JP4453529B2 - Arterial stiffness measurement device - Google Patents

Description

  The present invention relates to an arterial wall stiffness measuring device that measures the degree of stiffness of an arterial wall based on biological information based on deformation generated in a living artery due to a heartbeat.

  A traditional blood pressure measurement method is to use a stethoscope while the cuff pressure is slightly reduced after the brachial artery is blocked by a cuff with an air bladder (Bladder). This is the Korotkoff method for measuring blood pressure by detecting Korotkoff sounds (blood vessel noise). In this method, the blood pressure when Korotkoff sounds are generated is the highest blood pressure (blood pressure in the systolic phase of the heart), and the blood pressure when Korotkoff sounds disappear is the lowest blood pressure (blood pressure in the diastole of the heart).

  On the other hand, in recent years, blood pressure meters that measure blood pressure electrically and electronically have been developed in place of the traditional Korotkoff method due to advances in electronics and the like. This blood pressure monitor uses a blood pressure measurement method such as a photoelectric volume pulse wave method or an oscillometric method (vibration method).

  This photoelectric volumetric pulse wave method is based on the arterial volumetric pulse wave obtained by irradiating a predetermined part of a living body with near infrared light while detecting the reflected light with a photoelectric sensor while changing the cuff's compression pressure very slowly. This is a method for measuring blood pressure. In this photoelectric volume pulse wave method, when the photoelectric volume pulse wave is measured in the process of depressurizing the cuff pressure, the blood pressure when the photoelectric volume pulse wave appears is set as the maximum blood pressure.

  The oscillometric method is a method of measuring blood pressure from a pulse wave envelope obtained by detecting the pressure of the cuff while changing the compression pressure of the cuff slightly. More specifically, in the oscillometric method, first, a cuff is attached to a predetermined part of a living body, and an artery under the predetermined part is blocked by pressurizing the cuff pressure. Thereafter, the cuff pressure is detected while the pressure of the cuff is slightly reduced.

  FIG. 11 is a diagram showing temporal changes in the cuff pressure in the slow depressurization process. The horizontal axis in FIG. 11 is time, and the vertical axis is the cuff pressure. In FIG. 11, a plurality of minute pressure fluctuations 1002 corresponding to the heartbeat occur in the cuff pressure 1001 in the slow depressurization process. The minute pressure fluctuation 1002 superimposed on the cuff pressure 1001 in the slow depressurization process is caused by a volume change in the artery under the cuff due to the pulsation based on the heartbeat.

  That is, when the compression pressure is higher than the maximum blood pressure, the blood pressure is blocked, so that the arterial volume change due to pulsation does not occur, and therefore the minute pressure fluctuation 1002 does not occur. When the compression pressure is close to the maximum blood pressure, in principle, blood flow begins to occur because the internal pressure acting on the artery due to pulsation can resist the compression pressure (external pressure) acting on the artery. Then, the volume change of the artery due to pulsation starts to occur, and a minute pressure fluctuation 1002 starts to occur. Actually, since the cuff swells in a round shape, a pulse wave is detected at the end of the cuff even when the blood pressure exceeds the maximum blood pressure without blocking the artery.

  As the compression pressure is reduced from the maximum blood pressure, the blood vessel gradually expands, and the amount of change in the volume of the artery due to pulsation gradually increases, so that the minute pressure fluctuation 1002 also gradually increases. When the compression pressure becomes the average blood pressure, the minute pressure fluctuation 1002 is maximized. When the compression pressure is further reduced, the minute pressure fluctuation 1002 gradually decreases.

  This is due to the mechanical properties of the arterial wall. The arterial wall has a three-layer structure of intima, media and adventitia, and the intima and media that are made of elastic fibers are highly extensible, while the extensibility of the outer membrane that is made of collagen fibers is Remarkably low. For this reason, in the region where the internal pressure acting on the artery is relatively low, the adventitia does not extend, so the extensibility of the arterial wall depends mainly on the mechanical properties of the intima and media. As a result, the arterial wall sufficiently expands and contracts according to the change in the internal pressure of the artery. On the other hand, in the region where the internal pressure acting on the artery is relatively high, the intima and media are sufficiently stretched and the adventitia covering the outside is also stretched. Will depend on the specific characteristics. As a result, the expansion and contraction of the arterial wall becomes extremely small in accordance with the change in the internal pressure of the artery. Therefore, when the compression pressure becomes the average blood pressure, the difference between the internal and external pressures of the blood vessel becomes 0 on average, and the extensibility of the intima and media is maximized in this vicinity, so that the minute pressure fluctuation 1002 becomes the maximum. When the compression pressure exceeds the average blood pressure and the compression pressure is further reduced, the arterial wall swells. As a result, the adventitia acts dominantly to harden the arterial wall, and the minute pressure fluctuation 1002 gradually decreases.

  For this reason, when the minute pressure fluctuations 1002 superimposed on the cuff pressure 1001 in the slow depressurization process are arranged in time series for each heartbeat, that is, arranged according to the compression pressure, as shown by a solid line in FIG. The minute pressure fluctuations 1002-1 at the time of maximum blood pressure gradually become minute pressure fluctuations 1002-2, 1002-3, 1002-4,... When the amplitude reaches a peak, the amplitude gradually increases. A small minute pressure fluctuation 1002 is obtained. As a result, as shown by a broken line in FIG. 12, the envelope 1003 of minute pressure fluctuations 1002 arranged in time series for each heartbeat becomes a mountain shape. Here, the minute pressure fluctuation 1002 is called a pulse wave, the amplitude of the minute pressure fluctuation 1002 is called a pulse wave amplitude, and the envelope 1003 is called a pulse wave envelope.

  Since the minute pressure fluctuation 1002 superimposed on the cuff pressure 1001 in the slow depressurization process is caused by such a cause, the oscillometric method continues the detection of the cuff pressure under the slow depressurization described above. A pulse wave is detected from the pressure of the cuff detected while the pressure is reduced slightly, and a pulse wave envelope is generated from the detected pulse wave. In the oscillometric method, blood pressures such as the maximum blood pressure, the average blood pressure, and the minimum blood pressure are obtained from the generated pulse wave envelope. In the oscillometric method, the compression pressure at which the pulse wave amplitude of the pulse wave envelope becomes the maximum pulse wave amplitude is the average blood pressure, and the compression pressure at the inflection point of the pulse wave envelope on the higher pressure side than the average blood pressure is the maximum blood pressure. The compression pressure at the inflection point of the pulse wave envelope on the lower pressure side than the average blood pressure is set as the minimum blood pressure. Actually, it is difficult to determine the systolic blood pressure and the diastolic blood pressure based on the inflection point of the pulse wave. Therefore, the determination of the systolic blood pressure and the diastolic blood pressure by the oscillometric method is consistent with the systolic blood pressure and the diastolic blood pressure by the Korotkoff method. The blood pressure measurement program has been devised to improve.

  As can be seen from the above explanation, the change in the pulse wave amplitude of the pulse wave in accordance with the change in the compression pressure (the shape of the pulse wave envelope) is the change in the volume of the artery due to the change in the compression pressure, It is thought to reflect the actual mechanical properties, and reflects the degree of physical (based on mechanical properties) arterial stiffness and cardiovascular diseases such as arteriosclerosis and heart disease. Yes. Note that the degree (degree) of physical (based on mechanical characteristics) arterial hardness is referred to as arterial stiffness in this specification.

  FIG. 13 is a diagram showing various pulse wave envelopes. FIG. 13 (a) is an example of a healthy person, and FIG. 13 (b) shows a case of low blood pressure (a state in which the maximum blood pressure is low (for example, a state of 100 mmHg or less)) or a blood vessel is soft (the blood vessel wall is soft). 13 (c) is an example in the case where arteriosclerosis is progressing or at an advanced age, including at least one of a good blood vessel and one having good blood vessel wall followability according to external pressure due to internal pressure) FIG. 13 (d) is an example of a case where there is a disease in the heart, and FIG. 13 (e) is an example of hypertension and progression of arteriosclerosis or old age. It is an example of a case.

