JPH01221139A - Electronic hemadynamometer - Google Patents

Abstract

PURPOSE:To make it possible to prevent errors in a maximum value of pulsating pressure waves by calculating a measured difference between a cuff pressure and a sampled cuff pressure so as to calculate a crawling reduced pressure value, by calculating an actual difference which is obtained by subtracting the crawling reduced pressure value from the measured difference, by positive actual adding value added with the actual difference during the actual value is maintained to be positive so as to detect the maximum value. CONSTITUTION:Among five cuff pressures stored in a pressure memory means 21, the oldest cuff pressure is subtracted from the newest cuff pressure by a measured difference calculating means 23 so as to calculate a variation in cuff pressure in an infinitesimal time as a measure difference. A crawling reduced pressure value calculating means 22 calculates a crawling reduced pressure value in an infinitesimal time. An actual difference calculating means 24 subtracts the crawling reduce pressure value from the measured difference so as to calculate an actual difference. A positive actual difference adding means 25 adds all successive positive actual differences to each other if an actual difference for every sampling is positive, and thus added value of the positive actual differences is stored and transmitted to a maximum value detecting means 26. If the content of the maximum value detecting means 26 is greater than 1 while the positive actual difference adding means 25 delivers zero, a value held by the maximum value detecting means 26 is determined to be a maximum value so as to be delivered to a blood pressure determining means 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic blood pressure monitor that determines blood pressure using an oscillometric method (vibration method).

[Prior Art] A conventional electronic blood pressure monitor using an oscillometric method involves wrapping a cuff around the upper arm of a subject, pressurizing the cuff to the pressure required for blood pressure measurement, and then gradually evacuating the cuff. During this evacuation process, the pulse pressure changes the cuff pressure, and a pulse pressure wave is superimposed on the cuff pressure. Extract the pulse pressure wave component from this cuff pressure,
Blood pressure is determined based on this pulse pressure wave component and cuff pressure.

A pulse pressure wave is extracted based on the difference in cuff pressure (time differential value) over a minute period of time. That is, only when the extracted differences are positive and continuous, the differences are added up and the maximum value of this added value is determined, thereby detecting the maximum value of the pulse pressure wave component of one cycle.

Furthermore, conventionally, the systolic blood pressure and the like are determined according to an envelope connecting the maximum value (increase pressure) of one pulse pressure wave component obtained by the above method or other methods.

For example, the cuff pressure corresponding to the maximum point on the envelope line is set as the average blood pressure, and the highest cuff pressure among the cuff pressures at which a pulse pressure wave component of 30% of the pulse pressure wave component corresponding to the maximum point of the envelope line occurs is set as the average blood pressure. High blood pressure is defined as high blood pressure, and the lowest cuff pressure among the cuff pressures at which 50% of the pulse pressure wave component corresponding to the maximum point of the envelope occurs is defined as the diastolic blood pressure.

By the way, when measuring blood pressure, the slow evacuation rate of the cuff is detected, and it is determined whether the amount of decompression per second (hereinafter referred to as "evacuation rate") is below a predetermined value.
If it is below the predetermined value, extraction of the pulse pressure wave is started as described above and the blood pressure is determined.

This is done because as the exhaust rate increases, the error in the extracted pulse pressure wave increases and the reliability of the blood pressure determination result decreases.

[Problem to be solved by the invention] In the above-mentioned conventional electronic blood pressure monitor using the oscillometric method, the pulse pressure wave included in the cuff pressure is extracted as a minute time difference, and the extracted difference is added only when it is in the positive direction. However, when the maximum value of the pulse pressure wave during the cuff pressure is detected, the maximum value of the pulse pressure wave decreases depending on the evacuation rate, so there is a problem that an error occurs in the maximum value of the pulse pressure wave. If the value of the pulse pressure wave is small, the pulse pressure wave may not be extracted.

