JP3445655B2 - Blood pressure monitoring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood pressure monitoring device for monitoring the blood pressure value of a living body without imposing a heavy load.

[0002]

2. Description of the Related Art When continuously monitoring a blood pressure value of a living body, an automatic blood pressure measuring device having a cuff wound around a part of the living body is used, and the blood pressure measurement by the automatic blood pressure measuring device is performed at a predetermined cycle. In many cases, the blood pressure value is measured by starting it repeatedly. However, in such a case, if the measurement interval is shortened in order to improve the accuracy of blood pressure monitoring, the frequency with which the cuff is pressed against the living body becomes high, so that there is a drawback that a large burden is imposed on the living body.

On the other hand, a cuff attached to a part of a living body is pressurized to a predetermined value, a pulse wave which is a pressure vibration generated in the cuff is detected, and a blood pressure value is determined based on the magnitude of the pulse wave. An apparatus for monitoring blood pressure by estimating has been proposed. For example, those described in JP-A-61-103432 and JP-A-60-241422.

[0004]

However, in the above-mentioned conventional blood pressure monitoring apparatus, if the pressure of the cuff is set as low as possible in order to reduce the burden on the living body, the pulse wave amplitude corresponding to the change in the blood pressure value is changed. In some cases, changes did not appear easily, and sufficient blood pressure monitoring accuracy could not be obtained. That is, the pulse wave amplitude obtained from the cuff changes with the pressure of the cuff at a predetermined normal blood pressure value, for example, like the envelope curve of the pulse wave amplitude shown by the solid line in FIG. Since it has the property of changing like the envelope of the pulse wave amplitude shown by the broken line of 8,
When detecting the pulse wave amplitude with the pressure of the cuff set relatively low as shown by P _K in FIG. 8, there is little change in the amplitude with respect to the change in blood pressure value, so at such a low set pressure P _K. When monitoring blood pressure, sufficient accuracy could not be obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a blood pressure monitoring device which can obtain high blood pressure monitoring accuracy without imposing a burden on a living body.

[0006]

The gist of the present invention for achieving the above object is to monitor the blood pressure value of a living body by changing the compression pressure of a cuff wound around a part of the living body. In the blood pressure monitoring device, (a) a pulse wave detecting means for detecting a pulse wave generated in the cuff when the cuff is compressed, and (b) the compression pressure of the cuff at a predetermined rest period. Compression pressure control means for repeatedly changing to a predetermined pressure value lower than the average blood pressure value of the living body, (c)
When the compression pressure of the cuff is changed by the compression pressure control means, by the envelope and the baseline connecting the amplitude value of the pulse wave within the preset pressure range of the cuff lower than the average blood pressure value of the living body. An area shape ratio calculation means for calculating the area shape ratio of the enclosed area, and (d) an abnormality for determining an abnormal decrease in the blood pressure value of the living body based on the change of the area shape ratio calculated by the area shape ratio calculation means. And a deterioration determining means.

[0007]

With this configuration, when the compression pressure of the cuff is changed by the compression pressure control means, the amplitude value of the pulse wave is connected within the preset pressure range of the cuff lower than the average blood pressure value of the living body. The area shape ratio of the area surrounded by the envelope and the base line is calculated, and by the abnormal decrease determination means,
The abnormal decrease in blood pressure value of the living body is determined based on the change in the area shape ratio calculated by the area shape ratio calculating means.

[0008]

According to the blood pressure monitoring apparatus of the present invention, therefore, the rate of change on the low pressure side of the envelope representing the change in the amplitude of the pulse wave due to the change in the pressure of the cuff changes in response to the change in the blood pressure value. Since blood pressure is monitored using this, high monitoring accuracy can be obtained. Further, since the above-mentioned rate of change is obtained by changing the pressure of the cuff in the low pressure region from the atmospheric pressure to the predetermined pressure value, the burden on the living body is not imposed.

[0009] Preferably, when the abnormal decrease determining means determines that the blood pressure of the living body is abnormally decreased, the blood pressure of the living body is automatically measured according to a series of predetermined measurement operations. Blood pressure measuring means is included. In this way, the blood pressure value when the blood pressure is abnormally lowered is measured by the blood pressure measuring means, so that there is an advantage that an accurate blood pressure value can be immediately obtained and an appropriate treatment can be performed.

