Electronic blood pressure monitor

Abstract

Electronic blood pressure measuring device (1, 1A, 1B, 1C) which has a peripheral location as a measuring point; the electronic blood pressure measuring device has: a first cuff (20A) which is to be wrapped around the peripheral location; a second cuff (20B) which is to be wrapped around an upper arm; a pressure detection unit (32A, 32B) to detect a first cuff pressure signal representing a pressure of the first cuff (20A), and a second cuff pressure signal representing a pressure of the second cuff (20B); a special processing unit (111, 112) to perform a process to specify an upper arm equilibrium value which represents a cuff pressure in a state in which an internal pressure and an external pressure of an artery of an upper arm are in equilibrium, based on the second cuff pressure signal; a measurement control unit (121, 122) to measure the blood pressure of a person being measured, based on the first cuff pressure signal; and a first volume detection unit (70A) which is arranged at a predetermined position of the first cuff to detect a first arterial volume signal at the peripheral location; where the measurement control unit (121, 122) performs a control to correct a blood pressure value obtained according to the first cuff pressure signal, so that a peripheral equilibrium value, which represents a cuff pressure in a state in which an internal pressure and an external pressure of an artery of the peripheral location are in equilibrium, corresponds to the upper arm equilibrium value; The measurement control unit (121, 122) performs constant control of the arterial volume based on the first arterial volume signal to continuously measure the blood pressure; and The peripheral equilibrium value corresponds to an initial cuff pressure, which represents a reference value of the first cuff pressure signal in the constant control of arterial volume. wherein the measuring control unit (121, 122) detects a control target value in the constant control of the arterial volume, with the pressure of the first cuff (20A) which is set at the upper arm equilibrium value, where the upper arm equilibrium value is the initial cuff pressure, and the cuff pressure, which is obtained when the difference between the value of the first arterial volume signal and the control target value becomes less than or equal to a predetermined value when constant control of the arterial volume is performed, is determined as the blood pressure value.

Description

Technical area

[0001] The present invention relates to electronic blood pressure monitors, and more particularly to an electronic blood pressure monitor that uses a location other than the upper arm as the measurement location. Background of the state of the art

[0002] Blood pressure is a kind of index for analyzing cardiovascular diseases, and conducting a risk analysis based on blood pressure is effective in preventing cardiovascular diseases such as stroke, heart failure, heart attack, and the like. Specifically, early morning high blood pressure, which tends to rise in the morning, is related to heart disease and stroke. Furthermore, within early morning high blood pressure, a symptom in which blood pressure rises rapidly within an hour or an hour and a half after waking up, called the morning surge, is known to have a cause-and-effect relationship with stroke. Therefore, for cardiovascular disease risk analysis, it is useful to have a thorough understanding of the relationship between time (lifestyle habits) and changes in blood pressure.Therefore, blood pressure measurement must be performed continuously over a long period of time. When monitoring patients during and after surgery, checking the medical effect, when treating with antihypertensive medication, and the like, it is very important to continuously measure blood pressure for each heartbeat and monitor changes in blood pressure.

[0003] For blood pressure monitors, both commercially available and those under development, the measurement site covers a wide range of locations, such as the upper arm, wrist, finger, and ear. When measuring blood pressure, the height of the measurement site must be the same as the height of the heart. If there is a difference in height between the measurement site and the heart, a pressure differential will be generated between the blood pressure at the measurement site and the heart due to such a difference, and the measured blood pressure value may contain an error.

[0004] As described in Japanese Unexamined Patent Publication JP H07 - 136133 A (Patent Document 1) and in "Feasibility of ambulatory, continuous 24-hour finger arterial pressure recording" by BP Imholz et al., Hypertension, American Heart Association, January 1993, Vol. 21, Section 1, pp. 65 to 73 (Document 1, no patent), the measurement site such as the finger and the heart position are connected to a tube filled with a liquid having substantially the same specific gravity as blood, the pressure difference is measured, and the blood pressure value is corrected.

[0005] As described in WO 02 / 039 893 A1 (Patent Document 2), a blood pressure monitor using the wrist as the measurement site includes a blood pressure monitor having a function of guiding the height of the wrist to be equal to the height of the heart via a height sensor built therein. [Prior art documents][Patent documents] Patent Document 1: Japanese Unexamined Patent Publication No. JP H 07-136133 A Patent Document 2: Document WO 02 / 039 893 A1 [Document, not a patent]

[0006] Document 1, not a patent: “Feasibility of ambulatory, continuous 24-hour finger arterial pressure recording” by BP Imholz et al., Hypertension, American Heart Association, January 1993, Volume 21, Section 1, pp. 65 to 73.

[0007] JP S62-72606 U describes a blood pressure measuring device with a finger blood pressure measuring device for measuring a blood pressure value by pressing a finger using a cuff, and an upper arm blood pressure measuring device for measuring blood pressure in the upper arm using a second cuff. The blood pressure measuring device includes a correction calculation device for calculating a correction value for the measured blood pressure at the finger based on the measured value at the upper arm.

[0008] JP S61-247431 A describes a method for correcting a non-invasive continuous blood pressure measurement on a finger, as well as a blood pressure monitor that uses the method. The blood pressure monitor is designed to measure blood pressure simultaneously at two different locations on the body. The blood pressure monitor determines correction values ​​alpha and beta for correcting the maximum and minimum blood pressure values. Publication of the inventionProblems to be solved by the invention

[0009] In the method of correcting the blood pressure value according to the state of the art, the change in the height of the measuring site can be tracked, but the tube for connecting the measuring site and the heart position is necessary.

[0010] In addition, fixing the guide as a function of height, as in WO 02 / 039 893 A1 (Patent Document 2), is an effective solution for the wrist, finger, and the like where the height of the measurement site can be adjusted, but it does not become a solution for the blood pressure monitor for a site where the height of the measurement site cannot be adjusted, such as the ear.

[0011] In view of the foregoing, it is an object of the present invention to provide an electronic blood pressure monitor which uses a location (peripheral location) other than the upper arm as a measurement location and which is capable of accurately measuring blood pressure without arranging special hardware. Facility to solve the problem

[0012] According to one aspect of the present invention, there is provided an electronic sphygmomanometer according to claim 1, which has a peripheral site as a measurement site; the electronic sphygmomanometer includes a first cuff to be wrapped around the peripheral site; a second cuff to be wrapped around an upper arm; a pressure detecting unit for detecting a first cuff pressure signal representing a pressure of the first cuff and a second cuff pressure signal representing a pressure of the second cuff; a special processing unit for executing a process to specify an upper arm equilibrium value representing a cuff pressure in a state where an internal pressure and an external pressure of an artery of the upper arm are in balance, based on the second cuff pressure signal;and a measurement control unit for measuring a blood pressure of a person to be measured based on the first cuff pressure signal; wherein the measurement control unit performs control to correct a blood pressure value obtained according to the first cuff pressure signal so that a peripheral equilibrium value representing a cuff pressure in a state where an internal pressure and an external pressure of an artery of the peripheral site are in equilibrium coincides with the upper arm equilibrium value.

[0013] Further, a first volume detection unit is arranged at a predetermined position of the first cuff to detect a first arterial volume signal at the peripheral location; wherein the measurement control unit performs constant control of the arterial volume based on the first arterial volume signal to continuously measure the blood pressure; and the peripheral equilibrium value corresponds to an initial cuff pressure, which is a reference value of the first cuff pressure signal in the constant control of the arterial volume.