Furthermore, there is a problem in that the exhaust rate varies depending on the thickness of the upper arm of the person to be measured, and the above-mentioned error varies depending on the thickness of the upper arm.

An object of the present invention is to provide an electronic blood pressure monitor in which an error is less likely to occur in the maximum value of the extracted pulse pressure wave even when the exhaust rate differs due to the difference in the thickness of the upper arm of the person being measured for each blood pressure measurement. purpose.

[Means for Solving the Problems] The present invention calculates the measured difference between one cuff pressure and a cuff pressure sampled a predetermined number of times before from this cuff pressure, and calculates the difference between the cuff pressures sampled a predetermined number of times before, and Calculate the amount of slow decompression generated by slow exhaust, calculate the actual difference by subtracting the amount of slow decompression from the actual measured difference, and add the real difference while the real difference is positive for M consecutive times. is calculated, and the maximum value among the above-mentioned positive real difference added values is detected.

[Operation] The present invention calculates the measured difference between one cuff pressure and the cuff pressure sampled a predetermined number of times before from this cuff pressure, and calculates the difference generated by the slow evacuation during the same period as the predetermined number of sampling periods. Calculate the slow decompression amount to Since the maximum value of the added real difference values is detected, there is no error in the maximum value of the extracted pulse pressure wave even if the exhaust rate differs due to the difference in the thickness of the upper arm of the subject for each blood pressure measurement. Hard to occur.

[Example 1 FIG. 1 is a block diagram showing one embodiment of the present invention.

This embodiment includes a cuff 11 that is wrapped around the arm of a subject, a pressurizing means 12 that pressurizes the cuff pressure 1 to a predetermined pressure necessary for blood pressure measurement, and an inside of the cuff 11 that is pressurized by the pressurizing means 12. the cuff 11;
a pressure detection means 14 that includes a pressure quadrature transducer that detects the pressure of , converts the pressure into an electric signal (pulse) and outputs it, and an electric signal (pulse) from the pressure detection means 14;
and a sampling means 15 for counting within a certain period of time and periodically repeating the counting according to a sampling signal.

Further, a pressure storage means 21, a slow pressure reduction amount calculation means 22, an actual difference calculation means 23, an actual difference calculation means 24,
A positive real difference adding means 25, a maximum value detecting means 26, a one hour limit means 27, and a blood pressure determining means 30 are provided. Note that the means 21 to 30 may be replaced with a CPU (microcomputer).

The pressure storage means 21 chronologically stores a predetermined number of discrete cuff pressures output by the sampling means 15 at predetermined time intervals, stores a new cuff pressure for each sampling, erases the oldest cuff pressure, and It constantly stores multiple cuff pressures while moving on the axis.

The actual measurement difference calculation means 23 is a means for calculating the difference (actual measurement difference) between one cuff pressure and a turnip pressure sampled a predetermined number of times before from this cuff pressure, and specifically, it is stored in the pressure storage means 21. This method subtracts the oldest cuff pressure from the newest cuff pressure, and calculates the difference in cuff pressure change over a minute period.

The slow decompression amount calculating means 22 is a means for calculating the slow decompression amount by which the cuff pressure gradually decreases due to the slow evacuation during the same period as the predetermined number of sampling periods (for example, 200 ms). Specifically, based on the cuff positive output by the sampling means 15, the cuff pressure decrease amount (evacuation rate) every second is detected, and the actual difference calculation means 23 calculates a coefficient according to the time to calculate the actual difference. , the amount of slow decompression is calculated by multiplying the amount of cuff pressure decrease. Note that the slow pressure reduction amount is a negative value.

The actual difference calculating means 24 is means for calculating an actual difference obtained by subtracting the slow pressure reduction amount from the actual measured difference.

The positive real difference addition means 25 is a means for calculating a positive real addition value by adding the above real differences while the real difference is positive and continuous, and stores the positive real difference adding value.

