JP2014014556A - Electronic sphygmomanometer and sphygmomanometry method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control a pressure of a cuff fitted to a part to be measured in non-invasive measurement of a blood pressure per heartbeat according to a volume compensation method.SOLUTION: An electronic sphygmomanometer comprises a pressure adjustment part that has a plurality of pumps and is for adjusting a cuff pressure. An arterial volume detection part is provided to detect an arterial volume in a part to be measured and output it as an arterial volume signal. The cuff pressure is varied by operating the pressure adjustment part in a first capacity with the use of first-numbered pumps so that a direct current component of the arterial volume signal obtained at the maximum amplitude of a varied component of the arterial volume signal using a pulse wave is determined as a control target value for the arterial volume (S4). Then, a feedback control is made to control the cuff pressure by the pressure adjustment part so that the arterial volume signal matches the control target value (S8 to S11). In the cuff pressure control stage, the pressure adjustment part is operated in a second capacity that is higher than the first capacity by using second-numbered pumps in excess of the first-numbered pumps (S5 to S6).

Description

  The present invention relates to an electronic sphygmomanometer and a blood pressure measuring method, and more particularly to an electronic sphygmomanometer and a blood pressure measuring method for measuring blood pressure for each heartbeat in a non-invasive manner by volume compensation.

  For example, Patent Document 1 (Japanese Patent Publication No. 1-331370) discloses a blood pressure measurement method that performs blood pressure measurement for each heartbeat in a non-invasive manner by a volume compensation method. In this blood pressure measurement method, an arterial volume signal (referred to as “PGdc”) that changes due to the pulsation of the heart is detected by an arterial volume sensor such as a photoelectric sensor. Then, the volume signal PGdc indicates the arterial volume at a pressure at which the pre-detected arterial internal pressure (blood pressure) and the cuff internal pressure (cuff pressure) wound around the measurement site are balanced (the control target value V0). The cuff pressure is controlled so that it always matches. Since the cuff pressure during the control is always balanced with the blood pressure, the blood pressure for each heartbeat can be continuously measured by detecting the controlled cuff pressure.

  When controlling cuff pressure, a pump is generally used to pump and pressurize fluid (typically air) into the cuff, and a valve is used to drain the fluid from the cuff and depressurize it.

Japanese Patent Publication No. 1-331370

  As described above, in the blood pressure measurement using the volume compensation method, the intra-arterial pressure and the cuff pressure are balanced. For this reason, it is necessary to control the cuff pressure in accordance with the change in blood pressure from the diastolic blood pressure to the systolic blood pressure as illustrated in FIG. That is, it is necessary to generate a cuff pressure change corresponding to the pulse pressure (difference between systolic blood pressure and diastolic blood pressure) during the rise time (tr) of the blood pressure waveform (pulse wave waveform) of one heartbeat. It has been found that the rise time tr of the pulse wave waveform is about 0.08 s at the shortest. Further, as can be seen from the scatter diagram of FIG. 10 (circles in FIG. 10 correspond to the data of each person), the pulse pressure can reach up to about 150 mmHg in a person with high blood pressure and systolic blood pressure of 200 mmHg or more. It turns out.

  Here, the performance (flow rate per unit time) of the pump and the valve required for carrying out the cuff pressure control by the volume compensation method can be obtained as follows.

  FIG. 11 shows the characteristics of the cuff attached to the wrist, that is, the cuff pressure Pc (mmHg) and the flow rate required to change the cuff pressure by 1 mmHg (this is referred to as cuff-compliance comp (ml / mmHg)). Represents the relationship.

  First, a flow rate (referred to as ΔVair) necessary for changing the cuff pressure is calculated. Now, it is assumed that the required change in cuff pressure is 150 mmHg, which is the maximum value of the pulse pressure, the systolic blood pressure is 240 mmHg, and the diastolic blood pressure is 90 mmHg. The flow rate ΔVair required for the change in the cuff pressure is indicated by the hatched area in FIG. 11, and it can be seen that this cuff characteristic is about 19 ml. The shortest time required for the change of the cuff pressure is the pulse wave rise time tr = 0.08 s shown in FIG. Accordingly, the performance (capacity) required for the pump is obtained as ΔVair / tr = 316.7 ml / s (= 19 l / m) by dividing the required flow rate ΔVair by the shortest time tr of the cuff pressure change.

  This required performance can be said to be very high.

  In a diaphragm pump (a pump that discharges fluid by compressing and opening an air chamber called a diaphragm with a motor), which is a general pump structure, the capacity of the diaphragm is assumed to increase the flow rate per unit time. Is increased, ripple (pulsation) is generated in the discharged fluid. Since this ripple directly changes the cuff pressure, accurate blood pressure measurement becomes impossible.

  Accordingly, an object of the present invention is to provide an electronic sphygmomanometer and a blood pressure measurement method capable of appropriately controlling the pressure of a cuff attached to a measurement site when performing blood pressure measurement for each heartbeat noninvasively by the volume compensation method. Is to provide.

In order to solve the above problems, an electronic sphygmomanometer according to the present invention provides:
An electronic sphygmomanometer that non-invasively measures blood pressure for each heartbeat by volume compensation,
A cuff attached to the measurement site;
A plurality of pumps for supplying fluid to the cuff, and a pressure adjusting unit for adjusting the pressure of the cuff;
A pressure detector for detecting the pressure of the cuff;
An arterial volume detector that detects the volume of the artery of the measurement site and outputs it as an arterial volume signal;
The amplitude of the arterial volume change signal representing the change component due to the pulse wave of the arterial volume signal by changing the pressure of the cuff by operating the pressure adjusting unit with the first capacity using the first number of pumps. A first control unit that determines a direct current component of the arterial volume signal at the time of maximum amplitude when becomes a maximum as a control target value for the arterial volume;
A second control unit that performs feedback control after the control target value is determined and controls the pressure of the cuff by the pressure adjustment unit so that the arterial volume signal matches the control target value; ,
The second control unit controls the pressure of the cuff with a second capacity higher than the first capacity using a second number of pumps greater than the first number to control the pressure of the cuff. The part is operated.