Further, preferably, the pulse rate change value calculating means for calculating a change value of the pulse rate of the living body when the area shape ratio calculating means calculates the area shape ratio, and the abnormal decrease in blood pressure value. When the determination reference value for determination is R ^* and the change value of the pulse wave number is ΔPR, the determination reference value R ^* is based on the actual change value ΔPR of the pulse wave number from the following equation (1) stored in advance ^. Determination criterion value calculating means for calculating the abnormality is determined, and the abnormality reduction determining means determines the abnormality based on that the area shape ratio exceeds the determination reference value R ^* calculated by the determination criterion value calculating means. It is configured to make a drop determination. When the blood pressure value of the living body is lowered, such as in a shocked state of the living body, since the envelope representing the change of the amplitude of the pulse wave accompanying the pressure change of the cuff becomes flat, the pulse wave with respect to the change of the compression pressure of the cuff. Although it is not easily determined based on the rate of change of the size of, the area shape ratio of the area surrounded by the envelope and the base line in a predetermined cuff pressure range lower than the average blood pressure value of the living body is thus obtained. By monitoring the actual area-to-shape ratio in relation to the pulse rate by utilizing the phenomenon that the rate of change in pulse rate decreases with decreasing blood pressure, and the rate of change in pulse rate decreases with decreasing blood pressure. That is, there is an advantage that the shock state of the living body can be determined with high accuracy.

[0011]

## EQU1 ## R ^* = k ₁ .ΔPR + k ₂ (1) (where k ₁ and k ₂ are constants)

Further, preferably, the pulse rate change value calculating means includes pulse rate detecting means for detecting the pulse rate of the living body when the compression pressure of the cuff is changed by the compression pressure control means, The difference between the latest pulse rate detected by the pulse rate detection means and the pulse rate detected before that,
It is configured to be calculated as the pulse rate change value. At this time, an average value of the pulse rate detected by the pulse rate detection means is calculated by the compression pressure control means based on a plurality of pulse wave intervals generated during the change of the compression pressure of the cuff. By doing this, the effect of noise is mitigated,
Blood pressure monitoring accuracy is improved.

Further preferably, the compression pressure control means raises the compression pressure of the cuff to a predetermined first holding pressure, holds the holding pressure for a predetermined holding period, and then is higher than the first holding pressure. The pressure is raised to a second holding pressure that is predetermined as a value and is held for a predetermined holding period, and the area shape ratio calculating means is configured to hold the first holding pressure and the second holding pressure during the holding period. The area shape ratio of the pulse wave is calculated based on the amplitude of each detected pulse wave. By doing so, the area-to-shape ratio is calculated based on the amplitude of the pulse wave without distortion detected at each of the predetermined constant first and second holding pressures,
There is an advantage that the area shape ratio is accurately determined and the blood pressure monitoring accuracy is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A blood pressure monitoring apparatus according to an embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, a cuff 10 wound around an upper arm of a living body is compressed, and an inflatable bag 10a made of an elastic film such as a rubber sheet or a vinyl sheet does not expand and contract. It is configured by being housed inside. Inflatable bag 10a of this cuff 10
Is a pressure sensor 12, an air pump 14, a pressure control valve 16
And the air pipe 18 are connected.

The pressure sensor 12 has, for example, a semiconductor pressure detecting element, detects the pressure in the cuff 10, and supplies a pressure signal SP representing the pressure to the low pass filter 20 and the band pass filter 22. The low-pass filter 20 discriminates the DC component contained in the pressure signal SP to take out the pressure (static pressure) P _C of the cuff 10, and outputs it to the A / D converter 24 as a cuff pressure signal SK. Further, the bandpass filter 22 discriminates a frequency component of, for example, 1 to 10 Hz included in the pressure signal SP, extracts a pulse wave component, and outputs the pulse wave signal SM1 to the A / D converter 24. Cuff 1 wrapped around the upper arm of a living body
At 0, a pressure fluctuation synchronized with the heartbeat is generated based on the pulsation of the artery.

The band-pass filter 22 is a gradual pressure change (2 to 3 mm / H) of the pressure of the cuff 10 for blood pressure measurement.
g) has a narrow frequency characteristic for the purpose of extracting the pressure vibration, that is, the pulse wave amplitude generated in the cuff 10 in synchronization with the heartbeat without the influence of noise such as motion artifact noise. The above A / D converter 2
4 includes a multiplexer that time-divisions the above two types of input signals, and has a function of A / D converting the two types of input signals in parallel. The bandpass filter 22 corresponds to a pulse wave detecting means 50 described later.