  In this way, since the shape of the pulse wave envelope is considered to reflect the actual mechanical characteristics of the artery, in recent years, the stiffness of the artery is determined using the pulse wave envelope obtained by the oscillometric method. There are researches and developments on devices that can be used, for example, Patent Document 1 and Non-Patent Document 1.

  In the arteriosclerosis measuring device disclosed in Patent Document 1, from the pulse wave envelope obtained by the oscillometric method, as shown in FIG. 14, the inflection point a corresponding to the systolic blood pressure SYS on the pulse wave envelope and the maximum The angle θ formed by the straight line C connecting the two points b corresponding to the 63.2% value of the pulse wave amplitude Amax and the horizontal axis is obtained, and the degree of arteriosclerosis is determined based on this angle θ. Alternatively, an arrival time t from the inflection point a corresponding to the systolic blood pressure SYS on the pulse wave envelope to the point b corresponding to the 63.2% value of the maximum pulse wave amplitude Amax is obtained, and this arrival time t Based on the above, the degree of arteriosclerosis is determined. Alternatively, an increase rate of the pulse wave amplitude A with respect to the decrease rate of the cuff pressure P is obtained, and the degree of arteriosclerosis is determined based on the increase rate. Alternatively, the curve width W between the two points c and d corresponding to the 90% value of the maximum pulse wave amplitude Amax on the pulse wave envelope is obtained, and the ratio of the maximum pulse wave amplitude Amax and the curve width W (Amax / W) And the degree of arteriosclerosis is determined based on this ratio (Amax / W). Alternatively, a ratio (Amax / MEAN) between the maximum pulse wave amplitude Amax and the average blood pressure MEAN is obtained, and the degree of arteriosclerosis is determined based on this ratio (Amax / MEAN).

In Non-Patent Document 1, an experiment using a femoral artery obtained from a 40-year-old male anatomy example shows that the internal pressure Pi of the femoral artery is a predetermined reference internal pressure (considering physiological blood pressure) as shown in Equation 101. The linear relationship between the logarithm ln (Pi / Pis) of the value divided by Pis and the value R0 / Rs of the femoral artery outer radius R0 divided by the outer radius Rs corresponding to the reference inner pressure Ps. It is disclosed that there is.
ln (Pi / Pis) = β (R0 / Rs−1) (Formula 101)
Note that the coefficient β is a slope of a straight line, and the authors of Non-Patent Document 1 call this a stiffness parameter.

Non-Patent Document 1 discloses that there is a linear relationship between an increase ΔPi in the internal pressure P of the femoral artery and an increase ΔR0 in the external radius of the internal pressure Pi as shown in Expression 102. .
β ″ = (ΔPi / Pi) / (ΔR0 / Rs) (Formula 102)
Note that the authors of Non-Patent Document 1 call this β ″ as a modified stiffness parameter.

In clinical practice, the stiffness parameter β and the modified stiffness parameter β ″ are calculated by obtaining an outer radius from the carotid artery or the like using ultrasound. That is, as shown in FIG. The stiffness parameter β and the modified stiffness parameter β ″ are calculated based on the internal pressure-external radius characteristic curve from the minimum blood pressure to the maximum blood pressure.
JP-A-5-38332 Shinzaburo Hayashi, Shiro Nagasawa, Yoshito Naruto, Jun Handa "2. Stiffness and elasticity of arterial wall" Journal of Japan Society for Materials Strength, 1980. Vol. 15, No. 3, P83-P93

  By the way, the arteriosclerosis measuring device disclosed in Patent Document 1 has an angle θ, an arrival time t, an increase rate, a curve width W, a maximum pulse wave amplitude Amax based on values obtained from two points of the pulse wave envelope. The degree of arteriosclerosis is determined by either the ratio (Amax / W) with the curve width W and the ratio (Amax / MEAN) between the maximum pulse wave amplitude Amax and the average blood pressure MEAN. The degree of physical arterial stiffness (based on mechanical properties) and cardiovascular diseases such as arteriosclerosis and heart disease are reflected in the entire curve shape of the pulse wave envelope as described above. Therefore, the technique disclosed in Patent Document 1 is inconvenient for detecting the degree of arterial stiffness and circulatory disease more accurately.

  Further, the stiffness parameter β and the modified stiffness parameter β ″ disclosed in Non-Patent Document 1 are obtained based on the internal pressure P−the external radius Rs. In clinical practice, the stiffness parameter β disclosed in Non-Patent Document 1 is disclosed. The stiffness parameter β and the modified stiffness parameter β ″ are values obtained based on the internal pressure P−the external radius Rs from the lowest blood pressure to the highest blood pressure, and are values in a state where the artery is not collapsed. That is, the mechanical characteristics of the artery from the collapsed state of the artery to the arterial diameter at the time of minimum blood pressure are not reflected.

  The present invention has been made in view of the above-described circumstances, and is based on biological information based on deformation generated in an artery at a predetermined site by a heartbeat in the process of changing the compression pressure applied to the predetermined site of the living body. It is an object of the present invention to provide an arterial stiffness measuring apparatus capable of measuring arterial stiffness with high accuracy.

  In order to achieve the above object, an arterial stiffness measurement apparatus according to an aspect of the present invention includes a compression unit that compresses a predetermined part of a living body, a pressure detection unit that detects the pressure of the compression unit, and the compression A pressure control unit that changes a compression pressure at which the unit compresses the predetermined part, and a magnitude of a pulse wave generated in an artery at the predetermined part by a heartbeat in the process of changing the compression pressure of the compression part based on the detected pressure A pulse wave information detection unit for detecting pulse wave information on the length, the pulse wave information detected by the pulse wave information detection unit, and the compression pressure of the compression unit at the time of detecting the pulse wave information A biometric information processing unit for obtaining a data pair of first and second biometric information based on deformation generated in the artery at the predetermined site by a heartbeat in the process of changing the compression pressure of the unit, and three or more sets obtained by the biometric information processing unit of A linear conversion unit for converting a nonlinear correlation between the three or more data pairs into a linear correlation using a data pair, and a straight line obtained from the data pair converted by the linear conversion unit And a degree-of-hardness measuring unit for determining the degree of hardening of the arterial wall based on the inclination of

  In this arterial stiffness measuring apparatus, the data pair is a data pair on a pulse wave envelope in which the first biological information is the compression pressure and the second biological information is the pulse wave amplitude. It is characterized by being.

  Further, in the above arteriosclerosis measuring apparatus, the three or more data pairs include a region on the lower pressure side than the compression pressure when the pulse wave amplitude including the data pair having the maximum pulse wave amplitude is maximum. It is the data pair which concerns on.

  Further, in the arterial stiffness measuring apparatus, the data pair includes a pressure-internal volume in which the first biological information is a pressure difference between the inside and outside of the artery, and the second biological information is an internal volume of the artery. It is a data pair on a characteristic curve.

  In the above arterial stiffness measurement apparatus, the three or more data pairs are data pairs related to a positive region in which the internal / external pressure difference is 0 or more, including the data pair in which the internal / external pressure difference is 0. It is characterized by that.

  Furthermore, in the above-described arterial stiffness measurement apparatus, the linear conversion unit uses the predetermined value of the first biological information as reference first biological information and the second biological information corresponding to the reference first biological information. Is the reference second biological information, the logarithm of the value obtained by dividing the first biological information of the data pair by the reference first biological information is calculated, and the second biological information of the data pair is used as the reference second biological information. By calculating the value divided by the information, the nonlinear correlation between the three or more data pairs is converted into a linear correlation.

  And in these above-mentioned arteriosclerosis measuring devices, the linear conversion part makes the predetermined value of the 1st living body information the standard 1st living body information, and the 2nd living body information corresponding to the standard 1st living body information Is the reference second biological information, the values obtained by subtracting the reference first and second biological information from the first and second biological information of the data pair are respectively divided by the reference first and second biological information. By calculating the calculated value, the nonlinear correlation between the three or more data pairs is converted into a linear correlation.