  In this specification, the “measurement site” may be a site through which a body artery passes, such as a wrist or an upper arm.

  Examples of the feedback control include PID control, that is, control in which proportional control (Proportional Control), integral control (Integral Control), and differential control (Derivative Control) are combined to converge a control target to a control target value. .

  In the electronic sphygmomanometer according to the present invention, the first control unit changes the pressure of the cuff by operating the pressure adjusting unit with the first capacity using the first number of pumps. When the internal pressure of the artery and the pressure of the cuff are balanced, the amplitude of the arterial volume change signal representing the change component due to the pulse wave of the arterial volume signal is maximized. The first control unit determines the direct current component of the arterial volume signal at the maximum amplitude as the control target value for the arterial volume. After the control target value is determined, the second control unit performs feedback control, and controls the pressure of the cuff by the pressure adjusting unit so that the arterial volume signal coincides with the control target value. Here, the second control unit uses a second number of pumps larger than the first number to control the pressure of the cuff with a second capacity higher than the first capacity. The pressure adjusting unit is operated. Therefore, when performing blood pressure measurement for each heartbeat noninvasively by the volume compensation method, it is possible to satisfy the performance (flow rate per unit time) required to perform cuff pressure control. In addition, since the second number is plural, ripples (pulsations in the discharged fluid) generated randomly by each pump cancel each other and are averaged. Therefore, the fluctuation of the cuff pressure can be reduced as compared with the case where one large-capacity pump is used. Thereby, the pressure of the cuff attached to the measurement site can be appropriately controlled. As a result, in a situation where the internal pressure of the artery and the pressure of the cuff are always coincident, the blood pressure for each heartbeat can be continuously measured with high accuracy based on the cuff pressure signal output by the pressure detector. .

  In the electronic sphygmomanometer according to one embodiment, the second control unit sets the second number based on the blood pressure value of the person to be measured.

  Here, the “blood pressure value” of the measurement subject includes systolic blood pressure and diastolic blood pressure.

  As described above, the performance required for the pressure adjusting unit depends on the flow rate (ΔVair) required to change the cuff pressure. That is, it depends on a person's systolic blood pressure and diastolic blood pressure. Therefore, in the electronic sphygmomanometer according to this embodiment, the second control unit sets the second number according to the blood pressure value (including systolic blood pressure and diastolic blood pressure) of the measurement subject. It is characterized by. Therefore, a necessary and sufficient number can be set as the second number, and as a result, a necessary and sufficient capacity can be set as the second capability. Thereby, the precision (resolution) which controls the pressure of the said cuff can be raised, and the blood pressure for every heartbeat can be measured accurately.

  If an excessive capacity is set as the second capacity by using an excessive number as the second number, a flow rate unnecessary for blood pressure measurement is generated. For this reason, most of the pressure control amount (resolution) is used for supplying and discharging the unnecessary flow rate, and as a result, the resolution of the pressure control amount is lowered.

In one embodiment of the electronic blood pressure monitor,
The first control unit determines a control target value for the arterial volume and detects a first blood pressure value of the measurement subject.
The second control unit sets the second number based on the first blood pressure value detected by the first control unit.

  In the electronic sphygmomanometer according to this embodiment, the first control unit determines a control target value for the arterial volume and detects a first blood pressure value of the measurement subject. The second control unit sets the second number based on the first blood pressure value detected by the first control unit. That is, the second number is set based on the blood pressure value of the person to be measured obtained at the start of blood pressure measurement by the volume compensation method. Therefore, the necessary and sufficient number can be set more appropriately as the second number, and as a result, the necessary and sufficient capacity can be set more appropriately as the second capability. Thereby, the precision (resolution) which controls the pressure of the said cuff can further be raised, and the blood pressure for every heartbeat can be measured more accurately.

  In the electronic sphygmomanometer according to an embodiment, the second control unit sets the second number based on the first blood pressure value detected by the first control unit, and then the cuff of the cuff is set by the pressure adjustment unit. While the pressure is controlled, the second number is switched and set based on the second blood pressure value obtained based on the cuff pressure signal output from the pressure detector.

  In the electronic sphygmomanometer according to this embodiment, the second control unit sets the second number based on the first blood pressure value detected by the first control unit, and then the cuff is controlled by the pressure adjustment unit. The second number is switched and set based on the second blood pressure value obtained based on the cuff pressure signal output from the pressure detector while the pressure is controlled. That is, the second number is switched and set based on the blood pressure value obtained immediately before the subject. Therefore, the necessary and sufficient number can be set more appropriately as the second number, and as a result, the necessary and sufficient capacity can be set more appropriately as the second capability. Thereby, the precision (resolution) which controls the pressure of the said cuff can further be raised, and the blood pressure for every heartbeat can be measured more accurately.

  In the electronic sphygmomanometer according to one embodiment, the second control unit is configured such that the second number of units is different if a difference between the first blood pressure value and the second blood pressure value is less than a predetermined threshold value. Is maintained without switching.

