Blood pressure measuring device

Abstract

To provide a blood pressure measuring device that can accurately determine a highest blood pressure value.SOLUTION: A highest blood pressure value calculation unit 88 determines a highest blood pressure value SBP of a living body 14 on the basis of a change in a correlation coefficient Φ(τ) between an upstream volume pulse wave represented by a pulse wave signal SM1 and a downstream volume pulse wave represented by a pulse wave signal SM3, obtained sequentially in a process in which the compression pressure of a tourniquet 12 is made to decrease from a pressure value higher than the highest blood pressure value of the living body. Because the change in the correlation coefficient Φ(τ) between the upstream and downstream volume pulse waves indicates initiation of an actual blood flow in an artery previously occluded by the tourniquet 14, there is no influence by feature amounts specific to the living body such as vascular compliance, heart rate, pulse pressure value, blood pressure value, and the like, which are different among subjects. As a result, determination accuracy of the highest blood pressure value SBP of the living body is improved.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a blood pressure measuring device including a compression band that is wound around a compressed part of a living body, such as an arm or an ankle.

Background Art

[0002] In a blood pressure measuring device that includes a compression band wound around a compressed part of a living body and sequentially extracts a pulse wave, which is a pressure vibration in the compression band, while changing the compression pressure of the compression band, and automatically determines a blood pressure value of the living body based on the change in the pulse wave, there is known a compression band having a plurality of inflatable bags that are arranged in the width direction and each compress a compressed part of the living body. For example, the one described in Patent Document 1 is such a device.

[0003] In the blood pressure measuring device described in Example 1 of Patent Document 1, in the process of reducing the compression pressure by the compression band from a value higher than the maximum blood pressure value, an envelope line connecting the peaks of the volume pulse waves obtained from one of the plurality of inflatable bags, for example, the middle inflatable bag, is used to determine the compression pressures at the points showing a sharp rise and the points showing a sharp fall as the maximum blood pressure value and the minimum blood pressure value, respectively, by a so-called oscillometric method blood pressure value determination algorithm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the so-called oscillometric blood pressure determination algorithm, which determines the systolic and diastolic blood pressure values ​​based on the compression pressure at points where the envelope connecting the peaks of the volume pulse wave obtained from one of multiple inflation bags, such as an intermediate inflation bag, shows a rapid increase and a rapid decrease, the measurement error in blood pressure measurements is large and measurement accuracy cannot be obtained because the compression pressure obtained from the compression band is reduced from a value higher than the systolic blood pressure value to a value higher than the systolic blood pressure value.

[0006] This invention was made against the above circumstances, and its objective is to provide a blood pressure measuring device that can accurately determine the systolic blood pressure value. [Means for solving the problem]

[0007] Based on the above circumstances, the inventors conducted various studies and found that when the compression pressure from the compression band is reduced to near the systolic blood pressure value, the waveforms of the upstream volume pulse wave obtained from the upstream volume pulse wave obtained from the upstream volume pulse wave obtained from the downstream volume pulse wave obtained from the downstream volume pulse wave become similar, and the cross-correlation coefficient between these upstream and downstream volume pulse waves increases sharply. The inventors found that the point at which the cross-correlation coefficient between the upstream and downstream volume pulse waves sharply increases is evidence that blood flow has started in the previously occluded artery, and that the systolic blood pressure value can be determined based on the compression pressure at that point. The present invention is based on this finding.

[0008] In other words, the gist of the first invention is a blood pressure measuring device comprising: (a) a compression band that is wrapped around a compressed area of ​​a living body and has independent upstream and downstream inflation bags that compress different compressed areas in the longitudinal direction of the arteries within the living body, and the upstream and downstream inflation bags compress the arterial blood vessels within the compressed area with the same compression pressure, the device comprising: (b) a volume pulse wave extraction unit that sequentially extracts upstream volume pulse waves and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body and included in the compression pressure in the upstream and downstream inflation bags, respectively, during the process of decreasing the compression pressure on the compressed area by the compression band from a value higher than the systolic blood pressure value of the living body; (c) a cross-correlation coefficient calculation unit that sequentially calculates the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave sequentially extracted by the volume pulse wave extraction unit; and (d) a systolic blood pressure value calculation unit that calculates the systolic blood pressure value of the living body based on the change in the cross-correlation coefficient sequentially calculated by the cross-correlation coefficient calculation unit. (e) The systolic blood pressure calculation unit includes (e1) a normalization processing unit that converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which has been sequentially calculated by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that has been normalized so that its maximum value is 1; (e2) a difference value calculation unit that sequentially calculates the difference value of the normalized cross-correlation coefficient; and (e3) a systolic blood pressure determination unit that determines the systolic blood pressure of the living body based on the compression pressure on the compressed part of the living body by the compression band when the maximum value of the difference value of the normalized cross-correlation coefficient, which has been sequentially calculated by the difference value calculation unit, occurs. It is about doing.

[0011] The 2 The gist of the invention is the first Clearly In this configuration, the compression band reduces the compression pressure on the area to be compressed from a value higher than the systolic blood pressure of the living body by repeatedly alternating between a constant compression pressure section in which the compression pressure is kept constant and a change in compression pressure section in which the compression pressure is changed between the constant compression pressure sections. The volume pulse wave extraction unit sequentially extracts upstream and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body, during the constant compression pressure section.

[0012] The 3 The gist of the invention is: (a) A blood pressure measuring device comprising a compression band that is wrapped around a compressed area of ​​a living body and has independent upstream and downstream inflation bags that compress different compressed areas in the longitudinal direction of the arteries within the living body, and the upstream and downstream inflation bags compress the arterial blood vessels within the compressed area with the same compression pressure, (b) a volume pulse wave extraction unit that sequentially extracts upstream volume pulse waves and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body and are included in the compression pressure in the upstream and downstream inflation bags, respectively, during the process of decreasing the compression pressure on the compressed area by the compression band from a value higher than the systolic blood pressure value of the living body, (c) a cross-correlation coefficient calculation unit that sequentially calculates the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave sequentially extracted by the volume pulse wave extraction unit, and (d) a systolic blood pressure value calculation unit that calculates the systolic blood pressure value of the living body based on the change in the cross-correlation coefficient calculated sequentially by the cross-correlation coefficient calculation unit, (f) The aforementioned systolic blood pressure value calculation unit, (f1) A normalization processing unit that converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which has been sequentially calculated by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that has been normalized so that its maximum value is 1, and (f2) The aforementioned Normalization Mutual relationship Number The system includes a systolic blood pressure determination unit that determines the systolic blood pressure value based on the compression pressure applied to the compressed area of ​​the body by the compression band when the pressure exceeds a preset threshold. [Effects of the Invention]

