JPS63262125A - Blood pressure measuring method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Applicability Meter) The present invention is a non-invasive blood pressure monitor that is mainly attached to a finger, limb, tail, etc. The present invention relates to a method of measuring blood pressure by using optical means to detect a blood vessel diameter (volume) that changes depending on pressure and blood vessel internal pressure.

(Prior Art) Conventionally, it is convenient and meaningful to indirectly measure blood pressure using a finger or the like using this cage sphygmomanometer. For example, (1) US Pat. No. 4,406,289 uses a servo balance technique. On the other hand (2), in another example, U.S. Patent No. 4,597,39
3, there is also a method of estimating the diastolic blood pressure by calculation, assuming that the elasticity of blood vessels and surrounding tissue is linear. (3) Other examples include multiple cuffs and sensors, as seen in U.S. Pat. 〇 (Problem to be solved by the invention) However, in the case of conventional method (1), the device is large-scale, it takes time to wear and adjust it, and it is difficult to measure blood pressure at any time. The problem was that it was not suitable for the intended purpose. In the case of (2), in addition to the error caused by assuming linearity, there is also an increase in the amount of data due to calculating the area of a minute waveform, and errors that occur when trying to save the amount of data. have a problem. Next, in the case of (3), it is cumbersome because two or more items must be attached, and pressurization is not allowed for the peripheral detector because pressurization may cause an error. Furthermore, in determining the diastolic blood pressure, there have been problems such as it being impossible to determine it or the decision logic being ambiguous.

Therefore, it is an object of the present invention to solve the problems of measurement accuracy and device complexity that the prior art had, and to provide a highly accurate blood pressure monitor with a simple configuration.

(Means for Solving the Problems) In the present invention, means for solving the above-mentioned problems will be explained below using drawings corresponding to embodiments.

The first invention is a non-invasive blood pressure monitor, as shown in FIG. and a means for reducing pressure S1; an optical means E for detecting changes in blood vessel diameter (volume) that change due to applied force and internal pressure to the blood vessel;
In a blood pressure monitor consisting of a, Eb and Da, Db,
The device shown in FIG. 1 (1), the light emitting part Ea of the optical means,
Eb is plural, or light receiving parts Da and Db are plural. (
2) One of the light emitting (or light receiving) elements Ea (or Da) is positioned closer to the heart than the other light emitting (or light receiving) element Eb (or Db) (see FIG. 2). (3) The plurality of optical means are operated in a time-divisional manner. (4),
These optical means are shielded to block external light.

<5), i-r on the cardiac side and peripheral side as shown in Figure i1.
Two or more optical means (E.

It has means Cp for comparing the outputs of Da input (FA Db), and the systolic blood pressure is determined by optical means (Eb) located on the peripheral side.

Db), and the diastolic blood pressure is determined at the point at which the output Sd of the comparison means cp disappears.

The second invention has exactly the same configuration as the detection section of the first invention, but there is no shielding and the light receiving elements Da and Db receive light from the outside.
As shown in FIG. 6, (1) the optical means has a plurality of light emitting sections E^Eb or a plurality of light receiving sections D&Db. (2) One of the light emitting (or light receiving) elements Ea (or Da) is arranged so as to be located i1 closer to the heart than the other light emitting (or light receiving) element Eb (or Db). (3) Although the plurality of optical means are operated in a time-divisional manner as shown in FIG. 3, there is a phase in which all light emission is stopped. (4) a means (differential amplifier 2, n) for storing the light reception signal during rest in capacitors Ca, Cb, etc. and subtracting the stored signal from the signal when emitting light; and (5) cardiac side and peripheral side. Two or more optical means (Ea Da) in a relationship located at , (
The systolic blood pressure is determined by the appearance point of the output Ss of the optical means (Eh, Eb) located on the peripheral side, and the diastolic blood pressure is determined by the point of appearance of the output Ss of the optical means (Eh, Eb) located on the peripheral side, and the diastolic blood pressure is determined by the point of appearance of the output Ss of the optical means (Eh, Eb) located on the peripheral side. The determination is made at the time when the output Sd disappears.

