Sphygmomanometer and blood pressure measuring method

Abstract

To provide a sphygmomanometer capable of determining irregular pulses accurately by obtaining a pulse wave signal with a large amplitude in a decompression process of blood pressure measurement.SOLUTION: A sphygmomanometer for pressuring a measured part of a user with a cuff and measuring blood pressure includes: a blood pressure measuring unit for measuring blood pressure of the user on the basis of a pulse wave signal in a decompression process for decompressing cuff pressure after a pressurizing process for pressurizing cuff pressure indicating internal pressure of the cuff to the pressure greater than specified pressure; a determination unit for determining whether or not irregular pulses are occurring in the user on the basis of the pulse wave signal in the decompression process; and a mode setting unit for setting either a first mode for executing irregular pulse determination or a second mode for not executing irregular pulse determination. The blood pressure measuring unit makes a first decompression speed of the cuff pressure when the first mode is set slower than a second decompression speed of the cuff pressure when the second mode is set.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a blood pressure monitor and a blood pressure measurement method. [Background technology]

[0002] Conventionally, a technique for detecting atrial fibrillation using a signal acquired during the process of measuring blood pressure is known. For example, a blood pressure monitor according to Patent Document 1 (JP Patent Publication 2020-192322 A) determines atrial fibrillation based on data on the interval time of a pulse signal in the pressurization stage measurement data and data on the interval time of a pulse signal in the depressurization stage measurement data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-192322 A Summary of the Invention [Problem to be solved by the invention]

[0004] As a method for determining arrhythmia using a blood pressure monitor based on the oscillometric method, a method for determining arrhythmia such as atrial fibrillation based on a pattern of pulse wave intervals acquired during the process of reducing cuff pressure is known. For example, the rising point or maximum point of the pulse wave signal for each beat is detected as a characteristic point, and the interval between the current beat and the previous beat is calculated as the pulse wave interval. In order to calculate the pulse wave interval accurately, it is better for the amplitude of the acquired pulse wave signal to be large. Therefore, in order to increase the accuracy of arrhythmia determination based on the pattern of the pulse wave interval, it is necessary to increase the amplitude of the pulse wave signal and acquire a more accurate pulse wave interval.

[0005] In one aspect, the present disclosure aims to provide a blood pressure monitor and a blood pressure measurement method that are capable of accurately determining arrhythmia by acquiring a large amplitude pulse wave signal during the depressurization process of blood pressure measurement. [Means for solving the problem]

[0006] In one example of the present disclosure, a blood pressure monitor is provided that measures blood pressure by compressing a measurement site of a user with a cuff. The blood pressure monitor includes a blood pressure measurement unit that measures the blood pressure of a user based on a pulse wave signal during a depressurization process in which the cuff pressure, which indicates the internal pressure of the cuff, is depressurized to a pressure greater than a specified pressure, after a pressurization process in which the cuff pressure is depressurized, a determination unit that determines whether the user has arrhythmia based on the pulse wave signal during the depressurization process, and a mode setting unit that sets either a first mode in which arrhythmia determination is performed or a second mode in which arrhythmia determination is not performed. The blood pressure measurement unit makes a first depressurization speed of the cuff pressure slower when the first mode is set than a second depressurization speed of the cuff pressure when the second mode is set.

[0007] According to the above configuration, by acquiring a pulse wave signal with a large amplitude during the depressurization process of blood pressure measurement, it is possible to accurately determine arrhythmia.

[0008] In another example of the present disclosure, the blood pressure measurement unit sets the first depressurization speed based on a pulse wave amplitude indicating the amplitude of a pulse wave signal during a pressurization process.

[0009] According to the above configuration, a more appropriate decompression speed can be set for the user.

[0010] In another example of the present disclosure, the blood pressure monitor further includes a memory unit that stores a pulse wave signal during a pressurization process or a depressurization process when the blood pressure measurement unit measures the user's blood pressure. The blood pressure measurement unit sets a first depressurization speed based on a pulse wave amplitude indicating the amplitude of a past pulse wave signal stored in the memory unit.

[0011] According to the above configuration, a more appropriate decompression speed can be set for the user.

[0012] In another example of the present disclosure, the blood pressure measurement unit sets the first depressurization speed to be slower as the pulse wave amplitude is smaller.

[0013] According to the above configuration, arrhythmia determination can be achieved with high accuracy in an appropriate measurement time.

[0014] In another example of the present disclosure, the blood pressure measurement unit sets the first depressurization speed to be slower as the time it takes for the cuff pressure to reach a predetermined pressure in the inflation process becomes longer.

[0015] According to the above configuration, arrhythmia determination can be achieved with high accuracy in an appropriate measurement time.

[0016] In another example of the present disclosure, the blood pressure measurement unit estimates the size of the cuff based on the time it takes for the cuff pressure to reach a predetermined pressure during the inflation process, and sets the first depressurization speed slower as the estimated cuff size increases.

[0017] According to the above configuration, arrhythmia determination can be achieved with high accuracy in an appropriate measurement time.

[0018] In another example of the present disclosure, the blood pressure monitor further includes a wrapping strength detection unit that detects the wrapping strength of the cuff around the measurement site based on the cuff pressure and the volume change of the cuff during the pressurization process. The blood pressure measurement unit sets the first depressurization speed to be slower as the wrapping strength is smaller.

[0019] According to the above configuration, arrhythmia determination can be achieved with high accuracy in an appropriate measurement time.

[0020] In another example of the present disclosure, the blood pressure measurement unit sets the second decompression speed based on an estimated pulse pressure, which is the difference between an estimated systolic blood pressure and an estimated diastolic blood pressure, and a predetermined pulse rate required when measuring the user's blood pressure.

[0021] According to the above configuration, it is possible to realize quick blood pressure measurement for a user who does not want arrhythmia determination.

[0022] In another example of the present disclosure, a blood pressure measurement method using a sphygmomanometer is provided that measures blood pressure by compressing a measurement site of a user with a cuff. The blood pressure measurement method includes the steps of measuring the user's blood pressure based on a pulse wave signal during a depressurization process in which the cuff pressure, which indicates the internal pressure of the cuff, is depressurized to a pressure greater than a specified pressure, after which the cuff pressure is depressurized, determining whether the user has arrhythmia based on the pulse wave signal during the depressurization process, and setting either a first mode in which arrhythmia determination is performed or a second mode in which arrhythmia determination is not performed. A first depressurization speed of the cuff pressure when the first mode is set is slower than a second depressurization speed of the cuff pressure when the second mode is set.

