JP5035114B2 - Electronic blood pressure monitor - Google Patents

Description

  The present invention relates to an electronic sphygmomanometer, and more particularly to an electronic sphygmomanometer that measures blood pressure using a volume compensation method.

  Some conventional electronic sphygmomanometers measure blood pressure according to an oscillometric method. In the oscillometric method, an arm band (cuff) is wound around the measurement site of the measurement subject in advance. During measurement, the pressure in the cuff (cuff pressure) is increased higher than the maximum blood pressure, and then gradually reduced. In the process of reducing the pressure, pulsation generated in the artery at the measurement site is detected as a pulse wave signal by the pressure sensor through the cuff. The systolic blood pressure and the diastolic blood pressure are determined using the cuff pressure at that time and the magnitude of the detected pulsation (the amplitude of the pulse wave signal). As used herein, systolic blood pressure refers to systolic blood pressure, and diastolic blood pressure refers to diastolic blood pressure.

  On the other hand, there is a volume compensation type sphygmomanometer that can measure a blood pressure waveform continuously every heartbeat in a non-invasive manner (Patent Document 1: Japanese Patent Publication No. 59-5296).

  The volume compensation method is as follows. That is, the artery is compressed from outside the living body with a cuff, and the pressure of the measurement site (cuff pressure) and the internal pressure of the artery at the measurement site, that is, the blood pressure, are maintained by constantly maintaining the volume of the artery that pulsates in synchronization with the heartbeat. In this method, the blood pressure value is continuously obtained by detecting the cuff pressure when the equilibrium state is maintained and the equilibrium state is maintained.

  Therefore, in the volume compensation method, detection of the volume value (hereinafter referred to as the control target value) when the artery is in an unloaded state (a natural state in which no pressure is applied to the vascular wall of the artery), and this unloaded state is maintained. Two points to do (servo control) are important.

  As a method for determining the control target value, an arterial volume change signal (AC component of volume pulse wave) is detected while gradually compressing the artery with a cuff. A method has been proposed in which the level of the detected arterial volume signal (DC component of the volume pulse wave) is detected as a control target value when it is detected that the level of the detected arterial volume change signal is maximized. (Patent Document 2: Japanese Patent Publication No. 1-331370).

When the control target value is determined, after setting the cuff pressure to the control initial cuff pressure, the cuff pressure is servo-controlled so that the level of the arterial volume change signal is minimized, that is, the arterial volume is constant. If it is detected in the servo control process that the level of the arterial volume change signal is smaller than a predetermined value, the cuff pressure at this time becomes equal to the blood pressure. The blood pressure can be continuously measured by measuring the cuff pressure while maintaining this state.
Japanese Patent Publication No.59-5296 Japanese Patent Publication No. 1-331370

  In the electronic sphygmomanometer using the volume compensation method described above, the servo control method is a combination of PID control (Proportional Control, Integral Control, and Derivative Control) which is feedback control. Refers to control that converges to a target value). That is, the cuff pressure is the sum of the deviation between the current arterial volume signal and the control target value obtained in advance, the integral of the deviation, and the derivative of the deviation multiplied by a constant: constant value (hereinafter referred to as servo gain). Is output as a control amount. In order to measure blood pressure with high accuracy, it is necessary to adjust the optimum value of the servo gain according to the control target.

  In the configuration of the above-mentioned Patent Document 2 (Japanese Patent Publication No. 1-331370), the servo gain is gradually increased at a constant speed, and the elimination rate of the volume pulse wave signal (the amplitude / volume of the volume pulse wave signal being controlled / The servo gain at the time when the amplitude of the volume pulse wave signal before control becomes smaller than a predetermined value is used in blood pressure measurement. However, this method takes time to determine the servo gain, and blood pressure measurement cannot be started quickly.

  Therefore, an object of the present invention is to provide an electronic sphygmomanometer that can quickly determine a servo gain for the servo control in an electronic sphygmomanometer that measures blood pressure according to the volume compensation method under servo control. It is.

  An electronic sphygmomanometer for measuring blood pressure according to a volume compensation method according to an aspect of the present invention includes a cuff attached to a blood pressure measurement site, and pressure detection means for detecting a cuff pressure representing the pressure in the cuff. , A volume detecting means for detecting an arterial volume signal indicating the volume of the artery at the measurement site in the process of applying the cuff pressure, and a cuff pressure adjusting means for adjusting the cuff pressure by pressurization and decompression And a control means.

  The control means controls the cuff pressure adjusting means, the first control means for setting the cuff pressure to an initial cuff pressure representing a specific pressure value, and after setting the cuff pressure to the initial cuff pressure, Servo control means for servo-controlling the cuff pressure adjusting means using the servo gain so that the arterial volume is constant, and the initial gain is added when the servo control by the servo control means is performed Servo gain determination means for determining a specific servo gain for blood pressure measurement while sequentially updating the servo gain, and the amplitude of the arterial volume signal detected when the cuff pressure is set to the initial cuff pressure Is the maximum, and the initial gain is calculated by dividing the estimated arterial pulse pressure value by the maximum amplitude value detected for the arterial volume signal.

  Preferably, the control means includes an initial gain detection means for detecting an initial gain, and the initial gain detection means determines the maximum blood pressure and the minimum blood pressure based on the cuff pressure detected by the pressure detection means in the process of detecting the initial cuff pressure. The pulse pressure is estimated by calculating

  Preferably, the servo gain determination means calculates the updated servo gain when the amount of change in the arterial volume detected by the volume detection means converges to a minimum value in the process of servo control while updating the servo gain value. Determine a specific servo gain.

  Preferably, the servo gain determination means determines the initial cuff pressure and the amplitude of the arterial volume signal detected by the volume detection means and the cuff pressure for each pulse wave when the servo control is performed by the servo control means. Having amplitude ratio detection means for detecting the ratio of the amplitude of the arterial volume signal detected when set to, and detecting that the ratio detected by the amplitude ratio detection means is smaller than a predetermined value When it is detected that the amount of arterial volume change has converged to a minimum value.

  An electronic sphygmomanometer for measuring blood pressure according to a volume compensation method according to another aspect of the present invention includes a cuff attached to a blood pressure measurement site, and pressure detection means for detecting a cuff pressure representing the pressure in the cuff. , Provided with a volume detecting means for detecting an arterial volume signal indicating the volume of the artery at the measurement site, a cuff pressure adjusting means for adjusting the cuff pressure by pressurization and decompression, and a control means. .

  The control means includes a setting means for setting the cuff pressure to an initial cuff pressure representing a specific pressure value, and after setting the cuff pressure to the initial cuff pressure, based on a specific servo gain for blood pressure measurement, the artery Servo control means for servo-controlling the cuff pressure adjusting means such that the volume of the cuff is constant, and determination processing means for performing processing for determining a specific servo gain, the determination processing means comprising: cuff pressure adjusting means The amplitude pulse pressure detecting means for detecting the maximum amplitude of the arterial volume signal and the pulse pressure of the artery in the process of increasing the cuff pressure to the predetermined value by the step or the process of decreasing the cuff pressure from the predetermined value Based on the relationship between the arterial pulse pressure and the amount of change in volume between the arterial pulse pressures, the characteristic estimation means for estimating the elastic characteristics of the artery, the elastic characteristics of the artery estimated by the characteristic estimation means, Yo Have based on a predetermined correlation equation showing the relationship between elastic properties and volume change erasure rate, and erasing ratio calculating means for calculating the volume change erasure rate for arterial and. Then, the specific pulse gain is determined by dividing the detected pulse pressure by a value obtained by multiplying the detected maximum amplitude value of the arterial volume signal by the calculated volume change erasure rate.

  Preferably, the determination processing means detects the cuff pressure at the time when the amplitude of the arterial volume signal becomes maximum as the initial cuff pressure in the process of increasing the cuff pressure to a predetermined value or reducing the cuff pressure from the predetermined value. And a blood pressure estimating means for estimating the minimum blood pressure and the maximum blood pressure in parallel with the processing by the detection processing means, and the characteristic estimation means includes the minimum blood pressure and the maximum blood pressure. By dividing the difference in the value of the arterial volume signal between the time points at which each is detected by the difference between the systolic blood pressure and the systolic blood pressure, the elasticity characteristic of the artery is estimated.

  Preferably, the control unit receives a detection signal from the pressure detection unit and determines a cuff pressure corresponding to the detection signal as a blood pressure when the servo control unit performs servo control with a specific servo gain. Blood pressure determining means, and further comprising storage means for storing the blood pressure determined by the blood pressure determining means.

  Preferably, the detection processing means further derives an initial cuff pressure based on the detection signal from the pressure detection means and the arterial volume signal.