  In the arterial stiffness measuring apparatus having such a configuration, the compression unit compresses a predetermined part of the living body, the pressure detection unit detects the pressure of the compression part, and the compression pressure control unit compresses the predetermined part of the compression part. Based on the pressure detected and the pressure detected by the pulse wave information detection unit, pulse wave information relating to the magnitude of the pulse wave generated in the artery at a predetermined site by the heartbeat is detected in the process of changing the compression pressure of the compression unit. Then, the biological information processing unit changes the compression pressure of the compression unit based on the pulse wave information detected by the pulse wave information detection unit and the compression pressure of the compression unit at the time when the pulse wave information is detected. To obtain a data pair of first and second biological information based on the deformation occurring in the artery at a predetermined site, and the linear conversion unit uses the three or more data pairs obtained by the biological information processing unit. The nonlinear correlation between the pairs is converted into a linear correlation, and the arterial wall stiffness of the artery is determined based on the slope of the straight line obtained from the data pair converted by the linearity conversion unit. Find the degree. Therefore, the arterial stiffness measuring apparatus according to the present invention is more accurate based on biological information based on deformation generated in an artery at a predetermined site due to a heartbeat in the process of changing the compression pressure applied to the predetermined site of the living body. The degree of wall hardening can be measured.

Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.
(Configuration of the first embodiment)
FIG. 1 is a block diagram showing the configuration of the arterial stiffness measuring apparatus according to the first embodiment. In FIG. 1, the arterial stiffness measuring apparatus 1A according to the first embodiment includes a cuff 11, a compression pressure control unit 12, a pressure detection unit 13, a pulse wave amplitude detection unit 14, a central processing unit 15A, An output unit 16 and a communication pipe 17 are provided.

  The cuff 11 is a compression band that compresses a predetermined part of the measurement subject (living body), and includes, for example, a rubber bag that can be attached while being wound around the upper arm LB of the living body. The The compression pressure control unit 12 is connected to the cuff 11 via the communication pipe 17 and changes the compression pressure of the cuff 11. For example, the pressure in the cuff 11 is applied by supplying gas into the cuff 11. A pressurizing pump for pressurizing and an exhaust valve for reducing the pressure in the cuff 11 by exhausting the gas in the cuff 11 are configured. In accordance with the control signal from the central processing unit 15A, the compression pressure control unit 12 pressurizes the pressure in the cuff 11 so that the pressure in the cuff 11 becomes a predetermined pressure higher than the maximum blood pressure expected by the measurement subject, The pressure in the cuff 11 is gradually reduced. The pressure detection unit 13 is connected to the cuff 11 via the communication pipe 17, detects the pressure in the cuff 11 at a predetermined sampling interval, and outputs the detected pressure to the central processing unit 15A. A pressure sensor that detects the pressure by converting the pressure into a voltage; and an analog / digital converter that converts an output of the pressure sensor from an analog signal to a digital signal (hereinafter abbreviated as “A / D converter”). It is configured with. The pulse wave amplitude detection unit 14 is a circuit that detects the pulse wave amplitude of the artery, for example, a filter circuit (a high-pass filter circuit or a band-pass filter) that cuts a predetermined frequency component such as a direct current component from the output of the pressure detection unit 13. Circuit), a pulse wave signal is generated by cutting a predetermined frequency component from the output of the pressure detection unit 13, a pulse wave is generated from a temporal change of the generated pulse wave signal, and the generated pulse wave To detect the pulse wave amplitude. The pulse wave amplitude detector 14 is an example of a pulse wave information detector, and the pulse wave amplitude is an example of pulse wave information. The output unit 16 is a device that outputs the state of the arterial stiffness measurement apparatus 1A in operation and the arterial stiffness H of the measurement result, for example, a display device such as a CRT display, LCD, organic EL display, or plasma display, A printing device such as a printer;

  The central processing unit 15A includes, for example, a microcomputer configured with a microprocessor, a storage circuit, and its peripheral circuits, and functionally includes a biological information processing unit 18A, a linear conversion unit 19A, and a curing degree measurement unit. 20A, and the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14 and the output unit 16 are controlled according to the function according to the control program, thereby controlling the entire arterial stiffness measuring apparatus 1A. It is something to control. The memory circuit is executing various programs such as an arterial stiffness program for controlling the arterial stiffness measuring apparatus 1A to measure the arterial stiffness H, data necessary for executing the various programs, and executing various programs. And various data such as data generated after execution. The storage circuit includes, for example, a volatile storage element such as a RAM (Random Access Memory) serving as a so-called working memory of a microprocessor, a ROM (Read Only Memory) that stores programs, data, and the like, and a rewritable EEPROM ( Nonvolatile memory elements such as Electrically Erasable Programmable Read Only Memory) are included.

  The biological information processing unit 18A performs a heartbeat in the process of changing the compression pressure of the cuff 11 based on the pulse wave amplitude detected by the pulse wave amplitude detection unit 14 and the compression pressure of the cuff 11 at the time when the pulse wave amplitude is detected. Thus, the data pair of the first and second biological information based on the deformation generated in the artery in the predetermined part (upper arm LB) of the living body is obtained. The linear conversion unit 19A uses the three or more data pairs obtained by the biological information processing unit 18A to convert the non-linear correlation between the three or more data pairs into a linear correlation. is there. The degree-of-hardness measurement unit 20A calculates the arterial wall hardening degree H of the artery based on the straight line inclination α obtained from the data pair converted by the linear conversion unit 19A.

  Here, the arterial stiffness measuring apparatus 1A according to the first embodiment uses a pulse wave envelope as a characteristic curve composed of data pairs of the first and second biological information, and forms three sets of the pulse wave envelope. This is an embodiment in which the above data pair is linearly converted using a first pressure logarithmic conversion described later, and the degree of arterial stiffness is obtained based on the slope α of the straight line obtained from the converted data pair. Therefore, the biological information processing unit 18A includes a pulse wave processing unit 181 and a pulse wave amplitude characteristic information storage unit, and the linear conversion unit 19A includes a pulse wave amplitude characteristic log-linear conversion unit 191A. The hardening degree measuring unit 20A includes a pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination unit 201A and a pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination table storage unit 202A.

  The pulse wave processing unit 181 corresponds the pulse wave amplitude detected by the pulse wave amplitude detecting unit 14 and the compression pressure detected by the pressure detecting unit 13 at the time of detecting the pulse wave amplitude as a data pair of pressure-pulse wave amplitude. In addition, the pulse wave amplitude characteristic information storage unit 182 stores the pulse wave amplitude characteristic information.

  The pulse wave amplitude characteristic information storage unit 182 stores a plurality of pressure-pulse wave amplitude data pairs generated by the pulse wave processing unit 181. As can be understood from the description of the background art, by plotting the plurality of pressure-pulse wave amplitude data pairs in the pressure-pulse wave amplitude coordinate system, the pressure-pulse wave amplitude characteristic curve, that is, the pulse wave envelope is obtained. can get. The pressure in the pressure-pulse wave amplitude characteristic curve (pulse wave envelope) is a compression pressure. In the first embodiment, the compression pressure corresponds to the first biological information, and the pulse wave amplitude corresponds to the second biological information.

  The pulse wave amplitude characteristic logarithmic linear conversion unit 191A uses three or more sets of pressure-pulse wave amplitude data pairs stored in the pulse wave amplitude characteristic information storage unit 182 to perform the three or more sets by a predetermined linear conversion algorithm. The nonlinear correlation between the data pairs is converted into a linear correlation.

