KR890002765B1 - Electronic blood pressure meter - Google Patents

Abstract

The blood pressure meter has a cuff (2) adapted to be fitted around the arm of a patient whose pressure is to be measured, and is formed with a cavity. The cavity can be pressurised and depressurised by a pump (9). The pressure is sensed in the cavity and representative output signals are produced. A pulse wave component in the output signal of the sensor (11) is then detected. The amplitude of the detected pulse wave is then determined. The systolic blood pressur, and the distolic blood pressure are then determine according to the determined amplitude and the output signal produced by the pressure sensor.

Description

Electronic sphygmomanometer

1 is a flowchart illustrating the operation of an electronic blood pressure monitor according to an embodiment of the present invention.

2 is an external perspective view of the electronic blood pressure monitor.

3 is a circuit block diagram of the electronic blood pressure monitor.

4 (a) and 4 (b) show the relationship between the blood pressure value measured by the electronic blood pressure monitor and the blood pressure value measured by the stethoscope method.

5 (a), 5 (b) and 5 (c) are diagrams showing the principle of blood pressure determination by the vibration method.

6 (a) and 6 (b) show the relationship between the blood pressure value measured by a conventional electronic blood pressure monitor employing a vibration method and the blood pressure value measured by a stethoscope method.

* Explanation of symbols for main parts of the drawings

2: cuff 9: pressurized pump

10 exhaust valve 11 pressure sensor

14: microcomputer (MPU)

The present invention relates to an improvement of an electronic blood pressure monitor.

Conventionally, an electronic sphygmomanometer employing a so-called vibration method includes a cuff, a pressure pump for pressurizing air in the cuff (hereinafter referred to as a cuff), an exhaust valve for depressurizing air in the cuff, and an air pressure in the cuff ( It is known that a pressure sensor and a microcomputer (MPU) for detecting cuff) are provided. The MPU detects the pulse wave component from the output signal of the pressure sensor, calculates the pulse amplitude from the pulse wave component, and determines the maximum blood pressure value (SYS) and the minimum blood pressure value (DIA) from the cuff pressure and the pulse amplitude. .

In the conventional electronic sphygmomanometer, it is typical to use the threshold described below as a procedure for determining the highest blood pressure value and the lowest blood pressure value based on the pulse amplitude and the cuff pressure.

The pulse wave is observed when the cuff pressure is transmitted to the cuff when blood flows when the cuff pressure is decompressed at a constant micro velocity in the artery that exhibits arterial blood flow. As shown in Figs. 5 (b) and 5 (c), the pulse amplitude amplitude Ap increases with the decrease in the cuff pressure Pc and gradually decreases after taking the maximum value Apmax.

In the process of increasing the pulse amplitude, the cuff pressure at the time when the pulse amplitude closest to the threshold, which is a predetermined ratio of the maximum pulse amplitude Apmax, is observed, is determined as the maximum blood pressure value. In the pulse amplitude reduction process, the cuff pressure at the time when the pulse amplitude is closest to another threshold value, which is a predetermined ratio of the maximum pulse amplitude, is determined as the minimum blood pressure value (FIGS. 5 (a) and 5 (b)). Also, in FIG. 5 (c), 60% of the maximum pulse amplitude Apmax as a threshold for determining the maximum blood pressure value and 70% of the maximum pulse amplitude Apmax as the threshold for determining the lowest blood pressure value are shown.)

The conventional electronic sphygmomanometer has a drawback in that a systematic error occurs with respect to an accurate blood pressure value measured by a stethoscope. This is demonstrated below based on FIG. 6 (a) and FIG. 6 (b).

FIG. 6 (a) shows a correlation between the highest blood pressure value S _AUS (mmHg) by the stethoscope method and the highest blood pressure value Sosc (mmHg) by the vibration method simultaneously measured for the same subject. The threshold for determining the maximum blood pressure Sosc by the vibration method is set at 60% of the maximum pulse wave amplitude Apmax.

In this case, the highest blood pressure Socc is slightly lower in hypertensive patients and the highest blood pressure Sosc is slightly higher in hypotensive patients. The straight line L's in FIG. 6 (a) is a straight line approximation of the relationship between the highest blood pressure values Sosc and S _AUS . This straight line L's is represented by the following first equation.

