JPH06108B2 - Electronic blood pressure monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention detects a pulse wave amplitude in the process of compressing an artery with a cuff and changing the cuff pressure, and determines the blood pressure using this pulse wave amplitude. About electronic blood pressure monitor.

(B) Conventional Technique Generally known electronic blood pressure monitors are of the so-called arm type in which an arm band is wrapped around the upper arm to compress an artery. However, the arm-type electronic blood pressure monitor is relatively large and inconvenient to carry,
In addition, the inventor of the present application has already filed a separate application for an electronic sphygmomanometer for fingers that is pressed by a cuff with a finger because it is troublesome to roll the arm when wearing the armband.

This finger electronic blood pressure monitor detects the amplitude of the pulse wave signal for blood pressure measurement, and determines the blood pressure from the change in the pulse wave amplitude and the cuff pressure. A photoelectric pulse wave sensor including a light emitting element and a light receiving element is used to detect the pulse wave.

(C) Problems to be Solved by the Invention In the above electronic blood pressure monitor for fingers, when the blood pressure is measured, when the finger is inserted into the cuff and pressurized at a high speed, the cuff pressure is as shown in FIG. The output (baseline) of the pulse wave sensor fluctuates greatly in the process of rising. This is when the cuff inflates
This is because the angle between the light emitting element and the light receiving element of the pulse wave sensor changes, and the amount of light input to the light receiving element changes. Therefore, ignoring this baseline fluctuation during pressurization, a simple program detects the pulse wave component to obtain the pulse wave amplitude, and when the blood pressure value is determined, the baseline fluctuation is detected as the pulse wave component. However, it may cause measurement failure or erroneous measurement.

In view of the above, it is an object of the present invention to provide an electronic sphygmomanometer that can perform accurate measurement without being affected by pulse wave baseline fluctuations.

(D) Means and Actions for Solving Problems As shown in FIG. 1, the electronic sphygmomanometer of the present invention has a cuff 1 for compressing an artery of a body to be measured, and pressurizing or depressurizing the inside of the cuff. A pulse wave amplitude detecting means 4 for detecting a pulse wave amplitude in the pressure change process of the cuff, which includes an air pressure system 2, a pulse wave sensor 3 provided between the inner surface of the cuff and the measured object, and after starting the operation,
Baseline stability determination means 5 for determining whether or not the output of the pulse wave sensor is stable, and blood pressure determination for determining blood pressure based on the cuff pressure and the pulse wave amplitude by starting the operation by the stability determination of the baseline stability determination means. And means 6.

With this electronic sphygmomanometer, when pressurizing, that is, when starting operation,
Since the baseline is not stable, the baseline stability determination means does not capture the pulse wave sensor output during this period as blood pressure determination data. When the baseline stability determination means outputs a stability determination output, the blood pressure determination means takes in the subsequent pulse group sensor output as data for blood pressure determination, and shifts to the determination operation.

(E) Examples Hereinafter, the present invention will be described in more detail with reference to Examples.

FIG. 2 is a schematic block diagram of an electronic blood pressure monitor for a finger in which the present invention is implemented.

In FIG. 2, the cuff 11 is formed of a rubber bag and has a cylindrical shape that allows insertion of fingers.
1 is provided with a pulse group sensor 12, and the pulse group signal detected by the pulse group sensor 12 is taken into an MPU (microprocessor unit) 15 via an amplifier 13 and an A / D converter 14. Has become. Although not shown, the pulse sensor 12 used here is made up of a light emitting element and a light receiving element, is provided on the inner wall of the cylinder of the cuff 11, and when a finger is inserted into the cuff 11, the pulse surface sensor 12 is It is located between the cuffs 11.

Further, the cuff 11 is connected to the pressure sensor 17 by the rubber tube 16, is also connected to the air buffer 18, and is further connected to the slow exhaust valve 19 and the quick exhaust valve 20. Also,
The air buffer 18 is connected to a pressurizing pump 21 via a check valve 22. The pressurizing pump 21 includes a motor.