The arithmetic and control unit 26 includes a CPU 28 and a RAM.
The CPU 28 is a so-called microcomputer including the ROM 30, the output interface 34, and the display interface 36. The CPU 28 stores the signal input from the A / D converter 24 in the ROM 32 in advance while using the temporary storage function of the RAM 30. Process according to the program
The air pump 14 and the pressure control valve 16 are drive-controlled via the output interface 34, and the display 38 is drive-controlled via the display interface 36.
The display 38 is provided with an image display plate capable of displaying numerical values and waveforms by a large number of pixels, and is also equipped with a printing machine capable of displaying numerical values and waveforms on paper with ink as required. In this embodiment, the display 38
Corresponds to the display means 68 described later.

The mode changeover switch 40 is operated to switch between the once measurement mode and the continuous monitoring mode, and selectively supplies a signal instructing the once measurement mode or the continuous monitoring mode to the CPU 28. Further, the start / stop switch 42 supplies the CPU 28 with a signal for alternately instructing start and stop for each pressing operation.

FIG. 2 is a functional block diagram for explaining a main part of the control function of the arithmetic and control unit 26. The blood pressure monitoring device shown in the figure is a pulse wave detecting means 50 for detecting a pulse wave which is a pressure signal generated in the cuff 10 in synchronization with a heartbeat when the cuff 10 wound around a part of a living body is compressed, and Cuff 1
It is provided with a so-called oscillometric blood pressure measuring means 52 for measuring the blood pressure value of the living body based on the change in the amplitude Am of the series of pulse waves obtained when the compression pressure of 0 is changed. The blood pressure measuring means 52 immediately performs blood pressure measurement at every preset measurement cycle and also when the abnormal lowering determination means 58 described later determines that the blood pressure of the living body is abnormally low.

As shown in FIG. 6, the compression pressure control means 54 sets the target pressure P which is set so that the compression pressure of the cuff 10 is higher than the maximum blood pressure of the living body during the blood pressure measurement period of the blood pressure measurement means 52.
After the pressure is rapidly increased to _CM , the pressure is gradually decreased at a rate of about 2 to 3 mm / Hg, while the pressure of the cuff 10 is lower than the average blood pressure of the living body during the non-measurement period when the blood pressure measuring means 52 does not measure blood pressure. The pressure is repeatedly changed to a low predetermined pressure value P _{CH with a} predetermined rest period T _1M . The area / shape ratio calculating means 56 controls the cuff 1 by the compression pressure controlling means 54.
When the compression pressure of 0 is changed, an envelope H connecting the amplitude values of the pulse waves within a preset pressure range of the cuff 10 lower than the average blood pressure value of the living body and a baseline showing the compression pressure of the cuff 10. The area shape ratio of the area surrounded by the shaded area in the two-dimensional coordinate composed of the abscissa (baseline) showing the compression pressure of the cuff 10 and the ordinate showing the relationship with the pulse wave amplitude shown in FIG. Calculate R _AREA .

The abnormality drop judging means 58, based on the determined area shape ratio R _AREA by the area shape ratio calculating means 56, the pulse calculated preferably by the area shape ratio R _AREA and pulse rate change value calculating means 60 The abnormal decrease in the blood pressure value of the living body is determined based on the number change value ΔPR. The pulse rate change value calculation means 60 is a pulse wave detection means in the process of changing the compression pressure of the cuff 10 to a predetermined pressure value P _CH lower than the average blood pressure value of the living body by the compression pressure control means 54 during the non-measurement period. The pulse rate PR of the living body is calculated from the interval of the pulse waves detected by 50, and the pulse rate PR _n-1 obtained when the compression pressure of the cuff 10 was changed last time or a plurality of m times before The change value Δ of the pulse rate based on the moving average value PR _ave (= PR _n-1 + ... PR _nm / m) of each calculated pulse rate and the pulse rate PR _n calculated this time.
The PR is calculated. Pulse rate change value calculation means 60
Is preferably a predetermined pressure value P _CH
The pulse rate detecting means 64 detects the pulse rate PR of the living body every time the pulse rate is changed, and the pulse rate moving average value calculating means 66 calculates the moving average value PR _ave .