The third invention is an additional invention to the first and second inventions, and as shown in FIGS. 7 and 8, the signal Sa'XSb' in FIGS. 1 and 6 is variable. By adding a gain amplifier, we first obtain a pressure value that is clearly smaller than the diastolic blood pressure (
For example, when reaching 30sa H9), both signals Sa',
A closed loop control circuit is temporarily activated to control the gain so that Sb' becomes equal, and the diastolic blood pressure can be measured with high accuracy.

(Function) When the first invention and the second invention are configured as above,
Once the bladder B is pressurized to a level higher than the systolic blood pressure by the pressurizing means S, and then the pressure is gradually reduced by the depressurizing means SK, J:
As shown in Fig. 4, the blood vessel volume change is also expressed by the signal Sa'XS.
b' changes as shown in Figure 5. Therefore, when the bladder pressure is higher than the systolic blood pressure, the blood vessels remain occluded and there is no blood flow (see Figure 4 (at). Since there is no blood flow , the blood vessel volume on the peripheral side does not change and the light Lb does not change, but the blood vessel volume on the heart side changes and the light La changes.

That is, the signal Sb1 is not present, and the signal Sa' is generated (on the left side of the fifth factor).

When the bladder king drops slightly below the systolic blood pressure, blood vessels open and blood flow occurs only during the period when the internal pressure is higher than the external pressure.
Figure 4 (see bl). Due to this, a change in light LbK appears and an n1 signal sb° is generated (see the systolic blood pressure point in Figure 5).

When the bladder pressure becomes lower than the diastolic blood pressure, there is no period during which the blood vessel closes (see FIG. 4 (cl)), the changes to the lights La and Lb become equal, and the signals Sa' and Sb' also become equal.

Therefore, the comparison means cp compares the signals Sa' and Sb' and outputs the difference Sd, so that the output becomes zero at the diastolic blood pressure (see below the diastolic blood pressure in the lower part of FIG. 5).

In this way, the systolic blood pressure can be determined from the point at which the signal Sbl appears, and the diastolic blood pressure can be determined from the point at which the signal Ss representing the difference between Sa'XSb' disappears.

The third invention is based on the waveform from two positions for determining the diastolic blood pressure, since there are variations in the sensitivity of light receiving elements such as LEDs of light emitting elements and phototransistors, not only due to biological causes but also due to equipment side. This is to make the output match more completely, and the gain is controlled in advance so that both the signals sa1 and sbl are equal.
Therefore, the diastolic blood pressure can be measured with good accuracy.

(Example) Fig. 2 is a partially cutaway cross-sectional view showing the configuration of the detection unit of the present invention, where F is a human finger whose left half is shown in cross-section, A is an artery in the finger F, and B is an air pressure Prada-1C is a cuff that restricts the expansion of Prada-B, S is a pressurization device that controls the air pressure inside Prada-B, EalEb is a light emitting element such as an InfraRed LED, and Da and Db are e.g. Shows a light receiving element such as a phototransistor. In the figure, the light-emitting element Ea and the light-receiving element Da are arranged facing each other so that the light from the light-emitting element Ea reaches the finger (including the artery). For example, if Prada B is opaque, finger F
It is placed between the Prada B and Prada B. But if Prada
If B is transparent, it may be on the inner surface of Prada B or between Prada B and cuff C. Further, the light emitting element Eb and the light receiving element Da are also placed facing each other. However, the light emitting element Ea
The light-receiving element Da is placed closer to the heart than the center of Prada-B, and the light-emitting element Eb and the light-receiving element Db are placed closer to the periphery than the center of Prada-B.

Then, the light La that comes out of the light emitting element Ea and reaches the light receiving element DaK changes the flow rate of the light due to a volume change according to the internal pressure of the artery (blood vessel) A, and outputs a signal to the light receiving element Da. Similarly, from the light receiving element Db, a signal output of the light LbK, J: the arterial volume change emitted from the light emitting element Eb is obtained.