[0013] According to the blood pressure measuring device of the first invention, the systolic blood pressure value is automatically determined by the systolic blood pressure value calculation unit based on the change in the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which is obtained sequentially during the process in which the compression pressure of the compression band is lowered from a value higher than the systolic blood pressure value. As a result, the change in the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave indicates that blood flow in the artery that was occluded by the compression band has actually started, and is not affected by the unique biological characteristics of each subject, such as vascular compliance, pulse rate, pulse pressure value, and blood pressure value, thus improving the accuracy of determining the systolic blood pressure value of the subject. Furthermore, the systolic blood pressure calculation unit includes a normalization processing unit that converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which are sequentially calculated by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that is normalized so that its maximum value is 1. As a result, the accuracy of determining the systolic blood pressure of the living body is further improved because it is not affected by the magnitude of the absolute value of the cross-correlation coefficient. Moreover, the systolic blood pressure calculation unit includes a difference value calculation unit that sequentially calculates the difference value of the normalized cross-correlation coefficient, and a systolic blood pressure determination unit that determines the systolic blood pressure of the living body based on the compression pressure on the compressed part of the living body by the compression band when the maximum value of the difference value of the normalized cross-correlation coefficient, which is sequentially calculated by the difference value calculation unit, occurs. As a result, the difference value of the normalized cross-correlation coefficient emphasizes the change in the normalized cross-correlation coefficient, further improving the accuracy of determining the systolic blood pressure of the living body.

[0016] The 2 According to the blood pressure measuring device of the invention, the compression band reduces the compression pressure on the area to be compressed from a value higher than the systolic blood pressure of the living body by repeatedly alternating between a constant compression pressure section in which the compression pressure is kept constant and a compression pressure variation section in which the compression pressure is changed between the constant compression pressure section. The volume pulse wave extraction unit sequentially extracts upstream volume pulse waves and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body, during the constant compression pressure section. As a result, distortion of the waveforms of the upstream volume pulse waves and downstream volume pulse waves extracted by the volume pulse wave extraction unit is suppressed, thereby further improving the accuracy of determining the systolic blood pressure of the living body.

[0017] The 3 According to the blood pressure measuring device of the invention, The systolic blood pressure value calculation unit automatically determines the systolic blood pressure value of the living organism based on the change in the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which is obtained sequentially during the process in which the compression pressure of the compression band is lowered from a value higher than the systolic blood pressure value. Since the change in the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave indicates that blood flow in the artery that was occluded by the compression band has actually started, the determination of the systolic blood pressure value of the living organism is not affected by the unique biological characteristics that differ for each subject, such as vascular compliance, pulse rate, pulse pressure, and blood pressure, thus improving the accuracy of determining the systolic blood pressure value of the living organism. Furthermore, the systolic blood pressure value calculation unit includes a normalization processing unit that converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which is calculated sequentially by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that normalizes to a maximum value of 1. This further improves the accuracy of determining the systolic blood pressure value of the living organism, as it is not affected by the magnitude of the absolute value of the cross-correlation coefficient. The systolic blood pressure value calculation unit is the Normalization Mutual relationship Number The system includes a systolic blood pressure determination unit that determines the systolic blood pressure value based on the compression pressure applied to the compressed area of ​​the body by the compression band when a preset threshold is exceeded. This indicates that blood flow in the artery that was blocked by the compression band has actually started. Normalization Since the systolic blood pressure value is determined based on the change in the cross-correlation coefficient, the accuracy of determining the systolic blood pressure value in a living organism is improved. [Brief explanation of the drawing]

[0018] [Figure 1] It is a block diagram for explaining the configuration of a blood pressure measuring device which is an embodiment of the present invention. [Figure 2] It is a view showing a part of the outer peripheral surface of the compression band in FIG. 1 with a notch. [Figure 3] It is a plan view showing an upstream expansion bag, an intermediate expansion bag, and a downstream expansion bag provided in the compression band of FIG. 2. [Figure 4] It is a sectional view taken along line IV-IV of FIG. 3, showing the upstream expansion bag, the intermediate expansion bag, and the downstream expansion bag cut in the width direction. [Figure 5] It is a functional block diagram for explaining the main part of the control function provided in the electronic control device of FIG. 1. [Figure 6] It is a time chart for explaining the main part of the compression pressure control operation by the cuff pressure control unit of FIG. 5. [Figure 7] It is a view for explaining the generation intervals of the upstream volume pulse wave and the downstream volume pulse wave extracted by the volume pulse wave extraction unit of FIG. 5 among the compression pressures controlled by the cuff pressure control unit of FIG. 5. [Figure 8] It is a view showing the change of the normalized cross-correlation coefficient calculated for each step pressure by the cross-correlation coefficient calculation unit and the normalization processing unit of FIG. 5 with respect to the compression pressure by the compression band. [Figure 9] It is a view showing the change of the difference value of the normalized cross-correlation coefficient calculated for each step pressure by the difference value calculation unit of FIG. 5 with respect to the compression pressure. [Figure 10] It is a view showing a flowchart for explaining the main part of the blood pressure measurement operation of the electronic control device of FIG. 5. [Figure 11] It is a flowchart for explaining in detail the content of the maximum blood pressure determination routine of FIG. 10. [Figure 12] It is a view showing the error of the maximum blood pressure value measured by the oscillometric method with respect to the maximum blood pressure value measured by the auscultation method. [Figure 13] It is a view showing the error of the maximum blood pressure value measured according to an example of the present invention with respect to the maximum blood pressure value measured by the auscultation method.

Mode for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiment, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0020] Figure 1 shows an example of a blood pressure measuring device 10 of the present invention, which includes an upper arm compression band 12 wrapped around the limb of a living body 14, such as the upper arm 16, which is the site to be compressed. 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 artery 18 in the upper arm 16, after the blood pressure measurement is started, this blood pressure measuring device 10 sequentially extracts pulse waves, which are pressure oscillations of the compression pressure PC in the compression band 12 that occur in response to changes in the volume of the artery 18, and automatically measures the systolic blood pressure value SBP and diastolic blood pressure value DBP of the living body 14 based on the information obtained from these pulse waves.

