JP2023158983A - Blood pressure measuring apparatus - Google Patents

Abstract

To provide a blood pressure measuring apparatus capable of estimating diastolic pressure with high accuracy.SOLUTION: An intercept β and an inclination α included in a linear regression line expression (2) leading a diastolic pressure estimation equation (5) are mutually in a constant linear relation as shown in equation (4) and are not influenced by a person to be measured, and thus are unlikely to be influenced by individual biological features of a person to be measured, so diastolic pressure value DAPe can be measured with high accuracy. There is a merit that there is no need to perform calibration as a conventional one which performs blood pressure estimation using pulse wave velocity PWV.SELECTED DRAWING: Figure 5

Description

The present invention includes a compression band that is wrapped around a compressed area that is a part of a living body, and calculates the diastolic (minimum) blood pressure of the living body based on the compression pressure by the compression band and the pulse wave propagation velocity of an arterial blood vessel passing through the compression area. The present invention relates to a blood pressure measuring device and a blood pressure measuring method for estimating blood pressure.

Blood pressure measurement using the Korotkoff sound auscultation method, which is commonly used in clinical practice, uses a compression cuff attached to the upper arm, and during the process of changing the compression pressure of the compression cuff, vascular sounds (Korotkoff sounds) are generated in synchronization with the heartbeat. ), the systolic blood pressure value SAP and the diastolic blood pressure value DAP are determined based on the compression pressure Pc at the time of occurrence and disappearance. The systolic blood pressure value SAP and diastolic blood pressure value DAP determined by this auscultation method are most trusted among medical professionals. Since blood pressure measurement using this auscultation method is highly specialized, automatic blood pressure measurement devices that determine blood pressure values using the oscillometric method, which is easy to operate, are recommended for daily blood pressure monitoring at home or in non-medical institutions. Common.

In the oscillometric method, a compression cuff similar to the auscultation method is used, and in the process of increasing the pressure to a pressure higher than the systolic (systolic) blood pressure value and then lowering the blood pressure, the cuff pulse, which is a minute fluctuation component superimposed on the compression pressure of the compression cuff, is used. By extracting the cuff pulse wave (volume pulse wave) and applying a predetermined threshold value experimentally or empirically, the pressure of the compression cuff when the amplitude of the cuff pulse wave suddenly changes can be calculated as the systolic blood pressure. and diastolic blood pressure. Since the physical relationship between the auscultation method and the oscillometric method is not clear, the threshold used to determine a sudden change in the amplitude of the cuff pulse wave when determining systolic and diastolic blood pressure is not clear. The value is preset using a constant based on the maximum value observed in the compression pressure corresponding to the mean blood pressure value MAP, and is made to match the value measured by the auscultation method. For example, the blood pressure measuring devices described in Patent Document 1 and Non-Patent Document 1 are examples thereof.

Another method for estimating the blood pressure value is to estimate the pulse wave obtained from the compression pressure of the compression cuff from the time when the R wave of the electrocardiogram occurs, based on the preset relationship between the blood pressure value of the living body and the pulse wave propagation velocity of the living body. A method is known in which the pulse wave propagation velocity is calculated from the time difference (pulse wave propagation time) from the time of occurrence, and the blood pressure value of the living body is estimated based on the actual pulse wave propagation velocity from a preset relationship. For example, the blood pressure monitoring device described in Patent Document 2 is one example.

Japanese Patent Application Publication No. 2012-071059 Japanese Patent Application Publication No. 2000-116608

L.A.Geddes, M.Voelz, C.Combs, D.Reiner, C.F.Babbs, “Characterization of the oscillometric method for measuring indirect blood pressure,” Ann. Biomed Eng., vol. 10, pp. 271-280, 1982 F. K. Forster and D. Turney, “Oscillometric determination of diastolic, mean, and systric blood pressure-A numerical model,” J. Biomech. Eng., vol. 108, pp. 359-364, Nov. 1986. Forouzanfar M, Dajani HR, Groza VZ, Bolic M, Ratkin I. “Oscillometlic blood pressure estimation: past, present, and future.”IEEE Rev Biomed Eng 2015;8:44-63.

When measuring blood pressure using the oscillometric method, a preset threshold using a constant based on the average blood pressure value MAP is uniformly applied to each individual blood pressure measurement in order to match the measured value using the auscultation method. The relationship between the threshold value and the actual blood pressure value may be affected by the individual biological characteristics of the subject, such as arterial vascular compliance, pulse rate, pulse pressure value, and arterial pulse pressure, which may reduce the accuracy of blood pressure measurement. There was a problem. Such a problem is pointed out in Non-Patent Document 2.

In addition, when estimating blood pressure using the pulse wave velocity calculated based on the time difference between the R wave of the electrocardiogram and the detection of the pulse wave, the time from the generation of the R wave of the electrocardiogram until the heart starts ejecting blood is calculated. (Pre-ejection period PEP) is included in the time difference, and is measured not as a strict pulse wave propagation time PTT but as a pulse wave arrival time PAT (Pulse Arrival Time). Therefore, an error occurs in the calculation of the pulse wave propagation velocity, resulting in a large blood pressure measurement error. In addition, the pulse wave from the heart is propagated to the brachial artery (muscular artery) through the aortic artery (elastic artery), but the propagation time is not in a strict sense because the composition of the blood vessels is different. Such a problem is pointed out in Non-Patent Document 3.

Blood pressure measuring devices with large blood pressure measurement errors increase the possibility that insufficient antihypertensive treatment will cause hypertension to persist, or excessive antihypertensive treatment will cause hypotension, increasing the risk of vascular complications and dementia. This contributes to problems such as On the other hand, a blood pressure measuring device that can measure blood pressure values with high precision can reduce insufficient antihypertensive treatment that causes hypertension, reduce the possibility of hypotension caused by excessive antihypertensive treatment, and prevent vascular complications. It can reduce the risk of inducing dementia.

The present invention was made against the background of the above circumstances, and its purpose is to be able to measure diastolic (minimum) blood pressure values with high precision, which is not easily influenced by the individual biological characteristics of the subject. An object of the present invention is to provide a blood pressure measuring method and a blood pressure measuring device.

After various studies, the present inventors found that the cross-sectional area of the arterial blood vessel is the cross-sectional area Ao of the arterial blood vessel when the transmural pressure Pt at the time of diastolic blood pressure (= diastolic blood pressure DAP - compression pressure Pc) is zero. The relationship between the transmural pressure Pt and the square value of the pulse wave velocity PWV ² obtained by applying the Bramwell-Hill formula to the blood vessel model equation that expresses the relationship between A and the transmural pressure Pt of the arterial blood vessel as a mathematical formula. The ^theoretical nonlinear exponential function curve (Equation (1)) showing I discovered the fact that They also found that the relationship shown by swapping the horizontal and vertical axes of the exponential function curve can be approximated with high accuracy to the logarithmic relational expression (2), regardless of the constant b or the cross-sectional area ratio Ao/Am. . The logarithmic relational expression (2) can be regarded as a linear regression equation with a slope α and an intercept β, if the logarithm of the square value of the pulse wave velocity PWV ² is considered as an independent variable, and the slope α and the intercept β are In between, there are points in the linear relationship equation (4) that is constant regardless of the person being measured, and the linear regression equation (2) can be transformed as shown in equation (3), so the slope α is the pulse wave It can be calculated from the regression analysis of the logarithm of the propagation velocity PWV ² and the compression pressure Pc, and the intercept β of the linear regression equation can be calculated from the linear relational expression (4) based on its slope α, and the slope α and intercept β are applied. It has been found that the diastolic blood pressure value DAPe can be estimated from the diastolic blood pressure value estimation formula (5) based on the square value PWV ² of the actual pulse wave propagation velocity and the compression pressure Pc.

PWV ² = (1/ρ・b) (1/(1-Ao/Am))・e^(b・Pt)
-(1/ρ・b) ... (1)
Pt=α・ln(PWV ² )+β... (2)
-Pc=α・ln(PWV ² )+(β-DAP)... (3)
β=γ・α+δ... (4)
DAPe=α・ln(PWV ² )+(β+Pc)... (5)

That is, in the blood vessel model equation, since the transmural pressure Pt of the arterial blood vessel is the estimated diastolic blood pressure DAPe - compression pressure Pc, the transmural pressure Pt of the arterial blood vessel and the logarithm of the square value of the pulse wave propagation velocity PWV ² The linear regression equation (2) expressing the relationship can be transformed into equation (3) with respect to the trans-wall pressure Pt. The slope α of Equation (3) is the same as Equation (2), and the slope α is obtained by regression analysis of the logarithm of the actually measured compression pressure Pc and the square value PWV ² of the pulse wave propagation velocity. . In this way, the slope α itself unique to each subject can be calculated even if the diastolic blood pressure DAP is unknown, that is, even if the transmural pressure Pt is unknown. By substituting the calculated slope α into the empirically established linear relationship (4) between the predetermined slope α and the intercept β, the intercept β unique to each subject can be determined. . Once the slope α and intercept β unique to each subject are determined in this way, the diastolic blood pressure DAPe can be expressed by the diastolic blood pressure estimation formula (5), which is a modification of the formula (3) for the transmural pressure Pt. Ru. As a result, the diastolic blood pressure estimation formula (5) is set, which uses the compression pressure Pc and the square value PWV ² of the pulse wave velocity as variables, and includes the slope α and the intercept β. From this diastolic blood pressure value estimation formula (5), based on the actual compression pressure Pc for the compression site of the measurement subject and the pulse wave propagation velocity in the arterial blood vessel passing through the compression site of the measurement subject, the dilation of the measurement subject is calculated. Periodic blood pressure can be estimated. The present invention has been made based on this knowledge.

The gist of the first invention is as follows: (a) the compression pressure by the compression band that compresses the arterial blood vessel at the compressed site of the subject and the square value of the pulse wave propagation velocity of the arterial blood vessel passing through the compressed site; (b) a pulse wave velocity that measures the pulse wave velocity PWV of the compressed area under compression by the compression band; and (c) measurement at the compression pressure and the compression pressure from the conversion equation from the linear regression equation between the logarithm of the square value of the pulse wave propagation velocity and the transmural pressure of the arterial blood vessel. (d) a slope calculation unit that calculates a slope α of the linear regression equation based on the pulse wave propagation velocity of the compressed area; and (d) a slope calculation unit that calculates the slope α of the linear regression equation based on the (e) an intercept calculation unit that calculates an intercept β of the linear regression equation based on the slope α of the linear regression equation from a pre-stored linear relationship between; the compression pressure to be subtracted from the diastolic blood pressure representing pressure, the pulse wave propagation velocity of the compressed area, the slope of the linear regression equation calculated by the slope calculation unit, and the slope of the linear regression equation calculated by the intercept calculation unit. a diastolic blood pressure estimation equation setting unit that sets a diastolic blood pressure estimation equation by substituting the intercept of the linear regression linear equation; and (f) determining the actual compression pressure Pc and the compressed area from the diastolic blood pressure estimation equation. and a diastolic blood pressure estimation unit that estimates the diastolic blood pressure DAP of the subject based on the pulse wave propagation velocity PWV.