Sosc = a _s S _AUS + b _s ... … … … … … … … … … … … … … … … … … … (One)

Specific values of a _s and b _s are 0.91 (dimensionless) and 11.2 (mmHg), respectively.

FIG. 6 (b) shows the relationship between the minimum blood pressure value D _AUS (mmHg) by the stethoscope method and the minimum blood pressure value Dosc (mmHg) by the vibration method simultaneously measured for the same subject. It is a figure which shows the relationship of the minimum blood pressure value Dosc (mmHg) by the vibration method. The threshold for determining the minimum blood pressure Dosc by the vibration method is set to 70% of the maximum pulse amplitude Apmax.

Even in this case, the lowest blood pressure value Dosc is slightly lower in hypertensive patients, and the lowest blood pressure value Dosc is slightly higher in hypotensive patients. The straight line L ' _D in FIG. 6 (b) approximates the relationship between the minimum blood pressure values Dosc and D _{AUS in} a straight line. This straight line L ' _D is represented by the following second equation.

Dosc = a _d D _AUS + b _d . … … … … … … … … … … … … … … … … … … (2)

Specific values of a _d and b _s are 0.91 (dimensionless) and 7.5 (mmHg), respectively. In the above description, the relationship between the highest blood pressure Sosc and S _{AUS and the} lowest blood pressure Dosc and D _AUS is represented by a first-order formula, respectively. Each is represented by.

Sosc = f _s (S _AUS ). … … … … … … … … … … … … … … … … … … … … … … (3)

Dosc = f _d (D _AUS ). … … … … … … … … … … … … … … … … … … … … … … (4)

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described drawbacks, and an object of the present invention is to provide an electronic blood pressure monitor that can accurately measure blood pressure values even for hypertensive patients and hypotensive patients, except for errors caused when determining blood pressure values by a vibration method.

The electronic blood pressure monitor of the present invention as a means for solving the above-mentioned shortcomings includes: a pressurizing means for pressurizing a cuff and a fluid in the cuff; Pulse wave component detecting means for detecting pulse wave components contained in the output signal of the pressure detecting means, pulse amplitude calculating means for calculating pulse wave amplitude values from pulse wave components detected by the pulse wave component detecting means, and pulse amplitude calculating value And a blood pressure value determining means for determining the highest blood pressure value and the lowest blood pressure value based on the output signal of the means and the output signal of the pressure detecting means. The predetermined blood pressure value determined by at least one of the highest blood pressure value and the lowest blood pressure value determined by the blood pressure value determining means. Characterized by the blood pressure value correction means for performing the correction operation of the configuration.

The electronic sphygmomanometer according to the present invention is a formula in which the above equation (3) is described in relation to the highest blood pressure value S _AUS measured by the stethoscope method when performing a correction operation on the maximum blood pressure value determined by the blood pressure value determining means.

S _AUS = g _s (Sosc)... … … … … … … … … … … … … … … … … … … … … … … (5)

Corrected in accordance with the above, and excluding the systematic error from the highest blood pressure Sosc measured by the vibration method.

In the case of performing a correction operation on the minimum blood pressure value determined by the blood pressure value determining means, the above equation (4) is described in the form of a description of the exact minimum blood pressure value D _AUS measured by the stethoscope method.

D _AUS = g _d (Dosc). … … … … … … … … … … … … … … … … … … … … … … (6)

The system error is corrected and the system error is excluded from the blood pressure Dosc measured by the vibration method.

EXAMPLE

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3, 4 (a) and 4 (b).

Explain.

First, the threshold for determining the blood pressure value of the electronic sphygmomanometer and the correction equation for the correction operation will be described.

In the electronic blood pressure monitor of this embodiment, the threshold value for determining the maximum blood pressure value is set at 60% of the maximum pulse amplitude Apmax, and the threshold for determining the minimum blood pressure value is set at 70% of the maximum pulse wave amplitude Apmax. .

As the correction equation for the correction operation, the following equation (5) is used for the highest blood pressure value.

