JP2011182969A - Blood pressure information measuring instrument and method of computing index of extent of arteriosclerosis by the instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure blood pressure information permitting an accurate decision to be made about the extent of arteriosclerosis. <P>SOLUTION: The measuring instrument computes a secondary differential curve of the waveform of an input pulse wave and specifies a point Pinf on the waveform corresponding to a local maximum point (S103 and 105) as a process for extracting a feature point showing the appearance point of a necessary reflection wave to compute Tr as an index of the extent of arteriosclerosis from the waveform of the pulse wave and computes a quartic differential curve and specifies a point Psho on the waveform corresponding to a descending zero crossing point (S107 and 109). When a person to be measured is 60 years old or older (YES at S111), the point Psho is adopted as the feature point and Tr is computed (S113). When the person is younger than 60 years old (NO at S111), the point Pinf is adopted as the feature point and Tr is computed (S115). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a blood pressure information measuring apparatus and a method for calculating an index of arteriosclerosis in the apparatus, and in particular, a blood pressure information measuring apparatus for measuring blood pressure information effective for determination of the arteriosclerosis degree, The present invention relates to an index calculation method.

  Conventionally, as a device for determining the degree of arteriosclerosis, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-316821 (Patent Document 1), the speed of propagation of a pulse wave ejected from the heart (hereinafter, PWV: There is a device to check (Pulse Wave Velocity). The PWV is equipped with cuffs or the like that measure pulse waves at at least two locations such as the upper arm and lower limbs, and simultaneously measures the pulse waves, so that the appearance time difference between the pulse waves at each position and the cuff that measures the pulse waves are measured. It is calculated from the length of the artery between the two points to which etc. are mounted. For this reason, it is necessary to attach cuffs or the like to at least two places, and there is a problem that it is difficult to easily measure PWV at home.

  As a technique for determining the degree of arteriosclerosis only from the pulse wave of the upper arm, Japanese Patent Application Laid-Open No. 2004-113593 (Patent Document 2) discloses a measurement device including a pulse wave measurement cuff and a compression cuff that compresses the distal side. The technique used and determined is disclosed. This technique measures the pulse wave on the central (heart) side while compressing the peripheral side, and the ejection wave ejected from the heart and the reflected wave from the iliac bifurcation and the stiffening site in the artery And the degree of arteriosclerosis is determined based on an index such as an amplitude difference between the ejection wave and the reflected wave, an amplitude ratio, or an appearance time difference.

JP 2000-316821 A JP 2004-113593 A

  The technique disclosed in Patent Document 2 has a problem that the determination accuracy of the degree of arteriosclerosis cannot be ensured unless the start point of the reflected wave appearing in the pulse wave is accurately detected.

  The present invention has been made in view of such a problem, and is a blood pressure information measuring device for measuring blood pressure information capable of accurately determining the degree of arteriosclerosis, and a method for calculating an index of arteriosclerosis in the device. The purpose is to provide.

  In order to achieve the above object, according to one aspect of the present invention, the blood pressure information measurement device is a blood pressure information measurement device that calculates an index of the degree of arteriosclerosis of a measurement subject as blood pressure information, and includes: A first sensor for detecting the internal pressure of the first air bag as blood pressure information, and an arithmetic means for calculating an index of the degree of arteriosclerosis based on a change in the internal pressure of the first air bag. The means includes a reflected wave start point from among a plurality of points on the internal pressure change curve of the first air bag attached to the measurement site of the measurement subject in the state where the peripheral side is driven based on information on the measurement subject. And calculating means for calculating an index of the degree of arteriosclerosis using the specified feature point.

  Preferably, the information on the measurement subject is at least one of the age of the measurement subject and the maximum blood pressure value.

  Preferably, the calculation means is a determination means for determining which point among the plurality of points on the internal pressure change curve corresponding to each of the plurality of candidates obtained from the differential curve of the internal pressure change curve is a feature point. Further included.