The gist of the second invention is that in the first invention, the linear regression equation is expressed by the equation (2).

The gist of the third invention is that in the first or second invention, the conversion equation from the linear regression equation is expressed by the equation (3).

The gist of the fourth invention is that in any one of the first to third inventions, the linear relationship is expressed by the equation (4).

The gist of the fifth invention is that in any one of the first to fourth inventions, the diastolic blood pressure estimation formula is expressed by the formula (5).

The gist of the sixth invention is that in the invention according to any one of the first to fifth inventions, the diastolic blood pressure estimating section calculates a plurality of types of compression pressures by the compression band from the diastolic blood pressure estimation formula. Each time, the diastolic blood pressure of the subject is estimated based on the actual compression pressure Pc and the pulse wave propagation velocity of the compressed area, and the diastolic blood pressure obtained by estimating each of the plurality of types of compression pressure is The average value of blood pressure is determined as diastolic blood pressure.

The gist of the seventh invention is that, in the invention according to any one of the first to sixth inventions, the diastolic blood pressure estimating unit may set the pressure to be lower than the diastolic blood pressure DAP of the subject. The method estimates the diastolic blood pressure DAP of the subject based on the actual compression pressure and the pulse wave velocity PWV of the compressed area in the compression pressure applied by the band.

The gist of the eighth invention is that, in the invention according to any one of the first to seventh inventions, the pair of pairs are arranged at two positions separated by a predetermined distance from each other along the arterial blood vessel to detect pulse waves. The pulse wave sensor includes a pulse wave sensor, and the pulse wave propagation velocity is calculated based on the time difference between the pulse waves respectively detected by the pair of pulse wave sensors and the predetermined distance.

The gist of the ninth invention is that, in the invention according to any one of the first to eighth inventions, the compression pressure control unit maintains the compression pressure by the compression band at a monitored pressure lower than the diastolic blood pressure of the living body. , a blood pressure fluctuation determination unit that determines the occurrence of a blood pressure fluctuation based on the fact that the pulse wave propagation velocity measured during the period in which the monitor pressure is maintained is out of a preset fluctuation determination range, The diastolic blood pressure estimating section calculates, from the diastolic blood pressure estimation equation, the actual compression pressure and the pulse wave velocity of the compressed region when the blood pressure fluctuation determination section determines that a blood pressure fluctuation has occurred. The object of the present invention is to estimate the diastolic blood pressure of the subject.

According to the blood pressure measuring device of the first aspect, the intercept and slope included in the linear regression equation that leads to the diastolic blood pressure estimation equation have a constant linear relationship with each other and are not influenced by the person to be measured. Therefore, the diastolic blood pressure value can be measured with high accuracy because it is not easily influenced by the individual biological characteristics of the subject. Further, there is an advantage that there is no need to perform calibration for each subject, unlike the conventional method of estimating blood pressure using pulse wave propagation velocity.

According to the blood pressure measuring device of the second aspect of the invention, the preset linear regression equation representing the physical model equation of the arterial blood vessel is expressed by the equation (2) above. The linear regression equation shows the actual behavior of blood vessels, in which the blood vessel cross-sectional area is greater than zero when the transmural pressure is zero, and as the transmural pressure increases, the blood vessel cross-sectional area increases and becomes saturated. , the physical model equation (a1) of arterial blood vessels, and the Bramwell-Hill equation (a3), so the diastolic (minimum) blood pressure value can be measured with high accuracy.

According to the blood pressure measuring device of the third aspect of the invention, the conversion equation from the linear regression equation is expressed by the equation (3) above. Based on the conversion formula (3), even if the diastolic blood pressure and intercept are unknown, the slope can be calculated by linear regression analysis of the logarithm of the square of the pulse wave propagation velocity obtained by actual measurements and the compression pressure. be able to.

According to the blood pressure measuring device of the fourth invention, the linear relationship is expressed by the equation (4). The linear relationship indicates that the intercept and slope included in the linear regression equation have a fixed linear relationship with each other regardless of the individual values, and this relationship is not influenced by the person being measured. Therefore, the diastolic blood pressure value can be measured with high accuracy without being affected by the individual biological characteristics of the subject.

According to the blood pressure measuring device of the fifth invention, the diastolic blood pressure estimation formula is expressed by the formula (5). The diastolic blood pressure estimation formula is a formula that uses measurable compression pressure and pulse wave velocity as variables, and the intercept and slope included in the linear regression equation calculated from these two measurable variables. Therefore, by substituting and calculating the two measured variables, the diastolic blood pressure of the subject can be estimated.

According to the blood pressure measurement device of the sixth aspect, the diastolic blood pressure estimating section calculates the actual compression pressure Pc and the compressed site from the diastolic blood pressure estimation formula for each of the plurality of types of compression pressures by the compression band. The diastolic blood pressure DAP of the subject is estimated based on the pulse wave propagation velocity of each of the plurality of compression pressures, and the average value of the obtained diastolic blood pressures is determined as the diastolic blood pressure. Therefore, the diastolic blood pressure value can be measured with higher accuracy.

According to the blood pressure measurement device of the seventh aspect, the diastolic blood pressure estimating unit is configured to calculate the actual compression pressure Pc and the compression pressure of the compression band set lower than the diastolic blood pressure of the subject. Since the diastolic blood pressure DAP of the subject is estimated based on the pulse wave propagation velocity at the compression site, the burden (stress) of compression by the compression band on the subject is reduced, stable blood pressure values are obtained, and the blood pressure is increased. Measurement accuracy is improved.

According to the blood pressure measuring device of the eighth aspect of the invention, the predetermined distance is based on the time difference between the pulse waves respectively detected by a pair of pulse wave sensors arranged at two positions separated by a predetermined distance from each other along the arterial blood vessel. The pulse wave propagation velocity is calculated. As a result, the delay time from the R wave generation point to the start of cardiac ejection (pre-ejection Since there is no error in time), diastolic blood pressure can be estimated with high accuracy. That is, according to the eighth invention, since the pulse wave propagation time is measured which purely reflects only the characteristics of the arterial blood vessels, it is influenced by the fluctuation of the delay time (pre-ejection time) which also depends on the state of the heart. The reproducibility of blood pressure measurements is high.

According to the blood pressure measuring device of the ninth aspect of the invention, there is provided a compression pressure control unit that maintains the compression pressure by the compression band at a monitor pressure lower than the diastolic blood pressure of the living body; a blood pressure change determination section that determines the occurrence of blood pressure fluctuation based on the fact that the pulse wave propagation velocity deviates from a preset fluctuation determination value; When it is determined that a fluctuation has occurred, the diastolic blood pressure of the subject is estimated from the diastolic blood pressure estimation formula based on the actual compression pressure and the pulse wave propagation velocity of the compressed area. Thereby, long-term blood pressure monitoring can be performed with less burden on the person being measured.

FIG. 1 is a block diagram illustrating the configuration of a blood pressure measuring device that is an embodiment of the present invention. FIG. 2 is a diagram illustrating the compression band of FIG. 1 with a part of the outer circumferential surface cut away. FIG. 3 is a plan view showing an upstream inflation bladder, an intermediate inflation bladder, and a downstream inflation bladder provided in the compression band of FIG. 2. FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, showing the upstream inflation bag, intermediate inflation bag, and downstream inflation bag cut in the width direction. 2 is a functional block diagram for explaining main parts of control functions provided in the electronic control device of FIG. 1. FIG. 6 is a time chart illustrating a main part of the compression pressure control operation by the compression pressure control section of FIG. 5. FIG. FIG. 2 is a diagram showing a theoretical blood vessel model expressing the relationship between transmural pressure and cross-sectional area of an arterial blood vessel in a living body. The relationship between the transmural pressure and the square value of the pulse wave velocity, which is a summary of the equation showing the relationship between the transmural pressure and the cross-sectional area of the arterial blood vessel in the blood vessel model shown in FIG. 7, and the Bramwell-Hill equation, can be expressed numerically. It is a simulated diagram. FIG. 9 is a diagram showing a state approximated by a logarithmic function shown by a broken line in the theoretical relationship shown in FIG. 8 with the vertical and horizontal axes interchanged. It is a figure which shows the relationship between the square value of the pulse wave propagation velocity and transmural pressure actually measured using the upper arm of a goat. 10 is a diagram showing a plot of the relationship between the slope and the intercept of the six logarithmic relationship approximations in FIG. 9. FIG. In addition to the relationships between the slopes and intercepts of the eight logarithmic relationship approximations in Figure 10, we plotted the relationships between the slopes and intercepts of 15 logarithmic relationship approximations obtained in additional experiments such as one goat. FIG. FIG. 7 is a diagram showing the relationship between the slope and the intercept when the relationship between the square value of the pulse wave propagation velocity and the transmural pressure of 111 data sets obtained from 7 goats is approximated by a logarithmic function. FIG. 3 is a diagram showing the relationship between the slope and the intercept when the relationship between the square value of the pulse wave propagation velocity and the transmural pressure of 90 data sets obtained from 30 people is approximated by a logarithmic function. Diastolic blood pressure DAP estimated by formula (5) from actually measured pulse wave velocity PWV and compression pressure Pc for 30 people, and diastolic blood pressure measured by blood pressure measurement using the Korotkoff sound auscultation method. It is a figure showing correlation with DAP. 6 is a flowchart illustrating a main part of the control operation of the electronic control device 70 of FIG. 5, and shows control for setting a diastolic blood pressure estimation formula and calculating and estimating the diastolic blood pressure. 17 is a flowchart illustrating a main part of the control operation of the electronic control device 70 of FIG. 5, and shows the diastolic blood pressure estimation formula setting routine of FIG. 16. 17 is a flowchart illustrating a main part of the control operation of the electronic control device 70 of FIG. 5, and shows the diastolic blood pressure estimation routine of FIG. 16. 6 is a flowchart illustrating a main part of the control operation of the electronic control device 70 of FIG. 5, and shows blood pressure monitoring control. 7 is a time chart illustrating another control operation of the electronic control device 70 of FIG. 5, and is a diagram corresponding to FIG. 6. FIG. FIG. 6 is a diagram illustrating a change in the shape of a pulse wave in the process of lowering the compression pressure by the compression pressure control unit in FIG. 5;

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Note that in the following examples, the figures are simplified or modified as appropriate, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

FIG. 1 shows an example of blood pressure measurement according to the present invention, which is equipped with a compression band 12 for the upper arm, which is wrapped around an arm or an ankle of a living body 14, which is a person to be measured, at a compressed site such as an upper arm 16. A device (diastolic blood pressure estimating device) 10 is shown. This blood pressure measuring device 10 detects the pressure generated in response to a change in the volume of the arterial blood vessel 18 in the process of lowering the compression pressure Pc of the compression band 12, which has been increased to a value sufficient to occlude the arterial blood vessel 18 in the upper arm 16. A pulse wave (volume pulse wave), which is a pressure vibration of the compression pressure Pc in the compression band 12, is sequentially extracted, and the systolic blood pressure value SAP and diastolic blood pressure value DAP of the living body 14 are determined based on information obtained from the pulse wave. It is used to measure.

