WO2013061778A1

WO2013061778A1 - Blood pressure meter

Info

Publication number: WO2013061778A1
Application number: PCT/JP2012/076230
Authority: WO
Inventors: 広幸木下; 佐藤　博則; 藤井　健司; 幸哉澤野井
Original assignee: オムロンヘルスケア株式会社
Priority date: 2011-10-26
Filing date: 2012-10-10
Publication date: 2013-05-02
Also published as: JP2013090824A

Abstract

A blood pressure meter (100) is provided with: a cuff to be disposed around the periphery of the part of a person at which blood pressure is to be measured; an adjustment unit for adjusting pressure within the cuff by controlling a pump for supplying fluid into the cuff; a control unit for controlling the adjustment unit so that, during the measurement of blood pressure, the pressure within the cuff is increased at a constant speed according to a target pressurization speed; a pressure detection unit for detecting a cuff pressure representing the pressure within the cuff; a pulse wave detection unit (118) for detecting a pulse wave superposed on the cuff pressure; a blood pressure calculation unit for calculating blood pressure on the basis of the detected cuff pressure and of a pulse wave amplitude; and a target change unit (114) for changing in a variable manner the target pressurization speed. The blood pressure calculation unit changes the pulse wave amplitude so as to correct an error in the pulse wave amplitude caused by a change in the target pressurization speed and calculates blood pressure on the basis of the cuff pressure and the changed pulse wave amplitude.

Description

Electronic blood pressure monitor

The present invention relates to an electronic sphygmomanometer, and more particularly to an electronic sphygmomanometer that measures blood pressure using a pulse wave detected from a measurement site.

Blood pressure is one of the indices for analyzing circulatory diseases, and risk analysis based on blood pressure is effective in preventing cardiovascular diseases such as stroke, heart failure and myocardial infarction. Conventionally, diagnosis has been performed based on blood pressure (anytime blood pressure) measured at a medical institution such as when visiting a hospital or during a medical examination. However, recent studies have shown that blood pressure measured at home (home blood pressure) is more useful for diagnosis of cardiovascular diseases than blood pressure at any time. Accordingly, blood pressure monitors used at home have become widespread.

Most home blood pressure monitors use the oscillometric blood pressure measurement method. Blood pressure measurement by the oscillometric method is to wrap the cuff around a measurement site such as the upper arm, pressurize the cuff internal pressure (cuff pressure) by a predetermined pressure (for example, 30 mmHg) higher than the systolic blood pressure, and then gradually or stepwise. Reduce the cuff pressure. In this decompression process, the volume change of the artery is detected as a pressure change (pulse wave amplitude) superimposed on the cuff pressure, and the systolic blood pressure and the diastolic blood pressure are determined from the change in the pulse wave amplitude. In the oscillometric method, the blood pressure can be measured by detecting the amplitude of the pulse wave generated in the process of increasing the cuff pressure.

In order to accurately detect the pulse wave amplitude in these blood pressure measurements, it is necessary to increase or decrease the cuff pressure at a constant speed by a pump or a valve. Therefore, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-129920), the constant speed pressurization control or the constant speed depressurization control is based on the difference between the average speed and the target speed so that the average speed becomes the target speed. Alternatively, the valve drive voltage is feedback controlled.

JP 2006-129920 A

FIG. 16 is a diagram schematically showing the relationship between the output flow rate of the pump of the conventional blood pressure monitor and the cuff pressure. FIG. 17 schematically shows the relationship between the conventional cuff pressure constant velocity pressurization and the pump drive voltage. In home sphygmomanometers, miniaturization and cost reduction are required from the viewpoint of improving usability, and the pump is small to meet this demand. As shown in FIG. 16, since the pump size and the output flow rate of fluid such as air from the pump are in a trade-off relationship, a small pump cannot achieve a desired pressurization speed compared to a large pump. There is.

In the case of a small pump, if the drive voltage that is feedback controlled so that the pressurization speed matches the target speed exceeds the upper limit voltage of the pump drive, the speed can be increased further. Therefore, the cuff pressure cannot be increased at a constant speed (see FIG. 17). In this case, the pressure fluctuation factor within one pulse wave includes not only the volume change component of the pulse wave but also the pressurization speed change component, so that the detection accuracy of the pulse wave amplitude is lowered. As a result, blood pressure calculation accuracy also decreases.

Therefore, an object of the present invention is to provide an electronic sphygmomanometer that can calculate blood pressure from a pulse wave that eliminates an error due to a change in the cuff pressure pressurization speed.

