JP2798698B2 - Blood pressure monitoring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood pressure monitor, and more particularly to a technique for determining a blood pressure value with high accuracy.

2. Description of the Related Art A pressure pulse wave generated from an artery of a living body is detected by pressing a pressure detecting element positioned just above an artery of the living body against the skin of the living body with a prescribed pressure, and the magnitude of the pressure pulse wave is detected. 2. Description of the Related Art A blood pressure measurement device that determines a blood pressure value of a living body is known. For example, a continuous blood pressure measuring device described in Japanese Patent Application Laid-Open No. 63-293424 is that. In the above blood pressure measurement device, when a part of the flexible blood vessel wall is pushed in so as to be flat, the elastic force or tension of the blood vessel wall does not act on the flat part in a direction perpendicular to the wall. Based on the principle that the pressure outside the portion and the pressure inside the portion are equal, the blood pressure value is configured to be determined based on the magnitude of the output signal from the pressure sensing element corresponding to the center position of the flat portion. I have. However, in actual blood pressure measurement, since the pressure detecting element is pressed toward the blood vessel from above the skin, the pressure in the blood vessel and the pressure detecting element are determined by the skin and subcutaneous tissue interposed between the pressure detecting element and the blood vessel wall. Often occurs between the pressure and the pressure detected.

Problems to be Solved by the Invention In contrast, prior to blood pressure measurement, a blood pressure value is measured in advance using a cuff, and at the same time, an actual pressure pulse wave is obtained by a pressure detecting element. A blood pressure measurement device of a type that determines a relationship with the magnitude of the blood pressure and then determines a blood pressure value based on the actual pressure pulse wave from the relationship. However, in such a case, it is necessary to use a cuff, so that the device is large and the handling is complicated.On the other hand, since the error of the blood pressure measurement method using the cuff is inherited as it is, the accuracy of the measurement method is reduced. The inconvenience that blood pressure measurement cannot be performed with higher accuracy than that occurs.

The present inventor has made various investigations with the above circumstances as a background and to provide a blood pressure measurement device capable of determining a relationship for determining blood pressure without using a cuff. The difference between the pressure in the blood vessel caused by the skin and the subcutaneous tissue of the subject interposed between the pressure and the pressure detected by the pressure detecting element is caused by the elastic properties of the skin and the subcutaneous tissue of the subject. I found the facts that were mainly affected. The present invention has been made based on the findings.

Means for Solving the Problems That is, the gist of the present invention is to have a pressing surface on which a number of pressure-sensitive elements are arranged, so that the arrangement direction of the pressure-sensitive elements intersects the artery on the pulsation of a living body. And a pressure sensor output from a pressure-sensitive element located immediately above the artery among the pressure-sensitive elements by pressing the pressure sensor against the skin of a living body at a predetermined pressure. A blood pressure monitor device of a type in which a pressure pulse wave generated from an artery is detected based on a wave signal, and a blood pressure value of a living body is determined based on a magnitude of an actual pressure pulse wave from a relationship obtained in advance.
(A) surface pressure detecting means for detecting a surface pressure received from the skin by a pressure-sensitive element located at a predetermined distance from a pressure-sensitive element located immediately above the artery on a pressing surface of the pressure sensor; b) a relation correcting means for correcting the relation based on the surface pressure detected by the surface pressure detecting means.

In this way, the surface pressure generated in response to the elastic force of the skin and subcutaneous tissue of the subject is separated from the pressure-sensitive element located immediately above the artery by the predetermined distance in the surface pressure detecting means. Since the relation is corrected by the pressure-sensitive element located at the place and the relation correction means corrects the relation based on the surface pressure,
The relationship for determining blood pressure is accurately obtained. That is, by determining the blood pressure value based on the actual pressure pulse wave from the corrected relationship, the blood pressure value accurately corresponding to the pressure in the blood vessel can be measured without using a cuff. Therefore, since the blood pressure is determined without using a cuff, the structure and handling of the device are simplified, and the blood pressure can be measured with high accuracy exceeding the accuracy of the blood pressure measurement method using the cuff.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the blood pressure monitoring device of the present embodiment. In the figure, an electric pump 10 is connected to a pipe 12
Are connected to the pressing force control valve 14 and the position control valve 16 via the control valve. To the pulse wave detector 18, a control pressure for controlling the pressing force is supplied from the pressing force control valve 14, and
The control pressure for controlling the pressing position is the position control valve.
It is supplied from 16. Above pressure control valve
A conduit between the pulse wave detector 18 and the pulse wave detector 18
A pressure sensor 20 for detecting a control pressure for controlling the pressing force of the pressure sensor 20 is provided, and a pressure signal SP output from the pressure sensor 20 is supplied to the CPU 24 via the A / D converter 22. . Also, the pressure pulse wave signal output from the pulse wave detector 18
The SM is supplied to the CPU 26 via the A / D converter 24.