  The pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination table storage unit 202A stores a pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination table. The pulse wave amplitude characteristic logarithm arterial stiffness determination table is a table for determining the arterial stiffness H from the linear slope α obtained from the linearly converted pressure-pulse wave amplitude data pair. In the embodiment, the table is obtained by associating the slope α of the straight line obtained from the linearly converted pressure-pulse wave amplitude data pair and the degree of hardening of the arterial wall obtained by statistically examining in advance. The pulse wave amplitude characteristic logarithmic arterial wall stiffness determination unit 201A has a pulse wave amplitude characteristic logarithmic arterial wall stiffness determination table based on the slope α of the straight line obtained from the data pair converted by the pulse wave amplitude characteristic logarithmic linear conversion unit 191A. The arterial stiffness H is obtained by referring to the pulse wave amplitude characteristic logarithmic arterial stiffness determination table stored in the storage unit 202 </ b> A and is output to the output unit 16.

Next, the operation of this embodiment will be described.
(Operation of the first embodiment)
FIG. 2 is a flowchart showing the operation of the arterial stiffness measurement apparatus according to the first embodiment.

  The measurer or the subject himself / herself turns on the power of the arterial stiffness measurement apparatus 1A, attaches the cuff 11 to the subject's upper arm LB, and starts measurement of the arterial stiffness, for example, Operate the measurement start switch (not shown).

  In FIG. 2, when the central processing unit 15A detects the operation of the measurement start switch (not shown), the central processing unit 15A controls the compression pressure control unit 12 to rapidly increase the pressure in the cuff 11 to the start target pressure. The compression pressure control unit 12 pressurizes the cuff 11 by supplying gas into the cuff 11 based on the control signal (S11). As a result, the upper arm LB of the measurement subject is strongly compressed by the cuff 11, and the blood flow of the artery under the cuff 11 is blocked.

  When the pressure detected by the pressure detection unit 13 reaches a predetermined target pressure that is higher than the expected maximum blood pressure of the measured person, the central processing unit 15A gradually moves through the cuff 11. In order to reduce the pressure, a control signal is output to the compression pressure control unit 12, and the compression pressure control unit 12 starts the slow depressurization in the cuff 11 by gradually exhausting the gas in the cuff 11 based on this control signal ( S12).

  Next, the pulse wave amplitude detector 14 measures the pulse wave of one heartbeat based on the output of the pressure detector 13, detects the pulse wave amplitude in the measured pulse wave of one heartbeat, and detects the detected pulse wave. The amplitude is output to the pulse wave processing unit 181 of the biological information processing unit 18A (S13). That is, during the slow depressurization of the cuff 11, the pressure detection unit 13 detects the pressure of the cuff 11 at a predetermined sampling interval, and the pulse wave amplitude detection unit 14 and the pulse wave processing are performed using the detected pressure of the cuff 11 as a compression pressure. To the unit 181. The pulse wave amplitude detection unit 14 generates a pulse wave of one heartbeat by plotting the output of the pressure detection unit 13 in time series order, and detects the pulse wave amplitude in the pulse wave of one heartbeat from the generated pulse wave. Then, the pulse wave amplitude detector 14 outputs the detected pulse wave amplitude to the pulse wave processor 181.

  Next, when the pulse wave amplitude in the pulse wave of one heartbeat is input from the pulse wave amplitude detection unit 14 to the pulse wave processing unit 181 of the biological information processing unit 18A, the pulse wave processing unit 181 is input from the pressure detection unit 13 at a predetermined sampling interval. The compression pressure at the time when the input pulse wave amplitude is detected is detected from the pressures that are input (S14).

  Next, the pulse wave processing unit 181 of the biological information processing unit 18A stores the data pair of the pulse wave amplitude and the compression pressure at the time when the pulse wave amplitude is detected in the pulse wave amplitude characteristic information storage unit 182 and the pressure-pulse wave amplitude. (S15).

  Next, the central processing unit 15A determines whether or not the slow depressurization of the cuff 11 has ended by determining whether or not the pressure detected by the pressure detecting unit 13 has reached the end target pressure (S16). . As a result of the determination, when the slow depressurization of the cuff 11 is not completed, the central processing unit 15A returns the process to the process S13. On the other hand, as a result of the determination, the slow depressurization of the cuff 11 is completed. The central processing unit 15A executes the process S17. By operating in this manner, the pressure-pulse wave amplitude data pair is measured for each heartbeat during the slow depressurization, and the measured pressure-pulse wave amplitude data pair is stored in the pulse wave amplitude characteristic information storage unit 182. Remembered.

  In step S17, when the slow depressurization ends, the central processing unit 15A outputs a control signal to the compression pressure control unit 12 to return the pressure in the cuff 11 to substantially atmospheric pressure, and the compression pressure control unit 12 Based on the above, the gas in the cuff 11 is rapidly exhausted to reduce the pressure in the cuff 11 to approximately atmospheric pressure. As a result, the upper arm LB of the person to be measured is released from the pressure of the cuff 11.

  Next, the pulse wave amplitude characteristic logarithmic linear conversion unit 191A of the linear conversion unit 19A has three or more sets of pressure-pulse wave amplitude data pairs stored in the pulse wave amplitude characteristic information storage unit 182 of the biological information processing unit 18A. Is converted by the predetermined linear conversion algorithm so that the mutual relationship between the three or more pairs of pressure-pulse wave amplitude data becomes linear (S18).

  Here, the inventors set the compression pressure C as the reference compression pressure Cs when the predetermined compression pressure C is set as the reference compression pressure Cs and the pulse wave amplitude A at the reference compression pressure Cs is set as the reference pulse wave amplitude As. A linear relationship is established between the natural logarithm ln of the value C / Cs divided by (C / Cs) and the value A / As obtained by dividing the pulse wave amplitude A by the reference pulse wave amplitude As, and the slope α of the straight line α Was found to reflect the arterial stiffness H well.

  Therefore, assuming that the pressure-pulse wave amplitude data pair is represented as (Cn, An), the linear conversion by the first pressure logarithmic conversion first converts the reference compression pressure Cs to the pulse wave amplitude A of the pulse wave envelope. Is the compression pressure C at which the maximum pulse wave amplitude Amax is obtained. Therefore, the reference pulse wave amplitude As is the maximum pulse wave amplitude Amax. Next, the pressure-pulse wave amplitude data pair (Cn, An) is divided (divided) by the reference compression pressure Cs and the reference pulse wave amplitude As, and the value Cn / value obtained by dividing the compression pressure Cn by the reference compression pressure Cs. A data pair (Cn / Cs, An / As) of Cs and a value An / As obtained by dividing the corresponding pulse wave amplitude An by the reference pulse wave amplitude As is obtained. Next, the natural logarithm ln (Cn / Cs) of the value Cn / Cs obtained by dividing the compression pressure Cn by the reference compression pressure Cs is obtained, and the natural logarithm ln of the value Cn / Cs obtained by dividing the compression pressure Cn by the reference compression pressure Cs ( Cn / Cs) and a data pair (ln (Cn / Cs), An / As) of a value An / As obtained by dividing the corresponding pulse wave amplitude An by the reference pulse wave amplitude As are obtained.

  Here, 1 is subtracted from An / As to set the coordinate origin of the horizontal axis to As / As, and (An / As-1) is set to the horizontal axis and ln (Cn / Cs) is set to the vertical axis (An / As -1) Plot the data pair (ln (Cn / Cs), An / As-1) in the-(ln (Cn / Cs)) plane coordinate system. FIG. 3 is a graph showing a data pair (ln (Cn / Cs), A / As-1) in each region. FIG. 3A is a graph of data pair (ln (Cn / Cs), An / As-1) in the region higher than the reference compression pressure Cs corresponding to the maximum pulse wave amplitude Amax (= reference pulse wave amplitude As). FIG. 3B shows a data pair (ln (Cn / Cs), An / As−1) in a region lower than the reference compression pressure Cs corresponding to the maximum pulse wave amplitude Amax (= reference pulse wave amplitude As). ).

  Next, the pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination unit 201A of the hardening degree measuring unit 20A receives the data pair (ln (Cn / Cs), An / As-1) converted by the pulse wave amplitude characteristic logarithmic linear conversion unit 191A. ) And refer to the pulse wave amplitude characteristic logarithmic arterial stiffness determination table stored in the pulse wave amplitude characteristic logarithmic arterial stiffness determination table storage unit 202A based on the obtained slope α of the straight line. Is used to determine the degree of arterial stiffness H (S19).