[0014] The measurement control unit preferably detects a maximum value of a volume change signal of the peripheral site from the first arterial volume signal in a process of gradually pressurizing or depressurizing the pressure of the first cuff to detect a volume value where the internal pressure and the external pressure of the artery of the peripheral site are in balance as a control target value in the constant arterial volume control, and to detect a value of the first cuff pressure signal corresponding to a time point when the control target value is detected as the initial cuff pressure.The cuff pressure obtained when a difference between the value of the initial arterial volume signal and the control target value becomes less than or equal to a predetermined value when the constant arterial volume control is performed is determined as a temporary blood pressure value; and the temporary blood pressure value is corrected according to a difference between the upper arm equilibrium value and the initial cuff pressure.

[0015] The measurement control unit detects a control target value in the constant control of the arterial volume with the pressure of the first cuff, which is set at the upper arm equilibrium value, wherein the upper arm equilibrium value is the initial cuff pressure, and determines the cuff pressure obtained when a difference between the value of the first arterial volume signal and the control target value becomes less than or equal to a predetermined value when the constant control of the arterial volume is carried out as the blood pressure value.

[0016] The special processing unit preferably specifies either an average blood pressure obtained from the second cuff pressure signal or the cuff pressure at a time when a maximum value of the amplitude of a pressure pulse wave is detected as the upper arm equilibrium value.

[0017] Alternatively, a second volume detection unit is preferably further arranged, which is arranged at a predetermined position of the second cuff to detect a second arterial volume signal at the upper arm; wherein the special processing unit specifies the upper arm equilibrium value by detecting a maximum value of an arterial volume change of the upper arm from the second arterial volume signal in the process of gradually pressurizing or depressurizing the pressure of the second cuff.

[0018] The measurement control unit preferably calculates a temporary blood pressure value based on an amplitude of a pressure pulse wave corresponding to the first cuff pressure signal and corrects the temporary blood pressure value according to a difference between the peripheral equilibrium value and the upper arm equilibrium value.

[0019] The peripheral equilibrium value is preferably defined in advance to be an average blood pressure value obtained from the first cuff pressure signal or a cuff pressure at a time point when a maximum value of an amplitude of a pressure pulse wave is detected.

[0020] The special processing unit preferably specifies either an average blood pressure obtained from the second cuff pressure signal or the cuff pressure at a time when a maximum value of the amplitude of a pressure pulse wave is detected as the upper arm equilibrium value.

[0021] Alternatively, a volume detection unit is further arranged, which is arranged at a predetermined position of the second cuff, to detect an arterial volume signal at the upper arm; wherein the special processing unit specifies the upper arm equilibrium value by detecting a maximum value of an arterial volume change of the upper arm from the arterial volume signal in the process of gradually pressurizing or depressurizing the pressure of the second cuff. Effect of the invention

[0022] According to the present invention, blood pressure can be accurately measured without arranging special hardware even with a blood pressure meter having the peripheral site as a measurement site. Short description of the drawings Fig. 1 is a perspective view of an external appearance of a blood pressure monitor according to each embodiment of the present invention; Fig. 2 is a block diagram showing a hardware configuration of the blood pressure monitor according to a first embodiment of the present invention. Fig. Figure 3 is a graph showing the mechanical characteristics of the artery. Fig. 4 is a flowchart showing a blood pressure measurement process in the first embodiment of the present invention. Fig. 5 is a flowchart showing a control target value detecting process in the first embodiment of the present invention. Fig. 6 is a view showing a detection method of a control target value and a control initial cuff pressure (initial cuff pressure) according to a first embodiment of the present invention. Fig. 7 is a flowchart showing the detection process of the upper arm V0 equivalent cuff pressure (upper arm equilibrium value) in the first embodiment of the present invention. Fig. 8 is a view describing an example of a method for calculating the average blood pressure. Fig. 9 is a flowchart showing another example of the detection process of the upper arm V0 equivalent cuff pressure in the first embodiment of the present invention. Fig. 10 is a view showing a relationship of the maximum value of the pressure pulse wave amplitude and the upper arm V0 equivalent cuff pressure. Fig. 11 is a flowchart showing the blood pressure measurement process according to a variant of the first embodiment of the present invention. Fig. 12 is a flowchart showing the control target value detecting process according to the variation of the first embodiment of the present invention. Fig. 13 are views for describing the method of determining the control target value and the control initial cuff pressure according to the variation of the first embodiment of the present invention. Fig. 14 is a block diagram showing a hardware configuration of a blood pressure monitor according to a second embodiment of the present invention. Fig. 15 is a flowchart showing a detection process of the upper arm V0 equivalent cuff pressure according to the second embodiment of the present invention. Fig. 16 is a block diagram showing a hardware configuration of a blood pressure monitor according to a third embodiment of the present invention. Fig. 17 is a view showing the concept of correcting blood pressure according to the third embodiment of the present invention. Fig. 18 is a flowchart showing a blood pressure measurement process in the third embodiment of the present invention. Fig. 19 is a block diagram showing a hardware configuration of a blood pressure monitor according to a variant of the third embodiment of the present invention. Fig. Figure 20 is a view describing the error in blood pressure caused by physiological factors of the peripheral site (especially the wrist). Embodiment to carry out the invention

[0023] Embodiments of the present invention will be described in detail with reference to the drawings. The same reference numerals designate the same or equivalent parts throughout the figures, and the description thereof will not be repeated. [First Embodiment]<External Appearance and Configuration>

[0024] First, the external appearance and configuration of an electronic blood pressure monitor (hereinafter abbreviated as "blood pressure monitor") according to a first embodiment of the present invention will be described. (Looking at the external appearance)

[0025] With reference to Fig. 1 includes a blood pressure monitor 1, a main body 10, two cuffs 20A, 20B and two tracheas 31A, 31B.

[0026] The cuff 20A can be attached to a peripheral location of a person to be measured, which is a blood pressure measurement location. The cuff 20B can be attached to an upper arm of the person to be measured. The trachea 31A connects the main body 10 and the cuff 20A. The trachea 31B connects the main body 10 and the cuff 20B.

[0027] In the present invention, "the peripheral site" refers to the site other than the upper arm (e.g., the wrist, finger, ear, etc.) among the physical locations where blood pressure can be measured. The wrist is assumed to be the measurement site in the following description.

[0028] Hereinafter, the cuff 20A is also referred to as the “measuring cuff 20A,” and the cuff 20B is also referred to as the “upper arm cuff 20B.”

[0029] A display unit 40 configured, for example, by liquid crystals, and an operation unit 41 for accepting instructions from the user (representative of the person to be measured) are arranged on the surface of the main body 10.

[0030] The operation unit 41 includes, for example, a power supply switch 41A for accepting an input of an instruction to turn the power supply ON or OFF, a measurement switch 41B for accepting the instruction to start the measurement, a stop switch 41C for accepting the instruction to stop the measurement, and a memory switch 41D for accepting the instruction to read out the stored values ​​(measurement data).