  Preferably, the plurality of candidates obtained from the differential curve include a maximum point of the secondary differential curve and a descending zero cross point of the quaternary differential curve.

  Preferably, the calculated index of arteriosclerosis includes a difference in appearance time between the ejection wave and the reflected wave in the pulse wave waveform of one beat.

  Preferably, the blood pressure information measuring device further includes a second air bag and a second sensor for detecting the internal pressure of the second air bag as blood pressure information, and the computing means changes the internal pressure of the first air bag. Instead, the first air bag is attached to the measurement site such that the first air bag is located on the distal side of the measurement site and the second air bag is located on the central side of the measurement site. An index of the degree of arteriosclerosis is calculated based on the change in the internal pressure of the second air bag when the peripheral side is driven by pressing.

  According to another aspect of the present invention, a method for calculating an index of arteriosclerosis includes an air bag, a sensor for detecting the internal pressure of the air bag as blood pressure information, and the degree of arteriosclerosis based on a change in the internal pressure of the air bag. A method for calculating an index of arteriosclerosis in a blood pressure information measuring device comprising a calculation means for calculating an index, wherein the measured subject is in a state in which the peripheral side is driven based on the attribute of the measured person. A step of identifying a feature point representing a reflected wave start point from a plurality of points on an internal pressure change curve of an air bag attached to a measurement site, and calculating an index of arteriosclerosis using the identified feature point Steps.

  According to the present invention, the start point of the reflected wave can be detected from the pulse waveform with higher accuracy, and as a result, the degree of arteriosclerosis can be determined more accurately than in the past.

It is a perspective view which shows the specific example of the external appearance of the measuring apparatus concerning embodiment. It is a schematic cross section which shows the specific example of the measurement attitude | position at the time of measuring blood pressure information using a measuring apparatus, and the structure of an armband. It is a figure explaining the relationship between the parameter | index for determining an arteriosclerosis degree, and a pulse wave waveform. It is a figure which shows the relationship between a pulse wave waveform, its secondary differential curve, and its quaternary differential curve. It is a figure showing the relationship between Tr calculated by each of two types of feature point candidates and pulse wave propagation time for the measured pulse wave. It is a figure which shows the relationship between the specific example of the pulse-wave waveform in which the inflection point appeared clearly, its 2nd derivative curve, and its 4th derivative curve. It is a figure which shows the relationship between the specific example of the pulse wave waveform whose inflection point is unclear, its secondary differential curve, and its quaternary differential curve. It is a figure showing the relationship between Tr calculated using the feature point according to the age of a to-be-measured person, and pulse wave propagation time about the measured pulse wave. It is a figure showing the relationship between Tr calculated using the feature point according to the maximum blood pressure value, and pulse wave propagation time about the measured pulse wave. It is a figure showing the functional block of a measuring device. It is a flowchart which shows the specific example of operation | movement with a measuring apparatus. 12 is a flowchart illustrating a specific example of an operation for extracting feature points during the operation of FIG. It is a figure which shows the pressure change in each air bag during operation | movement with a measuring apparatus. It is a figure which shows the specific example of the correlation with the appearance time difference Tr and PWV between an ejection wave and a reflected wave.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

  Referring to FIG. 1, a blood pressure information measuring device (hereinafter abbreviated as a measuring device) 1 according to an embodiment is connected to a base 2 and an arm band 9 that is connected to the base 2 and is attached to an upper arm that is a measurement site. These are connected by an air tube 10. On the front surface of the substrate 2, a display unit 4 that displays various information including measurement results and an operation unit 3 that is operated to give various instructions to the measuring apparatus 1 are arranged. The operation unit 3 includes a switch 31 that is operated to turn on / off the power source and a switch 32 that is operated to instruct the start of measurement.