  In the electronic sphygmomanometer according to the embodiment, the second control unit may perform the second control if the difference between the first blood pressure value and the second blood pressure value is less than a predetermined threshold value. Maintain the number without switching. Therefore, the second number is not switched unnecessarily.

In one embodiment of the electronic blood pressure monitor,
A storage unit for recording the blood pressure value of the measurement subject;
The second control unit sets the second number based on the blood pressure value of the measurement subject recorded in the storage unit.

  Here, the blood pressure value of the measurement subject may be acquired in the past by the electronic sphygmomanometer of the present invention (for example, before the start of measurement by the electronic sphygmomanometer of the present invention), or may be acquired in the past by another sphygmomanometer. It may be measured.

  Further, the blood pressure value of the person to be measured may be a representative value (for example, an average value, a median value, a maximum value, etc.) of blood pressure values obtained by a plurality of measurements.

  The electronic sphygmomanometer according to the embodiment further includes a storage unit that records the blood pressure value of the measurement subject. The second control unit sets the second number based on the blood pressure value of the measurement subject recorded in the storage unit. Therefore, the necessary and sufficient number can be set more appropriately as the second number, and as a result, the necessary and sufficient capacity can be set more appropriately as the second capability. Thereby, the precision (resolution) which controls the pressure of the said cuff can further be raised, and the blood pressure for every heartbeat can be measured more accurately.

In one embodiment of the electronic blood pressure monitor,
The pressure adjusting unit has a plurality of valves for discharging fluid from the cuff,
The first control unit changes the pressure of the cuff by operating the pressure adjusting unit with a first capacity using a first number of pumps and a third number of valves, and the arterial volume signal. Determining the direct current component of the arterial volume signal at the time of the maximum amplitude when the amplitude of the arterial volume change signal representing the change component due to the pulse wave is maximized as a control target value for the arterial volume,
The second control unit uses the second number of pumps greater than the first number and the fourth number of valves greater than the third number to control the pressure of the cuff. The pressure adjusting unit is operated with a second ability higher than the first ability.

  In the electronic sphygmomanometer according to this embodiment, the pressure adjusting unit has a plurality of valves for discharging fluid from the cuff. Then, the first control unit changes the pressure of the cuff by operating the pressure adjusting unit with a first capacity using a first number of pumps and a third number of valves, and The DC component of the arterial volume signal at the maximum amplitude when the amplitude of the arterial volume change signal representing the change component due to the pulse wave of the volume signal is maximized is determined as a control target value for the arterial volume. The second control unit uses a second number of pumps larger than the first number and a fourth number of valves larger than the third number in order to control the pressure of the cuff. The pressure adjusting unit is operated with a second ability higher than the first ability. Therefore, the fluid discharge capability of the valve can be set according to the fluid supply capability of the pump.

The blood pressure measurement method of the present invention includes
A blood pressure measurement method for measuring blood pressure for each heartbeat in a non-invasive manner by volume compensation,
Prepare a pressure regulator with multiple pumps that supply fluid to the cuff,
Attach a cuff to the measurement site,
While detecting the pressure of the cuff by the pressure detector and outputting it as a cuff pressure signal,
While detecting the volume of the artery of the measurement site by the arterial volume detection unit and outputting it as an arterial volume signal,
The amplitude of the arterial volume change signal representing the change component due to the pulse wave of the arterial volume signal by changing the pressure of the cuff by operating the pressure adjusting unit with the first capacity using the first number of pumps. Determine the direct current component of the arterial volume signal at the maximum amplitude when the maximum is as a control target value for the arterial volume,
In the blood pressure measurement method in which after the control target value is determined, feedback control is performed and the pressure adjusting unit controls the pressure of the cuff so that the arterial volume signal matches the control target value.
In order to control the pressure of the cuff, the pressure adjusting unit is operated with a second capacity higher than the first capacity by using a second number of pumps larger than the first number. And

  According to this blood pressure measurement method, when performing blood pressure measurement for each heartbeat noninvasively by the volume compensation method, the performance (flow rate per unit time) required for performing cuff pressure control is satisfied. be able to. In addition, since the second number is plural, ripples (pulsations in the discharged fluid) generated randomly by each pump cancel each other and are averaged. Therefore, the fluctuation of the cuff pressure can be reduced as compared with the case where one large-capacity pump is used. Thereby, the pressure of the cuff attached to the measurement site can be appropriately controlled.

  As is clear from the above, according to the electronic sphygmomanometer and blood pressure measurement method of the present invention, when blood pressure measurement for each heartbeat is performed noninvasively by the volume compensation method, the cuff attached to the measurement site The pressure can be controlled appropriately.

It is a figure which shows the block configuration of the electronic blood pressure monitor of one Embodiment of this invention. It is a figure which shows the flow of the blood-pressure measurement process by the said electronic blood pressure monitor. It is a figure which shows the time-dependent change of the cuff pressure Pc, arterial volume signal PGdc, and arterial volume change signal PGac when performing the said blood-pressure measurement process. It is a graph which shows the mechanical characteristic of an artery. It is a figure which shows the flow which determines the control target value and 1st blood pressure value for an arterial volume signal in the said blood pressure measurement process. It is a figure which shows the flow of the modification of the blood pressure measurement process of FIG. It is a figure which shows the flow of another modification of the blood pressure measurement process of FIG. It is a figure which shows the block configuration of the modification of the electronic blood pressure monitor of FIG. It is a figure explaining the blood pressure waveform of 1 heartbeat. It is a scatter diagram which shows the relationship between the systolic blood pressure about many people, and a pulse pressure. It is a figure which shows the characteristic of the cuff mounted | worn with a wrist, ie, the relationship between a cuff pressure (mmHg) and a cuff-compliance (ml / mmHg).

