JP2013090664A - Device, method and program for evaluating vascular stiffness, and computer-readable recording medium recording the program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for evaluating vascular stiffness which can be inexpensive and miniaturized, and enable a user to easily measuring the vascular stiffness of a specific portion in an ordinary household, a method, and a program for evaluating vascular stiffness; and to provide a computer-readable recording medium recording the vascular stiffness evaluation program.SOLUTION: In the device, a blood vessel is pressurized by a pressurizing means 11 while increasing or lowering pressure, and the pressure of the blood vessel during pressurization is measured by a measuring means 12. A mean pressure and a pressure amplitude which are measured by the measuring means 12 are obtained by a vascular pressure computing means 24 for each of stages of pressurization in the pressurizing means 11. The relationship between a characteristic index about a change in the pressure amplitude for the mean pressure and a stiffness parameter is obtained in advance by a model computing means 14 on the basis of model computation. The characteristic index is obtained by a vascular stiffness computing means 25, and the stiffness parameter is obtained from the characteristic index on the basis of the relationship obtained by the model computing means 14.

Description

  The present invention relates to a blood vessel hardness evaluation apparatus, a blood vessel hardness evaluation method, a blood vessel hardness evaluation program, and a computer-readable recording medium on which a blood vessel hardness evaluation program is recorded.

  As a conventional device for evaluating the stiffness of a blood vessel, the pulse wave velocity and blood pressure of the blood vessel of the measurement target region are measured, and the stiffness parameter of the measurement target region is obtained based on the measurement result (see, for example, Patent Document 1) Further, a stiffness parameter is obtained based on a change in blood vessel inner diameter measured using an ultrasonic diagnostic apparatus and a blood pressure measurement result (see, for example, Patent Document 2), and a blood vessel pulse wave is obtained using a cuff. There is one that detects, calculates the amplitude of the cuff pressure pulse wave and the blood pressure pulse wave, and obtains a unique blood vessel stiffness index based on the pulse wave amplitude (see, for example, Patent Document 3). In addition, there is also one that determines pulse wave velocity information based on the pulse wave of the radial artery and the heart sound waveform detected by the heart sound microphone, and uses it for calculation of a unique blood vessel stiffness index (see, for example, Patent Document 4). ).

  In addition, the present inventors performed a model calculation using a tube rule representing a mechanical characteristic of a blood vessel using an arm vascular system model or a subcutaneous tissue model modeled by a non-linear spring, and obtained by a pressure sensor. The pulse wave is numerically reproduced (for example, see Non-Patent Documents 1 to 3).

JP 2006-6893 A JP 2010-110373 A JP 2008-228934 A JP 2004-16744 A

Tsutomu Nakanishi, Satoshi Shirai, Toshiyuki Hayase, “Reproduction of Pulse Wave Measurement Experiment Using One-Dimensional Mathematical Model for Scientific Validation of Pulse Diagnosis”, Proc. Of the 21st Bioengineering Lecture, The Japan Society of Mechanical Engineers , January 22, 2009, p.51-52 Nakanishi, T., Sirai, A., and Hayase, T., “Reproduction of Pulse Waveform Measurement using One-dimensional Mathematical Model for Validation of Pulse Diagnosis”, GPBE / NUS-Tohoku Graduate Student Conference inBioengineering, Program & Abstract, 2008, p .9-10 Tsutomu Nakanishi, Kentaro Narumi, Atsushi Shirai, Toshiyuki Hayase, “Examination of Mechanical Model of Subcutaneous Tissue for Scientific Validation of Pulse Diagnosis”, The 11th Japan Substitute for Complementary and Complementary Traditional Medicine (JACT) 7th Annual Meeting of the Japan Association for Integrative Medicine (JIM) Program and Abstracts, 2007, p.76

  However, the apparatus described in Patent Document 1 has a problem that the apparatus becomes large because it is necessary to measure pulse waves at two locations when measuring the pulse wave velocity. The apparatus described in Patent Document 2 has a problem that an ultrasonic diagnostic apparatus is expensive and requires specialized knowledge when used. The apparatus described in Patent Document 3 has a problem that the calculation for obtaining the blood vessel stiffness index from each pulse wave is complicated and the calculation scale becomes enormous.

  In the apparatus described in Patent Document 4, since heart sound measurement is necessary, there is a problem that the apparatus becomes large. In addition, it uses the pulse wave velocity information between the heart and the pulse wave measurement site to estimate the average vessel stiffness between them, and cannot estimate the vessel stiffness of a specific site. There was a problem. In the devices described in Patent Documents 3 and 4, since a unique blood vessel hardness index is used, the relevance to the stiffness parameter generally used as a blood vessel hardness index is unknown, and the blood vessel hardness There was a problem that evaluation was difficult.

  The present invention has been made by paying attention to such a problem, and can be inexpensively and miniaturized, and can easily measure and evaluate the blood vessel hardness of a specific part even in a general home. An object of the present invention is to provide a blood vessel hardness evaluation method, a blood vessel hardness evaluation program, and a computer-readable recording medium on which the blood vessel hardness evaluation program is recorded.

  As described in Non-Patent Documents 1 to 3, the present inventors are based on a vascular system model at a measurement target site and a subcutaneous tissue model for calculating blood pressure when a blood vessel is pushed in at a predetermined pressure. Thus, a model calculation was performed for blood pressure fluctuation when the blood vessel was pressurized while increasing the pressure stepwise at predetermined time intervals. As a result, the present inventors have found that the relationship between the average pressure and the pressure amplitude for each pressure stage changes due to the stiffness of the blood vessel, and have reached the present invention.