The maximum value detection means 26 is a means for detecting the maximum value from among the above-mentioned positive real difference added values, and detects the maximum value of the pulse pressure wave generated for each pulse. Furthermore, when the detected maximum value exceeds a predetermined value, the maximum value detection means 26 instructs the slow decompression amount calculation means 22 to stop calculating the slow decompression amount from now on. .

The time limiter 27 detects slow decompression when the time from when the maximum value detecting means 26 outputs the maximum value of a certain pulse pressure wave to when the maximum value of the next pulse pressure wave is output exceeds a predetermined time limit. A command is issued via the maximum value detection means 26 to the amount calculation means 22 to output the slow depressurization amount again.

The blood pressure determination means 30 uses the envelope of the maximum value of the pulse pressure wave for each pulse outputted by the maximum value detection means 25 and the sampling means 15
Systolic blood pressure, mean blood pressure, and diastolic blood pressure are determined based on the cuff pressure output by the system.

Next, the operation of the above embodiment will be explained.

First, when the cuff pressure 1 is wrapped around the arm of the subject and a measurement start switch (not shown) is turned on, the pressurizing means 12 pressurizes the cuff 1 until the pressure required for blood pressure measurement is reached, and after this pressurization stops, The air within the cuff 11 is gradually exhausted by the slow exhaust means 13, and along with this, the pressure displacement due to the pulse pressure wave begins to be transmitted to the cuff.

The pressure detection means 14 converts the cuff pressure into an electrical signal as a change in frequency, and the sampling means 15 converts the cuff pressure into an electrical signal at regular intervals (
For example, every 50 m5), a pulse is output in accordance with the sampled cuff pressure. FIG. 2 is a graph showing cuff pressure sampled as described above.

FIG. 6 is a flowchart showing the operation of the above embodiment.

First, the pressure storage means 21 stores the new cuff pressure output by the sampling means 15, and erases the five previously stored cuff pressures! (S l), that is, the pressure storage means 21
are registers RG5, RG4 . that store five cuff pressures. R
G3. RG2 and RGI, and the cuff pressures stored in the above registers are RG2→RGI%RG3→RG2,
It moves in the order of RG4 → RG3, RG5 → RG4, stores the cuff pressure output by the sampling means 15 in the register RG5, and selects the oldest stored cuff pressure among the five (the cuff pressure stored in the register RGI). to erase. Therefore, the pressure storage means 21 always stores the current cuff pressure and the cuff pressure that occurred four times earlier while moving on the time axis.

Then, among the five cuff pressures stored in the pressure storage means 21, the actual measurement difference calculation means 23 subtracts the oldest cuff pressure from the newest cuff pressure. The change in cuff pressure in 5×5×4=200 layers S) is calculated as a difference (measured difference ΔP) (S2). FIG. 3 is a graph showing an example of the measured difference obtained as described above.

On the other hand, the slow decompression amount calculating means 22 detects the amount of cuff pressure decompression every second (this is referred to as the "evacuation rate") (53
), and the influence of changes in turnip pressure due to noise and pulse pressure waves on the detected exhaust rate value.

In other words, in order to reduce the error, the exhaust rate is detected every 1 second, but if the time is sufficiently longer than the sampling period of the sampling means 15, the exhaust rate may be detected at intervals other than 1 second. You can do it like this.

Further, the slow decompression amount calculation means 22 calculates the minute time (20
0s+s) (this is referred to as the "slow decompression amount") (34). In the case of the above example, since the micro time is 200 m5, the slow decompression amount Pg is calculated as follows: Pg= (exhaust L/ -g) X (200as710
00m100O exhaust rate) X (115).

The actual difference calculation means 24 subtracts the slow pressure reduction amount Pg from the actual measurement difference ΔP output by the actual measurement calculation means 23 to obtain an actual difference Pd.
If i is calculated (35), this can be expressed as the following equation, and the actual difference Pdi is shown graphically in FIG.