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 shows a block configuration of an electronic sphygmomanometer (hereinafter, simply referred to as “sphygmomanometer” as appropriate) according to an embodiment.

  This sphygmomanometer includes a cuff 20 attached to a site to be measured, a pressure detection unit 30 and a pressure adjustment unit 50 connected to an air bag 21 contained in the cuff 20 via an air tube 31, and arterial volume detection. Unit 70, CPU (Central Processing Unit) 100 that controls the operation of the entire sphygmomanometer, display unit 40, first memory 42 and second memory 43, operation unit 41, and power supply 44 And a clock 45.

  In a state where the cuff 20 is attached to the measurement site, the air bag 21 is used to press the measurement site. Although the cuff 20 includes the air bag 21 and air is supplied as a fluid, the fluid supplied to the cuff 20 is not limited to air, and may be a liquid or a gel, for example. Good.

  The pressure detection unit 30 includes a pressure sensor 32 for detecting the pressure of the cuff 20, more precisely, the pressure in the air bladder 21, and an oscillation circuit 33. In this example, the pressure sensor 32 is a capacitance type pressure sensor, and the capacitance value changes according to 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 converts the signal obtained from the oscillation circuit 33 into a pressure and obtains it as a cuff pressure signal Pc representing the cuff pressure (hereinafter, referred to as “cuff pressure Pc” as appropriate).

  The pressure adjustment unit 50 supplies a plurality of pumps 51A, 51B, 51C,... For supplying air to the air bladder 21 and the corresponding pumps 51A, 51B, 51C,. Based on pump control circuits 53A, 53B, 53C,..., One valve 52 that is opened and closed to discharge or seal the air in the air bag 21, and a control signal supplied from the CPU 100 And a valve drive circuit 54 for controlling the opening and closing of 52.

  In this example, the pumps 51A, 51B, 51C,... Are general diaphragm pumps, and the air supply capacity per unit is about 1 l / m. It is assumed that ten pumps 51A, 51B, 51C,... Are prepared.

  The arterial volume detection unit 70 includes a light emitting element 71 and a light receiving element 72 as photoelectric sensors arranged at predetermined intervals inside the air bag 21 in the cuff 20, a light emitting element driving circuit 73, and an arterial volume detection circuit 74. Is included. The light emitting element driving 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 light emitting element 71 irradiates light to the artery passing through the measurement site. The light receiving element 72 receives light that is transmitted through or reflected by the artery at the measurement site, that is, light that reflects the volume of the artery. The arterial volume detection circuit 74 converts the output from the light receiving element 72 into a voltage value and obtains it as an arterial volume signal PGdc representing the volume of the artery (photoplethysmography method).

  The arterial volume detection unit 70 only needs to be able to detect the volume of the artery, and may be one that detects the volume of the artery using an impedance sensor, for example, by impedance plethysmography. In that case, instead of the light emitting element 71 and the light receiving element 72, a plurality of electrodes (an electrode pair for applying a voltage to the measurement site and an electrode for detecting a current flowing through the measurement site) for detecting the impedance of the site including the artery Pair) is used.

  The display unit 40 is configured by, for example, a liquid crystal display or an EL (electroluminescence) display, and displays information related to blood pressure such as a blood pressure value, a blood pressure waveform, and a pulse rate in accordance with a signal received from the CPU 100.

  The first memory 42 stores a program for causing the CPU 100 to control blood pressure measurement processing described later, and various data for control.

  The second memory 43 stores information regarding the measured blood pressure.

  The operation unit 41 includes a power switch 41A that receives an input of an instruction to turn on or off the power, a measurement switch 41B that receives an instruction to start measurement, a stop switch 41C that receives an instruction to stop measurement, 2 includes a recording call switch 41D for receiving an instruction to read out information related to blood pressure recorded in the memory 43.

  The power supply 44 supplies power to each unit (including the CPU 100) of the sphygmomanometer or stops the supply in accordance with an operation on the power switch 41A.

  The clock 45 performs a time measuring operation and serves as a reference clock for the operation of the CPU 100.

  FIG. 2 shows a flow of blood pressure measurement processing by this blood pressure monitor. This sphygmomanometer measures blood pressure every heartbeat in a non-invasive manner by volume compensation.

  Specifically, first, the user presses the power switch (SW) 41A (step S1). Then, the CPU 100 initializes the processing memory area of the CPU 100 as initialization of the blood pressure monitor. Further, the air in the cuff 20 (the air bag 21) is exhausted by the pressure adjusting unit 50, and correction is performed so that the output (cuff pressure signal Pc) of the pressure detecting unit 30 at this time is 0 mmHg (step S2).

  Next, the user presses the measurement switch (step S3). Then, the CPU 100 determines the control target value V0 and the control initial cuff pressure PC_V0 for the arterial volume in the volume compensation method, and becomes a reference for setting the capability of the pressure adjusting unit 50 in step S6 described later. A blood pressure value is obtained (step S4).

  Here, the control target value V0 for the arterial volume will be described with reference to FIG. 4 showing the mechanical characteristics of the artery. The horizontal axis in FIG. 4 represents the arterial pressure difference Ptr, and the vertical axis represents the arterial volume V. The arterial internal / external pressure difference Ptr corresponds to the difference between the arterial internal pressure Pa and the cuff pressure (expressed by a cuff pressure signal) Pc.