In this case, if the light emitting element and the light receiving element receive external light components, there is a possibility that an error may occur in the measurement. Therefore, as a method for avoiding the occurrence of this error, the first invention protects the optical means by blocking external light. For example, wear gloves.

Next, the second invention is designed to electrically remove external light even if it is received.

First, the first invention will be described.

In this case, the light emitting elements Ea and Eb are caused to emit light alternately using a two-phase clock so that their light emitting times do not overlap. Also,
The light receiving elements Dh and Db are switched in synchronization with the light emission clock, and the light L of the light emitting elements Ea and Eb facing each other is switched.
Receives the light reception signal of only the light of a and Lb. Note that the blinking frequency of these lights should be at least 60 times the expected maximum pulse rate in order to reproduce the correct pulse waveform.

Next, the operation will be explained using the circuit diagram shown in FIG.

First, in phase P, the light emitting element Ea emits light via the switches SW, , w, and the light receiving element Da is shielded from external light, so it receives only the light La from the light emitting element Ea. This is replaced with a voltage signal and amplified by the n1 amplifier A to become a signal Sa.

Next, in phase P, the light emitting element Eb emits light as described above, and the light receiving element Db receives light Lb, resulting in a voltage signal sb. These signal voltages Sa and Sb are detected by the detectors D+ and D.
The wave is detected by z. That is, the clock component which is the carrier is removed and the signal Sa' corresponding to the change in the body ff of the blood vessel is obtained.
Obtain Sb'. Then, comparator cp causes signals Sa1, S
b1 is compared and outputs n1 70 difference Sd ◎Then, when both waveforms and amplitudes match, the output will be zero.

In the above configuration, the systolic blood pressure (SY-3TOI
JC), fi low m E (DIASTOLIC) is determined as Noyo'+Ic will be explained based on FIGS. 4 and 5.

First, Prada B is once pressurized to a level higher than the systolic blood pressure by the pressurizing means S. Next, the pressure is gradually reduced by the pressure reducing means SK, but at this time the blood vessel volume changes as shown in Figs.
, (cl), and the signals sa' and sb' change as shown in Figure 5. That is, when the Prader pressure is higher than the systolic blood pressure, the blood vessel remains occluded and there is no blood flow. (See FIG. 4 (at)) Therefore, since there is no blood flow, the blood vessel volume on the peripheral side does not change and there is no change with respect to the light Lb, but the blood vessel volume on the heart side changes and the light La changes. That is, there is no signal sb1, and a signal SaI is generated (see the left side of Figure 5).0 And when King Prada's blood pressure falls slightly below the systolic blood pressure, the blood vessels are closed only during the period when the internal pressure is high and the external pressure is also high. It opens and blood flow occurs (see FIG. 4(b)). This causes a change to the light Lb, and a signal sb+ is generated (see FIG. 5, 5YSTOLIC).

Next, when the Prader pressure becomes lower than the diastolic blood pressure, the blood vessels no longer have a closing period (see FIG. 4(c)), and the changes in the lights La and Lb become equal to 0, that is, the signals Sa' and Sb' also become equal. Therefore, comparator cp receives signals Sa', sb'
Since the difference Sd is outputted, the diastolic blood pressure is determined by the output bar!!'
(see DIASTOLIC).

In this way, the systolic blood pressure can be determined from the point at which the signal Sb1 appears, and the diastolic blood pressure can be determined from the point at which the difference signal Sd between the signals Sa'XSb' disappears.

Next, the second invention will be explained.

The detection section in FIG. 2 has exactly the same configuration as the first invention, and the outside thereof is not shielded. Therefore, the light receiving element D^Db also receives light from the outside. In that case, the light emitting elements Ea and Eb are multi-layered. To emit light using a phase clock so that the light emitting times do not overlap.