The CPU 26 is connected to the RAM 2 connected via a data bus line.
A microcomputer which functions as a control device of the present embodiment together with the ROM 8, the ROM 30, and the output interface 32 is configured. The CPU 26 executes signal processing using the storage function of the RAM 28 according to a program stored in the ROM 30 in advance, and controls the electric pump 10 via drive circuits (not shown), respectively, while the pressing force control valve 14 and the position control valve 16 to control the pressing position and the pressing force of the pulse wave detecting device 18 appropriately, and the pulse wave signal obtained from the pulse wave detecting device 18.
The systolic blood pressure value and the diastolic blood pressure value are sequentially determined based on the SM, and the blood pressure values are continuously displayed on the blood pressure display.

The pulse wave detector 18 is configured to arrive at a wrist 36 of a living body as shown in FIGS. 2 and 3, for example. That is, the pulse wave detector 18 includes a housing 38 having a bottomed cylindrical shape, and the open end of the housing 38 can be attached to and detached from the wrist 36 by the band 42 with the open end facing the body surface of the wrist 36, that is, the skin 40. It can be attached to. Inside the housing 38, a pulse wave sensor 46 is provided via a diaphragm 44 so as to be relatively movable and protrudable from the open end of the housing 38. The pressure chamber 48 is formed by the housing 38 and the diaphragm 44.
Are formed. The pressure chamber 48 is supplied with a pressure fluid from the electric pump 10 via the pressing force control valve 14, so that the pulse wave sensor 46
The skin 40 is pressed with a pressing force corresponding to the internal pressure P. The pressure sensor 20 detects the pressure P in the pressure chamber 48 and outputs a pressure signal SP representing the pressure P to the CPU 24 via the A / D converter 22.

An inner wall near the open end of the housing 38 and a band
At a position corresponding to each of the two mounting portions 42, a pair of arc-shaped rubber bags 50 and 52 are fixed so as to be sandwiched between the pulse bags and the pulse wave sensor 46, respectively.
A pressure fluid is supplied from the electric pump 10 through the position control valve 16 to the inside of the housing 52. The position control valve 16 controls the pulse wave sensor 46 in a direction substantially orthogonal to the radial artery 54 by controlling the difference in thrust in the radial direction between the rubber bags 50 and 52.

The pulse wave sensor 46 includes a semiconductor chip 56 such as single crystal silicon.
A plurality of pressure-sensitive elements 60 such as semiconductor strain gauges and pressure-sensitive diodes are alternately arranged in two rows on a pressing surface 58 of the radial artery.
By being pressed against the skin 40 of the wrist 36 so as to be substantially orthogonal to 54, the pressure vibration wave, that is, the pressure pulse wave transmitted from the radial artery 54 to the body surface in synchronization with the pulse is detected at each pressure-sensitive element 60. Then, a pulse wave signal SM representing the pressure pulse wave is output to the CPU 26 via the A / D converter 24. The arrangement range R of the pressure-sensitive elements 60, that is, the interval between the pressure-sensitive elements 60 located at both ends in the arrangement direction is set to be larger than the maximum outer diameter when the radial artery 54 is pressed.

Next, the operation of the blood pressure monitor configured as described above will be described with reference to the flowchart of FIG.

