JP3042051B2 - Electronic sphygmomanometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillometric sphygmomanometer.

[0002]

2. Description of the Related Art In an oscillometric sphygmomanometer, for example, the cuff pressure is changed with time (see FIG. 5A), and the amplitude of a pulse wave superimposed on the cuff pressure is changed (see FIG. 5B). There is one that calculates the blood pressure from the data. FIG. 5B shows a change in pulse wave amplitude in the process of reducing the cuff pressure of such a sphygmomanometer, where point P is the maximum amplitude point ( _AMAX ).
Is shown. The point D is set at 0. 0 relative to the maximum amplitude point.
A point having an amplitude of 7A _MAX and an S point having an amplitude of 0.5A _MAX with respect to the maximum amplitude point. Then, for example, from the point of view of the FIG. 5 in FIG. 5 corresponding to the S point and the D point (b) (a), systolic blood pressure (the systolic blood pressure) has determined the amplitude period blood pressure (diastolic blood pressure).

In the oscillometric sphygmomanometer, the blood pressure value is determined as described above, and therefore, it is necessary to apply a pressure sufficient to detect the point S in FIG. 5 (b). Since it is not possible to predict (systolic blood pressure), it is difficult to set the pressurization stop value to an appropriate value, and it is particularly difficult for a hypertensive subject with severe blood pressure fluctuation. If the pressurization stop value is set to an unnecessarily high value, the subject is forced to suffer.

Therefore, conventionally, when the cuff pressure is pressurized, the cuff pressure signal is captured, and the change in the amplitude of the pulse wave (pulse wave envelope) superimposed on the cuff pressure signal is obtained, thereby simplifying the operation. The systolic pressure was estimated. And the pressurization stop point was automatically set based on the estimated systolic pressure.

[0005]

However, since a high-pass filter is used to separate a pulse wave from a cuff pressure signal on which a pulse wave is superimposed, a point at which the signal changes abruptly, such as at the start of pressurization. There is a problem that a large fluctuation called a transient response occurs, and an envelope for calculating the systolic pressure cannot be normally captured. Specifically, since an abnormal bulge occurs in the low pressure region of the cuff pressure, a very low value is estimated as the systolic pressure, and when the pressurization stop point is set based on this estimated value, There was a problem that blood pressure could not be measured due to lack.

The present invention has been made in view of this problem, and provides a sphygmomanometer capable of estimating a systolic pressure in a process of applying a cuff pressure without being affected by a transient response. The purpose is to do.

[0007]

To achieve the above object, a sphygmomanometer according to the present invention detects a cuff for compressing a living artery, a pressurizing means for pressurizing the cuff, and a pressure in the cuff. A pressure sensor, pulse wave extracting means for extracting a pulse wave component superimposed on the cuff pressure signal from the cuff pressure signal detected by the pressure sensor, and whether predetermined conditions have been satisfied after the start of pressurization
Condition determining means for determining
Operation start control means for starting the operation of the pulse wave extraction means in response to the establishment of the pulse wave;
A systolic pressure estimating means for estimating the systolic pressure based on the signal and the cuff pressure, and the operation of the pressurizing means when a predetermined cuff pressure determined based on the systolic pressure estimated by the systolic pressure estimating means is reached. Pressure stop means for stopping, pressure reducing means for gradually reducing the cuff pressure after the pressure stop, and a blood pressure for extracting a pulse wave signal in the process of reducing the cuff pressure and determining a blood pressure based on the pulse signal and the cuff pressure. Decision means. Condition judgment
The stage detects that the cuff pressure has exceeded the specified value after the start of pressurization.
Cuff pressure detection means, or at a predetermined time from the start of pressurization
It is a time lapse detecting means for detecting that the time has elapsed.
Alternatively, both of them may be provided.

[0008]

The pressurizing means pressurizes the cuff, and the pressure sensor detects the pressure in the cuff (cuff pressure signal on which a pulse wave is superimposed). Then, the pulse wave extracting means extracts a pulse wave component superimposed on this signal from the cuff pressure signals at the time of pressurization and at the time of depressurization. Condition judgment
Steps are performed under predetermined conditions after the start of pressurization, for example, after the start of pressurization.
Either the specified value has been exceeded, or a specified time
Determine if you have missed it. Operation start control means is responsive to the condition satisfied to start the operation of the pulse wave extracting means. Therefore, the pulse wave is not extracted during the transient response, and the systolic pressure estimating means estimates the systolic pressure accurately. The pressurizing stop unit stops pressurizing at a pressurizing stop point determined based on the value of the estimated systolic pressure, and thereafter, the pressure reducing unit gradually reduces the cuff pressure.
The blood pressure determining means determines a blood pressure value based on a change in the amplitude of the pulse wave extracted by the pulse wave extracting means in the cuff pressure reducing process.

