JPH0434808Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a pulse wave detection device, and particularly to a device that detects pulse waves generated from blood vessels with high accuracy.

PRIOR ART Pressure waves or vibrations of blood vessel walls that are generated as the heart beats and propagate within blood vessels are generally called pulse waves, and various medical information such as the state of cardiac motion can be obtained from these pulse waves. It is known that it can be obtained. As a device for detecting such pulse waves, a pressure sensor such as a piezoelectric element or a strain gauge that is pressed on the surface of the human body directly above the blood vessel is provided, and the pressure sensor detects the pulse wave generated by the blood vessel. Some devices are designed to detect pulse waves. The device described in Japanese Utility Model Application Publication No. 61-60901 is one example.

Problems to be Solved by the Invention However, in this type of pulse wave detection device, the pressure sensor is pressed against the surface of the human body with a predetermined constant pressing force by an elastic force such as a spring. Therefore, there was a problem that pulse waves could not always be detected with high accuracy. In other words, the pressing force of the pressure sensor is applied so that the blood vessel becomes approximately flat in order to eliminate the influence of tension on the blood vessel wall.In other words, a part of the blood vessel wall becomes flat and the pressing surface of the pressure sensor is It is desirable to set the pressure sensor so that the pressure sensor is approximately parallel to the current pressure sensor, but since this varies depending on the individual differences of the subject, conventional devices that press the pressure sensor with a constant pressure cannot detect a sufficient pulse wave. Detection accuracy cannot be obtained.

On the other hand, it is conceivable to adjust the pressing force based on the signal output from the pressure sensor, but conventionally, a pressure sensor having a contact surface of the same size or larger than the diameter of the blood vessel is generally used. Since the pulse wave was detected using the pulse wave, it is difficult to adjust the pressing force based on the signal so that the blood vessel becomes flat.

Means for Solving the Problems The present invention was developed against the background of the above-mentioned circumstances, and its purpose is to find an optimal pressure that will make blood vessels approximately flat regardless of individual differences among subjects. The purpose is to enable pulse waves to be detected with high accuracy at all times by pressing a pressure sensor with pressure.

In order to achieve such an object, the present invention provides a device for detecting pulse waves generated from blood vessels in the human body when pressed against the surface of the human body, which comprises: (b) a plurality of pressure sensors arranged in a direction intersecting blood vessels and outputting pulse wave signals corresponding to pulse waves generated from the blood vessels when pressed against the body surface; a pressing means for pressing the surface;
(c) The pressing force of the pressing means is determined by the signal strength of each pulse wave signal simultaneously output from a group of pressure sensors located directly above the blood vessel among the plurality of pressure sensors. The pressing force is adjusted to be high at both ends and low at the center.

Function and Effects of the Invention In other words, the present invention arranges a plurality of pressure sensors in a direction intersecting the blood vessel so that a group of pressure sensors is positioned directly above the blood vessel, and also increases the pressing force of the pressure sensors. With various changes,
We focused on the fact that when a blood vessel is approximately flat, the signal strength of the pulse wave signal output from a group of pressure sensors located directly above the blood vessel is high at both ends of the blood vessel and low at the center. The pressure adjustment means causes the signal strength of each pulse wave signal simultaneously output from a group of pressure sensors located directly above the blood vessel to be high at both ends of the blood vessel and high at the center. The pressing force of the pressing means that presses the pressure sensor against the body surface is adjusted so that the pressure becomes lower.

Therefore, according to the pulse wave detection device of the present invention, the pressure sensor is always pressed with the optimal pressing force that makes the blood vessel substantially flat regardless of individual differences among the subjects. This makes it possible to detect pulse waves with high accuracy without being affected by tension.

Note that the pulse wave detection device of the present invention adjusts the pressing force based on the signal strength of the pulse wave signal, that is, the pressure of the pulse wave, so it can be used without pressure vibration.
It can also be applied to detecting a venous pulse wave consisting only of DC components.

Further, the pressing force adjusting means may obtain, for example, a peak value of each of the pulse wave signals respectively output from the plurality of pressure sensors, and a change tendency of the peak value in a direction intersecting the blood vessel may be determined to have two maximum parts. and the pressing force is adjusted so that the peak value of the minimum portion existing between the maximum portions is equal to or less than a predetermined constant ratio with respect to the peak value of the maximum portion.