  According to the present invention, prior to the servo gain adjustment processing in the configuration of the electronic sphygmomanometer based on the volume compensation method, an initial gain value in an amount corresponding to the ratio between the pulse pressure and the maximum arterial volume indicated by the arterial volume signal is detected. During adjustment, the servo gain is updated by sequentially adding the detected initial gain values.

  Thereby, the time required for servo gain adjustment can be shortened. As a result, the servo gain for blood pressure measurement according to the volume compensation method can be determined quickly, and blood pressure measurement can be started quickly.

  Further, according to the present invention, in the process of detecting the initial cuff pressure for blood pressure measurement, the volume change elimination rate is calculated, and the calculated volume change elimination rate is used to detect a specific servo gain for blood pressure measurement. Therefore, the servo gain adjustment process in the configuration of the electronic blood pressure monitor based on the volume compensation method can be omitted. As a result, the servo gain for blood pressure measurement according to the volume compensation method can be determined quickly, and blood pressure measurement can be started quickly.

  Further, since the volume change elimination rate described above is calculated according to the elastic characteristics of the artery, a specific servo gain for blood pressure measurement that is optimal for the subject can be set using the calculated volume change elimination rate. Thereby, the blood pressure can be accurately measured by the volume compensation method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts, and description thereof will not be repeated.

  The inventors have obtained the following knowledge about the determination of the servo gain related to the servo control for maintaining the no-load state of the artery in the volume compensation method.

  As the servo gain is increased, the amplitude of the arterial volume change signal gradually decreases and the amplitude converges to the minimum value. That is, in the process of increasing the servo gain by servo control, the magnitude of the pulsation detected from the cuff pressure signal converges, and the amount of change in the arterial volume also converges to the minimum value. If the servo gain is further increased, the control system becomes unstable, and unnecessary high frequency component vibrations occur in the control signal. Further, when the servo gain is increased, abnormal control oscillation occurs in the control signal and control becomes impossible. Therefore, the inventors use this property to detect the time when the amplitude of the arterial volume change signal is minimized in the process of performing servo control while increasing the servo gain. The knowledge that the optimum servo gain for maintaining the state can be determined was obtained.

  Hereinafter, an electronic sphygmomanometer that measures blood pressure using the volume compensation method according to each embodiment will be described. After determining the optimum servo gain, the electronic sphygmomanometer according to each embodiment continuously measures the blood pressure by a volume compensation method using a procedure disclosed in Patent Document 1, for example. The electronic sphygmomanometer applies an external pressure to the artery from outside the living body, and performs servo control using the determined optimum servo gain so that the in-vivo pressure and the intra-arterial pressure, that is, blood pressure are always balanced. That is, the electronic sphygmomanometer continuously measures blood pressure by finely adjusting the cuff pressure so that the arterial wall is maintained in an unloaded state and measuring the in vitro pressure at that time (unloaded state).

FIG. 1 is an external perspective view of an electronic blood pressure monitor 1 according to each embodiment of the present invention.
Referring to FIG. 1, an electronic sphygmomanometer 1 includes a main body 10 and a cuff 20 that can be wound around the limb of a person to be measured. The main body 10 is attached to the cuff 20. On the surface of the main body unit 10, a display unit 40 made of, for example, liquid crystal and an operation unit 41 for receiving instructions from a user (a person to be measured) are arranged. The operation unit 41 includes a plurality of switches.

  In the present embodiment, “limbs” represent an upper limb and a lower limb. That is, the limb includes a part from the wrist to the base of the arm and a part from the ankle to the base of the foot. In the following description, it is assumed that the cuff 20 is attached to the wrist of the measurement subject.

  The electronic sphygmomanometer 1 in each embodiment will be described by taking an example in which the main body 10 is attached to the cuff 20 as shown in FIG. The main body 10 and the cuff 20 may be connected by an air tube (air tube 31 in FIG. 3 described later).

  FIG. 2 is a diagram showing the concept of controlling the cuff pressure for blood pressure measurement in electronic blood pressure monitor 1 according to each embodiment of the present invention. FIG. 2 shows a state where the cuff 20 is attached to the wrist 200 of the measurement subject.

  Referring to FIG. 2, a cuff pressure adjusting mechanism including a pump 51 and an exhaust valve (hereinafter simply referred to as “valve”) 52 is disposed in the main body 10.

  An air system 30 including a pump 51, a valve 52, and a pressure sensor 32 for detecting the pressure (cuff pressure) in the air bladder 21 is connected to the air bladder 21 contained in the cuff 20 via an air tube 31. Is done. Thus, since the air system 30 is provided in the main body part 10, the thickness of the cuff 20 can be kept thin.

  Inside the air bladder 21, a light emitting element 71 and a light receiving element 72 are arranged at a predetermined interval. In FIG. 2, the light emitting element 71 and the light receiving element 72 are arranged along the circumference of the wrist when the cuff 20 is attached. However, the arrangement is not limited to such an arrangement example.

  FIG. 3 is a block diagram showing a hardware configuration of electronic blood pressure monitor 1 according to each embodiment of the present invention.

  Referring to FIG. 3, cuff 20 of electronic sphygmomanometer 1 includes air bag 21 and arterial volume sensor 70. The arterial volume sensor 70 includes the light emitting element 71 and the light receiving element 72 described above. The light emitting element 71 emits light to the artery, and the light receiving element 72 receives the transmitted light or reflected light of the artery irradiated by the light emitting element 71.

  The arterial volume sensor 70 may be any sensor that can detect the volume of the artery, and may detect the volume of the artery based on impedance. In that case, it replaces with the light emitting element 71 and the light receiving element 72, and the some electrode for detecting the impedance of the site | part containing an artery is contained.

  In addition to the display unit 40 and the operation unit 41 described above, the main unit 10 centrally controls each unit and performs various arithmetic processes, and a program that causes the CPU 100 to perform predetermined operations. And a memory unit 42 for storing various data, a flash memory 43 which is a kind of nonvolatile memory for storing measured blood pressure data, and a power supply 44 for supplying power to each unit via the CPU 100, And a timer 45 for measuring the current time and outputting the time data to the CPU 100. The operation unit 41 includes a power switch 41A that receives an input of an instruction for turning on or off the power supply, a measurement switch 41B that receives an instruction to start measurement, a stop switch 41C that receives an instruction to stop measurement, and a flash It has a memory switch 41D for receiving an instruction to read information such as blood pressure recorded in the memory 43, and an ID switch 41E operated to input ID (Identifier) information for identifying the measurement subject.

  The main body 10 further includes the air system 30, the cuff pressure adjusting mechanism 50, the oscillation circuit 33, the light emitting element driving circuit 73, and the arterial volume detection circuit 74 described above.

  The adjustment mechanism 50 includes a pump drive circuit 53 and a valve drive circuit 54 in addition to the pump 51 and the valve 52.

  The pump 51 supplies air to the air bladder 21 in order to increase the cuff pressure. The valve 52 is opened and closed to exhaust or seal the air in the air bladder 21. The pump drive circuit 53 controls the drive of the pump 51 based on a control signal given from the CPU 100. The valve drive circuit 54 performs opening / closing control of the valve 52 based on a control signal given from the CPU 100.

  The light emitting element drive circuit 73 causes the light emitting element 71 to emit light at a predetermined timing in response to a command signal from the CPU 100. The arterial volume detection circuit 74 detects the arterial volume based on the signal from the light receiving element 72.

  The pressure sensor 32 is a capacitance-type pressure sensor, and the capacitance value changes depending on the cuff pressure. The oscillation circuit 33 outputs an oscillation frequency signal corresponding to the capacitance value of the pressure sensor 32 to the CPU 100. The CPU 100 detects a pressure by converting a signal obtained from the oscillation circuit 33 into a pressure.

(Embodiment 1)
The servo gain determination operation according to the first embodiment will be described below. In the present embodiment, the time required for determining a specific servo gain (referred to as optimum servo gain) detected in advance to be used for servo control during blood pressure measurement according to the volume compensation method can be shortened so that blood pressure measurement can be started quickly. Therefore, the initial servo gain is calculated in advance, and the current servo gain is updated sequentially by adding the calculated initial servo gain when adjusting the servo gain. This outline will be described.

(Overview)
First, a method for calculating the initial servo gain will be described using Equations 1 to 4 described later. FIG. 4 schematically shows the relationship between the control pulse pressure, the control error, and the servo gain. In FIG. 4, the horizontal axis indicates the passage of time for determining the optimum servo gain, and changes in the control pulse pressure, the control error, and the servo gain are shown on the same time axis.