An electronic sphygmomanometer according to an aspect of the present invention adjusts the pressure in the cuff by controlling a cuff wound around the measurement site of the measurement subject and a pump for supplying fluid into the cuff. For detecting the cuff pressure representing the pressure in the cuff, the control unit for controlling the adjustment unit so that the pressure in the cuff is pressurized at a constant speed according to the pressurization speed target during blood pressure measurement A pressure detector, a pulse wave detector for detecting a pulse wave superimposed on the cuff pressure, a blood pressure calculator for calculating blood pressure based on the detected cuff pressure and the pulse wave amplitude, A target changing unit that variably changes the pressure speed target. The blood pressure calculation unit changes the pulse wave amplitude so as to correct an error of the pulse wave amplitude due to the change of the pressurization speed target, and calculates the blood pressure based on the cuff pressure and the changed pulse wave amplitude.

According to the present invention, the blood pressure is calculated from the pulse wave from which the error due to the change in the cuff pressure is changed.

3 is a block diagram illustrating a hardware configuration of the electronic blood pressure monitor according to Embodiment 1. FIG. 3 is a block diagram showing a functional configuration of the electronic blood pressure monitor according to Embodiment 1. FIG. It is a figure explaining the influence which pressurization speed has on a pulse wave amplitude, and amplitude correction of a pulse wave. It is a figure explaining the influence which pressurization speed has on a pulse wave amplitude, and amplitude correction of a pulse wave. It is a figure which shows a cuff compliance characteristic. It is a figure which shows the table which stores the correction coefficient which concerns on embodiment. It is a figure which shows typically correction | amendment of the pulse wave amplitude by embodiment. It is a figure which shows the table referred in order to estimate the perimeter based on Embodiment. It is a graph of the cuff pressure-pressurization time characteristic (in the case of appropriate winding) by an embodiment. 3 is a processing flowchart of blood pressure measurement according to the first embodiment. FIG. 10 is a diagram for explaining the timing at which a pulse wave is detected in the pressurizing process according to the second embodiment. 6 is a functional block diagram showing a functional configuration of an electronic blood pressure monitor according to Embodiment 2. FIG. 10 is a processing flowchart of blood pressure measurement according to the second embodiment. FIG. 10 is a functional block diagram showing a functional configuration of an electronic blood pressure monitor according to Embodiment 3. It is a figure which shows the table for determining the pressurization speed target which concerns on Embodiment 3. FIG. It is a figure which shows typically the relationship between the output flow volume of the pump of the conventional blood pressure meter, and a cuff pressure. It is a figure which shows typically the relationship between the constant velocity pressurization of the conventional cuff pressure, and a pump drive voltage.

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

(Embodiment 1)
FIG. 1 is a block diagram showing a hardware configuration of electronic blood pressure monitor 100 according to the present embodiment. Referring to FIG. 1, an electronic sphygmomanometer 100 includes a cuff 20 and an air system 300 attached to a blood pressure measurement site. The cuff 20 includes an air bag 21. The air bag 21 is connected to the air system 300 via the air tube 31.

The electronic sphygmomanometer 100 further centrally controls the display unit 40, the operation unit 41, and each unit to perform various arithmetic processes, a CPU (Central Processing Unit) 10, a program for causing the CPU 10 to perform predetermined operations, and various types It includes a memory unit 42 for storing data, a power source 44 for supplying power to each unit, and a clock unit 45 for performing a timing operation. The memory unit 42 includes a nonvolatile memory (for example, a flash memory) for storing the measured blood pressure.

The operation unit 41 includes a power switch 41A that accepts an operation for turning the power on and off, a measurement switch 41B that accepts a measurement start operation, a stop switch 41C that accepts a measurement stop instruction operation, and a user (covered) A user selection switch 41E for accepting an operation for selectively designating (measurement person) is provided. The operation unit 41 also includes a switch (not shown) for receiving an operation for reading information such as measured blood pressure stored in the flash memory and displaying the information on the display unit.

In the present embodiment, since the electronic blood pressure monitor 100 is shared by a plurality of persons to be measured, the electronic blood pressure monitor 100 includes a user selection switch 41E. However, when not shared, the user selection switch 41E may be omitted. The measurement switch 41B may also be used as the power switch 41A. In that case, the measurement switch 41B can be omitted.

The air system 300 includes a pressure sensor 32 for detecting the pressure in the air bladder 21 (hereinafter referred to as cuff pressure), a pump 51 for supplying air to the air bladder 21 to increase the cuff pressure, and air It includes a valve 52 that is opened and closed to evacuate or seal the bag 21 air. The electronic sphygmomanometer 100 includes an oscillation circuit 33, a pump drive circuit 53, and a valve drive circuit 54 in association with the air system 300. Here, the pump 51, the valve 52, the pump drive circuit 53, and the valve drive circuit 54 correspond to the adjusting unit 30 for adjusting the cuff pressure.