FIG. 2 is a diagram showing the compression band 12 with a part of the outer peripheral side nonwoven fabric 20a cut away. As shown in FIG. 2, the compression band 12 includes a band-shaped outer bag 20 made of an outer peripheral side non-woven fabric 20a and an inner peripheral side non-woven fabric 20b made of synthetic resin fibers whose back surfaces are mutually laminated with synthetic resin such as PVC (polyvinyl chloride). , an upstream inflation bag 22 and an intermediate inflation bag which are housed sequentially in the width direction within the belt-shaped outer bag 20 and are made of a flexible sheet such as a soft polyvinyl chloride sheet and can independently compress the upper arm 16. 24, and a downstream expansion bag 26. This compression band 12 can be attached to and detached from the upper arm 16 by attaching and detaching a raised pile 28b attached to the end of the inner circumferential side nonwoven fabric 20b to a hook and loop fastener 28a attached to the end of the outer circumferential side nonwoven fabric 20a. It is designed so that it can be installed.

The upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26 each have independent air chambers that are connected in the width direction of the longitudinal compression band 12 and compress the upper arm 16, and each have a tube connection connector. 32, 34 and 36 are provided on the outer peripheral surface side. These tube connectors 32, 34, and 36 are exposed on the outer circumferential surface of the compression band 12 through the outer circumferential side nonwoven fabric 20a.

FIG. 3 is a plan view showing the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 provided in the compression band 12, and FIG. 4 is a sectional view taken along the line IV-IV in FIG. . The upstream expansion bag 22, the intermediate expansion bag 24, and the downstream expansion bag 26 are for detecting pulse waves, which are pressure vibrations generated in response to changes in the volume of the arterial blood vessel 18 compressed by them. Each of them is elongated. The upstream expansion bag 22 and the downstream expansion bag 26 are arranged adjacent to both sides of the intermediate expansion bag 24, and the intermediate expansion bag 24 is sandwiched between the upstream expansion bag 22 and the downstream expansion bag 26. It is disposed at the center of the compression band 12 in the width direction. The center of the upstream expansion bag 22 and the center of the intermediate expansion bag 24 are separated by a distance L12, and the center of the upstream expansion bag 22 and the center of the downstream expansion bag 26 are separated by a distance L13. Note that when the compression band 12 is wrapped around the upper arm 16, the upstream inflation bag 22 and the downstream inflation bag 26 are positioned at a predetermined distance in the longitudinal direction of the upper arm 16, and the intermediate inflation bag 24 is It is arranged between the upstream inflation bag 22 and the downstream inflation bag 26 so as to be continuous in the longitudinal direction of the upper arm 16.

The intermediate expansion bag 24 has side edges with a so-called gusset structure on both sides. That is, at both ends of the intermediate inflatable bag 24 in the longitudinal direction of the upper arm 16, that is, in the width direction of the compression band 12, there are a pair of flexible sheets that are folded in the direction toward each other so that the closer they are to each other, the deeper the sheet. Folding grooves 24f and 24g are formed, respectively. Ends 22a and 26a of the upstream expansion bag 22 and the downstream expansion bag 26 adjacent to the intermediate expansion bag 24 are inserted into the pair of folding grooves 24f and 24g, respectively. . As a result, the end 24a of the intermediate inflation bag 24 and the end 22a of the upstream inflation bag 22 are overlapped with each other, and the end 24b of the intermediate inflation bag 24 and the end 26a of the downstream inflation bag 26 are overlapped with each other. Since they have a mutually stacked structure, that is, an overlapping structure, when the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 press the upper arm 16 with equal pressure, the pressure is also equal near their boundaries. distribution is obtained.

The upstream inflation bag 22 and the downstream inflation bag 26 also have side edges of a gusset structure at ends 22b and 26b on the opposite side from the intermediate inflation bag 24. That is, at the end 22b of the upstream inflation bag 22 opposite to the intermediate inflation bag 24, there is a folding groove 22f made of flexible sheets that is folded in the direction toward each other so that the closer they are to each other, the deeper the folding groove 22f is. It is formed. In addition, at the end 26b of the downstream inflation bag 26 opposite to the intermediate inflation bag 24, there is a folding groove 26g made of flexible sheets folded in the direction toward each other so that the closer they are to each other, the deeper the groove is. It is formed. In order to prevent the compression band 12 from protruding in the width direction, the sheet forming the folding groove 22f is inserted into the opposite side, that is, the intermediate inflation bag 24, through a connecting sheet 38 having a through hole arranged in the upstream inflation bag 22. connected to the side part. Similarly, the sheet constituting the folding groove 26g is connected to the opposite side, that is, the intermediate expansion bag 24 side, via a connection sheet 40 provided with a through hole arranged in the downstream expansion bag 26.

As a result, the compression pressure Pc against the arterial blood vessel 18 of the upper arm 16 can be obtained at the ends 22b and 26b of the upstream inflation bag 22 and the downstream inflation bladder 26 in the same way as in other parts, so that the compression pressure Pc in the width direction of the compression band 12 is The effective compression width becomes equal to the width dimension. The width direction of the compression band 12 is about 12 cm, and since the three upstream inflation bags 22, the intermediate inflation bag 24, and the downstream inflation bladder 26 are arranged in the width direction, each of them is substantially 4 cm. It has no choice but to have a width dimension of approximately In order to sufficiently generate the compression function even with such a narrow width dimension, both ends 24a and 24b of the intermediate inflation bag 24, the end 22a of the upstream inflation bag 22, and the end 26a of the downstream inflation bag 26 are are overlapped with each other, and the ends 22b and 26b of the upstream expansion bag 22 and the downstream expansion bag 26 on the opposite side from the intermediate expansion bag 24 are the side edges of a so-called gusset structure. has been done.

Between the ends 22a and 26a of the upstream expansion bag 22 and the downstream expansion bag 26 on the intermediate expansion bag 24 side and the inner wall surfaces of the pair of folding grooves 24f and 24g into which they are inserted, that is, the opposing groove side surfaces. are interposed respectively with longitudinal shielding members 42n and 42m having stiffness anisotropy in which the bending stiffness in the width direction of the compression band 12 is higher than the bending stiffness in the longitudinal direction of the compression band 12. The shielding member 42n has a length similar to the overlapping dimension of the upstream inflation bag 22 and the intermediate inflation bag 24. Similarly, the shielding member 42m has a length similar to the overlapping dimension of the downstream expansion bag 26 and the intermediate expansion bag 24.

As shown in FIGS. 3 and 4, the outer circumference of the gap between the end 22a of the upstream expansion bag 22 and the folding groove 24f into which it is inserted, and the gap between the downstream expansion bag 26 Longitudinal shielding members 42n and 42m are respectively interposed in the outer peripheral side of the gap between the end portion 26a and the folding groove 24g into which it is inserted. In this embodiment, the shielding effect is greater in the gap on the outer circumference side than in the gap on the inner circumference side, so the longitudinal shielding members 42n and 42m are provided in the gap on the outer circumference side. and the gap on the inner peripheral side.

The shielding members 42n and 42m are arranged so that the plurality of flexible hollow tubes 44 made of resin are parallel to each other in the longitudinal direction of the upper arm 16 (that is, the width direction of the compression band 12), and In other words, the flexible hollow tubes 44 are arranged in series (in the longitudinal direction of the compression band 12), and the flexible hollow tubes 44 are connected directly by molding or adhesive, or indirectly through another member such as a flexible sheet such as an adhesive tape. It is constructed by interconnecting each other. The shielding member 42n is hung on a plurality of hanging sheets 46 provided at a plurality of locations on the outer circumferential side of the end 22a of the upstream inflation bag 22 on the intermediate inflation bag 24 side. Similarly, the shielding member 42m is hung on a plurality of hanging sheets 46 provided at a plurality of locations on the outer circumferential side of the end 26a of the downstream inflation bag 26 on the intermediate inflation bag 24 side.

Returning to FIG. 1, in the blood pressure measuring device 10, an air pump 50, a rapid exhaust valve 52, and an exhaust control valve 54 are each connected to a main pipe 56. From the main pipe 56, there is a first branch pipe 58 connected to the upstream expansion bag 22, a second branch pipe 62 connected to the intermediate expansion bag 24, and a third branch pipe connected to the downstream expansion bag 26. The tubes 64 are each branched. The first branch pipe 58 includes a first on-off valve E1 for directly opening and closing between the air pump 50 and the upstream expansion bag 22. The second branch pipe 62 includes a second on-off valve E2 for directly opening and closing between the air pump 50 and the intermediate expansion bag 24. The third branch pipe 64 includes a third on-off valve E3 for directly opening and closing between the air pump 50 and the downstream expansion bag 26.

A first pressure sensor T1 for detecting the pressure value inside the upstream expansion bag 22 is connected to the first branch pipe 58, and a first pressure sensor T1 for detecting the pressure value inside the intermediate expansion bag 24 is connected to the second branch pipe 62. A second pressure sensor T2 is connected to the third branch pipe 64, a third pressure sensor T3 is connected to the third branch pipe 64, and a third pressure sensor T3 is connected to the main pipe 56, for detecting the pressure value inside the downstream inflation bag 26. A fourth pressure sensor T4 for detecting twelve compression pressures Pc is connected.

The electronic control device 70 is supplied with an output signal indicating the pressure value inside the upstream inflation bag 22, that is, the compression pressure Pc1 of the upstream inflation bag 22, from the first pressure sensor T1, and an output signal indicating the pressure value Pc1 of the upstream inflation bag 22 from the second pressure sensor T2. An output signal indicating the pressure value within the downstream inflation bag 26, that is, the compression pressure Pc2 of the intermediate inflation bag 24 is supplied from the third pressure sensor T3, and an output signal indicating the pressure value within the downstream inflation bladder 26, that is, the compression pressure Pc3 of the downstream inflation bladder 26. is supplied, and an output signal indicating the compression pressure Pc of the compression band 12 is supplied from the fourth pressure sensor T4.