  In the volume compensation method, the cuff pressure Pc is servo-controlled so that the arterial volume matches the unloaded volume (control target value), that is, the pulsation of the arterial volume is minimized. Referring to FIG. 4, in the servo control, the control amount of cuff pressure Pc (this is referred to as control pulse pressure PPc) is the control error signal (the control error signal is the difference between the control target value and the arterial volume signal value). Is indicated by a value obtained by multiplying the servo gain (G) by the amplitude (Δerr). Therefore, if the control pulse pressure PPc1, which is the control pulse pressure PPc when the arterial volume is unloaded, and the control error amplitude Δerr1, which is the control error amplitude Δerr when the arterial volume is unloaded, are detected in advance (expression Based on 1), the optimum servo gain AG can be calculated.

  The control pulse pressure PPc is indicated by the difference between the maximum blood pressure and the minimum blood pressure. Here, blood pressure values (maximum blood pressure and minimum blood pressure) to be detected during blood pressure measurement according to the volume compensation method can be estimated (detected) by calculation according to the oscillometric method in the process of determining the control target value. Further, the control error amplitude Δerr1 includes the amplitude value of the arterial volume signal before starting servo control (maximum control error value: Δerr-max) and the volume change elimination rate PDR (arterial volume during servo control) by constant arterial volume control. It can be calculated based on (Equation 2) using the amplitude of the change signal / the amplitude of the arterial volume change signal before servo control.

  The arterial volume signal (Δerr-max) before the start of servo control can be detected as the maximum amplitude value of the arterial volume signal when the artery is gradually compressed by the cuff 20. On the other hand, the volume change erasure rate PDR differs depending on the elastic characteristics of the artery of the person to be measured, and therefore cannot normally be detected until actual servo control is performed. Here, if the volume change elimination rate PDR can be estimated in advance by any method, the servo gain necessary to obtain the control pulse pressure PPc1 based on (Equation 3), that is, the optimum servo gain AG is calculated in advance. It is possible.

  As described above, when the volume change erasure rate PDR is not detected in advance, it is impossible to calculate the optimum servo gain AG in advance, so even if the volume change erasure rate PDR cannot be detected in advance. It is desired to detect the optimum servo gain AG within a short time.

  Therefore, in this embodiment, in order to detect the optimum servo gain AG in a short time, a value obtained by dividing the control pulse pressure PPc1 by the control error maximum value Δerr-max based on (Equation 4) is set as the initial servo gain G. Calculate as -init. If the calculated initial servo gain G-init value is sequentially added to the servo gain value during servo control, the optimum servo gain can be reached faster than gradually increasing the servo gain from zero. Become. As a result, it is possible to reduce the time required for servo gain adjustment for obtaining the optimum servo gain. For example, if the volume change erasure rate PDR indicates 50%, the initial servo gain G-init value indicates 50% of the optimum servo gain AG value according to (Equation 3) and (Equation 4). Will do. Therefore, compared with the case where the servo gain value is increased from zero in the servo gain adjustment, the time required for determining the optimum servo gain AG can be reduced by half.

AG = PPc1 / Δerr1 (Formula 1)
Δerr1 = Δerr-max × PDR (Formula 2)
AG = PPc1 / (Δerr-max × PDR) (Formula 3)
G-init = PPc1 / Δerr-max (Equation 4)
(Memory contents)
Here, an example of data stored in the flash memory 43 in Embodiment 1 of the present invention will be described with reference to FIG.

  Referring to FIG. 5, the flash memory 43 stores an area E0 for storing data related to detection of the optimum servo gain AG, an area E1 for storing a predetermined threshold value in advance, a work area E2 and blood pressure measurement data. An area E3 for storing is included. The data in the area E0 will be described later. In the area E1, cuff pressure data PC1 referred to for control target value and initial cuff pressure detection, and threshold value THpdr referred to for servo gain determination are stored in advance. The contents of the areas E0 and E2 are initialized every time blood pressure measurement is started.

  In the region E3, a plurality of measurement data 80 obtained at the time of blood pressure measurement according to the volume compensation method is stored. Each of the measurement data 80 includes, for example, a field 81 of “ID information” and a field 83 of measurement information. The field 81 stores ID information for identifying the person to be measured input by operating the ID switch 41E during blood pressure measurement. In the field 83, data 831 indicating the measurement start date and time and the measurement period of the measurement data 80 timed by the timer 45 and measured blood pressure data 832 (data V (1), V (2),..., V (N)) is stored in association with each other.

(Functional configuration)
FIG. 6 is a functional block diagram showing a functional configuration of the electronic sphygmomanometer 1 according to the embodiment of the present invention.

  Referring to FIG. 6, CPU 100 continuously controls blood pressure by controlling target value detecting unit 102 for detecting a control target value for servo control, cuff pressure setting unit 104 for setting cuff pressure, and blood pressure. Servo control unit 106 that performs feedback control for measurement, blood pressure determination unit 108, servo gain determination unit 109 for determining servo gain, and initial gain detection unit 107 for detecting initial servo gain G-init Including. In FIG. 6, only peripheral hardware that directly transmits and receives signals to and from these units included in the CPU 100 is shown for the sake of simplicity.

  The control target value detection unit 102 performs a process of detecting the initial cuff pressure in the process of increasing the cuff pressure to a predetermined value (for example, 200 mmHg). The control target value detector 102 causes the pump drive circuit 53 to drive the pump 51 and causes the light emitting element drive circuit 73 to drive the light emitting element 71. As the pump 51 is driven, the cuff pressure gradually increases. A signal received by the light receiving element 72 is output to the arterial volume detection circuit 74 by driving the light emitting element 71. The control target value detection unit 102 receives the arterial volume change signal output from the arterial volume detection circuit 74, and detects a change (amplitude) for each heartbeat based on the input arterial volume change signal.

  The control target value detection unit 102 controls the drive of the pump drive circuit 53 until the cuff pressure detected based on the signal input from the oscillation circuit 33 indicates a predetermined value (at this time, the valve 52 is in a closed state). . The control target value detection unit 102 detects the (temporary) maximum value of the amplitude of the arterial volume change signal until the cuff pressure reaches a predetermined value, and inputs the signal from the oscillation circuit 33, and inputs the signal Is converted into a pressure value to detect the cuff pressure. Then, the detected temporary maximum value, the value of the arterial volume signal detected at that time, and the cuff pressure are associated with each other and recorded in the area E2 of the flash memory 43.

  Finally, the value recorded in the region E2 as the maximum value of the arterial volume signal is determined as a control target value (V0) for servo control and stored in the region E0. Further, the cuff pressure stored in the region E2 as the maximum value of the cuff pressure is determined as the initial cuff pressure (MBP) and stored in the region E0.

In the process of reducing the cuff pressure from a predetermined value, the initial cuff pressure may be detected.
When the control target value detection unit 102 detects that the cuff pressure has reached a predetermined value, the control target value detection unit 102 stops driving the pump drive circuit 53. Then, the cuff pressure setting unit 104 reads the initial cuff pressure and the control target value determined from the region E0. The cuff pressure setting unit 104 receives the signal from the oscillation circuit 33, converts the input signal into a cuff pressure, and drives the valve drive circuit 54 until the converted cuff pressure becomes the initial cuff pressure. As a result, the valve 52 is opened, air is discharged from the air bladder 21, and the cuff pressure is reduced from the predetermined cuff pressure to the initial cuff pressure.

  The servo control unit 106 drives the light emitting element driving circuit 73. Based on the signal from the arterial volume detection circuit 74, the pump drive circuit 53 or the valve drive circuit 54 is controlled so that the arterial volume becomes constant.

  More specifically, the servo control unit 106 follows the servo gain so that the difference between the arterial volume signal received from the arterial volume detection circuit 74 and the control target value V0 is minimized (preferably zero). The pump drive circuit 53 or the valve drive circuit 54 is controlled based on the control amount. That is, the pump drive circuit 53 or the valve drive circuit 54 controls the drive of the pump 51 or the opening / closing of the valve 52 so that the value (amplitude value) of the arterial volume change signal is equal to or less than a predetermined threshold value.

  The blood pressure determination unit 108 continuously (periodically) receives a signal (referred to as a “pressure detection signal”) input from the oscillation circuit 33 while the control by the servo control unit 106 is being performed, and the pressure detection signal A process for determining the cuff pressure corresponding to the blood pressure as the blood pressure is performed.

  More specifically, the blood pressure determination unit 108 detects whether or not the difference between the value of the arterial volume signal and the control target value V0 read from the region E0 is equal to or less than a predetermined threshold value. Only when this is the case, the cuff pressure at that time is determined as the blood pressure. The determined blood pressure is stored in time series in the area E2 of the flash memory 43 in accordance with the timing data of the timer 45.

  In order to determine the optimum servo gain, the initial gain detection unit 107 includes a control pulse pressure detection unit 113, and the servo gain determination unit 109 includes a volume change erasure rate calculation unit 111 and a gain update unit 112. The functions of these units will be described later.