The cuff pressure detected by the pressure sensor 17 is amplified by the amplifier 23, and is taken into the MPU 15 via the A / D converter 14.

The MPU 15 has a built-in memory for storing programs and calculated values, a function for taking in pulse wave data and cuff pressure data by switching from the A / D converter 14, a function for turning on / off the pressurizing pump 21, ON / OFF of quick exhaust valve 20
Function, a function of determining whether or not the output of the pulse wave sensor 12 is stable after the operation is started, a function of detecting the pulse wave amplitude from the output of the pulse wave sensor 12, and a systolic blood pressure (from the cuff pressure and the pulse wave data). It has a function of determining a blood pressure value such as systolic blood pressure (DIA).

Further, the determined blood pressure value, that is, the systolic blood pressure (SYS) and the like is output from the MPU 15 and displayed on the display 24,
In addition, the notification sound is output by the buzzer 2 according to a command from the MPU 15.
5 is output.

Next, the operation of the electronic blood pressure monitor of the above embodiment will be described with reference to the control flow chart shown in FIG.

Before starting the measurement, the measurer inserts the index finger into the cylindrical shape of the cuff 11 and turns on a power switch (not shown) attached to the MPU 15. This starts the operation. First, in step ST (hereinafter referred to as ST) 1, the display 2
All display segments of all digits of 4 are lit and displayed for 1.5 seconds (ST2), then the rapid exhaust valve 20 is opened (ST3) and the rapid exhaust mark on the display 24 is blinked (ST).
4). Then, it is determined whether or not the cuff pressure is 0, and if it is not 0, the process waits until it becomes 0 (ST). When the cuff pressure becomes 0, the exhaust mark is turned off (ST6) and the preparation completion mark is turned on (ST7). This allows the measurer to know that the preparation is complete. Here again, MPU15
When a start switch (not shown) attached to is turned on, the determination in ST8 becomes YES and the preparation completion mark disappears (ST8). Subsequently, an LED (not shown) indicating that the measurement is in progress is turned on (ST10), the rapid exhaust valve 20 is closed, and the cuff 11 is pressurized to the set value (ST1).
2). The set value here means the pressurization target value set to a value 20 to 30 mmHg higher than the systolic blood pressure value of the subject.
When the pressure is increased to the set value, the pressure pump 21 is turned off, and it is determined whether or not the current pressurization is repressurization (ST13). If the pressurization is the first pressurization, the process proceeds to ST15, and the slow exhaust valve 19 is used. Starts slow exhaust. However, since the baseline of the pulse wave is not stable immediately after the end of pressurization, it is determined whether the baseline is stable (ST16), and the process waits until the baseline is stable.
This baseline stability determination process is a feature of this electronic sphygmomanometer, and its details will be described later. If the base line is not stable and the cuff pressure falls below 40 mmHg below the set value (ST17), it is judged whether re-pressurization has already been performed (ST18), and the re-pressurization corresponds to the first time. , The set value +30 mmHg is set as a new set value (ST19), the re-pressurization mark blinks (ST20),
After returning to ST12, the pressure is repressurized to the set value, and when the pressure is repressurized to the re-set value, this time ST13 "Repressing process?"
The determination is YES, and the repressurization mark is turned off (ST14).

If it has already been repressurized once, and this time the repressurization is the second time, the determination in ST18 is NO, the LED is turned off (ST13), and then the quick exhaust valve 20 is opened to temporarily exhaust the gas. To do. If the baseline is stable before the cuff pressure falls to the set value of -40 mmHg, the determination in ST16 becomes YES, and the amplitude of each pulse wave is measured in the subsequent processing. That is, the pulse number j for obtaining the amplitude of the pulse wave is set to 0 (ST21), the sample counter i within one beat is set to 1, the pulse number is set to j = 1, and the maximum value xmax of the pulse wave level is set to 0, The minimum value xmin is set to xsup (ST22). Here, x _sup is an upper limit value that the pulse wave level x _i can take.