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

In FIG. 1, reference numeral 10 is a hollow body having an opening 12 at the lower end, and a band 16 is attached to the wrist with the opening 12 facing the body surface 14 of the human body.
It is designed to be removably attached to 8. The main body 10 consists of an annular side wall member 20 and a lid member 24 fixed to the upper end of the side wall member 20 with the outer peripheral edge of the diaphragm 22 interposed therebetween, and the inner peripheral edge of the diaphragm 22 is fixed to a pressing member 26. ing. The diaphragm 22 is made of an elastically deformable material such as rubber, and the pressing member 26 is held relatively movably within the main body 10 via the diaphragm 22. Further, a pressure chamber 28 is formed between the main body 10 and the pressing member 26 by the diaphragm 22, and pressure fluid such as pressurized air is supplied from a pressure fluid supply source 30 via a pressure regulating valve 32. By doing so, the pressing member 26 is pressed against the body surface 14. In this embodiment, the pressing means is constituted by the main body 10 forming a pressure chamber 28 at the rear of the pressing member 26, the diaphragm 22, and a pressure fluid supply source 30 such as a pump that supplies pressure fluid into the pressure chamber 28. There is.

The pressing member 26 includes an annular side wall member 36;
The diaphragm 22 is attached to the upper end of the side wall member 36.
It is composed of a lid member 38 fixed to sandwich the inner peripheral edge of the side wall member 36, and a press plate 40 disposed at the lower end of the side wall member 36. As shown in FIG. 2, the pressure plate 40 has a large number of pressure sensitive diodes 44 formed on the upper surface of a semiconductor chip 42 made of single crystal silicon, etc., and has electrical current corresponding to changes in pressure at the junction. Signals are adapted to be tapped between the common terminal 46 and the individual terminals 48. A large number of pressure-sensitive diodes 44 are formed at regular intervals in a direction that intersects the radial artery 50, whose pulse wave is to be detected, at a substantially right angle when the main body 10 is attached to the wrist 18. artery 50
The width dimension and the interval in the direction substantially perpendicular to the radial artery 50 are such that at least three (about seven in this embodiment) pressure sensitive diodes 44 are located directly above the radial artery 50, that is, directly above the radial artery 50. It is determined that the length is approximately the same as the diameter of the Note that the shape of the pressure sensitive diode 44 and the artery 50
The length dimension in the direction parallel to is set appropriately.

Furthermore, in the lower surface 52 of the press plate 40, in the portions corresponding to the pressure sensitive diodes 44, recesses are formed and rubber fillers 54 are embedded. The rubber filler 54 is filled in the recess so as not to apply a load to the pressure-sensitive diode 44 and to make the lower surface 52 flat, and the body surface 14 directly above the artery 50 and in the vicinity
is pressed flat by the lower surface 52 of the
Arterial pressure vibrations generated from the radial artery 50 are transmitted to the pressure sensitive diode 44 via the rubber filler 54. Semiconductor chip 4 in the part where the recess is formed
The wall thickness of the pressure sensitive diode 44 is extremely thin, for example, about 15 μm, and as pressure vibrations are transmitted to the rubber filler 54, pressure fluctuations occur at the joint of the pressure sensitive diode 44, and as a result, the pressure is released from the pressure sensitive diode 44. The electrical signal corresponding to fluctuations is the pulse wave signal SM
is output as In this embodiment, this pressure sensitive diode 44 corresponds to a pressure sensor.

The pressing plate 40 is fixed to the lower end opening of a container-shaped holding member 56 made of an insulating material, which is disposed inside the side wall member 36, and holds the semiconductor chip 42.
This is designed to prevent electrical leakage from the Further, a cavity 58 surrounded by the holding member 56 and the pressing plate 40 is open to the atmosphere via a rubber tube 60, and the pressure inside the cavity 58 fluctuates due to body temperature or the like. , the pulse wave signal SM output from the pressure sensitive diode 44 is prevented from changing.

The pulse wave signal SM output from the pressure-sensitive diode 44 is supplied to the control device 62 through an amplifier (not shown), a bandpass filter that extracts only the frequency component of the pulse wave, and the like. This control device 62 is composed of a microcomputer, etc., and detects the pulse wave of the artery 50 based on the supplied pulse wave signal SM, outputs a display signal SS to the display/recording device 64, and displays the pulse wave. is displayed and recorded, and a drive signal SD is output to the pressure regulating valve 32 to control the pressure value of the pressure fluid supplied into the pressure chamber 28. FIG. 3 is a flowchart showing an example of signal processing logic by the control device 62, and the operation of this embodiment will be explained below in accordance with this flowchart.