  The operation of each functional block included in the CPU 100 may be realized by executing software stored in the memory unit 42, and at least one of these functional blocks is realized by hardware. May be.

  Alternatively, at least one of the blocks described as hardware (circuit) may be realized by the CPU 100 executing software stored in the memory unit 42.

(Blood pressure measurement operation)
Next, the operation of the electronic sphygmomanometer 1 in the present embodiment will be described.

  7, 8 and 11 are flowcharts showing the blood pressure measurement process in the first embodiment of the present invention. The processing shown in the flowchart of FIG. 7 is stored in advance in the memory unit 42 as a program, and the blood pressure measurement processing function is realized by the CPU 100 reading and executing this program. It is assumed that the person to be measured wears the cuff 20 of the electronic sphygmomanometer 1 on the wrist as a measurement site as shown in FIG. 3 when measuring blood pressure.

  Referring to FIG. 8, CPU 100 detects whether or not power switch 41A has been operated (for example, pressed) (step S2). If it is detected that power switch 41A has been operated (YES in step S2), the process proceeds to step S4.

  In step S4, the CPU 100 performs an initialization process. Specifically, predetermined areas of the memory unit 42 and the flash memory 43 are initialized, the air in the air bladder 21 is exhausted, and correction is performed so that the pressure sensor 32 indicates 0 mmHg. At this time, the value of the flag FL for instructing whether or not the optimum servo gain has been determined is initialized. For example, the value of the flag FL is updated to 0. The flag FL is a temporary variable prepared for the flowchart, and indicates a predetermined storage area of an internal memory (not shown) of the CPU 100.

  When the initialization is completed, the CPU 100 detects whether or not the measurement switch 41B has been operated (for example, pressed) (step S6). Wait until the measurement switch 41B is operated. If it is detected that measurement switch 41B is pressed (YES in step S6), the process proceeds to step S8.

  In step S8, the control target value detection unit 102 executes processing for detecting an initial cuff pressure and a control target value, and the initial gain detection unit 113 executes processing for initial servo gain detection in parallel with this processing. The initial cuff pressure, control target value, and initial servo gain are detected as follows.

  The control target value detection unit 102 drives the pump drive circuit 53 to gradually increase the cuff pressure, while the arterial volume signal (DC component of the volume pulse wave signal) PGdc and the arterial volume change signal (volume pulse wave signal AC component) PGac is detected. These signals are detected by the arterial volume detection circuit 74. That is, the arterial volume detection circuit 74 has an HPF (High Pass Filter) circuit (not shown).

  In operation, when the arterial volume detection circuit 74 receives a volume pulse wave signal indicating a change in the volume of the artery from the arterial volume sensor 70, the HPF circuit inputs the input signal to the arterial volume signal PGdc of the DC component of the volume pulse wave signal. Separated into an AC volume arterial volume change signal PGac and output. For example, assuming that the filter constant is 1 Hz, a signal of 1 Hz or less is detected as a DC component, and a signal exceeding 1 Hz is detected as an AC component. The control target value detection unit 102 inputs the arterial volume signal PGdc and the arterial volume change signal PGac from the arterial volume detection circuit 74. Based on the input arterial volume signal PGdc, the amplitude for each heartbeat is detected.

  The control target value detection unit 102 detects whether the amplitude value of the arterial volume change signal PGac detected at present is the maximum, and the value of the arterial volume signal PGdc and the arterial volume detected when the amplitude value is detected as the maximum. The amplitude value of the signal PGdc and the cuff pressure are associated with each other and stored in the region E2. This operation is repeated until the cuff pressure reaches a predetermined pressure. This predetermined pressure is indicated by cuff pressure data PC1 (for example, 200 mmHg) read from area E1 of flash memory 43.

  The amplitude value of the arterial volume change signal PGac corresponds to the maximum value calculated by, for example, extracting the waveform of the arterial volume change signal PGac for one heartbeat and differentiating the extracted waveform. Similarly, the amplitude value of the arterial volume signal PGdc corresponds to the maximum value calculated by, for example, extracting the waveform of the arterial volume signal PGdc for one heartbeat and differentiating the extracted waveform.

  When it is detected that the cuff pressure has reached a predetermined pressure, the maximum value of the arterial volume signal PGdc, the maximum value of the cuff pressure, and the maximum value of the amplitude value of the arterial volume signal PGdc stored in the region E2 are controlled. The target value, initial control cuff pressure, and control error maximum value are determined. Thereby, the control target value, the initial cuff pressure, and the control error maximum value are detected. The detected control target value, initial cuff pressure and maximum control error value are read from region E2 and stored in region E0 as control target value V0, initial cuff pressure MBP and maximum control error value Δerr-max.

  The detection of the control target value V0, the initial cuff pressure MBP, and the control error maximum value Δerr-max will be described in detail with reference to FIGS.

  FIG. 8 is a flowchart showing the control target value, initial cuff pressure, and initial servo gain detection processing in the embodiment of the present invention. FIG. 9 is a diagram for explaining blood pressure measurement processing according to Embodiment 1 of the present invention. In the upper part of FIG. 9, a signal indicating the cuff pressure Pc detected by the pressure sensor 32 is shown along the time axis measured by the timer 45. The middle stage and the lower stage of FIG. 9 show an arterial volume change signal PGac and an arterial volume signal PGdc along the same time axis.

  The procedure of FIG. 8 will be described with reference to FIG. Referring to FIG. 8, control target value detection unit 102 initializes area E2 of flash memory 43 (step S102). At this time, it corresponds to time = 0 in FIG. In the following processing, the maximum value of the arterial volume change signal PGac is updated as needed, and the value until the final value is finally determined as the maximum value is referred to as a “volume change temporary maximum value”.

  Next, the CPU 100 controls the pump drive circuit 53 to increase the cuff pressure (step S104).

  At the stage of increasing the cuff pressure, the control target value detection unit 102 receives the arterial volume signal PGdc and the arterial volume change signal PGac from the arterial volume detection circuit 74, and detects a signal for each heartbeat of both input signals. (Step S106). Then, an amplitude value for each heartbeat is detected for the arterial volume signal PGdc (step S108).

  The control target value detection unit 102 compares the detected amplitude value of the arterial volume change signal PGac with the volume change temporary maximum value read from the region E2, and based on the comparison result, the amplitude value of the arterial volume change signal PGac is It is detected whether or not the change temporary maximum value is exceeded (step S110). If it is detected that the amplitude value of arterial volume change signal PGac is greater than or equal to the volume change temporary maximum value (YES in step S110), the process proceeds to step S112. On the other hand, when it is detected that the value of arterial volume change signal PGac is less than the temporary volume maximum value (NO in step S110), the process proceeds to step S114.

  In step S112, the control target value detection unit 102 stores the detected amplitude value of the arterial volume change signal PGac, the cuff pressure, the value of the arterial volume signal PGdc, and the amplitude value of the arterial volume signal PGdc. When this process ends, the process moves to a step S114.

  In S114 to S120, blood pressure estimation (detection) and pulse pressure calculation (detection) processing are performed in parallel with the control target value detection processing. This process will be described later.

  Thereafter, in step S122, the control target value detection unit 102 detects whether or not the detected cuff pressure Pc indicates a cuff pressure equal to or higher than the predetermined value PC1 read from the region E1. If it is detected that the cuff pressure Pc does not indicate a cuff pressure equal to or higher than the predetermined value PC1 (NO in step S122), the process returns to step S104, and the transition process is similarly repeated. Such loop processing of steps S104 to S122 is performed in a period up to time T0 in FIG.

  On the other hand, when it is detected that cuff pressure Pc indicates a cuff pressure equal to or higher than predetermined value PC1 (YES in step S112), the process proceeds to step S124. In step S124, the maximum value of the arterial volume signal PGdc stored in the region E2 is set as the initial control target value V0, the maximum value of the cuff pressure Pc is set as the initial cuff pressure MBP, and the maximum value of the amplitude value of the arterial volume signal PGdc. Is detected as the maximum control error value Δerr-max, read from the region E2, and stored in the region E0. As a result, the determined initial control target value V0, initial cuff pressure MBP, and control error maximum value Δerr-max are detected.

  Here, a specific example of the blood pressure estimation process in the period until time T0 in FIG. 9 in steps S114 to S116 will be described with reference to FIG. FIG. 10 is a diagram conceptually illustrating a blood pressure estimation method using an oscillometric method. The upper part of FIG. 10 shows the gradually increased cuff pressure along the time axis measured by the timer 45, and the lower part shows the envelope of the amplitude of the arterial volume change signal PGac along the same time axis. Line 600 is shown. For the envelope 600, the amplitude value of the arterial volume change signal PGac detected in step S108 is stored in time series in the region E2 until it is determined YES in step S122. Thereby, envelope 600 is indicated by the amplitude data of time-series arterial volume change signal PGac stored in region E2 when it is determined YES in step S122.

