JPH0131368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention detects arteries under the skin of a living body based on pulse wave signals output from a plurality of sensors arranged on the front surface of a housing that is pressed against the skin of the living body. This invention relates to a device that accurately detects waves.

BACKGROUND OF THE INVENTION Important medical information can be obtained from the waves of an artery under the skin of a living body, such as the carotid artery, so it is desired to accurately display the waves of the carotid artery, that is, the pulse wave. On the other hand, it includes a common housing that is pressed against the skin of the living body and a plurality of sensors arranged at predetermined intervals on the pressing surface of the housing,
A pulse wave detection device has been proposed that detects a pulse wave in an artery under the skin based on pulse wave signals output from each of the sensors. According to this type of device, since a plurality of sensors are arranged at predetermined intervals on the pressing surface of the housing, one of the sensors can be easily positioned directly above or near the artery, even though the area in which the artery touches is narrow. There is an advantage that it can be done.

Problems to be Solved by the Invention Incidentally, in the conventional pulse wave detection device described above, the housing is pressed against the skin of the living body using a mounting tool, or the housing is held by an operator and pressed against the skin of the living body. However, if there is variation in the pressing force when pressing the housing against the skin, there is a drawback that the pulse wave signal output from the sensor varies. That is, especially when the worker holds the housing, the pressing force of the housing against the skin tends to fluctuate, so the pressing force of the sensor also fluctuates, and this fluctuation can be mixed into the pulse wave signal output from the sensor. This noise makes it impossible to obtain accurate medical information.

The present invention has been made against the background of the above circumstances, and its object is to provide a pulse wave detection device that can output an accurate pulse wave that does not contain noise.

Means for Solving the Problems The gist of the present invention for achieving the object is to provide a common housing that is pressed against the skin of a living body, and a plurality of housings that are arranged at predetermined intervals on the pressing surface of the housing. A pulse wave detection device comprising a sensor and detecting a pulse wave in an artery under the skin based on pulse wave signals output from each sensor, the device comprising: (a)
(b) variable amplification means connected to each of the sensors and amplifying the pulse wave signal output from the sensor at a negative or positive amplification factor; and (b) each amplified pulse wave signal output from the variable amplification means. (c) maximum pulse wave determining means that compares each pulse wave signal output from the sensor and determines the largest maximum pulse wave signal; and (d) applying to the variable amplification means a series of amplification factor values in which the central value is positive, the other values on both sides are negative, and the average value as a whole is zero; Control to amplify the maximum pulse wave signal by a central value of the amplification factor value sequence, and amplify the pulse wave signals on both sides of the maximum pulse wave signal by values on both sides of the central value of the amplification factor value sequence. means.

Operation and Effects of the Invention By doing this, in the variable amplification means, a series of amplification factor values in which the central value is positive, the other values on both sides thereof are negative, and the average value as a whole is zero. is applied, the maximum pulse wave signal is amplified by the central value of the amplification factor value sequence, and the maximum pulse wave signal on both sides of the amplification factor value sequence is amplified by the values on both sides of the central value of the amplification factor value sequence. Since the pulse wave signal is amplified, in effect, each pulse wave signal output from each sensor has a central value that is positive, other values on both sides of it are negative, and an average value as a whole. A series of weight values that are zero are assigned. When an artery under the skin is pressed by each sensor arranged in a common housing, the sensor located directly above the artery outputs the maximum pulse wave signal, while the sensor located further away from the artery outputs a smaller pulse wave signal. But,
Since the pressing force of each sensor changes in accordance with the variation in the pressing force of the housing, an influence related to the change appears on each of the pulse wave signals. At this time, as mentioned above, if we take the average value of each pulse wave to which the above series of weighting values, each of which has an average value of zero, are given, it is possible to calculate the difference due to fluctuations in the pressing force of the housing against the skin or movement of the measurement site. By using the average pulse wave signal as the pulse wave, the noise included in each pulse wave is canceled out, and at the same time, the difference between the positive weighted maximum pulse wave signal and other signals is emphasized. Pulse waves can be obtained. Therefore,
The pulse waves generated from the arteries can be accurately detected, and accurate medical information can be derived based on the pulse waves.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