The electronic control device 70 is a so-called microcomputer including a CPU 72, a RAM 74, a ROM 76, a display device 78, an I/O port (not shown), and the like. This electronic control device 70 processes an input signal in accordance with a program stored in advance in a ROM 76 while a CPU 72 utilizes a memory function of a RAM 74, and in response to an operation of a blood pressure estimation start operation button 80, an electric air pump is activated. 50, by controlling the rapid exhaust valve 52, the exhaust control valve 54, the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3, automatic blood pressure measurement control is executed, and the measurement results are displayed on the display device. 78. FIG. 6 shows changes in the compression pressure Pc of the compression band 12 controlled by the compression pressure control section 86 of the electronic control device 70.

(Explanation of diastolic blood pressure estimation algorithm)
In the following, a diastolic blood pressure estimation algorithm executed by the functions of the electronic control unit 70 of FIG. 5 will be described.

FIG. 7 shows a model of the arterial blood vessel 18 showing the relationship between the transmural pressure Pt and the cross-sectional area A of the arterial blood vessel 18. As the trans-wall pressure Pt increases, the cross-sectional area A increases exponentially toward the saturation value Am, and when the trans-wall pressure Pt is zero, it shows the Ao value. The characteristic showing the relationship between the transmural pressure Pt of the arterial blood vessel 18 and the cross-sectional area A of the arterial blood vessel 18 in FIG. 7 is expressed by the following blood vessel model equation. The transmural pressure Pt is the value obtained by subtracting the external arterial pressure, that is, the compression pressure (cuff pressure) Pc from the intraarterial pressure AP (AP - Pc). It is the value obtained by subtracting the compression pressure Pc from (DAP-Pc). Formula (a1) is described in Non-Patent Document 3. In formula (a1), b is an index related to blood vessel hardness (compliance or elastic modulus).
A=Am+(Ao-Am)e^(-b・Pt)... (a1)

The theoretical nonlinear exponential curve equation (1) obtained by applying the Bramwell-Hill equation to this blood vessel model equation (a1) is the It is very similar to an exponential function curve showing the relationship with the multiplicative value PWV ² . The relationship shown by exchanging the horizontal and vertical axes of the exponential function curve becomes a logarithmic function, and the logarithmic function approximation curve that can be approximated with high accuracy to the logarithmic function is the constant b and the cross-sectional area ratio Ao It can be converted into linear regression equation (2) that does not depend on /Am. Since the transmural pressure Pt of the arterial blood vessel 18 at the time of diastolic blood pressure is (estimated diastolic blood pressure DAPe - compression pressure Pc), the relationship between the transmural pressure Pt of the artery and the square value of the pulse wave velocity PWV ² is expressed as follows: The linear regression equation (2) expressed can be transformed as shown in equation (3) regarding the trans-wall pressure Pt. Since the slope α of Equation (3) is the same as Equation (2), the slope α can be obtained by regression analysis between the plurality of actually measured compression pressures Pc and the square value PWV ² of the pulse wave propagation velocity. The intercept β is obtained by substituting the slope α into the predetermined linear relationship (4) between the predetermined slope α and the intercept β. When the slope α and the intercept β are determined in this way, the diastolic blood pressure DAPe is expressed by the diastolic blood pressure estimation formula (5), which is a modification of the formula (3) for the transmural pressure Pt. From this diastolic blood pressure value estimation formula (5), the diastolic blood pressure value DAPe is estimated based on the square value PWV ² of the actual pulse wave propagation velocity and the compression pressure Pc.

PWV ² = (1/ρ・b) (1/(1-Ao/Am))・e^(b・Pt)
-(1/ρ・b) ... (1)

This nonlinear exponential function equation (1) is the equation (a1) showing the relationship between the transmural pressure Pt (=DAP-Pc) at the diastolic blood pressure of the arterial blood vessel 18 and the cross-sectional area A of the arterial blood vessel 18 shown in FIG. It is based on ρ in equation (1) represents blood density.

The following new blood vessel model equation (a2) is obtained by differentiating both sides of this equation (a1) with respect to Pt, the well-known Bramwell-Hill equation (a3), and the differential equation regarding the cross-sectional area A of the volume V of the arterial blood vessel 18 When the three equations are summarized using (a4), the following equation (a5) is obtained. L in equation (a4) represents the effective length of the arterial blood vessel 18 in the upper arm.
dA/dPt=-b(Ao-Am)e^(-b・Pt)... (a2)
PWV ² = (dPt/ρ)・(V/dV) ... (a3)
dV=dA・L... (a4)
PWV ² = (1/ρb) (1/(1-Ao/Am))・e^(b・Pt)
-(1/ρb) ... (a5)

In this formula (a5), the variable related to the cross-sectional area A is the ratio Ao/Am of the saturation value Am of the cross-sectional area A to the cross-sectional area Ao when the trans-wall pressure Pt is zero, so the formula (a5) The relationship between PWV ² and Pt is not affected by the absolute value of the cross-sectional area A of the arterial blood vessel 18. In other words, it is considered that it is not affected by the physique of each living organism. The relationship in equation (a5) depends on the cross-sectional area ratio Ao/Am of the arterial blood vessel 18 and the constant b related to the hardness of the arterial blood vessel 18.

In previous research, there is a report that b = 0.03, Ao/Am = 0.25, so hypothetically, b = 0.03, 0.06, 0.09, Ao/Am = 0.25, When the relationship of equation (a5) is numerically simulated with 0.5, the result is as shown in FIG.

In order to consider the relationship between constant b and cross-sectional area ratio Ao/Am, if both sides of equation (a2) are made reciprocals, equation (a6) is obtained. In this formula (a6), it is shown that as the constant b becomes larger, dPt/dA, that is, the elastic modulus becomes larger within a predetermined range for a predetermined transwall pressure Pt.
dPt/dA=e^(b・Pt)/b(Am-Ao)... (a6)

The present inventors attached the above-mentioned compression band 12 to the front leg (upper arm) of a goat whose blood pressure value was changed using a drug for each measurement, and at each pressure step by the compression band 12, the compression pressure Pc and An experiment was conducted to obtain the pulse wave propagation velocity PWV based on the time difference between the pulse wave obtained from the expansion bag 22 and the pulse wave obtained from the downstream expansion bag 26. At this time, the relationship between the obtained square value PWV ² of the pulse wave propagation velocity PWV and the transmural pressure Pt was extremely similar to that shown in FIG.

The theoretical relationship shown in FIG. 8 above becomes the relationship shown in FIG. 9 when the vertical and horizontal axes are interchanged, and can be approximated to the logarithmic function shown by the broken line, regardless of the constant b or the cross-sectional area ratio Ao/Am of the arterial blood vessel 18. . The coefficient of determination R ² of this logarithmic function approximation curve is 0.97-0.99, and it can be approximated with high accuracy. The relationship shown in FIG. 10 was also obtained in the relationship between the square value PWV ² of the pulse wave propagation velocity PWV and the transmural pressure Pt obtained using the goat. In the bold line in FIG. 10, the coefficient of determination ^R2 is 0.9615, which allows for high accuracy approximation. The average value of the coefficient of determination of all 23 logarithmic function approximation curves was 0.91±0.11, and very good logarithmic function approximation curves were obtained. Such a logarithmic function approximation curve can be obtained by linear regression linear equation (2) converted into a linear form by considering the independent variable as the logarithm (ln(PWV ² )) of the square value PWV ² of the pulse wave propagation velocity PWV. Represented by The same applies to humans.
Pt=α・ln(PWV ² )+β... (2)

Here, the slope α of the logarithmic function approximation curve as shown in FIG. 10 is mathematically equivalent to the slope of the linear regression line of ln(PWV ² ) and -Pc. By substituting transwall pressure Pt=DAP-Pc into the left side of equation (2), it can be converted into equation (3) of the following linear regression line -Pc. In this way, the equation (3) of the linear regression line −Pc converted from the equation (2) of the linear regression line Pt, that is, the conversion equation (3), calculates the measurable pulse wave propagation velocity PWV and the pulse wave propagation velocity PWV. can be obtained as a linear regression line of multiple data points each representing the compression pressure Pc during actual measurement, and by finding the slope of the obtained linear regression line, the above-mentioned slope α can be calculated for each subject. It is.
-Pc=α・ln(PWV ² )+(β-DAP)... (3)

When the relationship between the slope α and the intercept β of the six logarithmic functions in FIG. 9 is plotted using six data points indicating the slope α and the intercept β, it is represented by the regression line shown by the broken line in FIG. 11. This result shows that even if the index b related to vascular hardness and the cross-sectional area ratio Ao/Am of the arterial blood vessel 18, which are constants specific to biological conditions, are varied over a wide range, the slope α and the intercept β of the logarithmic function are linearly correlated. It can be said that this has been confirmed theoretically and analytically. Similarly, when plotting the relationship between the slope α and the intercept β of the 23 logarithmic functions obtained from the experiment using the goat upper arm shown in Figure 10, it is clear that there is a linear correlation as shown in Figure 12. It became. As a result, when the relationship between PWV ² and Pt is approximated by a logarithmic function, if the mutual linear correlation between the slope α and the intercept β can be stably obtained regardless of the state of the living body, then the intercept β of the logarithmic function It is thought that it can be used for estimating

Therefore, using experimental data using the upper arms of seven goats, the linear relationship between the slope α and the intercept β when the relationship between PWV ² and Pt of 111 data sets is approximated by a logarithmic function is shown in the figure. 13. The numbers shown on the right side of FIG. 13 are the individual identification numbers of the seven goats. In FIG. 13, when y is β and x is α in the above linear relationship, the linear regression line is y=-1.921x+11.4, as shown by the broken line in FIG. The coefficient of determination ^R2 of the straight line was 0.86. Further, FIG. 14 shows the linear relationship between the slope α and the intercept β when the relationship between PWV ² and Pt of 90 data points obtained from 30 people is approximated by a logarithmic function. The linear regression line shown by the broken line in FIG. 14 was y=-3.6137x+14.833, and the coefficient of determination R ² of this linear regression line was 0.7071. As is clear from FIGS. 13 and 14, the approximation can be made using substantially the same linear relationship regardless of the individual living organisms, and the following linear relationship equation (4) was experimentally obtained. A linear relational expression (4) indicating a certain relation between the slope α and the intercept β is previously determined and stored in a linear relational storage unit 84, which will be described later. The slope γ of linear relational expression (4) is, for example, −3.6137, and the intercept δ is, for example, 14.833.
β=γ・α+δ... (4)

Assuming that the relationship between the square value PWV ² of the pulse wave velocity PWV and the transmural pressure Pt is approximately stable and can be approximated by equation (2) regardless of the condition of the individual living body, as described above, Calculate the intercept β by substituting the slope α calculated from equation (2) or its modified form (3) based on the compression pressure Pc and pulse wave velocity PWV actually measured in the linear relational equation (4). can do. By transforming equation (3), the following diastolic blood pressure estimation equation (5) is obtained. Therefore, by substituting the obtained slope α and intercept β, the actually measured PWV and the compression pressure Pc at the time of the actual measurement into this diastolic blood pressure estimation formula (5), the diastolic blood pressure estimated value DAPe can be obtained.
DAPe=α・ln(PWV ² )+(β+Pc)...(5)

FIG. 15 shows the diastolic blood pressure value DAPe estimated by equation (5) from the actually measured pulse wave velocity PWV and compression pressure Pc, and the blood pressure measured by the Korotkoff auscultation method for 30 people. The correlation between diastolic blood pressure and DAP is shown. At this time, the linear regression line passing through the 90 data points was y=1.0094x-1.2482, as shown by the solid line in FIG. 15, and the coefficient of determination R ² of this linear regression line was 0.6416.