[0021] Figure 2 shows a cutaway of a portion of the outer peripheral nonwoven fabric 20a that encloses the outer periphery of the compression band 12. As shown in Figure 2, the compression band 12 comprises a strip-shaped outer bag 20 consisting of an outer peripheral nonwoven fabric 20a and an inner peripheral nonwoven fabric 20b made of synthetic resin fibers whose back surfaces are laminated with a synthetic resin such as PVC (polyvinyl chloride), and an upstream inflation bag 22, an intermediate inflation bag 24, and a downstream inflation bag 26 that are sequentially housed in the width direction within the strip-shaped outer bag 20 and are made of a flexible sheet such as a soft polyvinyl chloride sheet, capable of independently compressing the upper arm 16. The compression band 12 is designed to be detachably attached to the upper arm 16 by detachably adhering a hook-and-loop fastener 28a attached to the end of the outer peripheral nonwoven fabric 20a to a napped pile 28b attached to the end of the inner peripheral nonwoven fabric 20b.

[0022] The upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26 are connected in the width direction of the longitudinal compression band 12, i.e., in the longitudinal direction of the artery 18, and each has an independent air chamber that compresses a separated portion of the artery 18 in the longitudinal direction of the brachial arm 16, and is provided with tube connection connectors 32, 34, and 36 on its outer surface. These tube connection connectors 32, 34, and 36 are exposed on the outer surface of the compression band 12 through the outer surface nonwoven fabric 20a.

[0023] Figure 3 is a plan view showing the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 provided within the compression band 12, and Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. The upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 are for detecting pulse waves, which are pressure oscillations generated in response to volume changes in the artery 18 compressed by them, and each is longitudinally shaped. The upstream inflation bag 22 and the downstream inflation bag 26 are positioned adjacent to both sides of the intermediate inflation bag 24. The intermediate inflation bag 24 is positioned in the center of the width direction of the compression band 12, sandwiched between the upstream inflation bag 22 and the downstream inflation bag 26. 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 apart in the longitudinal direction of the upper arm 16, and the intermediate inflation bag 24 is positioned 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.

[0024] The intermediate inflation bag 24 has side edges with a so-called gusset structure on both sides. That is, at both ends of the intermediate inflation bag 24 in the longitudinal direction of the upper arm 16, i.e., in the width direction of the compression band 12, a pair of folded grooves 24f and 24g are formed, respectively, made of flexible sheets that are folded in a direction toward each other so that they become deeper as they approach each other. The ends 22a and 26a of the upstream inflation bag 22 and the downstream inflation bag 26 adjacent to the intermediate inflation bag 24 are inserted into the pair of folded 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 overlap each other, and the end 24b of the intermediate inflation bag 24 and the end 26a of the downstream inflation bag 26 overlap each other, creating an overlap structure, so that when the upstream inflation bag 22, intermediate inflation bag 24 and downstream inflation bag 26 compress the upper arm 16 at equal pressure, a uniform pressure distribution is obtained even near their boundaries.

[0025] The upstream inflation bag 22 and the downstream inflation bag 26 also have gusseted side edges at ends 22b and 26b opposite to the intermediate inflation bag 24. Specifically, the end 22b of the upstream inflation bag 22 opposite to the intermediate inflation bag 24 has a folded groove 22f made of a flexible sheet folded in a direction toward each other so that it becomes deeper as they get closer. Similarly, the end 26b of the downstream inflation bag 26 opposite to the intermediate inflation bag 24 has a folded groove 26g made of a flexible sheet folded in a direction toward each other so that it becomes deeper as they get closer. To prevent them from protruding in the width direction of the compression band 12, the sheets constituting the folded groove 22f are connected to the opposite side, i.e., the side facing the intermediate inflation bag 24, via a connecting sheet 38 with through holes located inside the upstream inflation bag 22. Likewise, the sheets constituting the folded groove 26g are connected to the opposite side, i.e., the side facing the intermediate inflation bag 24, via a connecting sheet 40 with through holes located inside the downstream inflation bag 26.

[0026] As a result, the compression pressure on the artery 18 of the upper arm 16 is obtained at the ends 22b and 26b of the upstream inflation bag 22 and the downstream inflation bag 26 in the same way as in other parts, so that the effective compression width in the width direction of the compression band 12 is equal to its width dimension. The width direction of the compression band 12 is about 12 cm, and since the structure has three upstream inflation bags 22, an intermediate inflation bag 24, and a downstream inflation bag 26 arranged in the width direction, each of them inevitably has a width dimension of about 4 cm in practical terms. In order to generate sufficient compression function even with such a narrow width dimension, the ends 24a and 24b of the intermediate inflation bag 24 and the ends 22a of the upstream inflation bag 22 and the ends 26a of the downstream inflation bag 26 are arranged in an overlapping structure, and the ends 22b and 26b of the upstream inflation bag 22 and the downstream inflation bag 26 on the opposite side from the intermediate inflation bag 24 are made into so-called gusseted side edges.

[0027] 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 walls of the pair of folding grooves 24f and 24g into which they are inserted, i.e., the opposing groove sides, are interposed longitudinal shielding members 42n and 42m, respectively, which have anisotropic stiffness such that the bending stiffness of the compression band 12 in the width direction is higher than the bending stiffness of the compression band 12 in the longitudinal direction. The shielding member 42n has a length dimension similar to the overlap dimension of the upstream expansion bag 22 and the intermediate expansion bag 24. Similarly, the shielding member 42m has a length dimension similar to the overlap dimension of the downstream expansion bag 26 and the intermediate expansion bag 24.

[0028] As shown in Figures 3 and 4, longitudinal shielding members 42n and 42m are interposed in the outer circumferential gap between the end 22a of the upstream expansion bag 22 and the folding groove 24f into which it is inserted, and in the outer circumferential gap between the end 26a of the downstream expansion bag 26 and the folding groove 24g into which it is inserted. In this embodiment, the shielding effect is greater in the outer circumferential gap than in the inner circumferential gap, so the longitudinal shielding members 42n and 42m are provided in the outer circumferential gap, but they may also be provided in both the outer and inner circumferential gaps.