1 to 3, seven sensors 14a to 14g are arranged in a line along the longitudinal direction on the pressing surface 12 of the elongated housing 10. As shown in FIGS. That is, notches 16 in the width direction are formed in the housing 10, and stepped grooves 18 in the longitudinal direction of the housing 10 are formed between the notches 16. 1
0, the sensors 14a to 14g are installed in exactly the same way. For example, sensor 1
As shown in FIG. 3, the flexible elastic membrane 22g has a protrusion 20 in the center and is fixed to the housing 10 at both ends, and the flexible elastic membrane 22g has both ends in contact with the center of the flexible elastic membrane 22g. An elastic plate piece 28g supported by a support frame 24g and having a strain gauge 26g attached to the back side and a support frame 24g are placed in a groove 1.
30g of elastic supports elastically supported within 8
It consists of Therefore, in the sensor 14g, the support frame 24g is supported by the elastic support 30g, so that regardless of the variation in the pressing force of the housing 10 against the skin surface, the pressure of the protrusion 20g changes relatively gently. There is an advantage that

As shown in FIG. 2, both ends of the housing 10 are fixed to a holder 32, and the center portion of the housing 10 is bendable when the housing 10 is pressed against, for example, the neck of a human body. That is, the housing 10 is made of a resin that is relatively soft compared to the holder 32, and can be easily bent by the notches 16 formed in the thickness direction. Note that 34 is a multicore cord connected to the holder, and is connected to the strain gauges 26a to 26g of the sensors 14a to 14g.

Each of the sensors 14a to 14g of the pulse wave detection device configured as described above is connected to a circuit shown in FIG. 4. In FIG. 4, the pulse wave signals output from each sensor 14a to 14g are supplied to variable sensitivity amplifiers 38a to 38g and an averaging circuit 40 via preamplifiers 36a to 36g, respectively, and to each input port Pa of a multiplexer 42.
Bandpass filters 44a to 44g from Pg to Pg
Supplied via.

The variable sensitivity amplifiers 38a to 38g receive an amplification factor signal SSa from a sensitivity setting interface 46, which will be described later.
The input pulse wave signals SMa to SMg are amplified at the amplification factors indicated by SSg to SSg, and are supplied to the averaging circuit 48. The averaging circuit 48 averages the input amplified pulse wave signals SMa to SMg, and outputs the average pulse wave signal SMA to the input port of the multiplexer 42.
Supply to Pm.

On the other hand, the averaging circuit 40 is for detecting pressure fluctuations, and is for detecting the input pulse wave signal.
Average SMa to SMg and use low pass filter 5
Supply to 0. The low-pass filter 50 removes signal components (wave components) from the input signal and supplies a drift signal SD representing only a static drift component to the input port Pd of the multiplexer 42 .

The multiplexer 42 receives a select signal SL supplied from a port selection interface 52, which will be described later.
Accordingly, the input port is selectively selected, and the signal supplied to the selected input port is supplied to the oscilloscope 54 and to the I/O port 58 via the A/D converter 56. .
The I/O port 58 is connected via a data path line.
It is connected to the CPU 60, RAM 62, and ROM 64. The CPU 60 executes signal processing using the storage function of the RAM 62 according to a program stored in advance in the ROM 64, and supplies a sensitivity command signal SO and a port command signal SP to the sensitivity setting interface 46 and port selection interface 52. At the same time, a display signal SH is supplied to the printer drive circuit 66. The printer drive circuit 66 outputs a display signal
A drive signal SHD is supplied to the printer 68 so that the printer 68 displays the wave represented by SH.

Note that the pressing force display signal PP is supplied from the I/O port 58 to the pressing force display 70, where a lighting display is performed to indicate whether or not the pressing force of the sensors 14a to 14g is appropriate. There is.

The operation of this embodiment will be explained below based on the flowchart of FIG.

