JPH0557850B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention relates to an electronic blood pressure monitor, particularly an electronic blood pressure monitor for vibration method sampling.

(b) Conventional technology Electronic blood pressure monitors use a cuff that is wrapped around the upper arm, and in the process of pressurizing the cuff to a predetermined value and then decreasing the pressure, the electronic blood pressure monitor collects waveform information about the cuff pressure and the pulse wave component contained in the cuff pressure. Based on this, there is a method that uses the so-called oscillatory method to determine mean blood pressure, systolic blood pressure, and diastolic blood pressure. This type of electronic sphygmomanometer detects the DC component of the cuff pressure signal, which is depressurized by slow evacuation, as shown in Figure 6a, and extracts the pulse wave component contained in this cuff pressure signal. Figure 6b], find the maximum pulse width for each beat of this pulse wave component, use this maximum pulse width as a parameter, arrange it in time series (or cuff pressure series), and create the envelope shown in Figure 6c. A blood pressure value is determined from this envelope and the above-mentioned cuff pressure DC component. There are various algorithms for determining blood pressure, but for example, the cuff pressure corresponding to the maximum point of the parameter (envelope) is the average blood pressure, and the cuff pressure on the high pressure side corresponding to the parameter corresponding to 50% of the maximum value point is the cuff pressure. The systolic blood pressure is determined as the diastolic blood pressure, and the cuff pressure on the low pressure side corresponding to the parameter corresponding to 70% of the maximum point is determined as the diastolic blood pressure.

In addition, there is a method in which parameters are determined by dividing into fixed periods, and the difference between the maximum and minimum values of cuff pressure for each period is determined and used as the pulse wave parameter for that period.

(C) Problems to be Solved by the Invention In the electronic blood pressure monitor employing the vibration method described above, the time series of parameters in a normal case, or the distribution corresponding to cuff pressure changes, is the distribution shown in Figure 6c.
For example, an abnormal distribution as shown in FIG. 6d may occur due to arm movement or the like. If such an abnormal distribution occurs and blood pressure is determined by applying a normal algorithm, there is a problem in that a large error will occur in the measurement results. This problem can be solved by using Figure 7.
To explain more specifically, the parameter is the dashed line a
In the case of normal distribution, the pressure corresponding to the parameter corresponding to 50% of the peak of the parameter as shown in
SYS ₁ is the correct systolic blood pressure. However, if abnormal distribution b occurs, 50% of the peak of the parameter
The pressure corresponding to the parameter corresponding to is SYS ₂ , and the measurement result will be higher than in the case of normal distribution.

In view of the above, it is an object of the present invention to provide an electronic blood pressure monitor that does not cause measurement errors even when an abnormality occurs in the parameter distribution.

(d) Means for Solving Problems The electronic blood pressure monitor of the present invention, as schematically shown in FIG. 1, includes a cuff 1 and a pressure system 2 connected to the cuff for pressurizing or depressurizing the cuff. , a success sensor 3 that detects the cuff pressure, a pulse wave parameter extraction means 4 that extracts parameters within a predetermined section of the pulse wave component included in the cuff pressure for each section, and a In an electronic sphygmomanometer including a blood pressure determining means 5 for determining blood pressure, a first determination is made in which the current parameter value is compared with the previous parameter value to determine whether the current parameter value is larger. means 6, first difference calculation means 7 that calculates a difference value by subtracting the previous parameter value from the current parameter, and a first difference calculation means 7 that determines whether the first difference value is greater than or equal to a predetermined value. 2 discriminating means 8, and 1
Second difference value calculating means 9 for calculating a difference value by subtracting the parameter value two times before from the parameter value before the second time
and a third determining means for determining whether the first difference value is larger than the second difference value by an equivalent value or not, and outputs of the first, second and third determining means are all affirmative. It is characteristically equipped with an abnormality processing means for abnormally processing the current parameter when .

(E) Effect In this electronic blood pressure monitor, if the parameters extracted by the pulse wave parameter extraction means 4 have the distribution shown in FIG.
Hi and the parameter value H(i-1) at the previous time point t(i-1) are compared by the first determining means 6, and H
If (i)>H(i-1), there is a probability that the parameter value is increasing and is abnormal. Also, the current parameter value H(i) and the previous parameter value H(i-
The difference value K1=H(i)−H(i−1) of 1) is calculated by the first difference value calculation means 7, and this difference value _K1 is compared with a predetermined value by the second discrimination means 8. . If the difference value K1 is abnormal by a predetermined value, it means that the rate of increase in the parameter value is large, and the probability that the current parameter value is abnormal becomes even higher. However, the rate of increase in parameters may be large depending on the time point even when the condition is normal. Therefore, the previous parameter value H
The difference value K2=H(i-1)-H(i-2) between (i-1) and the parameter value H(i-2) two times before is calculated by the second difference value calculation means 9, The determining means 10 of No. 3 compares whether the difference value K1 is considerably larger than the difference value K2. If K1>α・K2 [α: constant],
This means that the parameter value has further increased rapidly this time, and with the positive outputs of the first, second, and third determining means, the current parameter value is determined to be abnormal, and the current parameter value correction or abnormality notification etc. abnormality processing is performed.