[0029] The shielding members 42n and 42m are constructed by arranging multiple flexible hollow tubes 44 made of resin parallel to each other in the circumferential direction of the upper arm 16 (i.e., the longitudinal direction of the compression band 12), and these flexible hollow tubes 44 are connected to each other either directly by molding or bonding, or indirectly via other members such as flexible sheets such as adhesive tape. The shielding member 42n is attached to multiple fastening sheets 46 provided at multiple locations on the outer circumference of the end 22a of the upstream inflation bag 22 on the intermediate inflation bag 24 side. Similarly, the shielding member 42m is attached to multiple fastening sheets 46 provided at multiple locations on the outer circumference of the end 26a of the downstream inflation bag 26 on the intermediate inflation bag 24 side.

[0030] Returning to Figure 1, in the blood pressure measuring device 10, the air pump 50, the rapid exhaust valve 52, and the exhaust control valve 54 are connected to the main piping 56, respectively. From this main piping 56, a first branch pipe 58 connected to the upstream inflation bag 22, a second branch pipe 62 connected to the intermediate inflation bag 24, and a third branch pipe 64 connected to the downstream inflation bag 26 are branched off, respectively. The first branch pipe 58 is equipped with a first on-off valve E1 for directly opening and closing the connection between the air pump 50 and the upstream inflation bag 22. The second branch pipe 62 is equipped with a second on-off valve E2 for directly opening and closing the connection between the air pump 50 and the intermediate inflation bag 24. The third branch pipe 64 is equipped with a third on-off valve E3 for directly opening and closing the connection between the air pump 50 and the downstream inflation bag 26.

[0031] A first pressure sensor T1 for detecting the pressure value in the upstream expansion bag 22 is connected to the first branch pipe 58, a second pressure sensor T2 for detecting the pressure value in the intermediate expansion bag 24 is connected to the second branch pipe 62, a third pressure sensor T3 for detecting the pressure value in the downstream expansion bag 26 is connected to the third branch pipe 64, and a fourth pressure sensor T4 for detecting the compression pressure PC of the compression zone 12 is connected to the main pipe 56. The electronic control unit 70 is supplied with an output signal from the first pressure sensor T1 indicating the pressure value in the upstream expansion bag 22, i.e., the compression pressure PC1 of the upstream expansion bag 22, an output signal from the second pressure sensor T2 indicating the pressure value in the intermediate expansion bag 24, i.e., the compression pressure PC2 of the intermediate expansion bag 24, an output signal from the third pressure sensor T3 indicating the pressure value in the downstream expansion bag 26, i.e., the compression pressure PC3 of the downstream expansion bag 26, and an output signal from the fourth pressure sensor T4 indicating the compression pressure PC of the compression zone 12.

[0032] The electronic control unit 70 is a so-called microcomputer that includes a CPU 72, RAM 74, ROM 76, display device 78, and I / O ports (not shown). The electronic control unit 70 processes input signals according to a program pre-stored in ROM 76, using the memory function of RAM 74 with the CPU 72, and in response to the operation of the blood pressure measurement start operation button 80, it controls the electric air pump 50, rapid exhaust valve 52, exhaust control valve 54, first on / off valve E1, second on / off valve E2, and third on / off valve E3, respectively, thereby performing automatic blood pressure measurement control and displaying the measurement results on the display device 78.

[0033] Figure 5 is a functional block diagram illustrating the main components of the control functions provided in the electronic control unit 70. In Figure 5, the electronic control unit 70 functionally includes a cuff pressure control unit 82, a volume pulse wave extraction unit 84, a diastolic blood pressure calculation unit 86, a systolic blood pressure calculation unit 88, a blood pressure value display output unit 98, and the like. Figure 6 is a time chart illustrating the main components of the compression pressure control operation of the compression band 12 by the cuff pressure control unit 82.

[0034] In response to the operation of the blood pressure measurement start button 80 shown in Figure 5, the cuff pressure control unit 82 closes the rapid exhaust valve 52 and the exhaust control valve 54, opens the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3, and operates the air pump 50, thereby rapidly increasing the compression pressure PC of the compression band 12 against the body 14 until it reaches a pressure sufficiently higher than the systolic blood pressure value SBP of the body 14, for example, a preset target pressure value PCM of 180 mmHg.

[0035] Next, with the exhaust control valve 54 half-open, the cuff pressure control unit 82 simultaneously opens the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3 repeatedly for a predetermined period at a predetermined cycle, thereby slowly lowering the compression pressure PC of the compression band 12 at a predetermined rate, so that multiple step pressures P1, P2, P3, ... Px are sequentially formed at intervals of, for example, 2 to 5 mmHg, until the compression pressure PC of the compression band 12 reaches a pressure sufficiently lower than the lowest blood pressure value of the body 14, for example, a measurement termination pressure value PCE set to 30 mmHg, by repeatedly creating a constant compression pressure section Tc in which the compression pressure PC is kept constant, and a change in compression pressure section Td in which the compression pressure PC is changed (decreased) within the constant compression pressure section Tc.

[0036] When the compression pressure PC of the compression band 12 becomes smaller than the measurement termination pressure PCE, the cuff pressure control unit 82 uses the rapid exhaust valve 52 to release the pressure in the upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26 to atmospheric pressure. In the compression band 12 controlled in this way, the upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26 compress the living body 14 with the same compression pressure PC, but Figure 6 shows the compression pressure PC of the compression band 12 detected by the fourth pressure sensor.

[0037] The volume pulse wave extraction unit 84 sequentially extracts and stores pulse wave signals SM1, SM2, and SM3, which represent the upstream volume pulse wave, intermediate volume pulse wave, and downstream volume pulse wave, respectively, which are waveforms of pressure fluctuations (AC components) synchronized with the heartbeat of a living organism, superimposed on the compression pressure PC1, PC2, and PC3 of the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26, respectively, by bandpass filtering when the compression pressure PC of the compression band 12 is maintained at step pressures P1, P2, P3, ..., Px in each constant compression pressure interval Tc during the slow decrease in pressure, based on the output signals from the first pressure sensor T1, the second pressure sensor T2, and the third pressure sensor T3, by bandpass filtering the pulse wave signals SM1, SM2, and SM3, respectively, which are waveforms of pressure fluctuations (AC components) synchronized with the heartbeat of a living organism.