  That is, the blood vessel stiffness evaluation apparatus according to the present invention includes a pressurizing unit that pressurizes a blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure, and the pressure of the blood vessel that is being pressurized by the pressurizing unit. Measuring means for measuring the blood pressure, blood pressure calculating means for obtaining an average pressure of the blood pressure of the blood vessel measured by the measuring means and a pressure amplitude due to a pulse wave for each predetermined pressure stage in the pressurizing means, The model calculation shows the relationship between the characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel and the parameter related to the stiffness of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure. A model calculation means to be obtained, and a characteristic index relating to a change in the pressure amplitude with respect to the average pressure obtained by the blood vessel pressure calculation means is obtained, and from the characteristic index, the model meter Based on the relationship obtained by the means, and a blood vessel hardness calculating means for calculating a parameter relating to hardness of the blood vessel, characterized in that it has.

  The blood vessel hardness evaluation method according to the present invention includes a pressurizing step of pressurizing a blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure, and measuring the pressure of the blood vessel being pressurized in the pressurizing step. A blood pressure calculation step for obtaining an average pressure of the blood vessel pressure measured in the measurement step and a pressure amplitude by a pulse wave for each predetermined pressure stage in the pressurization step, and a model calculation in advance The relationship between the characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel and the parameter related to the stiffness of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure A characteristic index relating to a change in the pressure amplitude with respect to the average pressure obtained in the model pressure calculating step and a blood vessel pressure calculating step, and obtaining the characteristic index in the model calculating step from the characteristic index. It was based on the relationship, and the blood vessel hardness calculating step of calculating a parameter related to stiffness of the blood vessel, characterized in that it has.

  The blood vessel hardness evaluation program according to the present invention comprises: a receiving means for receiving a pressure of the blood vessel measured by pressurizing a blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure; For each predetermined pressure stage of the blood vessel pressure received at the blood vessel pressure calculating means for obtaining an average pressure of the blood vessel pressure and a pressure amplitude due to a pulse wave, while increasing the pressure obtained in advance by model calculation, Or a model storage means for storing a relationship between a characteristic index relating to a change in pressure amplitude with respect to an average pressure of the blood vessel when the blood vessel is pressurized while reducing the pressure from a predetermined pressure, and a parameter relating to the stiffness of the blood vessel, A characteristic index relating to a change in the pressure amplitude with respect to the average pressure obtained by the blood vessel pressure calculating means is obtained, and the model storage means is obtained from the characteristic index. Based on the stored relationship, characterized in that to function as a vascular hardness calculating means, for determining a parameter related to stiffness of the blood vessel.

  The computer-readable recording medium on which the blood vessel hardness evaluation program according to the present invention is recorded is the pressure of the blood vessel measured by pressurizing the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure. Receiving means, blood vessel pressure calculating means for obtaining an average pressure of the blood vessel pressure and a pressure amplitude due to a pulse wave for each predetermined pressure stage of the blood vessel pressure received by the receiving means, by model calculation in advance The relationship between the obtained characteristic index regarding the change in pressure amplitude with respect to the average pressure of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure, and the parameter regarding the stiffness of the blood vessel. Model storage means for storing, a characteristic index relating to a change in the pressure amplitude with respect to the average pressure obtained by the blood vessel pressure calculating means A blood vessel stiffness evaluation program for functioning as a blood vessel stiffness calculating means for obtaining a parameter relating to the stiffness of the blood vessel based on the relationship stored in the model storage means from the characteristic index obtained. It is characterized by.

  A blood vessel hardness evaluation apparatus, a blood vessel hardness evaluation method, a blood vessel hardness evaluation program, and a computer-readable recording medium that records the blood vessel hardness evaluation program according to the present invention obtain a parameter related to blood vessel hardness, Blood vessel stiffness can be evaluated. In order to evaluate the hardness of the blood vessel, it is only necessary to pressurize the blood vessel and measure the pressure only at the measurement target position, and it is not necessary to measure at a plurality of locations, so that the size can be reduced. A commercially available cuff can be used for pressurization and pressure measurement of the blood vessel, which does not require expensive equipment or equipment and is inexpensive. In addition, by using a cuff, it can be easily measured even in ordinary households. As described above, according to the vascular stiffness evaluation apparatus, the vascular stiffness evaluation method, the vascular stiffness evaluation program, and the computer-readable recording medium that records the vascular stiffness evaluation program according to the present invention, This can be easily measured and evaluated even at home.

  A blood vessel hardness evaluation apparatus, a blood vessel hardness evaluation method, a blood vessel hardness evaluation program, and a computer-readable recording medium that records the blood vessel hardness evaluation program according to the present invention. Any characteristic index may be used as long as it is considered that the stiffness of the blood vessel is reflected. As the characteristic index, it is preferable to use a characteristic index that is greatly influenced by the stiffness of the blood vessel when the change of the pressure amplitude with respect to the average pressure of the blood vessel is obtained by varying the stiffness of the blood vessel by model calculation. The pressurization of the blood vessel may be performed while increasing (decreasing) the pressure stepwise at a predetermined time interval, or may be performed while increasing (decreasing) the pressure continuously. When using a cuff, it is easy to change the pressure continuously.