Returning to FIG. 5, FIG. 5 is a functional block diagram for explaining main parts of the control functions provided in the electronic control device 70. In FIG. 5, the electronic control device 70 includes a linear regression straight line storage section 82, a linear relationship storage section 84, a compression pressure control section 86, a pulse wave extraction section 88, a pulse wave velocity calculation section 90, a unique relationship generation section 94, a blood pressure It functionally includes an estimation section 102 and a blood pressure fluctuation determination section 108.

The linear regression line storage unit 82 stores in advance the equation (3) of the linear regression line −Pc converted from the equation (2) of the linear regression line Pt, that is, the conversion equation (3). Furthermore, the linear relationship storage unit 84 stores in advance a linear relationship equation (4) between the slope α and the intercept β, in which a constant slope γ and an intercept δ obtained empirically and experimentally are set. .

In response to the operation of the blood pressure estimation start operation button 80, the compression pressure control unit 86 first calculates the actual pulse wave propagation velocity PWV for each of a plurality of compression pressures Pc around the diastolic blood pressure DAP within the compression pressure Pc decreasing period. In order to obtain the biological 14 The compression pressure Pc of the compression band 12 against the living body 14 is rapidly increased until it reaches a pressure upper limit value PCM that is set in advance to a pressure sufficiently higher than the systolic blood pressure value SAP, for example, 180 mmHg.

Next, the compression pressure control unit 86 repeatedly opens the exhaust control valve 54 at a predetermined period for a predetermined period, so that the compression pressure Pc of the compression cuff 12 is sufficiently lower than the diastolic blood pressure value DAP of the living body 14, for example. Multiple constant step pressures P1, P2, P3,...Px are maintained sequentially at preset steps of about 2 to 5 mmHg until reaching the lower limit of reduced pressure PCE, which is preset to about 40 to 60 mmHg. As shown in FIG. Rapidly lower blood pressure. The compression pressure Pc of the compression band 12 controlled in this way is such that the upstream expansion bag 22, intermediate expansion bag 24, and downstream expansion bag 26 compress the living body 14 with the same compression pressure Pc, but in FIG. The compression pressure Pc of the compression band 12 detected by the fourth pressure sensor is shown.

After the diastolic blood pressure estimation formula (5) described above is generated by the unique relationship generation unit 94 (described later), the compression pressure control unit 86 controls the diastolic blood pressure of the living body 14 in response to the blood pressure monitoring start operation. In order to monitor the value, the compression pressure Pc is preferably maintained at a pressure sufficiently lower than the diastolic blood pressure value DAP of the living body 14, for example, at a monitoring maintenance pressure PcHm set within the range of 20 to 60 mmHg. Control the compression pressure Pc. The monitoring maintenance pressure PcHm is set to a value as low as possible within a range in which the pulse wave included in the compression pressure Pc of the compression band 12 can be reliably obtained.

When the monitor pressure maintenance period ends, the compression pressure control unit 86 uses the rapid exhaust valve 52 to exhaust the pressures in the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 to atmospheric pressure. Press.

The pulse wave extractor 88 outputs an output signal indicating the compression pressure Pc1 in the upstream inflation bag 22 from the first pressure sensor T1 and a downstream signal from the third pressure sensor T3 in the section where the compression pressure Pc is maintained. A pair of pulse waves MW1 and MW3 are respectively extracted from the output signal indicating the compression pressure Pc3 in the expansion bag 26 through a pulse wave discrimination band-pass filter of 0.5 Hz to 20 Hz, and are stored. The pair of pulse waves MW1 and pulse waves MW3 are pressure oscillation waves that are generated in synchronization with the pulse that is superimposed on the compression pressure Pc. The pulse wave extraction unit 88 stores the pulse wave MW1, the pulse wave MW3, and the compression pressure Pc at the time when they are generated in association with each other.

The pulse wave velocity calculation unit 90 calculates the time difference Δt between the rising points or the peak points of the pair of pulse waves MW1 and MW3 obtained while the compression pressure Pc is maintained, and the upstream expansion bag 22 and the downstream side. Based on the known distance L13 between the side inflation bags 26, the pulse wave propagation velocity PWV (=L13/Δt) is calculated every time a pulse wave occurs at each of a plurality of preset step pressures. The above-mentioned plurality of preset step pressures are the pressure values (average These are a predetermined number (for example, six) of consecutive step pressures from a pressure value (diastolic blood pressure equivalent value) calculated from a step pressure having an amplitude of a predetermined proportion of the maximum amplitude value based on the blood pressure equivalent value). Alternatively, the above-mentioned plurality of preset step pressures may be a predetermined step pressure from which the amplitude of the pulse wave extracted by the pulse wave extraction unit 88 shows the maximum value as the compression pressure Pc of the compression cuff 12 decreases. This is a predetermined number (for example, six) of consecutive step pressures after passing through several (for example, two) step pressures.

The pulse wave propagation velocity calculation unit 90 calculates the time difference Δt between the rising points or the peak points of the pair of pulse waves MW1 and MW3 obtained in a state where the compression pressure Pc is maintained for each of the predetermined number of step pressures. and the known distance L13 between the upstream expansion bag 22 and the downstream expansion bag 26, the pulse wave propagation velocity PWV (=L13/Δt) calculated each time a pulse wave occurs, and the step when the pulse wave occurs. A set of data including pressure, that is, compression pressure Pc, is stored for each predetermined number of steps.

Note that the average value of cuff pressures Pc corresponding to the rising points of a plurality of pulse waves within a step may be used as the compression pressure Pc for each step pressure. In addition, as the pulse wave propagation velocity PWV, in two-dimensional coordinates where the horizontal axis is the time difference between the rising points of a pair of pulse waves and the vertical axis is the distance between the inflation bags, the upstream expansion bag 22 is taken as a reference. The known distance L12 between the bag 22 and the intermediate inflation bag 24 and the time difference Δt1 between the pulse wave rise points, and the known distance L13 between the upstream expansion bag 22 and the downstream expansion bag 26 and the time difference Δt3 between the pulse wave rise points. Pulse wave propagation velocity PWV obtained from linear regression and the slope of the regression line may be used.

The unique relationship generation section 94 includes a slope α calculation section 96, an intercept β calculation section 98, and a diastolic blood pressure estimation formula setting section 100.

The inclination α calculation unit 96 calculates the pulse wave propagation velocity PWV stored for each of the predetermined number (for example, six) of step pressures in the two-dimensional coordinates of the axis representing ln(PWV ² ) and the axis representing −Pc. The linearity of 6 measured data points showing 6 sets of measured data of the logarithm ln (PWV ² ) of the square value of (=L13/Δt) and the step pressure, that is, the compression pressure Pc when the pulse wave occurs. By performing regression analysis, the coefficient value of the first term on the right side of equation (3) of the linear regression line -Pc is determined as the slope α.

The intercept β calculation unit 98 calculates the intercept β based on the slope α calculated by the slope α calculation unit 96 from the linear relational expression (4). That is, the intercept β is calculated by substituting the slope α calculated by the slope α calculation unit 96 into the linear relational expression (4).

The diastolic blood pressure estimation formula setting unit 100 converts the slope α calculated by the slope α calculation unit 96 and the intercept β calculated by the intercept β calculation unit 98 into the equation (5) converted from the linear regression linear equation (2). A diastolic blood pressure estimation formula (5) reflecting the unique relationship of the living body is set and stored.

The blood pressure estimating unit 102 includes a diastolic blood pressure estimating unit 104 that performs blood pressure estimation, for example, in the interval in which the compression pressure is increased or decreased from time t2 to t11 in FIG. 6, or in the monitoring interval in which the monitor pressure PcHm is maintained after tm1. It is equipped with. The diastolic blood pressure estimating unit 104 calculates the diastolic blood pressure by substituting the pulse wave velocity PWV and the compression pressure Pc actually measured at a predetermined period of, for example, one pulse cycle to ten or more pulse cycles into the diastolic blood pressure estimation formula (5). The estimated blood pressure value DAPe is repeatedly calculated. A moving average value of the calculated diastolic blood pressure values DAPe may be calculated. The diastolic blood pressure estimating unit 104 causes the display device 78 to display the calculated diastolic blood pressure estimated value DAPe in chronological order.

The blood pressure fluctuation determining unit 108 determines based on the fact that the change in pulse wave velocity PWV deviates from the preset fluctuation determination range PWV1 to PWVh in the monitoring period in which the monitored pressure PcHm is maintained after time tm1 in FIG. Alternatively, the occurrence of a blood pressure change in a living body is determined based on the fact that a change in the estimated diastolic blood pressure value DAPe deviates from a preset fluctuation determination range DAPe1 to DAPeh, and the occurrence of a blood pressure change in the living body is determined. is displayed on the display device 78.

16, FIG. 17, FIG. 18, and FIG. 19 are flowcharts illustrating main parts of the control operation of the electronic control device 70. FIG. 16 shows control for setting a diastolic blood pressure estimation formula and collecting actual measurement data for calculating and estimating diastolic blood pressure, FIG. 17 shows a diastolic blood pressure estimation formula setting routine of FIG. 16, and FIG. shows the diastolic blood pressure estimation routine in FIG. 16, and FIG. 19 shows blood pressure monitoring control.