The pump 51 may be a pump using a motor as a drive source, a piezoelectric micro pump using a piezoelectric element as a drive source, or the like.

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 (hereinafter referred to as a pressure signal) corresponding to the capacitance value of the pressure sensor 32 to the CPU 10. The CPU 10 detects the cuff pressure by converting the signal obtained from the oscillation circuit 33 into a pressure. The pump drive circuit 53 controls the pump 51 based on a control signal given from the CPU 10. The valve drive circuit 54 controls opening and closing of the valve 52 based on a control signal given from the CPU 10.

In addition, the fluid supplied to the cuff 20 is not limited to air, and may be a liquid or a gel, for example. Or it is not limited to fluid, Uniform microparticles, such as a microbead, may be sufficient.

(Functional configuration)
FIG. 2 is a functional block diagram showing a functional configuration of electronic blood pressure monitor 100 according to the present embodiment. The functional configuration is indicated by using the functions of the CPU 10 and its peripheral part.

Referring to FIG. 2, the CPU 10 includes a pulse wave detection unit 118 and a pressure detection unit 112 for inputting a pressure signal from the oscillation circuit 33, an amplitude correction unit 113 for correcting the amplitude of the pulse wave, and an addition during blood pressure measurement. A target changing unit 114 that changes a pressure speed target (hereinafter referred to as a pressurization speed target), a pressurization control unit 115 that outputs control signals to the pump drive circuit 53 and the valve drive circuit 54, a depressurization control unit 116, and a blood pressure value. Is provided with a blood pressure determination unit 117 for determining the data, a memory processing unit 119 for reading and writing (accessing) data in the flash memory of the memory unit 42, and a display control unit 120 for controlling display on the display unit 40. The pressurization control unit 115 and the decompression control unit 116 correspond to the drive control unit 111 for pressurizing the adjustment unit 30 during blood pressure measurement to pressurize the cuff pressure according to the pressurization speed target.

The pressurization control unit 115 and the pressure reduction control unit 116 transmit control signals to the pump drive circuit 53 and the valve drive circuit 54 in order to adjust the cuff pressure. Specifically, a control signal for increasing or decreasing the cuff pressure is output. In the present embodiment, the blood pressure derivation process is performed by the blood pressure determination unit 117 in the process of increasing the cuff pressure with the pressurization speed target. The pulse wave detection unit 118 detects a pulse wave signal representing a change in the volume of the artery superimposed on the pressure signal from the oscillation circuit 33 using a filter circuit. In order to detect the cuff pressure, the pressure detection unit 112 converts the pressure signal from the oscillation circuit 33 into a pressure value and outputs the pressure value.

The amplitude correction unit 113 includes a perimeter estimation unit 401 and a correction coefficient determination unit 402. The cuff 20 is wound around the measurement site, for example, the upper arm (or wrist). The perimeter estimation unit 401 estimates the length of the circumference (arm circumference) of the measurement site around which the cuff 20 is wound. The correction coefficient determination unit 402 determines a coefficient for correcting the pulse wave amplitude based on the pressurization speed target before and after the change.

The blood pressure determining unit 117 determines the blood pressure according to the oscillometric equation. Specifically, the pulse cuff pressure input from the pressure detection unit 112 during blood pressure measurement and the pulse wave detected by the pulse wave detection unit 118 or the pulse wave whose amplitude is corrected by the amplitude correction unit 113 are used. The blood pressure is determined based on the wave amplitude transition and the cuff pressure. For example, the cuff pressure corresponding to the maximum value of the pulse wave amplitude is the average blood pressure, the cuff pressure corresponding to the pulse wave amplitude on the high cuff pressure side corresponding to 50% of the maximum value of the pulse wave amplitude is the systolic blood pressure, and the pulse wave. The cuff pressure corresponding to the pulse wave amplitude on the low cuff pressure side corresponding to 70% of the maximum value of the amplitude is determined as the diastolic blood pressure. The pulse rate is calculated according to a known procedure using the pulse wave signal. Therefore, here, the amplitude correction unit 113 and the blood pressure determination unit 117 correspond to a blood pressure calculation unit for calculating blood pressure.

(Feedback control of pump 51)
When blood pressure is measured according to the oscillometric equation, the cuff pressure must be increased at a constant pressure target in order to obtain measurement accuracy. That is, the target changing unit 114 gives an initial value of the target speed to the pressurization control unit 115 at the start of blood pressure measurement. The pressurization control unit 115 calculates the cuff pressure change rate based on the cuff pressure periodically input from the pressure detection unit 112, and compares the calculated change rate with the pressurization rate target given from the target change unit 114. Then, a control signal based on the difference between the two based on the comparison result is generated and output to the pump drive circuit 53. Thus, the pump 51 is feedback-controlled so that the pressurization speed becomes the pressurization speed target.

