unit that includes an ultrasonic wave detecting unit that detects Korotkoff sounds generated in response to the pulsation and 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; 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 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:

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