  As shown in FIG. 4, in the arterial dynamic characteristics, when the intra-arterial pressure difference Ptr is 0 (equilibrium state), the arterial compliance is maximized, and the arterial volume change ΔV due to pulse pressure variation is maximized. Therefore, in the volume compensation method, the point at which the amplitude of the arterial volume change signal PGac becomes maximum in the process of gradually increasing the cuff pressure Pc is obtained, and the point when the amplitude of the arterial volume change signal PGac becomes maximum (maximum amplitude). The value of the arterial volume signal PGdc at the time point (pointing to a direct current component) is determined as the control target value V0 for the arterial volume.

  Specifically, the CPU 100 works as the first control unit to determine the control target value V0 for the arterial volume according to the flow shown in FIG. 5 as follows, and to determine the first blood pressure value (systolic blood pressure and diastole). Blood pressure).

  First, the CPU 100 reserves a temporary arterial volume signal (this is referred to as PGdc_temp) secured in the first memory 42, a temporary arterial volume change signal maximum value (this A memory area M2 in which PGac_temp is to be stored and a memory area M3 in which a temporary control initial cuff pressure value (this is referred to as Pc_temp) are to be initialized (step S101).

Here, the first memory 42 has the following memory areas M1, M2, and M3.
(First memory 42)

  Next, the valve 52 is closed (step S102). Then, the pressure adjusting unit 50 is operated with the first capacity (about 1 l / min) using one pump (51A) as the first number. The cuff pressure Pc is gradually increased by the pump 51A (step S103). During the pressurization of the cuff pressure Pc, the arterial volume detection unit 70 causes the arterial volume signal PGdc indicating the volume of the artery at the site to be measured, and the arterial volume change which is a change component due to the pulse wave of the arterial volume signal PGdc. The signal PGac is detected (step S104).

  The upper part of FIG. 3 shows the change of the cuff pressure Pc with time, the middle part of FIG. 3 shows the arterial volume signal PGdc that changes according to the cuff pressure Pc, and the lower part of FIG. 3 shows the arterial volume change signal PGac. Show. In the initial stage of time 0 to 0.2 [min], the cuff pressure Pc increases, the arterial volume signal PGdc decreases, and the arterial volume change signal PGac increases.

  Next, as shown in step S105 in FIG. 5, the detected amplitude of the arterial volume change signal PGac and the arterial volume change signal maximum value PGac_temp are compared. Here, when the amplitude of the arterial volume change signal PGac is larger than the maximum value PGac_temp of the arterial volume change signal (YES in step S105), the amplitude of the arterial volume change signal PGac at that time is stored in the memory area M2. The arterial volume change signal maximum value PGac_temp is updated (step S106). At the same time, the arterial volume signal PGdc_temp stored in the memory area M1 is updated using the value of the arterial volume signal PGdc at that time, and stored in the memory area M3 using the cuff pressure Pc at that time. The control initial cuff pressure value Pc_temp is updated.

  In the example of FIG. 3, the arterial volume signal PGdc_temp, the arterial volume change signal maximum value PGac_temp, and the control initial cuff pressure Pc_temp are provisional values at the initial stage of time 0 to 0.2 [min]. In the example of FIG. 3, the amplitude of the arterial volume change signal PGac shows a maximum value when about 0.2 [min] has elapsed from the start of pressurization (maximum amplitude time point), and this maximum value is set as PGac_Max in the memory area M2. Retained. Further, the value of the arterial volume signal PGdc_temp at the maximum amplitude is held in the memory area M1, and the control initial cuff pressure value Pc_temp at the maximum amplitude is held in the memory area M3.

  After the maximum amplitude point, the amplitude of the arterial volume change signal PGac becomes smaller than the maximum arterial volume change signal value PGac_temp (NO in step S105 in FIG. 5), and the contents of the memory areas M1, M2, and M3 are updated. It will never be done.

  In this example, by using one pump 51A as the first number, the pressure adjusting unit 50 is operated with a relatively low first capacity (about 1 l / min), and the cuff pressure Pc is gradually increased. Therefore, it is possible to avoid a situation where the maximum amplitude point is missed.

  In parallel with this, based on the change in arterial volume (pressure pulse wave signal) superimposed on the cuff pressure, the blood pressure value of the person to be measured is converted into the first blood pressure value (the systolic blood pressure and the blood pressure value) by a known oscillometric method, for example. (Including diastolic blood pressure)) (step S107). The first blood pressure value may be calculated by the volume vibration method using the detected arterial volume change signal PGac.

  Next, as shown in step S108 in FIG. 5, it is determined whether or not the cuff pressure has reached a predetermined pressure (referred to as Pc_A). If the cuff pressure has not reached the predetermined pressure Pc_A (NO in step S108), the processing from step S103 to step S107 is repeated. As this predetermined pressure Pc_A, a pressure sufficiently higher than the systolic blood pressure of the measurement subject is used. For example, a fixed value such as 180 mmHg may be used as Pc_A, or a value obtained by adding 30 mmHg to the systolic blood pressure calculated during the pressurization may be used.

  When the cuff pressure reaches the predetermined pressure Pc_A (YES in step S108), the value of the arterial volume signal PGdc_temp held in the memory area M1 at that time is determined as the control target value V0 for the arterial volume, and at that time The control initial cuff pressure value Pc_temp held in the memory area M3 is determined as the control initial cuff pressure PC_V0 (step S109).

  After determining the control target value V0, the control initial cuff pressure PC_V0, and the first blood pressure value of the measurement subject for the arterial volume in this way, the process proceeds to step S5 in FIG.

  In step S5 and subsequent steps in FIG. 2, the CPU 100 operates as the second control unit and performs the following processing.

  First, based on the first blood pressure value (including systolic blood pressure and diastolic blood pressure) obtained in step S4, the number of pumps to be driven is set to the first number (one in the above example). ) Is determined as a second number greater than (step S5).