When the blood pressure value is normal, an envelope H having a rising angle .alpha. On the low pressure side is formed as shown by the solid line in FIG. 8, but when the blood pressure value decreases, 1 in FIG.
Since the whole value of the envelope H is low and the peak moves to the low pressure side as shown by the dashed line, the envelope is accompanied by the decrease of the blood pressure value as shown by the rising angle β of the envelope H of the one-dot chain line. Since the rising angle of the line H on the low pressure side is larger than the angle α at the time of normal blood pressure, on the low pressure side of the envelope H, the envelope H in the preset cuff pressure range.
The area shape ratio R _AREA of the area surrounded by and the base line (the horizontal axis indicating the compression pressure of the cuff 10) also becomes large. Utilizing such a property, the abnormal decrease determination means 58 determines an abnormal decrease in the blood pressure value based on the area shape ratio R _AREA . For example, the abnormal decrease determination means 58 uses the pulse wave area change rate R
_{When AREA} becomes larger than the predetermined judgment reference value R ^* , it is judged that the blood pressure value of the living body is abnormally lowered. When the abnormal decrease determination means 58 determines that the biological blood pressure value is abnormally decreased, the abnormality content is displayed by the display means 68.
Is displayed in.

Here, the judgment reference value R ^* may be a preset constant value, but it is preferable that the judgment reference value calculation means 62 calculates the pulse rate from the previously stored equation (1). It is calculated based on the change value ΔPR of the pulse wave number calculated by the change value calculating means 60.

Further, the compression pressure control means 54 preferably increases the compression pressure of the cuff 10 to a predetermined first holding pressure P _CH1 and holds it for a predetermined holding period, and then the first holding pressure P _CH1. The pressure is raised to a predetermined second holding pressure P _CH2 higher than the pressure P _CH1 and held for a predetermined holding period. The area shape ratio calculation means 56 then determines the first holding pressure P _{CH 1}
The area shape ratio R _AREA is calculated based on the amplitudes Am ₁ and Am ₂ of the pulse waves detected during the holding period and the holding period of the second holding pressure P _CH2 , respectively.

3 and 4 show the arithmetic and control unit 26.
6 is a flowchart illustrating a control operation of the above. In step S1 in the figure, it is determined based on a signal from the start / stop switch 42 whether or not the start of the blood pressure monitoring device has been operated. If the determination in step S1 is negative, the process is put on standby, but if the determination is affirmative, in step S2 the cuff 1 is operated by the air pump 14 and the pressure control valve 16.
0 is quickly boosted.

In the following step S3, it is determined whether or not the cuff pressure P _C has reached a preset target pressure P _CM, for example, 180 mmHg. If the determination in step S3 is negative, steps S2 and subsequent steps are repeatedly executed, but if the determination is positive, the air pump 14 is stopped and the opening degree of the pressure control valve 16 is controlled in step S4. As a result, the gradual exhaust of the cuff 10 is started, and the cuff pressure is gradually reduced at a speed suitable for blood pressure measurement, for example, 2 to 3 mmHg / sec. Then, in step S5,
Whether or not one pulse wave is input is determined based on the pulse wave signal SM1. If the determination in step S5 is negative, steps S4 and thereafter are repeatedly executed.

However, if the determination in step S5 is affirmative, the blood pressure value determination routine by the oscillometric blood pressure value determination algorithm is executed in step S6, and then the blood pressure value determination is completed in step S7. It is determined whether or not. In the process of gradually reducing the pressure of the cuff 10 in the blood pressure measurement period, the pulse wave amplitude based on the pulse wave signal SM1 initially increases gradually as shown by the envelope H of the pulse wave amplitude in FIG. In the above blood pressure value determination algorithm, for example, the cuff pressure value when the amplitude of the pulse wave sharply decreases is the maximum blood pressure value P.
_sys , the cuff pressure value when the amplitude of the pulse wave is maximum is determined as the average blood pressure value P _mean , and the cuff pressure value when the amplitude of the pulse wave is rapidly increased is determined as the minimum blood pressure value P _dia .

If the determination in step S7 is negative, steps S4 and thereafter are repeatedly executed, but if the determination is affirmative, the blood pressure values P _{sy s} , P _mean , and P _dia are RAM 30 in step S8. In step S9, the pressure control valve 16 is opened, the cuff 10 is rapidly evacuated, and the compression by the cuff 10 is released. In the present embodiment, the above steps S2 to S9 correspond to the blood pressure measuring means 52 which automatically executes the blood pressure measurement according to a series of procedures.

Then, in step S10, it is judged based on the signal from the mode changeover switch 40 whether or not the continuous monitoring mode is set. If the determination in step S10 is negative, the one-time measurement mode is in effect, so this routine is ended, and steps S1 and thereafter are executed again. However, if the determination in step S10 is affirmative, that is, in the continuous monitoring mode, the blood pressure monitoring routine from step S11 onward is repeatedly executed at a predetermined cycle of about 1 to 3 minutes.