[0038] Specifically, the output signals from the first pressure sensor T1, the second pressure sensor T2, and the third pressure sensor T3 are each subjected to a bandpass filter with a pass frequency of, for example, 0.5 Hz to 20 Hz, thereby sequentially extracting pulse wave signals SM1, SM2, and SM3 as the compression pressure decreases due to the compression zone 12. These pulse wave signals SM1, SM2, and SM3 are sequentially stored in a predetermined storage area such as RAM 74, corresponding to the compression pressure at the time of pulse wave generation for any of the step pressures P1, P2, P3, ... Px. The volume pulse wave extraction unit 84 extracts pulse wave signals SM1, SM2, and SM3 that have undergone trend removal processing as needed to reduce distortion in the waveform when the baseline is flat. The pulse wave signals SM1 and SM3, which represent the upstream and downstream volume pulse waves extracted by the volume pulse wave extraction unit 84, may each consist of a single waveform, but in this embodiment, they are each composed of two waveforms that are generated in sequence for each constant compression pressure interval Tc.

[0039] The diastolic blood pressure calculation unit 86 determines the diastolic blood pressure value DBP using a well-known diastolic blood pressure determination algorithm, for example, a so-called oscillometric diastolic blood pressure determination algorithm that determines the diastolic blood pressure value as the compression pressure of the pulse wave signal SM2 obtained sequentially as the compression pressure by the compression band 12 decreases, specifically the compression pressure at the point where the envelope connecting the peaks of the waveforms shows a sharp decline.

[0040] The systolic blood pressure value calculation unit 88 includes a cross-correlation coefficient calculation unit 90, a normalization processing unit 92, a difference value calculation unit 94, and a systolic blood pressure value determination unit 96.

[0041] As shown in Figure 7, the cross-correlation coefficient calculation unit 90 sequentially calculates the cross-correlation coefficient Φ(τ) between the pulse wave signal SM1 representing the upstream volume pulse wave and the pulse wave signal SM3 representing the downstream volume pulse wave for a predetermined number of beats generated in the same constant compression pressure interval Tc in the upstream inflation bag 22 and the downstream inflation bag 26, respectively, for each step pressure P1, P2, P3, ... Px from which the pulse wave signals SM1 and SM3 are extracted, using the following equation (1).

[0042] Φ(τ)=∫〔SM1(t)·SM3(t-τ)〕dt ··· (1) Φ(τ)n=Φ(τ) / (φ1·φ3) ··· (2) However, τ is a variable that represents the phase shift time (sec) between the upstream volume pulse wave represented by pulse wave signal SM1 and the downstream volume pulse wave represented by pulse wave signal SM3, which are used when calculating the cross-correlation coefficient. φ1 and φ3 indicate the magnitudes of the pulse wave signals (data) SM1 and SM3, respectively.

[0043] The normalization processing unit 92 normalizes the cross-correlation coefficient Φ(τ), which is sequentially calculated by the cross-correlation coefficient calculation unit 90, by the magnitudes φ1 and φ3 of the pulse wave signals SM1 and SM3, respectively, and converts it into a normalized cross-correlation coefficient Φ(τ)n with a maximum value of 1 using equation (2). Figure 8 shows the relationship between the normalized cross-correlation coefficient Φ(τ)n thus normalized and the step pressure, i.e., the compression pressure PC. The ● marks in Figure 8 indicate the normalized cross-correlation coefficient Φ(τ)n that changes as the compression pressure PC1 of the upstream inflation bag 22 decreases. As the compression pressure PC1 of the upstream inflation bag 22 decreases, that is, as you move from the right to the left on the horizontal axis of Figure 8, the normalized cross-correlation coefficient Φ(τ)n shows a low value in the step pressure section of the high-pressure region which is higher than the initial systolic blood pressure value SBP, but it increases sharply toward 1 when it reaches around the systolic blood pressure value SBP (120 mmHg).

[0044] The difference value calculation unit 94 sequentially calculates the difference value ΔΦ(τ)n, which represents the change in the normalized cross-correlation coefficient Φ(τ)n between the pulse wave signal SM1 representing the upstream volume pulse wave and the pulse wave signal SM3 representing the downstream volume pulse wave, which are sequentially calculated by the cross-correlation coefficient calculation unit 90 and normalized by the normalization processing unit 92. The difference value ΔΦ(τ)n is the difference between adjacent data points of the normalized cross-correlation coefficient Φ(τ)n for each step pressure. The × marks in Figure 9 indicate the difference value ΔΦ(τ)n of the normalized cross-correlation coefficient Φ(τ)n that changes as the compression pressure PC1 of the upstream inflation bag 22 decreases stepwise. The difference value ΔΦ(τ)n indicates the magnitude of the change in the normalized cross-correlation coefficient Φ(τ)n, and as the compression pressure PC1 of the upstream inflation bag 22 decreases, it shows the maximum value and maximum amplitude value around the systolic blood pressure value SBP (120 mmHg).

[0045] The systolic blood pressure determination unit 96 determines the maximum value among the difference values ​​ΔΦ(τ)n of the normalized cross-correlation coefficients sequentially calculated by the difference value calculation unit 94, and determines the systolic blood pressure SBP of the living body 14 based on the compression pressure PC applied to the compressed area of ​​the living body 14 by the compression band 12 when the maximum value occurs. Alternatively, the systolic blood pressure determination unit 96 determines the systolic blood pressure SBP of the living body 14 based on the compression pressure PC applied to the compressed area of ​​the living body 14 by the compression band 12 when the sequentially calculated normalized cross-correlation coefficient value exceeds a predetermined threshold of approximately 0.8 to 0.9, which in Figure 9 is a compression pressure of around 120 mmHg. Preferably, the determination threshold of the normalized cross-correlation coefficient is experimentally set in advance so that it can be determined that arterial blood flow has started at the time of the systolic blood pressure value.

[0046] The blood pressure value display output unit 98 displays the systolic blood pressure value SBP determined by the systolic blood pressure value determination unit 96 and the diastolic blood pressure value DBP calculated by the diastolic blood pressure value calculation unit 86 on the display device 78.