[0031] In the present embodiment, the tube 31B connected to the upper arm cuff 20B and the tube 31A connected to the measuring cuff 20A may be removable with respect to the main body 10. (Viewing the hardware configuration)

[0032] With reference to Fig. 2, the blood pressure monitor 1 according to the present invention continuously measures the blood pressure according to a volume compensation method.

[0033] The measuring cuff 20A includes an air bellows 21A and an arterial volume sensor 70A to detect the volume of the artery at the measuring site (wrist).

[0034] The arterial volume sensor 70A is configured by a light-emitting element and a light-receiving element (not shown). The light-emitting element irradiates the artery with light, and the light-receiving element receives the light (the transmitted light) in which the light applied by the light-emitting element is transmitted through the artery, or the light (reflected light) reflected by the artery. The light-emitting element and the light-receiving element are arranged, for example, at a predetermined gap on the inside of the air bladder 21A.

[0035] Alternatively, the arterial volume sensor 70A can detect the volume of the artery using an impedance sensor (impedance plethysmograph). In such a case, the arterial volume sensor 70A must be configured with a plurality of electrodes (a pair of electrodes for current application and a pair of electrodes for voltage detection) to detect the impedance of the site containing the artery.

[0036] The upper arm cuff 20B contains an air bellows 21B.

[0037] In addition to the display unit 40 and the operation unit 41, the main body 10 includes a CPU (Central Processing Unit) 100 for controlling each unit in a concentrated manner and executing various types of calculation processes, a storage unit 42 for storing various types of programs and data, a non-volatile memory (e.g., flash memory) 43 for storing the measurement data, a power supply 44 for supplying power to the CPU 100, and the like, a timing unit 45 for executing the timing operation, an arterial volume detection circuit 76A connected to the arterial volume sensor 70A, a measurement air system 30A, and an upper arm air system 30B.

[0038] The arterial volume detection circuit 76A is configured, for example, by a driving circuit (not shown) for causing a light-emitting element (not shown) to output light at a predetermined timing according to a command signal from the CPU 100, and a detecting circuit (not shown) for detecting the arterial volume of the measurement site by converting the output signal from a light-receiving element (not shown) into a voltage value.

[0039] The air system 30A includes a pressure sensor 32A, a pump 51A, a valve 52A, an oscillation circuit 33A, a pump driver circuit 53A, and a valve driver circuit 54A.

[0040] The pressure sensor 32A is a device for detecting the pressure (cuff pressure) of the air bladder 21A. The pump 51A supplies air to the air bladder 21A to inflate the cuff 20A. The valve 20A is opened and closed to release or enclose the air in the air bladder 21A.

[0041] The pressure sensor 32A is, for example, a capacitance-type pressure sensor in which the capacitance value changes according to the cuff pressure. The oscillation circuit 33A outputs a signal of oscillating frequency corresponding to the capacitance value of the pressure sensor 32A to the CPU 100. The CPU 100 converts the signal received from the oscillation circuit 33A into pressure and detects the pressure. The pump drive circuit 53A controls the driving of the pump 51A based on the control signal supplied from the CPU 100. The valve drive circuit 54A controls the opening / closing of the valve 52A based on the control signal supplied from the CPU 100.

[0042] The air system 30B includes a pressure sensor 32B, a pump 51B, a valve 52B, an oscillation circuit 33B, a pump driver circuit 53B, and a valve driver circuit 54B. This hardware is similar to the air system 30A, and therefore, the description thereof will not be repeated.

[0043] In the present invention, the air systems 30A, 30B are arranged for the measuring cuff 20A and the upper arm cuff 20B, respectively, but a conventional air system may be arranged to change the pressure setting target value.

[0044] The pressure adjustment unit for adjusting the pressure of the cuffs 20A, 20B by pressure build-up and pressure reduction is not limited to the pumps 51A, 51B, the valves 52A, 52B, the pump drive circuits 53A, 53B, and the valve drive circuits 54A, 54B. For example, the pressure adjustment unit for the cuff 20A may include an air cylinder and an actuator for driving the air cylinder in addition to / instead of the hardware described above.

[0045] The cuffs 20A, 20B are pressurized or depressurized by air, however, the fluid delivered to the cuffs 20A, 20B is not limited to air and can be a liquid or a gel. Alternatively, it is not limited to a fluid and can be uniform, microscopic particles, such as microspheres. (Consider the volume compensation method)

[0046] The blood pressure measurement method using the volume compensation method is briefly described below.

[0047] The volume compensation method is a method of compressing the artery with a cuff from outside the body part, which generates the pressure (cuff pressure) for compressing the measurement site and the internal pressure of the artery of the measurement site, that is, the blood pressure balance by constantly maintaining the volume of the artery, which constantly pulsates in synchronization with the heartbeat, and continuously obtaining the blood pressure value by detecting the cuff pressure when the equilibrium state is maintained.

[0048] The graph showing the mechanical characteristics of the artery of the Fig. Figure 3 shows the relationship between the arterial internal and external pressure difference Ptr and the arterial volume V, with the arterial internal and external pressure difference Ptr shown on the horizontal axis and the arterial volume V shown on the vertical axis. The arterial internal and external pressure difference Ptr indicates the difference between the arterial internal pressure Pa and the cuff pressure Pc applied to the body part from the outside by the cuff.

[0049] As shown in the graph, the mechanical characteristics of the artery typically exhibit strong nonlinearity, with the "compliance" of the artery (the amount of change in volume due to pulsation) reaching a maximum value when the arterial internal and external pressure difference Ptr is 0 (equilibrium state), i.e., when the arterial wall is in the unstressed state. In other words, the follow-up property (evolution property) of the volume change with respect to the pressure change becomes a maximum. In the volume compensation method, the blood pressure is controlled by sequentially controlling the ex vivo pressure (cuff pressure) so that the detected arterial volume always becomes a capacity value at the time when the arterial internal and external pressure difference Ptr becomes 0.Up to this point, the capacitance value V0 at the time when the arterial internal and external pressure difference Ptr becomes 0 (the state in which the internal and external pressures of the artery at the measurement site are in equilibrium) before blood pressure measurement is detected as the "control target value." The cuff pressure at the time the capacitance value V0 is detected is detected as the "control initial cuff pressure." In the present embodiment, the cuff pressure is also referred to as the "V0 equivalent cuff pressure of the measurement site."

[0050] However, the blood pressure value contains errors even if the capacitance value V0 is accurately detected if the position of the measurement site does not match the height of the heart.

[0051] Shifts with heart level are less likely to occur when the measurement site is the upper arm, but high-speed response of the measurement pressure is generally necessary when measuring blood pressure using the volume compensation method. Therefore, a peripheral location, such as the wrist, is used for the measurement site to minimize the pressure build-up and pressure release mechanism. Therefore, if the measurement site is lower than the heart level, the user must position the measurement site at the level of the heart, where the cuff pressure (control initial pressure) at the time the arterial internal and external pressure difference Ptr becomes 0 will be higher than the cuff pressure obtained when the measurement site coincides with the heart level.If the measurement location is shifted upward from the level of the heart, the cuff pressure (control initial pressure) at the time when the arterial internal and external pressure difference Ptr becomes 0 will be lower than the cuff pressure obtained when the measurement location is at the level of the heart. Therefore, if the cuff pressure obtained when the arterial volume is at the level of the control target value (V0) as the blood pressure is measured, the blood pressure cannot be accurately measured if the measurement location is at a level shifted from the position of the heart.