Second in steps S11 and S12
Timer counter T ₂ and first timer counter T ₁
The contents of each are cleared and step S1
After the 3 "1" to the contents of the first timer counter T ₁ and the second timer counter T ₂ are respectively added, the first timer in step S14 the counter T ₁
It is determined whether or not the content of has reached a preset determination reference value T _1M . This judgment reference value T _1M is set to a cycle, for example, about 1 to 5 minutes, in which the pressure of the cuff 10 is raised to a preset holding pressure P _CH, for example, about 60 mmHg for monitoring blood pressure during the non-blood pressure measurement period. It is set in advance.

Initially, the determination at step S14 is negative, so steps S13 and thereafter are repeatedly executed. However, when the determination in step S14 is affirmed while the step is repeatedly executed, the pressure in the cuff 10 is increased by the air pump 14 and the pressure control valve 16 in step S15. This gradual boost rate is
It is set so that a pulse wave of 4 beats or more is generated at least until the pressure of the cuff 10 reaches the holding pressure P _CH , and for example, a value of about 10 mmHg / sec is adopted. Next, in step S16, every time a pulse wave is generated, the amplitude Am of the pulse wave is calculated and is sequentially stored together with the cuff pressure at the time of the pulse wave generation and the generation time.

Next, in step S17, the cuff pressure P _C
Has reached a preset pressure value P _CH . The pressure value P _CH is set to a pressure sufficiently lower than the average blood pressure value P _{mean and} a constant pressure at which a change in pulse wave amplitude can be sufficiently recognized, for example, a pressure of about 60 mmHg. If the determination in step S17 is negative, steps S15 and below are executed again, but if the determination is affirmative, the gradual pressure increase of the cuff 10 is stopped in step S18, and the cuff 10 reaches the atmospheric pressure. It is exhausted.

The following step S19 corresponds to the area / shape ratio calculating means 56, in which step S16 is performed when the cuff 10 is depressurized to the pressure value P _CH .
From the pulse wave amplitudes Am stored in step c and the cuff pressure at the time of the pulse wave generation, the two-dimensional coordinates of the horizontal axis (baseline) indicating the compression pressure of the cuff 10 and the vertical axis indicating the relationship between the pulse wave amplitudes are displayed. An envelope H passing through the pulse wave amplitude is formed, and the envelope H in the preset cuff pressure range, for example, 30 to 60 mmHg.
Area shape ratio R representing the shape of the area surrounded by and the base line
_AREA is calculated. For example, the envelope H formed above
At cuff pressure of 30 mmHg, pulse wave amplitude is Am ₃₀ ,
The pulse wave amplitude is Am ₄₀ when the cuff pressure is ₄₀ mmHg, the pulse wave amplitude is Am ₅₀ when the cuff pressure is ₅₀ mmHg, and the cuff pressure is 60 mmHg.
If the pulse wave amplitude at this time is Am ₆₀ , the area shape ratio R _AREA is calculated from the following equation (2).

[0035]

[ _Equation 2] R _AREA = (Am ₃₀ + Am ₄₀ + Am ₅₀ + Am ₆₀ ) / Am ₃₀ (2)

Then, in step S20 corresponding to the pulse rate detecting means 64, the pulse rate PR _n is calculated from the pulse wave generation time interval stored in step S16, and the pulse rate moving average value calculating means is calculated. At step S21 corresponding to 66, the moving average value PR _ave of respective calculated pulse rate PR _n-1 + ·· PR _nm before m times than the time _{(= PR n-1 + ··} PR nm / m) In step S22 corresponding to the pulse rate change value calculating means 60, the current pulse rate PR _n obtained in step S20 and the moving average value PR _ave obtained in step S21 up to the previous time are calculated. Based on this, the pulse rate change value ΔPR (= PR _n −PR _ave ) is calculated.

Then, in step S23 corresponding to the judgment reference value calculating means 62, for example, the judgment reference value R ^* is calculated based on the pulse rate change value ΔPR from the relationship of FIG. 5 showing the equation (1). It According to the research conducted by the present inventors, when the blood pressure value of the living body becomes low, the area shape ratio R _AREA
, While the pulse rate PR tends to decrease, the determination reference value R ^* is corrected according to the pulse rate change value ΔPR by using the above relationship to determine the decrease in blood pressure value. It improves accuracy.