  Here, a straight line is obtained from each point of three or more data pairs (ln (Cn / Cs), An / As-1) in the high-pressure side region shown in FIG. 3A, and the slope αh of the straight line is obtained. Alternatively, a straight line is obtained from each point of three or more data pairs (ln (Cn / Cs), An / As-1) in the low-pressure region shown in FIG. 3B, and the slope of the straight line is obtained. Although αl may be obtained, a straight line may be obtained from each point of three or more data pairs (ln (Cn / Cs), An / As-1) in the high-pressure side region and the low-pressure side region. To that end, for example, the data pair (ln (Cn / Cs), An / As-1) in the high-pressure side region shown in FIG. 3A is folded with respect to the vertical axis, and the low-pressure side shown in FIG. When the data pairs (ln (Cn / Cs), An / As-1) in the region are combined, the graph shown in FIG. 4 is obtained. A straight line of this graph is obtained, and the slope α of the straight line is obtained. FIG. 4 is a diagram illustrating a graph of data pairs (ln (Cn / Cs), A / As-1) in the entire region. It should be noted that the data pair (ln (Cn / Cs), An / As-1) in the low-pressure side region shown in FIG. 3B is folded with respect to the vertical axis, and the data in the high-pressure side region shown in FIG. The pair (ln (Cn / Cs), An / As-1) may be combined to obtain a straight line of this graph, and the slope -α of the straight line may be obtained. Further, from the viewpoint of minimizing the error from each data pair, these straight lines may be obtained using, for example, the least square method.

  Then, the pulse wave amplitude characteristic logarithmic arterial wall hardening degree determination unit 201A of the hardening degree measurement unit 20A outputs the determined arterial wall hardening degree H to the output unit 16 (S20).

  As described above, the arterial stiffness measuring apparatus 1A according to the first embodiment obtains a pulse wave by depressurizing from the ischemic state at a low speed, so that the dynamics of the artery when a wide range of compression pressure is applied to the artery. A pulse wave envelope (data pair) reflecting the characteristics can be obtained. Also, the arterial stiffness measurement apparatus 1A does not determine the arterial stiffness H from the shape of the curve shape of the pulse wave envelope itself, but linearly converts the curve shape of the pulse wave envelope and performs linear conversion. Since the determination is made from the slope α of the obtained straight line, the arterial stiffness H can be easily and accurately determined. Since the straight line slope α is obtained from three or more pairs of data, the curve shape of the pulse wave envelope is better reflected, and the arterial stiffness H can be measured with higher accuracy.

Next, another embodiment will be described.
(Configuration of Second Embodiment)
FIG. 5 is a block diagram illustrating a configuration of the arterial stiffness measuring apparatus according to the second embodiment. In FIG. 5, the arterial stiffness measuring apparatus 1B according to the second embodiment includes a cuff 11, a compression pressure control unit 12, a pressure detection unit 13, a pulse wave amplitude detection unit 14, a central processing unit 15B, An output unit 16 and a communication pipe 17 are provided.

  The cuff 11, the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, the output unit 16, and the communication pipe 17 in the second embodiment are the same as the cuff 11, the compression pressure control unit in the first embodiment. 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, the output unit 16, and the communication pipe 17 are the same as each other, and the description thereof is omitted. The central processing unit 15B includes, for example, a microcomputer including a microprocessor, a storage circuit, and its peripheral circuits, and functionally detects the pulse wave amplitude detected by the pulse wave amplitude detection unit 14 and the pulse wave. Based on the compression pressure of the pressure part at the time of detecting the wave amplitude, the data pair of the first and second biological information based on the deformation generated in the artery in the predetermined part of the living body due to the heartbeat in the process of changing the compression pressure of the cuff 11 The biometric information processing unit 17B that calculates the non-linear correlation between the three or more data pairs is converted into a linear correlation using the three or more data pairs determined by the biometric information processing unit 17B. The linearity conversion unit 19B and the degree-of-hardness measurement unit 2 for determining the arterial stiffness H of the artery based on the linear inclination α obtained from the data pair converted by the linear conversion unit 19B B, and according to the control program, the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14 and the output unit 16 are respectively controlled according to the function to control the entire arterial stiffness measuring apparatus 1B. It is something to control.

  Here, the arterial stiffness measuring apparatus 1B according to the second embodiment uses a pressure-internal volume characteristic curve obtained from a pressure-pulse wave amplitude data pair (pulse wave envelope) as biological information, and uses this pressure- Three or more pairs of data forming the internal volume characteristic curve are linearly converted using the second pressure logarithmic transformation described later, and the arterial wall stiffness H is calculated based on the slope α of the straight line obtained from the data pair after the transformation. This is an embodiment for obtaining. Therefore, the biological information processing unit 18B includes a pulse wave processing unit 181, a pulse wave amplitude characteristic information storage unit 182, a pressure-internal volume characteristic conversion unit 183, and a pressure-internal volume characteristic information storage unit 184, and is linear. The conversion unit 19B includes a pressure-internal volume characteristic logarithmic linear conversion unit 191B, and the hardening degree measurement unit 20B includes the pressure-internal volume characteristic logarithmic arterial wall hardening degree determination unit 201B and the pressure-internal volume characteristic logarithm. And an arterial wall stiffness determination table storage unit 202B.

  Since the pulse wave processing unit 181 and the pulse wave amplitude characteristic information storage unit 182 are the same as the pulse wave processing unit 181 and the pulse wave amplitude characteristic information storage unit 182 described in the first embodiment, description thereof is omitted. . The pressure-internal volume characteristic conversion unit 183 converts the pressure-pulse wave amplitude data pair stored in the pulse wave amplitude characteristic information storage unit 182 into a pressure-internal volume data pair. The conversion from the pressure-pulse wave amplitude data pair (the data pair on the pulse wave envelope) to the pressure-internal volume data pair (the data pair on the pressure-internal volume characteristic curve) is performed by a known process, for example, a special process. Since the processing disclosed in Kaihei 5-305061, JP-A-7-124129, etc. is used, the description thereof is omitted. The pressure-internal volume characteristic information storage unit 184 stores a plurality of pressure-internal volume data pairs generated by the pressure-internal volume characteristic conversion unit 183. Then, the pressure-internal volume characteristic curve is obtained by plotting the plurality of pressure-internal volume data pairs in the pressure-internal volume coordinate system. The pressure in the pressure-internal volume characteristic curve is the pressure difference between the inside and outside of the artery. In the second embodiment, the internal / external pressure difference of the artery corresponds to the first biological information, and the internal volume of the artery corresponds to the second biological information.

  The pressure-internal volume characteristic logarithmic linear conversion unit 191B uses three or more sets of pressure-internal volume data pairs stored in the pressure-internal volume characteristic information storage unit 184, and performs the three sets by a predetermined linear conversion algorithm. The non-linear correlation between the above data pairs is converted into a linear correlation.

  The pressure-internal volume characteristic logarithmic arterial wall hardening degree determination table storage unit 202B stores a pressure-internal volume characteristic logarithmic arterial wall hardening degree determination table. The pressure-internal volume characteristic logarithm arterial stiffness determination table is a table for determining the arterial stiffness H from the linear slope α obtained from the linearly converted pressure-internal volume data pair. In the embodiment, the table is obtained by associating the slope α of the straight line obtained from the linearly-transformed pressure-internal volume data pair and the degree of hardening of the arterial wall obtained by statistically examining in advance. The pressure-internal volume characteristic logarithmic arterial wall stiffness determination unit 201B is configured to determine the pressure-internal volume characteristic logarithmic arterial wall stiffness based on the slope α of the straight line obtained from the data pair converted by the pressure-internal volume characteristic logarithmic linear conversion unit 191B. The arterial stiffness H is obtained by referring to the pressure-internal volume characteristic logarithmic arterial stiffness determination table stored in the degree determination table storage unit 202B, and is output to the output unit 16.