When the operation button 80 that starts setting the diastolic blood pressure estimation formula is turned on, in step S1 corresponding to the compression pressure control section 86 (hereinafter, "step" is omitted), the compression pressure Pc of the compression cuff 12 is increased. be done. Specifically, as shown in FIG. 6, the quick exhaust valve 52 and the exhaust control valve 54 are closed, the air pump 50 is activated, and the compressed air pumped from the air pump 50 is used to discharge the main air. The pressure within the piping 56 and the upstream inflation bladder 22, intermediate inflation bladder 24, and downstream inflation bladder 26 connected thereto is rapidly increased, and compression of the upper arm 16 by the compression band 12 is started.

Next, in S2 corresponding to the compression pressure control unit 86, based on the output signal of the fourth pressure sensor T4 indicating the compression pressure Pc of the compression band 12, the compression pressure Pc is preset to a value equal to or higher than the systolic blood pressure of the living body. It is determined whether or not the boost target pressure value PCM (for example, 180 mmHg) is equal to or higher than the boost target pressure value PCM (for example, 180 mmHg). At a time point before time t2 in FIG. 6, the determination in S2 is negative, and steps S1 and subsequent steps in FIG. 16 are repeatedly executed.

When the compression pressure Pc reaches the increased target pressure value PCM and the determination in S2 is affirmed, the operation of the air pump 50 is stopped in S3 corresponding to the compression pressure control section 86, and the compression pressure Pc of the compression band 12 is increased. , Exhaust control is performed so that the exhaust gas is slowly exhausted with step pressure reductions that are sequentially formed at a constant cycle, such as constant step pressures P1, P2, P3, ... Px, which are preset in advance every 2 to 5 mmHg/sec, for example. The valve 54, the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3 are operated. When maintaining the step pressures P1, P2, P3, . . . Px, the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3 are each closed. Time t2 in FIG. 6 is the start point of the slow evacuation, and time t3 to t4 is the period during which the compression pressure Pc of the compression band 12 is maintained at the step pressure P1 for a predetermined period of time, for example, while two beats occur. It is.

Next, in S4 corresponding to the pulse wave extraction section 88, pulse waves are extracted in sections where the compression pressures P1, P2, P3, . . . Px are each maintained for a predetermined time. That is, pulse wave sampling band-pass filter processing is performed to discriminate signals in a wavelength band of, for example, 0.5 Hz to less than 20 Hz with respect to the output signals from the first pressure sensor T1, the second pressure sensor T2, and the third pressure sensor T3. As a result, pulse wave signals MW1, MW2, and MW3 representing pulse waves from the upstream expansion bag 22, intermediate expansion bag 24, and downstream expansion bag 26 are extracted, and pulse wave signals MW1, MW2, and MW3 representing pulse waves from the fourth pressure sensor T4 are The compression pressure Pc of the compression band 12 from which the alternating current component has been removed is extracted by performing low-pass filter processing on the output signal in a wavelength band of less than several Hz, for example. This compression pressure Pc represents the step pressure at that time, and the pulse wave signals MW1, MW2, and MW3 are sequentially stored for each step together with the compression pressure Pc at that time. In each step, a plurality of pulse wave signals MW1, MW2, and MW3 are stored.

In S5 corresponding to the compression pressure control section 86, it is determined whether the compression pressure Pc is equal to or less than a preset measurement end pressure value PCE (for example, 60 mmHg). If the determination in S5 is negative, that is, before t11 in FIG. 6, the determination in S5 is negative and steps S3 and subsequent steps are repeatedly executed. If the determination in S5 is affirmative, rapid exhaust is started in S6 at time t11.

Next, in S7 corresponding to the pulse wave velocity calculating section 90 or the pulse wave velocity measuring step, the amplitude of the pulse wave extracted by the pulse wave extracting section 88 reaches the maximum value as the compression pressure Pc of the compression cuff 12 decreases. Based on the pressure value of the step pressure (value equivalent to mean blood pressure) indicating the step pressure, a continuous plurality (for example, 6 A predetermined number (for example, two) of the step pressures at which the amplitude of the pulse wave extracted by the pulse wave extraction unit 88 shows the maximum value at the step pressure of The time difference Δt between the rise points or the peak points of the pair of pulse waves MW1 and pulse waves MW3 obtained at a plurality of consecutive (for example, six) step pressures after passing through the steps, and the upstream expansion bag 22 and the known distance L13 between the downstream expansion bags 26, the pulse wave propagation velocity PWV (=L13/Δt) is sequentially calculated every time a pulse wave occurs. Then, these pulse wave propagation velocities PWV were converted to the logarithm ln (PWV ² ) of the square value, and used to calculate the logarithm ln (PWV ² ) of the square value and the pulse wave propagation velocity PWV at that time. A set of actual measurement data [ln (PWV ² ), Pc] is formed with the compression pressure Pc when the pulse wave is generated, and each set of actual measurement data [ln (PWV ^{1 2} ), Pc1]...[ln(PWVn ² ), Pcn] are stored.

Next, in S8 corresponding to the unique relationship generation section 94 or the unique relationship generation step, a diastolic blood pressure estimation formula setting routine shown in FIG. 17 is started. In FIG. 17, the slope α calculation unit 96 or S81 corresponding to the slope calculation process calculates a plurality of sets (six sets in this example) of actually measured data [ln(PWV1 ² ), Pc1]...[ln(PWVn ² ), Pcn], the coefficient value of the first term on the right side of equation (3) of the linear regression line -Pc is obtained as the slope α.

Next, in the intercept β calculation section 98 or S82 corresponding to the intercept calculation step, by substituting the slope α calculated in S81 into x of the linear relational expression (4) stored in advance in the linear relation storage section 84, y, that is, the intercept β is calculated.

In the diastolic blood pressure estimation formula setting unit 100 or in S83 corresponding to the diastolic blood pressure estimation formula setting step, the slope α calculated in S81 and the intercept β calculated in S82 are substituted into the diastolic blood pressure estimation formula (5). By doing so, a diastolic blood pressure estimation formula is created that reflects the unique relationship of the living body from which the actual measurement data was obtained, between the diastolic blood pressure DAPe, the pulse wave velocity PWV, and the compression pressure Pc when it was obtained. (5) is set and stored.

Then, in S9 corresponding to the diastolic blood pressure estimation unit 104 or the diastolic blood pressure estimation step, a diastolic blood pressure estimation routine shown in FIG. 18 is started. In FIG. 18, in S91, at least one set of actual measurement data among n sets of actual measurement data [ln (PWV1 ² ), Pc1] ... [ln (PWVn ² ), Pcn] is calculated using the diastolic blood pressure estimation formula ( 5), at least one diastolic blood pressure DAPe is calculated and displayed on the display device 78. In S92, when a plurality of diastolic blood pressures DAPe are calculated by substituting a plurality of sets of actual measurement data for each of a plurality of steps into the diastolic blood pressure estimation formula (5), their average value is calculated as the diastolic blood pressure. It is stored as blood pressure DAPe and displayed on display device 78.

FIG. 19 shows a blood pressure monitoring routine that is executed in response to the operation of the blood pressure monitoring mode start operation button 81 after the diastolic blood pressure estimation formula (5) is set. In FIG. 20, in S31 corresponding to the compression pressure control unit 86, a constant monitoring maintenance is performed that is preset so that the compression pressure Pc of the compression cuff 12 is below the diastolic blood pressure, for example, within a range of 20 to 60 mmHg. The pressure is controlled to be PcHm. Next, in S32 corresponding to the pulse wave extraction section 88, the signals of the compression pressure Pc1 obtained from the upstream expansion bag 22 and the compression pressure Pc3 obtained from the downstream expansion bag 26 are passed through a bandpass filter for pulse wave discrimination, and a pair of signals are extracted. Pulse wave MW1 and pulse wave MW3 are each extracted for each beat and stored sequentially. In S33 corresponding to the pulse wave propagation velocity calculation unit 90, the time difference Δt between the rising points or the peak points of the pair of pulse waves MW1 and pulse waves MW3 obtained at the monitoring maintenance pressure PcH, the upstream expansion bag 22 and From the known distance L13 between the downstream expansion bags 26, the pulse wave propagation velocity PWV (=L13/Δt) is sequentially calculated every time a pulse wave occurs.

Next, in S34 corresponding to the diastolic blood pressure estimation unit 104 and the diastolic blood pressure estimation step, the logarithm ln (PWV ² ) of the square value of the pulse wave propagation velocity PWV calculated in S33 is calculated, and the maintenance pressure for monitoring is A set of actual measurement data [ln(PWV ² ), PcHm] at PcHm is constructed. Then, by substituting the set of measured data [ln(PWV ² ), PcHm] into the diastolic blood pressure estimation formula (5), the estimated diastolic blood pressure value DAPe is calculated for each pulse wave extraction cycle or after that. It is repeatedly calculated at a cycle that is an integral multiple of the pulse wave extraction cycle. Then, in S35, the estimated diastolic blood pressure value DAPe calculated in S34 is stored and output to the display device 78.

Next, in S36, the fluctuation width of the pulse wave velocity PWV calculated in S33 is outside the preset fluctuation determination range PWVl to PWVh, or based on the diastolic blood pressure estimation calculated in S34. The occurrence of a blood pressure fluctuation of the subject is determined based on whether or not the fluctuation range of the value DAPe deviates from a preset fluctuation determination range DAPel to DAPeh. If the determination in S36 is negative, S37 is skipped and S38 and subsequent steps are executed. However, if the determination in S36 is affirmative, the occurrence of a change in the estimated diastolic blood pressure value DAPe is output to the display device 78 in S37.

Next, in S38, it is determined whether the blood pressure monitoring mode operation button 81 has been operated again. If the determination in S38 is negative, steps S31 and subsequent steps are repeatedly executed, but if the determination is affirmative, the compression cuff 12 is rapidly evacuated in S39, and the blood pressure monitoring mode is ended.

As described above, according to the blood pressure measuring device 10 of the present embodiment, the intercept β and the slope α included in the linear regression equation (2) leading to the diastolic blood pressure estimation equation (5) are shown in equation (4). As such, they have a fixed linear relationship and are not influenced by the person being measured. Therefore, the diastolic blood pressure value DAPe can be measured with high accuracy because it is not easily influenced by the individual biological characteristics of the subject. Further, there is an advantage that there is no need to perform calibration for each subject, unlike the conventional method of estimating blood pressure using pulse wave velocity PWV.