[0052] On the other hand, when the measurement site is the upper arm, an error caused by height shift is less likely to occur. Therefore, the blood pressure monitor 1 according to the present embodiment performs a process of correcting the error caused by height shift using the upper arm V0 equivalent cuff pressure. The "upper arm V0 equivalent cuff pressure" is the cuff pressure in a state where the internal pressure and external pressure of the upper arm artery are in balance.

[0053] Fig. Figure 3 shows the error of the upper arm V0 equivalent cuff pressure and the V0 equivalent cuff pressure of the measurement site when the height of the measurement site is shifted to a lower position compared to the position of the heart. (Viewing the functional configuration)

[0054] The block diagram of the Fig. 2 also shows the functional configuration of the CPU 100. The CPU 100 includes a specifying unit 111 and a measurement control unit 121 as functions thereof.

[0055] The specifying unit 111 performs a process of specifying the upper arm V0 equivalent cuff pressure based on the upper arm cuff pressure signal output from the oscillation circuit 33B. For example, the specifying unit 111 specifies an average blood pressure calculated based on the upper arm cuff pressure signal as the upper arm V0 equivalent cuff pressure.

[0056] The measurement control unit 121 controls the measurement of the blood pressure of the subject based on the cuff pressure signal of the measurement site output from the oscillation circuit 33A. Furthermore, the measurement control unit 121 controls the correcting of the blood pressure value obtained according to the cuff pressure signal of the measurement site so that the V0 equivalent cuff pressure of the measurement site coincides with the upper arm V0 equivalent cuff pressure.

[0057] The blood pressure monitor 1 according to the present embodiment continuously measures the blood pressure according to the volume compensation method so that the V0 equivalent cuff pressure of the measurement site agrees with the control initial cuff pressure in the servo control (arterial volume constant control).

[0058] Therefore, in the present embodiment, the measurement control unit 121 performs the following processes. In other words, when the servo control is performed, the cuff pressure obtained when the difference between the value of the arterial volume signal obtained from the arterial volume detection circuit 76A and the control target value becomes less than or equal to a predetermined value is determined as a temporary blood pressure value. The determined temporary blood pressure value is corrected according to the difference between the upper arm V0 equivalent cuff pressure and the control initial cuff pressure. The blood pressure value after the correction is output as the measurement result. That is, the blood pressure value after the correction is displayed, for example, on the display unit 40 and / or stored in the flash memory 43.

[0059] The functions of the specifying unit 111 and the measurement control unit 121 may be realized by executing the software stored in the storage unit 42, or may be realized at least in part by hardware. <Betrachten des Betriebes>

[0060] The operation of the blood pressure monitor 1 according to the present embodiment will now be described. (Blood pressure measurement process)

[0061] The blood pressure measurement process in the first embodiment of the present invention will now be described with reference to the flowchart of Fig. 4. The processes described in the flow chart of the Fig. 4 are stored in the storage unit 42 in advance as a program, and the function of the blood pressure measurement process is realized when the CPU 100 reads out the program and executes the same.

[0062] The CPU 100 executes the initialization process (ST2) when it detects that the power supply switch 41A is pressed (ST1). Specifically, a predetermined area of ​​the memory unit 42 is initialized, the air from the air bladders 21A and 21B is expelled, and the 0 mmHg correction of the pressure sensors 32A and 32B is performed.

[0063] After initialization is completed, the CPU 100 determines whether the measurement switch 41B is pressed or not. If the measurement switch 41B is pressed (ST3), the specifying unit 111 executes the upper arm V0 equivalent cuff pressure detection process (ST4). This process will be described in detail later.

[0064] The measurement control unit 121 then performs a control target value detection process (ST5). In the present embodiment, the control target value (V0) and the control initial cuff pressure are determined using a known method. This process will also be described in detail later.

[0065] The order of executing the process of step ST4 and the process of step ST5 is not relevant.

[0066] The measurement control unit 121 then calculates the blood pressure correction value (ST6). The correction value is calculated using the following equation. Correction value=control initial cuff pressure−upper arm−V0−equivalent cuff pressure

[0067] The cuff's internal pressure is then adjusted so that the cuff pressure signal at the measurement site matches the initial control cuff pressure (ST7). The initial control cuff pressure becomes a reference value for the cuff pressure signal at the measurement site in constant arterial volume control.

[0068] The cuff pressure is then feedback-controlled so that the difference between the arterial volume signal and the control target value (V0) is minimized (ST8). This means that constant arterial volume control is performed. In this case, the cuff pressure obtained when the difference between the arterial volume signal and the control target value becomes smaller than a predetermined value (threshold) is determined as the temporary blood pressure value (ST9, ST10).

[0069] The measurement control unit 121 corrects the temporary blood pressure value determined in the manner described above with the correction value obtained in step ST6 (ST11). The blood pressure correction is calculated using the following equation. Blood pressure value = volume compensation method = blood pressure correction value

[0070] The feedback control continues until the stop signal is turned ON by the input of the stop switch 41C after the lapse of a predetermined time or the like (ST12).

[0071] Therefore, in the present embodiment, the (temporary) blood pressure value is measured once using a normal measurement method in the volume compensation method. The blood pressure value is then corrected with the blood pressure obtained when measured with the upper arm as a reference. That is, the blood pressure value in the volume compensation method is corrected according to the difference between the upper arm V0 equivalent cuff pressure and the V0 equivalent cuff pressure of the measurement site. Therefore, even if the height of the measurement site is shifted from the position of the heart, the error caused by the shift can be reduced. As a result, the blood pressure value can be accurately measured even if the measurement site is not a peripheral site. (Detection process of the control target value)

[0072] With reference to Fig. 5, the measurement control unit 121 initializes the storage area (e.g., the predetermined area of ​​the storage unit 42) to store the maximum value of the arterial volume change (hereinafter also referred to as “arterial volume maximum value”) and the cuff pressure at the relevant time (ST101).

[0073] The pump drive circuit 53A is then controlled to drive to gradually build up the pressure of the measuring cuff 20A at a low speed of about 3 mmHg / sec in pressure (ST102).

[0074] During pressure buildup, the measurement control unit 121 detects a signal (arterial volume signal) from the arterial volume detection circuit 76A (ST103). The measurement control unit 121 detects the arterial volume change signal, which indicates the amount of change in the arterial volume signal for each heartbeat. The arterial volume change signal can be obtained, for example, by filtering the arterial volume signal. Both the arterial volume signal and the arterial volume change signal can be detected in the arterial volume detection circuit 76A.

[0075] The value of the arterial volume signal is assumed to be stored in time sequences corresponding to the cuff pressure during pressure build-up.

[0076] The measurement control unit 12 determines whether the detected arterial volume change is a maximum or not (ST104). If it is determined that the detected arterial volume change is a maximum ("≥ maximum arterial volume value" in ST104), the measurement control unit 121 updates the maximum value of the arterial volume change and the cuff pressure of the relevant time (ST105). After such a process is completed, the process proceeds to step ST106.

[0077] If it is determined that the detected arterial volume change is not a maximum in step ST104 (“< arterial volume maximum value” in step ST104), the process of step ST105 is skipped, and the process proceeds to step ST106.

