JPH084575B2 - Electronic blood pressure monitor - Google Patents

Description

The present invention relates to an electronic sphygmomanometer, and more particularly to an electronic sphygmomanometer that extracts a pulse wave component of a blood vessel and determines blood pressure using the pulse wave component data as a parameter.

(B) Conventional technology In recent years, a photoelectric sensor consisting of a light emitting element and a light receiving element is attached to a substantially cylindrical pneumatic cuff, a finger is inserted into the cuff, and air pressure is supplied by a pump or the like into the cuff. Pressurize, pressurize the finger artery by this pressurization, for example, the cuff pressure is depressurized from the hemostasis state of the artery at a slow speed, and in the process, the pulse wave component of the blood vessel is detected by the photoelectric sensor, and its pulse wave information, An electronic sphygmomanometer for fingers has been proposed, which determines blood pressure such as systolic blood pressure and diastolic blood pressure from pulse wave amplitude and cuff pressure detected by a pressure sensor. In this type of electronic blood pressure monitor for a finger, a photoelectric sensor emits light from a light emitting element, the light is reflected by a finger and is received by a light receiving element. When the finger is in a hemostasis state, a fixed level (direct current) of reflected light is received by the light receiving element, but when blood begins to flow into the finger artery, the volume of the blood vessel changes due to the pulse wave and the amount of reflected light also pulsates. However, the output of the light receiving element is a direct current component with a pulse wave component superimposed. Only the pulse wave component is extracted from the output of the light receiving element, and its amplitude is stored in the storage means as data, for example, and this pulse wave amplitude is used as a parameter for blood pressure determination.

As shown in FIG. 7, the blood pressure determination algorithm uses SYS (maximum blood pressure) as the cuff pressure corresponding to the first pulse wave A ₁ obtained in the depressurization process of the cuff pressure, and corresponds to the maximum value Amax of the pulse wave amplitude. The cuff pressure is MAP (mean blood pressure), and DIA (minimum blood pressure) is calculated from = (3MAP-SYS) / 2. In the finger electronic sphygmomanometer of this type, the pulse wave amplitude data _{A 1, ‥‥, A i,} ‥‥, A n
Are quantized and stored in a memory in an MPU (microprocessor unit).

(C) Problems to be Solved by the Invention It is known that the maximum amplitude varies from person to person even if the pulse wave component is detected by the same pulse wave sensor to obtain the pulse wave amplitude. Since the conventional electronic blood pressure monitor for fingers stores the pulse wave amplitude in a fixed manner, if the resolution (quantization bit number) is adjusted to a person with a large pulse wave amplitude, it will be However, the accuracy deteriorates, and conversely, if the resolution of the pulse wave amplitude is small, there is a problem that the blood pressure cannot be measured because the range becomes overrange for a person with a large pulse wave amplitude.

In view of the above, the present invention provides an electronic sphygmomanometer that stores a pulse wave amplitude as a whole so that the pulse wave amplitude can be expanded and contracted as a whole, and can perform an appropriate measurement for both a person with a large pulse wave amplitude and a person with a small pulse wave amplitude. It is an object.

(D) Means and Actions for Solving Problems As shown in FIG. 1, the electronic sphygmomanometer of the present invention is a pulse wave for extracting the amplitude value of the pulse wave obtained from the living body when the cuff is pressurized or depressurized. The pulse extraction means E and the blood pressure determination means G for determining the blood pressure by using the pulse wave amplitude value extracted by the pulse wave amplitude extraction means E and the pressure value of the cuff by the pressure sensor C are provided. Data storage means F for sequentially storing each pulse wave amplitude value extracted by the wave amplitude extraction means E, and each time the pulse wave amplitude extraction means E extracts the pulse wave amplitude, the pulse wave amplitude value is below a predetermined value. Discrimination means H for discriminating whether or not there is a pulse wave amplitude value as it is when the discrimination result of the discrimination means H is less than or equal to a predetermined value.
If the judgment result exceeds a predetermined value,
By multiplying all the pulse wave amplitude values stored in the data storage means F by a predetermined coefficient less than 1 to update and store in the data storage means F, the pulse wave amplitude value and the pulse extracted thereafter are multiplied. A pulse wave amplitude value storage adjustment control means I for storing the wave amplitude value in the data storage means F by multiplying it by the predetermined coefficient is configured.

