JP5083037B2 - 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).

  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 control amount is the sum of the deviation between the current arterial volume signal and the previously calculated control target value, the integral of the deviation, and the derivative of the deviation multiplied by a constant value (hereinafter referred to as servo gain). Is output as 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 to set the cuff pressure to an initial cuff pressure representing a specific pressure value, and after setting the cuff pressure to the initial cuff pressure, When the servo control by the servo control means and the servo control means is performed, the cuff pressure adjusting means is controlled for each pulse wave. Servo gain determining means for updating the servo gain using an amount corresponding to the difference between the arterial volume indicated by the arterial volume signal detected by the volume detecting means and the target value for servo control.

  The amplitude of the arterial volume signal detected when the cuff pressure is set to the initial cuff pressure is the maximum, and the target value indicates the arterial volume when the maximum amplitude is detected for the arterial volume signal.

  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. And amplitude ratio detecting means for detecting a ratio of the amplitude of the arterial volume signal detected when set to. Then, an increase amount of the servo gain is determined based on the ratio detected by the amplitude ratio detection means, and the current servo gain value is updated using the determined increase amount.

  Preferably, in the process of performing servo control while updating the servo gain value, the cuff pressure detected by the pressure detection means when the change amount of the arterial volume detected by the volume detection means converges to the minimum value. Detect as.

  Preferably, when it is detected that the ratio detected by the amplitude ratio detection means is smaller than a predetermined value, it is detected that the amount of change in the arterial volume has converged to the minimum value.

  Preferably, the servo gain determining means detects the arterial volume indicated by the arterial volume signal detected by the volume detecting means and the maximum amplitude of the arterial volume signal when the control by the servo control means is being performed. The integrated value obtained by integrating the difference from the arterial volume for one pulse wave is detected, and the ratio between the detected integrated value and the integrated value detected when the cuff pressure is set to the initial cuff pressure is calculated. Based on the integration ratio detection means to be detected and the ratio detected by the integration ratio detection means, an increase amount of the servo gain is determined, and the current servo gain value is updated using the determined increase amount.

  Preferably, in the process of performing servo control while updating the servo gain value, the cuff pressure detected by the pressure detection means when the change amount of the arterial volume detected by the volume detection means converges to the minimum value. Detect as.

  Preferably, when it is detected that the ratio detected by the integration ratio detecting means is smaller than a predetermined value, it is detected that the amount of change in the arterial volume has converged to the minimum value.

  According to the present invention, in the servo gain adjustment processing in the configuration of the electronic sphygmomanometer by the volume compensation method, the amount corresponding to the magnitude of the control error for each pulse wave by servo control is used, that is, the pulse wave beat Each time, the servo gain is updated using an amount corresponding to the difference between the arterial volume indicated by the arterial volume signal detected by the volume detecting means and the servo control target value.

  As a result, the update speed for increasing the servo gain or the like is changed in accordance with the magnitude of the control error, so that the time required for servo gain adjustment can be shortened while maintaining control stability. As a result, the servo gain for blood pressure measurement according to the volume compensation method can be quickly determined.

  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 also converges, and the amount of arterial volume change 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 point at which the amplitude of the arterial volume change signal is minimized in the process of performing servo control while increasing the servo gain, so that no load is applied to the artery for each individual. 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.

  The electronic sphygmomanometer according to the present embodiment continuously measures blood pressure by the volume compensation method. 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 sphygmomanometer 1 according to an 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 portions of the upper limbs and lower limbs excluding their respective fingers. 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 according to the present 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 the 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 the present embodiment, 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 present invention 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 the 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 non-volatile memory (for example, a flash memory) 43 for storing measured blood pressure data according to FIG. 8 to be described later, and for supplying power to each unit via the CPU 100 A power supply 44 and a timer 45 that measures the current time and outputs the time measurement data to the CPU 100 are included. 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 nonvolatile switch A memory switch 41D for receiving an instruction to read information such as blood pressure recorded in the sex memory 43, and an ID switch 41E operated to input ID (Identifier) information for identifying the person to be measured .

  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.

  FIG. 5 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. 5, CPU 100 includes a drive control unit 101 that performs control for setting the cuff pressure to an initial cuff pressure, a servo control unit 106 that performs feedback control for continuously measuring blood pressure, and blood pressure. A determination unit 108 and a servo gain determination unit 109 for determining a servo gain are included. Note that FIG. 5 shows only peripheral hardware that directly transmits and receives signals to and from these units included in the CPU 100 for the sake of simplicity.