First, the pulse wave detection device described above uses its sensor 14.
For example, when sensors a to 14g are pressed against the neck of a human body so as to intersect with the carotid artery of the human body, the sensor closer to the carotid artery outputs a larger pulse wave signal. In such a state, step S1 is executed first, and the CPU
60 is the pulse wave signal SMa via the I/O port 58
A port command signal SP is supplied to the port selection interface 52 so that SMg to SMg are sequentially supplied to the I/O port 58. Therefore, the port selection interface 52 supplies the select signal SL to the multiplexer 42 so that the input ports Pa to Pg are sequentially selected, so that the pulse wave signals SMa to
SMg is sequentially supplied to I/O port 58. Next, step S2 is executed, and the largest maximum pulse wave signal among the pulse wave signals SMa to SMg is determined. Then, step S3 is executed, the amplification sensitivity centered on the maximum pulse wave signal is determined, and the sensitivity command signal SO is sent to the sensitivity setting interface so that each of the pulse wave signals SMa to SMg is amplified at that sensitivity. 46. Therefore, the sensitivity setting interface 46 supplies amplification factor signals SSa to SSg representing the respective sensitivities to the variable sensitivity amplifiers 38a to 38g. For example, if the maximum pulse wave signal is
In the case of SMd, each pulse wave signal is
SMa to SMg are amplified and supplied to an averaging circuit 48. That is, the vertical axis of FIG. 6 shows the value of the amplification factor, and the horizontal axis shows the name of the pulse wave signal to which the amplification factor is applied, and each value in the series of amplification factor values shown therein is The overall average value is zero, but the central value is positive and the other values on both sides are negative. Therefore, the amplification factor of the variable sensitivity amplifier 38d is set to a positive amplification factor, and the other variable sensitivity amplifiers 38a to 38c and 38e to 3
The amplification factor of the 8g amplifier is negative, and the amplification factor becomes closer to zero as it goes from SMa to SMc and from SMg to SMe. In other words, if the average value is zero and the pulse wave signal SMd has a positive weight,
Negative weights are given to the other pulse wave signals SMa to SMc and SMe to SMg.

In addition, in the above explanation, the case where the maximum pulse wave signal is determined to be the pulse wave signal SMd in step S2 is explained, but the housing 1
Depending on the relative position between the pulse wave signal 0 and the artery, the maximum pulse wave signal shifts toward the pulse wave signal SMc side or toward the pulse wave signal SMe side. For example, when it is determined that the maximum pulse wave signal is the pulse wave signal SMc, a series of amplification factor values as shown in FIG. 6 is used in step S3. The pulse wave signal SMc is amplified by the positive amplification factor, and the other pulse wave signals on both sides of the pulse wave signal SMc are amplified by the negative amplification factors on both sides of the positive amplification factor.

Next, step S4 is executed and input port Pm of multiplexer 42 is selected. For this reason,
Pulse wave signals SMa to amplified by the averaging circuit 48
The average pulse wave signal SMA obtained by averaging the SMg is supplied to the oscilloscope 54 and the I/O port 58. This average pulse wave signal SMA is determined by the above-mentioned weighting and subsequent averaging.
Noise contained in SMg to SMg is suitably removed. Therefore, even if the neck of the human body moves rapidly or the pressing force applied to the housing 10 fluctuates, and the compression pressure of the sensors 14a to 14g changes uniformly, accurate carotid artery waves can be obtained. is displayed on the oscillograph 54 in real time.

Furthermore, step S5 is executed to read the average pulse wave signal SMA for a certain period of time, for example, 10 seconds, and step S6 is executed to check whether the read average pulse wave signal SMA is abnormal, that is, the average pulse wave signal SMA. It is determined whether the amplitude exceeds a predetermined constant value. If the average pulse wave signal SMA is abnormal, step S5 and subsequent steps are executed again, but if it is not abnormal, step S7 is executed, and the amplitude of the read average pulse wave signal SMA is displayed on the chart (recording paper). width aligned and displayed on printer 48. In other words, a constant value for the entire width of the recording paper,
Average pulse wave signal so that an amplitude of 80% is obtained, for example.
When the SMA is rewritten, a display signal is displayed to represent the rewritten average pulse wave signal SMA.
By supplying SH to the printer drive circuit 66 and supplying the drive signal SHD from the printer drive circuit 66 to the printer 68, the printer 68
Accurate carotid artery waves are displayed on the recording paper at easy-to-read amplitudes.

In addition, the average circuit 40 and the low-pass filter 50
The drift components of the pulse wave signals SMa to SMg after passing through are
It is determined whether or not the pressure value is within a predetermined appropriate pressure value range according to a flowchart not shown, and a lighting display is made on the pressure force display 70 to indicate whether the pressure value is within the range or outside the range.