  Here, the second number is calculated from the cuff-compliance shown in FIG. 11, the pulse pressure that is the difference between the systolic blood pressure and the diastolic blood pressure represented by the first blood pressure value, and the pulse wave rise time tr. It is determined by the required flow rate (l / m) to be determined.

  Specifically, if the systolic blood pressure is 130 mmHg, the diastolic blood pressure is 90 mmHg, and the pulse pressure is 40 mmHg, the required flow rate is 42.6 ml / s (= 2.6 l / m) when the pulse wave rise time tr is 0.08 s. ) In this example, since the air supply capacity per pump is about 1 l / m, the second number is set to, for example, 3 so that the required flow rate of 2.6 l / m can be supplied.

  However, taking into consideration the possibility that the blood pressure of the measurement subject will fluctuate, a margin of a predetermined ratio (for example, 1.5 times) may be secured. For example, since 2.6 l / m × 1.5 = 3.9 l / m, the second number may be four.

  Further, although the pulse wave rise time tr is set to 0.08 s, it may be set to the actual pulse wave rise time of the measurement subject.

  In general, a cuff having a very small capacity is used for the volume compensation method. This is to realize a pressure change corresponding to the pulse pressure within the pulse wave rise time tr.

  Subsequently, in step S6, the second capacity higher than the first capacity in step S4 is used by using a plurality of pumps (pumps 51A, 51B, 51C) determined as the second number. The pressure adjusting unit 50 is operated with the ability (pump control). In this example, the voltages applied to the pumps 51A, 51B, and 51C by the pump drive circuits 53A, 53B, and 53C are made constant, the degree of opening of the valve 52 is adjusted, and the cuff pressure Pc is set to the control initial cuff pressure PC_V0 ( Step S7). In the example of FIG. 3, the cuff pressure Pc is set to the control initial cuff pressure PC_V0 when about 0.4 [min] has elapsed from the start of pressurization.

  Assuming that the cuff pressure Pc is controlled by adjusting the voltage applied to the pumps 51A, 51B, and 51C and making the opening amount of the valve 52 constant, in a general pump, the discharge fluid with respect to the drive voltage Since the responsiveness and resolution of the amount of change are low, it is difficult to match the cuff pressure Pc with the change in blood pressure for each heartbeat. Therefore, it is practical to control the cuff pressure Pc by making the voltage applied to the pumps 51A, 51B, and 51C constant and adjusting the opening amount of the valve 52. However, the drive voltage applied to the pumps 51A, 51B, 51C may be controlled.

  Next, in step S8 in FIG. 2, the CPU 100 performs PID control as feedback control to suppress the arterial volume change signal PGac so that the arterial volume signal PGdc matches the control target value V0 for the arterial volume. The cuff pressure Pc is controlled by the pressure adjusting unit 50.

  Specifically, first, the amplitude of the arterial volume change signal PGac at the time when the control target value V0 is determined (this is referred to as “PGac_V0”) is stored in the first memory 42. The initial value of the control gain for PID control is set to the minimum value that can be set. Here, the “control gain” of the feedback control means the pressure of the cuff (that is, the cuff pressure signal) based on the change component of the arterial volume signal so that the arterial volume signal matches the control target value. It means the control gain for controlling.

  Next, the amplitude of the current arterial volume change signal PGac (during PID control) is compared with PGac_V0, and it is determined whether or not the ratio is equal to or less than a predetermined ratio α (step S9). This ratio α is, for example, 30%.

  When it is determined that the ratio of the amplitude of the current arterial volume change signal PGac to PGac_V0 exceeds α (NO in step S9), the PID control gain is increased by a predetermined unit and updated (step S10). On the other hand, if it is determined that the ratio of the current arterial volume change signal PGac to PGac_V0 is equal to or less than α (YES in step S9), updating of the control gain of PID control is stopped, and the cuff pressure signal Pc at that time is stopped. Is determined as the second blood pressure value of the person to be measured (step S11).

  These processes (steps S8 to S11) are continued until an instruction to stop blood pressure measurement is input (stop signal ON) (NO in step S12). The instruction to stop the blood pressure measurement may be input by, for example, the stop switch 41C of the operation unit 41, or the elapsed time from the start of blood pressure measurement is measured by the clock 45 and stopped when a predetermined time (for example, 3 minutes) elapses. It is also good to do.

  When an instruction to stop blood pressure measurement is input (YES in step S12), the pumps 51A, 51B, 51C are stopped, the valve 52 is opened (step S13), and the blood pressure measurement is terminated.

  As described above, in this sphygmomanometer, in order to control the cuff pressure Pc at the stage of measuring the blood pressure for each heartbeat (steps S8 to S11), the second number of pumps 51A, 51B, 51C are used. Is used to operate the pressure adjusting unit 50 with a second ability higher than the first ability at the time of step S4. Therefore, the performance (flow rate per unit time) required for performing the cuff pressure control can be satisfied. Further, since the second number is plural, ripples (pulsations in the discharged fluid) generated randomly by the respective pumps 51A, 51B, 51C cancel each other and are averaged. Therefore, the fluctuation of the cuff pressure can be reduced as compared with the case where one large-capacity pump is used. Thereby, the pressure of the cuff attached to the measurement site can be appropriately controlled. As a result, in a situation where the internal pressure of the artery and the pressure of the cuff are always matched (regardless of the pulse), the blood pressure for each heartbeat is continuously accurately determined based on the cuff pressure signal Pc output from the pressure detection unit 50. Can be measured.