(f) Examples The present invention will be explained in more detail below using examples.

FIG. 2 is a block diagram of an electronic blood pressure monitor in which the present invention is implemented. In the figure, a cuff 11 is a rubber bag to be wrapped around the arm, and is connected to an exhaust valve 13 and a pressure pump 14, which constitute a pressure system 12, through a rubber tube 15. Further, the pressure sensor 16 is also communicated with the cuff 11 through the rubber tube 15.
Converts cuff pressure into an electrical signal. The output end of the pressure sensor 16 is connected to the input end of an amplifier 17, and the output electrical signal of the pressure sensor 16, that is, the cuff pressure signal, is DC amplified by the amplifier 17. The output terminal of the amplifier 17 is connected to one input terminal of the A/D converter 18 and also to the input terminal of the bandpass filter 19. The output end of the A/D converter 18 is the CPU
20 , and the output of the amplifier 17 and the output of the bandpass filter 19 are respectively converted into digital signals by the A/D converter 18 and taken into the CPU 19 .

The CPU 20 executes predetermined processing according to the built-in program, and
It has a function to extract each parameter (level difference between maximum value and minimum value), and a function to determine blood pressure values such as systolic blood pressure and diastolic blood pressure from cuff pressure and parameters.
The determined blood pressure value is displayed on the display section 11.
In addition to the above-mentioned general functions, this CPU 10 has a parameter value correction function.

Furthermore, when a measurement start key (not shown) is operated, the CPU 20 starts operating the pressurizing pump 14 to pressurize the cuff 11 in response to a command a, and controls the displacement of the exhaust valve 13 in accordance with a command b. do. Further, the cuff pressure from the amplifier 17 and the pulse wave component from the bandpass filter 19 are read at a predetermined sampling period according to commands c and d.

Below, with reference to the control flow diagram shown in Figure 3,
The overall operation of the electronic sphygmomanometer according to the embodiment will be explained.

When a measurement start key (not shown) is pressed to start operation, the pressurizing pump 14 starts operating in response to command a [step ST (hereinafter abbreviated as ST) 1], and the cuff is pumped until the cuff pressure reaches sufficient for measurement. 11 is pressurized (ST2). When the cuff pressure reaches a predetermined cuff pressure, the operation of the pressurizing pump 14 is stopped and pressurization is stopped (ST3), and at the same time, the exhaust valve 13 is evacuated at a slow speed according to command b, and depressurization is started (ST4). Then, initial settings for parameter calculation are performed, such as clearing counters for calculating each parameter and registers for storing the maximum and minimum cuff pressure values (ST5). Next, parameters are calculated in ST6. This parameter calculation involves determining the maximum and minimum values of the cuff pressure that are sampled and taken in each predetermined time interval (window) within that interval, and calculating the difference between them as the parameter value for that interval. . Through this calculation process, the uncorrected parameter H(i) shown in FIG. 5 is obtained.

If the calculated parameter (i) is greater than or equal to
The parameters are corrected in ST7. This correction is the most characteristic feature of the present invention, and details will be described later.

After processing for correction, the parameter value H(i) calculated this time is compared with the maximum parameter amount Hmax up to that point (ST8), and if H(i)>Hmax,
Set the current parameter H(i) to the new parameter maximum value
Store it as Hmax (ST9), determine the cuff pressure corresponding to that point as the average blood pressure (ST10), and
The cuff pressure corresponding to a parameter value of, for example, 1/2 of the maximum parameter value Hmax is determined as the maximum blood pressure (ST11).

Next, it is determined whether the current parameter value H _(i) has become 70% or less of the previous parameter maximum value Hmax (ST12). At the stage where the parameter is increasing, this judgment becomes NO, and the section counter i is +
1 (ST13), returns to ST6, calculates parameters for the next section (ST6), and performs parameter correction (ST7). After that, the parameter value turns from rising to falling and continues from ST6 until H(i)<70% of Hmax.
The process of ST13 is repeated.

Eventually the parameter H(i) reaches 70% of Hmax,
If it becomes even smaller than this, the ST12 judgment will be
YES, the cuff pressure corresponding to this point is determined to be the diastolic blood pressure (ST14), and then the determined average, maximum, and minimum blood pressure values are displayed on the display 11 (ST15), and the exhaust valve 13 is rapidly closed. It is exhausted (ST16) and the measurement ends.

Next, details of the parameter correction process in ST7 will be explained with reference to the flowchart in FIG. 4.