  2A and 2B, the armband 9 includes an air bag as a fluid bag for compressing the living body. The air bag includes an air bag 13A that is a fluid bag used to measure blood pressure as blood pressure information, and an air bag 13B that is a fluid bag used to measure pulse waves as blood pressure information. The size of the air bag 13B is, for example, about 20 mm × 200 mm. Preferably, the air capacity of the air bag 13B is 1/5 or less compared to the air capacity of the air bag 13A.

  When measuring the pulse wave using the measuring apparatus 1, as shown in FIG. 2A, the arm band 9 is wound around the upper arm 100 which is a measurement site. By pressing the switch 32 in this state, blood pressure information is measured, and an index for determining the degree of arteriosclerosis is calculated based on the blood pressure information. Here, “blood pressure information” refers to information related to blood pressure obtained by measurement from a living body, and specifically corresponds to a blood pressure value, a pulse wave waveform, a heart rate, and the like.

  One of the indexes for determining the degree of arteriosclerosis is Tr (Traveling time to reflected wave). Tr is represented by a time interval between the appearance time of the ejection wave and the appearance time of the reflected wave in which the traveling wave is reflected back from the bifurcation of the iliac artery. In FIG. 3, it is represented by the time interval from the rising point of the ejection wave to the inflection point representing the rising point of the reflected wave. When the measurement site is the upper arm and the reflected wave is a reflected wave from the ankle as the periphery, the correlation between the time difference Tr and PWV can be statistically obtained by obtaining individual parameters such as height and sex, for example, London GM As shown in FIG. 14 described in a paper published in “Hypertension” (1992 Jul; 20 (1): 10-19.). Therefore, the appearance time difference Tr between the ejection wave and the reflected wave can be used as an index for determining the degree of arteriosclerosis.

  As shown in FIG. 3, in order to obtain Tr as an index for determining the degree of arteriosclerosis from the measured pulse wave, it is necessary to accurately detect the start point of the reflected wave from the measured pulse wave. . As a method for this purpose, the applicant of the present application has already disclosed a method for detecting a feature point appearing in a differential curve of a pulse wave as a start point of a reflected wave in Japanese Patent Application Laid-Open No. 2004-195204.

  However, as shown in Segers P et al. “Physiological Measurement” (2007 28 (9): 1045-56 Assessment of pressure wave reflection: getting the timing right!) It is known that there are a plurality of candidate feature points that can be considered as points. Specifically, in the pulse wave waveform represented by the waveform A in FIG. 4, the vicinity of the inflection point seen from the rise to the notch is considered as the starting point of the reflected wave. The candidate characteristic points of the differential curve corresponding to this point of the pulse wave include a point Pinf corresponding to the maximum point of the secondary differential curve represented by the curve B and a descending zero crossing point of the quaternary differential curve represented by the curve B. There is a point Psho corresponding to.

  When the inventors measured the pulse wave for about 100 subjects and calculated Tr using each of the above-described points Pinf and Psho, it is shown in FIG. 5 between the pulse wave propagation time. A relationship was obtained. That is, from the result of FIG. 5, the Tr and the pulse wave propagation time obtained at the point Pinf and the Tr and the pulse wave propagation time obtained at the point Psho are both highly correlated. It was also verified that this is a valid starting point for the reflected wave.

  However, from the results of FIG. 5, it is verified that there is data with large errors in the region where the pulse wave propagation time is short for both Tr obtained at the point Pinf and Tr obtained at the point Psho. It was. Further, in the region where the pulse wave propagation time is short, the Tr obtained at the point Pinf is more deviated from the approximate straight line obtained in relation to the pulse wave propagation time than the Tr obtained at the point Psho. It was also verified that it existed.

  The following reasons can be considered as this reason. That is, the inflection point clearly appears in the waveform having a long pulse wave propagation time as shown in the waveform A in FIG. In this pulse wave, as represented by the curve B, the secondary differential curve also has a clear maximum point. Therefore, the reflection start point can be correctly detected by the point Pinf.