First, after the pulse wave detector 33 is attached to the wrist 32, when a power switch (not shown) is turned on, in a step (not shown), initial processing is executed to clear a timer counter, a flag, and the like. It is determined whether the manual start switch has been turned ON. If this judgment is affirmed, the routine of FIG. 4 is executed. First, in step S1, a position control routine for positioning the pulse wave sensor 46 is executed. That is, while the pump 10 is driven, the pressing force control valve 14
As a result, the pressure in the pressure chamber 48 starts to be relatively gradual, and when the pulse wave sensor 42 starts pressing the skin surface 40, the pressure P in the pressure chamber 48 becomes a predetermined pressure Pa (for example, about 250 mmHg). Until pressure (pressure) is reached, the pulse wave signal SM corresponding to one pulse wave is sequentially read together with the pressure signal SP representing the pressure P in the pressure chamber 44 in this slow pressure step-up process. Next, the maximum value of each pulse wave read in this way
_Mmax (mV) and the minimum value _Mmin (mV) are obtained, respectively, and the amplitude A of each pulse wave is obtained by calculating the difference between the maximum value _Mmax and the minimum value _Mmin . Then, the maximum value of the amplitude A for each pressure-sensitive element 60 is determined, and the pressure-sensitive element 60 that has output the pulse wave of the maximum amplitude A ^* among the maximum values of the amplitude A is the optimum pressure-sensitive element 60a. Is determined as Next, it is determined whether or not the optimum pressure-sensitive element 60a determined in this manner is located at substantially the center of the arrangement range R of the pressure-sensitive elements 60. If this determination is denied, after the pressing of the pulse wave sensor 46 is released by the pressing force control valve 14, the pulse wave sensor 42 is moved by a predetermined distance by the position control valve 16 and the radial artery 54 is aligned. It is located substantially at the center of the range R.

When the optimum pressure-sensitive element 60a is positioned substantially at the center of the arrangement range R of the pressure-sensitive elements 60 in this way, the pressing force control routine of step S2 is executed, and the pulse wave sensor
The optimum pressing force of 46 is determined and the pressing force is maintained. That is, from the data calculated and stored in the step S1, the pressure P in the pressure chamber 48 in a state where the output from the optimum pressure sensing element 60a has the maximum amplitude A ^*.
* Is determined as the pressure corresponding to the optimal pressing force of the pulse wave sensor 46, and the pressure P in the pressure chamber 48 is continuously adjusted to the pressure P ^* by the pressing force control valve 14. This allows
The pulse wave sensor 46 is pressed against the skin 40 with the optimum pressing force. In the present embodiment, the diaphragm 44, the pressing force control valve 14, and the like correspond to the pressing means of the pulse wave sensor 46.

When the pulse wave sensor 46 is positioned and pressed with the optimum pressing force in this way, a blood pressure value determination routine of step S3 is executed. That is, as shown in FIG. 5, first, the surface pressure value P _s is determined in step SS1, the surface pressure value P _s is the pressure corresponding to the elastic properties of the skin and subcutaneous tissue of the subject At a position separated by a predetermined distance from the optimal pressure-sensitive element 60a on the pressing surface 58 of the pulse wave sensor 46,
That is, the pressure is detected by the pressure-sensitive element 60 that is not located directly above the radial artery 54 and that is not directly pushing the bone or tendon. Specifically, a pressure-sensitive element 60 that outputs a pulse wave signal SM having a small amplitude (pp) and a small lower peak value (absolute value corresponding to DIASTOLIC) is determined, and the output from the pressure-sensitive element 60 is determined. lower peak value or average value of the signal is used as the surface pressure value P _s. In this embodiment, the above steps
SS1 corresponds to the surface pressure detecting means.

Next, in step SS2, the relational expression shown in a pre-stored equation to determine the blood pressure P _o (1) is, by the correction term of the second term of the right side of the expression is calculated, the equation is Will be corrected. The second term g (P _s ) on the right side of the equation (1) is
The function g (P _s ) is a function of the surface pressure value P _s , which is previously determined experimentally and is represented by, for example, a curve shown in FIG. so
It is stored in the ROM 30 in advance. Incidentally, (1) In the equation, the P _r is the actual pressure pulse wave values detected by the optimum pressure sensing element 60a. In the present embodiment, the above steps
SS2 corresponds to the relation correction means.

P _o = P _r + g (P _s ) (1) As described above, by calculating the correction term of the second term on the right side of equation (1), the relational equation of equation (1) is corrected. Then
In step SS3, the systolic blood pressure value and the diastolic blood pressure value are determined from the corrected relationship based on the pulse wave signal SM output from the optimal pressure-sensitive element 60a. That is, the upper peak value P _rh and the lower peak value _Prl of the SM of the pulse wave signal pulsating in synchronization with the heartbeat are determined, and the value calculated by substituting the upper peak value P _rh into the equation (1). the P _oh determined as the diastolic blood pressure value is to determine the diastolic blood pressure value calculated values P _ol by substituting the lower peak value P _rl in (1).