In this electronic sphygmomanometer, for example, in the depressurization process after pressurizing the cuff pressure to stop the arterial flow, the pulse wave component is detected by the pulse wave sensor, the pulse wave amplitude is extracted, and each value is sequentially stored in the data storage means. Remember. When storing, it is determined whether the pulse wave amplitude is less than or equal to a predetermined value. When the value is equal to or smaller than the predetermined value, it means that the data up to that point is stored at the predetermined resolution without being overranged, and the data is stored as it is. However, when the pulse wave amplitude exceeds a predetermined value, the pulse wave amplitude of the person is large, and if memory is continued as it is, there is a risk of overrange. Therefore, in this case, the pulse wave amplitude data up to that point are multiplied by a predetermined coefficient (for example, 0.5), each data is reduced as a whole, and updated and stored. After that, the data will be reduced at the same reduction ratio,
If the reduced pulse wave amplitude data still exceeds the predetermined value, the data is multiplied by the above coefficient to perform the second reduction. By such processing, even if a person has a large or small pulse wave amplitude, the degree of reduction is adjusted according to the magnitude, so that it is possible to always obtain appropriate pulse wave amplitude data that effectively uses the range.

(E) Examples The present invention will be described in more detail with reference to the following examples.

FIG. 2 is an external perspective view of a finger electronic blood pressure monitor showing an embodiment of the present invention. In the figure, a finger cuff 2 is attached to a main body case 1 and is configured to be openable and closable by a predetermined angle with a mounting point 2a as a fulcrum. Finger cuff 2 is finger cuff button 3
As shown in the figure, the tip 2b of the main body case 1
Away from it, making it easier to insert a long finger. A display 4, a power switch 5, and a start switch 6 are provided on the surface of the body case 1. An electronic circuit section, a pump, a motor for driving the pump, a power supply battery, and the like, which will be described later, are housed in the main body case 1.

In the finger cuff 2, as shown in FIGS. 3 (A) and 3 (B), the pressing band 8 is housed in the cylindrical base body 10, and
The periphery of 10 is held by a cuff holder 9.
The pressure belt 8 includes a pressure bag 83 having a rubber substrate 82 and a plurality of convex portions.
Are attached to form a plurality of air chambers 84, 84, ... And are housed in the above-mentioned base 10. The pulse wave is detected in the air chamber 84 of a part of the pressurizing band 8. Sensor (pulse wave sensor)
A light emitting element 15 and a light receiving element 16 are provided as described above, and although not shown, these are led out to the outside by a lead wire and connected to the main body circuit section. Also, the pressure belt 8
Air pressure is supplied to the inside of the container from a pump in the main body case 1 by a tube so that pressure can be applied.

In the finger cuff 2 of this embodiment, the light emitting elements 15 and 15 are provided in the air chambers on both sides of the light receiving element 16 for pulse wave detection, respectively. This is to prevent variations. Further, a light receiving element 18 is provided at a position facing the light receiving element 16. The light receiving element 18 is provided to detect the finger insertion.