  Referring to envelope 600 in the lower part of FIG. 10, when initial value MAX of amplitude of arterial volume change signal PGac is detected in step S114, initial gain detection unit 107 sets a predetermined constant (for example, Multiply 0.7 and 0.5) to calculate two thresholds TH-DIA and TH-SYS. Then, on the side where the cuff pressure is lower than the cuff pressure MEAN (mean blood pressure) at the time when the maximum value MAX is detected (this corresponds to the time T0 in FIG. 9), the threshold TH-DIA and the envelope 600 intersect. The cuff pressure at that point is estimated as the minimum blood pressure. Further, on the side where the cuff pressure is higher than the cuff pressure MEAN, the cuff pressure at the point where the threshold TH-SYS and the envelope 600 intersect is estimated as the maximum blood pressure.

  When the minimum blood pressure is estimated, for example, the initial gain detection unit 107 updates a flag (hereinafter referred to as “DIA flag”) indicating whether or not the minimum blood pressure has been estimated from 0 to 1. When the systolic blood pressure is estimated, for example, a flag indicating whether or not the systolic blood pressure has been estimated (hereinafter referred to as “SYS flag”) is updated from 0 to 1.

  The initial gain detection unit 107 determines whether the minimum blood pressure and the maximum blood pressure have been estimated (step S116). Specifically, it is determined whether or not the values of the DIA flag and the SYS flag indicate 1. When it is determined that the values of both flags indicate 1 (YES in step S116), the process proceeds to step S118.

  On the other hand, when it is not determined that the values of both flags indicate 1 (one in step S116), the process proceeds to step S122. That is, when it is determined in step S116 that the DIA flag indicates 1, the value of the arterial volume signal PGdc at that time is estimated as the minimum blood pressure, and when it is determined that the SYA flag indicates 1, the arterial volume at that time The value of the signal PGdc is estimated as the maximum blood pressure. When both the minimum and maximum blood pressures are estimated in this way, blood pressure value determination is detected (YES in step S116). If it is determined that the blood pressure value is determined, the determined blood pressure value is stored in the area E2.

  Then, the control pulse pressure detection unit 113 reads the values of the systolic blood pressure and the diastolic blood pressure estimated in steps S114 and S116 from the region E2, calculates the difference between the two blood pressures read (the systolic blood pressure−the diastolic blood pressure), and the control pulse pressure PPc1. Is stored in the area E2 (step S120).

  As a result, the initial control target value V0, the initial cuff pressure MBP, the maximum control error value Δerr-max, and the control pulse pressure PPc1 are detected and stored in the region E0 or E2.

  Thereafter, the initial gain detection unit 107 reads out the control pulse pressure PPc1 from the region E2, reads the control error maximum value Δerr-max from the region E1, and divides the read control pulse pressure PPc1 by the control error maximum value Δerr-max. Is calculated as the value of the initial servo gain G-init. The calculated initial servo gain G-init is stored in the area E0 (step S126). Thereby, the initial servo gain G-init is acquired.

  Next, referring to FIG. 7, servo control unit 106 controls pump drive circuit 53 and valve drive circuit 54 to read the cuff pressure detected based on the signal input from oscillation circuit 33 from region E0. The cuff pressure MBP is set (step S10). In this state, since the optimum servo gain is still determined based on the flag FL (NO in step S12), gain determination processing (step S26) is performed.

  The optimum servo gain determination process (step S26) will be described with reference to the flowchart of FIG. It is assumed that the servo gain referred to by the servo control unit 106 is stored in the area E2.

  Referring to FIG. 11, gain determination unit 109 detects the amplitude value of arterial volume change signal PGac for each heartbeat based on arterial volume change signal PGac input from arterial volume detection circuit 74 (step S302). Then, the volume change erasure rate calculation unit 111 sets the volume change erasure rate PDR (PDR = the amplitude value of the current arterial volume change signal PGac / cuff pressure of the arterial volume change signal PGac detected when the initial cuff pressure is set). (Amplitude value) is calculated and stored in the region E2 (step S304). It is assumed that the amplitude value of the arterial volume change signal PGac detected when the cuff pressure is set to the initial cuff pressure is stored in the internal memory of the CPU 100.

  Next, the gain updating unit 112 rewrites the current servo gain value in the region E2 so as to increase at a constant rate (step S308). Subsequently, the gain updating unit 112 updates the servo gain after the increase in the region E2 by adding the value of the initial servo gain G-init read from the region E0 (step S310). Then, the servo controller 106 reads the updated servo gain from the area E2, and performs servo control using the read servo gain (step S312).

  Next, the gain determination unit 109 determines whether or not the current volume change erasure rate PDR read from the region E2 is equal to or greater than a predetermined erasure rate target value THpdr read from the region E1 (step S316). If it is determined that the volume change erasure rate PDR is equal to or greater than the erasure rate target value THpdr (YES in step S316), if it is determined that the current servo gain is not optimal, the process returns to the main routine of FIG. It is. Here, the erasure rate target value THpdr is a value detected in advance by experiment as a value when the amplitude of the arterial volume change signal PGac converges to the minimum value. Therefore, by following the processing of FIG. Servo control of the cuff pressure is performed so that the difference between this value and the control target value V0 is minimized.

  On the other hand, when it is determined that the volume change erasure rate PDR is less than the erasure rate target value THpdr (NO in step S316), the gain determination unit 109 uses the servo gain used in the blood pressure determination process by the blood pressure determination unit 108 ( The optimum servo gain) is determined as the servo gain stored in the area E2 at this time (step S318). Since the determined optimum servo gain is given to the servo control unit 106, the servo control unit 106 can perform servo control for blood pressure measurement based on the given servo gain.

  Then, 1 is set in the flag FL to instruct that the servo gain has been determined (step S320).

  With the above procedure, the optimum servo gain determination process (step S26) according to the first embodiment is completed.

  Referring to FIG. 7 again, the cuff pressure is set to the initial cuff pressure (step S10), and then servo gain determination processing (step S26) by gain determination unit 109 is performed. The process during this time is performed during the period from time T1 to time T2 in FIG.

  Whether or not the optimum servo gain has been determined in step S12 is detected according to the value of the flag FL. Specifically, when it is detected that the value of the flag FL indicates 1, the optimum servo gain is detected (YES in step S12), and otherwise (NO in step S12), it is determined to be undecided. Then, the process proceeds to the servo gain determination process (step S26).

  When the optimal servo gain has been determined according to the above-described procedure (YES in step S12), the arterial volume constant control is executed by servo control by the servo control unit 106 using the determined optimal servo gain (step S14). Specifically, the servo control unit 106 inputs the arterial volume signal PGdc and the arterial volume change signal PGac from the arterial volume detection circuit 74, and sends the pump drive circuit 53 and the valve drive circuit 54 to the optimum servo gain of the region E2. A control signal based on the determined control amount is output. Thereby, the pump 51 and the valve 52 are driven so that the difference between the detected value of the arterial volume signal PGdc and the control target value V0 is minimized.

  Specifically, the control signals of the pump 51 and the valve 52 are calculated from a value obtained by multiplying the difference between the value of the arterial volume signal PGdc and the control target value V0 by the servo gain. When the servo gain is increased, the pulsation indicated by the cuff pressure is increased by the servo control. That is, in the present embodiment, the servo gain refers to a coefficient that determines the magnitude of cuff pressure pulsation by servo control.

  In the example of FIG. 9, when the optimum servo gain determination process is performed in the period from time T1 to T2, arterial volume constant control (servo control) is started from time T2.

  In parallel with such arterial volume constant control, the blood pressure determination unit 108 executes blood pressure calculation and blood pressure determination processing (steps S16 and S18). Specifically, the cuff pressure Pc detected during the arterial volume constant control is determined as the blood pressure (step S18).

  The determined blood pressure data is stored in the flash memory 43 (step S20). When the process of step S20 ends, the process proceeds to step S22.

  After time T2 shown in FIG. 9, the difference between the arterial volume and the control target value V0 is close to zero by servo control using the determined servo gain. That is, the servo control unit 106 maintains the artery in an unloaded state. Therefore, the cuff pressure Pc detected after time T2 is determined as the blood pressure. That is, the blood pressure determination unit 108 differentiates the waveform of the signal from the maximum value and the minimum value of the amplitude for each heartbeat of the signal indicated by the cuff pressure Pc (external pressure) during the period when the artery wall is maintained in an unloaded state. The maximum value detected by processing is calculated as the maximum blood pressure, the minimum value is calculated as the minimum blood pressure, and stored as measurement data 80 in the region E3.