[0078] In step ST106, the measurement control unit 121 determines whether the cuff pressure is greater than or equal to a predetermined value (e.g., 180 mmHg). If it is determined that the cuff pressure has not reached the predetermined value ("< predetermined pressure build-up value" in step ST106), the process returns to step ST102, and the above processes are repeated. If it is determined that the cuff pressure has reached the predetermined value ("≥ predetermined pressure build-up value" in step ST106), the process proceeds to step ST107.

[0079] In step ST107, the measurement control unit 121 confirms the average value of the arterial volume signal for one heartbeat corresponding to the maximum arterial volume change as the control target value (V0). More specifically, the arterial volume signal for one heartbeat when the arterial volume change is maximum is specified by the cuff pressure stored in a predetermined storage area. The average value of the specified arterial volume signal for one heartbeat is calculated as the control target value. The measurement control unit 121 then confirms the cuff pressure at the relevant time, that is, the cuff pressure stored in a predetermined storage area, as the control initial cuff pressure.

[0080] After the process ST107 is completed, the process returns to the main routine.

[0081] With reference to Fig. 6, the detection of the control target value and the control initial cuff pressure of the present embodiment will be described more specifically. Fig. 6(A) shows the cuff pressure of the measuring cuff 20A along the time axis. Fig. 6(B) shows the arterial volume signal of the measurement site along the time axis, equal to Fig. 6(A). Fig. 6(C) shows the arterial volume change signal of the measurement site along the time axis, equal to Fig. 6(A).

[0082] With reference to Fig. 6, the maximum value of the arterial volume change signal is detected during the process of increasing the cuff pressure at a constant rate to a predetermined value P1. The time at which the maximum value of the arterial volume signal is detected is represented by time tm. For example, the average value of the arterial volume signal at time tm is detected as the control target value (V0). Furthermore, the cuff pressure at time tm is detected as the control initial cuff pressure (PC0).

[0083] When the control target value and the control initial cuff pressure are detected in such a way, the cuff pressure is set to the control initial cuff pressure (PC0) as described above (ST7 of the Fig. 4). The time at which the cuff pressure is set to the initial control cuff pressure is displayed as time t1. After that (time t2), the control gain adjustment is started, and the optimal control gain is determined. Constant arterial volume control is then started (ST8 of the Fig. 4). In the constant arterial volume control, which is shown after time t3, the pressure of the measuring cuff 20A is fine-tuned so that the value of the arterial volume signal at the measurement site matches the control target value. The resulting cuff pressure is determined as the (temporary) blood pressure value. (An example of the detection process of the upper arm V0 equivalent cuff pressure)

[0084] In the present embodiment, the specifying unit 111 specifies the average blood pressure calculated by using the air system 30B for the upper arm as the upper arm V0 equivalent cuff pressure.

[0085] With reference to Fig. 7, the specifying unit 111 closes the valve 52B connected to the upper arm cuff 20B and builds up the cuff pressure to a predetermined pressure (e.g., 180 mmHg) with the pump 51B (ST201, "< predetermined pressure" in ST202). The pressure buildup can be carried out up to a systolic blood pressure (maximum blood pressure) estimated during the pressure buildup + a predetermined value (e.g., 40 mmHg).

[0086] After the pressure is built up to the predetermined pressure (“≥ predetermined pressure” in ST202), the pump 51B is stopped and the valve 52B is gradually opened to gradually reduce the cuff pressure (ST203).

[0087] The specifying unit 111 calculates the blood pressure using the oscillometric method during the gradual pressure reduction process (ST204). Specifically, the pressure change (pressure pulse wave) involved in the arterial volume change superimposed on the cuff pressure is extracted. A predetermined algorithm is then applied to the extracted pressure pulse wave signal to calculate the blood pressure, i.e., the systolic blood pressure and the diastolic blood pressure.

[0088] The pressure reduction continues at a constant rate until the blood pressure is calculated (NO in ST205).

[0089] After the blood pressure is calculated (YES in ST205), the valve 52B is fully opened to expel the air in the cuff 20B. The average blood pressure is calculated as the upper arm V0 equivalent cuff pressure (ST206).

[0090] The average blood pressure is calculated using the following equation by dividing the calculated systolic blood pressure and the diastolic blood pressure. Average blood pressure = diastolic blood pressure + (systolic blood pressure - diastolic blood pressure) / 3

[0091] The process returns to the main routine after the process of step ST206 is completed.

[0092] The blood pressure is calculated in the pressure reduction process in the present embodiment, but it may be calculated in the pressure build-up process.

[0093] As in Fig. As shown in Figure 8, the average blood pressure can be calculated by the area average value of the blood pressure waveform for one heartbeat of the pressure pulse wave amplitude. That is, the pressure value which is the average of the area of ​​the hatched area of ​​the Fig. 8 can be calculated as the average blood pressure.

[0094] In this case, the calculation process of diastolic blood pressure and systolic blood pressure as shown in the flow chart of Fig. 7 (ST204), is not necessary. Instead, a process of specifying the pressure pulse wave for a heartbeat at the low cuff pressure (e.g., 30 mmHg) less than or equal to the diastolic blood pressure may be performed. (Other examples of the upper arm V0 equivalent cuff pressure detection process)

[0095] The average blood pressure is specified as the upper arm V0 equivalent cuff pressure in the above example, but is not limited to this. For example, the cuff pressure at the time when the maximum point of the pressure pulse wave amplitude is detected during the pressure build-up process can be specified as the upper arm V0 equivalent cuff pressure.

[0096] With reference to Fig. 9, the storage area (e.g., the predetermined area of ​​the storage unit 42) for storing the maximum value of the pressure pulse wave amplitude and the cuff pressure at that time is first initialized (ST1201).

[0097] The valve 52B connected to the upper arm cuff 20B is closed, and the pressure change (pressure pulse wave) involved in the arterial volume change superimposed on the cuff pressure is extracted when the cuff pressure is gradually built up in pressure with the pump 51B (ST1202, ST1203).

[0098] The specifying unit 111 determines whether the amplitude of the pressure pulse wave is a maximum or not (ST1204). If it is a maximum ("≥ maximum value of the pressure pulse wave amplitude" in ST1204), the maximum value of the pressure pulse wave and the cuff pressure at that time are updated (ST1205). The process then proceeds to step ST1206.

[0099] If the pressure pulse wave amplitude is not a maximum (“< maximum value of pressure pulse wave amplitude” in ST1204), the process of step ST1205 is skipped, and the process proceeds to step ST1206.

[0100] In step ST1206, it is determined whether the cuff pressure has reached a predetermined value (e.g., 180 mmHg). If it is determined that the cuff pressure has not reached the predetermined pressure ("< predetermined pressure value" in ST1206), the process returns to step ST1202, and the above operation is repeated.

[0101] When the cuff pressure reaches the predetermined value (“≥ predetermined pressure build-up value” in ST1206), the pump 51B is stopped and the valve 52B is opened to expel the air in the cuff 20B.

[0102] The specifying unit 111 confirms the cuff pressure obtained when the pressure pulse wave amplitude is maximum as the upper arm V0 equivalent cuff pressure (ST1207). After the process is completed, the process returns to the main routine.

[0103] In the present example, the maximum value of the pressure pulse wave amplitude is detected during pressure build-up, but it can be detected during pressure reduction.

