JPH0636786B2 - Electronic blood pressure monitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic blood pressure monitor of an amplitude method for measuring a blood pressure value from the amplitude value of a pulse wave.

(B) Conventional technology Generally, this type of electronic sphygmomanometer supplies pressurized air to a cuff wound around an arm or the like from a pressure pump to interrupt the blood of the arm or the like, and then supplies this pressurized air. Exhaust at a very low speed from the exhaust valve, and the pressure in the cuff is detected by the pressure sensor during this exhaust,
It is configured to detect the pulse wave component from this pressure. Then, the CPU calculates the pulse wave amplitude value from the pulse wave component, and calculates and displays the maximum and minimum blood pressure values from the amplitude value and the cuff pressure.

This amplitude value sets a window which is a time section of a predetermined length in order to minimize the memory capacity in the CPU,
For each successive window, the difference is obtained from the maximum value and the minimum value of the pulse wave signal in the window. This difference is referred to as a parameter as a representative value of the amplitude value in each window, and the blood pressure value is calculated and displayed based on the continuously obtained parameters.

(C) Problems to be solved by the invention In the electronic blood pressure monitor described above, conventionally, the length of the window is fixed, but in this window, the maximum value of the pulse wave signal is obtained in order to obtain the pulse wave amplitude value. And the minimum value, and the pulse wave signal for at least one beat needs to be included. Therefore, when setting this window, it was made long so that even a person with a slow pulse could measure it.

However, if the window is lengthened, the time for obtaining one parameter becomes long, and the number of obtained parameters decreases, so that there is a problem that the measurement accuracy of the blood pressure value deteriorates.
Therefore, in order to improve the accuracy, the exhaust speed in the cuff is slowed down, but this causes a problem that the measurement time becomes long.

In addition, in a person with a fast pulse, even if it is possible to perform highly accurate measurement even at a distant exhaust speed, since the window length is constant, it takes a long time to measure, and unnecessary pain such as an ischemic state is caused. Was supposed to give.

(D) Means for Solving Problems As shown in FIG. 1, the present invention provides a cuff A, a pressurizing means for supplying pressurized air to the cuff A, and a pressurized air for the cuff A. Exhaust means C for slowly or rapidly exhausting, and the cuff A
Pressure detecting means D for detecting the pressure of the cuff A, pulse wave detecting means E for detecting the pulse wave component from the pressure of the cuff A, and cycle calculating means for calculating the pulse wave cycle from the signal of the pulse wave detecting means E. A window setting means for setting a window that is a time section for calculating a pulse wave amplitude value corresponding to the pulse wave period, and a parameter calculating means for calculating a parameter that is a representative value of the pulse wave amplitude value for each window. The exhaust speed setting means I sets the exhaust speed of the exhaust means according to the length of the window, and the blood pressure calculation means calculates the maximum and minimum blood pressure values from the parameters and the cuff pressure.

(E) Action In the electronic sphygmomanometer of the present invention, after the pressurized air is supplied to the cuff A by the pressurizing means B, the pressurized air is exhausted by the exhausting means C at a very low speed, and the pressure detecting means D causes the inside of the cuff A to be discharged. In addition to detecting the pressure, the pulse wave detecting means E detects the pulse wave component, the period calculating means F calculates the pulse wave period from the signal of the pulse wave component, and then the window setting means G calculates the pulse wave amplitude value. Corresponding to the pulse wave cycle, the window, which is the time interval, is set to be long when the cycle is large and short when it is small,
While calculating each of these parameters by the parameter calculating means H, the exhaust speed of the exhaust means is set by the exhaust speed setting means I to be slow when it is long and fast when it is short. The maximum and minimum blood pressure values are calculated by the blood pressure calculating means J from the parameters and the cuff pressure.

(F) Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, 1 is an electronic blood pressure monitor, and a cuff 2
A sphygmomanometer using a vibration method, in which the pulse wave amplitude value is detected and the blood pressure value is measured from this amplitude value while the pressurized air supplied to is discharged at a slow speed.

The cuff 2 is wound around an upper arm portion or the like, and is connected to a pressurizing pump (pressurizing means) 3 and an exhaust valve (exhaust means) 4 via an air pipe 5. The pressurizing pump 3 supplies pressurized air to the cuff 2 to block blood in the upper arm and the like, while the exhaust valve 4 exhausts the pressurized air at a slow speed or a rapid speed.