Pd1=ΔP−Pg The actual difference Pdi is the slow pressure reduction amount Pg than the actual difference ΔP
The reason for the small number is as follows. In other words, the difference value is extracted while the cuff pressure is gradually decreasing due to slow evacuation. is included, it is necessary to compensate for the decrease in cuff pressure due to slow evacuation from the difference value. When the pulse pressure wave is calculated based on the difference value that compensates for the decrease in cuff pressure in this way, the calculated pulse pressure wave (
The actual difference (shown in FIG. 4) does not include an error due to a decrease in cuff pressure due to slow evacuation.

The positive real difference adding means 25 has an internal storage area, and each time the real difference Pdi is input.

The actual difference Pdi is stored in the storage area.

Moreover, if the real difference Pdi for each sampling is positive,
Then, add all consecutive positive real differences Pdi,
The positive real difference added value Ps that is the result of this addition is stored in the storage area (SS), and the positive real difference added value Ps
is sent to the maximum value detection means 26. Note that when the real difference Pdi becomes negative, the storage area in the positive real difference adding means 25 is cleared.

By the way, when the content of the maximum value detection means 26 is 1 or more and the positive real difference addition means 25 outputs O,
It is determined that the value held by the maximum value detection means 26 is the maximum value, and the maximum value is output to the blood pressure determination means 30. The blood pressure determination means 30 is.

storing each maximum value input from the maximum value detection means 26 and the value of the cuff pressure when the maximum value was input (37);
Thereafter, the contents of the maximum value detection means 26 are cleared.

FIG. 5 is a graph showing the increased pressure (positive real difference added value Ps).

The above increased pressure is calculated as the difference between multiple samplings, and the amount of slow decompression due to the evacuation rate is removed and added for each sampling, so it is averaged, thereby reducing noise components included in the cuff pressure. can do.

In addition, in the slow decompression amount calculation means 22, when the exhaust rate is positive, the measured exhaust rate is incorrect because the pulse pressure wave becomes large to some extent, or
It should be considered that unnecessary pressure other than the pulse pressure wave is applied, and in this case, the slow decompression amount is not calculated and the previously calculated and stored slow decompression amount is used continuously.

Furthermore, when the increased pressure output by the maximum value detection means 26 (the maximum positive value of the pulse pressure wave in one cycle) is larger than a predetermined value, the measurement error of the exhaust rate often becomes large, and in this case, An error occurs in the slow decompression amount. Therefore, when the maximum value of the detected positive real difference addition value exceeds a predetermined value, the slow decompression amount calculating means 22 is commanded to stop calculating the new slow decompression amount, The slow depressurization amount calculation means 22 holds the slow depressurization amount stored at that time.

Then, the one-hour limiter 27 operates from the time when the maximum value of the positive real difference added value outputted by the maximum value detector 26 occurs.
The time until the next maximum value occurs is measured, and if the next maximum value does not occur within a predetermined time, it is determined that the maximum value of the positive real difference added value detected before that is not a pulse pressure wave component. , via the maximum value detection means 26, the suspension of calculation of the slow pressure reduction amount is canceled. Therefore, in this case, the slow pressure reduction amount calculation means 22 calculates the slow pressure reduction amount again.

The positive real difference addition means 25 calculates the positive real difference addition value PI(i).
(S7), the positive real difference added value PI(i) is compared with the maximum value P1max up to that point (S8), and the positive real difference added value PI(i) becomes the maximum value PI■a! If it is larger than (S9), the positive real difference added value PI(i) is stored as the maximum value PImax, and the cuff pressure when the maximum value PI*aX occurs is determined as the average blood pressure S l 1).

The cuff pressure at which the positive real difference addition value P(i) corresponding to the first predetermined % of the maximum value PImax occurs is determined as the systolic blood pressure (S12), and then the process returns to Sl.