[0023] According to the above configuration, by acquiring a pulse wave signal with a large amplitude during the depressurization process of blood pressure measurement, it is possible to accurately determine arrhythmia. Effect of the Invention

[0024] According to the present disclosure, arrhythmia can be determined with high accuracy by acquiring a pulse wave signal with large amplitude during the decompression process of blood pressure measurement. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram showing a blood pressure monitor according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a block diagram illustrating an example of a hardware configuration of a sphygmomanometer according to a first embodiment. [Diagram 3] FIG. 2 is a block diagram showing a functional configuration of the sphygmomanometer according to the first embodiment. [Figure 4] FIG. 13 is a diagram showing the relationship between pulse wave amplitude and decompression rate during the pressurization process. [Diagram 5] FIG. 13 is a diagram showing the relationship between previously obtained pulse wave amplitude and decompression rate. [Figure 6] 5 is a flowchart showing an example of a processing procedure of the sphygmomanometer according to the first embodiment. [Figure 7]13 is a flowchart showing another example of the processing procedure of the sphygmomanometer according to the first embodiment. [Figure 8] 13 is a flowchart showing still another example of the processing procedure of the sphygmomanometer according to the first embodiment. [Figure 9] 10 is a diagram for explaining the relationship between the time required to reach a predetermined pressure and the decompression speed. FIG. [Figure 10] FIG. 13 is a diagram for explaining the relationship between the time required to reach a predetermined pressure, the decompression rate, and the cuff size. [Figure 11] 11 is a flowchart showing an example of a processing procedure of the sphygmomanometer according to the second embodiment. [Figure 12] 13 is a flowchart showing another example of the processing procedure of the sphygmomanometer according to the second embodiment. [Figure 13] FIG. 11 is a block diagram showing a functional configuration of a sphygmomanometer according to a third embodiment. [Figure 14] 13 is a flowchart showing an example of a processing procedure of the sphygmomanometer according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0027] [Example of application] An application example of the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing a blood pressure monitor 100 according to the present embodiment.

[0028] With reference to FIG. 1, blood pressure monitor 100 is an upper arm blood pressure monitor that measures blood pressure by applying pressure to a measurement site of a user (i.e., a subject) with a cuff. Blood pressure monitor 100 performs blood pressure measurement by an oscillometric method. Blood pressure monitor 100 has a main body and a cuff (arm band) as main components. Note that blood pressure monitor 100 may be a wrist-type blood pressure monitor in which the main body and the cuff (arm band) are integrated. Hereinafter, the processing contents will be described with reference to FIG. 1.

[0029] 1, it is assumed that a user measures his / her own blood pressure using a blood pressure monitor 100. The blood pressure monitor 100 measures the user's blood pressure by a decompression measurement method that measures blood pressure during the decompression process of cuff pressure, which indicates the internal pressure of a cuff attached to a measurement site (e.g., an arm) of the user.

[0030] The blood pressure monitor 100 starts inflating the cuff in response to a blood pressure measurement instruction from the user (corresponding to (1) in FIG. 1).

[0031] The blood pressure monitor 100 estimates the systolic blood pressure (maximum blood pressure) and the diastolic blood pressure (minimum blood pressure) based on the detected pulse wave signal during the process of increasing the cuff pressure (corresponding to (2) in FIG. 1). The estimation of the systolic blood pressure and the diastolic blood pressure is performed by a known method. For example, the blood pressure monitor 100 estimates the systolic blood pressure and the diastolic blood pressure from a pulse wave envelope that indicates the pattern of the change in amplitude of the pulse wave signal that changes during the process of increasing the cuff pressure. Hereinafter, the estimated systolic blood pressure is also referred to as the "estimated systolic blood pressure" and the estimated diastolic blood pressure is also referred to as the "estimated diastolic blood pressure".

[0032] The sphygmomanometer 100 selects either a normal measurement mode (hereinafter also simply referred to as "normal mode") or an arrhythmia determination mode (corresponding to (3) in FIG. 1). The arrhythmia determination mode is a mode in which arrhythmia determination is performed in addition to blood pressure measurement based on a pulse wave signal during the cuff pressure reduction process following the inflation process. The normal mode is a mode in which only blood pressure measurement is performed based on the pulse wave signal during the depressurization process, and arrhythmia determination is not performed. Here, it is assumed that the arrhythmia determination mode is selected.

[0033] The sphygmomanometer 100 sets the decompression rate of the cuff pressure during the decompression process in the arrhythmia determination mode (corresponding to (4) in FIG. 1). Here, in the normal mode, the decompression rate is set so that a predetermined pulse rate is obtained between the estimated pulse pressure, which is the difference between the estimated systolic blood pressure and the estimated diastolic blood pressure. The decompression rate in the arrhythmia determination mode is set slower than the decompression rate in the normal mode. It is known that a slower decompression rate increases the amplitude of the pulse wave signal obtained during the decompression process (hereinafter, "pulse wave amplitude"). Therefore, the pulse wave amplitude obtained during the decompression process in the arrhythmia determination mode is larger than the pulse wave amplitude obtained during the decompression process in the normal mode.

[0034] The sphygmomanometer 100 calculates the user's blood pressure value and determines whether or not arrhythmia has occurred based on the pulse wave signal obtained during the decompression process (corresponding to (5) in FIG. 1). In this case, the sphygmomanometer 100 displays the user's blood pressure value and the arrhythmia determination result on the display.

[0035] According to the above application example, the pulse wave amplitude obtained in the arrhythmia determination mode is larger than that obtained in the normal mode, so that a more accurate pulse wave interval pattern can be obtained in the arrhythmia determination mode, thereby enabling the blood pressure monitor 100 to perform arrhythmia determination with higher accuracy.

[0036] The sphygmomanometer 100 creates a pulse wave envelope based on the amplitude of the acquired pulse wave signal and the cuff pressure, and calculates the blood pressure based on the pulse wave envelope. The sphygmomanometer 100 performs processing such as correction and smoothing of the pulse wave envelope so that the blood pressure can be calculated even if the acquired pulse wave signal is too small to be recognized as a pulse wave. Therefore, in the normal mode in which the decompression speed is fast, the sphygmomanometer 100 can calculate the blood pressure in a short measurement time. Therefore, blood pressure measurement is performed quickly for users who do not want arrhythmia determination.

[0037] As described above, blood pressure monitor 100 according to the present embodiment can accurately determine arrhythmia by acquiring a pulse wave signal with large amplitude during the depressurization process of blood pressure measurement.

[0038] [Configuration example] <Embodiment 1> (Hardware configuration) Fig. 2 is a block diagram showing an example of a hardware configuration of the blood pressure monitor 100 according to the first embodiment. With reference to Fig. 2, the blood pressure monitor 100 includes, as main components, a main body 10 and a cuff 20. The cuff 20 contains a fluid bag 22. The main body 10 includes a processor 110, an air system component 30 for blood pressure measurement, an A / D conversion circuit 310, a pump drive circuit 320, a valve drive circuit 330, a display 50, a memory 51, an operation unit 52, a communication interface 53, and a power supply unit 54.