  A blood vessel hardness evaluation apparatus, a blood vessel hardness evaluation method, a blood vessel hardness evaluation program, and a computer-readable recording medium that records the blood vessel hardness evaluation program according to the present invention. It is preferable to consist of stiffness parameters for ease. In addition, the relationship between the characteristic index and the parameter related to the stiffness of the blood vessel may be directly obtained by model calculation, or indirectly obtained through another parameter between the characteristic index and the parameter related to the stiffness of the blood vessel. Also good. The model used for the model calculation may be any model in which the actual measurement value of the blood pressure fluctuation and the model calculation value when the blood vessel is pressurized while increasing the pressure stepwise at a predetermined time interval substantially match, for example, As in the models described in Non-Patent Documents 1 to 3, the vascular system model in the measurement target region and the subcutaneous tissue model for calculating the blood pressure when the blood vessel is pushed at a predetermined pressure are used in combination. May be.

A vascular stiffness evaluation apparatus, a vascular stiffness evaluation program, and a computer-readable recording medium recording the vascular stiffness evaluation program according to the present invention, wherein the parameter relating to the stiffness of the blood vessel comprises a stiffness parameter, and the model calculation means When obtaining the relationship, it is preferable to obtain a characteristic index by obtaining a change in pressure amplitude with respect to the average pressure of the blood vessel using a tube rule representing the elasticity of the blood vessel, and obtaining a stiffness parameter by the equation (1).
β: Stiffness parameter P: Internal pressure of blood vessel P _b : Arbitrary reference internal pressure of blood vessel A: Cross-sectional area of blood vessel A ₀ : Cross-sectional area of blood vessel when P = P _b

  In the blood vessel stiffness evaluation method according to the present invention, the parameter relating to the stiffness of the blood vessel comprises a stiffness parameter, and the model calculation step uses a tube rule representing the elasticity of the blood vessel to obtain the average of the blood vessel when obtaining the relationship. It is preferable to obtain the characteristic index by obtaining the change in pressure amplitude with respect to the pressure, and obtain the stiffness parameter by the equation (1).

When this tube rule is used, the model calculation is performed on the assumption that the relationship between the cross-sectional area ratio A / A _{0 of} the blood vessel and the extension pressure φ is expressed by the tube rule. Here, the tube rule is expressed by equation (2).

Here, as a reference value used below,
A _C / A ₀ = 0.3
C ₁ = 0.3, C ₂ = 0.05
C _{3 to} C ₅ : Set so that the slopes of φ in the two formulas coincide with each other in A _C / A ₀ = 0.3 φ ₀ : Extension pressure when A / A ₀ = 1 (= 13.3 kPa )
n ₁ = 5 (changes according to blood vessel stiffness)
n ₂ = 6
And

Further, it is known that the relationship between the internal pressure P and the radius R of the blood vessel is expressed by the equation (3) in a blood vessel in a physiological state.
R _b : radius of blood vessel when P = P _b

Assuming that the cross section of the blood vessel in a physiological state is circular, from Equation (2) and Equation (3), φ = P and stiffness parameter β is Equation (1). From equation (1), the stiffness parameter β can be obtained by using the slope of the curve representing the tube rule shown in FIG. 1 when A / A ₀ = 1, and varies depending on the value of the tube rule parameter n _1. To do.

  A blood vessel hardness evaluation apparatus, a blood vessel hardness evaluation program, and a computer-readable recording medium recording the blood vessel hardness evaluation program according to the present invention, wherein the blood vessel hardness calculation means includes a change in the pressure amplitude with respect to the average pressure. Is determined dimensionlessly with the peak value of the pressure amplitude and the average pressure value at that time, and as the characteristic index, a second-order differential value when the pressure is half of the average pressure giving the peak value of the pressure amplitude, It is preferable to obtain a first-order differential value when the pressure amplitude starts to change from zero.

  In the vascular stiffness evaluation method according to the present invention, the vascular stiffness calculation step is configured to make the change in the pressure amplitude with respect to the average pressure non-dimensional with a peak value of the pressure amplitude and a value of the average pressure at that time. As the characteristic index, a second-order differential value when the pressure is half the average pressure giving the peak value of the pressure amplitude and / or a first-order differential value when the pressure amplitude starts to change from 0 is obtained. It is preferable.

  When a second-order differential value or a first-order differential value is used as this characteristic index, the change in pressure amplitude with respect to the average pressure is made dimensionless between the peak value of the pressure amplitude and the value of the average pressure at that time. It is possible to reduce the influence of measuring instrument errors. Further, the second-order differential value when the pressure is half of the average pressure that gives the peak value of the pressure amplitude, and the first-order differential value when the pressure amplitude starts to change from 0 strongly reflect the stiffness of the blood vessel. Therefore, it is possible to more accurately evaluate the stiffness of the blood vessel by using these as characteristic indexes.

  According to the present invention, a vascular stiffness evaluation apparatus, a vascular stiffness evaluation method, and a vascular stiffness evaluation that can be inexpensively and miniaturized and that can easily measure and evaluate the vascular stiffness of a specific part even in a general household. A computer-readable recording medium in which a program and a blood vessel stiffness evaluation program are recorded can be provided.