[0104] Fig. Figure 10 shows the upper arm V0 equivalent cuff pressure when the maximum pressure pulse wave amplitude is detected during pressure buildup. When the pressure pulse wave amplitude is at a maximum, the cuff pressure is essentially equal to the average blood pressure. (Variant of the first embodiment)

[0105] In the first embodiment, the blood pressure is directly corrected by the difference (correction value) of the upper arm V0 equivalent cuff pressure and the control initial cuff pressure after the blood pressure is measured according to the volume compensation method by a known method.

[0106] In the present variant, on the other hand, the control target value and the control initial cuff pressure used in the constant control of the arterial volume are corrected to indirectly correct the blood pressure value, which can be obtained according to the volume compensation method.

[0107] Only the parts which are different from the first embodiment will be described below.

[0108] In the flow chart of the Fig. 11, which shows the blood pressure measurement process according to the variant of the first embodiment of the present invention, the same step numbers are used for the processes similar to the flowchart of Fig. 4. The description of this will therefore not be repeated.

[0109] With reference to Fig. 11, the control target value detection process is different in the present variant, and accordingly, the process of step ST5A is used instead of step ST5 in Fig. 4. The processes of steps ST6 and ST11 of the Fig. 4 are not necessary.

[0110] The control target value detection process executed in step ST5A will be described with reference to the flowchart of Fig. 12 and the graphs of the Fig. 13 described. Fig. 13(A) shows the cuff pressure signal of the measuring cuff 20A along the time axis. Fig. 13(B) shows the arterial volume signal of the measurement site along the same time axis as Fig. 13(A).

[0111] With reference to Fig. 12 and Fig. 13(A), the measurement control unit 121 first sets the cuff pressure of the upper arm V0 equivalent cuff pressure detected in step ST4 (ST1101).

[0112] The arterial volume signal at the relevant time is then detected (ST1102), and the average value of the arterial volume signal for one heartbeat is determined as the control target value (V0 of the measurement site). The cuff pressure at the relevant time is determined as the control initial cuff pressure (ST1103). This means that the control initial cuff pressure and the upper arm V0 equivalent cuff pressure are equal in this variant.

[0113] According to the variant of the present embodiment, the control target value is determined with the control initial cuff pressure as the upper arm V0 equivalent cuff pressure. That is, in the present variant, the control target value does not coincide with the arterial volume value in a state where the internal pressure and external pressure of the artery at the measurement site are in a state of equilibrium when the height of the measurement site is shifted.

[0114] The error in the pressure value caused by the shift in the height of the measurement site and the heart can be reduced by feedback control of the cuff pressure so that it agrees with the corrected control target value, as in the present variant.

[0115] Furthermore, in the present embodiment, the control target value can be detected in a short time because the control initial cuff pressure is determined first. As a result, continuous blood pressure measurement can be started more quickly than in the first embodiment. [Second embodiment]

[0116] Then, a second embodiment of the present invention will be described below.

[0117] In the first embodiment and its variant, the upper arm V0 equivalent cuff pressure is detected based on the pressure pulse wave signal of the upper arm cuff 20B. In the present embodiment, on the other hand, the upper arm V0 equivalent cuff pressure is detected based on the arterial volume signal by a method similar to detecting the control initial cuff pressure in the first embodiment.

[0118] The external appearance, basic configuration, and operation of the blood pressure monitor according to the present embodiment are similar to the first embodiment. Therefore, only the parts that are different from the first embodiment will be described below.

[0119] Fig. 14 shows a hardware configuration of a blood pressure monitor 1A according to the second embodiment of the present invention.

[0120] With reference to Fig. 14, an arterial volume sensor 70B is also disposed in the upper arm cuff 20B in the present invention. Therefore, the arterial volume detection circuit 76B is also incorporated in the main body 10.

[0121] The configurations of the arterial volume sensor 70B and the arterial volume detection circuit 76B are similar to the arterial volume sensor 70A and the arterial volume detection circuit 76A in the measurement cuff 20A, respectively. Therefore, the description thereof will not be repeated.

[0122] In Fig. 14, a CPU 100A is shown instead of the CPU 100 because the functions performed by the CPU of the blood pressure monitor 1A are different from the first embodiment.

[0123] The CPU 100A includes a specifying unit 112 instead of the specifying unit 111 of the first embodiment. The function of the measurement control unit 121 is similar to that of the first embodiment.

[0124] The specifying unit 112 detects the maximum value of the upper arm volume change signal based on the signal from the arterial volume detection circuit 76B. The cuff pressure at the time the maximum value of the volume change signal is detected is specified as the upper arm V0 equivalent cuff pressure.

[0125] The blood pressure measurement process according to the present invention is basically similar to the flow chart of Fig. 4 shown in the first embodiment. Only the detection process of the upper arm V0 equivalent cuff pressure, which is performed in step ST5 of the Fig. 4 is executed is different.

[0126] The detection process of the upper arm V0 equivalent cuff pressure according to the present embodiment will be described with reference to the flowchart of Fig. 15 described.

[0127] First, the specifying unit 112 initializes a storage area (e.g., a predetermined area of ​​the storage unit 42) to store the maximum value of the arterial volume change of the upper arm and the cuff pressure at the relevant time (ST2201).

[0128] The valve driver circuit 54B is then driven to close the valve 52b, and the pump driver circuit 53B is driven to build up the pressure of the upper arm cuff 20B (ST2202).

[0129] During pressure build-up, the specifying unit 112 detects the signal (arterial volume signal) from the arterial volume detection circuit 76B (St2203). In addition, the arterial volume change signal, which indicates the amount of change for each heartbeat of the arterial volume signal, is detected. During pressure build-up, for example, it is assumed that the arterial volume signal is stored in time series corresponding to the cuff pressure.

[0130] The specifying unit 112 determines whether the detected arterial volume change is a maximum (ST2204). If it is determined that the detected arterial volume change is a maximum ("≥ maximum value of arterial volume change" in step ST2204), the maximum value of the arterial volume change and the cuff pressure at the relevant time are updated (ST2205). The process proceeds to step ST2206 after such a process is completed.

[0131] If it is determined that the detected arterial volume change is not a maximum in step ST2204 (“< maximum value of arterial volume change” in ST2204), the process of step ST2205 is skipped, and the process proceeds to step ST2206.

[0132] In step ST2206, the specifying unit 112 determines whether the cuff pressure is greater than or equal to a predetermined value (e.g., 180 mmHg). If it is determined that the cuff pressure has not reached the predetermined value ("< predetermined pressure build-up value" in ST2206), the process returns to step ST2202, and the above processes are repeated. If it is determined that the cuff pressure has reached the predetermined value ("≥ predetermined pressure build-up value" in ST2206), the process proceeds to step ST2207.

[0133] In step ST2207, the specifying unit 112 determines the cuff pressure at the time the maximum value of the arterial volume is detected as the upper arm V0 equivalent cuff pressure. That is, the upper arm V0 equivalent cuff pressure represents the cuff pressure equivalent to (corresponding to) the average value (upper arm V0) of the arterial volume signal for one heartbeat in which the amplitude is a maximum.

[0134] After the process of step ST2207 is completed, the process returns to the main routine.

[0135] In the present invention, the maximum value of arterial volume change is detected during pressure build-up, but it may be detected during pressure reduction.