[0039] The processor 110 is an arithmetic processing unit such as a CPU (Central Processing Unit) or an MPU (Multi Processing Unit). The processor 110 realizes each of the processes (steps) of the sphygmomanometer 100 described later by reading and executing a program stored in the memory 51. For example, the processor 110 controls the driving of the pump 32 and the valve 33 in response to an operation signal from the operation unit 52. The processor 110 also calculates a blood pressure value using an algorithm for calculating blood pressure by the oscillometric method, and displays the calculated blood pressure value on the display 50.

[0040] The memory 51 is realized by a RAM (Random Access Memory), a ROM (Read-Only Memory), a flash memory, etc. The memory 51 stores a program for controlling the sphygmomanometer 100, data used for controlling the sphygmomanometer 100, setting data for setting various functions of the sphygmomanometer 100, and data of blood pressure measurement results, pulse rate, pulse wave interval, etc. The memory 51 is also used as a work memory, etc. when the program is executed.

[0041] The air system component 30 supplies or exhausts air through air piping to the fluid bag 22 contained in the cuff 20. The air system component 30 includes a pressure sensor 31 for detecting the pressure inside the fluid bag 22, and a pump 32 and a valve 33 as an inflation / deflation mechanism for inflating and deflating the fluid bag 22.

[0042] The pressure sensor 31 detects the pressure (cuff pressure) in the fluid bag 22 and outputs a signal (cuff pressure signal) corresponding to the detected pressure to the A / D conversion circuit 310. The pressure sensor 31 is, for example, a piezo-resistance type pressure sensor, and is connected to the pump 32, the valve 33, and the fluid bag 22 contained in the cuff 20 via an air pipe. The pump 32 supplies air as a fluid to the fluid bag 22 through the air pipe to increase the cuff pressure. The valve 33 is opened and closed to control the cuff pressure by discharging air from the fluid bag 22 through the air pipe or by sealing air in the fluid bag 22.

[0043] The A / D conversion circuit 310 converts the output value of the pressure sensor 31 (for example, a voltage value corresponding to a change in electrical resistance due to the piezoresistance effect) from an analog signal to a digital signal and outputs it to the processor 110. The processor 110 acquires a signal representing the cuff pressure according to the output value of the A / D conversion circuit 310. The pump drive circuit 320 controls the drive of the pump 32 based on a control signal provided by the processor 110. The valve drive circuit 330 controls the opening and closing of the valve 33 based on a control signal provided by the processor 110.

[0044] When blood pressure is measured according to the oscillometric method, the following operations are generally performed. Specifically, a cuff is wrapped around the subject's measurement site (wrist, arm, etc.) in advance, and during measurement, the pump 32 and valve 33 are controlled to increase the cuff pressure higher than the estimated systolic blood pressure, and then the pressure is gradually reduced. During this reduction process, the cuff pressure is detected by a pressure sensor, and the change in arterial volume occurring in the artery at the measurement site is extracted as a pulse wave signal. The systolic blood pressure and diastolic blood pressure are calculated based on the change in amplitude of the pulse wave signal (mainly the rise and fall) accompanying the change in cuff pressure at that time.

[0045] The operation unit 52 inputs an operation signal corresponding to an instruction from a user to the processor. The operation unit 52 includes a measurement switch 52A for receiving a blood pressure measurement instruction from the user, and a mode selection switch 52B for selecting a measurement mode.

[0046] When the measurement switch 52A is pressed, the measurement site is temporarily compressed by the cuff 20, and blood pressure measurement is performed by the oscillometric method. When the measurement switch 52A is pressed again during blood pressure measurement, the blood pressure measurement is stopped.

[0047] When the mode selection switch 52B is pressed, the measurement mode is switched. For example, when the mode selection switch 52B is pressed while the current measurement mode is set to the normal mode, the measurement mode is switched to the arrhythmia determination mode.

[0048] The display 50 displays various information including blood pressure measurement results based on a control signal from the processor 110. The communication interface 53 exchanges various information with an external device. The power supply unit 54 supplies power to the processor 110 and each piece of hardware.

[0049] (Functional configuration) FIG. 3 is a block diagram showing a functional configuration of blood pressure monitor 100 according to the first embodiment. Referring to FIG. 3, blood pressure monitor 100 includes, as main functional components, a mode setting unit 210, a blood pressure measurement unit 220, a determination unit 230, and an output control unit 240. These functions are realized, for example, by processor 110 of blood pressure monitor 100 executing a program stored in memory 51. Note that some or all of these functions may be configured to be realized by hardware. Blood pressure monitor 100 further includes a storage unit 250. The storage unit 250 is realized by memory 51.

[0050] The mode setting unit 210 sets either an arrhythmia determination mode in which the presence or absence of arrhythmia of the user is determined, or a normal mode in which arrhythmia determination is not performed. Typically, the mode setting unit 210 sets either the arrhythmia determination mode or the normal mode in accordance with a mode selection instruction from the user via the operation unit 52 (e.g., the mode selection switch 52B).

[0051] The mode setting unit 210 may be configured to automatically set one of the modes according to a predetermined schedule. For example, when blood pressure measurement is started in time zone H of a day (for example, blood pressure measurement is started by pressing the measurement switch 52A), the arrhythmia determination mode is automatically set. On the other hand, when blood pressure measurement is performed in a time zone other than time zone H of a day, the normal mode is automatically set.

[0052] The blood pressure measurement unit 220 controls the cuff pressure according to a measurement start instruction from the user via the operation unit 52 (e.g., measurement switch 52A). Specifically, the blood pressure measurement unit 220 drives the pump 32 via the pump drive circuit 320, and controls the drive of the valve 33 via the valve drive circuit 330. The valve 33 is opened and closed to discharge or seal air in the fluid bag 22 to control the cuff pressure.

[0053] The blood pressure measurement unit 220 receives the cuff pressure signal detected by the pressure sensor 31 and extracts a pulse wave signal representing the pulse wave at the measurement site superimposed on the cuff pressure signal. That is, the blood pressure measurement unit 220 detects, from the cuff pressure signal, a pulse wave, which is a pressure component that is superimposed on the cuff pressure signal in synchronization with the beating of the user's heart.

[0054] The blood pressure measurement unit 220 calculates blood pressure information of the user based on the cuff pressure signal and the pulse wave signal superimposed on the cuff pressure signal. Specifically, the blood pressure measurement unit 220 measures the user's blood pressure according to an oscillometric method. In this embodiment, a decompression measurement method is adopted in which the cuff pressure is increased to a pressure greater than a specified pressure (e.g., an estimated systolic blood pressure) and then the user's blood pressure is measured based on the pulse wave signal in a decompression process in which the cuff pressure is reduced. Typically, the blood pressure measurement unit 220 calculates the systolic blood pressure, the diastolic blood pressure, the pulse rate, and the pulse pressure. The storage unit 250 stores information obtained during blood pressure measurement (e.g., the pulse wave signal, the systolic blood pressure, the diastolic blood pressure, the pulse rate, the pulse pressure, etc.).