Next, in step S24 corresponding to the abnormal drop determining means 58, it is determined whether the area shape ratio R _AREA obtained in step S19 exceeds the determination reference value R ^* obtained in step S23. To be done. If the determination in step S24 is affirmative, step S25
After the blood pressure lowering abnormality is displayed on the display 38 by executing, the step S2 and subsequent steps corresponding to the blood pressure measuring means 52 are executed, and the blood pressure value when the blood pressure lowering abnormality is determined is immediately measured. .

However, if the determination in step S24 is negative, the cuff 10 is exhausted in step S26 to release its pressure, and then the content of the second timer counter T ₂ is preset in step S27. It is judged whether or not the judgment reference value T _2M has been reached. This judgment reference value T _2M is a time interval for periodically executing the blood pressure measurement routine of step S2 and thereafter, and is appropriately set to a value of, for example, about 10 minutes to 30 minutes. Initially, the determination in step S27 is negative, so that steps S12 and thereafter are repeatedly executed. However, while such steps are repeatedly executed, the above step S
When the determination at 27 is affirmed, the steps S2 and thereafter are executed again.

Therefore, the above steps are repeated.
By performing the pressure of the cuff 10 as shown in FIG.
Can be changed. That is, performed in connection with the startup operation
The blood pressure measurement period is completed
During the blood pressure measurement period, the pressure of the cuff 10 is set to T
_1MPressure value P set lower than average blood pressure over time _CH
Is gradually increased until the
Area ratio R issued _AREABased on the
Is determined.

As described above, according to this embodiment, the compression pressure of the cuff 10 is changed to the pressure value P _CH set below the average blood pressure by the pump 14 and the pressure control valve 16 corresponding to the compression pressure control means 54. If so, the area shape ratio R _AREA is calculated in step S19 corresponding to the area shape ratio calculation means 56, and the abnormal decrease determination means 58 is calculated.
By the step S24 corresponding to
_An abnormal decrease in blood pressure in the living body is determined based on the change in _AREA . Therefore, according to the blood pressure monitoring device of the present embodiment, the change rate on the low pressure side of the envelope H representing the change in the amplitude of the pulse wave due to the pressure change in the cuff 10 changes in response to the change in the blood pressure value. Since blood pressure is monitored by using it, high monitoring accuracy can be obtained. Further, since the above-mentioned rate of change is obtained by changing the pressure of the cuff 10 in the low pressure region from atmospheric pressure to a predetermined pressure value, the living body is not burdened.

Further, in the present embodiment, when the abnormal decrease determination means 58 determines an abnormal decrease in the blood pressure value of the living body, the blood pressure measuring means 52 determines the blood pressure value of the living body according to a series of predetermined measurement operations. Since it is automatically measured, there is an advantage that an accurate blood pressure value at the time of blood pressure abnormality can be immediately obtained by the blood pressure measuring means 52 and an accurate treatment can be performed.

Further, in the present embodiment, in step S23 corresponding to the judgment reference value calculating means 62, the living body at the time when the area shape ratio R _AREA is calculated from the previously stored equation (1). The determination reference value R ^* is calculated based on the pulse rate change value ΔPR, and in step S24 corresponding to the abnormal decrease determination means 58, it is determined that the area shape ratio R _AREA exceeds the determination reference value R ^*. An abnormal decrease is determined. When the blood pressure value of the living body decreases, such as in a shocked state of the living body, the envelope H representing the change of the amplitude Am of the pulse wave accompanying the pressure change of the cuff 10 becomes flat, so that
Although it is not easily determined based on the rate of change in the magnitude of the pulse wave with respect to the change in the compression pressure of 0, the envelope H and the baseline in the predetermined cuff pressure range lower than the average blood pressure value of the living body Area shape ratio R of the area surrounded by
Utilizing the phenomenon that _AREA increases as blood pressure decreases and pulse rate change rate ΔPR decreases as blood pressure decreases,
By monitoring the actual area-to-shape ratio R _AREA in relation to the pulse rate, there is an advantage that the abnormal decrease in the blood pressure value of the living body, that is, the shock state of the living body can be determined with high accuracy.

Next, another control operation example of the arithmetic and control unit 26 will be described. In the following description, the same parts as those in the above-described embodiment will be designated by the same reference numerals and the description thereof will be omitted.