Next, the operation of this embodiment will be described.
(Operation of Second Embodiment)
FIG. 6 is a flowchart showing the operation of the arterial stiffness measurement apparatus according to the second embodiment. FIG. 7 is a diagram showing a pressure-internal volume characteristic curve. The horizontal axis in FIG. 7 indicates the internal / external pressure difference, and the vertical axis indicates the internal volume.

  The measurer or the subject himself / herself turns on the power of the arterial stiffness measurement apparatus 1B, attaches the cuff 11 to the upper arm LB of the subject, and starts measurement of the arterial stiffness H. For example, a measurement start switch (not shown) is operated.

  In FIG. 6, from the quick pressurization process (S31) of the cuff 11 to the start target pressure, which is executed after the central processing unit 15B detects the operation of the measurement start switch (not shown), the process of starting the slow depressurization of the cuff 11 ( S32), pulse wave measurement, pulse wave amplitude detection processing (S33), compression pressure detection processing at pulse wave amplitude detection (S34), pressure-pulse wave amplitude data pair storage processing (S35), and slow depressurization Each process from the end determination process (S36) to the rapid exhaust process (S37) is performed from the rapid pressurization process (S11) of the cuff 11 up to the start target pressure in the first embodiment to the slow depressurization of the cuff 11. Start processing (S12), pulse wave measurement, pulse wave amplitude detection processing (S13), compression pressure detection processing during pulse wave amplitude detection (S14), pressure-pulse wave amplitude data pair storage processing (S15) And end determination processing of slow depressurization ( Since 16) and the process to reach quick exhaust processing (S17) via the respectively same, description thereof will be omitted.

  Then, the pressure-internal volume characteristic conversion unit 183 of the biological information detection unit 17B calculates the pressure-internal volume from the pressure-pulse wave amplitude data pair stored in the pulse wave amplitude characteristic information storage unit 182 by a known method. The data pair is converted, and the pressure-internal volume data pair is stored in the pressure-internal volume characteristic information storage unit 184 (S38).

  The pressure of the pressure-internal volume characteristic is an arterial internal / external pressure difference, that is, an average blood pressure-compression pressure. As explained in the background art, in the region where the pressure difference between the inside and outside of the artery is negative, it depends mainly on the mechanical properties of the intima and media, so the internal volume gradually increases as the compression pressure decreases. The ratio of the change in the internal volume to the unit change in the internal / external pressure difference gradually increases, and in the vicinity of the artery internal / external pressure difference = 0 (mean blood pressure−compression pressure = 0 point), the intima and media Since the membrane develops most, the ratio of the change in the internal volume to the unit change in the internal / external pressure difference is also maximized. In the region where the pressure difference between the inside and outside of the arteries is positive, it depends mainly on the mechanical properties of the media, and then depends mainly on the mechanical properties of the media and the media. Therefore, as the compression pressure decreases, the ratio of the change in the internal volume to the unit change in the internal / external pressure difference gradually decreases, and the internal volume does not increase so much as the compression pressure decreases. Accordingly, as shown in FIG. 7, the pressure-internal volume characteristic curve is a monotonically increasing function in which the internal volume increases from 0 to a predetermined internal volume value as the internal / external pressure difference increases (decrease in compression pressure). The ratio of the change in the internal volume to the unit change in the pressure difference gradually increases as the internal / external pressure difference increases in the negative region, and the arterial internal / external pressure difference = 0. And then gradually decreases in a region where the pressure difference between the inside and outside of the artery is positive. Therefore, as shown in FIG. 7, the shape of the pressure-internal volume characteristic curve is a curve that rises sharply from 0, has a maximum slope when the internal / external pressure difference = 0, and then gradually rises to the right. In particular, in a region where the internal / external pressure difference is positive, the soft artery has a larger internal volume than the hard artery at the same internal / external pressure difference. Therefore, the pressure-internal volume characteristic curve s of the soft artery is a solid line in FIG. The pressure-internal volume characteristic curve h of the hard artery is as shown by a broken line in FIG.

  Next, the pressure-internal volume characteristic logarithmic linear conversion unit 191B of the linear conversion unit 19B has three or more sets of pressure-internal volume data stored in the pressure-internal volume characteristic information storage unit 184 of the biological information processing unit 18B. Using the pair, conversion is performed so that the correlation between the three or more pressure-internal volume data pairs becomes linear by a predetermined linear conversion algorithm (S39).

  Here, the inventors set the predetermined internal / external pressure difference P as the reference internal / external pressure difference Ps, and when the internal volume V at the reference internal / external pressure difference Ps is set as the reference internal volume Vs, the internal / external pressure difference P is determined as the reference internal / external pressure difference Ps. A linear relationship is established between the natural logarithm ln (P / Ps) of the value P / Ps divided by the pressure difference Ps and the value V / Vs obtained by dividing the internal volume V by the reference internal volume Vs, and the slope of the straight line It was found that α well reflects arterial stiffness H.

  When three or more data pairs in the positive region are used, there is no problem. However, if the pressure-internal volume characteristic curve shown in FIG. 7 is used as it is, the logarithm cannot be obtained in the negative region. Coordinate conversion is performed so that the pressure-internal volume characteristic curve moves in parallel in the positive direction of the horizontal axis so that the internal volume characteristic curve becomes all positive values. When the pressure-internal volume data pair after the coordinate conversion is expressed as (Pn ′, Vn), the linear conversion by the second pressure logarithmic conversion first arbitrarily sets the internal / external pressure difference P ′ as a reference. The internal / external pressure difference Ps is set, and the internal volume Vn corresponding to the reference internal / external pressure difference Ps is set as the reference internal volume Vs. Next, the pressure-internal volume data pair (Pn ′, Vn) is divided (divided) by the reference internal / external pressure difference Ps and the reference internal volume Vs, respectively, and the internal / external pressure difference Pn ′ is divided by the reference internal / external pressure difference Ps. A data pair (Pn ′ / Ps, Vn / Vs) of the value Vn / Vs obtained by dividing the value Pn ′ / Ps and the corresponding internal volume Vn by the reference internal volume Vs is obtained. Next, a natural logarithm ln (Pn ′ / Ps) of a value Pn ′ / Ps obtained by dividing the internal / external pressure difference Pn ′ by the reference internal / external pressure difference Ps is obtained, and a value obtained by dividing the internal / external pressure difference Pn ′ by the reference internal / external pressure difference Ps. A data pair (ln (Pn '/ Ps), Vn / Vs) of a value Vn / Vs obtained by dividing the natural logarithm ln (Pn' / Ps) and the corresponding internal volume Vn by the reference internal volume Vs is obtained.

  Next, the pressure-internal volume characteristic logarithm arterial wall hardening degree determination unit 201B of the degree-of-curing degree measurement unit 20B calculates a straight line from the data pair converted by the pressure-internal volume characteristic logarithmic linear conversion unit 191B, The arterial stiffness H is determined by referring to the pressure-internal volume characteristic logarithmic arterial stiffness determination table storage unit 202B based on the inclination α. (S40). Further, from the viewpoint of minimizing an error from each data pair, a straight line may be obtained from this data pair using, for example, a least square method.

  Then, the pressure-internal volume characteristic logarithmic arterial wall hardening degree determining unit 201B of the hardening degree measuring unit 20B outputs the determined arterial wall hardening degree H to the output unit 16 (S41).

  As described above, the arterial stiffness measuring apparatus 1B according to the second embodiment obtains the pressure-internal volume characteristic curve based on the pulse wave obtained by slow depressurization from the ischemic state. When pressure is applied to the artery, a pressure-internal volume characteristic curve reflecting the mechanical characteristics of the artery can be obtained. In addition, the arterial stiffness measurement apparatus 1B does not determine the arterial stiffness H from the shape of the pressure-internal volume characteristic curve itself, but linearly converts the curve shape of the pressure-internal volume characteristic curve, Since the determination is made from the straight line inclination α obtained by linear conversion, the arterial stiffness H can be easily and accurately determined. Since the slope α of this straight line is obtained from three or more pairs of data, the curve shape of the pressure-internal volume characteristic curve is better reflected, and the arterial stiffness H can be measured with higher accuracy.