Further, the light receiving elements Da and Db are switched in synchronization with the light emission clock. As shown in FIG. 3, in phase P, the light-emitting strand Ea emits light;

In phase P, the light emitting element Eb emits light, and in phase P, neither emits light.The blinking frequency of these light emissions is set at 60 times or more the expected maximum pulse rate in order to reproduce the correct pulse waveform.

Note that there is a phase Ps in which both light emitting elements Ea and Eb do not emit light.
, the light receiving elements Da and Db receive external light Lc. That is, ambient light (electric lighting or sunlight) illuminates the finger F, and at both ends of the cuff C, the light is scattered by the tissue of the finger F, and the light receiving element Da.

Arrive at Db. Let this be Lc.

Next, the operation will be explained with reference to FIG.

The signal obtained from the light receiving element DaK is sent to the amplifier A.

is amplified by the differential amplifier A via the switch 5w1t.
Guided by a+. In this case, the operation of the switch groove t and the differential amplifier A, 1 will be explained. In phase PI, the light emitting element Ea emits light via the switch groove. The light receiving element Da receives the light La from the light emitting element Ea, but at the same time it also receives the external light Lc ◇ That is, at phase P, the light L
It receives light at a-+-Lc'. This n is replaced with a voltage signal and amplified by the n1 amplifier A1, resulting in a signal Sa+Sc.

Next, in the phase P, the light emitting element Eb
emits light, and the light-receiving element Db receives the light Lb-1 (, c, resulting in a voltage signal Sb + Sc.Furthermore, at phase P, only the light Lc is received as described above, but the signal Sc at this time is It is connected to the non-inverting input side of two differential amplifiers A87 and 2 by the switch groove s'w32.

However, the capacitors Ca and C are connected to the non-inverting input terminal.
b is connected, the signal voltage at this time is phase P,
It is held on the non-inverting input side even after completing the process.

Moreover, in phase PI, the signal Sa + Sc is connected to the inverting input side of the differential amplifier As+, and the switch history 8. Therefore, the differential amplifier A31 outputs a signal of the difference between both inputs, that is, 5c - (Sa + 5c) = -8a
Similarly, in phase P, the differential amplifier Aa is 5c-
(Sb+5c)--8b signal is output.

In this way, only the signal component from which the signal Sc due to external light has been removed is output from the differential amplifiers A□, N,. Next, these signal voltages Sa and Sb are detected by detectors D1 and Dt. That is, the clock component, which is a carrier, is removed to obtain signals Sa' and Sb' corresponding to changes in blood vessel volume. The above is based on the signal Ba using the same comparator cp as in the first invention.
118b1 compares n and outputs the difference Sd. Therefore, when both waveforms and amplitudes match, the output becomes zero.

In the above configuration, the systolic blood pressure (SY-3TOL
IC), fi low surface EE (DIASTOLIC) is determined to 17) J:5 is exactly the same as in the first invention, so the explanation will be omitted.

According to the above method, the diastolic blood pressure can be measured with high accuracy, but due to, for example, variations in the elements, causes on the biological side, etc., it is necessary to more completely match the waveform outputs from the two positions to determine the diastolic blood pressure. The improvements for this purpose are described below.

FIG. 7 is a circuit diagram thereof, and FIG. 8 is an explanatory diagram of its operation.

In the figure, the signals Sa' and Sb' are the respective signals corresponding to the volume change of the blood vessel shown in Figure 1, and one of the signals
After passing through a variable gain amplifier, the signal is input to the comparator circuit Cp shown in FIG. Next, both signals should be equal.
Control the gain of a variable gain amplifier.

That is, a closed loop control is temporarily activated in which the output from the comparator Cp is connected to a variable gain amplifier via an amplifier.

This is done at the beginning of the pressurization process in the process shown in FIG. 8, when a pressure value Pc (for example, 30 va Hf) which is clearly smaller than the diastolic blood pressure is reached. At this time, pressurization is stopped for t time to keep the pressure constant.