FIG. 9 shows steps S15 to S15 of FIG.
17 shows another routine that replaces 17. In step S17-1 of FIG. 9, the pressure of the cuff 10 is held at the preset first holding pressure P _CH1 . This first holding pressure P _CH1
Is a pressure that can be sampled for calculating the area shape ratio R _AREA on the low pressure side of the envelope H indicating the magnitude of the pulse wave in FIG. 7, and is set to, for example, about 30 mmHg. In a succeeding step S17-2, it is determined whether or not two pulse waves continuously input to read a pulse wave containing no noise have the same magnitude. This step S17-2
Further, in step S17-5 described later, since the pressure of the cuff 10 is constant, a more accurate pulse wave filtered by the bandpass filter 22 is used. This step S1
When the determination in 7-2 is denied, step S17 is performed again.
-1 is repeatedly executed, but if the result is affirmative, the amplitude values of the two pulse waves are first determined in step S17-3.
It is stored as the pulse wave amplitude Am ₁ .

In the following step S17-4, the pressure of the cuff 10 is held at the preset second holding pressure P _{CH 2} . The second holding pressure P _CH2 is a pressure at which a pulse wave larger than the pulse wave stored in step S17-3 for calculating the area shape ratio R _AREA can be collected, and is set to, for example, about 60 mmHg. . Next, also in step S17-5, it is determined whether or not the magnitudes of the two consecutively input pulse waves are the same. If the determination in step S17-5 is negative, the steps from step S17-4 are executed again, but if the determination is positive, the amplitude values of the two pulse waves are the pulse wave amplitudes in step S17-6. It is stored as Am ₂ . Then, in step S19 of the present embodiment, the area shape ratio R _AREA is simply calculated from the following equation (3) based on the pulse wave amplitude Am ₁ and the amplitude Am ₂ . FIG. 10 shows the pressure P _{C of the} cuff 10 changed by the above steps.

[0047]

[ _Equation 3] R _AREA = Am ₂ / Am ₁ ... (3)

According to this embodiment, in addition to the same effect as described above, the area shape ratio R _{AR EA} is calculated from the two pulse wave amplitudes Am ₁ and Am ₂ , so that the calculation is simple. There is an advantage to be.

Further, according to this embodiment, two similar pulse waves are held at the first holding pressure P _CH1 until the first pulse wave amplitude Am ₁ is stored, and then the second holding pressure P _CH1 is held. After the pressure is stepwise increased to P _CH2 , two similar pulse waves are generated and held at the second holding pressure P _CH2 until the second pulse wave amplitude Am ₂ is stored. Is advantageously removed.

Further, according to this embodiment, the compression pressure control is performed.
Steps S17-1 and S17 corresponding to the control means 54
-4 is a first holding that holds the compression pressure of the cuff 10 in advance.
Pressure P _CH1 After boosting to and holding for a predetermined holding period,
First holding pressure P of_CH1 The second protection preset to a higher value
Holding pressure P_CH2 Boosted to and held for a predetermined holding period
And the step S corresponding to the area shape ratio calculation means 56.
At 19, the first holding pressure P_CH1 Retention period and second
Holding pressure P_CH2 Pulse detected in each retention period
Wave amplitude Am₁And amplitude Am₂Area of envelope H based on
Shape ratio R_AREAIs configured to calculate
Constant first holding pressure P_CH1 And the second holding pressure P_CH2 That's it
Based on the amplitude of the undistorted pulse wave detected in
Product shape ratio R_AREAArea ratio R_AREABut
It has the advantage that it is accurately determined and the blood pressure monitoring accuracy is high.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can be applied to other modes.

For example, in the above-described embodiment, the compression pressure control
The pressure of the cuff 10 is changed to the pressure value P by the controlling means 54._CHHeading to
In the range of 30 to 60 mmHg during the process of gradually increasing the pressure
The pulse wave amplitude in the
Area ratio R of the low pressure side part of _AREAWas calculated,
The pressure of the cuff 10 is increased by the compression pressure control means 54.
Value P_CHThe pulse wave amplitude during the process
Area ratio R_AREAUsed to calculate
It may be done.

Further, the area shape ratio R of the above embodiment
_{The AREA} was calculated from the equation (2) or the equation (3), but the normalized area value may be used as the area shape ratio R _AREA .

The pressure value P _CH in the above-mentioned embodiment is 60 mm.
Although the pressure is set to about Hg, the pressure is not limited thereto, and if the pressure is lower than the average blood pressure value P _mean , a temporary effect is obtained. It is more preferable that the pressure is set to be lower than the minimum blood pressure value P _dia because the blood flow is not hindered.