Is a graph showing the tube law showing the relationship between the blood vessel cross-sectional area ratio A / A ₀ and extension pressure phi. It is a schematic block diagram which shows the blood vessel hardness evaluation apparatus of embodiment of this invention. The blood vessel hardness evaluation apparatus according to the embodiment of the present invention, (a) a graph showing a measurement result of blood pressure when the blood vessel is pressurized stepwise, (a) when the blood vessel is pressurized stepwise A graph showing a model calculation result of the blood pressure of the blood vessel, (c) a graph showing an actual measurement value and a calculated value of the average pressure P _oav for each pressure stage at that time, and (d) a pressure amplitude ΔP for each pressure stage. It is a graph which shows the actual value of ₀ , and a calculated value. It is a side view which shows the (a) mathematical model of an arm part vascular system and (b) a subcutaneous tissue model used by the model calculation of the vascular stiffness evaluation apparatus of embodiment of this invention. Used in the model calculations of the embodiment of vascular stiffness evaluation apparatus of the present invention, it is a graph showing the supply pressure P _s heartbeat one period. 4 is a graph of (a) average pressure P _oav and (b) pressure amplitude ΔP ₀ showing model calculation results when the tube rule parameter n ₁ is changed in the vascular stiffness evaluation apparatus of the embodiment of the present invention. . (A) A graph showing a change in pressure amplitude ΔP ₀ with respect to a non-dimensionalized average pressure P _oav , (b) a second-order differential when P _oav = 0.5, in the vascular stiffness evaluation apparatus according to the embodiment of the present invention. 6 is a graph showing the relationship between the value ΔP ″ and the stiffness parameter β, and (c) a graph showing the relationship between the first-order differential value ΔP ′ and the stiffness parameter β when the pressure amplitude ΔP ₀ starts to change from zero. It is a schematic block diagram which shows the modification of the blood vessel hardness evaluation apparatus of embodiment of this invention. It is a flowchart which shows the blood vessel hardness evaluation method of embodiment of this invention. (A) The cuff internal pressure when the cuff internal pressure is continuously changed, (b) the output voltage of the PVDF film sensor installed inside the cuff at that time in the vascular stiffness evaluation apparatus according to the embodiment of the present invention. It is a graph. (A) a graph showing an average pressure P _oav for each pressure stage when the blood vessel is pressurized while increasing the pressure stepwise, (b) each pressure stage, in the blood vessel stiffness evaluation apparatus of the embodiment of the present invention; It is the graph which shows pressure amplitude ( _DELTA ) P for every, (c) The graph which plotted the change of pressure amplitude ( _DELTA ) P with _respect to average pressure P _oav .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
2 to 11 show a blood vessel hardness evaluation apparatus and a blood vessel hardness evaluation method according to an embodiment of the present invention. The blood vessel hardness evaluation method of the embodiment of the present invention is suitably implemented by the blood vessel hardness evaluation device of the embodiment of the present invention.
Hereinafter, the blood vessel hardness evaluation apparatus and the blood vessel hardness evaluation method according to the embodiment of the present invention will be described with reference to examples as appropriate according to FIGS.

[Pressurizing means and measuring means]
As shown in FIG. 2, the blood vessel hardness evaluation apparatus 10 according to the embodiment of the present invention includes a pressurizing unit 11, a measuring unit 12, a computer 13, and a model calculating unit 14. The pressurizing means 11 is composed of a sensor pressing device and is connected to a computer 13 via an amplifier 15. The measuring means 12 is composed of a pressure sensor and is connected to the computer 13. The measuring means 12 is attached to the pressurizing means 11. The pressurizing means 11 can pressurize a blood vessel such as a radial artery via the measuring means 12. The measuring means 12 can measure the pressure of the blood vessel when pressurized by the pressurizing means 11. The pressurizing means 11 and the measuring means 12 may be made of a commercially available cuff used by being wound around an arm or the like.

[Control means and receiving means]
As shown in FIG. 2, the computer 13 includes a control unit 21 that controls the pressure applied by the pressurizing unit 11 and a receiving unit 22 that receives the pressure measured by the measuring unit 12. The control means 21 can control the pressurizing means 11 by sending a sensor pressing signal to the pressurizing means 11 so as to pressurize the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure. . The control means 21 may control to pressurize the blood vessel while increasing (decreasing) the pressure stepwise at predetermined time intervals, or control to pressurize the blood vessel while increasing (decreasing) the pressure continuously. May be. The receiving means 22 can receive the blood pressure measured by the measuring means 12 via a bandpass filter (BPF) when the blood pressure is pressurized by the pressurizing means 11. As an example of this measurement, FIG. 3A shows the measurement result of the blood pressure when the blood vessel is pressed down by 0.5 mm at intervals of 5 seconds and the blood pressure is increased while increasing the pressure stepwise.

[Model calculation means]
Further, as shown in FIG. 2, the computer 13 has a model storage unit 23. The model storage unit 23 includes a memory, and stores the relationship between the characteristic index and the parameter relating to the stiffness of the blood vessel, which is model-calculated by the model calculation unit 14 in advance. The model calculation unit 14 is configured to be implemented by another computer different from the computer 13. The model calculation means 14 assumes a plurality of parameters related to the stiffness of the blood vessel, and in each case, calculates the blood pressure when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from a predetermined pressure. In addition, the average pressure and the pressure amplitude of the blood vessel are obtained for each predetermined pressure stage. Further, the model calculation means 14 obtains a characteristic index that is considered to reflect the stiffness of the blood vessel from the change in the pressure amplitude with respect to the average pressure of the blood vessel for each parameter related to the stiffness of the blood vessel, and the characteristic index. And a parameter related to the stiffness of the blood vessel. The parameter relating to the stiffness of the blood vessel is a stiffness parameter. The model calculation unit 14 may be implemented by the computer 13.

[Model calculation example-use model]
FIG. 4 shows an example of a model used by the model calculation means 14 in order to evaluate the stiffness of the radial artery blood vessel. Note that the model shown in FIG. 4 is the same as the model described in Non-Patent Documents 1 to 3. As shown in FIG. 4 (a), the mathematical model of the arm vascular system simulates the arterial system (Artery) with a collapsible tube having a taper length of 700 mm and supplies a supply pressure source (Supply) to the upstream end of the tube. However, micro-circulation and vein (Venous) by capillaries are connected to the downstream end. The upstream radius (Inlet radius) of the tube is 4.23 mm, and the downstream radius (Outlet radius) is 1.74 mm. The blood is an incompressible Newtonian fluid having a density ρ = 1050 kg / m ³ and a kinematic viscosity ν = 3.8 × 10 ⁻⁶ m ² / s, and the blood flow is described in one dimension.