Here, it is assumed that the discharge flow rate of the pump 51 is proportional to the voltage applied from the pump drive circuit 53. The pump drive circuit 53 outputs a voltage signal corresponding to the control signal to the pump 51. A voltage sensor (not shown) is provided at the output stage of the pump drive circuit 53, a voltage for driving the pump 51 is detected by the voltage sensor, and a drive voltage 511 indicating the detected voltage is output to the target changing unit 114. The

The target changing unit 114 compares the drive voltage 511 with the drive voltage upper limit 512 inherent to the pump 51, and based on the comparison result, the condition (drive voltage 511> drive voltage upper limit 512) is satisfied, and the output of the pump 51 is If it is determined that the maximum is not sufficient, the pressure speed target is changed to be lowered. Then, feedback control is performed using the changed pressurization speed target. Thereby, the pressurization speed can be controlled at a constant speed within a range where the output of the pump 51 has a margin.

(Pulse wave amplitude correction)
According to the oscillometric equation, the measurement accuracy of blood pressure depends on the pulse wave amplitude, but as described in FIGS. 16 and 17, the pulse wave amplitude includes the volume change component of the blood vessel within one pulse wave. In addition to the cuff pressure change rate component, it is necessary to correct the pulse wave amplitude error due to the latter component. Therefore, in the present embodiment, the pulse wave amplitude is corrected by eliminating the error caused by the change in the pressurization speed target described above.

Here, with reference to FIGS. 3 and 4, the influence of the pressurization speed on the pulse wave amplitude and the amplitude correction will be described. 3 and 4 are data obtained by the inventors' experiments, and show the influence of the decompression speed in the decompression process on the pulse wave amplitude. Note that the principle shown in FIGS. 3 and 4 can be applied in the same way even in the pressurizing process.

In FIGS. 3 and 4, the time change of the cuff pressure is shown in the lower stage, the time change of the cuff volume is shown in the middle stage, and the arterial blood vessel of the measurement site is shown in the upper stage in the cases where the decompression speed is fast and slow. The time variation of the volume of is shown. These show changes in the same period. In FIGS. 3 and 4, even if the blood vessel volume change ΔV due to the pulsation of the heart is equal as in the upper stage, the maximum change in cuff volume with respect to the baseline (shown by a dotted line) of the cuff volume waveform is shown in the middle stage. The value varies depending on the decompression speed (that is, ΔVa <ΔVb). Since this volume change appears as a cuff pressure change, the volume change of the cuff 20 increases as the depressurization speed decreases, and the cuff pressure change also differs as in the lower stage (ie, ΔPa <ΔPb). Therefore, even if the blood vessel volume changes in the same manner, the pulse wave amplitude detected by the pressure reduction rate or the pressure increase rate is different.

Further, from the cuff compliance characteristics shown in FIG. 5, since the cuff compliance becomes larger as the measurement site is thicker (periphery length is longer), the pulse wave calculated by the thickness of the measurement site is obtained even when the blood vessel volume changes similarly. It can be seen that the amplitudes are different. Here, the cuff compliance is a volume required to change the cuff pressure by 1 mmHg, and its unit is [ml / mmHg].

Therefore, the pulse wave amplitude detected when the pressurization speed of the cuff 20 is changed needs to be determined according to the rate of change of the pressurization speed and the circumference of the measurement site. Here, the change rate of the pressurization speed is determined according to the change rate of the pressurization speed target. Here, the rate of change refers to the ratio between the pressurization speed target before the change and the pressurization speed target after the change.

The memory unit 42 stores a correction coefficient α corresponding to the peripheral length L of the measurement region and the post-change pressurization speed target V (here, the pre-change pressurization speed target is constant). Table TB is stored. Therefore, it can be said that the correction coefficient α is stored in the table TB corresponding to each set of the peripheral length L and the change rate of the pressurization speed target. The data in FIG. 6 is acquired through experiments or the like.

At the time of blood pressure measurement, the circumference length L of the measurement site is estimated by the circumference length estimation unit 401 based on the pressure change characteristic immediately after the start of pressurization. After the pressurization speed target is changed by the target changing unit 114, the correction coefficient determination unit 402 searches the table TB based on the peripheral length L and the post-change pressurization speed target V, and the corresponding correction coefficient. Read α. Thereby, the correction coefficient α is determined.