[0055] The blood pressure measurement unit 220 sets a depressurization speed of the cuff pressure in the depressurization process based on the measurement mode set by the mode setting unit 210. Specifically, the blood pressure measurement unit 220 sets a depressurization speed G1 of the cuff pressure when the arrhythmia determination mode is set to be slower than a depressurization speed G2 of the cuff pressure when the normal mode is set.

[0056] Typically, the blood pressure measurement unit 220 determines an estimated systolic blood pressure and an estimated diastolic blood pressure based on the pulse wave signal during the pressurization process, and sets the depressurization speed G2 based on an estimated pulse pressure, which is the difference between the estimated systolic blood pressure and the estimated diastolic blood pressure, and a predetermined pulse rate (e.g., 8 beats) required for measuring the user's blood pressure. For example, the sphygmomanometer 100 sets the depressurization speed G2 so that the pulse rate occurring between the estimated pulse pressures is equal to or greater than the predetermined pulse rate.

[0057] There are several possible methods for setting the decompression speed G1 by the blood pressure measurement unit 220. In one aspect, the blood pressure measurement unit 220 sets the decompression speed G1 to a predetermined speed (e.g., 4 mmHg / s). This speed (e.g., 4 mmHg / s) is sufficiently slower than the decompression speed G2 calculated by the above method.

[0058] In another aspect, the blood pressure measurement unit 220 sets the depressurization speed G1 based on the pulse wave amplitude during the pressurization process. The blood pressure measurement unit 220 sets the depressurization speed G1 to be slower as the pulse wave amplitude is smaller.

[0059] Fig. 4 is a diagram showing the relationship between the pulse wave amplitude and the decompression speed during the pressurization process. The vertical axis of the graph in Fig. 4 indicates the decompression speed G1, and the horizontal axis indicates the maximum pulse wave amplitude obtained during the pressurization process. It can be seen that the smaller the maximum pulse wave amplitude during the pressurization process, the slower the decompression speed G1. This is because a pulse wave amplitude having a certain magnitude or more during the decompression process can be obtained to perform arrhythmia determination with high accuracy.

[0060] Specifically, there is a positive correlation between a large pulse wave amplitude in the pressurization process and a large pulse wave amplitude in the depressurization process. Therefore, when the pulse wave amplitude in the pressurization process is small, the depressurization speed is slowed down so that the pulse wave amplitude obtained in the depressurization process is large. On the other hand, when the pulse wave amplitude in the pressurization process is sufficiently large, it is considered that a large pulse wave amplitude can also be obtained in the depressurization process, so the depressurization speed is increased. In this case, the measurement time is shortened. In this way, the depressurization speed G1 is set to a depressurization speed required to obtain a pulse wave amplitude of a certain magnitude or more. This allows a more appropriate depressurization speed to be set for the user, and allows for highly accurate arrhythmia determination to be achieved in an appropriate measurement time.

[0061] Referring again to FIG. 3, blood pressure measurement unit 220 sets decompression speed G1 based on the amplitude of the past pulse wave signal stored in storage unit 250 (ie, the pulse wave amplitude).

[0062] Fig. 5 is a diagram showing the relationship between the pulse wave amplitude and the decompression speed obtained in the past. The vertical axis of the graph in Fig. 5 indicates the decompression speed G1, and the horizontal axis indicates the pulse wave amplitude obtained during the pressurization process or decompression process during the user's previous blood pressure measurement (hereinafter, for convenience, also referred to as "pulse wave amplitude Am"). It can be seen that the smaller the pulse wave amplitude Am, the slower the decompression speed G1. This is because a pulse wave amplitude having a certain magnitude or more can be obtained during the decompression process to perform arrhythmia determination with high accuracy.

[0063] Specifically, if the pulse wave amplitude Am obtained in the past is small, it is estimated that the pulse wave amplitude in the decompression process during the current blood pressure measurement is also small. Therefore, if the pulse wave amplitude Am obtained in the past is small, the decompression speed is slowed down so that the pulse wave amplitude obtained in the current decompression process is large. On the other hand, if the pulse wave amplitude Am obtained in the past is sufficiently large, it is considered that a large pulse wave amplitude will also be obtained in the current decompression process, so the decompression speed is increased. In this case, the measurement time is shortened. In this way, as in the case of FIG. 4, the decompression speed G1 is set to a decompression speed required to obtain a pulse wave amplitude of a certain magnitude or more. Even in this case, a more appropriate decompression speed can be set for the user, and highly accurate arrhythmia determination can be achieved with an appropriate measurement time.

[0064] The memory unit 250 stores pulse wave amplitudes during a predetermined period in the past. For example, the memory unit 250 stores pulse wave signals during the pressurization process or the depressurization process when the user's blood pressure is measured. As an example, the blood pressure measurement unit 220 calculates the average value of the maximum pulse wave amplitudes during the pressurization process during the most recent multiple (e.g., three) blood pressure measurements based on the data stored in the memory unit 250, and sets the average value as the pulse wave amplitude Am. As another example, the blood pressure measurement unit 220 extracts data from past blood pressure measurements in the same time period (e.g., morning, afternoon, night, etc.) as the current blood pressure measurement, and sets the maximum pulse wave amplitude during the pressurization process during the current blood pressure measurement as the pulse wave amplitude Am. As yet another example, the blood pressure measurement unit 220 sets the maximum pulse wave amplitude during the pressurization process during multiple blood pressure measurements within a predetermined period (e.g., one day) as the pulse wave amplitude Am.

[0065] 3 again, when the arrhythmia determination mode is set, the determination unit 230 determines whether or not the user has experienced arrhythmia based on the pulse wave signal during the decompression process. A known method is used to determine arrhythmia. For example, the determination unit 230 determines whether or not arrhythmia has occurred based on the occurrence interval of a plurality of pulse waves (i.e., the pulse wave interval) acquired from the pulse wave signal.

[0066] The output control unit 240 displays the measurement results of the blood pressure measurement unit 220 and the determination results of the determination unit 230 on the display 50. The output control unit 240 may transmit the measurement results and the determination results to an external device via the communication interface 53, or may be configured to output the results as audio via a speaker (not shown).

[0067] (Processing Procedure) Fig. 6 is a flowchart showing an example of a processing procedure of blood pressure monitor 100 according to the embodiment 1. At the start of the processing, it is assumed that the user is wearing cuff 20 of blood pressure monitor 100. In Fig. 6, it is assumed that the normal mode or the arrhythmia determination mode is set as the measurement mode.