SYS = (Sb _s ) / a _s ... … … … … … … … … … … … … … … … … … … … … … (5)

a _s = 0.91... … … … … … … … … … … … … … … … … … … … … … … … … (6)

b _s = 11.2 (mmHg)... … … … … … … … … … … … … … … … … … … … … … (7)

Here, SYS is the highest blood pressure value finally determined, and S is the highest blood pressure value (hereinafter referred to as the maximum blood pressure back value) before performing the correction operation determined by the blood pressure value determining means. Equation (5) is a form in which electric formula (1) is described with respect to the maximum blood pressure value S _AUS .

On the other hand, the following first equation (8) is employed as the correction equation for the minimum blood pressure value.

/ DIA = (Db _d ) / a _d ... … … … … … … … … … … … … … … … … … … … … … … (8)

a _d = 0.91... … … … … … … … … … … … … … … … … … … … … … … … … … (9)

b _d = 7.5 (mmHg)... … … … … … … … … … … … … … … … … … … … … … … … 10

Here, DIA is a final minimum blood pressure value, and D is a minimum blood pressure value (hereinafter referred to as a minimum blood pressure candidate value) before performing a correction operation determined by the blood pressure value determination means. This formula (6) also has the form which described said formula (2) with respect to minimum blood pressure value DAUS.

Next, the specific structure of the electronic blood pressure monitor 1 of this embodiment is demonstrated below, referring FIG. 2 and FIG.

2 is an external perspective view of the electronic blood pressure monitor 1 according to this embodiment. (2) is a cuff composed of a belt-shaped air bag. The cuff 2 is connected to the electronic blood pressure monitor body 4 via a soluble tube 3.

On the upper surface of the electronic blood pressure monitor main body 4, an indicator 5, a power switch 6, and a measurement switch 7 made of a liquid crystal display element or the like are provided.

3 shows a block diagram of the air gauge of the electronic blood pressure monitor 1 and the measurement circuit. The cuff 2 is provided with a pressure pump (pressurizing means) 9, an exhaust valve (reducing pressure means) 10 and a pressure sensor (pressure detecting means) via a tube 3 and pipes 8a, 8b and 8c. (11) is connected. The exhaust valve 10 is comprised of two valves, a rapid exhaust valve and a slow speed exhaust valve. The pressure sensor 11 uses a diaphragm pressure transducer or a semiconductor pressure transducer using a strain gauge. The pressure pump 9 and the exhaust valve 10 are controlled by a microcomputer (NPU) 14 to be described later.

The output signal of the pressure sensor 11 is amplified by the amplifier 12 and converted into a digital signal by the analog / digital (A / D) converter 13.

The MPU 14 takes in the output signal of the pressure sensor 11 digitally converted by the A / D converter 13 at regular intervals. The MPU 14 has a function of detecting a pulse wave component from an output signal of the pressure sensor 11, a function of calculating a pulse amplitude, a maximum blood pressure candidate value and a minimum blood pressure candidate value, and the highest blood pressure candidate value and the lowest blood pressure candidate. And a function of performing correction operation on the teeth, controlling the pressure pump 9 and the exhaust valve 10, and the like.

The MPU 14 is also connected with the indicator 5, the power switch 6, and the measurement switch 7 for displaying the highest blood pressure value and the lowest blood pressure value.

Next, the operation of the electronic blood pressure monitor 1 according to this embodiment will be described below with reference to FIG. 1 mainly.

Initially, the cuff 2 is wound on the upper part of the arm of the subject, and the power switch 6 is turned on. When the power switch 6 is turned on, the MPU 14 determines whether the measurement switch 7 is turned on and if it is not turned on, repeats this determination process and waits here (step ST1 (hereinafter referred to as ST)). Refer to FIG. 1).

When the measurement switch 7 is turned on in ST1, the MPU 14 operates the pressure pump 9 to operate ST2 to pressurize the cuff 2 of ST2. The MPU 14 receives the cuff pressure Pc therebetween from the A / D converter 13 and determines whether the cuff pressure Pc has reached a predetermined cuff pressure (ST3).

In ST3, when it is determined that the cuff pressure Pc has reached the predetermined value, it advances to ST4, the MPU 14 stops the pressure pump 9, and opens the slow-speed exhaust valve of the exhaust valve 10, and the cuff 2 Slow-speed exhaust gas is started (ST5).