  The drive control unit 101 includes a control target value detection unit 102 for detecting a control target value for servo control, and a cuff pressure setting unit 104 for setting a cuff pressure.

  The control target value detection unit 102 performs a process of deriving an 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 inputs an arterial volume change signal representing a change (amplitude) for each beat of the arterial volume signal output from the arterial volume detection circuit 74.

  The control target value detection unit 102 controls the drive of the pump drive circuit 53 until the cuff pressure reaches a predetermined value. Until the cuff pressure reaches a predetermined value, the (temporary) maximum value of the arterial volume change signal is detected, the signal from the oscillation circuit 33 is input, and the input signal is converted into a pressure value. Then, the detected temporary maximum value and the cuff pressure at that time are recorded in a predetermined area of the nonvolatile memory 43. The provisional maximum value and the cuff pressure may be overwritten and recorded each time the recorded (provisional) maximum value is updated.

  Finally, the value recorded as the maximum value of the arterial volume change signal is determined as the control target value in the servo control. Further, the cuff pressure when the arterial volume change signal is the maximum value (reference cuff pressure at the time of servo control) is determined as the initial cuff pressure.

  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 determined initial cuff pressure and control target value are output to the cuff pressure setting unit 104.

  In the process of reducing the cuff pressure from a predetermined value, the reference cuff pressure as the initial cuff pressure may be derived.

  The cuff pressure setting unit 104 inputs a signal from the oscillation circuit 33 and drives the valve drive circuit 54 until the cuff pressure reaches the initial cuff pressure. As a result, the valve 52 discharges air, 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 performs control according to 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 is minimized (preferably zero). Based on the quantity, the pump drive circuit 53 or the valve drive circuit 54 is controlled. That is, the pump drive circuit 53 or the valve drive circuit 54 controls the operation of the pump 51 or the opening / closing of the valve 52 so that the value (amplitude) of the arterial volume change signal is not more 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 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 nonvolatile memory 43 in time series.

  The servo gain determination unit 109 includes an amplitude value calculation unit 110, a volume change erasure rate calculation unit 111, and a gain increase amount determination unit 112 as shown in FIG. 6 in order to determine an optimum servo gain. 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.

Next, the operation of the electronic sphygmomanometer 1 in the present embodiment will be described.
FIG. 7 is a flowchart showing blood pressure measurement processing in the 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 the measurement site as shown in FIG. 3 when measuring blood pressure.

  Referring to FIG. 7, 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, a predetermined area of the memory unit 42 is initialized, the air in the air bladder 21 is exhausted, and the pressure sensor 32 is corrected. At this time, the value of the flag FL for instructing whether or not the servo gain for servo control 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 S <b> 8, the control target value detection unit 102 performs processing for detecting an initial cuff pressure and a control target value. The initial cuff pressure and the control target value are detected as follows.

  While gradually increasing the cuff pressure, the arterial volume signal (DC component of the volume pulse wave signal) PGdc and the arterial volume change signal (AC component of the volume pulse wave signal) PGac at that time are 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 a volume pulse wave signal indicating a change in arterial volume is input from the arterial volume sensor 70, the input signal is input to the arterial volume signal PGdc of the DC component of the volume pulse wave signal and the arterial volume change of the AC component by the HPF circuit. Separate and output to signal PGac. For example, assuming that the filter constant is 1 Hz, a signal of 1 Hz or less is derived as a DC component, and a signal exceeding 1 Hz is derived as an AC component. The control target value detection unit 102 inputs the arterial volume signal PGdc and the arterial volume change signal PGac.

  The control target value detection unit 102 detects whether or not the value of the arterial volume change signal PGac currently detected is the maximum, and the value of the arterial volume signal PGac, the value of the arterial volume signal PGdc, the cuff pressure, Are stored in a predetermined memory area. This operation is repeated until the cuff pressure reaches a predetermined pressure. This predetermined pressure is specified by cuff pressure data PC1 (for example, 200 mmHg) read from nonvolatile memory 43.

  The value of the arterial volume signal PGdc associated with the maximum value among the values of the arterial volume change signal PGac stored in the predetermined memory area when detecting that the cuff pressure has reached the predetermined pressure is set as the control target value. Then, the stored cuff pressure is determined as the control initial cuff pressure. Thereby, the control target zone and the initial cuff pressure are detected.

  The detection of the control target value and the initial cuff pressure will be described in detail with reference to FIGS.