[0047] Figure 10 is a flowchart illustrating the main parts of the control operation of the electronic control unit 70, and Figure 11 is a flowchart illustrating in detail the contents of the systolic blood pressure value determination routine shown in S8 of Figure 10. In Figure 10, when the blood pressure measurement start operation button 80 is operated, in step S1 (hereinafter, "step" will be omitted) corresponding to the cuff pressure control unit 82, the compression pressure PC of the compression band 12 is increased. Specifically, as shown in Figure 6, the rapid exhaust valve 52 and the exhaust control valve 54 are closed, and the air pump 50 is activated, and the compressed air supplied from the air pump 50 rapidly increases the pressure inside the main piping 56 and the upstream inflation bag 22, intermediate inflation bag 24, and downstream inflation bag 26 connected thereto. Then, compression of the upper arm 16 by the compression band 12 is started.

[0048] Next, in S2, which corresponds to the cuff pressure control unit 82, it is determined whether the compression pressure PC of the compression band 12 is equal to or greater than a preset target pressure value PCM (for example, 180 mmHg, which is higher than the normal systolic blood pressure value of a living organism), based on the output signal of, for example, the fourth pressure sensor T4, which indicates the compression pressure PC of the compression band 12. In the section before time t2 in Figure 6, the determination in S2 is rejected, and steps S1 and below in Figure 10 are repeatedly executed.

[0049] When the compression pressure PC reaches the target pressure value PCM and the judgment in S2 is affirmed, in S3, which corresponds to the cuff pressure control unit 82, the operation of the air pump 50 is stopped, and the exhaust control valve 54, the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3 are activated at the timings shown in Figure 6 so that the compression pressure PC of the compression zone 12 is depressurized in steps, for example, every 2 to 5 mmHg / step, in which preset step pressures P1, P2, P3, ... Px are sequentially formed, and exhaust is slowly discharged at a constant average speed.

[0050] When the above step pressures P1, P2, P3, ... Px are maintained, the first on-off valve E1, the second on-off valve E2, and the third on-off valve E3 are closed, respectively. Time t2 in Figure 6 is the start of the slow exhaust, and between times t3 and t4, the compression pressure PC of the compression zone 12 is maintained at the step pressure P1 for a predetermined time, for example, two beats.

[0051] Next, in S4, which corresponds to the volume pulse wave extraction unit 84, while the compression pressures PC1, PC2, and PC3 are held for a predetermined time, the output signals from the first pressure sensor T1, the second pressure sensor T2, and the third pressure sensor T3 are subjected to, for example, bandpass filtering to discriminate signals in the wavelength band of 0.5 to 20 Hz, and, if necessary, trend removal processing to reduce distortion to the waveform when the baseline is flat. As a result, pulse wave signals SM1, SM2, and SM3, which represent the pulse waves from the upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26, are extracted. At the same time, the output signal from the fourth pressure sensor T4 is subjected to lowpass filtering to remove the AC component, thereby extracting the compression pressure PC of the compression band 12. These are then associated with each other and stored.

[0052] In S5, which corresponds to the cuff pressure control unit 82, it is determined whether the compression pressure PC is less than or equal to a preset measurement termination pressure value PCE (for example, 30 mmHg). Before time t11 in Figure 6, the determination in S5 is rejected, and steps S3 and below are repeatedly executed.

[0053] When the compression pressure PC becomes less than or equal to the measurement end pressure value PCE and the judgment in S5 is affirmed, in S6, which corresponds to the cuff pressure control unit 82, the rapid exhaust valve 52 is activated so that the pressure in the upstream inflation bag 22, the intermediate inflation bag 24, and the downstream inflation bag 26 is released to atmospheric pressure, and the upper arm 16 is released from compression by the compression band 12. Figure 6 shows this state from time t11 onwards.

[0054] Next, in S7, which corresponds to the diastolic blood pressure calculation unit 86, the point where the envelope connecting the peaks of the pulse wave signals SM2 obtained sequentially as the compression pressure by the compression band 12 decreases shows a sharp decline is determined, and the compression pressure corresponding to that sharp decline point is determined as the diastolic blood pressure value DBP.

[0055] Next, in the systolic blood pressure value determination routine S8, which corresponds to the systolic blood pressure value calculation unit 88, S81, which corresponds to the cross-correlation coefficient calculation unit 90 shown in Figure 11, S82, which corresponds to the normalization processing unit 92, S83, which corresponds to the difference value calculation unit 94, and S84, which corresponds to the systolic blood pressure value determination unit 96 are executed sequentially.

[0056] In S81, the cross-correlation coefficient Φ(τ) between the pulse wave signal SM1 representing the upstream volume pulse wave and the pulse wave signal SM3 representing the downstream volume pulse wave, which are generated in the same constant compression pressure interval Tc in the upstream inflation bag 22 and the downstream inflation bag 26, is calculated sequentially for each step pressure P1, P2, P3, ... Px from which the pulse wave signals SM1 and SM3 are extracted, using equation (1).

[0057] In S82, the cross-correlation coefficient Φ(τ) calculated sequentially in S81 is normalized by the magnitudes φ1 and φ3 of the pulse wave signals SM1 and SM3, respectively. From equation (2), the cross-correlation coefficient Φ(τ) is converted into a normalized cross-correlation coefficient Φ(τ)n with a maximum value of 1. Figure 8 shows the normalized cross-correlation coefficient Φ(τ)n after normalization.

[0058] In S83, the difference value ΔΦ(τ)n of the normalized cross-correlation coefficient Φ(τ)n between the pulse wave signal SM1, which is sequentially calculated in S81 and normalized in S82, and the pulse wave signal SM3, which is sequentially calculated as the × mark in Figure 9.

[0059] In S84, the maximum value among the difference values ​​ΔΦ(τ)n of the normalized cross-correlation coefficients calculated sequentially in S83 is determined, and the systolic blood pressure (SBP) of the body 14 is determined based on the compression pressure PC applied by the compression band 12 to the compressed area of ​​the body 14 when this maximum value occurs. Alternatively, the systolic blood pressure (SBP) of the body 14 is determined based on the compression pressure PC applied by the compression band 12 to the compressed area of ​​the body 14 when the sequentially calculated normalized cross-correlation coefficient exceeds a predetermined threshold of approximately 0.8 to 0.9 in Figure 9, which is a compression pressure of around 120 mmHg in Figure 9. Preferably, the determination threshold is experimentally set in advance so that it can be determined that arterial blood flow has actually started at the time of the systolic blood pressure value.

[0060] Returning to the main section of Figure 10, in S9, which corresponds to the blood pressure value display output unit 98, the diastolic blood pressure value DBP calculated in S7 and the systolic blood pressure value SBP calculated in S8 are displayed on the display device 78.