First, the pressing plate 40 of the pressing member 26 is pressed against the radial artery 5.
In a state where the main body 10 is attached to the wrist 18 by the band 16 so as to cover the right upper part of the wristband 0,
When the start switch (not shown) is operated, the step
When S1 is executed and the drive signal SD is output, pressure fluid at a predetermined constant pressure is supplied into the pressure chamber 28. As a result, the pressing member 26 is moved in the direction toward the body surface 14 relative to the main body 10, and the lower surface 52 of the pressing plate 40 is pressed against the body surface 14. When the lower surface 52 is pressed against the body surface 14 in this way, the pressure vibration of the pulse wave generated from the artery 50 is transmitted to the pressure sensitive diode 44.
The pulse wave signal corresponding to the pressure vibration is transmitted to
SM will now be output. The above-mentioned constant pressure is set to a level at which the pressure vibration of the pulse wave can be detected by the pressure sensitive diode 44.

Subsequently, step S2 is executed, and each pulse wave signal output simultaneously from a large number of pressure-sensitive diodes 44 arranged in a direction substantially perpendicular to the artery 50 is
The amplitude A of each SM is determined, and in step S3, the maximum amplitude maxA having the largest value among the determined amplitudes A is determined. Next, in step S4, a predetermined coefficient k ₁ (1>k>0) is applied to the maximum amplitude maxA.
A reference value A _s is calculated by multiplying , and in step S5, a pulse wave signal SM _(A) whose amplitude A is larger than the reference value A _s is selected. Then, in the following step S6, the maximum peak value P of the pulse wave signal SM _(A) selected in the step S5, that is, the pulse wave signal SM _(A) corresponding to the blood pressure value in the artery 50 during the cardiac systole. The signal intensities are respectively detected, and it is determined in the next step S7 whether the change tendency of the maximum peak value P in the direction intersecting the artery 50 has two local maxima.

Here, the steps S2 to S5 are performed using a pressure sensitive diode 44 located near the immediate upper part of the artery 50.
This is for selecting the pulse wave signal output from. That is, as shown in FIG. 4, the amplitude A of each pulse wave signal SM in the direction perpendicular to the artery 50 is larger directly above the artery 50 than in other parts, indicating that the artery 50 is approximately flat. When the pressing member 26 is pressed against the body surface 14 as shown in FIG. Pulse wave signal SM output from diode 44 is selected as signal SM _(A) . The coefficient k ₁ for calculating the reference value A _s is set such that the pulse wave signal SM output from the pressure-sensitive diode 44 located near the immediate upper part of the artery 50 is selected as the signal SM _(A). is set to .

And each pulse wave signal selected in this way
The graph of the maximum peak value P of SM _(A) in the direction intersecting the artery 50 is as shown in FIG. There is a tendency to have local maximum portions near the respective portions, and the determination in step S7 is YES.
This is because when the artery 50 is approximately flat, the wall of the artery 50 near the center directly above it is approximately parallel to the pressing member 40, so the pulse wave in the direction perpendicular to the wall of the artery is approximately parallel to the pressing member 40. The tension of the tube wall has almost no effect on pressure vibrations, whereas the pressure applied to the pressure-sensitive diode 44 near both ends of the artery 50 where the tube wall is curved is due to the tension of the tube wall. This is because the overall cost becomes high.

However, at this stage when the pressure value of the pressure fluid supplied into the pressure chamber 28 is relatively small, the pressing force for pressing the pressing member 26 against the body surface 14 is weak, so the artery 50 has not yet become flat. artery 50
The amplitude A of each pulse wave signal SM in the direction perpendicular to
As shown in FIG. 4(a), it only becomes relatively large near the center of the upper part. Therefore, in step S5, one to several pulse wave signals SM near the center are selected as the signal SM _(A) . Furthermore, the graph of the maximum peak value P of the pulse wave signal SM _(A) selected in this way is shown in FIG. 5(a), where the artery 50 has not yet become flat. There is only one local maximum near the center. Therefore, the steps
The determination at S7 is NO, and step S8 is then executed.

In step S8, the drive signal SD is output to the pressure regulating valve 32, so that the pressure chamber 28
The pressure value of the pressure fluid supplied within is increased by a predetermined constant pressure. Thereafter, steps S2 and subsequent steps are repeated, and the reference value A _s is determined based on the pulse wave signals SM newly output from the multiple pressure _- sensitive diodes 44, and the pulse wave signal SM _{( A)} is selected, and it is determined whether the graph of its maximum peak value P has two local maxima. In step S8, the pressure chamber 28
As the pressure value of the pressure fluid supplied into the body is increased, the pressing force for pressing the pressing member 26 against the body surface 14 is also increased.
By repeating S8, the artery 50 is gradually deformed, and the graph of the amplitude A of each pulse wave signal SM changes as shown in (b) in FIG. 4. Further, the graph of the maximum peak value P of the pulse wave signal SM _(A) selected in step S5 also changes as shown in (b) in FIG. When the graph of the maximum peak value P has two maximum parts as shown in FIG. 5(c), the determination in step S7 becomes YES, and step S9 is then executed.