  Subsequently, in step S22, the CPU 100 detects whether or not the stop switch 41C is operated (for example, pressed). If it is detected that stop switch 41C has not been operated (NO in step S22), the process returns to step S12. When it is detected that the stop switch 41C has been operated (YES in step S22), the blood pressure data measured from the flash memory 43 is read and displayed on the display unit 40 (step S24). Thereby, a series of blood pressure measurement processing ends.

  In the present embodiment, the blood pressure measurement process is terminated when the operation of the stop switch 41C is detected. However, the timer 45 detects that a predetermined time has elapsed since the start of the arterial volume constant control. In some cases, it may be terminated.

  According to the first embodiment, since the initial gain G-init is configured to be sequentially added to the gain at the time of servo control for determining the optimum servo gain, it is faster than gradually increasing the servo gain from zero. The optimum servo gain can be reached, and the time taken to determine the optimum servo gain can be shortened.

(Embodiment 2)
In the second embodiment, the volume change erasure rate PDR during the arterial volume constant control is calculated using the blood pressure-volume characteristic during the control target value detection process. Using this calculated value, the optimum servo gain in servo control is calculated in advance from (Equation 3). As a result, it is possible to reduce the time required to detect the optimum servo gain.

Prior to the description of the second embodiment of the present invention, an outline will be described.
In an electronic blood pressure monitor using a conventional volume compensation method, when performing volume compensation control, the servo gain is gradually increased, and the volume change elimination rate (the amplitude of the arterial volume change signal under control / the amplitude before the control is controlled). A point where the amplitude of the arterial volume change signal becomes smaller than a predetermined value is detected, and blood pressure is measured using the servo gain at this time.

  However, the volume change elimination rate varies depending on the elastic characteristics of the artery, that is, the degree of arteriosclerosis. Specifically, the harder the artery, the worse the responsiveness to pressing, so that the control becomes more difficult and the remaining disappearance (pulse wave signal being controlled) becomes larger. As a result, the volume change erasure rate becomes a large value. Conversely, the softer the artery, the smaller the volume change elimination rate. For this reason, there is an individual difference in the optimum value of the servo gain.

  Therefore, in the second embodiment, the optimal servo gain is set for each subject by detecting the volume change elimination rate PDR according to the elastic characteristic of the artery by calculation.

  Hereinafter, an electronic sphygmomanometer that measures blood pressure using a volume compensation method according to an embodiment of the present invention will be described.

  The appearance and hardware configuration of the electronic sphygmomanometer according to the second embodiment are the same as those shown in FIGS.

(Functional configuration)
FIG. 12 is a functional block diagram showing a functional configuration of the electronic sphygmomanometer 1 according to the second embodiment. 12 differs from the configuration of FIG. 6 in that the configuration of FIG. 12 omits the initial gain calculation unit 107 of FIG. 6 and replaces the gain determination unit 109 and servo control unit 106 of FIG. Thus, the gain determination unit 120 and the servo control unit 109 are provided. The other configuration of FIG. 12 is the same as that shown in FIG.

  The gain determination unit 120 in FIG. 12 includes an erasure rate detection unit 121 having a characteristic estimation unit 122 in order to determine a servo gain at the time of blood pressure measurement using the volume compensation method.

  In the control target value and initial cuff pressure detection processing (hereinafter referred to as “control target value detection processing”), that is, in parallel with the processing by the control target value detection unit 102, the characteristic estimation unit 122 determines the elasticity characteristic of the artery. presume. The characteristic estimation unit 122 receives signals from the oscillation circuit 33 and the arterial volume detection circuit 74.

  The elastic characteristic of the artery can be obtained from the pressure-volume characteristic curve of the blood vessel. The pressure-volume characteristic curve of the blood vessel is an arterial volume signal PGdc obtained from a photoelectric volume pulse wave or an impedance pulse wave when the cuff pressure is increased or decreased. In the present embodiment, in the control target value detection process Detected. The slope and the amount of change of the pressure-volume characteristic curve represent the elastic characteristic of the artery.

  FIG. 13 is a diagram showing blood pressure-volume characteristics, in which the arterial volume signal is shown on the Y-axis, and the pressing force (unit: mmHg) is shown on the X-axis. Referring to FIG. 13, the pressure-volume characteristic of a soft blood vessel is indicated by a curve La, and the pressure-volume characteristic of a hard blood vessel is indicated by a curve Lb. The curve La has a large slope near the internal / external pressure difference of 0 (near the pressing force P0), and the curve Lb has a small slope. That is, in a blood vessel in which hardening is recognized, a pressure-volume characteristic curve (hereinafter referred to as a “characteristic curve”) near a blood pressure difference of 0 (that is, in the vicinity of average blood pressure) is compared with a blood vessel in which hardening is not recognized (or less). ) Has a small inclination. Here, the slope of each characteristic curve is obtained by “ΔPGdc / pulse pressure”. The pulse pressure is the difference between the maximum blood pressure and the minimum blood pressure, and ΔPGdc indicates the difference between the arterial volume at the time of detecting the minimum blood pressure and the arterial volume at the time of detection of the maximum blood pressure.

  Therefore, in the second embodiment, the characteristic estimation unit 122 estimates the highest blood pressure and the lowest blood pressure of the measurement subject in accordance with the oscillometric method in the control target value detection process. That is, in the process of gradually increasing (or reducing) the cuff pressure to a predetermined value, the measurement subject's maximum blood pressure and minimum blood pressure are estimated based on the pressure detection signal from the oscillation circuit 33.

  When the systolic blood pressure and the systolic blood pressure are estimated, the characteristic estimation unit 122 identifies the values of the arterial volume signal (PGdc-SYS, PGdc-DIA) at the time when the estimated systolic blood pressure and the estimated systolic blood pressure are detected. The slope of the characteristic curve is calculated by dividing ΔPGdc, which is the difference between PGdc-SYS and PGdc-DIA, by the pulse pressure (estimated systolic blood pressure−estimated diastolic blood pressure). A value indicating the calculated slope is given to the erasure rate detection unit 121.

  Thus, in the second embodiment, the slope of the characteristic curve can be calculated using the cuff pressure and the arterial volume signal detected in the control target value detection process. Therefore, it is possible to estimate the elastic characteristic of the artery efficiently and with high accuracy. However, it is not always necessary to use the cuff pressure and the arterial volume signal detected in the control target value detection process. For example, the elastic characteristics based on the measurement data of the measurement subject in the past (for example, the latest) by the blood pressure determination unit 108. May be calculated.

  The erasure rate detection unit 121 responds to the arterial elasticity characteristic based on the inclination of the characteristic curve calculated by the characteristic estimation unit 122 and the correlation between the inclination of the characteristic curve (blood vessel elastic characteristic) and the volume change erasure rate. The volume change elimination rate PDR is detected. Then, the gain determination unit 120 uses this value to calculate the optimum servo gain value based on (Equation 3).

  FIG. 14 shows the correlation between the slope of the blood vessel characteristic curve and the volume change elimination rate. In a two-dimensional coordinate plane, the “volume change elimination rate” is taken on the Y axis and the “inclination of the pressure-volume characteristic curve” is taken on the X axis. y = -7.3861x + 0.5405).

  The correlation in FIG. 14 is based on clinical data obtained by measuring blood vessels in an invasive state. As shown in FIG. 14, the volume change elimination rate increases as the slope of the characteristic curve decreases (that is, as the artery is harder), and decreases as the slope of the characteristic curve increases (ie, as the artery is softer).

  In the second embodiment, the “volume change elimination rate” on the Y axis is calculated for each subject. That is, the erasure rate detection unit 121 converts the slope of the characteristic curve calculated by the characteristic estimation unit 122 into a volume change erasure rate PDR based on the linear function formula. Instead of the linear function equation, a data table representing the correlation between the erasure rate target value and the slope of the characteristic curve may be used.

  The volume change erasure rate PDR calculated by the erasure rate detection unit 121 is given to the gain determination unit 120.

  In the present embodiment, the “servo gain for blood pressure measurement” is a period during which blood pressure is continuously measured (determined) by the volume compensation method, that is, the cuff pressure and the internal pressure of the artery are maintained in an equilibrium state. This is the optimum servo gain used in the servo control for the period. Therefore, when the optimum servo gain is determined, the servo control unit 109 fixes the servo gain to the optimum servo gain (time T2 in FIG. 5) and starts servo control. Therefore, in the second embodiment, the adjustment time for determining the optimum servo gain from time T1 to time T2 in FIG. 5 can be omitted.

  The blood pressure determination unit 108 continuously (periodically) receives a signal (referred to as a “pressure detection signal”) input from the oscillation circuit 33 while the control by the servo control unit 109 is being performed. A process for determining the cuff pressure corresponding to the blood pressure as the blood pressure is performed. More specifically, after the servo gain is fixed, the blood pressure determination unit 116 determines whether or not the difference between the value of the arterial volume signal and the control target value is equal to or less than a predetermined threshold value. Only when this is the case, the cuff pressure at that time is determined as the blood pressure. The determined blood pressure is stored in the flash memory 43 in time series.