[0009]

1 is a block diagram of an electronic sphygmomanometer according to an embodiment of the present invention. This electronic sphygmomanometer includes a cuff 1 for compressing a living artery, a pump 2 for pressurizing the cuff 1, and a cuff 1
Quick exhaust valve 3 for rapidly exhausting the pressure (air pressure), a slow exhaust valve 4 for gradually exhausting the air of the cuff 1, a pressure sensor 5 for detecting the pressure of the cuff 1, and a low-pass filter 6
A / D for converting the output of the pressure sensor 5 into a digital value
A converter 7, an MPU 8 that takes in signals from the A / D converter 7 and performs various processes described later, and a display 9 that displays a measured blood pressure value are provided. The low-pass filter 6 is provided to remove pressure noise of the pressurizing pump 2 mixed in the cuff pressure signal when extracting a pulse wave during pressurization.

FIG. 2 is a general flowchart showing the overall operation of the electronic sphygmomanometer shown in FIG. The pulse wave extraction processing (ST5, ST12) and the pulse wave amplitude calculation processing (ST5)
6, ST13), the blood pressure estimation process (ST7), and the blood pressure calculation process (ST14) are portions that perform the following processes, respectively. Pulse wave extraction processing: This is processing for extracting a pulse wave component superimposed on cuff pressure data from cuff pressure data. Pulse wave amplitude calculation processing: This is processing for calculating the pulse wave amplitude by recognizing the start point and end point of the pulse wave for each beat. Blood pressure estimation process: the maximum value A _MAX of the pulse wave amplitude in pressurization process of the cuff pressure, a subroutine for determining an estimated value SP of systolic pressure based on the maximum value A _MAX of the pulse wave amplitude (Figure 3 reference). Blood pressure calculation processing: This is a subroutine for calculating the systolic blood pressure (systolic pressure) and the diastolic blood pressure (diastolic pressure) from the change in the pulse wave envelope due to the pulse wave amplitude (see FIG. 4).

The operation of the electronic sphygmomanometer shown in FIG. 1 will be described below with reference to the flowchart of FIG. When the operation is started by a start switch or the like, the MPU 8 operates the pump 2
To start pressurization (step ST (hereinafter abbreviated as ST) 1). Next, the MPU 8 detects a signal from the pressure sensor 5 and monitors the increasing pressure (ST2), and determines whether or not the cuff pressure has reached a predetermined value (ST3). If the cuff pressure has not reached the predetermined value, the process returns to ST2, but if the cuff pressure has reached the predetermined value, the process proceeds to the next process (ST4). Then, it is determined whether or not a predetermined time (τ) has elapsed since the start of the measurement. If the predetermined time τ has not elapsed, the process returns to ST2 and waits (ST4). That is, since there are the processes of ST3 and ST4, the process proceeds to the next process ST5 only when the cuff pressure becomes equal to or more than the predetermined value and the predetermined time τ has elapsed.

When the cuff pressure exceeds a predetermined value and a predetermined time has elapsed from the start of pressurization, the processing shifts to pulse wave extraction processing, and the MPU 8
Extracts a pulse wave component from the cuff pressure data (ST5).
After that, the process proceeds to the pulse wave amplitude calculation processing to calculate the pulse wave amplitude for each beat (ST6). Then, a blood pressure estimation process is executed (ST7). In this process, the maximum amplitude value A _MAX is updated or the systolic pressure estimated value SP is obtained (details will be described later). However, the cuff pressure is not sufficiently increased and the systolic pressure estimated value SP is still not obtained. If not found, the process returns to ST5 and repeats ST5 to ST7 (ST8).

When the systolic pressure estimated value SP is obtained, a pressurization stop point (target pressure) is calculated based on the obtained systolic pressure estimated value SP, and pressurization is performed until the pressurization stop point is reached. It lasts (ST9). The pressurization stop point is determined by, for example, the systolic pressure estimated value SP in consideration of the estimation error of the systolic pressure and the pressure drop from immediately after the stop of pressurization to the start of the pulse wave amplitude measurement.
Is set to a value obtained by adding 30 mmHg to. When the pressurization stop point is reached, pressurization is stopped (ST10), and pressure reduction by operation of the slow exhaust valve 4 is started (ST11).