FIG. 4 is a circuit block diagram of the finger electronic blood pressure monitor of the embodiment. When the power switch 5 is turned on, the power circuit 11
Power supply voltage is supplied to U12 and other electronic circuit parts, and under the command of MPU12, the motor drive circuit 25 is operated when required to rotate the pump motor 26,
Pressurize the pressure band 8 of the finger cuff 2 and, if necessary, MPU1
Under the command of 2, the quick exhaust valve drive circuit 27 is driven and the valve 28
Is opened, and the pressure of the pressure band 8 of the finger cuff 2 can be rapidly exhausted. Further, the air pressure in the pressurizing band 8 of the finger cuff 2 is gradually exhausted by the slow exhaust valve 29. The MPU 12 outputs a digital value indicating the light emission level of the light emitting element 15, converts it into an analog value by the D / A (digital / analog) converter 13, inputs a predetermined voltage to the LED drive circuit 14, and then the LED drive circuit. The light emitting element 15 is turned on by operating the light emitting element 14. In this embodiment, the command signal output from the MPU 12 causes the light emitting element 15 to be stepwise (for example, 5
It can be switched to level) to emit light. This is a function provided because it is necessary to set an appropriate level in order to correct the difference in the amount of reflected light absorbed by the light receiving element depending on the measurer.

The pressure of the finger cuff 2 is detected by the semiconductor pressure sensor 23, passed through the amplifier circuit 24 and the A / D converter 22, and taken into the MPU 12 for storage. On the other hand, the output of the light receiving element 16 of the photoelectric sensor is the buffer amplifier 19, the filter circuit 20, and the amplifier circuit 2.
1. Further, it is configured to be taken into the MPU 12 through the A / D converter 22 or directly through the A / D converter 22. The output of the light receiving element 16 directly goes through the A / D converter 22, and the MPU12
Is taken in to obtain the DC component of the output of the light receiving element 16, and the MPU 12 receives this DC component and switches the light emission level of the light emitting element 15 according to the value. On the other hand, the output of the light receiving element 18 for finger detection is also taken into the MPU 12.

The MPU 12 has a built-in memory 12a for storing data, and has a function of storing the cuff pressure corresponding to the amplitude of each pulse wave in the memory in the process of slowly reducing the cuff pressure. The MPU12 also has a function to compare with a predetermined value in the process of capturing the pulse wave amplitude, and when it determines that the pulse wave amplitude is larger than the predetermined value, it multiplies the data stored in the memory up to that point by 0.5 to reduce and update the data. And the function of determining SYS (maximum blood pressure) and DIA (minimum blood pressure) from the pulse wave amplitude and cuff pressure stored in the memory. The determined blood pressure value is displayed on the display 4.

Next, the operation of measuring blood pressure with the electronic blood pressure monitor for a finger of the above embodiment will be described.

First, as shown in FIG. 2, the push button 3 is operated to open the finger cuff 2 from the main body as shown in the drawing, and for example, the index finger is inserted into the finger cuff 2 as shown in the drawing. In this state, the power switch 5 is turned on.