According to this embodiment, in the variable sensitivity amplifier circuits 38a to 38g, for example, as shown in FIG. 6, the central value is positive, and the other values on both sides thereof are negative, and the overall average By applying a series of amplification factor values having a value of zero, the maximum pulse wave signal is amplified by the central value of the amplification factor value sequence, and the values on both sides of the central value of the amplification factor value sequence are amplified. Since the pulse wave signals on both sides of the maximum pulse wave signal are amplified depending on the value, each pulse wave signal SMa to SMa output from each sensor 14a to 14g is substantially amplified.
SMg is given a series of weight values where the central value is positive, the other values on either side are negative, and the overall average value is zero. When an artery under the skin is pressed by each sensor arranged in the common housing 10, the sensor located directly above the artery outputs the maximum pulse wave signal, while the sensor located further from the artery outputs a smaller pulse wave signal. However, since the pressing force of each sensor changes depending on the variation in the pressing force of the housing 10, the pulse wave signals SMa to SMg are affected by the changes. At this time, as mentioned above, if we take the average value of each pulse wave to which the above series of weighting values, each of which has an average value of zero, are given, it is possible to calculate the difference due to fluctuations in the pressing force of the housing against the skin or movement of the measurement site. By using the average pulse wave signal as the pulse wave, the noise included in each pulse wave is canceled out, and at the same time, the difference between the positive weighted maximum pulse wave signal and other signals is emphasized. Pulse wave can be obtained. Therefore, the pulse waves generated from the arteries can be accurately detected, and accurate medical information can be derived based on the pulse waves.

Furthermore, the negative weight assigned in step S3 becomes a value closer to zero as the sensor that outputs the pulse wave signal to which it is assigned is disposed closer to the sensor that outputs the maximum signal. Therefore, the carotid artery wave can be displayed more accurately and easily. In other words, the closer the sensor is to the carotid artery, the less distortion the carotid artery wave can be obtained.
It is desirable that a pulse wave signal output from a sensor close to the carotid artery be used to display wave motion in the carotid artery.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other aspects.

For example, in the above embodiment, the oscillograph 54 displays carotid artery waves in real time,
Although the printer 68 is configured to display the carotid artery wave after checking whether or not the average pulse wave signal SMA is abnormal, if either the oscillograph 54 or the printer 68 is provided, It's good.

Further, in the above embodiment, the negative weight given to pulse wave signals other than the maximum pulse wave signal may be a constant value.

Further, although the sensors 14a to 14g of the carotid artery wave detection device shown in FIGS. 1 to 3 are arranged in a straight line that intersects the carotid artery, they may be arranged in a plane. .

In addition, in the carotid artery wave detection device, the elastic support 3
0g may be excluded and the support frame 24g may be directly fixed to the housing 10.

Furthermore, the pressing force indicator 70 may be provided on the housing 10 or the holder 32. In such a case, there is an advantage that the person pressing the pulse wave detection device can easily understand whether the pressing force is appropriate or not.

The above-mentioned embodiment is merely one embodiment of the present invention, and the present invention can be modified in various ways without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway plan view of a carotid artery wave detection device to which an example of the present invention is applied. 2 and 3 are a partially cutaway side view and a sectional view, respectively, of the device shown in FIG. 1. FIG. 4 is a circuit diagram showing an example of the present invention connected to the device of FIG. 1. FIG. 5 is a flowchart illustrating the operation of the embodiment shown in FIG. FIG. 6 is a diagram showing an example of the amplification factor for each pulse wave signal. 10: Housing, 12: Pressing surface, 14a~
g: sensor, 38a to g: variable sensitivity amplification circuit (variable amplification means), 46: sensitivity setting interface (control means), 60: CPU (control means), 62:
RAM (control means), 64: ROM (control means), 4
8: averaging circuit (pulse wave averaging means), 54: oscillograph (display device), 68: printer (display device),
S2: Step of determining the maximum pulse wave signal, S3: Weighting step, S4: Average step, S7: Display step,
SMa~g: Pulse wave signal, SMA: Average pulse wave signal.

Claims (1)

[Claims] 1. A common housing that is pressed against the skin of a living body, and a plurality of sensors arranged at predetermined intervals on the pressing surface of the housing, and based on pulse wave signals output from the respective sensors. A pulse wave detection device that detects the pulse wave of the artery under the skin, the variable device being connected to each of the sensors and amplifying the pulse wave signal output from the sensor at a negative or positive amplification factor. an amplifying means; a pulse wave averaging means that averages each amplified pulse wave signal outputted from the variable amplifying means and outputs an average pulse wave signal; and a pulse wave averaging means that compares each pulse wave signal outputted from the sensor. Maximum pulse wave determining means for determining the largest maximum pulse wave signal, and said variable amplifying means having a central value positive, other values on both sides thereof being negative, and an overall average value of zero. Applying a series of amplification factor values, the maximum pulse wave signal is amplified by the central value of the amplification factor value sequence, and the maximum pulse wave signal is amplified by the values on either side of the central value of the amplification factor value sequence. A pulse wave detection device comprising: a control means for amplifying pulse wave signals on both sides of the pulse wave signal;