When entering the parameter correction subroutine, the
In ST71, the current parameter value H _(i) and the previous parameter value H (i-1) are compared, and the current parameter value H _(i) is larger than the previous parameter value H (i-1). It is determined whether or not (first determining means). If H(i)>H(i-1), the parameter is increasing as shown in FIG. Fifth
As shown in H(i) in the figure, if there is an abnormal and rapid increase,
The judgment in ST71 becomes YES, and then in ST72 the current parameter value H(i) and the previous parameter value H(i
-1) is calculated (first difference value calculation means). Next, in ST73, the difference value K1 is set to a predetermined value x (x=
0.5 to 1 mmHg) or more (second determining means). If the difference value K1 is greater than or equal to the predetermined value x, it means that the current parameter has increased significantly compared to the previous time. As shown in H(i) in Figure 5, if there is an abnormal and rapid increase, the judgment of ST73 will be YES,
Next, in ST74, a difference value K2 between the previous parameter value H(i-1) and the second previous parameter value H(i-2) is calculated (second difference value calculation means). And ST75
It is determined whether K2=0 or not. Here, if K2 = 0, that is, if H(i-1) = H(i-2), the minimum unit y of H(i) is set to K2 (ST76), and the following
Move to ST77. If K2≠0 in ST75, immediately move to ST77.
Move to. Entering y as K2 in ST76 is
This is because when K2=0, the determination of ST77 becomes impossible. In ST77, it is determined whether the difference value K1 is greater than three times the difference value K2 (third determination means). If the difference value K1 is larger than three times the difference value K2, it means that the parameter has suddenly increased this time. The triple value of 3 used here is determined empirically, and other appropriate constants may be selected depending on the case. In the determination of K1≧x in ST73, the parameter may change with a steep slope even if it is normal, so in ST77, a further comparison with the difference value K2 is performed. It is detected that there has been a change in H in Figure 5
If the gradient suddenly changes due to an abnormality like (i), then
The judgment of ST77 becomes YES.

As described above, “H(i)>H(i−
1)?”, ST73’s “K1≧x?”, ST77’s “K ₁ >
3×K ₂ ?'' is YES, it is determined that the parameter value H(i) is abnormal, and in ST78,
By adding K2 to the parameter value H(i), a corrected H(i) [H(i)' in FIG. 5] is obtained. Then, return from this subroutine.

Furthermore, if any of the judgments in ST71, ST73, and ST77 is NO, the process returns without correction.

In the above embodiment, when the parameter value H(i) is abnormal, a correction calculation is performed in ST78, but the abnormality notification may be made without performing this calculation.

Further, in the above embodiment, a case has been described in which parameters are determined for each fixed time interval (window), but the present invention can of course also be applied to a method in which parameters are determined using one beat of the pulse wave as one interval.

(G) Effects of the Invention According to the present invention, when an abnormality occurs in pulse wave waveform information due to arm movement, etc., this abnormality is detected, so it is possible to prevent measurement errors caused by abnormal waveforms. .

In addition, in a device that performs correction calculations based on abnormality detection, substantially accurate measurements can be made even when an abnormality occurs in the pulse waveform.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of the present invention, Fig. 2 is a block diagram of an electronic blood pressure monitor in which the invention is implemented, Fig. 3 is a control flow diagram of the electronic blood pressure monitor, and Fig. 4 is a control flow diagram of the electronic blood pressure monitor. A control flow diagram showing the parameter correction routine of the flow in more detail, FIG. 5 is a diagram showing an example of parameter distribution to explain the operation of the electronic blood pressure monitor, and FIG. 6 a, b, c, and d are vibration FIG. 7 is a diagram illustrating a time chart for explaining the principle of an electronic sphygmomanometer adopting the method, and is a diagram illustrating a problem in the abnormal distribution of parameters of a conventional electronic sphygmomanometer. 1: Cuff, 2: Pressure system, 3: Pressure sensor, 4:
Pulse wave parameter extraction means, 5: Blood pressure determination means,
6: first discrimination means, 7: first difference value calculation means,
8: second discrimination means, 9: second difference value calculation means,
10: Third discrimination means.

Claims (1)

[Claims] 1. A cuff, a pressure system connected to the cuff for pressurizing or depressurizing the cuff, a pressure sensor for detecting cuff pressure, and a predetermined section of pulse wave components included in the cuff pressure. In an electronic blood pressure monitor, the electronic blood pressure monitor includes a pulse wave parameter extracting means for extracting the parameters in each interval, and a blood pressure determining means for determining the blood pressure based on the cuff pressure and the pulse wave parameter. a first determining means that compares the parameter value of the current parameter value with the parameter value of the current parameter value and determines whether the current parameter value is larger; 1 difference value calculating means; second determining means for determining whether the first difference value is greater than or equal to a predetermined value; and a difference value obtained by subtracting the second previous parameter value from the first previous parameter value. a second difference value calculating means for calculating a value; a third determining means for determining whether the first difference value is larger than the second difference value by an equivalent value; and the first and second difference values. and abnormality processing means for abnormally processing the current parameter value when both outputs of the third determination means are positive. 2. The electronic blood pressure monitor according to claim 1, wherein the abnormality processing by the abnormality processing means is to add the second difference value to the previous parameter to obtain the current correction parameter value.