When the power switch 5 is turned on, the processing operation of the MPU 12 starts, and as shown in FIG. 5 (A), first, all the segments of the display 4 are turned on [step ST (hereinafter referred to as ST) 1]. . Then, after turning off all the segments of the display 4 and checking the operation of the display 4 (ST2), the heart () mark of the display 4 is turned on (ST3). When this heart symbol is lit, it indicates that the electronic circuit section of the instrument is ready, and the measurer then turns on the start switch 6.
Yes (ST4). As a result, the determination of ST4 "whether the start switch has been pressed" becomes YES, and subsequently the heart mark on the display 4 is turned off (ST5). Then, it is determined whether or not the finger is inserted (ST6). This determination is based on the light emitting element 1
It is determined whether or not 5 is turned on and the light entering the light receiving element 18 is blocked. That is, when the measurer inserts his / her finger into the finger cuff, the light from the light emitting element 15 is blocked by the finger, and thus the insertion of the finger is detected. Second
When the finger is inserted as shown in the figure, this judgment is YE.
S, then the indicator 4 lights up an arrow (ST
7). This upward arrow is a display signifying the start of the pressurizing operation, and then the valve 28 is closed (ST8). afterwards,
The motor drive circuit 25 is operated to start the rotation of the pump motor 26 (ST9). Then, the maximum pressurizing time is set (ST10). This pressurization maximum time sets the time required for pressurization (eg 30 seconds). After the pressurizing operation is started, it is further determined in ST11 whether or not the finger is inserted again. If the finger is still inserted, the pressurization is continued as it is. If the finger is pulled out after pressurization, this judgment becomes NO and the operation moves to ST45 and an error message is displayed. Then, it is determined whether the cuff pressure is 170 mmHg or higher (ST12). In the initial pressurization state in which the cuff pressure has not reached 170 mmHg or more, the determination is NO, and then the process proceeds to ST44, where it is determined whether the maximum pressurization time is over. If the maximum pressurizing time is not exceeded, the process returns to ST11, that is, the pressurizing operation is continued. If 170mmHg is not reached even after pressurizing for the maximum time, such as when there is air leak in the cuff, move to ST45 and display an error message. In ST12, it is determined whether the cuff pressure has reached 170 mmHg or higher because this 170 mmHg is set as the pressurization target value. When the cuff pressure reaches 170 mmHg, the determination in ST12 becomes YES, the pump motor 26 is stopped here (ST13), and the upward arrow of the display 4 is turned off (ST14). This completes the pressurization, and then the LED (light emitting element) is turned on to detect the pulse wave.
Turn on the LED (ST15). Then, it is determined whether the pulse wave sensor, that is, the direct current (pulse wave) level detected by the light receiving element 16 is higher than a predetermined level (ST16). A high pulse wave level indicates a small amount of reflected light, and therefore
In this case, the LED lighting level is increased by one rank, that is, set to level 4 (ST17), and it is determined whether the pulse wave level is high (ST18). In ST18, if the pulse wave level is still high, raise the LED lighting level by one rank, that is, level 5
(ST19), and then in ST20, it is determined whether the pulse wave level is high. If it is still high here, there is no higher lighting level, and the process moves to ST46. If the pulse wave level is not high in ST20, it is determined that this lighting level is appropriate, and subsequent lighting is executed at the level 5.

On the other hand, when the pulse wave level is not high in ST16, that is, when the level 3 is turned on, it is determined whether or not the pulse wave level is low. If it is not low here, the pulse wave level is in the linear range, and the lighting level 3 is appropriate. Therefore, the process proceeds to ST26 in FIG. 5 (C). But ST21
If the pulse wave level is low at, light emitting element 15
The lighting level of is set to level 2, then it is determined whether the pulse wave level is low (ST23), and when the pulse wave level is low, the process proceeds to ST24 and the lighting level of the light emitting element 15 is set to level 1. Similarly, determine whether the pulse wave level is low (ST
twenty five). When the level is appropriate at the level 2 or the level 1, respectively, the light emitting element 15 is kept at that level as it is.
Keeps on. If the pulse wave level is still low in ST25, it is out of adjustment, and the process proceeds to ST36. This is shown in FIG. 5 (B).
The processes of ST15 to ST25 are processes of actually adjusting the lighting level of the light emitting element under the control of the MPU 12 to obtain the most appropriate pulse wave level with the finger inserted by the measurer.

If it is determined that the pulse wave level is appropriate, then the process proceeds to ST26 shown in FIG. 5 (C). This invention will be described below.
The processing of ST26 to ST38 is important.

In ST26, the output of this light-receiving element 16, i.e. the pulse wave level x _i and the previous pulse wave level x _i-1 of the difference x _i -x _i-1 is the predetermined value x
Determine if it is greater than _th . This determination is whether or not a pulse wave is generated, that is, the pulse wave is detected. When the cuff pressure is high and blood flow does not flow, pulse wave does not occur.
There is not so much difference between x _i and x _i-1 , and if the judgment in ST26 is NO, move to ST40, judge whether the cuff pressure is less than 20 mmHg, return to ST26 until the judgment is YES, and perform pulse wave detection processing. continue. Even if the cuff pressure becomes less than 20 mmHg, if the pulse wave is not detected, it is abnormal and the process moves from ST40 to ST43 to display an error on the display unit 4.