Further, according to the blood pressure measuring device 10 of the present embodiment, the preset linear regression equation representing the physical model equation of the arterial blood vessel 18 is expressed by the above equation (2). The linear regression equation (2) is the actual case in which the blood vessel cross-sectional area A is larger than zero when the transmural pressure is zero, and the blood vessel cross-sectional area A increases and becomes saturated as the transmural pressure increases. Since it is based on the physical model equation (a1) of the arterial blood vessel 18 indicating the behavior of the blood vessel and the Bramwell-Hill equation (a3), the diastolic blood pressure value DAPe can be measured with high accuracy.

Further, according to the blood pressure measuring device 10 of the present embodiment, the conversion equation from the linear regression equation (2) is expressed by equation (3). Based on the conversion formula (3), even if the diastolic blood pressure DAP and the intercept β are unknown, by linear regression analysis of the logarithm of the square of the pulse wave propagation velocity PWV obtained by actual measurement and the compression pressure Pc, , the slope α can be calculated.

Further, according to the blood pressure measuring device 10 of this embodiment, the linear relationship is expressed by equation (4). The linear relationship (4) indicates that the intercept β and slope α included in the linear regression linear equation (2) have a constant linear relationship with each other regardless of each individual, and this relationship is not influenced by the person being measured. Therefore, the diastolic blood pressure value DAPe can be measured with high accuracy without being affected by the individual biological characteristics of the subject.

Further, according to the blood pressure measurement device 10 of the present embodiment, the diastolic blood pressure estimation formula is expressed by equation (5). The diastolic blood pressure estimation formula (5) is a formula that uses two measurable compression pressure Pc and pulse wave velocity PWV as variables, so by substituting the two measured variables, A person's diastolic blood pressure DAPe can be estimated.

Further, according to the blood pressure measurement device 10 of the present embodiment, the diastolic blood pressure estimating unit 104 calculates the actual The diastolic blood pressure DAPe of the subject is estimated based on the compression pressure Pc and the pulse wave velocity PWV of the compressed area, and the average value of the diastolic blood pressure DAPe obtained for each step pressure is calculated as the diastolic blood pressure. Since it is determined as DAPe, the diastolic blood pressure value can be measured with higher accuracy.

Further, according to the blood pressure measuring device 10 of the present embodiment, the diastolic blood pressure estimating unit 104 calculates the actual diastolic blood pressure obtained at a plurality of pressures set by the compression band 12 and set lower than the diastolic blood pressure DAP of the subject. Since the diastolic blood pressure DAPe of the subject is estimated based on the compression pressure Pc and the pulse wave velocity PWV of the compressed area, the burden (stress) of compression by the compression band 12 on the subject is reduced and stable. The accuracy of blood pressure measurement can be improved by obtaining the blood pressure value.

Further, according to the blood pressure measuring device 10 of this embodiment, a pair of pulse wave sensors (a first pressure sensor T1, a third pressure sensor T3) are arranged at two positions apart from each other by a predetermined distance along the arterial blood vessel 18. ), the pulse wave can be determined from the time difference Δt between the rising points or peak points of the pair of pulse waves MW1 and MW3 respectively detected by Pulse wave propagation velocity PWV (=L13/Δt) is calculated every time . As a result, the delay time from the R wave generation point to the cardiac ejection point (pre-ejection Since there is no error in the period), the diastolic blood pressure DAPe can be estimated with high accuracy. In other words, since the pulse wave velocity PWV, which purely reflects the characteristics of the arterial blood vessels, is measured, it is not affected by fluctuations in the delay time (pre-ejection period), which also depends on the state of the heart, and the measurement Highly reproducible.

Further, according to the blood pressure measuring device 10 of the present embodiment, the compression pressure control section 86 maintains the compression pressure Pc by the compression cuff 12 at the monitor pressure PcHm lower than the diastolic blood pressure of the living body, and the monitor pressure PcHm is maintained. A diastolic blood pressure estimating unit includes a blood pressure fluctuation determination unit 108 that determines the occurrence of blood pressure fluctuation based on whether the pulse wave propagation velocity PWV measured during the period deviates from preset fluctuation determination values PWV1 to PWVh, and the diastolic blood pressure estimation unit 104 is a measurement target based on the actual compression pressure Pc and the pulse wave velocity PWV of the compressed area from the diastolic blood pressure estimation formula (5) when the occurrence of blood pressure fluctuation is determined by the blood pressure fluctuation determination unit 108. Estimate the person's diastolic blood pressure DAPe. Thereby, long-term blood pressure monitoring can be performed with less burden on the person being measured.

FIG. 20 is a time chart illustrating another control operation of the electronic control device 70, and is a diagram corresponding to FIG. 6. In this embodiment, parts common to those in the previous embodiment are given the same reference numerals and explanations will be omitted. In this embodiment, the method of setting the diastolic blood pressure estimation formula (5) is different, but the other aspects are the same.

In FIG. 20, in order to set the equation (5) for estimating the diastolic blood pressure DAPe of the living body 14 to be measured, the compression pressure control unit 86 controls the 1 maintenance period (from time tk1 to time tk2), a second maintenance period (from time tk3 to time tk4) in which the second maintenance pressure PcH2 is maintained lower than the first maintenance pressure PcH1, and a third maintenance period lower than the second maintenance pressure PcH2. After lowering the compression pressure Pc step by step so that a third maintenance section (time tk5 to time tk6) in which the pressure PcH3 is maintained is sequentially formed, the rapid exhaust valve 52 is used to remove the upstream expansion bag 22, the middle The pressure inside the expansion bag 24 and the downstream expansion bag 26 is exhausted to atmospheric pressure. The first maintenance pressure PcH1, the second maintenance pressure PcH2, and the third maintenance pressure PcH3 are a plurality of preset pressures that are lower than the diastolic blood pressure value DAP of the living body 14 as the subject, for example, within the range of 20 to 60 mmHg. This is a value in stages (three stages in this embodiment).

The pulse wave extraction unit 88 outputs an output indicating the compression pressure Pc1 in the upstream inflation bag 22 from the first pressure sensor T1 in the first maintenance interval, the second maintenance interval, and the third maintenance interval in which the compression pressure Pc is maintained. A pair of pulse waves MW1 and pulse waves are obtained from the signal and the output signal from the third pressure sensor T3 indicating the compression pressure Pc3 in the downstream expansion bag 26 through a band pass filter for pulse wave discrimination of, for example, 0.5 Hz to 20 Hz. Each MW3 is extracted and stored.

Similarly to the above, the pulse wave velocity calculation unit 90 calculates the obtained value in the state where the compression pressure Pc is maintained, for each of the three first maintenance intervals, the second maintenance interval, and the third maintenance interval in which the compression pressure Pc is maintained. It was calculated every time a pulse wave occurred from the time difference Δt between the rising points or peak points of the pair of pulse waves MW1 and MW3 and the known distance L13 between the upstream expansion bag 22 and the downstream expansion bag 26. One set of measured data of the pulse wave propagation velocity PWV (=L13/Δt) and the step pressure, that is, the compression pressure Pc when the pulse wave is generated, is calculated for each three steps, and a total of three sets of measured data are obtained. remember. With three actually measured data points, it is possible to perform a linear regression analysis.

The inclination α calculation unit 96 calculates the pulse rate stored for each three step pressures in two-dimensional coordinates between the axis representing the logarithm ln (PWV ² ) of the square value of the pulse wave propagation velocity PWV and the axis representing -Pc. Actual measurements at three points showing three sets of actual measurement data: the logarithm ln (PWV ² ) of the square value of the wave propagation velocity PWV (=L13/Δt) and the step pressure, that is, the compression pressure Pc when the pulse wave is generated. By performing linear regression analysis of the data points, a predetermined linear regression line equation (2) between the logarithm ln of the square value of the pulse wave velocity (PWV ² ) and the transmural pressure Pt of the arterial blood vessel is obtained. The coefficient value of the first term on the right side of equation (3) of the linear regression line −Pc converted from is determined as the slope α.

The intercept β calculation unit 98 calculates the intercept β based on the slope α calculated by the slope α calculation unit 96 from the linear relational expression (4). That is, the intercept β is calculated by substituting the slope α calculated by the slope α calculation unit 96 into the linear relational expression (4).

The diastolic blood pressure estimation formula setting unit 100 substitutes the slope α calculated by the slope α calculation unit 96 and the intercept β calculated by the intercept β calculation unit 98 into the diastolic blood pressure estimation formula (5), and A diastolic blood pressure estimation formula (5) reflecting the relationship is set and stored.

The blood pressure estimating unit 102 calculates the pulse wave propagation velocity PWV and the compression pressure Pc that are actually measured at a predetermined cycle, for example, from one pulse cycle to more than ten pulse cycles, in a monitor interval in which the monitor pressure PcHm is maintained after time tm1 in FIG. 20, for example. The estimated diastolic blood pressure value DAPe is repeatedly calculated by substituting the value DAPe into the diastolic blood pressure estimation formula (5). A moving average value of the calculated diastolic blood pressure values DAPe may be calculated. The diastolic blood pressure estimating unit 104 causes the display device 78 to display the calculated diastolic blood pressure estimated value DAPe in chronological order. The monitoring maintenance pressure PcHm is preferably set lower than the diastolic blood pressure of the living body, and may be the same as any of the first maintenance pressure PcH1 to third maintenance pressure PcH3, or may be set at a different maintenance pressure. There may be.

In this example, as in Example 1, the intercept β and slope α included in the linear regression equation (2) leading to the diastolic blood pressure estimation equation (5) are as shown in equation (4). They have a certain linear relationship with each other and are not influenced by the person being measured. Therefore, the diastolic blood pressure value DAPe can be measured with high accuracy because it is not easily influenced by the individual biological characteristics of the subject. Further, there is an advantage that there is no need to perform calibration unlike the conventional method of estimating blood pressure using pulse wave velocity PWV.

In the above-mentioned Example 1, in order to set the equation (5) for estimating the diastolic blood pressure DAPe of the living body 14 to be measured, the amplitude of the pulse wave extracted by the pulse wave extraction unit 88 has a maximum value. Based on the pressure value of the step pressure (value equivalent to mean blood pressure), a predetermined number of continuous steps (for example, 6 ) or the plurality of preset step pressures is the amplitude of the pulse wave extracted by the pulse wave extracting unit 88 as the compression pressure Pc of the compression cuff 12 is lowered. Pulse wave propagation is determined by the pulse wave propagation velocity calculation unit 90 from the pulse waves obtained at a predetermined number of consecutive step pressures (for example, six) after passing through a predetermined number of step pressures (for example, two) from the step pressure. Speed PWV (=L13/Δt) was calculated. However, in the third embodiment, the compression pressure control unit 86 focuses on the fact that the pulse wave shape sequentially obtained by the pulse wave extraction unit 88 changes sequentially in the process of decreasing from the systolic blood pressure SAP, and Pulse wave propagation for setting equation (5) for determining the start of collecting actual measurement data based on the change and estimating the diastolic blood pressure DAPe of the living body 14 from the pulse waves collected at subsequent multiple step pressures. Calculation of speed PWV (=L13/Δt) is started.