  FIG. 8 is a flowchart showing the control target value and the initial cuff pressure detection process in the embodiment of the present invention. FIG. 9 is a diagram for explaining blood pressure measurement processing according to the embodiment 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 the maximum value and cuff pressure value of arterial volume change signal PGac stored in a predetermined area of memory unit 42 (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 finally determined as the maximum value is referred to as “temporary volume maximum value”.

Next, the pump drive circuit 53 is controlled to increase the cuff pressure (step S104).
At the stage of increasing the cuff pressure, 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 (step S106).

  The control target value detection unit 102 compares the value of the arterial volume change signal PGac with the value of the temporary volume maximum arterial volume change signal PGac read from the memory unit 42, and based on the comparison result, the value of the arterial volume change signal PGac Is greater than or equal to the provisional maximum value (step S108). When it is detected that the value of arterial volume change signal PGac is equal to or greater than the temporary volume maximum value (YES in step S108), the process proceeds to step S110. 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 S108), the process proceeds to step S112.

  In step S110, the control target value detection unit 102 updates the temporary volume maximum value in the memory unit 42 using the value of the arterial volume change signal PGac, and the cuff pressure associated with the temporary volume maximum value in the memory unit 42. Is overwritten by the cuff pressure Pc detected at that time. When this process ends, the process moves to a step S112.

  In step S112, 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. 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 S112), the process returns to step S104. On the other hand, when it is detected that the cuff pressure Pc indicates the cuff pressure equal to or higher than the predetermined value PC1 (YES in step S112), the process proceeds to step S114. Such loop processing of steps S104 to S112 is performed in the period up to time T0 in FIG.

  In step S114, the control target value detection unit 102 determines the temporary volume maximum value finally recorded in step S110 as the maximum value, and the value of the cuff pressure Pc detected at time T0 when the maximum value is detected. Is determined as the initial cuff pressure (the cuff pressure indicated by the symbol MBP in FIG. 9). The control target value detection unit 102 further determines the value of the arterial volume signal PGdc stored in association with the arterial volume change signal PGac at time T0 as the control target value V0. The procedure for detecting the control target value V0 is in accordance with Patent Document 1.

When the process of step S114 ends, the process is returned to the main routine.
Referring to FIG. 7 again, when the control target value and initial cuff pressure detection processing as described above is completed, the cuff pressure setting unit 104 controls the valve drive circuit 54 to change the cuff pressure Pc to the initial cuff pressure. Set (step S10). Referring to FIG. 9, the cuff pressure setting unit 104 stops the valve drive circuit 54 at time T <b> 1 when the 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 period until the optimum servo gain for servo control is determined (NO in step S12), that is, in the period from time T1 to T2 in FIG. Servo gain determination processing (step S26) is performed by the determination unit 109. 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 has been determined (YES in step S12), and otherwise (NO in step S12), it is not determined. And the process proceeds to the servo gain determination process (step S26). The procedure for determining the servo gain will be described later.

  If the optimum servo gain has been determined (YES in step S12), arterial volume constant control is executed by servo control by the servo control unit 106 using the determined optimum 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 controls the pump drive circuit 53 and the valve drive circuit 54 according to the servo gain. A control signal based on 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, the optimum servo gain determination process is performed in the period from time T1 to T2, and it is shown that the 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 nonvolatile 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 beat 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 detected maximum value corresponds to the maximum blood pressure (systolic blood pressure), and the minimum value corresponds to the minimum blood pressure (diastolic blood pressure).

  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 nonvolatile 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.

  In the present embodiment, servo gain determination processing (step S26) is performed in order to quickly start blood pressure measurement. In the servo gain determination process, it is necessary to appropriately set the servo gain increase rate (increase amount per unit time) to shorten the time required for determining the servo gain. To shorten the time, it is desirable to increase it quickly. However, if the increasing speed is too large, it becomes difficult to detect the control limit point (that is, the optimum servo gain), and the servo gain value becomes larger than necessary, so that abnormal oscillation occurs in the control signal and servo control becomes impossible. Therefore, it is necessary to appropriately set the servo gain increasing speed. The appropriate increase speed is influenced by the value of the detected arterial volume change signal PGac or the amount of decrease in the value of the arterial volume change signal PGac when servo control is performed, and cannot be generally determined.