(About operation)
Next, the operation of the electronic sphygmomanometer 1 according to the second embodiment will be described.

  15 to 17 are flowcharts showing blood pressure measurement processing according to Embodiment 2 of the present invention. FIG. 18 is a diagram showing an example of the contents of the flash memory 43 according to the second embodiment.

  The flowchart of FIG. 15 differs from the flowchart of FIG. 9 in that the processing in steps S4 and S8 in FIG. 9 is replaced with steps S4a and S8a in FIG. The other processes in FIG. 15 are the same as those shown in FIG.

  Referring to FIG. 15, when CPU 100 determines that power switch 41A has been operated (YES in step S2), CPU 100 performs an initialization process in step S4. At this time, the values of the flags FL and FR are also initialized. The flag FR indicates whether or not blood pressure estimation is completed during the servo gain adjustment period.

  When initialization is completed and CPU 100 determines that measurement switch 41B has been pressed (YES in step S6), the process proceeds to step S8a.

  In step S8a, the control target value detection unit 102 performs processing for detecting an initial cuff pressure and a control target value. The detection of the initial cuff pressure and the control target value will be described in detail with reference to FIG. 16 and FIG.

  FIG. 16 is a flowchart showing a control target value detection process in the embodiment of the present invention.

  Referring to FIG. 16, control target value detection unit 102 performs the processing of steps S102 to S112 in the same manner as in FIG.

  In the next step S113, blood pressure is estimated by the characteristic estimation unit 122. The blood pressure estimation process will be described in detail later using the flowchart of FIG.

  When the process of step S113 ends, the control target value detection unit 102 determines whether or not the detected cuff pressure Pc indicates a cuff pressure equal to or higher than the predetermined value PC1 (step S122). If it is determined that the cuff pressure Pc is not instructed to exceed the cuff pressure of the predetermined value PC1 (NO in step S122), the process returns to step S102. On the other hand, if it is determined that cuff pressure Pc indicates a cuff pressure equal to or higher than predetermined value PC1 (YES in step S122), the process proceeds to step S124.

  In step S124, similarly to FIG. 6, in step S124, the maximum value of the arterial volume signal PGdc stored in the region E2 of FIG. 18 is set as the initial control target value V0, and the maximum value of the cuff pressure Pc is set as the initial cuff pressure MBP. And the maximum amplitude value of the arterial volume signal PGdc is detected as the control error maximum value Δerr-max, read from the region E2, and stored in the region E0 in FIG. As a result, the determined initial control target value V0, initial cuff pressure MBP, and control error maximum value Δerr-max are detected.

  When the process of step S124 is completed, the volume change erasure rate PDR and the optimum servo gain AG are calculated. First, the characteristic estimation unit 122 detects whether or not the flag FR indicates 1 (step S136). If it is detected that the flag FR is 0 (NO in step S136), the process of FIG. 16 is exited and the process is returned to the main routine.

  If the flag FR = 1 is detected (YES in step S136), the slope of the pressure-volume curve is calculated from the arterial volume change (ΔPGdc) and the pulse pressure (step S138), and the relational expression obtained from the clinical data The volume change elimination rate PDR is calculated based on (FIG. 14) and the slope of the pressure-volume characteristic curve (step S140).

  More specifically, in step S138, the characteristic estimation unit 122 calculates the slope of the characteristic curve as the elastic characteristic of the artery. The slope of the characteristic curve is calculated based on the systolic blood pressure and the systolic blood pressure estimated in step S200 and the volume values PGdc-DIA and PGdc-SYS determined in steps S204 and S208, respectively. More specifically, it is calculated by the following equation.

Slope of characteristic curve = {(PGdc-SYS) − (PGdc-DIA)} / (estimated systolic blood pressure−estimated diastolic blood pressure)
Next, the erasure rate detection unit 121 calculates an erasure rate target value PDR (step S140). Specifically, the erasure rate target value PDR is calculated by substituting the value of the slope of the characteristic curve calculated in step S138 into the linear function equation represented by equation 700 in FIG. The calculated erasure rate target value PDR is temporarily stored in the area E0 in FIG. When this process ends, the process moves to a step S144.

  In step S144, the gain determination unit 120 detects the systolic blood pressure and the diastolic blood pressure according to the procedure described with reference to FIG. 10 as in the first embodiment, and calculates the pulse pressure PPc1 based on both detected blood pressures (step S144). Then, using the calculated pulse pressure PPc1, the erasure rate target value PDR read from the region E0, and the maximum control error value Δerr-max, the optimum servo gain AG is calculated according to (Equation 3) and stored in the region E0. When the optimum servo gain AG is determined, the value of the flag FL is set to 1 (step S146). When the optimum servo gain AG is thus detected, the process is returned to the main routine.

  Here, the flow of blood pressure estimation processing (step S113) will be described. FIG. 17 is a flowchart showing blood pressure estimation processing.

  Referring to FIG. 17, first, characteristic estimation unit 122 executes a blood pressure estimation process (step S200). Here, a specific example of the blood pressure estimation process in the second embodiment will be described with reference to FIG. Referring to FIG. 10, characteristic estimation unit 122 calculates threshold values TH-DIA and TH-SYS when maximum value MAX of the amplitude of arterial volume signal PGdc is detected. Then, on the side where the cuff pressure is lower than the cuff pressure MEAN (mean blood pressure) at the time point T0 when the maximum value MAX is detected, the cuff pressure at the point where the threshold TH-DIA and the envelope 600 intersect is estimated as the minimum blood pressure. . Further, on the side where the cuff pressure is higher than the cuff pressure MEAN, the cuff pressure at the point where the threshold TH-SYS and the envelope 600 intersect is estimated as the maximum blood pressure. When the diastolic blood pressure is estimated, for example, the characteristic estimating unit 122 updates a flag (hereinafter referred to as “DIA flag”) indicating whether or not the diastolic blood pressure has been estimated from 0 to 1. When the systolic blood pressure is estimated, for example, a flag indicating whether or not the systolic blood pressure has been estimated (hereinafter referred to as “SYS flag”) is updated from 0 to 1.

  The characteristic estimation unit 122 determines whether or not the minimum blood pressure has been estimated (step S202). Specifically, it is determined whether or not the value of the DIA flag indicates 1. If it is determined that the minimum blood pressure has been estimated (YES in step S202), the value of the arterial volume signal PGdc at that time is determined as the volume value “PGdc-DIA” at the time of minimum blood pressure estimation (step S204). The determined volume value PGdc_DIA is temporarily recorded in the internal memory. When this process ends, the process proceeds to step S206.

  If it is determined in step S202 that the minimum blood pressure has not been estimated (NO in step S202), the process proceeds to step S206.

  In step S206, the characteristic estimation unit 122 determines whether or not the systolic blood pressure has been estimated. Specifically, it is determined whether or not the value of the SYS flag indicates 1. If it is determined that the maximum blood pressure has been estimated (YES in step S206), the value of the arterial volume signal PGdc at that time is determined as the volume value “PGdc-SYS” at the time of maximum blood pressure estimation (step S208). The determined volume value PGdc-SYS is temporarily recorded in the internal memory. When this process ends, the process proceeds to step S210.

  If it is determined in step S206 that the minimum blood pressure has not been estimated (NO in step S206), the process proceeds to step S210.

  In step S210, the characteristic estimation unit 122 determines whether the volume value PGdc-DIA and the volume value PGdc-SYS have been determined. If it is determined that it has been determined (YES in step S210), the value of the flag FR is set to 1 in step S212. On the other hand, if it is determined that it has not been determined (NO in step S210), the process returns to the routine of FIG. 16 without updating the value of the flag FR.

  Referring to FIG. 15 again, when the control target value detection process as described above is completed, cuff pressure setting unit 104 controls valve drive circuit 54 to set cuff pressure Pc to the initial cuff pressure (step S10). ). Referring to FIG. 5, cuff pressure setting unit 104 stops valve drive circuit 54 at time T1 when cuff pressure Pc is set to the initial cuff pressure.

  Thus, when the cuff pressure is set to the initial cuff pressure, the amplitude indicated by the arterial volume change signal PGac is maximized.

  When the cuff pressure is set to the initial cuff pressure, the servo gain determination process (step S26) is performed until the optimum servo gain AG (specific servo gain) for servo control is determined (NO in step S12).

  If the optimal servo gain AG has been determined by the gain determination unit 120 (YES in step S12), servo control is performed by the servo control unit 109 using the optimal servo gain AG read from the region E0, and the arterial volume constant control is performed. Is executed (step S14).