Pressurization to the artery and measurement of the pressure are set at a position 100 mm from the downstream end of the tube, and a subcutaneous tissue model (Tissue Model) at the time of pressurization at that position is shown in FIG. As shown in FIG. 4B, when a second-order nonlinear spring model is used as the subcutaneous tissue model, the relationship between the pressing amount Y of the pressure sensor (Sensor) and the sensor output pressure P ₀ is expressed by the following equation (4). Become. The sensor has a circular pressure surface with a diameter of 8 mm.

P _e : Pressure for compressing the artery a: Tissue model constant dy _av : Spatial average value of the amount of change dy from the height y ₀ of the initial shape of the blood vessel on the sensor pressurization surface

Further, the waveform of the pulse one cycle supply pressure (Supply pressure) _{P s} to be used in the model, shown in Figure 5. Here, the average pressure P _sav was 13.3 kPa (100 mmHg), and the amplitude ΔP _s was 5.5 kPa (41 mmHg). The waveform shown in FIG. 5 is created based on the actual measurement value of the human brachiocephalic artery.

[Model calculation example-calculation result]
Model calculation was performed on the model shown in FIG. 4 using the supply pressure shown in FIG. 5 and the tube rule shown in equation (2). In the model calculation, the calculation is performed in the same manner as the model calculation performed in Non-Patent Documents 1 to 3. In the model calculation, first, while changing the tube rule parameter n ₁ , the tissue model constant a, the average pressure P _sav of the supply pressure, and the amplitude ΔP _s , the measured values of the blood pressure shown in FIG. The value of each parameter that fits best was determined. The ranges for changing the values of the parameters are n ₁ = 2 to 12, a = 3.667 × 10 ^{8 to} 16.00 × 10 ⁸ Pa / m ² , and P _sav = 8.3 as realistic values. ˜21.3 kPa and ΔP _s = 3.5 to 9.5 kPa.

FIG. 3B shows a model calculation result that best fits the actually measured values in FIG. In addition, FIG. 3 (c) and FIG. 3 (d) show a comparison between the actual measurement value and the calculated value of the average pressure P _oav and the amplitude ΔP ₀ for each pressure stage at this time, respectively. The values of each parameter at this time were n ₁ = 8, a = 11.0 × 10 ⁸ Pa / m ² , P _sav = 8.3 kPa, and ΔP _s = 4.5 kPa. As shown in FIG. 3, the measured value of the blood pressure fluctuation and the model calculation value based on the model shown in FIG. 4 are almost the same, and the model shown in FIG. 4 can be used to evaluate the stiffness of the blood vessel. There is some thought.

Next, as shown in the equation (1) and FIG. 1, model calculation is performed by varying the tube rule parameter n ₁ correlated with the stiffness parameter β, and the result is shown in FIG. The other parameters at this time were a = 10.0 × 10 ⁸ Pa / m ² , P _sav = 13.3 kPa, and ΔP _s = 5.5 kPa. As shown in FIG. _6A , in the range of Y ≦ 8.0 mm, the average pressure P _oav increases as n ₁ increases, and in the range of Y ≧ 8.0 mm, there is no difference in P _oav. Was confirmed. Further, as shown in FIG. 6B, it was confirmed that the amplitude ΔP ₀ was smaller as n ₁ was larger in the range of Y ≦ 5.0 mm. This is because when the blood vessel is soft (n ₁ is small), the blood vessel is easily deformed by pushing the sensor, and a signal is detected even with a small push amount, whereas the blood vessel is hard (n ₁ is large). When the sensor is pushed, the subcutaneous tissue, not the blood vessel, is deformed, and it is considered that the signal is not detected unless the blood vessel is deformed so that it is pushed.

[Calculation of characteristic index]
As shown in FIG. 6, the change in P _oav due to n ₁ is remarkable in the range where the amount Y pushed into the blood vessel is small. In order to reduce the influence of individual differences and measuring instrument errors, the change of the pressure amplitude ΔP ₀ with respect to the average pressure P _oav is obtained, and there is no difference between the peak value of the pressure amplitude ΔP ₀ and the average pressure P _oav at that time. Dimensionalize and plot on graph. Thereby, the range (P _oav <1.0) where the average pressure P _oav is smaller than the average pressure P _oav (P _oav = 1.0) when the pressure amplitude ΔP ₀ is the peak value (ΔP ₀ = 1.0). in, the value of n _1, the shape of the curve of the graph changes significantly. Specifically, when the value of n ₁ is small, the curve of the graph is convex upward, and when the value of n ₁ is large, the curve of the graph is convex downward. From this, as a characteristic index characterizing the value of n ₁ , the second-order differential value (ΔP ″) when the pressure is half the average pressure P _oav giving the peak value of the pressure amplitude ΔP ₀ (P _oav = 0.5), It may be appropriate to use the first derivative (ΔP ′) when the pressure amplitude ΔP ₀ starts to change from zero.