[0068] 6, the processor 110 of the sphygmomanometer 100 receives an instruction to start blood pressure measurement from the user via the measurement switch 52A of the operation unit 52 (step S10). The processor 110 initializes the pressure sensor 31 (step S12). Specifically, the processor 110 initializes the processing memory area, turns off (stops) the pump 32, and adjusts the pressure sensor 31 to 0 mmHg (sets the atmospheric pressure to 0 mmHg) with the valve 33 open.

[0069] The processor 110 closes the valve 33 via the valve drive circuit 330 (step S14), and turns on (starts) the pump 32 via the pump drive circuit 320 to start pressurizing the cuff 20 (fluid bag 22) (step S16). Typically, the processor 110 drives the pump 32 by controlling the pump drive circuit 320 for pressurization so that the cuff pressure inflation speed is constant.

[0070] Processor 110 extracts a pulse wave signal from the cuff pressure signal detected by pressure sensor 31, and calculates an estimated systolic blood pressure, an estimated diastolic blood pressure, and a pulse rate based on the pulse wave signal obtained during the pressurization process (step S18). Processor 110 determines whether or not the cuff pressure has reached a threshold value Th or higher (step S20). Typically, threshold value Th is set to a value that is a fixed value (e.g., 40 mmHg) higher than the estimated systolic blood pressure.

[0071] If the cuff pressure is less than the threshold Th (NO in step S20), the processor 110 returns to step S16. If the cuff pressure is equal to or greater than the threshold Th (YES in step S20), the processor 110 stops the pump 32 (step S22) and determines whether the currently set measurement mode is the normal mode (step S24).

[0072] First, a case where the measurement mode is the normal mode (YES in step S24) will be described. The processor 110 calculates a decompression speed G2 based on the estimated pulse pressure, which is the difference between the estimated systolic blood pressure and the estimated diastolic blood pressure, and the pulse rate (step S26). The processor 110 controls the valve 33 to gradually open in accordance with the decompression speed G2 (step S28). This causes a transition from the pressurization process to the decompression process, and the cuff pressure is gradually decompressed in accordance with the decompression speed G2.

[0073] During this decompression process, processor 110 extracts a pulse wave signal from the cuff pressure signal detected by pressure sensor 31, and attempts to calculate systolic and diastolic blood pressures based on the pulse wave signal to determine whether blood pressure calculation has been completed (step S30). If blood pressure calculation cannot be completed yet due to insufficient data (NO in step S30), processor 110 returns to step S28. If blood pressure calculation has been completed (YES in step S30), processor 110 fully opens valve 33 (step S32) to perform control to rapidly exhaust air from within cuff 20. Processor 110 displays the blood pressure value (measurement result) measured in step S30 on display 50 (step S34).

[0074] Next, a case where the measurement mode is the arrhythmia determination mode (NO in step S24) will be described. The processor 110 sets the decompression speed G1 to a predetermined speed (e.g., 4 mmHg / s) (step S40). The predetermined speed is assumed to be sufficiently slower than the decompression speed G2. The processor 110 controls the valve 33 to gradually open in accordance with the decompression speed G1 (step S42). This causes a transition from the inflation process to the decompression process, and the cuff pressure is gradually decompressed in accordance with the decompression speed G1.

[0075] During the decompression process, processor 110 extracts a pulse wave signal from the cuff pressure signal, attempts to calculate systolic blood pressure and diastolic blood pressure based on the pulse wave signal, and determines whether blood pressure calculation is complete (step S44). If blood pressure calculation cannot be completed (NO in step S44), processor 110 returns to step S42. If blood pressure calculation is completed (YES in step S44), processor 110 executes arrhythmia determination processing (step S46). Specifically, processor 110 determines whether arrhythmia has occurred based on the pulse wave interval obtained from the pulse wave signal during the decompression process.

[0076] Subsequently, the processor 110 executes the above-mentioned steps S32 and S34. In step S34, the blood pressure measurement result and the arrhythmia determination result are displayed as the measurement results.

[0077] Fig. 7 is a flowchart showing another example of the processing procedure of sphygmomanometer 100 according to embodiment 1. The flowchart in Fig. 7 corresponds to the flowchart in Fig. 6 in which step S40 is replaced with step S50. Therefore, detailed description of the processing other than step S50 will not be repeated.

[0078] 7, in step S50, processor 110 calculates depressurization speed G1 based on the amplitude of the pulse wave signal (i.e., the pulse wave amplitude) during the pressurization process. For example, processor 110 calculates depressurization speed G1 according to the graph of FIG.

[0079] Fig. 8 is a flowchart showing still another example of the processing procedure of sphygmomanometer 100 according to embodiment 1. The flowchart in Fig. 8 corresponds to the flowchart in Fig. 6 in which step S40 is replaced with step S60. Therefore, detailed description of the processing other than step S60 will not be repeated.

[0080] 8, in step S60, processor 110 calculates decompression speed G1 based on the pulse wave amplitude obtained in the past. For example, processor 110 calculates decompression speed G1 according to the graph in FIG.

[0081] <Embodiment 2> In the second embodiment, a method of setting the decompression speed G1 with attention focused on the size of the cuff (for example, the volume of the fluid bag) will be described.

[0082] In order to accurately measure blood pressure, it is necessary to appropriately compress and occlude the artery at the measurement site by the cuff pressure. Therefore, the size of the cuff is determined according to the circumferential length of the measurement site, and the longer the circumferential length of the measurement site, the larger the cuff size. When the cuff size is larger, the volume of the fluid bag increases, and the ratio of the volume change of the fluid bag to the volume change of the artery decreases. As a result, the change in the cuff pressure, i.e., the amplitude of the pulse wave signal (i.e., the pulse wave amplitude), decreases. Hereinafter, a method for setting the decompression speed G1 according to the second embodiment will be described.

[0083] (Functional configuration) The functional configuration of the sphygmomanometer 100 according to the second embodiment will be described with reference to the block diagram of Fig. 3. The blood pressure measurement unit 220 according to the second embodiment further has the following functions in addition to the functions described in Fig. 3.

[0084] During the pressurization process, the blood pressure measurement unit 220 pressurizes the cuff by driving the pump 32 so as to achieve a constant discharge flow rate per unit time. Based on the cuff pressure signal detected by the pressure sensor 31, the blood pressure measurement unit 220 measures the arrival time T for the cuff pressure to reach a predetermined pressure during the pressurization process. The arrival time T varies depending on the capacity (size) of the cuff. For example, the blood pressure measurement unit 220 measures the arrival time T for the cuff pressure to reach "30 mmHg" from "0 mmHg". The blood pressure measurement unit 220 sets the depressurization speed G1 to be slower as the arrival time T is longer.