Therefore, in the present embodiment, the servo gain increasing speed is adjusted by paying attention to the control error according to the flowchart of FIG. Here, the control error refers to a difference between the control target value V0 and the detected value of the arterial volume signal PGdc. In the servo gain determination process of FIG. 10, when the servo gain is small and the control error is large, the servo gain is increased rapidly by increasing the servo gain increase speed, and the servo gain is increased and the control error is reduced. As the time goes, the increase rate of servo gain is reduced. This shortens the time required to determine the optimum servo gain while maintaining control stability. In the servo gain determination process of FIG. 10, in the process of increasing the servo gain according to the control error, the volume is increased. Servo gain obtained when the change erasure rate is detected as less than a predetermined volume change erasure rate target value (hereinafter referred to as the erasure rate target value) is optimal for blood pressure measurement according to the volume compensation method. Determine the servo gain. Therefore, according to the present embodiment, it is possible to quickly determine the optimum servo gain as compared with the conventional configuration in which the optimum servo gain is detected by increasing the servo gain at a constant value.

  The servo gain determination process according to the present embodiment will be described with reference to FIG. It is assumed that the servo gain is set to a small value in advance so as to avoid the abnormal oscillation described above.

  In operation, first, the amplitude value calculation unit 110 calculates an amplitude value for each beat based on the detected arterial volume change signal PGac (step ST3).

  Next, the volume change elimination rate calculation unit 111 sets the volume change elimination rate at this time (the amplitude value / cuff pressure of the current arterial volume change signal PGac to the initial cuff pressure) for each beat of the arterial volume change signal PGac. The amplitude value of the arterial volume change signal PGac detected at this time is calculated and stored in the nonvolatile memory 43 (step ST5). The current amplitude value of the arterial volume change signal PGac is the value calculated in step ST3. Further, 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 servo gain increase amount calculation unit 112 calculates a value obtained by multiplying the volume change erasure rate read from the nonvolatile memory 43 by a predetermined coefficient as a servo gain increase amount (hereinafter referred to as a servo gain increase amount). (Step ST7). The calculated servo gain increase amount data is stored in the nonvolatile memory 43.

  The servo control unit 106 updates the current servo gain by adding the servo gain increase amount read from the nonvolatile memory 43 (step ST9). Thus, the servo gain can be increased according to the value of the volume change erasure rate.

  Subsequently, the servo control unit 106 performs servo control using the updated servo gain so that the difference between the value of the arterial volume signal PGdc and the control target value V0 is minimized (step ST11). While the servo control is performed, the amplitude value calculation unit 110 calculates an amplitude value for each beat based on the detected arterial volume change signal PGac, and the volume change erasure rate calculation unit 111 calculates the calculated value. Using the amplitude value, the volume change erasure rate is calculated as described above.

  Subsequently, the servo gain determination unit 109 compares the volume change erasure rate calculated in step ST13 with the target value TH1 of the volume change erasure rate, and based on the comparison result, the calculated volume change erasure rate is the target value TH1. Is continuously detected (NO in step ST41), it is detected that the arterial volume change signal PGac has converged to the minimum value, and the servo gain to be used in the blood pressure calculation process is changed to the servo gain at this time. Determine (step ST43). The determined servo gain is stored in the nonvolatile memory 43. The servo control unit 106 reads the servo gain from the nonvolatile memory 43 and performs servo control in the blood pressure calculation process based on the read servo gain.

  Then, the servo gain determination unit 109 sets 1 to the flag FL to indicate that the servo gain for blood pressure measurement has been determined (step ST45).

  With the above procedure, the servo gain determination (step S26) processing according to the present embodiment ends.

  The above-described threshold value TH1 is a value determined in advance by sampling from a large number of subjects.

  In this way, in the process in which the servo control is performed while the servo control unit 106 increases the servo gain by an amount according to the detected value of the volume change erasure rate, the volume change erasure rate shown in synchronization with the heartbeat is the threshold value TH1. It is possible to detect that the amount of change in the arterial volume has converged to the minimum value.

  FIG. 11 schematically shows the change of the arterial volume change signal PGac and the change of the servo gain in the period from the start of the servo gain determination process to the convergence of the amplitude of the arterial volume change signal PGac along the same time axis. . FIG. 11 schematically shows the relationship between the increase rate of the servo gain and the amplitude value of the arterial volume change signal PGac in the period from time T1 to time T2 in FIG. 9, and the scale of the vertical axis is different from that in FIG. Yes.

  Here, in order to show the change of the servo gain in an easy-to-understand manner, it is assumed that the servo gain at the time of starting the servo gain determination process is zero. As shown in the figure, the servo gain increase rate is fast at the start of processing with a relatively large volume change erasure rate, but the amplitude value of the arterial volume change signal PGac is gradually converging during the subsequent servo control period. Therefore, the volume change erasure rate is also gradually reduced. Therefore, the increase rate of the servo gain gradually decreases during this servo control period.