[0136] The measurement process according to the variant of the first embodiment and the upper arm V0 equivalent cuff pressure detection process of the present embodiment may be combined. [Third Embodiment]

[0137] The blood pressure monitors in the first and second embodiments measure the blood pressure of the measurement site by the volume compensation method, but may measure the blood pressure by other methods as long as they are blood pressure monitors having the measurement site as the peripheral site.

[0138] The blood pressure monitor according to the present invention measures blood pressure, for example, using the oscillometric method.

[0139] The external appearance, basic configuration, and operation of the blood pressure monitor according to the present embodiment are similar to the first embodiment. Therefore, only parts that are different from the first embodiment will be described below.

[0140] Fig. 16 shows a hardware configuration of a blood pressure monitor 1B according to the present embodiment.

[0141] With reference to Fig. 16, the blood pressure monitor 1B according to the present embodiment does not include the arterial volume sensor 70A and the arterial volume detection circuit 76A.

[0142] In Fig. 16, a CPU 100B is shown instead of the CPU 100 because the functions performed by the CPU of the blood pressure monitor 1B are different from the first embodiment.

[0143] The CPU 100B includes a measurement control unit 122 instead of the measurement control unit 121 of the first embodiment. The function of the specifying unit 111 is similar to the first embodiment.

[0144] The measurement control unit 122 calculates a temporary blood pressure value based on the amplitude of the pressure pulse wave of the measurement site obtained from the oscillation circuit 33A. The temporary blood pressure value is corrected according to the difference between the V0 equivalent cuff pressure of the measurement site and the upper arm V0 equivalent cuff pressure. In the present embodiment, the V0 equivalent cuff pressure of the measurement site can be specified by the method similar to that when the specifying unit 111 of the first embodiment specifies the upper arm V0 equivalent cuff pressure. That is, the V0 equivalent cuff pressure of the measurement site can represent one of the average blood pressures obtained from the cuff pressure signal of the measurement site and the cuff pressure at the time when the maximum value of the amplitude of the pressure pulse wave is detected.

[0145] The concept of correcting blood pressure in the present embodiment will be briefly explained with reference to Fig. 17 described.

[0146] When blood pressure is measured using the oscillometric method, the envelope curve of the pressure pulse wave amplitude is used. The envelope curve of the pressure pulse wave amplitude at the measurement site does not match the envelope curve of the pressure pulse wave amplitude of the upper arm if the height of the measurement site (e.g., the wrist) is shifted relative to the level of the heart. Therefore, the upper arm V0 equivalent cuff pressure and the V0 equivalent cuff pressure at the measurement site do not match.

[0147] Therefore, when measuring blood pressure at a height that is offset from the measurement site, an error in the measured value occurs due to the difference between the upper arm V0 equivalent cuff pressure and the V0 equivalent cuff pressure of the measurement site. Therefore, in the present embodiment, the difference between the upper arm V0 equivalent cuff pressure and the V0 equivalent cuff pressure of the measurement site, which is the cause of the error, is also used to correct the blood pressure.

[0148] The blood pressure measurement process in the present embodiment is described using the flowchart of Fig. 18 described. In Fig. 18 are assigned the same step numbers for the processes, similar to the flow chart of the Fig. 4. The description of them will therefore not be repeated.

[0149] In the present embodiment, the start of the procedure for detecting the upper arm V0 equivalent cuff pressure (ST4) is similar to the first embodiment, but differs in the subsequent processes.

[0150] With reference to Fig. 18, when the upper arm V0 equivalent cuff pressure is detected, the measurement control unit 122 closes the valve 52A connected to the measuring cuff 20A and builds up the cuff pressure to a predetermined pressure (e.g., 180 mmHg) with the pump 51A (ST55, "< predetermined pressure" in ST56). Likewise, in this case, the pressure can be increased up to the systolic blood pressure (maximum blood pressure) estimated during the pressure build-up + a predetermined value (e.g., 40 mmHg).

[0151] After pressure buildup up to the predetermined pressure ("≥ predetermined pressure" in ST56), the storage area (e.g., the predetermined area of ​​the storage unit 42) is first initialized to store the maximum value of the pressure pulse wave amplitude and the cuff pressure at that time (ST57). Pump 51A is then stopped, and valve 52A is gradually opened to gradually reduce the cuff pressure (ST58).

[0152] The measurement control unit 122 calculates the blood pressure using the oscillometric method in the gradual pressure reduction process (ST59 to ST61). Specifically, the pressure change (pressure pulse wave) involved in the arterial volume change, superimposed on the cuff pressure, is extracted. When the amplitude of the extracted pressure pulse wave is maximum ("≥ maximum value of pressure pulse wave amplitude" in ST59), the maximum value of the pressure pulse wave amplitude and the cuff pressure are updated at the relevant time (ST60).

[0153] The measurement control unit 122 then performs the blood pressure calculation process (ST61). The blood pressure calculation is performed based on the relationship between the envelope curve of the amplitude value of the pressure pulse wave and the cuff pressure.

[0154] The above processes (ST58 to ST61) are repeated until the blood pressures (systolic blood pressure and diastolic blood pressure) are determined (NO in ST62).

[0155] After the blood pressures are determined, the measurement control unit 122 calculates the blood pressure correction value (ST62). The blood pressure correction value is calculated using the following equation. Correction value=V0−equivalent cuff pressure of the measurement site−upper arm−V0−equivalent cuff pressure.

[0156] The V0 equivalent cuff pressure of the measurement site can, for example, be the cuff pressure value obtained when the pressure pulse wave amplitude is at its maximum (value stored in ST60). It can be a value equivalent to the average blood pressure.

[0157] Finally, the blood pressure value calculated in step ST61 is corrected by the blood pressure correction value obtained in step ST63 (ST64). The blood pressure correction is performed using the following equation. Blood pressure value = blood pressure correction value

[0158] In the present embodiment, since the systolic blood pressure and the diastolic blood pressure are measured, the correction value is subtracted from the respective value in step ST64.

[0159] In the present invention, the blood pressure is calculated in the pressure reduction process, but the blood pressure may be calculated in the pressure build-up process.

[0160] The error in the measured value due to the difference in the measurement site (upper arm and peripheral site) can be reduced, even with the blood pressure monitor that uses the oscillometric method as described above.

[0161] The oscillometric method is used in the present embodiment, but other blood pressure calculation methods such as the Korotkoff sound method and the volume vibration method may be used. (Variant)

[0162] The blood pressure measurement process according to the present embodiment and the upper arm V0 equivalent cuff pressure detection process according to the second embodiment can be combined. The hardware configuration of the blood pressure monitor in such a case is described in Fig. 19 shown.

[0163] With reference to Fig. 19, a blood pressure monitor 1C according to the present embodiment includes an arterial volume sensor 70B and an arterial volume detection circuit 76B, similar to the blood pressure monitor 1A of the second embodiment.

[0164] In Fig. 19, a CPU 100C is shown instead of the CPU100B because the functions performed by the CPU of the blood pressure monitor 1C are different from those of the third embodiment.

[0165] The CPU 100C includes the specifying unit 112 described in the second embodiment and the measurement control unit 122 described in the third embodiment. The specifying unit 112 specifies the upper arm V0 equivalent cuff pressure using a method similar to the initial cuff pressure detection control of the arterial volume constant control. The measurement control unit 122 measures the (temporary) blood pressure according to the oscillometric method and corrects the measured blood pressure with the upper arm V0 equivalent cuff pressure. The functions of the specifying unit 112 and the measurement control unit 122 have already been described, and therefore, a detailed description thereof will not be repeated.