  The second number is set based on the first blood pressure value of the person to be measured obtained at the start stage of blood pressure measurement by the volume compensation method (step S4 in FIG. 2). Therefore, a necessary and sufficient number can be set as the second number, and as a result, a necessary and sufficient capacity can be set as the second capacity of the pressure adjusting unit 50. Thereby, the precision (resolution) which controls the cuff pressure Pc can be raised, and the blood pressure for every heartbeat can be measured accurately.

  FIG. 6 shows a flow of a modification of the blood pressure measurement process of FIG.

  6 is based on the premise that the blood pressure value of the person to be measured is recorded in the second memory 43 serving as a storage unit. The blood pressure value recorded in the second memory 43 may be acquired in the past by this sphygmomanometer (before starting measurement by this sphygmomanometer) or may be measured in the past by another sphygmomanometer. Further, the blood pressure value recorded in the second memory 43 may be a representative value (for example, an average value, a median value, a maximum value, etc.) of blood pressure values obtained by a plurality of measurements.

  In the blood pressure measurement process of FIG. 6, only steps S4 ′ and S5 ′ are different from steps S4 and S5 in the blood pressure measurement process of FIG. For simplicity, steps having the same contents as those in FIG. 2 are denoted by the same step numbers, and redundant description is omitted (the same applies to FIG. 7 described later).

  In step S4 ′ of FIG. 6, the same process as step S4 of FIG. 2 is performed except that the process of obtaining the first blood pressure value (step S107 in FIG. 5) is omitted. Thus, the control target value V0 and the control initial cuff pressure PC_V0 for the arterial volume described above are determined.

  Next, in step S5 ′ of FIG. 6, the number of pumps to be driven is determined based on the blood pressure value of the person to be measured recorded in the second memory 43 by the first number (one in the above example). ) Is determined as the second number more than. The specific method for determining the number of pumps is the same as in step S5 of FIG.

  According to the blood pressure measurement process of FIG. 6, as in the blood pressure measurement process of FIG. 2, a necessary and sufficient number can be set as the second number, and as a result, the second capacity of the pressure adjustment unit 50 is necessary and sufficient. You can set the ability. Thereby, the precision (resolution) which controls the cuff pressure Pc can be raised, and the blood pressure for every heartbeat can be measured accurately.

  FIG. 7 shows a flow of another modification of the blood pressure measurement process of FIG.

  7 is different from the blood pressure measurement process in FIG. 2 only in that steps S201 and S202 are added after step S11. That is, in the blood pressure measurement process of FIG. 7, the second blood pressure is switched and set based on the second blood pressure value obtained at the stage of measuring the blood pressure for each heartbeat. It is different from the measurement process.

  Specifically, after determining the second blood pressure value of the measurement subject in step S201 in FIG. 7, in step S201, the difference between the first blood pressure value and the second blood pressure value is calculated, and the difference is calculated. Is greater than or equal to a predetermined threshold (ΔPc_d).

  Here, for example, one or both of systolic blood pressure and diastolic blood pressure are used as the first blood pressure value and the second blood pressure value, respectively. The threshold value ΔPc_d is set to 20 mmHg, for example. That is, it is determined whether or not the difference between “systolic blood pressure at the first blood pressure value” and “systolic blood pressure at the second blood pressure value” is equal to or greater than ΔPc_d (= 20 mmHg). This is because, if the difference is not 20 mmHg or more, it is sufficient to change the driving voltage of each pump, and it is considered that there is little need to change the number of pumps. When both the systolic blood pressure and the diastolic blood pressure are used as the first blood pressure value and the second blood pressure value, respectively, “systolic blood pressure at the first blood pressure value” and “systolic blood pressure at the second blood pressure value”. And / or the difference between “diastolic blood pressure at the first blood pressure value” and “diastolic blood pressure at the second blood pressure value” is at least ΔPc_d (= 20 mmHg). to decide.

  Alternatively, for example, “the difference between the systolic blood pressure and the diastolic blood pressure at the first blood pressure value (pulse pressure)” and “the difference between the systolic blood pressure and the diastolic blood pressure at the second blood pressure value (pulse). It may be determined whether or not the difference from “pressure” is equal to or greater than ΔPc_d (= 20 mmHg).

  If the difference is not less than the threshold value ΔPc_d (YES in step S201), the number of pumps is switched and set (changed) based on the second blood pressure value.

  Here, the way of determining the number of pumps based on the second blood pressure value is the same as the way of determining the number of pumps based on the first blood pressure value (step S5 in FIG. 2).

  In this case, the necessary and sufficient number can be set more appropriately as the second number, and as a result, the necessary and sufficient capacity can be set more appropriately as the second ability of the pressure adjusting unit 50. Thereby, the accuracy (resolution) for controlling the cuff pressure Pc can be further increased, and the blood pressure for each heartbeat can be measured with higher accuracy.

  On the other hand, if the difference is less than the threshold ΔPc_d (NO in step S201), the second number is maintained without being switched. Therefore, the second number is not switched unnecessarily.

  Further, when the blood pressure for each heartbeat is measured, a transition of the second blood pressure value is detected. When the transition is equal to or greater than a predetermined threshold value ΔPc_d, the number of pumps is switched based on the blood pressure value after the transition. May be set.

  FIG. 8 shows a block configuration of a modification of the electronic sphygmomanometer of FIG.

  In the modified example (electronic sphygmomanometer) of FIG. 8, the pressure adjustment unit 50 includes a plurality of valves 52 </ b> A, 52 </ b> B, 52 </ b> C,... That are opened and closed to discharge or seal the air in the air bag 21. Are provided with valve drive circuits 54A, 54B, 54C,... For controlling the opening and closing of the corresponding valves 52A, 52B, 52C,. Other configurations are the same as those of the electronic blood pressure monitor of FIG.