The reason is that below the diastolic blood pressure, the signal Sa must be equal to 118bl, ◇ that is, the output of the comparator circuit Cp must be zero. However, if the signals Sa', S
If b' are not equal, the output of the comparator Cp is not zero. If the output of the comparator circuit Cp is zero, the output of the comparator circuit Cp is added to the variable gain amplifier 9 to control the gain and the comparator circuit Cp.

Control the output so that it becomes zero.

This control value is stored, for example, until the measurement is finished.
As soon as the pressure is stored and held in the electric device CC, the pressure is increased again, and the measurement is started as described above after the pressure is increased to a level higher than the systolic blood pressure. Note that this variable gain amplifier may be constructed, for example, by using a switch to select a resistor that determines the gain of the amplifier. Moreover, the switch can also be controlled by a digital signal. This method absorbs not only causes on the biological side but also causes on the equipment side, such as variations in sensitivity of LEDs and phototransistors.

This idea of matching the outputs of the two sets of optical systems at low pressures can also be realized by other means. An example of this is given below.

The second step is to replace some of the analog means with digital means, as shown in FIG. That is, the optical means are the same as those described in FIG. 1 and FIG. 6, but the differential amplifier As1, the differential amplifier As1, the detection circuit 7, D2, and the comparison circuit CP are not provided. These functions are performed digitally, i.e. each output of the two sets of optical means is connected to a transducer C.
t and stored in the memory M as n1 digital quantities. Of course, the output when the light emitting element is not emitting light in phase P3 is also stored separately. Also, differential amplifier I, A
The role of 32 is to remove the influence of external light, which is to subtract the signal at phase P from the signal at phase P. Similarly, the same is true for phase P,
Since each signal is stored as a digital quantity, the purpose can be easily achieved by digital subtraction by the central processing unit CPU. Next, the role of the detection circuits 0 and D2 is to extract the frequency component of the pulse wave. That is, the clock component (carrier) is removed. Therefore, since the converter can be made to operate synchronously with the clock, the clock component is automatically removed. Furthermore, the comparison circuit Cp can also be implemented digitally.

This method (some analog components can be omitted, but requires many memory devices).

It goes without saying that the present invention can be applied not only to human fingers but also to animal limbs and tails.

(Effects of the Invention) Since it is difficult to determine the diastolic blood pressure with one set of conventional optical systems, the average blood pressure has been determined in addition to the systolic blood pressure. In order to obtain the average blood pressure more accurately, the optical means was placed near the center. However, this resulted in obtaining a signal between the signals Sa" and Sb" according to the volume change of the blood vessel in the present invention. , the systolic blood pressure is clearly measured higher than the actual one. Also, since the distance between the two sets of optical means is short, there is little difference in the physical properties of the blood vessels and cortex (and the phase difference is also small).

Furthermore, since the same pressure is applied to both optical systems, the outputs at the diastolic blood pressure match with high precision. Furthermore, time-divisional light emission is effective in reducing power consumption, but providing a phase P in which both light emitting elements do not emit light and lengthening this time further enhance this effect.

As explained in detail above, compared to the method in which one set of optical means is provided in the center of the pressurizing part, the systolic blood pressure can be measured better, and since the distance between the two sets of optical means is short, It is possible to measure diastolic blood pressure with higher accuracy compared to the method of placing a sensor on the wall. Furthermore, time-division lighting has five effects: removing extraneous light, removing mutual interference between two sets of optical means, and reducing power consumption.