[0166] Therefore, in each embodiment and in each variant of the present invention, the error in the measurement value caused by the shift in the height of the measurement site (the peripheral site) can be reduced by using the upper arm V0 equivalent cuff pressure.

[0167] In addition, the error caused by biological factors at the peripheral site (especially the wrist) can be resolved by performing correction control of the peripheral site's blood pressure using the upper arm V0 equivalent cuff pressure. This will be described specifically.

[0168] Two arteries run through the wrist. The artery that runs along the thumb side of the wrist is called the radial artery, and the artery that runs along the little finger side is called the ulnar artery. Considering the depth at which the two arteries run (depth from the surface of the wrist), the radial artery generally runs more on the surface than the ulnar artery. Obviously, the depth of the position at which the artery runs and the difference in the depth of the radial artery and the ulnar artery vary among people. Therefore, when the wrist is compressed with the cuff, two envelope curves of the pulse wave amplitude are detected when the artery is viewed individually, as shown in Fig.20, because the pressure transmitted to the two arteries varies from person to person. The envelope curve currently detected by the blood pressure monitor is the sum of the two envelope curves, and therefore, blood pressure cannot be measured accurately.

[0169] On the upper arm, on the other hand, blood pressure is calculated based on an envelope curve, and therefore, the error due to the physiological factors of the measurement site does not occur. Therefore, according to each embodiment and each variant of the present invention, the error in the measured value due to such physiological factors can also be resolved.

[0170] In each embodiment and variant, the calculation of the correction value and the like are performed for each measurement because the altitude shift is taken into account. However, if only the physiological factor is taken into account, the correction value calculated once can be saved, and the blood pressure can be corrected for subsequent processes based on the saved correction value.

[0171] The embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is defined by the claims rather than by the description provided above, and all modifications equivalent in meaning to the claims and within the scope of the claims are intended to be embraced herein. Description of the symbols 1, 1A, 1B, 1C electronic blood pressure monitor 10 Main part 20A, 20B cuff 21A, 21B air bellows 30A, 30B air system 31A, 31B trachea 32A, 32B pressure sensor 33A, 33B oscillation circuit 40 display unit 41 Control unit 41A power supply switch 41B measuring switch 41C Stop switch 41D memory switch 42 storage unit 43 Flash memory 44 Power supply 45 time cycle unit 51A, 51B pump 52A, 52B valve 53A, 53B Pump driver circuit 54A, 54B valve driver circuit 70A, 70B arterial volume sensor 76A, 76B Arterial volume detection circuit 100 CPU 111, 112 Specifying unit 121, 122 Measurement control unit

Claims

[1] Electronic blood pressure monitor (1, 1A, 1B, 1C) which has a peripheral location as a measuring location; the electronic blood pressure monitor comprises: a first cuff (20A) to be wrapped around the peripheral site; a second cuff (20B) to be wrapped around an upper arm; a pressure detection unit (32A, 32B) for detecting a first cuff pressure signal representing a pressure of the first cuff (20A) and a second cuff pressure signal representing a pressure of the second cuff (20B); a special processing unit (111, 112) for performing a process to specify an upper arm equilibrium value representing a cuff pressure in a state in which an internal pressure and an external pressure of an artery of an upper arm are in equilibrium, based on the second cuff pressure signal; a measurement control unit (121, 122) for measuring a blood pressure of a person to be measured based on the first cuff pressure signal; and a first volume detection unit (70A) arranged at a predetermined position of the first cuff to detect a first arterial volume signal at the peripheral location; where the measurement control unit (121, 122) executes control to correct a blood pressure value obtained according to the first cuff pressure signal so that a peripheral equilibrium value representing a cuff pressure in a state in which an internal pressure and an external pressure of an artery of the peripheral site are in equilibrium coincides with the upper arm equilibrium value; the measurement control unit (121, 122) carries out constant control of the arterial volume based on the first arterial volume signal to continuously measure the blood pressure; and the peripheral equilibrium value corresponds to an initial cuff pressure, which represents a reference value of the first cuff pressure signal in the constant control of the arterial volume, wherein the measurement control unit (121, 122) detects a control target value in the constant control of the arterial volume, with the pressure of the first cuff (20A) being set at the upper arm equilibrium value, the upper arm equilibrium value being the initial cuff pressure, and the cuff pressure obtained when a difference between the value of the first arterial volume signal and the control target value becomes less than or equal to a predetermined value when the constant arterial volume control is carried out is determined as the blood pressure value. [2] The electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 1, wherein the measurement control unit (121, 122) detects a maximum value of a volume change signal of the peripheral site from the first arterial volume signal in a process of gradually pressurizing or depressurizing the pressure of the first cuff to detect a volume value in a state where the internal pressure and the external pressure of the artery of the peripheral site are in balance as a control target value in the constant control of the arterial volume, and to detect a value of the first cuff pressure signal corresponding to a time point when the control target value is detected as the initial cuff pressure; determines the cuff pressure obtained when a difference between the value of the first arterial volume signal and the control target value becomes less than or equal to a predetermined value when the constant arterial volume control is carried out, as a temporary blood pressure value; and the temporary blood pressure value is corrected according to a difference between the upper arm equilibrium value and the initial cuff pressure. [3] The electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 1, wherein the special processing unit (111, 112) specifies either an average blood pressure obtained from the second cuff pressure signal or the cuff pressure at a time point at which a maximum value of the amplitude of a pressure pulse wave is detected as the upper arm equilibrium value. [4] Electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 1, further comprising: a second volume detection unit (70B) arranged at a predetermined position of the second cuff to detect a second arterial volume signal at the upper arm; wherein the special processing unit (111, 112) specifies the upper arm equilibrium value by detecting a maximum value of an arterial volume change of the upper arm from the second arterial volume signal in the process of gradually pressurizing or depressurizing the pressure of the second cuff. [5] The electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 1, wherein the measurement control unit (121, 122) calculates a temporary blood pressure value based on an amplitude of a pressure pulse wave corresponding to the first cuff pressure signal, and corrects the temporary blood pressure value according to a difference between the peripheral equilibrium value and the upper arm equilibrium value. [6] The electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 5, wherein the peripheral equilibrium value is defined in advance to be an average blood pressure obtained from the first cuff pressure signal or a cuff pressure at a time point at which a maximum value of an amplitude of a pressure pulse wave is detected. [7] The electronic blood pressure monitor (1, 1A, 1B, 1C) according to claim 5, wherein the special processing unit (111, 112) specifies either an average blood pressure obtained from the second cuff pressure signal or the cuff pressure at a time point at which a maximum value of the amplitude of a pressure pulse wave is detected as the upper arm equilibrium value. [8] Electronic blood pressure monitor (1A, 1C) according to claim 5, further comprising: a volume detection unit (70B) arranged at a predetermined position of the second cuff (20B) to detect an arterial volume signal at the upper arm; wherein the special processing unit (111,112) specifies the upper arm equilibrium value by detecting a maximum value of an arterial volume change of the upper arm from the arterial volume signal in the process of gradually increasing or decreasing the pressure of the second cuff.

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