As described above, the systolic blood pressure value P _oh and the diastolic blood pressure value P _ol
Is determined, it is determined in step S4 of FIG. 4 whether the value is an abnormal value. The abnormality determination in step S4 is performed based on, for example, that the absolute value of the blood pressure value has exceeded the previously stored determination criterion value or that the difference from the previous blood pressure value has exceeded the previously stored determination criterion value. Will be Steps
If it is determined in S4 that the value is abnormal, the pulse wave sensor 46
Step S1 and subsequent steps are executed again in order to make the pressing state appropriate, but if it is determined that the values are not abnormal values, the systolic blood pressure value P _oh and the diastolic blood pressure value _Pol are displayed on the display 34 in step S5. After that, snap S3 and subsequent steps are executed again, and the blood pressure value is continuously monitored.

As described above, according to the blood pressure monitoring device of the present embodiment,
Sensitive surface pressure value P _s occurring in response to the elastic force of the skin and subcutaneous tissue of the subject, not located directly above the radial artery 54, yet positioned in a location that is not directly push the bones and tendons圧素Ko 60,
In other words, it detected by pressure sensitive elements 60 and outputting the amplitude (p-p) is small and the lower peak value (a value corresponding to Diastolic) is small pulse wave signal SM, based on the surface pressure value P _s ( Since the relationship of the expression 1) is corrected, the relationship for determining the blood pressure can be accurately obtained. Thus, a blood pressure value accurately corresponding to the pressure in the blood vessel 54 can be measured with high accuracy without using a cuff. As described above, since the blood pressure is determined without using the cuff, the structure and handling of the blood pressure monitoring device are simplified, and the blood pressure can be measured with high accuracy exceeding the accuracy of the blood pressure measurement method using the cuff. You get.

As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.

For example, in the above-described embodiment, the pressure-sensitive element 60 located at a position not directly above the radial artery 54 on the pressing surface 58 of the pulse wave sensor 46 and not directly pressing the bone or tendon.
Although the surface pressure value P _s has been detected by, it may be detected by pressure sensitive elements disposed between the semiconductor chip 56 separately.

Further, in the above-described embodiment, the plurality of pressure-sensitive elements 60 are provided in two rows on the pressing surface of the semiconductor chip 56, but may be one row or three or more rows.

Further, the equation (1) relationship of the foregoing examples, was the relationship between a linear expression with respect to the actual pressure pulse wave value P _r detected by the optimum pressure sensing element 60a, a multi-equation Is also good.

Further, in the above-described embodiment, the blood pressure value is obtained by the pulse wave detecting device 18 mounted so as to press the radial artery 54, but the pulse wave detecting device mounted on another site such as the dorsal foot artery. May be used to determine the blood pressure value.

Also, the function g (P _s ) of the second term on the right side of the above equation (1)
May be another function, such as a linear function.

The above is merely an example of the present invention, and the present invention can be variously modified by a person skilled in the art without departing from the purpose thereof.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. 2 and 3 are diagrams for explaining the configuration of the pulse wave detecting device of FIG. 1, respectively. FIG. 2 is a side view with a part cut away, and FIG. 3 is a bottom view. FIG. 4 is a flowchart for explaining the operation of the embodiment of FIG.
FIG. 5 is a diagram showing the steps of the blood pressure value determination rule in FIG. 4 in detail. FIG. 6 is a diagram showing an example of a function formula of the correction term of the relationship used in FIG. 46: pulse wave sensor (pressure sensor) 54: radial artery (artery) 58: pressing surface 60: pressure sensitive element SS1: surface pressure detecting means SS2: relation correcting means

Claims (1)

(57) [Claims] 1. A pressure sensor having a pressing surface on which a number of pressure-sensitive elements are arranged, wherein the pressure sensor is positioned so that the arrangement direction of the pressure-sensitive elements intersects the artery on the pulsation of a living body. By pressing a pressure sensor against the skin of the living body at a predetermined pressure, the pressure is generated from the artery based on a pulse wave signal output from a pressure-sensitive element located immediately above the artery among the pressure-sensitive elements. A blood pressure monitor of a type that detects a pressure pulse wave and determines the blood pressure value of the living body based on the magnitude of the actual pressure pulse wave from a relationship obtained in advance, wherein the artery is located on a pressing surface of the pressure sensor. Surface pressure detecting means for detecting a surface pressure received from the skin by a pressure-sensitive element located at a predetermined distance from a pressure-sensitive element located immediately above the sensor, based on the surface pressure detected by the surface pressure detecting means Relationship correction means for correcting the relationship by Blood pressure monitoring device, which comprises.