Next, in ST6, the count of the timer T1 is started _first . The timer T ₁ is used to determine the period for calculating the pulse amplitude Ap (n) from the pulse wave component and is set to 1 second to 2 seconds. In ST7, the count of the timer T ₂ is started. This timer T ₂ is for determining the sampling period at which the MPU 14 receives the cuff pressure Pc (i) at the A / D converter 13. This period is set between 10 and 50 ms.

To wait for the in ST8, the timer T ₂ has taimeop, when the timer T ₂ is determined to be taimeop, advances to ST9. In ST9, the MPU 14 receives the cuff pressure data Pc (i) from the A / D converter 13. In ST10, the pulse wave component value Pu (i) is detected from these cuff pressure data Pc (i).

As a means for detecting the pulse wave component, analog means using a band pass filter is also widely used. In this embodiment, however, a digital filter is employed for the calculation processing of the MPU 14. In the twisted pair processing of this digital filter, first, Pc (i) taken in by sampling at this time is determined as the variable X (i).

x (i) = Pc (i)... … … … … … … … … … … … … … … … … … … … … … … … (11)

Next, the value of the variable y (i) is calculated by the following expression (12) from the variable x (i-1) obtained by the previous sampling and the variable y (i-1) different from each other.

alpha y (i)-beta y (i-1) = x (i) -x (i-1)... … … … … … … … … … … … … … … (12)

Again, according to another variable z (i-1) obtained by the previous sampling and the variables y (i) and y (i-1), the variable z (i) in this sampling is expressed according to the following expression (13). Calculate.

αz (i) -βz (i-1) = y (i) -y (i-1)... … … … … … … … … … … … … … … … (13)

Z (i) obtained in the above formula is the pulse wave component value Pu (i) in this sampling.

Pu (i) = Z (i)... … … … … … … … … … … … … … … … … … … … … … … … (14)

In addition, said (alpha) and (beta) are normally set as follows, respectively.

α = 0.98 … … … … … … … … … … … … … … … … … … … … … … … (15)

β = 0.95... … … … … … … … … … … … … … … … … … … … … … … … (16)

In addition, when i = 1, that is, when the first digital filter operation is performed, the variables x (0), y (0) and x (0) do not exist. Set it.

Again, since only one value is used in the actual operation for the variable strings x (i), y (i), and z (i), only one value in the actual operation is stored in the memory. It can save memory capacity.

When component maekpayi value Pu (i) is detected in ST10 and ST11 in advance to determine whether or not the timer T ₁ is taimeop. If the timer T ₁ has not timed up, the process returns to ST7 and the detection of the pulse wave component value Pu (i) is continued.

When the timer T ₁ times up, it advances to ST12 and the pulse amplitude amplitude Ap (n) is calculated from the data sequence of the pulse wave component value Pu (i) detected during this timer T ₁ count. This Ap (n) calculation is performed by extracting the maximum value Pumax and the minimum value Pumax from the data sequence of the pulse wave component value Pu (i) in this timer T ₁ counter and taking these differences.

Ap (i) = Pumax-pumin... … … … … … … … … … … … … … … … … … (17)

In following ST13, it is determined whether the pulse wave amplitude Ap (n) is increasing. If the pulse amplitude Ap (n) is increasing, return to ST6 with plug F (indicating that the pulse amplitude Ap (n) is increasing) at ST14 and returning to ST6 to determine the next pulse amplitude Ap (n + 1). Perform the calculation.

In ST13, when it is determined that the pulse wave amplitude Ap (n) is not increasing, it advances to ST15 and determines whether or not said F is 1 (ST15). If F = 1 (pulse amplitude Ap (n) is increasing), go to ST16, otherwise go to ST20. In ST16, the plug F is first set to zero. In ST17, the maximum Apmax is extracted from the pulse wave amplitude Ap (n) data sequence.

In ST18, the pulse amplitude Ap (n) closest to the threshold of 60% of the maximum pulse amplitude Apmax is searched for, and the corresponding cuff pressure Pe (i) is the highest blood pressure candidate value S. In ST19, a correction operation is performed on the highest blood pressure candidate value S based on the above formula (5) to obtain the highest blood pressure value sys. Returning to ST6, the pulse wave amplitude Ap (n) data is collected.