Next, another embodiment will be described.
(Configuration of Third Embodiment)
FIG. 8 is a block diagram illustrating a configuration of the arterial stiffness measurement apparatus according to the third embodiment. In FIG. 8, the arterial stiffness measuring apparatus 1C according to the third embodiment includes a cuff 11, a compression pressure control unit 12, a pressure detection unit 13, a pulse wave amplitude detection unit 14, a central processing unit 15C, An output unit 16 and a communication pipe 17 are provided.

  The cuff 11, the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, the output unit 16, and the communication pipe 17 in the third embodiment are the same as the cuff 11, the compression pressure control unit in the first embodiment. 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, the output unit 16, and the communication pipe 17 are the same as each other, and the description thereof is omitted. The central processing unit 15C includes, for example, a microcomputer configured with a microprocessor, a storage circuit, and its peripheral circuits, and is functionally the same as the biological information processing unit 18B, the biological A linear conversion unit 19C that converts the nonlinear correlation between the three or more data pairs into a linear correlation using the three or more data pairs obtained by the information processing unit 18B, and linear conversion A degree-of-hardness measurement unit 20C for determining the degree of arterial stiffness H based on the straight line inclination α obtained from the data pair converted by the unit 19C, and the compression pressure control unit 12, the pressure detection unit 13, the pulse according to the control program By controlling the wave amplitude detection unit 14 and the output unit 16 in accordance with the function, the overall control of the arterial stiffness measuring device 1C is governed.

  Here, the arterial stiffness measuring apparatus 1C in the third embodiment uses a pressure-internal volume characteristic curve obtained from a pressure-pulse wave amplitude data pair (pulse wave envelope) as biological information, and uses this pressure- In this embodiment, three or more pairs of data forming the internal volume characteristic curve are linearly converted, and the arterial stiffness H is obtained based on the slope α of the straight line obtained from the converted data pair. In the embodiment, the second pressure logarithmic transformation is used for the linear transformation, but in the third embodiment, a differential transformation described later is used. Therefore, the biological information processing unit 18B includes a pulse wave processing unit 181, a pulse wave amplitude characteristic information storage unit 182, a pressure-internal volume characteristic conversion unit 183, and a pressure-internal volume characteristic information storage unit 184 similar to those in the second embodiment. The linear conversion unit 19C includes a pressure-internal volume characteristic difference linear conversion unit 191C, and the sclerosis degree measurement unit 20C includes a pressure-internal volume characteristic difference arterial wall sclerosis degree determination unit. 201C and a pressure-internal volume characteristic difference arterial wall hardening degree determination table storage unit 202C.

  The pressure-internal volume characteristic difference linear conversion unit 191C uses the three or more sets of pressure-internal volume data pairs stored in the pressure-internal volume characteristic information storage unit 184 to perform the three sets by a predetermined linear conversion algorithm. The non-linear correlation between the above data pairs is converted into a linear correlation.

  The pressure-internal volume characteristic difference arterial wall hardening degree determination table storage unit 202C stores a pressure-internal volume characteristic difference arterial wall hardening degree determination table. The pressure-internal volume characteristic difference arterial wall stiffness determination table is a table for determining the arterial stiffness H from the linear slope α obtained from the linearly converted pressure-internal volume data pair. In the embodiment, the table is obtained by associating the slope α of the straight line obtained from the linearly-transformed pressure-internal volume data pair and the degree of hardening of the arterial wall obtained by statistically examining in advance. The pressure-internal volume characteristic difference arterial wall hardening degree determination unit 201C is configured to determine the pressure-internal volume characteristic difference arterial wall hardening based on the straight line slope α obtained from the data pair converted by the pressure-internal volume characteristic difference linear conversion unit 191C. The arterial stiffness H is obtained by referring to the pressure-internal volume characteristic difference arterial stiffness determination table stored in the degree determination table storage unit 202C, and is output to the output unit 16.

Next, the operation of this embodiment will be described.
(Operation of Third Embodiment)
The operation of the arterial stiffness measurement apparatus 1C according to the third embodiment is the same as the operation shown in FIG. 6 of the arterial stiffness measurement apparatus 1B according to the second embodiment. Except for the difference in the processing method of S39), the operation is the same as the operation shown in FIG. 6 of the arterial stiffness measuring apparatus 1B in the second embodiment. For this reason, only the linear conversion processing of the pressure-internal volume data pair in the third embodiment will be described below.

  Here, the inventors set the predetermined internal / external pressure difference P as the reference internal / external pressure difference Ps, and when the internal volume V at the reference internal / external pressure difference Ps is set as the reference internal volume Vs, the internal / external pressure difference P is determined as the reference internal / external pressure difference Ps. The ratio ΔP / Ps of the value ΔP (= P−Ps) subtracted by the pressure difference Ps to the reference internal / external pressure difference Ps and the value ΔV (= V−Vs) obtained by subtracting the internal volume V by the reference internal volume Vs It has been found that a linear relationship is established between the ratio ΔV / Vs with respect to the reference internal volume Vs, and the slope α of the straight line reflects the arterial stiffness H well.

  Therefore, if the pressure-internal volume data pair is expressed as (Pn, Vn), the linear conversion by this difference conversion first arbitrarily sets the internal / external pressure difference P as the reference internal / external pressure difference Ps, and this reference internal / external pressure. The internal volume Vn corresponding to the difference Ps is set as a reference internal volume Vs. Next, the value ΔPn (= Pn (= Vn)) is obtained by dividing the pressure-internal volume data pair (Pn, Vn) by the reference internal / external pressure difference Ps and the reference internal volume Vs, respectively, and subtracting the internal / external pressure difference Pn by the reference internal / external pressure difference Ps. The ratio ΔP / Ps of the Pn−Ps) with respect to the reference internal / external pressure difference Ps and the ratio ΔVn (= Vn−Vs) of the value ΔVn (= Vn−Vs) obtained by subtracting the corresponding internal volume Vn with the reference internal volume Vs ΔVn A data pair (ΔPn / Ps, ΔVn / Vs) with / Vs is obtained.

  As described above, the arterial stiffness measuring apparatus 1C according to the third embodiment obtains the pressure-internal volume characteristic curve based on the pulse wave obtained by slow depressurization from the ischemic state. When pressure is applied to the artery, a pressure-internal volume characteristic curve reflecting the mechanical characteristics of the artery can be obtained. The arterial stiffness measurement apparatus 1C does not determine the arterial stiffness H from the shape of the pressure-internal volume characteristic curve itself, but linearly converts the curve shape of the pressure-internal volume characteristic curve, Since the determination is made from the straight line inclination α obtained by linear conversion, the arterial stiffness H can be easily and accurately determined. Since the slope α of this straight line is obtained from three or more pairs of data, the curve shape of the pressure-internal volume characteristic curve is better reflected, and the arterial stiffness H can be measured with higher accuracy.

  In the third embodiment, the linear transformation based on the difference transformation is applied to the pressure-internal volume data pair, but the same can be applied to the pressure-pulse wave amplitude data pair.

  Here, as can be seen from FIG. 7, there is a significant difference between the pressure-internal volume characteristic curve s in the soft artery and the pressure-internal volume characteristic curve h in the hard artery in a region where the internal / external pressure difference is 0 or more. Therefore, in the arterial stiffness measurement apparatuses 1B and 1C in the second and third embodiments described above, three or more pressure-internal volume data pairs used for obtaining the arterial stiffness H are the internal and external pressure differences. It is preferable that the data pair includes a data pair in which the internal / external pressure difference is 0 or more including a data pair in which 0 is zero. Alternatively, in view of the pulse wave envelope that is the basis for obtaining the pressure-internal volume characteristic curve, the arterial wall stiffness measuring apparatus 1A according to the first embodiment described above is used for obtaining the arterial stiffness H 3. The data pair of pressure-pulse wave amplitudes equal to or greater than the set may be a data pair related to a region on the lower pressure side than the compression pressure when the pulse wave amplitude includes the data pair having the maximum pulse wave amplitude. When three or more data pairs are used, the slope α of the straight line becomes a value that more appropriately reflects the difference in the arterial stiffness H, and the arterial stiffness H can be measured with higher accuracy.