Then, in ST23, it is determined whether the cuff pressure is larger than 20 mmHg. If it is less than 20 mmHg, move to ST31, turn off the LED, return to ST3, open the quick exhaust valve 20, turn on the exhaust mark (ST4) and wait for exhaust, but in the normal case, the determination in ST23 is YES. Then, the pulse wave data x _i is read (ST24), the difference value between the previous pulse wave data x _i-1 and the current pulse wave data x _i is calculated, and whether the difference value is larger than the predetermined value x _t It is determined whether or not (ST25). This determination is made in order to divide the pulse wave into one beat at the point where the pulse wave level changes abruptly.

If the determination in ST25 is NO, move to the next ST32.
It is determined whether or not the pulse number j is not updated for 1.5 seconds, and if it is updated, then the magnitude relationship between the current pulse wave data x _i and the maximum pulse wave value x max is compared (ST33). If x _i > x max, the current pulse wave data x _i is updated and stored as a new pulse wave maximum value x max (ST3).
4). On the other hand, if x _i ≦ xmax, ST34 is skipped and the process proceeds to ST35. In ST35, the magnitude relationship between the current pulse wave data x _i and the pulse wave minimum value x min is compared. When x _i <xmin, the current pulse wave data x _i is updated and stored as a new pulse wave minimum value Xmin (ST3).
6). Conversely, if x _i ≧, ST36 is skipped and S
Move to T37.

When the updating of the maximum value xmax and the minimum value xmin of the pulse wave data is completed in ST33 to ST36, the counter i is updated in ST37.
+1 processing is performed, and the process returns to ST23. Thereafter, x
ST32 to ST until _i-1− x _i > x _i > x _t
37, the processing of ST23 to ST25 is repeated to continue the processing of updating the pulse wave maximum value xmax and minimum value xmin.

When it is determined in ST25 that x _i-1 −x _i is equal to or greater than the predetermined value x _t , the buzzer 25 is sounded in ST26 to notify the pulse wave extraction. Then, the difference value Aj between the pulse wave maximum value xmax and the pulse wave minimum value amin, that is, the pulse wave amplitude Aj is obtained (ST2
7). If the pulse number j is not updated for 1.5 seconds in ST32, it is equivalently treated as one night has elapsed and the buzzer 25 does not sound, but the pulse wave amplitude Aj is obtained (ST27). The obtained pulse wave amplitude Aj is stored in the memory in the MPU 15. Then, the blood pressure determination process is performed using this pulse wave amplitude Aj as a parameter (ST28). Here, there are various blood pressure determination algorithms. For example, the cuff pressure at the time when the pulse wave starts to appear is the systolic blood pressure P _SYS, and the cuff pressure at the time when the pulse wave has the maximum amplitude (difference value) is the average blood pressure. P _MEAN ,
In addition, the minimum blood pressure P _DIA is P _MEAN = P _DIA + (P _SYS −
It is calculated from the formula of P _DIA ) / 3. Then, the process returns to ST22 until the minimum blood pressure P _DIA is determined, the pulse number j + 1 is incremented in ST22, and then the above process is repeated, and the pulse wave amplitude Aj (the difference value between the maximum value xmax and the minimum value xmin) for each pulse wave. Is calculated and the blood pressure determination process is continued.

When the process of determining the maximum blood pressure and the minimum blood pressure is completed (ST2
9), these blood pressure values are displayed on the display 24 (ST3
0) After that, the LED is turned off (ST31), the process returns to ST3, the quick exhaust valve 20 is operated, and the measurement operation is ended.

Next, the details of the baseline stability determination processing operation will be described with the flow chart of FIG. 4 as a minimum.