[0061] The inventors measured the systolic blood pressure (SBP) of 90 subjects using the auscultatory method, the oscillometric method, and the method according to this embodiment. The auscultatory method is a method in which the pressure of a compression band that compresses an artery is measured using a mercury pressure gauge, and the pressure value of the compression band is determined as the systolic blood pressure when the blood flow sound (Korotkoff sound) indicating the start of arterial blood flow is determined using a stethoscope. The oscillometric method is a method in which the compression pressure of a compression band is decreased from a value higher than the systolic blood pressure, and the compression pressure value at the point where the envelope connecting the peaks of the volume pulse wave obtained from the intermediate inflation bag 24 of the compression band 12 shows a rapid increase is determined as the systolic blood pressure.

[0062] Figure 12 shows the distribution of errors in systolic blood pressure values ​​measured by the oscillometric method compared to measurements taken by auscultation (true values). In this case, the mean error ME of systolic blood pressure values ​​measured by the oscillometric method compared to measurements taken by auscultation (true values) was -1.11, and the standard deviation SD was 4.39.

[0063] Figure 13 shows the distribution of errors in the systolic blood pressure values ​​measured by this embodiment compared to the values ​​measured by auscultation (true values). In this case, the mean error ME of the systolic blood pressure values ​​measured by this embodiment compared to the values ​​measured by auscultation (true values) was -0.59, and the standard deviation SD was 3.20.

[0064] As is clear from Figures 12 and 13, the systolic blood pressure values ​​measured by this embodiment have an average error that is about half that of the systolic blood pressure values ​​measured by the oscillometric method, and the standard deviation is reduced to about 72%. In other words, it has become clear that the measurement of systolic blood pressure values ​​by this embodiment has higher measurement accuracy than the measurement of systolic blood pressure values ​​by the oscillometric method.

[0065] As described above, according to the blood pressure measuring device 10 of this embodiment, the systolic blood pressure value SBP of the living body 14 is determined by the systolic blood pressure value calculation unit 88 based on the change in the cross-correlation coefficient Φ(τ) between the upstream volume pulse wave represented by pulse wave signal SM1 and the downstream volume pulse wave represented by pulse wave signal SM3, which is obtained sequentially during the process in which the compression pressure of the compression band 12 is lowered from a value higher than the living body's systolic blood pressure value. As a result, the change in the cross-correlation coefficient Φ(τ) between the upstream volume pulse wave and the downstream volume pulse wave indicates that blood flow in the artery that was occluded by the compression band 14 has actually started, and is not affected by the living body's unique characteristics which differ for each person being measured, such as vascular compliance, pulse rate, pulse pressure value, and blood pressure value, thus improving the accuracy of determining the living body's systolic blood pressure value SBP.

[0066] Furthermore, according to the blood pressure measuring device 10 of this embodiment, the systolic blood pressure calculation unit 88 includes a difference value calculation unit 94 that sequentially calculates the difference value ΔΦ(τ)n of the normalized cross-correlation coefficient Φ(τ)n between the upstream volume pulse wave and the downstream volume pulse wave, which are sequentially calculated by the cross-correlation coefficient calculation unit 90 and the normalization processing unit 92, and a systolic blood pressure determination unit 96 that determines the systolic blood pressure value SBP of the living body 14 based on the compression pressure PC applied to the upper arm (compressed area 16) of the living body 14 by the compression band 12 when the maximum value of the difference value ΔΦ(τ)n of the normalized cross-correlation coefficient Φ(τ)n calculated sequentially by the difference value calculation unit 94 occurs. As a result, the difference value ΔΦ(τ)n of the normalized cross-correlation coefficient Φ(τ)n emphasizes the change in the normalized cross-correlation coefficient Φ(τ)n, so the accuracy of determining the systolic blood pressure value SBP of the living body 14 is further improved.

[0067] Furthermore, according to the blood pressure measuring device 10 of this embodiment, the systolic blood pressure value calculation unit 88 includes a normalization processing unit 92 that converts the cross-correlation coefficient Φ(τ) between the upstream volume pulse wave and the downstream volume pulse wave, which are sequentially calculated by the cross-correlation coefficient calculation unit 90, into a normalized cross-correlation Φ(τ)n, which is normalized so that its maximum value is 1. As a result, the determination of the systolic blood pressure value SBP using the normalized cross-correlation Φ(τ)n is not affected by the magnitude of the absolute value of the cross-correlation coefficient Φ(τ), thus further improving the accuracy of determining the systolic blood pressure value SBP of the living body 14.

[0068] Furthermore, according to the blood pressure measuring device 10 of this embodiment, the compression band 12 lowers the compression pressure PC applied to the upper arm (compression site) 16 from a value higher than the systolic blood pressure value of the body 14 by repeatedly performing a constant compression pressure section Tc in which the compression pressure is kept constant, and a change in compression pressure section Td in which the compression pressure is changed within the constant compression pressure section Tc. The volume pulse wave extraction unit 84 sequentially extracts a pulse wave signal SM1 representing the upstream volume pulse wave, which is a pressure oscillation synchronized with the heartbeat of the body, and a pulse wave signal SM3 representing the downstream volume pulse wave, during the constant compression pressure section Tc. As a result, distortion originating from the decrease (change) in compression pressure PC is suppressed in the waveforms of the upstream volume pulse wave represented by pulse wave signal SM1 and the downstream volume pulse wave represented by pulse wave signal SM3 extracted by the volume pulse wave extraction unit 84, thereby further improving the accuracy of determining the systolic blood pressure value SBP of the body 14.

[0069] Furthermore, according to the blood pressure measuring device 10 of this embodiment, the systolic blood pressure value calculation unit 88 includes a systolic blood pressure value determination unit 96 that determines the systolic blood pressure value SAP based on the compression pressure PC applied by the compression band 12 when the normalized cross-correlation coefficient Φ(τ)n, which is sequentially calculated by the cross-correlation coefficient calculation unit 90 and normalized by the normalization processing unit 92, exceeds a preset determination threshold. As a result, the systolic blood pressure value SAP is determined based on the change in the cross-correlation coefficient Φ(τ)n, which indicates that blood flow in the artery that was occluded by the compression band 12 has actually started, thereby improving the accuracy of determining the systolic blood pressure value SAP in the living body.