[0085] Fig. 9 is a diagram for explaining the relationship between the time to reach a predetermined pressure and the decompression speed. The vertical axis of the graph in Fig. 9 represents the decompression speed G1, and the horizontal axis represents the time T required for the cuff pressure to reach "30 mmHg" from "0 mmHg."

[0086] 9, it can be seen that the decompression speed G1 becomes slower as the arrival time T becomes longer. This is because an arrhythmia can be determined with high accuracy by obtaining a pulse wave amplitude having a certain magnitude or more during the decompression process.

[0087] Specifically, the cuff pressure is increased by driving the pump 32 to achieve a constant discharge flow rate per unit time, so that a longer arrival time T means a larger cuff volume (i.e., cuff size). As described above, the larger the cuff size, the smaller the pulse wave amplitude. Therefore, by setting the decompression speed G1 slower as the arrival time T is longer (i.e., as the cuff size is larger), the pulse wave amplitude obtained during the decompression process can be increased. This allows for highly accurate arrhythmia determination.

[0088] The blood pressure measurement unit 220 may be configured to estimate the size of the cuff based on the arrival time T. Fig. 10 is a diagram for explaining the relationship between the arrival time to reach a predetermined pressure, the decompression speed, and the cuff size. The vertical axis of the graph in Fig. 10 is the decompression speed G1, and the horizontal axis is the arrival time T.

[0089] The blood pressure measurement unit 220 estimates the cuff size to be "Small" when the arrival time T is less than 3 seconds, estimates the cuff size to be "Medium" when the arrival time T is 3 seconds or more and less than 6 seconds, and estimates the cuff size to be "Large" when the arrival time T is 6 seconds or more. That is, the blood pressure measurement unit 220 estimates that the cuff size is larger as the arrival time T is longer.

[0090] Then, the blood pressure measurement unit 220 sets the decompression speed G1 to 6 mmHg / s when the cuff size is estimated to be "Small", sets the decompression speed G1 to 5.5 mmHg / s when the cuff size is estimated to be "Medium", and sets the decompression speed G1 to 4 mmHg / s when the cuff size is estimated to be "Large". In other words, the blood pressure measurement unit 220 sets the decompression speed G1 to a slower value as the cuff size increases.

[0091] (Processing Procedure) Fig. 11 is a flowchart showing an example of a processing procedure of sphygmomanometer 100 according to the second embodiment. The flowchart in Fig. 11 corresponds to the flowchart in Fig. 6 in which step S40 is replaced with step S70. Therefore, detailed description of the processes other than step S70 will not be repeated. However, in step S16, processor 110 drives pump 32 to achieve a constant discharge flow rate per unit time by controlling pump drive circuit 320 for pressurization.

[0092] 11, in step S70, processor 110 calculates decompression speed G1 based on the time T required for the cuff pressure to reach a predetermined pressure in the inflation process. For example, processor 110 calculates decompression speed G1 according to the graph in FIG.

[0093] Fig. 12 is a flowchart showing another example of the processing procedure of sphygmomanometer 100 according to the second embodiment. The flowchart in Fig. 12 corresponds to the flowchart in Fig. 6 in which step S40 is replaced with steps S80 and S82. Therefore, detailed description of the processes other than steps S80 and S82 will not be repeated. However, in step S16, processor 110 drives pump 32 to achieve a constant discharge flow rate per unit time by controlling pump drive circuit 320 for pressurization.

[0094] 12, processor 110 estimates the cuff size based on arrival time T (step S80), and calculates decompression speed G1 based on the estimated cuff size (step S82). Specifically, processor 110 estimates the cuff size and calculates decompression speed G1 according to the graph in FIG.

[0095] <Embodiment 3> In the third embodiment, a method for setting the decompression speed G1 with attention focused on the tightness of the cuff will be described.

[0096] When the cuff is wrapped loosely, the fluid bag needs to expand more until the gap between the living body and the cuff is filled. Therefore, when the cuff is wrapped loosely, the volume of the fluid bag becomes larger than when the cuff is wrapped tightly, and as a result, the amplitude of the obtained pulse wave signal becomes smaller. The method of setting the decompression speed G1 according to the third embodiment will be described below.

[0097] (Functional configuration) Fig. 13 is a block diagram showing a functional configuration of a sphygmomanometer 100 according to the third embodiment. With reference to Fig. 13, the sphygmomanometer 100 includes a mode setting unit 210, a blood pressure measurement unit 220, a determination unit 230, an output control unit 240, and a wrapping strength detection unit 260. These functions are realized, for example, by the processor 110 of the sphygmomanometer 100 executing a program stored in the memory 51. The functions of the mode setting unit 210, the determination unit 230, and the output control unit 240 are similar to the corresponding functions described in Fig. 3.

[0098] The wrapping strength detection unit 260 detects the wrapping strength of the cuff 20 around the measurement site based on the cuff pressure during the pressurization process and the volume change of the cuff 20. The wrapping strength detection method is realized by a known method. Typically, the wrapping strength detection unit 260 has the same function as the wrapping strength detection unit shown in Japanese Patent No. 5408142.

[0099] As an example, during the pressurization process in which the pump 32 is driven to achieve a constant discharge flow rate to pressurize the cuff, the wrapping strength detection unit 260 compares the value of the volume change of the cuff 20 detected as the cuff pressure changes from pressure P1 to pressure P2 with the value of the volume change of the cuff 20 detected as the cuff pressure changes from pressure P2 to pressure P3 based on the pressure-volume change relationship indicated by the volume change of the cuff 20 detected as the cuff pressure changes from pressure P1 to pressure P2 and the volume change of the cuff 20 detected as the cuff pressure changes from pressure P2 to pressure P3, and detects the wrapping strength of the cuff 20 from the comparison result.

[0100] Pressures P1, P2, and P3 are cuff pressures suitable for detecting the wrapping strength of the cuff, which have been determined in advance by experiments, etc. The times at which the cuff pressures become pressures P1 to P3 are defined as times V1 to V3, respectively.

[0101] In this case, the wrapping strength detection unit 260 calculates a change ΔP12, which is the difference between pressure P1 and pressure P2, and a time ΔV12 indicating the time required for the cuff pressure to change by ΔP12 (i.e., time V2-V1). The time ΔV12 is proportional to the change in the fluid volume in the cuff when the pressure changes from P1 to P2. The wrapping strength detection unit 260 calculates a change ΔP23, which is the difference between pressure P2 and pressure P3, and a time ΔV23 indicating the time required for the cuff pressure to change by ΔP23 (i.e., time V3-V2). The time ΔV23 is proportional to the change in the fluid volume in the cuff when the pressure changes from P2 to P3.

[0102] The winding strength detection unit 260 calculates the pressure volume change indexes ΔP12 / ΔV12 and ΔP23 / ΔV23, and compares the two calculated values. Based on the comparison result, the winding strength detection unit 260 detects the winding strength.