Further, a pressure sensor (pressure detecting means) 6 is linked to the cuff 2 so as to detect the pressure in the cuff 2 and output it as a cuff pressure signal. This cuff signal is input as a digital signal to the CPU 9 through the amplifier 7 and the A / D converter 8, while the amplifier 7 outputs the bandpass filter 1
Input to 0. The band pass filter 10 is a pulse wave detecting means for extracting a pulse wave component from the cuff pressure signal, and outputs the pulse wave signal. This pulse wave signal is
It is input as a digital signal to the CPU 9 through the A / D converter 8.

This CPU 9 has a built-in memory such as RAM and ROM,
The signal processing is performed according to the program stored in the ROM, and parameters such as pulse wave amplitude values, which will be described later, are extracted and the maximum blood pressure value, the average blood pressure value, and the minimum blood pressure value are determined. Also, this CPU 9 is a start switch 1
The switching signal is input from the control signal 1 and the control signals a and b are output to the pressurizing pump 3 and the exhaust valve 4 so that the pressurizing pump 3 is driven and stopped, while the exhaust valve 4 is exhausted at a very low speed or rapidly. Is configured. Furthermore, CPU9
A display unit 12 is connected to the display unit to display the maximum and minimum blood pressure values and the average blood pressure value.

Here, a method of determining the maximum and minimum blood pressure values will be described.

This electronic sphygmomanometer 1 adopts the vibration method, calculates a pulse wave amplitude value (parameter) from the pulse wave signal obtained by the band pass filter 10, and the envelope curve of this pulse wave amplitude value is the cuff 2's envelope curve. In the depressurization process, the bell shape is formed as shown in FIG. Although the blood pressure value is determined using this envelope curve, various determination methods have been proposed, and each blood pressure value is as follows, showing an example adopted in this embodiment.

Average blood pressure value: Cuff pressure at point M where the pulse wave amplitude value is maximum Maximum blood pressure value: In a region where the cuff pressure is higher than the average blood pressure value (the rising process of the pulse wave amplitude value), the pulse wave amplitude value is the maximum value M Cuff pressure at point N at 50% The minimum blood pressure value: Cuff at point L at which the pulse wave amplitude value is 70% of the maximum value M in the region where the cuff pressure is lower than the average blood pressure value (falling process of the pulse wave amplitude value). Pressure Next, the configuration and operation of the electronic sphygmomanometer 1 will be described based on the flow charts shown in FIGS. 4 to 8. The step is called ST.

First, in the main routine of FIG. 4, when the start switch 11 is turned on in ST1, the control signal a is output from the CPU 9, the pressurizing pump 3 is driven, and pressurized air is supplied to the cuff 2. The pressure in the cuff 2 is detected by the pressure sensor 6, and when the predetermined cuff pressure is reached, the CPU 9 recognizes it (ST2), outputs the control signal a, and stops the pressurizing pump 3 (ST3). After that, the CPU 9 outputs the control signal b, the exhaust valve 4 starts the slow speed exhaust (ST4), and the blood pressure measurement is started. At the time of this start, the exhaust speed of the exhaust valve 4 is controlled to be the slowest within the certifiable range.

Subsequently, initial setting is performed to calculate the parameter H (ST5), and thereafter, calculation of the parameter H and the amplitude cycle T
A series of processes such as calculation of _M , determination of blood pressure value, setting of exhaust speed, etc. are performed by ST6 to ST14.

Explaining the terms such as the parameter H, the parameter H is a representative value of the pulse wave amplitude value in one window, and one parameter H is calculated for each window. This window is a measurement time, that is, a time section in which the decompression process of the cuff pressure is divided into short time in order to minimize the memory capacity, the pulse wave amplitude is calculated for each window, and one parameter H is determined. To be done.

Returning the explanation to the flow of FIG. 4, the parameter H is from ST6 to
It is calculated each time the process in ST14 is performed, the number of times is indicated by i, and is stored in the memory of the CPU 9 together with the cuff pressure Wi at that time. Then, the processing of ST6 to ST14 is repeated until the average and systolic blood pressure values are determined, and it is determined that the diastolic blood pressure value can be determined (ST11).