The amplitude correction unit 113 extracts a pulse wave for each beat from the pulse wave signal (pressure signal) input from the pulse wave detection unit 118. Specifically, the difference between the current value of the pressure indicated by the pressure signal and the preceding value is calculated, it is determined whether the difference exceeds the reference, and the rising / falling point of the signal is extracted based on the determination result. Thereby, a pulse wave (one amplitude) can be extracted.

The amplitude correction unit 113 corrects the amplitude value of the extracted pulse wave using the correction coefficient α. That is, the detected pulse wave amplitude value Amp is corrected by Amp × α. The corrected pulse wave is output to the blood pressure determination unit 117. The blood pressure determination unit 117 determines the blood pressure according to the oscillometric equation using the pulse wave whose amplitude is corrected.

FIG. 7 schematically shows pulse wave amplitude correction according to the present embodiment. According to FIG. 7, as described above, when the pressurization speed target for constant speed pressurization is changed in the range where the output of the pump 51 has a margin, the error of the pulse wave amplitude due to the change is as described above. This can be eliminated by correcting the amplitude.

(Perimeter estimation)
The estimation of the circumference of the measurement site according to this embodiment will be described. FIG. 8 is a diagram showing an example of a table 433 that is referred to in order to estimate the measurement site circumference L according to the present embodiment. The table 433 stores the constant speed pressurization time required to pressurize the cuff pressure by a predetermined pressure when the winding state of the cuff 20 around the measurement site is “appropriate winding” and the corresponding peripheral length L. . The data in the table 433 is acquired in advance through experiments or the like. FIG. 9 is a graph of cuff pressure-pressurization time characteristics (in the case of appropriate winding) according to the present embodiment. 8 and 9 indicate values based on data sampled from many subjects using the electronic sphygmomanometer 100. Here, “appropriate winding” refers to a state substantially equal to the length of the circumference by the inner diameter of the cuff 20 wound around the circumference of the measurement site (diameter of the cross section of the arm as the measurement site). In the present embodiment, it is assumed that blood pressure is measured in an appropriate winding state.

Necessary until the cuff pressure changes from the pressure P2 to the pressure P3 based on the cuff pressure of the cuff 20 wound around the measurement site and the volume change of the fluid (air in the present embodiment) supplied into the cuff 20. The air is assumed to have a fluid volume ΔV23 (see FIG. 9). The pressurization time required for the pump 51 to supply the air of the fluid volume ΔV23 under constant pressure pressurization (constant rotation speed) in the pressurization process is a fixed time (here, time V23 from time V2 to time V3). It becomes. However, the time V23 varies depending on the peripheral length L of the measurement site.

For example, when the cuff 20 is wound with appropriate winding on measurement sites having different perimeters, as the perimeter is shorter (thin arm), the time V23 is smaller and the perimeter is longer (thick arm) as shown in FIG. ) V23 increases.

The peripheral length estimation unit 401 uses the clock unit 45 to measure the time required for the cuff pressure to change from 0 mmHg (pressure P2) to 20 mmHg (pressure P3) based on the detected cuff pressure after the start of pressurization. Then, the corresponding peripheral length L is acquired by searching the table 432 based on the measured time. The peripheral length L is given to the correction coefficient determination unit 402. The correction coefficient determination unit 402 searches the table TB based on the peripheral length L and the changed pressurization speed target V, and reads the corresponding correction coefficient α. Thereby, the correction coefficient α is determined.

Note that, here, the peripheral length L is estimated (measured) at the time of blood pressure measurement, but the measured person may operate and input the operation unit 41 at the time of measurement. Alternatively, the peripheral length L may be stored in advance in the memory unit 42 for each person to be measured.

(flowchart)
FIG. 10 is a processing flowchart of blood pressure measurement according to the present embodiment. The program according to this flowchart is stored in advance in the memory unit 42, read from the memory unit 42 by the CPU 10, and executed.

When the measurement subject operates the power switch 41A (or the measurement switch 41B) with the cuff 20 wound around the measurement site in an appropriate manner (step ST1), the CPU 10 performs a predetermined initialization process, and then the CPU 10 Outputs a control signal for closing the valve 52 to the valve drive circuit 54. Thereby, the valve 52 is closed by the valve drive circuit 54 (step ST3). In FIG. 10, “SW” means a switch.

The drive control unit 111 initially sets the pressurization speed target to a predetermined value (for example, 5.5 mmHg / sec), and outputs it to the pressurization control unit 115 (step ST5). The pressurization control unit 115 outputs a control signal to the pump drive circuit 53 so that the cuff pressure is pressurized at a constant speed according to the pressurization speed target (5.5 mmHg / sec). The pump drive circuit 53 outputs a drive signal (voltage signal) to the pump 51 so that the cuff pressure is pressurized at a constant pressurization speed target based on the control signal. Thereby, the cuff pressure is started at a constant pressure (step ST7).