[Relationship between characteristic index and stiffness parameter]
An example of the characteristic index thus obtained is shown in FIG. FIG. 7 (a) is a graph showing the change of the pressure amplitude ΔP ₀ with respect to the dimensionless average pressure P _oav , FIGS. 7 (b) and (c) are the relationship between ΔP ″ and the stiffness parameter β, and 7 is a graph showing the relationship between ΔP ′ and the stiffness parameter β, where _FIG.7 (a) shows n ₁ = 5, a = 10.0 × 10 ⁸ Pa / m ² , P _sav = 21.3 kPa, and ΔP _s = is a graph of time of 5.5 kPa. also, FIG. 7 (b) and (c) the plotted data (in the figure in the + sign) is tube-law parameters _{n 1,} the organizational model constants a, the supply pressure This is data when the average pressure P _sav and the amplitude ΔP _s are changed variously, and the range in which the value of each parameter is changed is the same as the range when FIG. , from the value of _{n 1} (1) and are determined using a tube law.

  As shown in FIGS. 7B and 7C, ΔP ″ and ΔP ′ are correlated with the stiffness parameter β. When the relationship between ΔP ″ and the stiffness parameter β is expressed by a linear expression The straight line is shown in FIG. FIG. 7C shows a curve when the relationship between ΔP ′ and the stiffness parameter β is expressed by a quadratic expression. The straight line in FIG. 7B and the curve in FIG. 7C are obtained using the least square method so that the residual sum of squares of each data becomes the smallest. The relationship between FIG. 7B and FIG. 7C is not limited to the straight lines and curves shown in the figure, and can be expressed by other straight lines and curves as long as each data can be explained. Good. By using the relationship shown in FIGS. 7B and 7C, the stiffness parameter β can be obtained from the characteristic index. The model storage unit 23 stores the relationship between the characteristic index and the stiffness parameter calculated by the model calculation unit 14 in this way.

[Blood pressure calculation means, vascular stiffness calculation means and display means]
As shown in FIG. 2, the computer 13 further includes a vascular pressure calculation unit 24, a vascular stiffness calculation unit 25, and a display unit 26. The blood vessel pressure calculating means 24 obtains the average pressure and the pressure amplitude separately for each predetermined pressure stage from the measurement value of the blood pressure when the blood pressure is pressurized by the pressurizing means 11.

  The blood vessel hardness calculation means 25 is configured to perform signal processing using the average pressure and pressure amplitude obtained by the blood vessel pressure calculation means 24. The blood vessel hardness calculation means 25 is adapted to obtain a characteristic index based on a change in pressure amplitude with respect to the average pressure obtained by the blood vessel pressure calculation means 24. In addition, the blood vessel hardness calculation unit 25 obtains a stiffness parameter from the characteristic index based on the relationship between the characteristic index stored in the model storage unit 23 and the stiffness parameter. The display means 26 is composed of a monitor and can display the stiffness parameter obtained by the blood vessel hardness calculation means 25.

  As shown in FIG. 8, in the blood vessel hardness evaluation apparatus 10 according to the embodiment of the present invention, the pressurizing means 11 includes a motor 51, a pulley 52, a winding belt 53, etc., and a measuring means comprising a pressure sensor. The blood vessel may be pressurizable via 12. In this case, the control means 21 can control the pressurizing means 11 by sending a motor drive signal to the pressurizing means 11 so as to pressurize the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure. ing. Further, the blood vessel pressure calculating means 24 obtains the change of the average pressure and the pressure amplitude with respect to the pushing amount (sensor displacement) of the measuring means 12 when pressurizing the blood vessel, and based on this, the blood vessel hardness calculating means 25 calculates the average pressure. The change of pressure amplitude with respect to is calculated.

[Implementation by blood vessel stiffness evaluation method]
The blood vessel hardness evaluation apparatus 10 according to the embodiment of the present invention can evaluate the blood vessel hardness by the blood vessel hardness evaluation method according to the embodiment of the present invention. Here, a case where the blood vessel is pressurized while increasing the pressure will be described. First, the pressurizing means 11 and the measuring means 12 are set so that a blood vessel such as the radial artery can be pressurized and the pressure of the blood vessel can be measured, such as by wrapping a cuff around the wrist. As shown in FIG. 9, the control means 21 controls the pressure by the pressurizing means 11 so as to pressurize the blood vessels while increasing the pressure, thereby pressurizing the blood vessels (step 31). The pressure of the blood vessel being pressurized is measured by the measuring means 12 as a pulse wave (step 32). From the measured pulse wave, the mean pressure P _oav and the pressure amplitude ΔP ₀ are obtained for each pressure stage by the vascular pressure calculation means 24 (step 33).

As an example of measuring the pulse wave, using a cuff, the pressure when cuff internal pressure is continuously changed to pressurize the blood vessel (cuff internal pressure), and the output voltage of the PVDF film sensor corresponding to the measured pressure Are shown in FIGS. 10 (a) and 10 (b), respectively. As shown in FIG. 10, at the stage where pressurization is started, the value of the pressure amplitude ΔP ₀ gradually increases every time pressurization is performed, but after ΔP ₀ reaches the maximum value ΔP _max at a predetermined pressure stage, The value of the pressure amplitude ΔP ₀ gradually decreases. Since the measurement data until the pressure amplitude reaches the maximum value ΔP _max is used for the evaluation of the blood vessel hardness, the pressurization may be stopped when the ΔP _max is measured, and the measurement may be terminated.

Therefore, as shown in FIG. 9, at each pressure stage, compared with the maximum value [Delta] P _max of the pressure amplitude before the pressure stage pressure amplitude [Delta] P _0, when the [Delta] P ₀ exceeds ΔP _max, ΔP _max = Pressurize to the next pressure stage as ΔP ₀ . And compared with the pressure repeatedly until the [Delta] P ₀ does not exceed [Delta] P _max, stop pressure when the [Delta] P ₀ is no longer exceeded [Delta] P _max (step 34).