As before, the processing from ST6 to ST12 is performed to calculate the pulse amplitude Ap (n). In ST13, the pulse amplitude Ap (n) is in the process of decreasing, so it is advanced to ST13. In addition, since the plug F is set to 0 in ST16, it is determined as "no" in ST15 and advances to ST20.

In ST20, it is determined whether or not the pulse amplitude amplitude Ap (n) is less than 70% of the maximum pulse amplitude amplitude Apmax. If this determination is "no", it returns to ST6 and calculates the next pulse wave amplitude Ap (n + 1).

In step ST20, when YES is determined, the process advances to ST21. The ST21 searches for the pulse amplitude Ap (n) closest to the threshold, which is 70% of the maximum pulse amplitude Apmax (but after the appearance of the maximum pulse amplitude Apmax), and corresponds to the corresponding cuff pressure Pc (i) as the lowest blood pressure candidate. Let's say D. Then, in ST22, correction operation is performed on the lowest blood pressure candidate value D based on Equation (8) above to obtain the lowest blood pressure value DIA.

Subsequently, in ST23, the MPU 14 causes the indicator 5 to display the SYS and the DIA. Finally, in ST24, the MPU 14 commands the exhaust valve 10 to open the rapid exhaust valve, rapidly exhausts the cuff 2, and ends the measurement.

4 (a) shows the relationship between the highest blood pressure value SYS measured by the electronic blood pressure monitor 1 of this embodiment and the highest blood pressure value S _AUS measured by the stethoscope method at the same time. The point envisioned in 4th (a) lies on the straight line Ls shown as approximately SYS = S _AUS . As a result, the systemic error of the highest blood pressure value SYS is eliminated, and as a conventional method, the blood pressure is not lowered to some extent for high blood pressure patients and to some extent for high blood pressure patients.

Similarly, FIG. 4 (b) shows the relationship between the lowest blood pressure value DIA measured by the electronic blood pressure monitor 1 of this embodiment and the lowest blood pressure value D _AUS measured by the stethoscope method at the same time. The viscosity envisaged in FIG. 4 (b) is raised on a straight line L _D expressed as approximately DIA = D _AUS .

In this case, the minimum blood pressure value DIA is excluded from the systematic error, and it is not measured to some extent low for hypertensive patients and to some extent high for hypotension patients as in the prior art.

In the above embodiment, 60% and 70% of the maximum pulse wave amplitude are used as the threshold for blood pressure determination, but the present invention is not limited thereto.

In addition, the numerical values of the constants a _s and b _s of the correction equation (5) and the constants a _D and b _D of the correction equation (8) are not limited to those shown here, but can be changed appropriately with the change in the threshold. have.

The electronic sphygmomanometer of the present invention is characterized by the fact that the blood pressure value correction means for performing a predetermined correction operation is provided on at least one of the highest blood pressure value and the lowest blood pressure value determined by the blood pressure value determination means, so that the system error caused when the blood pressure value is determined by the vibration method is determined. Excluding the hypertension patients and hypotension patients have the advantage that can accurately measure the blood pressure value.

Claims (3)

A cuff, pressurizing means for pressurizing the fluid in the cuff, decompression means for depressurizing the fluid in the cuff, pressure detecting means for detecting the fluid pressure in the cuff, and pulse wave components included in the output signal of the pressure detecting means Pulse wave component detection means for detecting a pulse wave amplitude detection means for calculating a pulse wave amplitude value from the pulse wave component detected by the pulse wave component detection means, an output signal of the pulse wave amplitude calculation means and an output signal of the pressure detection means. An electronic sphygmomanometer comprising: a blood pressure value determining means for determining a maximum blood pressure value and a minimum blood pressure value based on the blood pressure value correcting means for performing a predetermined correction operation on at least one of the highest blood pressure value and the lowest blood pressure value determined by the blood pressure value determining means. Electronic sphygmomanometer characterized in that it was installed. The electronic blood pressure monitor according to claim 1, wherein said blood pressure value correcting means performs a correction operation on the highest blood pressure value based on a correction equation expressed by a first equation of the highest blood pressure value determined by said blood pressure value determining means. The electronic blood pressure monitor according to claim 1 or 2, wherein the blood pressure value correcting means performs a correction operation on the lowest blood pressure value based on a correction equation expressed by a first equation of the lowest blood pressure value determined by the blood pressure value determining means.

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