Further, in step S20 of the above-described embodiment, the pulse rate is detected from the pulse wave which is the pressure oscillation of the cuff 10 for blood pressure measurement, but other photoelectric pulse waves, volume pulse waves, impedance pulse waves are detected. Alternatively, a pulse wave sensor or an electrocardiographic sensor for detecting an electrocardiographic signal may be provided and the pulse rate may be calculated from these signals.

The above description is merely an embodiment of the present invention, and the present invention can be variously modified without departing from the gist thereof.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a blood pressure monitoring device of the present invention.

FIG. 2 is a functional block diagram illustrating a main part of a control function of the arithmetic control circuit of FIG.

FIG. 3 is a flowchart illustrating a part of control operation of the arithmetic control circuit of FIG.

FIG. 4 is a flowchart illustrating a part of control operation of the arithmetic control circuit of FIG.

5 is a diagram showing relationships used in the flowchart of FIG.

FIG. 6 is a time chart explaining the pressure of the cuff changed by the control operation of FIGS. 3 and 4.

7 is a diagram illustrating an area shape ratio R _AREA calculated in the control operation of FIG.

FIG. 8 is a diagram illustrating an envelope H that connects amplitude values of pulse waves, which changes in association with changes in blood pressure values.

FIG. 9 is a flowchart illustrating a main part of an operation according to another embodiment of the present invention.

FIG. 10 is a time chart explaining the pressure of the cuff that is changed in the non-measurement period in order to monitor the abnormal blood pressure decrease by the control operation of the embodiment of FIG. 9.

[Explanation of symbols]

10: Cuff 50: Pulse wave detecting means 52: Blood pressure measuring means 54: Pressure control means 56: Area shape ratio calculation means 58: Abnormal drop determination means 60: means for calculating pulse rate change value 62: Judgment standard value calculation means 64: Pulse rate detecting means 66: Pulse rate moving average value calculation means

Claims (5)

(57) [Claims] 1. A blood pressure monitoring device for monitoring the blood pressure value of a living body by changing the compression pressure of the living body which is wound around a part of the living body, the pulse being generated in the cuff when the cuff is compressed. Pulse wave detection means for detecting a wave, compression pressure control means for repeatedly changing the compression pressure of the cuff to a predetermined pressure value lower than the average blood pressure value of the living body in a predetermined rest period, and the compression pressure When the compression pressure of the cuff is changed by the control means, it is surrounded by the envelope and the baseline connecting the amplitude values of the pulse wave within the preset pressure range of the cuff lower than the average blood pressure value of the living body. An area shape ratio calculating means for calculating an area shape ratio of the areas, and an abnormal decrease determining means for judging an abnormal decrease in the blood pressure value of the living body based on a change in the area shape ratio calculated by the area shape ratio calculating means, Including Blood pressure monitoring device according to claim and. 2. A blood pressure measuring means for automatically measuring the blood pressure value of the living body according to a series of predetermined measurement operations when the abnormal lowering judgment means judges an abnormal lowering of the blood pressure value of the living body. The blood pressure monitoring device according to claim 1, which includes: 3. A pulse rate change value calculation means for calculating a change value of the pulse rate of the living body when the area shape ratio calculation means calculates the area shape ratio, and for determining the abnormal decrease in blood pressure value. R ^*
When the change value of the pulse wave number is ΔPR, the change value of the actual pulse wave number is calculated from the following equation stored in advance: R ^* = k ₁ · ΔPR + k ₂ (where k ₁ and k ₂ are constants). A determination reference value calculating unit for calculating a determination reference value R ^* based on ΔPR, wherein the abnormality reduction determination unit determines that the area / shape ratio exceeds the determination reference value R ^*. The blood pressure monitoring device according to claim 1 or 2, which makes a determination. 4. The pulse rate change value calculation means includes pulse rate detection means for detecting the pulse rate of the living body when the compression pressure of the cuff is changed by the compression pressure control means, and the pulse rate detection means. 4. The blood pressure monitoring device according to claim 1, wherein a difference between the latest pulse rate detected by the means and the pulse rate detected before that is calculated as the pulse rate change value. 5. The compression pressure control means increases the compression pressure of the cuff to a predetermined first holding pressure and holds the pressure for a predetermined holding period, and then sets the value higher than the first holding pressure. The second holding pressure is increased and held for a predetermined holding period, and the area shape ratio calculating means detects the holding period of the first holding pressure and the holding period of the second holding pressure, respectively. The blood pressure monitoring device according to claim 1, wherein the area shape ratio is calculated based on the amplitude of the pulse wave.