Next, the change in the pressure amplitude ΔP ₀ with respect to the average pressure P _oav is obtained by the blood vessel hardness calculation means 25 and plotted on a graph. At this time, the peak value ΔP _max of the pressure amplitude ΔP ₀ and the average pressure P _oav at that time are _rendered dimensionless and plotted (step 35). FIGS. 11A and 11B show the results of _obtaining the average pressure P _oav and the pressure amplitude ΔP for each pressure stage when the blood vessel is pressurized while gradually increasing the pressure. 11 (a) and 11 (b) show the results of measuring a plurality of times for the same person. Further, FIG. 11C shows a result obtained by _obtaining the change in the pressure amplitude ΔP with respect to the average pressure P _oav from the blood vessel hardness calculation means 25 from FIGS. 10A and 10B and plotting the change in the graph. As shown in FIG. _{11C, by obtaining} the change of the pressure amplitude ΔP with respect to the average pressure P _oav , the error of the pressure amplitude ΔP for each measurement can be reduced and the peak positions of the pressure amplitude ΔP are aligned. You can also.

If plotted on the graph, as shown in FIG. 9, the second-order when the blood vessel hardness calculation means 25 has a pressure of half of the average pressure P _oav giving ΔP _max (P _oav = 0.5) as a characteristic index. differential value [Delta] P "(step 36), and / or to determine the first-order differential value [Delta] P 'when the pressure amplitude [Delta] P ₀ begins to change from 0 (step 37). further, the blood vessel hardness calculating means 25 calculates The stiffness parameter β is obtained from the obtained characteristic index ΔP ″ and / or ΔP ′ based on the relationship between the characteristic index obtained by the model calculation means 14 and stored in the model storage means 23 and the stiffness parameter (step 38). . The obtained stiffness parameter β and the like are displayed by the display means 26. The stiffness of the blood vessel can be evaluated based on the stiffness parameter β thus obtained.

  9 to 11, the case where the blood vessel is pressurized while increasing the pressure has been described. However, even when the blood vessel is pressurized while decreasing the pressure from a predetermined pressure, FIGS. 10 and 11 are used. The results as shown in Fig. 1 can be obtained, and the stiffness of the blood vessel can be evaluated in the same manner.

  The blood vessel hardness evaluation apparatus 10 and the blood vessel hardness evaluation method of the embodiment of the present invention need only perform blood pressure and pressure measurement only at the measurement target position in order to evaluate the blood vessel hardness. Since the measurement at is not necessary, the size can be reduced. A commercially available cuff can be used for blood pressure and pressure measurement. In this case, an expensive apparatus or device is not required, and the cost is low. Moreover, by using a cuff, it can be easily measured even in a general household. Thus, according to the blood vessel hardness evaluation apparatus 10 and the blood vessel hardness evaluation method of the embodiment of the present invention, the blood vessel hardness of a specific part can be easily measured and evaluated even in a general household.

Since the blood vessel hardness evaluation apparatus 10 and the blood vessel hardness evaluation method according to the embodiment of the present invention use the characteristic index ΔP ″ and / or ΔP ′ that strongly reflects the blood vessel hardness, the blood vessel hardness can be more accurately determined. Since a commonly used stiffness parameter is used as a parameter relating to the stiffness of the blood vessel, it is easy to evaluate the stiffness of the blood vessel. A relationship between the characteristic index and the tube rule parameter n ₁ may be obtained, and in this case, the stiffness parameter can be obtained from the obtained n ₁ using the equation (1) and the tube rule.

  The blood vessel stiffness evaluation program according to the embodiment of the present invention may be a program that causes the computer 13 shown in FIGS. 2 and 8 to function. In this case, for example, a computer (including a CPU, an information processing device, and various terminals) 13 mounted or connected to a commercially available home sphygmomanometer as a form for achieving easy measurement at a general home using a cuff, It may be realized by executing the blood vessel stiffness evaluation program according to the embodiment of the present invention according to the flow shown in FIG.

  The blood vessel stiffness evaluation program according to the embodiment of the present invention includes, for example, a CD (CD-ROM, CD-R, CD-RW, etc.), DVD (DVD-ROM, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, etc.) can be provided in a form recorded on a computer-readable recording medium. In this case, the computer 13 can read the blood vessel stiffness evaluation program from the recording medium, transfer it to the internal storage device or the external storage device of the computer, store it, and use it. In addition, the blood vessel stiffness evaluation program according to the embodiment of the present invention is recorded on a storage device (recording medium) such as a magnetic disk, an optical disk, or a magneto-optical disk, and the computer is connected to the computer via a communication line. 13 may be provided.

  Here, the computer is a concept including hardware and an OS (operating system) and means hardware that operates under the control of the OS. Further, when the OS is unnecessary and the hardware is operated by the application program alone, the hardware itself corresponds to the computer. The hardware includes at least a microprocessor such as a CPU and means for reading a computer program recorded on a recording medium.

  The application program as the blood vessel stiffness evaluation program according to the embodiment of the present invention includes a program code to be realized by the computer as described above. Also, some of the functions may be realized by the OS instead of the application program. The computer-readable recording medium according to the embodiment of the present invention includes the above-described flexible disk, CD, DVD, magnetic disk, optical disk, magneto-optical disk, and an internal storage device of the computer (memory such as RAM and ROM). It is also possible to use various computer-readable media such as an external storage device or a printed matter on which a code such as a barcode is printed.