[0070] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is not limited to this embodiment and can be implemented in other forms.

[0071] For example, in Figure 10 of the above-described embodiment, pulse wave signals SM1, SM2, and SM3 were read while the compression pressure on the upper arm 16 by the compression band 12 reached the measurement end pressure value PCE, and thereafter, S7 for determining the diastolic blood pressure value and S8 for determining the systolic blood pressure value were performed. However, for example, the processing of steps S7 and S8 may be performed sequentially in real time while step pressures P1, P2, P3, ... Px are being formed.

[0072] Furthermore, although the compression band 12 used in the above-described embodiment was equipped with three upstream inflation bags 22, an intermediate inflation bag 24, and a downstream inflation bag 26, it may also be equipped with, for example, two upstream inflation bags 22 and a downstream inflation bag 26, or it may be equipped with four or more inflation bags.

[0073] Furthermore, in the above-described embodiment, the compression pressure PC applied to the upper arm 16 by the compression band 12 may be the compression pressure PC1 in the upstream inflation bag 22, the compression pressure PC2 in the intermediate inflation bag 24, the compression pressure PC3 in the downstream inflation bag 26, or the average pressure thereof.

[0074] Furthermore, although the compression band 12 in the above-described embodiment compressed the upper arm 16, it may also compress a part of the living body 14, such as the wrist or lower limb.

[0075] Furthermore, although the compression band 12 in the above-described embodiment employed step-by-step pressure reduction during blood pressure measurement, continuous pressure reduction, where the compression pressure PC is continuously changed, may also be used.

[0076] Furthermore, although the compression band 12 in the above-described embodiment employed step-down pressure reduction when measuring blood pressure, step-up pressure reduction, where the compression pressure PC is increased in steps, or continuous pressure reduction, where the pressure is increased continuously, may also be used.

[0077] It should be noted that the above is merely one embodiment, and although other examples are not provided, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit. [Explanation of Symbols]

[0078] 10: Blood pressure measuring device 12: Compression bandage 14: Living organisms 16: Upper arm (area of ​​compression) 18: Artery 22: Upstream inflation bag 24: Intermediate inflation bag 26: Downstream inflation bag 82: Cuff pressure control unit 84: Volume pulse wave extraction unit 86: Minimum blood pressure calculation unit 88: Maximum blood pressure calculation unit 90: Cross-correlation coefficient calculation unit 92: Normalization Processing Unit 94: Difference Value Calculation Unit 96: Maximum blood pressure determination unit SBP: Systolic blood pressure DBP: Diastolic blood pressure PC: Compression pressure of the compression band PC1: Compression pressure inside the upstream inflation bag PC3: Compression pressure inside the downstream inflation bag PCM: Target pressure value for increasing pressure SM1: Pulse wave signal (upstream volume pulse wave) SM3: Pulse wave signal (downstream volume pulse wave) Φ(τ): Cross-correlation coefficient Φ(τ)n: Normalized cross-correlation coefficient

Claims

1. A blood pressure measuring device comprising a compression band that is wrapped around a compressed area of ​​a living body and has independent upstream and downstream inflation bags that compress different compressed areas along the long axis of the arteries within the living body, and the upstream and downstream inflation bags compress the arterial blood vessels within the compressed area with the same compression pressure, A volume pulse wave extraction unit sequentially extracts upstream volume pulse waves and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body, contained in the compression pressure in the upstream and downstream inflation bags, respectively, during the process of decreasing the compression pressure on the compressed area by the compression band from a value higher than the systolic blood pressure of the living body, A cross-correlation coefficient calculation unit sequentially calculates the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave sequentially extracted by the volume pulse wave extraction unit, The system includes a systolic blood pressure calculation unit that calculates the systolic blood pressure value of the living organism based on the change in the cross-correlation coefficient calculated sequentially by the cross-correlation coefficient calculation unit, The aforementioned systolic blood pressure value calculation unit, A normalization processing unit converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which has been sequentially calculated by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that has been normalized so that its maximum value is 1. A difference value calculation unit that sequentially calculates the difference values ​​of the normalized cross-correlation coefficients, The system includes a maximum blood pressure determination unit that determines the maximum blood pressure of the living body based on the compression pressure applied to the compressed area of ​​the living body by the compression band when the maximum value of the difference in the normalized cross-correlation coefficients, which is sequentially calculated by the difference value calculation unit, occurs. A blood pressure measuring device characterized by the following features.

2. The compression band reduces the compression pressure on the area to be compressed from a value higher than the systolic blood pressure of the living body by repeatedly alternating between a constant compression pressure section in which the compression pressure is maintained at a constant level and a variable compression pressure section in which the compression pressure is changed between the constant compression pressure sections. The volume pulse wave extraction unit sequentially extracts the upstream and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living organism, within the constant compression pressure interval. A blood pressure measuring device according to feature 1.

3. A blood pressure measuring device comprising a compression band that is wrapped around a compressed area of ​​a living body and has independent upstream and downstream inflation bags that compress different compressed areas in the longitudinal direction of the arteries within the living body, wherein the upstream and downstream inflation bags compress the arterial blood vessels within the compressed area with the same compression pressure, A volume pulse wave extraction unit sequentially extracts upstream volume pulse waves and downstream volume pulse waves, which are pressure oscillations synchronized with the heartbeat of the living body, contained in the compression pressure in the upstream and downstream inflation bags, respectively, during the process of decreasing the compression pressure on the compressed area by the compression band from a value higher than the systolic blood pressure of the living body, A cross-correlation coefficient calculation unit sequentially calculates the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave sequentially extracted by the volume pulse wave extraction unit, The system includes a systolic blood pressure calculation unit that calculates the systolic blood pressure value of the living organism based on the change in the cross-correlation coefficient calculated sequentially by the cross-correlation coefficient calculation unit, The aforementioned systolic blood pressure value calculation unit, A normalization processing unit converts the cross-correlation coefficient between the upstream volume pulse wave and the downstream volume pulse wave, which has been sequentially calculated by the cross-correlation coefficient calculation unit, into a normalized cross-correlation coefficient that has been normalized so that its maximum value is 1. The unit includes a systolic blood pressure determination unit that determines the systolic blood pressure value based on the compression pressure applied to the compressed area of ​​the body by the compression band when the normalized cross-correlation coefficient exceeds a preset determination threshold. A blood pressure measuring device characterized by the following features.

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