(Other calculation procedures for servo gain increase)
The procedure for calculating the servo gain increase amount in step ST7 described above is not limited to that described above, and may be calculated as follows. That is, the gain determination unit 109 may use a control error signal Err for each beat calculated by an integral value calculation unit (not shown) included in the gain determination unit 109, instead of the amplitude value of the arterial volume change signal PGac. . Here, the control error signal Err is calculated by squaring the difference between the control target value V0 and the value of the arterial volume signal PGdc, or a value obtained by integrating the absolute value of the difference for one pulse wave. In this case, the integral ratio detection means (not shown) included in the gain determination unit 109 detects (when the current control error signal Err value / cuff pressure is set to the initial cuff pressure) as the volume change elimination rate. Value of the control error signal Err). The gain determination unit 109 can detect that the amount of change in the arterial volume has converged when the calculated volume change elimination rate becomes equal to or less than the threshold value TH1.

  Here, the data structure of each measurement data stored in the nonvolatile memory 43 by the above blood pressure measurement process will be described.

  FIG. 4 is a diagram showing a data structure of measurement data stored in the nonvolatile memory 43 according to the embodiment of the present invention.

  Referring to FIG. 4, nonvolatile memory 43 includes an area E1, a work area E2, and a measurement data storage area E3. The area E1 stores the control target value and the cuff pressure data PC1 that is referred to for detecting the initial cuff pressure, and the threshold value TH1 that is referred to for determining the servo gain.

  A plurality of measurement data 80 is stored in the area E3. 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 input by operating the ID switch 41E during blood pressure measurement. In the field 83, data 831 measured by the timer 45 such as the measurement start date and time and the measurement period of the measurement data and the measured blood pressure data 832 are stored in association with each other.

  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.

1 is an external perspective view of an electronic blood pressure monitor according to an embodiment of the present 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 embodiment of this invention. It is a block diagram showing the hardware constitutions of the electronic blood pressure monitor which concerns on embodiment of this invention. It is a figure explaining the example of storage of the measurement data which concerns on embodiment of this invention. It is a functional block diagram which shows the function structure of the electronic blood pressure monitor which concerns on embodiment of this invention. It is a functional block diagram which shows the function structure of the servo gain determination part which concerns on embodiment of this invention. It is a flowchart which shows the blood-pressure measurement process in embodiment of this invention. It is a flowchart which shows the control target value and initial cuff pressure detection process in embodiment of this invention. It is a figure for demonstrating the blood-pressure measurement process of embodiment of this invention. It is a flowchart of the servo gain determination process which concerns on embodiment of this invention. It is a figure explaining the servo gain increase speed which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electronic sphygmomanometer, 102 Control target value detection part, 104 Cuff pressure setting part, 106 Servo control part, 108 Blood pressure determination part, 109 Gain determination part, 110 Amplitude value calculation part, 111 Volume change erasure rate calculation part, 112 Gain increase A quantity calculator.

Claims (6)

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;
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 Amplitude ratio detecting means for detecting a ratio of the amplitude of the arterial volume signal detected in
Means for determining an increase amount of the servo gain based on the ratio detected by the amplitude ratio detection means, and updating a current value of the servo gain using the determined increase amount;
The electronic sphygmomanometer , wherein the amplitude of the arterial volume signal detected when the cuff pressure is set to the initial cuff pressure is maximum . 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 detected as blood pressure, an electronic sphygmomanometer according to claim 1. The ratio detected by the amplitude ratio detecting means, when detecting that becomes smaller than a predetermined value, detects that the amount of change in volume of the artery is converged to a minimum value, according to claim 2 Electronic blood pressure monitor. 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;
When the control by the servo control means is performed, the arterial volume indicated by the arterial volume signal detected by the volume detecting means and the arterial volume when the maximum amplitude is detected for the arterial volume signal An integrated value obtained by integrating the difference for one beat of the pulse wave is detected, and a ratio between the detected integrated value and the integrated value detected when the cuff pressure is set to the initial cuff pressure is detected. Integration ratio detection means for
Determining an increase amount of the servo gain based on the ratio detected by the integration ratio detection means, and updating a current value of the servo gain using the determined increase amount;
The electronic sphygmomanometer, wherein the amplitude of the arterial volume signal detected when the cuff pressure is set to the initial cuff pressure is maximum . 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 blood pressure monitor according to claim 4 , wherein the blood pressure is detected as blood pressure. The ratio detected by the integral ratio detecting means, when detecting that becomes smaller than a predetermined value, detects that the amount of change in volume of the artery is converged to a minimum value, according to claim 5 Electronic blood pressure monitor.

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