DESCRIPTION OF SYMBOLS 10 Blood vessel hardness evaluation apparatus 11 Pressurizing means 12 Measuring means 13 Computer 21 Control means 22 Receiving means 23 Model storage means 24 Blood vessel pressure calculating means 25 Blood vessel hardness calculating means 26 Display means 14 Model calculating means 15 Amplifier

Claims (8)

Pressurizing means for pressurizing the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure;
Measuring means for measuring the pressure of the blood vessel being pressurized by the pressurizing means;
Blood vessel pressure calculating means for obtaining an average pressure of the blood pressure of the blood vessel measured by the measuring means and a pressure amplitude by a pulse wave for each predetermined pressure stage in the pressurizing means;
Relationship between the characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel and the parameter related to the stiffness of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure by model calculation in advance A model calculation means for obtaining
A characteristic index relating to a change in the pressure amplitude with respect to the average pressure obtained by the vascular pressure calculating means is obtained, and a parameter relating to the stiffness of the blood vessel is obtained from the characteristic index based on the relationship obtained by the model calculating means. Blood vessel stiffness calculating means,
A blood vessel hardness evaluation apparatus comprising: The blood vessel stiffness parameter comprises a stiffness parameter,
The model calculation means obtains the characteristic index by obtaining a change in the pressure amplitude with respect to the average pressure of the blood vessel using a tube rule representing the elasticity of the blood vessel, and obtains a stiffness parameter by the equation (1). The blood vessel stiffness evaluation apparatus according to claim 1.
β: Stiffness parameter P: Internal pressure of blood vessel P _b : Arbitrary reference internal pressure of blood vessel A: Cross-sectional area of blood vessel A ₀ : Cross-sectional area of blood vessel when P = P _b   The blood vessel stiffness calculation means obtains a change in the pressure amplitude with respect to the average pressure by making it non-dimensional with a peak value of the pressure amplitude and a value of the average pressure at that time, and uses the pressure amplitude as the characteristic index. 3. A second-order differential value at a half pressure of an average pressure giving a peak value and / or a first-order differential value when the pressure amplitude starts to change from 0 are obtained. Blood vessel hardness evaluation device. A pressurizing step of pressurizing the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure; and
A measurement step of measuring the pressure of the blood vessel during pressurization in the pressurization step;
A blood vessel pressure calculating step for obtaining an average pressure of the blood vessel pressure measured in the measuring step and a pressure amplitude by a pulse wave for each predetermined pressure stage in the pressurizing step;
Relationship between the characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel and the parameter related to the stiffness of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure by model calculation in advance Model calculation process to find
A characteristic index relating to the change in the pressure amplitude with respect to the average pressure obtained in the blood vessel pressure calculating step is obtained, and a parameter relating to the stiffness of the blood vessel is obtained from the characteristic indicator based on the relationship obtained in the model calculating step. Blood vessel hardness calculation step,
A method for evaluating blood vessel hardness, comprising: The blood vessel stiffness parameter comprises a stiffness parameter,
In the model calculation step, when obtaining the relationship, a change in pressure amplitude with respect to the average pressure of the blood vessel is obtained by using a tube rule representing the elasticity of the blood vessel, and a characteristic index is obtained, and a stiffness parameter is obtained from the equation (1). The blood vessel hardness evaluation method according to claim 4.
β: Stiffness parameter P: Internal pressure of blood vessel P _b : Arbitrary reference internal pressure of blood vessel A: Cross-sectional area of blood vessel A ₀ : Cross-sectional area of blood vessel when P = P _b   In the blood vessel stiffness calculation step, the change in the pressure amplitude with respect to the average pressure is obtained by dimensionlessly calculating the peak value of the pressure amplitude and the value of the average pressure at that time, and as the characteristic index, 6. The second-order differential value at a half pressure of the average pressure giving a peak value and / or the first-order differential value when the pressure amplitude starts to change from 0 are obtained. Blood vessel stiffness evaluation method. Computer
Receiving means for receiving the pressure of the blood vessel measured by pressurizing the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure;
Blood vessel pressure calculating means for obtaining an average pressure of the blood vessel pressure and a pressure amplitude by a pulse wave for each predetermined pressure stage of the blood vessel pressure received by the receiving means;
Characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure, and parameters related to the stiffness of the blood vessel, which are obtained in advance by model calculation Model storage means for storing the relationship between
A characteristic index relating to the change in the pressure amplitude with respect to the average pressure obtained by the vascular pressure calculating means is obtained, and a parameter relating to the stiffness of the blood vessel is obtained from the characteristic index based on the relationship stored in the model storage means. Blood vessel stiffness calculation means,
Vascular stiffness evaluation program to function as. Computer
Receiving means for receiving the pressure of the blood vessel measured by pressurizing the blood vessel while increasing the pressure or decreasing the pressure from a predetermined pressure;
Blood vessel pressure calculating means for obtaining an average pressure of the blood vessel pressure and a pressure amplitude by a pulse wave for each predetermined pressure stage of the blood vessel pressure received by the receiving means;
Characteristic index related to the change in pressure amplitude with respect to the average pressure of the blood vessel when the blood vessel is pressurized while increasing the pressure or decreasing the pressure from the predetermined pressure, and parameters related to the stiffness of the blood vessel, which are obtained in advance by model calculation Model storage means for storing the relationship between
A characteristic index relating to the change in the pressure amplitude with respect to the average pressure obtained by the vascular pressure calculating means is obtained, and a parameter relating to the stiffness of the blood vessel is obtained from the characteristic index based on the relationship stored in the model storage means. Blood vessel stiffness calculation means,
The computer-readable recording medium which recorded the blood vessel hardness evaluation program for making it function as.