  On the other hand, the inflection point becomes unclear as shown in the waveform A of FIG. In this pulse wave, the maximum point of the second derivative curve becomes unclear as represented by curve B. Therefore, there is a high possibility that the point Pinf does not correctly reflect the reflection start point. In this case, it is considered that the point Psho is more likely to be a suitable reflection start point than the point Pinf.

  A characteristic of the pulse waveform is that the older the age and the higher the blood pressure, the larger the reflected wave amplitude and the shorter the arrival time. Therefore, the inflection point is unclear as shown in waveform A in FIG. There tends to be a pulse wave shape. Therefore, the inventors of the present application have confirmed that it is possible to determine which of the point Pinf and the point Psho is appropriate as a feature point using information such as the age and blood pressure of the subject based on the above-described verification results. Therefore, Tr was calculated using the point Psho when the age of the subject was 60 years or older, and using the point Pinf when the subject was younger than 60 years. Moreover, Tr was calculated using the point Psho when the subject's systolic blood pressure was 135 mmHg or more, and using the point Pinf when the subject's maximum blood pressure was less than 135 mmHg.

  As a calculation result, FIG. 8 shows Tr and pulse calculated using the point Psho when the subject's age is 60 years old or older and using the point Pinf when the subject is under 60 years old. FIG. 9 shows the relationship with the wave propagation time, and FIG. 9 uses the point Psho when the subject's systolic blood pressure is 135 mmHg or more and the point Pinf when the subject's systolic blood pressure is less than 135 mmHg. The relationship between the calculated Tr and the pulse wave propagation time is shown. 8 and FIG. 9 and the result of FIG. 5, both the results of FIG. 8 and the result of FIG. 9 have a higher correlation between the pulse wave propagation time and Tr than the result of FIG. It can be seen that is decreasing. Thus, it was verified that feature points to be adopted can be selected using information such as the age and blood pressure of the subject.

  The functional block of the measuring apparatus 1 for calculating an index of the degree of arteriosclerosis by selecting feature points to be adopted using information such as the age and blood pressure of the subject based on the verification results described above with reference to FIG. explain. Referring to FIG. 10, measuring apparatus 1 includes an air system 20A connected to air bag 13A through air tube 10, an air system 20B connected to air bag 13B through air tube 10, and a CPU ( Central Processing Unit) 40. The air system 20A includes an air pump 21A, an air valve 22A, and a pressure sensor 23A. The air system 20B includes an air valve 22B and a pressure sensor 23B.

  The air pump 21A is connected to the drive circuit 26A, and the drive circuit 26A is further connected to the CPU 40. The air pump 21A is driven by a drive circuit 26A that has received a command from the CPU 40, and pressurizes the air bag 13A by sending compressed gas into the air bag 13A.

  The air valve 22A is connected to the drive circuit 27A, and the drive circuit 27A is further connected to the CPU 40. The air valve 22B is connected to the drive circuit 27B, and the drive circuit 27B is further connected to the CPU 40. The open / close states of the air valves 22A and 22B are controlled by drive circuits 27A and 27B, respectively, which have received a command from the CPU 40. By controlling the open / close state, the air valves 22A and 22B maintain or depressurize the pressure in the air bags 13A and 13B, respectively. Thereby, the pressure in air bag 13A, 13B is controlled.

  The pressure sensor 23A is connected to an amplifier 28A, the amplifier 28A is further connected to an A / D converter 29A, and the A / D converter 29A is further connected to the CPU 40. The pressure sensor 23B is connected to the amplifier 28B, the amplifier 28B is further connected to the A / D converter 29B, and the A / D converter 29B is further connected to the CPU 40. The pressure sensors 23A and 23B detect pressures in the air bags 13A and 13B, respectively, and output signals corresponding to the detected values to the amplifiers 28A and 28B. The output signals are amplified by the amplifiers 28A and 28B, digitized by the A / D converters 29A and 29B, and then input to the CPU 40.