After the start of constant velocity pressurization, the perimeter estimation unit 401 estimates the perimeter L of the measurement site according to the procedure described above (step ST9). Even during the estimation period, the cuff pressure is maintained at a constant speed (step ST11).

The constant speed pressurization is performed by feedback controlling the drive signal of the pump 51 as described above. In the process of feedback control, the target changing unit 114 sequentially inputs the driving voltage 511 of the pump 51, and the voltage value of the driving voltage 511 and a predetermined voltage value stored in the memory unit 42 (for example, the driving voltage upper limit 512 of the pump 51). ) And based on the comparison result, it is determined whether or not the condition (value of drive voltage 511> predetermined voltage value) is satisfied (step ST13).

If it is determined that the condition is not satisfied (NO in step ST13), the process proceeds to step ST19.

The blood pressure determination unit 117 determines the blood pressure according to the oscillometric formula based on the pulse wave amplitude input from the amplitude correction unit 113 and the cuff pressure detected by the pressure detection unit 112 in the constant pressure pressurization process. Since the blood pressure cannot be determined during a period when the pressure is not sufficiently increased (NO in step ST19), the process returns to step ST11, and the subsequent processes are repeated to proceed with constant velocity pressurization.

On the other hand, when the pressure is sufficiently increased and the blood pressure is determined (YES in step ST19), the decompression control unit 116 stops the pump 51 and outputs a control signal for opening the valve 52. Thereby, the air in the air bladder 21 is exhausted and the cuff pressure is reduced (step ST21). When the decompression control unit 116 determines that exhaust is completed based on the cuff pressure output from the pressure detection unit 112, the display control unit 120 displays the blood pressure and the pulse rate determined by the blood pressure determination unit 117 on the display unit 40 (step 40). ST23). The determined blood pressure and pulse rate are stored in the memory unit 42 together with the measurement time measured by the clock unit 45.

Returning to step ST13, when the target changing unit 114 determines that the condition (value of drive voltage 511> predetermined voltage value (value of drive voltage upper limit 512)) is satisfied (YES in step ST13), that is, the pump 51 It is determined that the output capacity has reached the upper limit (see time T in FIG. 7).

When the target changing unit 114 determines that the above condition is satisfied, the target changing unit 114 changes the pressurization speed target to a predetermined value (for example, 3.0 mmHg / sec) (step ST15). Then, constant speed pressurization by feedback control is continued using the pressurization speed target after the change. Thus, constant speed pressurization control is performed in a range where the output of the pump 51 has a margin. The change of the pressurization speed target may be performed a plurality of times, or when the pressurization speed falls below the lower limit value, the measurement may be stopped and an error may be displayed.

When the pressurization speed target is changed, the correction coefficient determination unit 402 searches the table TB based on the post-change pressurization speed target and the surrounding length L estimated in step ST9, and the corresponding correction coefficient. Read α. Using the read correction coefficient α, the pulse wave amplitude is corrected, and the corrected pulse wave amplitude is output to the blood pressure determining unit 117 (step ST17). Thereby, the blood pressure determination unit 117 determines the blood pressure using the corrected pulse wave amplitude and the cuff pressure. Thereafter, similarly to the above, the processes after step ST19 are repeated.

According to the present embodiment, correction is performed by eliminating an error that occurs in the pulse wave amplitude due to a change in the constant speed pressurization speed due to the change in the pressurization speed target, and the blood pressure is corrected using the pulse wave amplitude after correction. Therefore, accurate blood pressure measurement can be performed.

(Embodiment 2)
In the above-described first embodiment, the timing for changing the pressurization speed target by resetting is determined based on the drive voltage 511 of the pump 51. However, as in the second embodiment, pressurization is performed. It may be determined on the basis of the timing at which the pulse wave is detected after starting the operation. Also in the present embodiment, the pressurization speed is controlled at a constant speed within a range where the condition of (drive voltage 511 ≦ drive voltage upper limit 512) is satisfied, that is, within a range where the output of the pump 51 has a margin.

FIG. 11 is a diagram illustrating the timing at which a pulse wave is detected in the pressurizing process according to the second embodiment. 11A and 11B show a change in the driving voltage 511 over time in the pressurization process and a change in the cuff pressure on which the pulse wave is superimposed.

As shown in FIG. 11A, in the case of a subject whose blood pressure is relatively low, the range of cuff pressure at which the pulse wave appears in the pressurizing process of constant velocity pressurization is low. In some cases, blood pressure measurement can be completed without changing the pressure speed target.