When the process proceeds to the cuff pressure decreasing process, first, a pulse wave to be superimposed on the cuff pressure signal is extracted by a pulse wave extracting process (ST12). Then, the amplitude of the pulse wave is calculated by the pulse wave amplitude calculation process (ST13), and the blood pressure calculation process is performed (ST14). In this blood pressure calculation process, the diastolic pressure DP
May or may not be determined (details will be described later), but the cuff pressure is not sufficiently reduced and the diastolic pressure DP
If the value of has not been obtained, the process returns to ST12 and returns to ST12.
Steps ST15 to ST15 are repeated (ST8). If this process is repeated, the diastolic pressure DP can be determined in due course. Thereafter, the rapid exhaust valve 3 is operated to eliminate the pressure in the cuff (ST16), and the blood pressure value is displayed on the display 9. All processing ends.

FIG. 3 is a flowchart showing the blood pressure estimation process (ST7 in FIG. 2) in more detail. In FIG. 3, AMP (n) indicates the extracted pulse wave amplitude.
n is a pulse wave number indicating the order of the extracted pulse waves. Also, each cuff pressure PC for each pulse wave amplitude AMP (n)
(N) is calculated in the pulse wave amplitude calculation process (ST6) executed immediately before this process. In addition, the pulse wave number n,
The variables A _MAX for obtaining the maximum value of the pulse wave amplitude are both initially set to 0. Hereinafter, the contents of the blood pressure estimation processing will be described with reference to FIG.

First, after updating the pulse wave number n, (S
T21), the pulse wave amplitude AMP (n) is changed to the pulse wave amplitude maximum value A
Compare with _MAX (ST22). Where AMP (n) ≧ A
If it is _MAX, the envelope of the pulse wave is in the ascent process, AMP to A _MAX and does not reach the still maximum point
Substitute the value of (n) (ST23) and return to the main routine. Conversely, when AMP (n) <A _MAX , it is determined that the envelope of the pulse wave amplitude is in the process of decreasing after passing through the maximum point, and the pulse wave amplitude AMP (n) is used to determine the systolic pressure. (ST24). In this embodiment, the threshold value for determining the systolic pressure is set to, for example, 0.5 A _MAX . If AMP (n) ≦ 0.5 A _MAX , the process proceeds to the next process and the estimated value of the systolic pressure ESP Is calculated (ST25). Conversely, if AMP (n)> 0.5A _MAX , the process returns to the main routine without determining the estimated value of the systolic pressure. Since the cuff pressure changes greatly during the pressurization period and the cuff pressure interval between pulse waves is wide, the cuff pressure at the time when the pulse wave amplitude decreases below the threshold value is directly used as the estimated value of the systolic pressure. Then the accuracy is poor. Therefore, in the present embodiment, the estimated value ESP of the systolic pressure is calculated using the following linear complementation equation.

[0017]

(Equation 1)

TH _S in (Expression 1) is a threshold value for determining the systolic pressure. FIG. 4 is a flowchart showing the blood pressure calculation process (ST14 in FIG. 2) in detail. The pulse wave amplitude AMP (n) and the cuff pressure P (n) are calculated based on the pulse wave extraction process (ST12) and the pulse wave amplitude calculation process (ST1).
3) has already been calculated, and the pulse wave number n
And systolic pressure, variable A _MAX for obtaining the maximum value of the variable SP, DP and the pulse wave amplitude for calculating the diastolic pressure is initially set to all zeros.

Hereinafter, based on the flowchart of FIG.
How the systolic pressure and the diastolic pressure are calculated in the process of reducing the cuff pressure will be described. First, the value of the number n of the pulse wave after being updated (ST31), the pulse wave amplitude AMP (n) is compared with the maximum value A _MAX (ST32). If AMP
If (n)> A _MAX , it is determined that the envelope of the pulse wave amplitude has not yet reached the local maximum point, and the process proceeds to ST40 to perform AMP.
After the value of (n) was substituted for the A _MAX, returns to the main routine (ST40).

On the other hand, if AMP (n) ≦ A _MAX, it is determined that the envelope of the pulse wave amplitude has already passed through the maximum point and is in a decreasing process, and the systolic pressure SP is set to the initial value 0. It is determined whether or not it is still (ST33). Here, if SP is other than 0, the systolic pressure SP has already been determined, so the process skips to ST38. Conversely, if SP is 0, the process proceeds to ST34 to determine the systolic pressure SP. Do (S
T33).