Then, if the next positive real difference added value PI(i) is larger than the maximum value PImax (59), the mean blood pressure value and the systolic blood pressure value are changed as needed, and the mean blood pressure and systolic blood pressure are finally determined. Ru.

On the other hand, when the envelope of increased pressure shown in FIG.
i) is the maximum value PI layer a! becomes smaller than
If the positive real difference addition value PI(i) is less than α (α = second predetermined % of maximum value p) wax) (S21)
, determine the cuff pressure at that time as the diastolic blood pressure value (32
2).

Then, the above average blood pressure value, systolic blood pressure value, and diastolic blood pressure value are
It is displayed on a display means (not shown) (323).

In the above embodiment, if the maximum value detected by the maximum value detection means 26 is abnormally larger or smaller than the normally considered value, it is invalidated as a pulse pressure wave component and the detected maximum value is The blood pressure may not be sent to the blood pressure determining means 30.

Further, the pressure storage means 21 may store cuff pressures other than five.

[Effects of the Invention] According to the present invention, even if the exhaust rate differs due to differences in the thickness of the upper arm of the person being measured for each blood pressure measurement, errors are unlikely to occur in the maximum value of the extracted pulse pressure wave. have an effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing changes in cuff pressure in the above example. FIG. 3 is a diagram showing changes in actually measured differences in the above example. FIG. 4 is a diagram showing changes in the actual difference in the above embodiment. FIG. 5 is a diagram showing changes in increased pressure in the above embodiment. FIG. 6 is a flowchart showing the operation of the above embodiment. 21... Pressure storage means, 22... Very slow pressure reduction amount calculation means, 23... Actual difference calculation means, 24... Actual difference calculation means. 25... Positive real difference addition means, 26... Maximum value detection means, 27... Time limiting means, 30... Blood pressure determination means. Patent Applicant Satoshi Yamaguchi Agent Arata Yokubo - Time Figure 5

Claims (6)

[Claims] (1) In an electronic sphygmomanometer that determines blood pressure according to a pulse pressure wave component included in a sampled cuff pressure value while slowly evacuating the cuff after pressurizing the cuff, one cuff pressure and this cuff Actual difference calculating means for calculating an actual difference between the pressure and the cuff pressure sampled a predetermined number of times before; A slow decompression amount for calculating a slow decompression amount generated by the slow evacuation during the same period as the sampling period of the predetermined number of cuffs; Calculating means; Actual difference calculating means for calculating an actual difference obtained by subtracting the slow speed decompression amount from the actual measured difference; and Positive actual difference calculating means for calculating an actual additional value by adding the actual difference while the actual difference is positive and continuous; An electronic blood pressure monitor comprising: a difference adding means; and a maximum value detecting means for detecting the maximum value among the positive real difference added values. (2) In claim (1), when the maximum value detected by the maximum value detection means exceeds a predetermined threshold, the latest slow decompression amount obtained by the slow slow decompression amount calculation means is calculated as the subsequent slow slow decompression amount. An electronic blood pressure monitor characterized by being used as an electronic blood pressure monitor. (3) In claim (2), when the pulse pressure wave is not generated within a second predetermined time after the maximum value detected by the maximum value detection means exceeds a predetermined threshold value, the slow decompression amount calculation means An electronic blood pressure monitor characterized by obtaining a new slow decompression amount from. (4) In claim (1), when the maximum value output by the maximum value detection means is below a first predetermined level or above a second predetermined level, the maximum value is not used as a factor for determining blood pressure. An electronic blood pressure monitor featuring (5) The electronic blood pressure monitor according to claim (1), wherein a value obtained by subtracting a predetermined value from the slow pressure reduction amount in the slow pressure reduction amount calculating means is used as the new slow pressure reduction amount. (6) In claim (1), the period during which the slow decompression amount calculation means calculates the slow decompression amount is a period in which the level of the pulse pressure wave included in the cuff pressure is below a predetermined value. Sphygmomanometer.