[0103] If the comparison result is (ΔP12 / ΔV12)<(ΔP23 / ΔV23), the wrapping strength detection unit 260 detects that the wrapping strength of the cuff 20 is "loosely wrapped." If the comparison result is (ΔP12 / ΔV12)>(ΔP23 / ΔV23), the wrapping strength detection unit 260 detects that the wrapping strength of the cuff 20 is "tightly wrapped." If the comparison result is (ΔP12 / ΔV12)=(ΔP23 / ΔV23), the wrapping strength detection unit 260 detects that the wrapping strength of the cuff 20 is "tightly wrapped."

[0104] "Loose wrapping" is a wrapping state in which the cuff 20 is wrapped loosely around the part to be measured, and the pressure applied to the part to be measured is lower than the appropriate level. "Tight wrapping" is a wrapping state in which the cuff 20 is wrapped appropriately around the part to be measured, and the pressure applied to the part to be measured is at the appropriate level. "Tight wrapping" is a wrapping state in which the cuff 20 is wrapped tightly around the part to be measured, and the pressure applied to the part to be measured is higher than the appropriate level.

[0105] The blood pressure measurement unit 220 sets the decompression speed G1 to be slower as the wrapping strength detected by the wrapping strength detection unit 260 is smaller. For example, for convenience, the decompression speed G1 when the wrapping strength is "loosely wrapped" is set to "G1a", the decompression speed G1 when the wrapping strength is "tightly wrapped" is set to "G1b", and the decompression speed G1 when the wrapping strength is "tightly wrapped" is set to "G1c". In this case, the decompression speed G1a is the slowest, the decompression speed G1c is the fastest, and the decompression speed G1b is intermediate between them (i.e., G1a <G1b<G1c)。

[0106] (Processing Procedure) Fig. 14 is a flowchart showing an example of a processing procedure of sphygmomanometer 100 according to the third embodiment. The flowchart in Fig. 14 corresponds to the flowchart in Fig. 6 in which step S40 is replaced with steps S90, S92, S94, and S96. Therefore, detailed description of the processes other than steps S90, S92, S94, and S96 will not be repeated. However, in step S16, processor 110 drives pump 32 to achieve a constant discharge flow rate per unit time by controlling pump drive circuit 320 for pressurization.

[0107] 14, the processor 110 detects the wrapping strength of the cuff 20 around the measurement site (step S90). The processor 110 determines whether the detected wrapping strength is equal to or greater than the "tight wrapping" level (i.e., "tight wrapping" or "tight wrapping") (step S92). If the wrapping strength is equal to or greater than the "tight wrapping" level (YES in step S92), the processor 110 calculates a depressurization speed G1 based on an estimated pulse pressure, which is a difference between an estimated systolic blood pressure and an estimated diastolic blood pressure, and a pulse rate (step S96). If the wrapping strength is equal to or greater than the "loose wrapping" level (NO in step S92), the processor 110 sets the depressurization speed G1 to a predetermined speed (e.g., 4 mmHg / s) (step S94).

[0108] 14, the configuration has been described in which the decompression rate G1 is calculated based on the estimated pulse pressure and pulse rate in the same manner as in the normal mode when the wrapping strength is "tightly wrapped" or more, but the configuration is not limited to this. For example, the decompression rate G1 may be set to one of the above-mentioned decompression rates G1a to G1c according to the wrapping strength ("loosely wrapped", "tightly wrapped", or "tightly wrapped").

[0109] <Other embodiments> (1) In the above-described embodiment, a program for causing a computer to function and execute the control as described in the above-described flowchart can also be provided. Such a program can be provided as a program product by being recorded on a non-transitory computer-readable recording medium such as a flexible disk, a CD-ROM (Compact Disk Read Only Memory), a secondary storage device, a main storage device, or a memory card that is attached to the computer. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built into the computer. The program can also be provided by downloading via a network.

[0110] (2) The configurations exemplified as the above-mentioned embodiments are merely examples of the configurations of the present invention, and may be combined with other known technologies, or may be modified, such as by omitting some parts, without departing from the scope of the present invention. In addition, the above-mentioned embodiments may be implemented by appropriately adopting the processes and configurations described in other embodiments.

[0111] [Note] As described above, the present embodiment includes the following disclosure.

[0112] [Configuration 1] A blood pressure monitor (100) that measures blood pressure by compressing a measurement site of a user with a cuff (20), comprising: a blood pressure measurement unit (220) that measures the blood pressure of the user based on a pulse wave signal during a depressurization process in which a cuff pressure indicating an internal pressure of the cuff is increased to a pressure greater than a specified pressure, and then the cuff pressure is depressurized; a determination unit (230) that determines whether or not the user is experiencing arrhythmia based on the pulse wave signal during the depressurization process; and a mode setting unit (210) that sets either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, and the blood pressure measurement unit sets a first depressurization rate of the cuff pressure when the first mode is set to be slower than a second depressurization rate of the cuff pressure when the second mode is set.

[0113] [Configuration 2] 2. The blood pressure meter according to configuration 1, wherein the blood pressure measurement unit sets the first depressurization speed based on a pulse wave amplitude indicating an amplitude of a pulse wave signal during the pressurization process.

[0114] [Configuration 3] The blood pressure monitor according to configuration 1, further comprising a memory unit (250) that stores a pulse wave signal during the pressurization process or the depressurization process when the blood pressure of the user is measured by the blood pressure measurement unit, and the blood pressure measurement unit sets the first depressurization speed based on a pulse wave amplitude that indicates an amplitude of the pulse wave signal in the past stored in the memory unit.

[0115] [Configuration 4] 4. The blood pressure monitor according to configuration 2 or 3, wherein the blood pressure measurement unit sets the first decompression speed to a slower value as the pulse wave amplitude is smaller.

[0116] [Configuration 5] 2. The blood pressure monitor according to claim 1, wherein the blood pressure measurement unit sets the first depressurization speed to be slower as the time it takes for the cuff pressure to reach a predetermined pressure in the inflation process becomes longer.

[0117] [Configuration 6] 2. The blood pressure meter according to claim 1, wherein the blood pressure measurement unit estimates a size of the cuff based on a time taken for the cuff pressure to reach a predetermined pressure during the inflation process, and sets the first depressurization speed to be slower as the estimated cuff size is larger.

[0118] [Configuration 7] The blood pressure monitor according to configuration 1, further comprising a wrapping strength detection unit (260) that detects a wrapping strength of the cuff around the measurement site based on the cuff pressure and a volume change of the cuff during the pressurization process, and the blood pressure measurement unit sets the first depressurization speed to be slower as the wrapping strength is smaller.