That is, the process after ST34 is a process for determining the systolic pressure SP. First, the pulse wave counter j is set to the current pulse wave number n (ST34), the counter j is decremented by one (ST35), and the pulse wave amplitude A designated by j is set.
MP (j) is compared with a threshold value for determining systolic pressure (ST36). In this embodiment, since the threshold value for determining the systolic pressure SP is set to, for example, 0.5 A _MAX , as long as AMP (j)> 0.5 A _MAX , ST35.
And ST36 are repeated. And if AMP (j) ≦
If a pulse wave number j satisfying the relationship of 0.5A _MAX is found,
The cuff pressure PC (j) for the number j is adopted as the systolic pressure SP (ST37).

When the systolic pressure SP is determined, the diastolic pressure DP is determined. First, it is determined whether or not the value of AMP (n) has decreased below the threshold value for determining the diastolic pressure DP (ST38). In this embodiment, since the threshold value for determining the diastolic pressure DP is set to 0.7 A _MAX , AMP
If (n)> 0.7A _MAX , the process returns to the main routine without doing anything. However, if AMP (n) ≦ 0.7A _MAX , the cuff pressure PC (n) for the pulse number n at that time is adopted as the diastolic pressure DP. And returns to the main routine (ST39). still,
Blood pressure calculation process shown in FIG. 4 (ST14), as long as the variable DP for determining diastolic pressure is zero, (see ST15) because it is repeatedly processed after the maximum amplitude A _MAX is determined, the pulse wave Extraction process ST12 and pulse wave amplitude calculation process ST
13 by repeating the diastolic pressure DP (0.
7A _MAX ) can be determined.

[0023]

As described above, in the electronic sphygmomanometer according to the present invention, a predetermined condition is set near the start of the cuff pressure application.
Until the cuff pressure reaches a predetermined value or
Since the pressure starts until a predetermined time elapses without the extraction of the pulse wave, the influence of noise or body movement occurring at the start of operation of the sphygmomanometer further less susceptible, thus ensuring, systolic pressure
And an appropriate pressurization stop point can be automatically set.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an electronic sphygmomanometer according to one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the overall operation of the electronic sphygmomanometer of FIG. 1;

FIG. 3 is a flowchart illustrating a blood pressure estimation process of the electronic sphygmomanometer of FIG. 1;

FIG. 4 is a flowchart illustrating a blood pressure calculation process of the electronic sphygmomanometer of FIG. 1;

FIG. 5 is a diagram for explaining a blood pressure determination method in an oscillometric electronic sphygmomanometer.

[Explanation of symbols]

 1 Cuff 2 Pump 3 Rapid exhaust valve 4 Slow exhaust valve 5 Pressure sensor 8 MPU

Claims (2)

(57) [Claims] 1. A cuff for compressing a living artery, a pressurizing means for pressurizing the cuff, a pressure sensor for detecting a pressure in the cuff, and a cuff pressure signal detected by the pressure sensor superimposed on the cuff pressure signal. Pulse wave extraction means for extracting a pulse wave component
Condition determination to determine whether predetermined conditions have been satisfied after the start of pressurization
Means, and in response to satisfaction of the condition by the condition determining means,
Operation start control means for starting the operation of the pulse wave extraction means; and a pulse wave signal and a cuff pressure
A systolic pressure estimating means for estimating a systolic pressure had pressurized stopping means for stopping the operation of the pressurizing means reaches a predetermined cuff pressure determined based on the estimated systolic pressure of the systolic pressure estimating means And pressure reducing means for gradually reducing the cuff pressure after stopping the pressurization, and blood pressure determining means for extracting a pulse wave signal in the process of reducing the cuff pressure and determining the blood pressure based on the pulse signal and the cuff pressure. An electronic sphygmomanometer characterized by the above. (2) Add a cuff to compress the living artery and this cuff
Pressure means for applying pressure and a pressure sensor for detecting the pressure in the cuff
From the cuff pressure signal detected by this pressure sensor.
Pulse wave extraction means for extracting a pulse wave component superimposed on the pressure signal,
Cuff that detects that the cuff pressure exceeds a specified value after the start of pressurization
Pressure detection means, and that a predetermined time has elapsed since the start of pressurization.
Time elapse detecting means for detecting, the predetermined cuff pressure and the predetermined
In response to the detection of the passage of time, the operation of the pulse wave extracting means
Operation start control means to start the
To estimate systolic pressure based on pulse wave signal and cuff pressure
Systolic pressure estimating means and the yield estimated by the systolic pressure estimating means.
When a predetermined cuff pressure determined based on the systolic pressure is reached,
Pressure stop means for stopping the operation of the pressure means, and after the pressure stop
Pressure reducing means for gradually reducing the cuff pressure
Pulse wave signal is extracted in the process, based on the pulse signal and cuff pressure
And blood pressure determining means for determining blood pressure.
Electronic blood pressure monitor.