That is, in ST6, a subroutine described later is read to read cuff pressure data and pulse wave data, and pulse wave period T
_M is calculated, and the parameter H is calculated (parameter calculating means H). This calculated last pamelator Hi and the previously obtained parameters H _{1 to} H
The maximum value Hmax of _i-1 is compared (ST7), and Hmax <
When Hi, the envelope curve of the pulse wave amplitude value is in the ascending process, and S
One method to move to T8, when Hmax> Hi, it is in the descending process,
It will move to ST11. In this ST8, the maximum value Hmax of the parameter H is sequentially updated, and the cuff pressure Wi at the time point corresponding to the maximum value Hmax is set as the average blood pressure value (ST9), and the time point corresponding to the parameter H closest to 50% of the maximum value Hmax. The cuff pressure A is set as the maximum blood pressure value (ST10). The both blood pressure values are updated each time the processes of ST6 to ST14 are repeated, and when the maximum value M of the envelope curve of the pulse wave amplitude value is reached, the maximum value Hmax of the parameter H is determined, and the average blood pressure value is determined. And the maximum blood pressure value is finally determined (blood pressure calculating means J).

Next, the parameter Hi decreases and the envelope curve descends, and it is determined whether or not the parameter Hi becomes smaller than 70% of the maximum value Hmax (ST11). When it becomes smaller, the process moves to ST15 and 70% or less thereof. When the cuff pressure Wi at the time of becomes the minimum blood pressure value (blood pressure calculation means J), the above-mentioned maximum blood pressure value and average blood pressure value are displayed on the display 12 (ST
16), the control signal b is output from the CPU 9, and the exhaust valve 4
Is rapidly exhausted (ST17), the pressurized air in the cuff 2 is discharged, and the blood pressure measurement ends.

In ST11, the process proceeds to ST12 until 70% is reached, and the next parameter H _{i + 1} is prepared for calculation.
In the above, the setting of the window length and the setting of the exhaust speed, which will be described later, are performed every time one parameter H is calculated.

Next, the parameter calculation processing in ST6 will be described based on the flow of the subroutine shown in FIG. This subroutine calculates the difference between the maximum value and the minimum value of the pulse wave data P in each window as a parameter H (amplitude value), and sets the cuff pressure W at the end of the window as the cuff pressure corresponding to the parameter H. On the other hand, the pulse wave period T _M in the vicinity of each window is calculated. First, in ST601, the maximum value Pmax and the minimum value Pmin of the pulse wave in each window are set to 0, and the counter n, which is the number of times of reading data, is initialized to 1. And S
At T602, the pulse wave data Pn, that is, the output signal of the bandpass filter 10 is read. This reading is 10
It is performed every msec, and the pulse wave data Pn is stored in the memory of the CPU 9. The read pulse wave data Pn is compared with the previous pulse wave data P _{1 to} P _n-1 in each window (ST603, ST605), and the minimum value P _min and the maximum value P max are set (ST 604, 606) and thereafter, when the pulse wave data Pn becomes smaller than the minimum value P _min and becomes larger than the maximum value Pmax, the minimum value Pmin and the maximum value Pmax are updated respectively.

Then, the process shifts to a subroutine for paying out the pulse wave period T _M (ST607). This subroutine will be described later, and the process proceeds to ST608, where the reading number counter n
After adding 1 to, the maximum number of data in each window n
Compared with _max (ST609), when the upper limit n _max is not reached, the process returns to ST602, and the operations of ST602 to ST609 are repeated until the upper limit n _max is reached.
The upper limit n _max indicates the length of the window by the number of the counter n, and is set in ST13 described later.

When the counter n of the number of pulse wave data reaches the upper limit n _max , one window ends, the process moves to S610, and the difference between the maximum value Pmax and the minimum value Pmin of the pulse wave data is stored in the memory of the CPU 9 as a parameter Hi. Along with
The cuff pressure Ai at the end of the window is stored in the memory as the cuff pressure corresponding to this parameter Hi (ST611).
As a result, the processing routine for calculating the parameter H ends, and the process moves to ST7 described above.
Two parameters H are calculated.

Next, the pulse wave cycle calculation process (cycle calculation means F) in ST607 will be described based on the flow of the subroutine shown in FIG. In this subroutine, the pulse wave period T _M per beat is calculated, and the window length and the exhaust velocity are set in correspondence with this period T _M (ST13, ST14).

First, in ST621, a timer T _M indicating the pulse wave period is displayed.
Is incremented by 1. As described above, this subroutine is called every time one pulse wave data Pn is read in ST607, so the timer T _M is a timer of 10 msec unit. Subsequently, in ST622, it is determined whether or not the pulse wave is recognized. If not recognized, this subroutine ends and returns to ST608, while if recognized, ST623.
Will move to. Although various determinations can be made for this recognition, as shown in FIG. 9, for example, a threshold level TH is set for the pulse wave data Pn and the pulse wave data Pn
The intersections C _{1 to} C ₇ where the rising process of C intersects with the threshold level TH are recognition points. Therefore, there is one beat from one recognition point to the next recognition point, which is one pulse wave period T _M.