  In the electronic sphygmomanometer of FIG. 8, in step S4 in FIG. 2, a first number (for example, one) of pumps and a third number (for example, one) of valves (referred to as 52A) are used. The pressure adjusting unit 50 is operated with the ability of 1. Thereby, the DC component of the arterial volume signal PGdc at the maximum amplitude when the amplitude of the arterial volume change signal PGac becomes maximum is determined as the control target value PC_V0 for the arterial volume by changing the cuff pressure Pc. Thereafter, in order to control the cuff pressure Pc at the stage of measuring blood pressure for each heartbeat (steps S8 to S11 in FIG. 2), a second number (a plurality) of pumps, which is larger than the first number. .., And a fourth number (plural number) of valves 52A, 52B, 52C,... That is larger than the third number, and a pressure with a second capacity higher than the first capacity. The adjustment unit 50 is operated. Therefore, the fluid discharge capability by the valves 52A, 52B, 52C,... Can be set according to the fluid supply capability by the pumps 51A, 51B, 51C,. Thereby, the pressure of the cuff attached to the measurement site can be appropriately controlled.

  The above embodiments are merely examples, and various modifications can be made without departing from the scope of the present invention.

20 Cuff 30 Pressure detection unit 50 Pressure adjustment unit 51A, 51B, 51C, ... Pump 52A, 52B, 52C, ... Valve 70 Arterial volume detection unit 100 CPU

Claims (8)

An electronic sphygmomanometer that non-invasively measures blood pressure for each heartbeat by volume compensation,
A cuff attached to the measurement site;
A plurality of pumps for supplying fluid to the cuff, and a pressure adjusting unit for adjusting the pressure of the cuff;
A pressure detector for detecting the pressure of the cuff;
An arterial volume detector that detects the volume of the artery of the measurement site and outputs it as an arterial volume signal;
The amplitude of the arterial volume change signal representing the change component due to the pulse wave of the arterial volume signal by changing the pressure of the cuff by operating the pressure adjusting unit with the first capacity using the first number of pumps. A first control unit that determines a direct current component of the arterial volume signal at the time of maximum amplitude when becomes a maximum as a control target value for the arterial volume;
A second control unit that performs feedback control after the control target value is determined and controls the pressure of the cuff by the pressure adjustment unit so that the arterial volume signal matches the control target value; ,
The second control unit controls the pressure of the cuff with a second capacity higher than the first capacity using a second number of pumps greater than the first number to control the pressure of the cuff. An electronic sphygmomanometer characterized by operating a part. The electronic sphygmomanometer according to claim 1,
The second control unit sets the second number based on the blood pressure value of the person to be measured. The electronic blood pressure monitor according to claim 2,
The first control unit determines a control target value for the arterial volume and detects a first blood pressure value of the measurement subject.
The second sphygmomanometer sets the second number based on the first blood pressure value detected by the first control unit. The electronic blood pressure monitor according to claim 3,
The second control unit sets the second number based on the first blood pressure value detected by the first control unit, and then controls the pressure of the cuff by the pressure adjustment unit. An electronic sphygmomanometer, wherein the second number is switched and set based on a second blood pressure value obtained based on a cuff pressure signal output from the pressure detector. The electronic blood pressure monitor according to claim 4,
The second control unit maintains the second number without switching if the difference between the first blood pressure value and the second blood pressure value is less than a predetermined threshold value. Electronic blood pressure monitor. The electronic blood pressure monitor according to claim 2,
A storage unit for recording the blood pressure value of the measurement subject;
The second control unit sets the second number based on the blood pressure value of the person to be measured recorded in the storage unit. The electronic blood pressure monitor according to any one of claims 1 to 6,
The pressure adjusting unit has a plurality of valves for discharging fluid from the cuff,
The first control unit changes the pressure of the cuff by operating the pressure adjusting unit with a first capacity using a first number of pumps and a third number of valves, and the arterial volume signal. Determining the direct current component of the arterial volume signal at the time of the maximum amplitude when the amplitude of the arterial volume change signal representing the change component due to the pulse wave is maximized as a control target value for the arterial volume,
The second control unit uses the second number of pumps greater than the first number and the fourth number of valves greater than the third number to control the pressure of the cuff. An electronic sphygmomanometer, wherein the pressure adjusting unit is operated with a second ability higher than the first ability. A blood pressure measurement method for measuring blood pressure for each heartbeat in a non-invasive manner by volume compensation,
Prepare a pressure regulator with multiple pumps that supply fluid to the cuff,
Attach a cuff to the measurement site,
While detecting the pressure of the cuff by the pressure detector and outputting it as a cuff pressure signal,
While detecting the volume of the artery of the measurement site by the arterial volume detection unit and outputting it as an arterial volume signal,
The amplitude of the arterial volume change signal representing the change component due to the pulse wave of the arterial volume signal by changing the pressure of the cuff by operating the pressure adjusting unit with the first capacity using the first number of pumps. Determine the direct current component of the arterial volume signal at the maximum amplitude when the maximum is as a control target value for the arterial volume,
In the blood pressure measurement method in which after the control target value is determined, feedback control is performed and the pressure adjusting unit controls the pressure of the cuff so that the arterial volume signal matches the control target value.
In order to control the pressure of the cuff, the pressure adjusting unit is operated with a second capacity higher than the first capacity by using a second number of pumps larger than the first number. Blood pressure measurement method.

Images