In step S9, the maximum value maxP and the minimum value minP are detected. The local maximum value maxP is the above 2
The average value of the maximum peak values P in the two local maximum parts,
The minimum value minP is the maximum peak value P of the minimum part that exists between those two maximum parts, and is the maximum peak value P of the minimum part between those two maximum parts.
In S10, the minimum value minP is the maximum value
It is determined whether the value is smaller than the value obtained by multiplying maxP by a predetermined coefficient k ₂ (1>k>0). That is, it is determined whether the large peak value minP of the local minimum values existing between the local maximum portions is less than a predetermined ratio with respect to the peak value maxP of the local maximum portion. This means that only the pressure vibration of the pulse wave within the artery 50 is applied to the pressure sensitive diode 44 located near the center directly above the artery 50, and the influence of the tension of the wall of the artery 50 is almost eliminated. This is for determining whether the artery 50 is flat or not, and the coefficient k ₂ is set economically in consideration of the elastic force of the artery 50 and the like. The steps S8 and S2 are repeated until the determination in step S10 becomes YES, and the pressure value of the pressure fluid supplied into the pressure chamber 28 is increased. In this embodiment, the control device 62
The part that executes the above steps S6, S7, S8, S9 and S10 of the series of signal processing logic by
The pressure regulating valve 32 controlled thereby corresponds to a pressing force regulating means.

If the determination in step S10 is YES, then step S11 is executed, and the pulse wave signal SM _(A) having the minimum value minP is selected as the pulse wave signal SM _(P) . Once the pulse wave signal SM _(P) is selected in this way, this pulse wave signal SM _(P) is read in continuously from now on, and the display signal is
By outputting SS, the pulse wave signal SM _(P)
The pulse wave represented by is displayed and recorded on the display/recording device 64. The pulse wave is displayed and recorded based on the extremely small pulse wave signal SM _(P) .
This is because the pulse wave represented by SM _(P) is hardly affected by the tension of the wall of the artery 50, as described above, and is extremely similar in absolute value to the actual pulse wave (pressure wave) inside the artery 50. be.

In this case, if the positional relationship between the pressing member 26 and the artery 50 changes due to the subject's body movement, a correct pulse wave may not be obtained depending on the pulse wave signal SM _(P) selected above. Therefore, each step is executed every time a certain period of time or a certain number of pulse waves are detected to monitor whether there is any change in the pulse wave signal SM _(P) , or to detect the pulse wave. It is desirable to change the pulse wave signal SM _(P) for this purpose.
Note that it is also possible to automatically diagnose the cardiac activity state etc. based on the detected pulse wave, or to determine the systolic blood pressure value and diastolic blood pressure value from the maximum peak value P and minimum peak value P' of the pulse wave.

As described above, the pulse wave detection device of this embodiment is such that the maximum peak value P of each pulse wave signal SM output simultaneously from the group of pressure-sensitive diodes 44 located near directly above the artery 50 is directly Since the pressing force for pressing the pressure sensitive diode 44 against the body surface 14 is adjusted so that it is high at both ends of the upper part and low at the central part, in other words, so that the artery 50 is approximately flat,
The pressure-sensitive diode 44 is always pressed against the body surface 14 with an optimal pressing force regardless of individual differences among subjects, and the accuracy of pulse wave detection is improved.

In particular, in this embodiment, among the pulse wave signals SM _(A) output from the pressure-sensitive diode 44 located near the immediate upper part of the artery 50, the pulse wave signal SM _(P) whose maximum peak value P is the minimum is selected. Since the pulse wave is detected based on the pulse wave, there is an advantage that the absolute pressure value of the pulse wave can be very similar to the actual pulse wave inside the artery 50.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, the pressing force adjusting means of the embodiment is adapted to control the pressing force so that the maximum peak value P as the signal intensity of the pulse wave signal SM has two maximum parts in the direction intersecting the artery 50. but,
Instead of the maximum peak value P, it is also possible to use the minimum peak value P' or a signal level obtained by smoothing the vibration component.