  In parallel with such constant arterial volume control, the blood pressure determination unit 116 executes blood pressure calculation and blood pressure determination processing (steps S16 and S18), as in the first embodiment. The measured blood pressure data is stored in the area E3 of the flash memory 43 (step S20). When the process of step S20 ends, the process proceeds to step S22.

  Subsequently, when it is determined in step S22 that the stop switch 41C has been operated (YES in step S22), the series of blood pressure measurement processes ends.

  As described above, according to the second embodiment, the optimum servo gain AG can be used instead of the initial gain value G-init of the first embodiment, so that the process for determining the optimum gain is not necessary. Therefore, the time for determining the optimum servo gain at time T1-T2 in FIG. 9 can be omitted, and the process can immediately shift to blood pressure measurement.

  In the second embodiment, since the servo gain for blood pressure measurement is determined according to the elastic characteristic (hardness) of the artery of the measurement subject, the blood pressure can be measured (determined) with high accuracy. . In addition, since the elastic characteristics of the artery are estimated based on the pulse pressure of the subject's artery and the amount of change in the arterial volume between the pulse pressures, the control target value is an essential process in blood pressure measurement by the volume compensation method. It can be estimated in the detection process. As a result, the optimum servo gain can be determined for each person to be measured without extending the time required for a series of blood pressure measurement processes.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is an external appearance perspective view of the electronic blood pressure monitor which concerns on each embodiment of this invention. It is a figure showing the concept which controls the cuff pressure for the blood pressure measurement in the electronic blood pressure monitor which concerns on each embodiment of this invention. It is a block diagram showing the hardware constitutions of the electronic blood pressure monitor which concerns on each embodiment of this invention. It is a figure which shows typically the relationship between the control pulse pressure which concerns on Embodiment 1 of this invention, a control error, and a servo gain. It is a figure explaining the example of storing of the data which concerns on Embodiment 1 of this invention. It is a functional block diagram which shows the function structure of the electronic blood pressure monitor which concerns on Embodiment 1 of this invention. It is a flowchart which shows the blood-pressure measurement process in Embodiment 1 of this invention. It is a flowchart which shows the control target value and initial gain detection process in Embodiment 1 of this invention. It is a figure for demonstrating the blood-pressure measurement process of Embodiment 1 of this invention. It is a figure for demonstrating the procedure of the blood pressure estimation which concerns on Embodiment 1 of this invention. It is a flowchart of the servo gain determination process which concerns on Embodiment 1 of this invention. It is a functional block diagram which shows the function structure of the electronic blood pressure monitor which concerns on Embodiment 2 of this invention. It is a figure which shows the pressure-volume characteristic of the blood vessel which concerns on this invention. It is a figure which shows the correlation with the inclination of the characteristic curve of the blood vessel based on this invention, and a volume change elimination rate. It is a flowchart which shows the blood-pressure measurement process in Embodiment 2 of this invention. It is a flowchart which shows the control target value and optimal gain detection process in Embodiment 2 of this invention. It is a flowchart of the blood-pressure estimation process which concerns on Embodiment 2 of this invention. It is a figure explaining the example of storage of the data which concerns on Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electronic sphygmomanometer, 102 Control target value detection part, 104 Cuff pressure setting part, 106,109 Servo control part, 108 Blood pressure determination part, 109,120 Gain determination part, 111 Volume change erasure rate calculation part, 112 Gain update part, 113 control pulse pressure detection unit, 121 erasure rate detection unit, 122 characteristic estimation unit.

Claims (9)

An electronic sphygmomanometer for measuring blood pressure according to a volume compensation method,
A cuff attached to a blood pressure measurement site;
Pressure detecting means for detecting a cuff pressure representing the pressure in the cuff;
A volume detecting means for detecting an arterial volume signal indicating the volume of the artery of the measurement site in the process of applying the cuff pressure to the cuff;
Cuff pressure adjusting means for adjusting the cuff pressure by pressurization and decompression;
Control means,
The control means includes
First control means for controlling the cuff pressure adjusting means to set the cuff pressure to an initial cuff pressure representing a specific pressure value;
Servo control means for servo-controlling the cuff pressure adjusting means using a servo gain so that the volume of the artery becomes constant after setting the cuff pressure to the initial cuff pressure;
Servo gain determination means for determining a specific servo gain for blood pressure measurement while sequentially updating the servo gain by adding an initial gain when servo control by the servo control means is performed. Including
The amplitude of the arterial volume signal detected when cuff pressure is set to the initial cuff pressure is maximum;
The electronic sphygmomanometer, wherein the initial gain is calculated by dividing the estimated value of the arterial pulse pressure by the maximum amplitude value detected for the arterial volume signal. The control means includes
Initial gain detecting means for detecting the initial gain;
The initial gain detection means includes
The electronic blood pressure according to claim 1, wherein the pulse pressure is estimated by calculating the systolic blood pressure and the diastolic blood pressure based on the cuff pressure detected by the pressure detecting means in the process of detecting the initial cuff pressure. Total. The servo gain determining means includes
In the process of performing servo control while updating the servo gain value, the updated servo gain is set to the specific servo when the amount of change in the arterial volume detected by the volume detecting means converges to a minimum value. The electronic sphygmomanometer according to claim 1 or 2, wherein a gain is determined.   In the process of performing servo control while updating the servo gain value, the cuff pressure detected by the pressure detecting means when the change amount of the arterial volume detected by the volume detecting means converges to a minimum value. The electronic sphygmomanometer according to claim 1, wherein the blood pressure is detected as blood pressure. The servo gain determining means includes
When the servo control by the servo control means is performed, the amplitude of the arterial volume signal detected by the volume detection means and the cuff pressure are set to the initial cuff pressure for each pulse wave An amplitude ratio detecting means for detecting a ratio of the amplitude of the arterial volume signal detected in
5. When detecting that the ratio detected by the amplitude ratio detecting means is smaller than a predetermined value, it is detected that the amount of change in the volume of the artery has converged to a minimum value. The electronic blood pressure monitor according to any one of the above. An electronic sphygmomanometer for measuring blood pressure according to a volume compensation method,
A cuff attached to a blood pressure measurement site;
Pressure detecting means for detecting a cuff pressure representing the pressure in the cuff;
A volume detection means provided on the cuff for detecting an arterial volume signal indicating the volume of the artery of the measurement site;
Cuff pressure adjusting means for adjusting the cuff pressure by pressurization and decompression;
Control means,
The control means includes
Setting means for setting the cuff pressure to an initial cuff pressure representing a specific pressure value;
Servo control means for servo-controlling the cuff pressure adjusting means so that the volume of the artery is constant based on a specific servo gain for blood pressure measurement after setting the cuff pressure to the initial cuff pressure;
Determination processing means for performing processing for determining the specific servo gain,
The determination processing means includes:
The amplitude pulse pressure for detecting the maximum amplitude of the arterial volume signal and the pulse pressure of the artery in the process of increasing the cuff pressure to a predetermined value by the cuff pressure adjusting means or the process of reducing the cuff pressure from the predetermined value Detection means;
A characteristic estimation means for estimating an elastic characteristic of the artery based on a relationship between the detected pulse pressure of the artery and a change in volume between the pulse pressures of the artery;
Erasing for calculating the volume change elimination rate for the artery based on the elastic characteristics of the artery estimated by the characteristic estimation means and a predetermined correlation equation indicating the relationship between the elastic characteristics and the volume change elimination rate A rate calculating means,
An electronic sphygmomanometer that determines the specific servo gain by dividing the detected pulse pressure by a value obtained by multiplying the detected maximum amplitude value of the arterial volume signal by the calculated volume change elimination rate . The determination processing means detects, as the initial cuff pressure, the cuff pressure at the time when the amplitude of the arterial volume signal becomes maximum in the process of increasing the cuff pressure to a predetermined value or reducing the cuff pressure from the predetermined value. Detection processing means for performing processing for
In parallel with the processing by the detection processing means, blood pressure estimation means for estimating the minimum blood pressure and the maximum blood pressure,
The characteristic estimation means divides the difference in the value of the arterial volume signal between the time points when the minimum blood pressure and the maximum blood pressure are detected by dividing the difference between the maximum blood pressure and the minimum blood pressure, thereby The electronic sphygmomanometer according to claim 6, wherein the elastic property is estimated. The control means includes
Blood pressure determination for receiving a detection signal from the pressure detection means and determining a cuff pressure corresponding to the detection signal as a blood pressure when the servo control means performs servo control with the specific servo gain. Further comprising means,
The electronic sphygmomanometer according to claim 6 or 7, further comprising storage means for storing the blood pressure determined by the blood pressure determination means.   The electronic sphygmomanometer according to claim 7 or 8, wherein the detection processing means further derives the initial cuff pressure based on a detection signal from the pressure detection means and the arterial volume signal.

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