[Brief explanation of drawings]

Fig. 1 is a signal processing circuit diagram according to a blood pressure measurement method showing an embodiment of the invention, Fig. 2 is a partially cutaway @ side view of the configuration of the detection unit of the invention, and Fig. 3 is a diagram of blinking light emitted from a light emitting element. 4 and 5 are illustrations of blood vessels and blood flow that determine the systolic and diastolic blood pressures. FIG. 6 is a signal processing circuit diagram showing another embodiment of the present invention. FIG. 7 8 is a partially added circuit diagram for improving the present invention, FIG. 8 is an explanatory diagram of its operation, and FIG.
The figure is a signal processing circuit diagram showing another embodiment of the present invention. Ea, Eb... Light emitting element, Da, Db... Light receiving element, A5... Amplifier, N As,... Differential amplifier, D Insertion... Detector, Cp.・Comparator, A・
...Artery, B...Prada-1C...Cuff, F...
Finger, S... Pressure regulator, Hm... Variable gain amplifier,
C1... Le ■Converter, M... Memory, CPU...
Central processing unit. Patent Applicant Japan Precision Instruments Co., Ltd. Title A Government Name Shaku Rinku H4 1st Cause R, La Q-To-pl, Lb W Hi@J Figure 5 La lb Bloody Blood Rebellion im+21 Figure 4 Kaimaru line Kata Iguchi movement explanation diagram ε mouth

Claims (3)

[Claims] (1) A non-invasive blood pressure monitor that is attached to a finger, limb, tail, etc., and includes a means for pressurizing a part thereof, a means for increasing and decreasing the pressure of this pressurizing means, and the pressurizing force and the inside of a blood vessel. In a sphygmomanometer comprising optical means for detecting changes in blood vessel diameter or volume that vary with pressure, at least one of the light emitting part or the light receiving part of the optical means has a plurality of elements, and these plural optical means are connected to an external The light from the
One of the light-emitting or light-receiving elements is arranged so as to be located closer to the heart than the other light-emitting or light-receiving element, and the systolic blood pressure is determined by the output of the optical means located on the peripheral side; A blood pressure measurement method characterized in that the outputs of two or more peripherally located optical means are compared, and the diastolic blood pressure is determined based on the output of the comparison means. (2) A non-invasive blood pressure monitor, which is attached to a finger, limb, tail, etc., and means for pressurizing a part thereof;
A means for increasing and decreasing the pressure of this pressurizing means, and a change in blood vessel diameter or volume that changes depending on the pressurizing force and the internal blood vessel pressure.
In a blood pressure monitor consisting of an optical means for detection, at least one of the light emitting part and the light receiving part of the optical means has a plurality of elements, and these plurality of optical means operate in a time division manner, and all the light emitted has a phase in which the light-emitting or light-receiving element is at rest, and further includes means for storing the light-receiving signal at rest and means for subtracting the stored signal from the signal when emitting light; Systolic blood pressure is determined by the output of an optical means disposed on the heart side and disposed on the peripheral side, while each output of two or more optical means located on the heart side and the peripheral side is determined. A blood pressure measuring method characterized in that the diastolic blood pressure is determined based on the output of the comparing means. (3) A non-invasive blood pressure monitor that is attached to a finger, limb, tail, etc., and includes a means for pressurizing a part of the blood pressure monitor, a means for adjusting the pressure of this pressurizing means, and a means for controlling the pressurizing force and internal blood vessel pressure. In a blood pressure monitor comprising an optical means for detecting a changing blood vessel diameter or volume change, at least one of the light emitting part or the light receiving part of the optical means has a plurality of elements,
These plurality of optical means block external light or are not related to light reception, and are located on the peripheral side so that one of the light emitting or light receiving elements is located closer to the heart than the other light emitting or light receiving elements. The systolic blood pressure is determined by the output of the optical means that performs the calculation, and the outputs of two or more optical means located on the cardiac side and the peripheral side are compared, and the diastolic blood pressure is determined from the output of the comparing means. In the blood pressure measurement method, in the process of processing the signals from the plurality of optical means, an amplifier whose gain can be varied for any one or more of the signals is added, and at the beginning of pressurization in the pressurization process, Stop pressurization at a pressure lower than the diastolic blood pressure of the majority of people, and control the gain of the variable gain amplifier so that the outputs of the two or more optical means are equal while the pressure is maintained approximately constant. A blood pressure measurement method characterized by measuring the diastolic blood pressure.