Then, in ST623, the pulse wave period T which is the pulse rate.
The counter K for the number of times _M is incremented by 1, and this subroutine ends and returns to ST608 until this counter K reaches 5, while when it reaches 5, it moves to ST625 and divides the pulse wave period T _M by 5 Then, the average pulse wave period T _P is calculated and stored in the memory of the CPU 9. After that, the pulse wave period T
Initialization is performed by setting _M and the counter K to 0 (ST6).
26, ST627), whereby the pulse wave period calculation routine ends. Therefore, since this subroutine is called and processed every 10 _msec , the pulse wave period T _M is indicated by the number of readings n of the pulse wave data Pn, and is newly set every 5 pulses. Become.

Next, the window length setting process (window setting means G) in ST13 will be described with reference to FIG. This window length n _max is the average pulse wave period T obtained in ST625.
It is set using _P and is set to a length of n _max = T _P × 1.1. This window is for calculating one parameter H, and originally, it is enough that one window includes one beat, that is, one pulse wave period T _{P, and} therefore n _max = T
_P is good. However, the surroundings of the pulse wave may fluctuate due to various conditions on the living body side such as arrhythmia and arm movement. Therefore, T _P × 1.1 is set as described above (ST13).
1).

Finally, the exhaust speed setting process (exhaust speed setting means I) in ST14 will be described with reference to FIG. The exhaust speed is calculated and controlled according to the window length n _max . That is, in order to set the minimum pulse rate to 40 beats / minute and to set the pressure reading interval to 4 mmHg, the average pulse wave period T _P becomes 150 and the window length n _max becomes 165.
Therefore, the reading of pressure is done at the end of one window,
It is sufficient to exhaust 4 mmHg per 1560 msec. The pumping speed in this case is 4/1650 ≒ 2.5 mmHg / s
It becomes ec. Therefore, in order to always keep the pressure reading interval at 4 mmHg, the pressure may be set to 2.5 × 165 (mmHg / sec).
(ST141).

These window lengths and pumping speeds will be newly set every 5 beats, and will be sequentially updated during the measurement.

In this embodiment, the pressure is read every 4 mmHg as the exhaust speed, but the present invention is not limited to this.

Further, it goes without saying that the window length is not limited to that in the embodiment.

(G) Effect of the Invention As described above, according to the electronic sphygmomanometer of the present invention, while detecting the pulse wave cycle, while setting the window from this cycle,
Since the exhaust speed is set according to the length of the window, the parameter can be obtained several times even if the pulse rate is different, so that the measurement can be always performed with good accuracy.

In addition, the pumping speed varies depending on the pulse rate, which is faster when the pulse rate is high and slower when the pulse rate is low, so the measurement time can be shortened, preventing unnecessary pain to the person being measured. can do.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of the present invention, FIGS. 2 to 9 show an embodiment of the present invention, FIG. 2 is a block diagram of an electronic blood pressure monitor, and FIG. FIG. 4 is a flow chart showing a main routine of the electronic sphygmomanometer, FIG. 5 is a flow chart showing a parameter calculation processing routine, and FIG. 6 is a pulse wave cycle calculation processing routine. 7 is a flow chart showing a window length setting processing routine, FIG. 8 is a flow chart showing an exhaust speed setting processing routine, and FIG. 9 is pulse wave data. A (2): cuff, B (3): pressurizing means, C (4): exhausting means, D (6): pressure detecting means, E (10): cycle calculating means F: cycle calculating means, G: window Setting means, H: Parameter setting means, I: Exhaust speed setting means, J: Blood pressure calculating means.

Claims (1)

[Claims] 1. A cuff, a pressurizing means for supplying pressurized air to the cuff, an exhausting means for exhausting the pressurized air in the cuff at a slow speed or a rapid speed, and a pressure detecting means for detecting the pressure in the cuff. A pulse wave detecting means for detecting a pulse wave component from the pressure in the cuff, a cycle calculating means for calculating a pulse wave cycle from a signal of the pulse wave detecting means, and a pulse wave amplitude corresponding to the pulse wave cycle. A window setting means for setting a window that is a time section for calculating a value, a parameter calculating means for calculating a parameter that is a representative value of a pulse wave amplitude value for each window, and the window corresponding to the length of the window. An electronic sphygmomanometer comprising an exhaust speed setting means for setting the exhaust speed of the exhaust means and blood pressure calculating means for calculating the maximum and minimum blood pressure values from the parameters and the cuff pressure.