When x _i −x _i-1 > x _{th in} ST26, it means that the first pulse wave is detected, the process proceeds to ST27, and the timer T is set to 1.
Initialize the variable G to 0 and the variable j to 0. The variable G is used for calculating the coefficient of data reduction described later, the variable j indicates the pulse wave number, and the post-initialization timer T is 0.
It is judged whether or not it is larger than 3 (ST28), and again "x _i −x _i-1 > x
_The pulse wave is detected by determining " _th or" (ST29). Here, after waiting for 0.3 seconds, when 0.3 seconds has elapsed, ST.
The reason for leaving 3 seconds is to prohibit pulse wave detection during this period and prevent noise and the like from being detected as a pulse wave. ST29 is
If it is not YES, the pulse wave detection process is repeated until the cuff pressure becomes less than 20 mmHg (ST42). If the pulse wave is not detected even if the cuff pressure becomes less than 20 mmHg, it is abnormal and the process moves from ST42 to ST43 to display an error on the display unit 4.

In ST29, when x _i −x _i-1 > x _th , that is, when the next pulse wave is detected, the heart symbol lights on the display 4 for 0.2 seconds (S
T30), the timer T is set to 0, the pulse wave amplitude A the _{(X max -x min) / 2} G (ST31). Here, x _max is the maximum level in the pulse wave and x _min is the minimum level in the pulse wave. For G = ^0, 2 0 = 1 so the pulse wave amplitude A is initially x
Calculated as _max −x _min .

Subsequently, it is determined whether or not the pulse wave amplitude A this time is less than or equal to a predetermined value A _sup (ST32). The constant A _sup is set to determine the possibility that the range of the memory will be exceeded if the pulse wave amplitude is continuously captured as it is. The judgment of “A ≦ A _sup ” is YES.
In case of ST34, it means that the pulse amplitude is relatively small, and ST34
Then, the variable j is incremented by 1 and the pulse wave amplitude A is stored as A _j (ST34). Next, it is determined whether or not the current pulse wave amplitude A is larger than the maximum pulse wave amplitude A _max so far (ST35), and if so, the pulse wave amplitude A is updated and stored as the maximum pulse wave amplitude A _max. (ST36), move to ST37. If smaller, skip ST36 and move to ST37. In ST37, it is measured whether or not the pulse wave amplitude A this time is smaller than A _max / 2. If not, the process returns to ST28, and in the process after ST28, the next pulse wave detection and pulse wave amplitude calculation process is performed. To continue.

When the pulse wave amplitude of the measurer is large and the pulse wave amplitude A becomes larger than A _sup , the determination in ST32 is NO, then 1/2 of the current pulse wave amplitude A is set as the new pulse wave amplitude A, and , The pulse wave amplitude A _i (i = 1, 2, ...
Update and memorize as 1/2. In other words, 1/2 the pulse wave amplitude data
Shrink to. Further, the variable G is incremented by +1 in order to halve the pulse wave amplitude in the future. As a result, G = 1 (ST3
3). After the processing of ST33, the pulse wave amplitude A has been reduced to half of that at the time of detection, so the determination of ST32 is YES and the processing is ST3.
Then, the process proceeds to step 4, and after processing ST35 to ST37, returns to ST28. Since the calculation of the pulse wave amplitude A of ST31 after this is G = 1, A = (x
_max −x _min ) / 2.

In this way, when the pulse wave amplitude A exceeds A _Sup , the data is reduced and updated and stored, so no matter how large the pulse wave amplitude data is captured, it is automatically caught, The maximum amplitude is stored in the memory 12a without overranging.