In the process of lowering the compression pressure Pc of the compression cuff 12, the shape of the pulse wave (cuff pulse wave), which is the pressure vibration of the compression pressure Pc within the compression cuff 12 that occurs in response to a change in the volume of the arterial blood vessel 18, is determined by the amplitude. In the process of changing from the maximum value to the minimum value, as shown in FIG. 21, there is a descending section LP that shows a substantially constant value, and the descending section LP becomes shorter as the compression pressure Pc decreases. , will soon disappear as shown in the dashed circle. The descending section LP is considered to be a section in the cycle of one pulse wave near the diastolic blood pressure point in which changes in blood vessel volume are suppressed due to complete occlusion of the arterial blood vessel 18.

In this embodiment, the pulse wave velocity calculation unit 90 calculates the pulse wave velocity at several steps, for example, 6 steps, from the step pressure at which the descending section LP disappeared or from the step pressure next to the step pressure at which the descending section LP disappeared. PWV (=L13/Δt) is calculated sequentially, and multiple sets of measured data of compression pressure Pc and pulse wave velocity PWV [ln(PWV1 ² ), Pc1]...[ln(PWVn ² ), Pcn] collected and stored.

Next, in the same manner as in the above-described embodiment, the slope α calculation unit ⁹⁶ calculates a plurality of By performing a linear regression analysis of multiple measured data points representing a set of measured data, the coefficient value of the first term on the right side of the linear regression line - Pc equation (3) converted from the linear regression line equation (2) is obtained as the slope α. Further, the intercept β calculation unit 98 calculates the intercept β based on the slope α calculated by the slope α calculation unit 96 from the linear relational expression (4), as in the above embodiment. That is, the intercept β is calculated by substituting the slope α calculated by the slope α calculation unit 96 into the linear relational expression (4). Further, similarly to the above embodiment, the diastolic blood pressure estimation formula setting unit 100 calculates the slope α calculated by the slope α calculation unit 96 and the intercept β calculated by the intercept β calculation unit 98 into equation (5). The diastolic blood pressure estimation formula (5) that reflects the inherent relationship of the living body is set and stored. Then, as in the above-described embodiment, the blood pressure estimating unit 102 performs actual measurement at a predetermined cycle, for example, from one pulse cycle to more than ten pulse cycles, in the monitor interval in which the monitor pressure PcHm is maintained after time tm1 in FIG. 20, for example. By substituting the pulse wave propagation velocity PWV and compression pressure Pc into the diastolic blood pressure estimation formula (5), the estimated diastolic blood pressure value DAPe is repeatedly calculated.

In this example, as in Examples 1 and 2 described above, the intercept β and slope α included in the linear regression equation (2) leading to the diastolic blood pressure estimation equation (5) are shown in equation (4). As such, they have a fixed linear relationship and are not influenced by the person being measured. Therefore, the diastolic blood pressure value DAPe can be measured with high accuracy because it is not easily influenced by the individual biological characteristics of the subject. Further, there is an advantage that there is no need to perform calibration unlike the conventional method of estimating blood pressure using pulse wave velocity PWV. In addition, in this embodiment, the start of collecting actual measurement data is determined after the falling section LP indicating the occlusion state of the blood vessel disappears within one pulse wave cycle. The step pressure for analyzing the pulse wave velocity PWV can be more accurately limited to the range below the diastolic blood pressure without being affected by the pulse wave velocity PWV, so compared to the above-mentioned embodiment, stable expansion can be achieved regardless of the subject. Estimation of period blood pressure becomes possible.

Although one embodiment of the present invention has been described above in detail with reference to the drawings, the present invention is not limited to this embodiment and may be implemented in other forms.

For example, in the embodiment, the compression band 12 was equipped with three inflation bags, that is, the upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26. As long as there is a pulse wave propagation velocity detection means using a pair of pressure pulse wave sensors instead of the time difference between the pulse wave and the pulse wave from the downstream expansion bag 26, it is sufficient that at least one expansion bag is provided. A compression band with one chamber may be used.

The pulse wave velocity PWV may be detected in any artery passing through the compression band, and may be detected at a position away from the compression band. Further, the pulse wave propagation velocity PWV may be detected using a pressure pulse wave sensor, an impedance pulse wave, or an ultrasound Doppler.

In the above-mentioned Example 1, the estimated diastolic blood pressure value DAPe is the average value of the diastolic blood pressures DAPe1, DAPe2, and DAPe3 obtained for each of the first maintenance pressure PcH1, the second maintenance pressure PcH2, and the third pressure PcH3. Although previously used, diastolic blood pressure DAPe may be estimated with a single maintenance pressure.

In the above-mentioned embodiment, the diastolic blood pressure DAPe was estimated at the time of occurrence of a change in the pulse wave velocity PWV for which the judgment in S34 was affirmative in the monitoring period in which the monitor maintenance pressure PcHm was maintained. It may be estimated all the time.

Moreover, although the compression band 12 of the above-mentioned embodiment employs step pressure reduction when measuring blood pressure, continuous pressure reduction may be adopted in which the compression pressure Pc is continuously changed.

Furthermore, although the compression band 12 of the above-described embodiment employs step pressure reduction when measuring blood pressure, it may also be a step pressure increase in which the compression pressure Pc is increased in steps, or a continuous pressure increase in which the pressure is continuously increased. .

The above-mentioned embodiment is merely one embodiment, and although no other examples are given, the present invention can be implemented with various changes and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof. I can do it.

10: Blood pressure measuring device 12: Compression band 14: Living body (person to be measured)
16: Upper arm (compressed area)
18: Arterial blood vessel 22: Upstream expansion bag (inflation bag)
24: Intermediate expansion bag (expansion bag)
26: Downstream expansion bag (expansion bag)
82: Linear regression linear equation storage unit 84: Linear relationship storage unit 86: Compression pressure control unit 88: Pulse wave extraction unit 90: Pulse wave velocity calculation unit 94: Unique relationship generation unit 102: Blood pressure estimation unit 104: Diastolic blood pressure Estimation unit 108: Blood pressure change determination unit

Claims (9)

The diastolic blood pressure of the subject is determined using the pressure applied by a compression band that compresses the arterial blood vessel at the compressed site of the subject and the square value of the pulse wave propagation velocity of the arterial blood vessel passing through the compressed site. A blood pressure measuring device for estimating,
a pulse wave velocity measurement unit that measures pulse wave velocity PWV of the compressed area under compression by the compression band;
From the conversion equation from the linear regression formula determined in advance between the logarithm of the square value of the pulse wave propagation velocity and the transmural pressure of the arterial blood vessel, the compression pressure and the pressure measured at the compression pressure are determined. a slope calculation unit that calculates the slope α of the linear regression equation based on the pulse wave propagation velocity of the compressed region;
an intercept calculation unit that calculates the intercept β of the linear regression equation based on the slope α of the linear regression equation from a pre-stored linear relationship between the intercept β and the slope α included in the linear regression equation; and,
The conversion equation from the linear regression linear equation includes the compression pressure to be subtracted from the diastolic blood pressure representing the transmural pressure, the pulse wave propagation velocity of the compressed area, and the linear regression line calculated by the slope calculation unit. a diastolic blood pressure estimation formula setting unit that sets a diastolic blood pressure estimation formula by substituting the slope of the equation and the intercept calculated by the intercept calculation unit;
a diastolic blood pressure estimation unit that estimates the diastolic blood pressure DAP of the subject based on the actual compression pressure Pc and the pulse wave velocity PWV of the compressed area from the diastolic blood pressure estimation formula; A blood pressure measuring device featuring: The blood pressure measuring device according to claim 1, wherein the linear regression equation is expressed by the following equation (2).
Pt=α・ln(PWV ² )+β... (2)
However, Pt is transmural pressure (=diastolic blood pressure DAP−compression pressure Pc), and PWV is pulse wave velocity. The blood pressure measuring device according to claim 1, wherein the conversion equation from the linear regression equation is expressed by the following equation (3).
-Pc=α・ln(PWV ² )+(β-DAP)... (3) The blood pressure measuring device according to claim 1, wherein the pre-stored linear relationship is expressed by the following equation (4).
β=γ・α+δ... (4)
However, γ is a constant indicating the slope of the above linear relationship, and δ is a constant indicating the intercept of the above linear relationship. The blood pressure measuring device according to claim 1, wherein the diastolic blood pressure estimation formula is expressed by the following formula (5).
DAPe=α・ln(PWV ² )+(β+Pc)... (5)
However, DAPe is an estimated blood pressure value. The diastolic blood pressure estimating unit calculates the diastolic blood pressure of the measured person based on the actual compression pressure and the pulse wave propagation velocity of the compressed area for each of the plurality of types of compression pressure by the compression band, from the diastolic blood pressure estimation formula. The blood pressure measuring device according to claim 1, wherein the diastolic blood pressure of the plurality of compression pressures is estimated, and the average value of the diastolic blood pressures obtained for each of the plurality of compression pressures is estimated as the diastolic blood pressure. The diastolic blood pressure estimating unit calculates the diastolic blood pressure of the subject based on the actual compression pressure and the pulse wave propagation velocity of the compressed area at a compression pressure by the compression band that is lower than the diastolic blood pressure of the subject. The blood pressure measuring device according to claim 1, wherein the blood pressure measuring device estimates the diastolic blood pressure of the patient. A pair of pulse wave sensors are arranged at two positions separated by a predetermined distance from each other along the arterial blood vessel to detect pulse waves, and the pulse wave propagation velocity is detected by each of the pair of pulse wave sensors. The blood pressure measuring device according to claim 1, wherein the blood pressure measuring device is calculated based on a time difference between pulse waves and the predetermined distance. a compression pressure control unit that maintains the compression pressure by the compression band at a monitor pressure lower than the diastolic blood pressure of the living body; and a preset variation in the pulse wave propagation velocity measured during a period in which the monitor pressure is maintained. and a blood pressure fluctuation determination unit that determines the occurrence of blood pressure fluctuation based on deviation from the determination range,
The diastolic blood pressure estimating unit calculates a value based on the actual compression pressure and the pulse wave velocity of the compressed region from the diastolic blood pressure estimation formula when the blood pressure change determining unit determines that a blood pressure fluctuation has occurred. The blood pressure measuring device according to claim 1, wherein the diastolic blood pressure of the subject is estimated by

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