  The air tube from the air bag 13 </ b> A and the air tube from the air bag 13 </ b> B are connected by a two-port valve 51. The 2-port valve 51 is connected to the drive circuit 53, and the drive circuit 53 is further connected to the CPU 40. The 2-port valve 51 has a valve on the air bag 13A side and a valve on the air bag 13B side, and these valves open and close by being driven by a drive circuit 53 that receives a command from the CPU 40.

  The memory 41 stores a program executed by the CPU 40. The CPU 40 reads out and executes a program from the memory 41 based on a command input to the operation unit 3 provided on the base 2 of the measuring apparatus, and outputs a control signal according to the execution. Further, the CPU 40 outputs the measurement result to the display unit 4 and the memory 41. In addition to storing the measurement results, the memory 41 stores information about the measurer including at least the age as required. And CPU40 reads the information regarding the said measurer with the execution of a program as needed, and uses it for a calculation.

  As a function for calculating an index of the degree of arteriosclerosis, the CPU 40 performs a secondary differential operation on the pulse wave waveform and specifies a point Pinf from its maximum point, and the pulse wave waveform includes four values. A fourth-order differential calculation unit 402 for performing a second-order differential operation and identifying the point Psho from the descending zero-cross point, a determination unit 403 for determining which of the point Pinf and the point Psho is used as a feature point, and a feature An index calculation unit 404 for calculating an index of the degree of arteriosclerosis based on the points is included. These are functions mainly formed in the CPU 40 when the CPU 40 reads out and executes a program stored in the memory 41 in accordance with an operation signal from the operation unit 3, but at least some of these functions have a hardware configuration. May be formed.

  The operation of the measurement apparatus 1 will be described using the flowchart of FIG. The operation shown in FIG. 11 is started when the measurer presses the switch 32. This operation is realized by the CPU 40 reading a program stored in the memory 41 and controlling each unit shown in FIG. Moreover, the pressure change in air bag 13A, 13B in operation | movement with the measuring apparatus 1 is demonstrated using FIG. FIG. 13A shows the time change of the pressure P1 in the air bag 13B, and FIG. 13B shows the time change of the pressure P2 in the air bag 13A. S3 to S17 attached to the time axis in FIGS. 13A and 13B coincide with each operation of the measurement operation in the measurement apparatus 1 described later.

  Referring to FIG. 11, when the operation starts, each part is initialized in CPU 40 in step S1. In step S3, the CPU 40 outputs a control signal to the air system 20A to start pressurization of the air bag 13A, and measures blood pressure in the pressurization process. The blood pressure in step S3 is measured by an oscillometric method that is performed with a normal sphygmomanometer.

  When the blood pressure measurement in step S3 is completed, the CPU 40 outputs a control signal to the drive circuit 53 in step S5 to open both the air bag 13A side valve and the air bag 13B side valve of the 2-port valve 51. . As a result, the air bag 13A and the air bag 13B communicate with each other, a part of the air in the air bag 13A moves to the air bag 13B, and the air bag 13B is pressurized.

  In the example of FIG. 13A, the pressure P2 in the air bladder 13A increases to a pressure higher than the maximum blood pressure value from the start of pressurization in step S3 until the blood pressure measurement is completed. Thereafter, when the valve of the 2-port valve 51 is opened in step S5, part of the air in the air bag 13A moves to the air bag 13B, and the pressure P2 decreases. At the same time, as shown in FIG. 13B, the pressure P1 in the air bladder 13B rapidly increases. When the pressure P1 and the pressure P2 coincide, that is, when the internal pressures of the air bags 13A and 13B change, the movement of air from the air bag 13A to the air bag 13B ends. In step S7, the CPU 40 outputs a control signal to the drive circuit 53 at this time, and closes both valves of the 2-port valve 51 opened in step S5. In FIGS. 13A and 13B, it is shown that the pressure P1 and the pressure P2 match at the time of step S7. As shown in FIG. 2A, since the capacity of the air bag 13B is smaller than the capacity of the air bag 13A, the decrease in the pressure P2 in step S5 is not significant, and the pressure P1 at the time of step S7. The pressure P2 is higher than the maximum blood pressure value.