When the pulse wave amplitude A becomes 1/2 or less of the maximum pulse wave amplitude A _max , S
The determination in T37 is YES, the blood pressure value is calculated in ST38, the pulse rate is further calculated (ST39), and the process proceeds to ST46. There are various blood pressure calculation algorithms. For example, the cuff pressure at the point where the pulse wave amplitude value is obtained is the systolic blood pressure SYS, and the cuff pressure at the point where the maximum pulse wave amplitude value is obtained is the average blood pressure MAP. And = (3MA
Processing such as setting P-SYS) / 2 as the diastolic blood pressure DIA is performed.
When an error occurs or the measurement ends, the pump motor 26 is stopped in ST46, the valve 28 is similarly opened to move to quick exhaust (ST47), the light emitting element 15 is turned off (ST48), and the downward arrow is turned on ( ST49). This downward arrow is a display that means quick exhaust. And the cuff pressure is 5m
If it is less than mHg (ST50), if it is less than 5 mmHg, the downward arrow is turned off (ST51), it is determined whether there is a measurement result, and if there is a normal measurement instead of an error, Display the measurement result in ST53 and return to ST3. If there is no measurement result, that is, if there is an error, go to ST3.
Return to and prepare for the next measurement.

In the above embodiment, the reduction ratio is set to 1/2, but this value may be appropriately set to any value smaller than 1.

Further, although the above embodiment has been described with respect to the finger electronic blood pressure monitor, the present invention can be applied to an arm electronic blood pressure monitor.

(F) Effect of the Invention According to the present invention, in storing the pulse wave amplitude data in the storage means, it is determined whether or not each pulse wave amplitude exceeds a predetermined value, and if it exceeds, the data is reduced. Since it is updated and stored, if the pulse wave amplitude is small in advance, it is set to have an appropriate range so that even a person with a large pulse wave amplitude can be reduced to an appropriate size and stored. Therefore, the blood pressure can be accurately measured regardless of the magnitude of the pulse wave amplitude.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electronic blood pressure monitor of the present invention, FIG. 2 is an external perspective view of an electronic blood pressure monitor for a finger according to the present invention, and FIG. 3 (A) is an example finger. Front view of the finger cuff of the electronic blood pressure monitor for medical use, FIG. 3 (B) is a sectional view of the finger cuff,
FIG. 4 is a circuit block of the electronic blood pressure monitor for the finger, FIG. 5 (A), FIG. 5 (B), FIG. 5 (C) and FIG. 5 (D).
FIG. 6 is a flow chart for explaining the operation of the electronic blood pressure monitor for the same finger, FIGS. 6 (a), (b), and (c) are diagrams for explaining the reduction storage operation of pulse wave amplitude data, and FIG. FIG. 6 is a diagram showing a relationship between a cuff pressure and a pulse wave amplitude in a process of slowly discharging a cuff. A: Cuff, B: Pneumatic system, C: Pressure sensor, D: Pulse wave sensor, E: Pulse wave amplitude extraction means, F: Data storage means, G: Blood pressure measurement means, H: Pulse wave amplitude determination means, I: Pulse wave amplitude memory adjustment control means.

Claims (1)

[Claims] 1. A pulse wave amplitude extracting means for extracting an amplitude value of a pulse wave obtained from a living body when the cuff is pressurized or decompressed, and a pulse wave amplitude value extracted by the pulse wave amplitude extracting means and a cuff by a pressure sensor. In an electronic sphygmomanometer including a blood pressure determining unit that determines a blood pressure using a pressure value, a data storage unit that sequentially stores each pulse wave amplitude value extracted by the pulse wave amplitude extracting unit, and the pulse wave amplitude extracting unit. Whenever the means extracts the pulse wave amplitude, the determining means determines whether or not the pulse wave amplitude value is less than or equal to a predetermined value, and if the determination result of the determining means is less than or equal to the predetermined value, the pulse wave The amplitude value is stored in the data storage means as it is,
When the determination result exceeds a predetermined value, all the pulse wave amplitude values stored up to that point in the data storage means are multiplied by a predetermined coefficient of less than 1 and updated and stored in the data storage means, An electronic sphygmomanometer comprising: a pulse wave amplitude value storage adjustment control unit that multiplies the pulse wave amplitude value and the pulse wave amplitude value extracted thereafter by the predetermined coefficient and stores the result in the data storage unit.