[0119] [Configuration 8] The blood pressure monitor according to any one of configurations 1 to 7, wherein the blood pressure measurement unit sets the second decompression speed based on an estimated pulse pressure, which is the difference between an estimated systolic blood pressure and an estimated diastolic blood pressure, and a predetermined pulse rate required when measuring the user's blood pressure.

[0120] [Configuration 9] A blood pressure measurement method using a blood pressure monitor (100) for measuring blood pressure by compressing a measurement site of a user with a cuff (20), the method comprising the steps of: measuring the user's blood pressure based on a pulse wave signal during a depressurization process for depressurizing the cuff pressure, which indicates the internal pressure of the cuff, after a pressurization process for pressurizing the cuff pressure indicating the internal pressure of the cuff to a pressure greater than a specified pressure; determining whether or not the user is experiencing arrhythmia based on the pulse wave signal during the depressurization process; and setting either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, wherein a first depressurization rate of the cuff pressure when the first mode is set is slower than a second depressurization rate of the cuff pressure when the second mode is set.

[0121] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0122] 10 main body, 20 cuff, 22 fluid bag, 30 air system component, 31 pressure sensor, 32 pump, 33 valve, 50 display, 51 memory, 52 operation unit, 52A measurement switch, 52B mode selection switch, 53 communication interface, 54 power supply unit, 100 sphygmomanometer, 110 processor, 210 mode setting unit, 220 blood pressure measurement unit, 230 judgment unit, 240 output control unit, 250 memory unit, 260 wrapping strength detection unit, 310 A / D conversion circuit, 320 pump drive circuit, 330 valve drive circuit.

Claims

1. A blood pressure monitor that measures blood pressure by compressing a measurement site of a user with a cuff, a blood pressure measurement unit that measures the user's blood pressure based on a pulse wave signal during a depressurization process of decreasing the cuff pressure after a depressurization process of increasing the cuff pressure indicating the internal pressure of the cuff to a pressure greater than a specified pressure; a determination unit that determines whether or not the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; a mode setting unit that sets either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, The blood pressure measurement unit a first decompression rate of the cuff pressure when the first mode is set is set slower than a second decompression rate of the cuff pressure when the second mode is set; The first decompression speed is set to be slower as the pulse wave amplitude indicating the amplitude of the pulse wave signal during the pressurization process is smaller, or the first decompression speed is set to be slower as the pulse wave amplitude indicating the amplitude of the pulse wave signal over a predetermined period in the past is smaller.

2. A blood pressure monitor as described in claim 1, further comprising a memory unit that stores a pulse wave signal during the pressurization process or the depressurization process when the blood pressure of the user is measured by the blood pressure measuring unit as a pulse wave signal for the specified period in the past.

3. A blood pressure monitor that measures blood pressure by compressing a measurement site of a user with a cuff, a blood pressure measurement unit that measures the user's blood pressure based on a pulse wave signal during a depressurization process of decreasing the cuff pressure after a depressurization process of increasing the cuff pressure indicating the internal pressure of the cuff to a pressure greater than a specified pressure; a determination unit that determines whether or not the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; a mode setting unit that sets either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, The blood pressure measurement unit a first decompression rate of the cuff pressure when the first mode is set is set slower than a second decompression rate of the cuff pressure when the second mode is set; A blood pressure monitor that sets the first decompression speed slower as the time it takes for the cuff pressure to reach a predetermined pressure during the inflation process becomes longer, or sets the first decompression speed slower as the size of the cuff estimated based on the time becomes larger.

4. A blood pressure monitor that measures blood pressure by compressing a measurement site of a user with a cuff, a blood pressure measurement unit that measures the user's blood pressure based on a pulse wave signal during a depressurization process of decreasing the cuff pressure after a depressurization process of increasing the cuff pressure indicating the internal pressure of the cuff to a pressure greater than a specified pressure; a determination unit that determines whether or not the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; a mode setting unit that sets either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, the blood pressure measurement unit sets a first depressurization rate of the cuff pressure when the first mode is set to be slower than a second depressurization rate of the cuff pressure when the second mode is set, a wrapping strength detection unit that detects the wrapping strength of the cuff around the measurement site of the user based on the cuff pressure and the volume change of the cuff during the inflation process, The blood pressure measurement unit sets the first decompression speed to be slower as the wrapping strength is smaller.

5. 5. The blood pressure monitor according to claim 1, wherein the blood pressure measurement unit sets the second decompression rate based on an estimated pulse pressure, which is a difference between an estimated systolic blood pressure and an estimated diastolic blood pressure, and a predetermined pulse rate required when measuring the user's blood pressure.

6. A blood pressure measurement method using a sphygmomanometer that measures blood pressure by compressing a measurement site of a user with a cuff, comprising: a step of increasing a cuff pressure indicating an internal pressure of the cuff to a pressure greater than a predetermined pressure, and then measuring the user's blood pressure based on a pulse wave signal during a step of decreasing the cuff pressure; determining whether the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; setting either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, a first depressurization rate of the cuff pressure when the first mode is set is slower than a second depressurization rate of the cuff pressure when the second mode is set; a step of setting the first decompression rate to be slower as a pulse wave amplitude indicating the amplitude of a pulse wave signal during the pressurization process is smaller, or a step of setting the first decompression rate to be slower as a pulse wave amplitude indicating the amplitude of a pulse wave signal during a predetermined period in the past is smaller.

7. A blood pressure measurement method using a sphygmomanometer that measures blood pressure by compressing a measurement site of a user with a cuff, a step of increasing a cuff pressure indicating an internal pressure of the cuff to a pressure greater than a predetermined pressure, and then measuring the user's blood pressure based on a pulse wave signal during a step of decreasing the cuff pressure; determining whether the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; setting either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, a first depressurization rate of the cuff pressure when the first mode is set is slower than a second depressurization rate of the cuff pressure when the second mode is set; a step of setting the first deflation rate to be slower as the time it takes for the cuff pressure to reach a predetermined pressure during the inflation process is longer, or a step of setting the first deflation rate to be slower as the size of the cuff estimated based on the time is larger.

8. A blood pressure measurement method using a sphygmomanometer that measures blood pressure by compressing a measurement site of a user with a cuff, a step of increasing a cuff pressure indicating an internal pressure of the cuff to a pressure greater than a predetermined pressure, and then measuring the user's blood pressure based on a pulse wave signal during a step of decreasing the cuff pressure; determining whether the user is experiencing arrhythmia based on the pulse wave signal during the decompression process; setting either a first mode in which the arrhythmia determination is performed or a second mode in which the arrhythmia determination is not performed, a first depressurization rate of the cuff pressure when the first mode is set is slower than a second depressurization rate of the cuff pressure when the second mode is set; detecting a wrapping strength of the cuff around the measurement site of the user based on the cuff pressure and a change in volume of the cuff during the inflation process; and setting the first decompression speed to be slower as the wrapping strength is smaller.

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