  Thereafter, in step S9, the CPU 40 outputs a control signal to the drive circuit 27B, and adjusts the pressure P1 in the air bladder 13B to a pressure suitable for measuring the pulse wave. The decompression adjustment amount here is preferably about 5.5 mmHg / sec, for example. Moreover, as a pressure suitable for measuring a pulse wave, about 50-150 mmHg is suitable. At this time, since both valves of the 2-port valve 51 are closed, as shown in FIG. 13B, the pressure P2 in the air bag 13A is higher than the maximum blood pressure value at the peripheral side of the measurement site. It is under pressure and is in a state of thrush.

  In a state where the peripheral side is driven, the CPU 40 extracts a feature point from the pulse wave waveform every time a pulse wave waveform for one beat based on the pressure signal from the pressure sensor 23B is input in step S11. Perform the action. Referring to the flowchart of FIG. 12 in detail, in step S101, the second derivative calculation unit 401 and the fourth derivative calculation unit 402 accept the input of the pulse waveform based on the pressure signal from the pressure sensor 23B, respectively, Differentiation processing and fourth-order differentiation processing are performed (steps S103 and S107). In step S105, the secondary differential calculation unit 401 specifies a point Pinf in the pulse wave waveform from the local maximum point of the secondary differential curve obtained as a result of the secondary differential processing. In step S109, the fourth derivative calculation unit 402 specifies a point Psho in the pulse waveform from the descending zero cross point of the fourth derivative curve obtained as a result of the fourth derivative process. The order of these operations may be reversed or may be performed in parallel.

  The determination unit 403 reads information about the measured person specified by the operation signal from the operation unit 3 from the memory 41, and includes the age of the measured person in the information and a threshold value stored in advance (for example, 60 years old). ) To determine whether to use a point Pinf or a point Psho as a feature point. As a result of the comparison, when the age of the person to be measured is 60 years or more which is a threshold value (YES in step S111), the determination unit 403 uses the point Psho specified in step S109 as a feature point in step S113 Judge. If the age of the measurement subject is less than the threshold value of 60 years (NO in step S111), the determination unit 403 determines in step S115 that the point Pinf specified in step S105 is used as the feature point.

  The operation of extracting the feature points in step S11 is a pulse wave for one beat until the number of feature points (for example, for 10 beats) necessary for calculating a predetermined index of arteriosclerosis is extracted. Repeated every time a waveform is input. Meanwhile, the pressure P1 in the air bladder 13B is maintained at a pressure suitable for measuring a pulse wave as shown in FIG. 13A, and the pressure P2 in the air bladder 13A is maintained in FIG. As shown, the pressure is maintained higher than the maximum blood pressure value. Thereby, the peripheral blood-feeding state of the measurement site is maintained.

  When the number of extracted feature points reaches a predetermined number (for example, 10 beats) (YES in step S13), in step S15, the index calculation unit 404 uses the average value of the extracted feature points. Tr or the like as an index of the degree of arteriosclerosis is calculated. In step S17, the CPU 40 outputs a control signal to the drive circuits 27A and 27B to open the air valves 22A and 20B, thereby releasing the pressure in the air bags 13A and 13B to atmospheric pressure. In the example of FIGS. 13A and 13B, the pressures P1 and P2 rapidly decrease to atmospheric pressure in the section of step S17.

  The calculated systolic blood pressure value (SYS), diastolic blood pressure value (DIA), arteriosclerosis index, and measurement results such as the measured pulse wave are displayed on the display unit 4 provided on the base 2. Applied and displayed.