Further, in the above embodiment, based on the amplitude A, the pressure sensitive diode 4 is placed in advance in the vicinity of right above the artery 50.
The pulse wave signal SM _(A) output from 4 is selected, but the maximum peak value P of the pulse wave signal SM
is higher near the area directly above the artery 50 than in other parts, so it is also possible to adjust the pressing force based only on the magnitude of the maximum peak value P without considering the amplitude A. Note that when detecting a venous pulse wave without pressure vibration, the pressing force is adjusted based on the average signal level of the pulse wave signal SM, etc.

Further, in the embodiment described above, pressure fluid is supplied into the pressure chamber 28 to press the pressing member 26 equipped with the pressure-sensitive diode 44 against the body surface 14, but a cylinder, an electromagnetic actuator, etc. may be used. It is also possible to use a spring.
When using a spring, the pressing force can be adjusted by changing the position of the spring receiver.

Further, although the pressure sensitive diode 44 is used as the pressure sensor in the above embodiment, various well-known means such as a semiconductor strain gauge or a pressure sensitive transistor may be used. Furthermore, it is also possible to configure one pressure sensor with two or four pressure-sensitive diodes and output a pulse wave signal using a bridge circuit or the like.

Further, in the above embodiment, a large number of pressure sensitive diodes 4
For example, if the pressing member 26 can be forcibly moved in a direction intersecting the artery 50 by an actuator, a relatively small number, for example, a number positioned near the right upper part of the artery 50, may be used. There is no problem even if only one pressure-sensitive diode 44 is provided.

Further, the pressure-sensitive diodes 44 are arranged in one row on the semiconductor chip 42, but if two rows are provided, shifted by 1/2 pitch, it is possible to increase the width and spacing of the pressure-sensitive diodes 44. On the other hand, if the intervals are kept the same, the resolution will double, making it possible to detect even finer pulse waves. Further, according to the same idea, it is also possible to provide three or more rows of pressure sensitive diodes 44.

Furthermore, in the embodiment described above, the pressure sensitive diodes 44 are arranged in a direction that intersects the artery 50 at a substantially right angle, but they can also be arranged in a direction that intersects the artery 50 obliquely. In that case as well, the spacing between the pressure-sensitive diodes 44 in the direction perpendicular to the artery 50 becomes narrower, so that the same effect as in the case where two or more rows of pressure-sensitive diodes 44 are provided as described above can be obtained.

Further, in the embodiment described above, the pressing force is adjusted by software using a microcomputer, but it is also possible to adjust the pressing force by using a hard logic circuit that performs the same function.

Further, in the above embodiment, a pulse wave detection device for detecting pulse waves from the radial artery 50 has been described, but the present invention can be similarly applied to detecting pulse waves from other arteries such as the carotid artery or veins. .

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the main parts of a pulse wave detection device which is an embodiment of the present invention. FIG. 2 is a partially cutaway perspective view for explaining a plurality of pressure sensors provided in the apparatus of FIG. 1. FIG. 3 is a flowchart illustrating an example of the operation of the apparatus shown in FIG. FIG. 4 is a graph showing the amplitude of the pulse wave signal output from each pressure sensor in the direction perpendicular to the artery, comparing three cases with different pressing forces. FIG. 5 is a graph showing the maximum peak value of the pulse wave signal output from each pressure sensor in the direction perpendicular to the artery, and shows a comparison of three cases with different pressing forces. 10... Body, 14... Body surface, 22... Diaphragm, 30... Pressure fluid supply source, 32... Pressure regulating valve, 44... Pressure sensitive diode (pressure sensor),
50... radial artery (blood vessel), 62... control device,
Steps S6 to S10...pressing force adjustment means.

Claims (1)

[Utility Model Registration Claims] (1) A device for detecting pulse waves generated from blood vessels within a human body when pressed against the body surface of the human body, comprising: a plurality of pressure sensors arranged on the body surface of the human body in a direction intersecting the blood vessels, each of which outputs a pulse wave signal corresponding to a pulse wave generated from the blood vessels when pressed against the body surface; pressing means for pressing the pressure sensors against the body surface; and pressing force adjustment means for adjusting the pressing force by the pressing means so that the signal strength of each pulse wave signal output simultaneously from a group of pressure sensors among the plurality of pressure sensors located immediately above the blood vessel is high at both ends of the immediately above the blood vessel and low in a central portion. (2) The pulse wave detection device described in claim 1 of the utility model registration, wherein the pressure adjustment means determines the peak values of each of the pulse wave signals output simultaneously from the multiple pressure sensors, and adjusts the pressure so that the trend of change in the peak value in a direction intersecting the blood vessel has two maximum parts and the peak value of the minimum part existing between the maximum parts is equal to or less than a predetermined constant percentage of the peak value of the maximum part.