When the operation shifts to the slow speed exhaust of ST15 in Fig. 3, 1.
The 5-second timer is started (ST41), and the maximum pulse wave level value xmax is set to 0 and the minimum value xmin is set to xsup (ST42).
Then, the output from the pulse wave sensor 12, that is, the pulse wave data x is obtained (ST43). The magnitude relationship between the detected pulse wave level x and the maximum value xmax is compared (ST44). If x> xmax, the x is updated as a new pulse wave level maximum value xmax (ST45), and conversely x> xmax. If not ST
45 is skipped, and the magnitude relationship between the detected pulse wave level x and the pulse wave minimum value xmin is compared (ST46). If x <xmin, the x is updated as a new pulse wave level minimum value xmin. (ST47), on the contrary, if x <xmin, then S
Skip T47. Then, it is determined whether or not the 1.5-second timer has timed up (ST48). If the time has not expired, the process returns to ST43, and the processes of ST43 to ST48 are repeated until the 1.5-second timer times out.
Then, the maximum value xmax and the minimum value xmin of the pulse wave level in 1.5 seconds are obtained. When the 1.5 second timer expires,
Then, the difference value a between the maximum value xmax and the minimum value xmin of the pulse wave level
Is calculated (ST49), and it is determined whether this difference value a is smaller than a predetermined pulse wave minimum value amin (ST50). Fifth
If the baseline of the pulse wave is still not stable, such as between points A and B in the figure, the determination is NO, the process returns to ST41 through ST17, and the processes of ST41 to ST50 are repeated, and the maximum value every 1.5 seconds. The difference value a between xmax and the minimum value xmin is calculated, and the baseline stability determination is continued depending on whether or not this value becomes equal to or less than the predetermined value amin. When a <amin, the baseline is stable (5th
After the point C in the figure), the process moves to the next measurement process after ST21.

If the cuff is not pressurized enough, as shown in FIG.
Since the original pulse wave fluctuation appears before the baseline stabilizes when entering the slow-speed exhaust, the determination in ST50 of FIG. 4 does not become YES even after a lapse of time. Therefore, it is possible to detect insufficient pressurization by executing the baseline stability determination process and determining whether or not the unstable state continues for a certain time or longer.

(E) Effect of the Invention According to the present invention, measurement (pulse wave new width detection and blood pressure determination) is not started until the baseline of the pulse wave level is stabilized, and the baseline changes due to high-speed pressurization of the cuff. Even if the baseline is stabilized, the blood pressure determination process is started after the baseline is stabilized. Therefore, accurate blood pressure measurement can be performed without being affected by the baseline fluctuation.

Further, it is possible to detect the presence or absence of insufficient pressurization by using the baseline stability determination output.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of the present invention, FIG. 2 is a block diagram of an electronic blood pressure monitor for a finger in which the present invention is implemented, and FIG.
FIG. 4 is a main flow chart for explaining the operation of the electronic blood pressure monitor for the same finger, FIG. 4 is a flow chart showing in detail the routine for determining the baseline stability of the main flow chart, and FIG. FIG. 6 is a time chart of cuff pressure and pulse wave level for explaining the baseline stability determination process of the electronic sphygmomanometer, and FIG. 6 is a cuff pressure and a cuff pressure for explaining the case of using the baseline stability determination process for the underpressure process. It is a time chart of a pulse wave level. 1: Cuff, 2: Air pressure gauge, 3. : Cuff pressure sensor, 4: Pulse wave sensor, 5: Pulse wave amplitude detection means, 6: Baseline stability determination means, 7: Blood pressure determination means.

Claims (2)

[Claims] 1. A cuff for compressing an artery of a body to be measured,
An air pressure system that pressurizes or depressurizes the inside of the cuff, a cuff pressure sensor that detects the pressure of the cuff, and a pulse wave sensor that is provided between the inner surface of the cuff and the object to be measured. Pulse wave amplitude detection means for detecting the pulse wave amplitude,
After the operation is started, a baseline stability determining means for determining whether or not the output of the pulse wave sensor is stable, and an operation is started by the stability determination of the baseline stability determining means, and the blood pressure is determined from the cuff pressure and the pulse wave amplitude. An electronic sphygmomanometer including a blood pressure determining means for determining. 2. The electronic sphygmomanometer according to claim 1, wherein the baseline stability determining means determines whether or not the change in the output of the pulse wave sensor is below a predetermined value at predetermined time intervals. .