  As described above, the measuring apparatus 1 uses the point Psho as the feature point when the age of the person to be measured is higher than the threshold value, and uses the point Pinf as the feature point when the age is lower than the threshold value. A degree indicator is calculated. Thus, as described with reference to FIGS. 8 and 5, it is possible to detect the start point of the reflected wave with higher accuracy than when the point Psho or the point Pinf is uniformly used regardless of the age. become. As a result, Tr as an index of the degree of arteriosclerosis is calculated with high accuracy, and the degree of arteriosclerosis can be determined with higher accuracy than before.

[Modification 1]
In the above example, the determination unit 403 determines whether to use the point Pinf or the point Psho as the feature point based on the comparison between the age of the person to be measured and the threshold value. The calculated systolic blood pressure value is compared with a prestored blood pressure value (for example, 135 mmHg). If the systolic blood pressure value is 135 mmHg or more, the point Psho is used, and if it is less than 135 mmHg, the point Pinf is used. You may make it judge that it uses.

  Even in this case, as described with reference to FIGS. 9 and 5, the start point of the reflected wave can be set with higher accuracy than when the point Psho or the point Pinf is used uniformly regardless of the systolic blood pressure value. It becomes possible to detect. As a result, Tr as an index of the degree of arteriosclerosis is calculated with high accuracy, and the degree of arteriosclerosis can be determined with higher accuracy than before.

  Further, a threshold value for the combination of the age of the person to be measured and the maximum blood pressure value is stored in advance in a table format, for example, and the age of the person to be measured and the calculated maximum blood pressure value are compared with the threshold value. Based on the above, it may be determined which of the point Pinf and the point Psho is used as the feature point.

  Even in this case, it is possible to detect the start point of the reflected wave with higher accuracy than when the point Psho or the point Pinf is used uniformly regardless of the age and the maximum blood pressure value of the measurement subject. As a result, Tr as an index of the degree of arteriosclerosis is calculated with high accuracy, and the degree of arteriosclerosis can be determined with higher accuracy than before.

[Modification 2]
In the above example, in the operation of calculating the feature point in step S11, it is determined which one is used as the feature point after the point Pinf and the point Psho of the pulse wave waveform input in steps S103 to S109 are specified. However, prior to the operation for specifying the feature point, it is determined which of the point Pinf and the point Psho is used as the feature point, and only the necessary points of the point Pinf and the point Psho are specified based on the determination. You may be made to do. Specifically, in the case of the example in FIG. 12, the age of the person to be measured and the threshold value of 60 years old are compared in advance, and if the age of the person to be measured is less than 60 years old, a second derivative curve is calculated and the point The operation up to specifying Pinf is performed, and the operation of calculating the fourth derivative curve may not be performed. The reverse is also true.

  By doing so, the processing can be simplified, and the operation time for calculating the feature points can be shortened.

  In the above description, as shown in FIG. 2 (A), FIG. 2 (B), FIG. 10 and the like, the armband 9 includes two air bags 13A and 13B, which are shown in FIG. As described above, the pulse wave waveform is based on the change in the internal pressure of the central air bag 13B when the peripheral air bag 13A is in a blood-feeding state by compressing the measurement site with a pressure higher than the maximum blood pressure value. Has been measured. However, the measurement of the pulse wave waveform is not limited to such an example. That is, the central air bag 13B is not provided, and the pulse wave waveform may be measured based on a change in internal pressure of a single air bag pressed against a measurement site such as the upper arm.