On the other hand, as shown in FIG. 7, in the case of a subject whose blood pressure is relatively high, it is necessary to change the pressurization speed target within the range of the cuff pressure at which the pulse wave appears, and the pulse wave amplitude Correction is required. Therefore, when it is predicted that the blood pressure of the measured person is high and the pressurization speed target needs to be changed within the range of the cuff pressure at which the pulse wave appears, a low pressure is applied in advance as shown in FIG. By starting the measurement with the pressure speed target, the blood pressure can be determined by constant speed pressurization without changing the pressurization speed target, that is, without correcting the pulse wave amplitude.

FIG. 12 is a functional block diagram showing a functional configuration of the electronic blood pressure monitor 100A according to the present embodiment. The functional configuration is indicated by using the functions of the CPU 10 and its peripheral part.

2 is different from the functional configuration in FIG. 2 in that the electronic blood pressure monitor 100A in FIG. 12 includes a target changing unit 114A in place of the target changing unit 114. The target changing unit 114A inputs the cuff pressure detected by the pressure detecting unit 112. The target changing unit 114A includes a pulse wave counting unit 121 that counts the number of pulse waves output from the pulse wave detecting unit 118, and changes the pressurization speed target based on the count value.

FIG. 13 is a processing flowchart of blood pressure measurement according to the present embodiment. The program according to this flowchart is stored in advance in the memory unit 42, read from the memory unit 42 by the CPU 10, and executed. The blood pressure measurement process according to the present embodiment will be described with reference to the flowchart of FIG.

First, in steps ST1 to ST11, the same processing as in FIG. 10 is performed.
Thereafter, the target changing unit 114A compares the cuff pressure detected by the pressure detecting unit 112 with a predetermined value (for example, 50 mmHg), and determines whether or not it is larger than the predetermined value based on the comparison result (step ST13a). If it is determined that the cuff pressure is equal to or lower than the predetermined value (NO in step ST13a), the process proceeds to step ST19. If it is determined that the cuff pressure is greater than the predetermined value (YES in step ST13a), blood pressure high / low screening is performed (step ST13b).

Specifically, the pulse wave counting unit 121 counts a pulse wave detected after starting pressurization, and the target changing unit 114A compares the count value with a predetermined value (for example, 2 beats), and compares It is determined whether it is larger than a predetermined value based on the result (step ST13b).

If it is determined that the detected pulse wave number is equal to or less than the predetermined value (NO in step ST13b), it is estimated that the person to be measured has high blood pressure, and thus the target changing unit 114A changes the pressurization speed target. (Step ST13c, Step ST15). For example, the pressurization speed target is reduced to a predetermined value (for example, 3.0 mmHg / sec) (step ST15), and constant pressure pressurization is executed using the post-change pressurization speed target. Thus, constant speed pressurization control is performed in a range where the output of the pump 51 has a margin.

When the pressurization speed target is changed, the amplitude correction unit 113 corrects the pulse wave amplitude in the same manner as described above, and the blood pressure determination unit 117 performs processing for blood pressure determination using the corrected pulse wave amplitude. (Step ST17). Thereafter, processing similar to that described above (step ST19 to step ST23) is performed.

Returning to step ST13a and step ST13b, the pressurization speed target is changed while the count value of the pulse wave is determined to be equal to or less than the predetermined value during the period when the cuff pressure is less than the predetermined pressure (YES in step ST13a, YES in step ST13b). The constant speed pressurization proceeds without being performed.

It should be noted that instead of performing the blood pressure high / low screening, the measurement subject may input information indicating whether the blood pressure is high or low from the operation unit 41 in advance. Alternatively, the blood pressure measured in the past of the measurement subject may be read from the memory unit 42, compared with the reference blood pressure, and based on the result, it may be determined whether the blood pressure is high or low.

Here, the number of pulse waves detected in the range where the cuff pressure becomes 50 mmHg after the start of pressurization is counted, but the predetermined range of the cuff pressure to be counted is not limited to this range.

According to this embodiment, the level of the blood pressure of the measurement subject is estimated based on the pulse wave number detected in a relatively early period from the start of pressurization, and the pressurization speed target is changed based on the result. Thus, in the case of a subject whose blood pressure is relatively high, by changing to a low pressure target in a relatively early period from the start of pressurization and performing constant speed pressurization, The blood pressure can be determined without changing the pressure speed target, that is, without correcting the pulse wave amplitude.

(Embodiment 3)
In the above-described first and second embodiments, the pressure target after the change to be reset is a fixed value of a predetermined value (for example, 3.0 mmHg / sec). However, as in the present third embodiment, The length L may be changed variably. That is, since the capacity of the cuff 20 increases as the peripheral length L of the measurement site increases, the pump 51 is required to have a high output (a large discharge amount). Therefore, in order to pressurize at a constant speed with a limited discharge amount, it is desirable to determine the pressurization speed target based on the peripheral length L.