  When the pulse wave waveform is measured based on the change in the internal pressure of a single air bag, the CPU 40 pressurizes the air bag to a maximum blood pressure value or more to bring the measurement site into a blood-feeding state, and then changes the internal pressure. Based on this, the pulse wave is measured for calculating the arteriosclerosis index. When a single air bag is used for measurement in this way, a sufficient compression force is required for the measurement site in order to measure blood pressure, so that the required capacity of the air bag is increased. As the capacity of the air bag increases, the pulse wave detection sensitivity for calculating the arteriosclerosis index decreases. Therefore, when using a single air bag for measurement, the accuracy of the calculated arteriosclerosis index may be reduced. Therefore, preferably, as shown in the drawing, the measuring apparatus 1 is provided with air having a small capacity on the central side in addition to the air bag having a large capacity. As a result, the measuring apparatus 1 can detect the pulse wave with higher sensitivity, and can calculate the arteriosclerosis index with high accuracy.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Measuring apparatus, 2 base | substrate, 3 operation part, 4 display part, 9 armband, 10 air tube, 13A, 13B air bag, 20A, 20B air system, 21A air pump, 22A, 22B air valve, 23A, 23B pressure sensor, 26A 27A, 27B, 53 drive circuit, 28A, 28B amplifier, 29A, 29B A / D converter, 31, 32 switch, 40 CPU, 41 memory, 51 2-port valve, 100 upper arm, 401 second derivative calculation unit, 402 Fourth-order differential calculation unit, 403 determination unit, 404 index calculation unit.

Claims (7)

A blood pressure information measuring device that calculates an index of the degree of arteriosclerosis of a measurement subject as blood pressure information,
A first air bag;
A first sensor for detecting the internal pressure of the first air bag as blood pressure information;
Calculating means for calculating an index of the degree of arteriosclerosis based on a change in internal pressure of the first air bag,
The calculation means includes a plurality of points on an internal pressure change curve of the first air bag attached to the measurement site of the measurement subject in a state where the peripheral side is driven based on information on the measurement subject. A blood pressure information measuring device comprising: a calculation means for specifying a feature point representing a reflected wave start point from the image and calculating an index of the degree of arteriosclerosis using the feature point.   The blood pressure information measurement device according to claim 1, wherein the information on the measurement subject is at least one of an age of the measurement subject and a maximum blood pressure value.   The calculation means determines to determine which point among the plurality of points on the internal pressure change curve corresponding to each of the plurality of candidates obtained from the differential curve of the internal pressure change curve as the feature point The blood pressure information measuring device according to claim 1 or 2, further comprising means.   The blood pressure information measurement device according to claim 3, wherein the plurality of candidates obtained from the differential curve includes a maximum point of a secondary differential curve and a descending zero cross point of a quaternary differential curve.   The blood pressure information measurement device according to any one of claims 1 to 4, wherein the index of the degree of arteriosclerosis includes an appearance time difference between an ejection wave and a reflected wave in a pulse waveform of one beat. A second air bag;
A second sensor for detecting the internal pressure of the second air bag as blood pressure information,
The calculation means calculates an index of the degree of arteriosclerosis based on an internal pressure change of the second air bag instead of an internal pressure change of the first air bag,
The calculation means replaces the change in the internal pressure of the first air bag, and the first air bag is located on the distal side of the measurement site, and the second air bag is located on the central side of the measurement site. Based on a change in the internal pressure of the second air bag that is attached to the measurement site and the first air bag is in a state of driving the peripheral side by pressing the distal side of the measurement site. The blood pressure information measurement device according to any one of claims 1 to 5, wherein an index of the degree of arteriosclerosis is calculated. A method for calculating an index of arteriosclerosis in a blood pressure information measuring device,
The blood pressure information measuring device includes an air bag, a sensor for detecting an internal pressure of the air bag as blood pressure information, and an arithmetic means for calculating an index of the degree of arteriosclerosis based on a change in the internal pressure of the air bag. Prepared,
A feature representing a reflected wave start point from among a plurality of points on an internal pressure change curve of the air bag attached to the measurement site of the measurement subject in a state where the peripheral side is driven based on the attribute of the measurement subject A step of identifying points;
Calculating the index of arteriosclerosis using the feature points.

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