In the present embodiment, the pressurization speed is controlled at a constant speed as long as the condition (driving voltage 511 ≦ driving voltage upper limit 512) is satisfied, that is, the output of the pump 51 has a margin.

FIG. 14 is a functional block diagram showing a functional configuration of the electronic sphygmomanometer 100B according to the third embodiment. The functional configuration is indicated by using the functions of the CPU 10 and its peripheral part.

FIG. 15 is a diagram showing a table TB1 for determining a pressurization speed target according to the present embodiment. Referring to FIG. 14, the difference from the functional configuration of FIG. 2 is that electronic blood pressure monitor 100 </ b> B includes target changing unit 114 </ b> B instead of target changing unit 114. The target changing unit 114B inputs the peripheral length L estimated by the peripheral length estimation unit 401, searches the table TB1 of FIG. 15 based on the peripheral length L, and determines the pressure target after the change. Have

The table TB1 is stored in the memory unit 42 in advance. When changing the pressurization speed target in the pressurization process, the target determining unit 122 searches the table TB1 based on the estimated peripheral length L and reads the corresponding pressurization speed v. The target changing unit 114B determines the read pressurization speed v as the post-change pressurization speed target.

The target determining unit 122 may be included in the target changing unit 114A of the electronic sphygmomanometer 100A of FIG.

Thereby, the pressurization speed target can be set according to the peripheral length L of the measurement site, and constant pressure can be applied.

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.

20 cuff, 51 pump, 52 valve, 53 pump drive circuit, 54 valve drive circuit, 100, 100A, 100B electronic sphygmomanometer, 111 drive control unit, 112 pressure detection unit, 113 amplitude correction unit, 114, 114A, 114B target change 115, pressurization control unit, 116 decompression control unit, 117 blood pressure determination unit, 118 pulse wave detection unit, 119 memory processing unit, 120 display control unit, 121 pulse wave count unit, 122 target determination unit, 401 circumference length estimation unit 402, correction coefficient determination unit, 432, 433, TB1 table, 511 drive voltage, 512 drive voltage upper limit.

Claims

A cuff (20) wound around the measurement site of the measurement subject;
An adjustment unit (30) for adjusting the pressure in the cuff by controlling a pump for supplying fluid into the cuff;
A control unit that controls the adjustment unit so that the pressure in the cuff is pressurized at a constant speed according to a pressurization speed target during blood pressure measurement;
A pressure detector (112) for detecting a cuff pressure representing the pressure in the cuff;
A pulse wave detector (118) for detecting a pulse wave superimposed on the cuff pressure;
A blood pressure calculator for calculating blood pressure based on the detected cuff pressure and the pulse wave amplitude;
A target changing unit that variably changes the pressurization speed target,
The blood pressure calculation unit
An electronic sphygmomanometer that changes the pulse wave amplitude so as to correct an error in the pulse wave amplitude due to the change in the pressurization speed target, and calculates the blood pressure based on the cuff pressure and the changed pulse wave amplitude.
The blood pressure calculation unit
A coefficient determination unit for determining a coefficient for the correction based on the pressurization speed target before and after the change,
The electronic sphygmomanometer according to claim 1, wherein the pulse wave amplitude after change is calculated from the pulse wave amplitude before change using the determined coefficient.
The coefficient determination unit
The electronic sphygmomanometer according to claim 2, wherein the coefficient is determined based on a ratio between a pressurization speed target before the change and a pressurization speed target after the change.
A peripheral length acquisition unit that acquires the peripheral length of the measurement site is provided,
The coefficient determination unit
The electronic sphygmomanometer according to claim 3, wherein the coefficient is determined based on the acquired peripheral length and a ratio between the pressurization speed target before the change and the pressurization speed target after the change.
The electronic blood pressure monitor according to any one of claims 1 to 4, wherein the target changing unit variably changes the pressurization speed target within a range in which the pump can output.
Obtain information indicating the blood pressure level of the person being measured,
The target changing unit
The electronic sphygmomanometer according to claim 1, wherein the pressurization speed target is changed based on the acquired information.
The information indicating the level of the blood pressure of the measurement subject is acquired based on the number of pulse waves detected by the pulse wave detection unit in a period in which the cuff pressure in a predetermined range is detected after the start of pressurization. The electronic sphygmomanometer described in 1.
A peripheral length acquisition unit that acquires the peripheral length of the measurement site is provided,
The target changing unit
The electronic sphygmomanometer according to claim 1, wherein the pressurization speed target is changed based on the acquired peripheral length.