  Then, the arterial stiffness measuring devices 1A, 1B, 1C in the first to third embodiments described above measure the pulse wave by detecting the pressure in the cuff 11 in the slow depressurization process by the pressure detection unit 13. However, instead of the pressure detection unit 13, an infrared light emission unit that emits infrared light and an infrared light reception unit that receives the infrared light and detects the amount of received light are provided. Using this infrared light detector and the infrared light detector arranged so that the reflected light of the infrared light irradiated to the artery is received by the infrared light receiver, the infrared light detector is used for slow depressurization. You may comprise so that a pulse wave may be measured by detecting the light quantity of the infrared light in a process. The infrared light emitting unit is, for example, an infrared light emitting diode, and the infrared light receiving unit is, for example, an infrared photodiode.

  Further, the arterial stiffness measurement apparatuses 1A, 1B, and 1C in the first to third embodiments described above are set so that the pressure in the cuff 11 becomes a predetermined pressure higher than the maximum blood pressure expected by the measurement subject. The pressure in the cuff 11 is increased and the pulse wave is measured in the subsequent slow depressurization process. Until the pressure in the cuff 11 reaches a predetermined pressure higher than the expected maximum blood pressure of the measurement subject, You may comprise so that a pulse wave may be measured in the slow pressurization process which pressurizes the pressure in the cuff 11 gradually. An example of the time change in the pressure of the cuff 11 in this case is shown in FIG.

  On the other hand, as described in the background art, since the blood pressure can be measured from the pulse wave envelope, the pulse wave is applied to the arterial stiffness measuring devices 1A, 1B, 1C in the first to third embodiments described above. A blood pressure measurement unit that measures blood pressure from the envelope may be further provided so that blood pressure can be measured. With this configuration, the cuff 11 for measuring the arterial stiffness H, the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, the pulse wave processing unit 181, and the pulse wave amplitude characteristic information The storage unit 182 can also be used to measure blood pressure, and an arterial stiffness measuring apparatus with a blood pressure measurement function can be configured compactly and inexpensively.

  As an example, an arterial stiffness measurement apparatus 2 in which a blood pressure measurement function is added to the arterial stiffness measurement apparatus 1A in the first embodiment will be described. As shown in FIG. Includes a cuff 11, a compression pressure control unit 12, a pressure detection unit 13, a pulse wave amplitude detection unit 14, a central processing unit 15 </ b> D, an output unit 16, and a communication pipe 17.

  The central processing unit 15D includes, for example, a microcomputer that includes a microprocessor, a storage circuit, and its peripheral circuits. The biological processing unit 18A that is functionally similar to the first embodiment, linearly It includes a conversion unit 19A and a curing degree measurement unit 20A, and further includes a blood pressure measurement unit 21 functionally, and the compression pressure control unit 12, the pressure detection unit 13, the pulse wave amplitude detection unit 14, and the output unit 16 according to the control program. It controls the entire arterial stiffness measuring apparatus 1D by controlling each function according to its function.

  The blood pressure measurement unit 21 obtains a pulse wave envelope from the pressure-pulse wave amplitude data pair stored in the pulse wave amplitude characteristic information storage unit 182 of the biological information processing unit 18A, and uses the obtained pulse wave envelope. A predetermined blood pressure is obtained, and the obtained blood pressure is output to the output unit 16. The predetermined blood pressure is, for example, an average blood pressure, a maximum blood pressure, and a minimum blood pressure. As can be seen from the description of the background art, the average blood pressure is measured from the compression pressure at which the pulse wave amplitude of the pulse wave envelope becomes the maximum pulse wave amplitude, and the maximum blood pressure is the pulse wave envelope of the pulse wave envelope on the higher pressure side than this average blood pressure. The systolic pressure is measured from the compression pressure at the inflection point, and the diastolic blood pressure is measured from the compression pressure at the inflection point of the pulse wave envelope on the side lower than the average blood pressure.

  And even if it is the same blood pressure, since the shape of the pulse wave envelope differs according to the arterial stiffness H, the arterial stiffness measuring devices 1A, 1B, 1C in the first to third embodiments described above are used. In addition to the blood pressure measurement unit that measures the blood pressure from the pulse wave envelope, a blood pressure correction unit that corrects the blood pressure measured by the blood pressure measurement unit according to the degree of arterial stiffness H may be further provided. With this configuration, blood pressure can be measured with higher accuracy.

  As an example, an arterial wall stiffness measuring device 2 ′ in which a blood pressure measuring function for correcting blood pressure based on the arterial stiffness H is added to the arterial stiffness measuring device 1 A in the first embodiment will be described. As shown, the blood pressure correction unit 22 is further functionally provided in the central processing unit 15D. The blood pressure correction unit 22 uses the correction function or the correction table to measure the blood pressure measured by the blood pressure measurement unit 21 with the arterial wall stiffness H measured by the pulse wave amplitude characteristic logarithmic arterial stiffness determination unit 201A of the stiffness measurement unit 20A. And the corrected blood pressure is output to the output unit 16. In the present embodiment, for example, in the present embodiment, the correction function and the correction table associate blood pressure, arterial stiffness H, and correction values obtained by statistically examining in advance.

  In the first embodiment, the compression pressure is used as the first biological information, and the pulse wave amplitude is used as the second biological information. In the second and third embodiments, the internal / external pressure is used as the first biological information. The arterial stiffness H was obtained using the internal volume of the artery as the second biological information using the difference. However, since the pulse wave area S and the pulse wave amplitude are correlated, the pulse wave area S is used instead of the pulse wave amplitude. May be used. That is, the arterial stiffness H may be obtained using the compression pressure as the first biological information and the pulse wave area S as the second biological information. The pulse wave area S is an area surrounded by the pulse wave and the horizontal axis (compression pressure). As an example, the pulse wave area S of the pulse wave 1002-4 shown in FIG. With this configuration, the signal-to-noise ratio (Signal to Noise Ratio) can be improved and the arterial stiffness H can be obtained more accurately.

It is a block diagram which shows the structure of the arterial wall hardening degree measuring apparatus in 1st Embodiment. It is a flowchart which shows operation | movement of the arterial wall hardening degree measuring apparatus in 1st Embodiment. It is a figure which shows the graph of the data pair (ln (Cn / Cs), A / As-1) in each area | region. It is a figure which shows the graph of the data pair (ln (Cn / Cs), A / As-1) in the whole area | region. It is a block diagram which shows the structure of the arterial wall hardening degree measuring apparatus in 2nd Embodiment. It is a flowchart which shows operation | movement of the arterial-wall-hardness measuring apparatus in 2nd Embodiment. It is a figure which shows a pressure-internal volume characteristic curve. It is a block diagram which shows the structure of the arterial wall hardening degree measuring apparatus in 3rd Embodiment. It is a figure which shows the time change in the pressure in the cuff in a slow pressurization process. It is a figure which shows the structure of the arterial wall hardening degree measuring apparatus which added the blood pressure measuring function to the arterial wall hardening degree measuring apparatus in 1st Embodiment. It is a figure which shows the time change of the pressure of the cuff in a slow depressurization process. It is a figure which shows the pulse wave and pulse wave envelope which were arranged in time series for every heartbeat. It is a figure which shows various pulse wave envelopes. It is a figure for demonstrating the measurement of the arteriosclerosis degree in patent document 1. FIG. It is a figure which shows the internal pressure-external radius characteristic in the minimum blood pressure to the maximum blood pressure.

Explanation of symbols

1A, 1B, 1C, 2, 2 ′ Arterial stiffness measurement apparatus 11 Cuff 12 Compression pressure control unit 13 Pressure detection unit 14 Pulse wave amplitude detection units 15A, 15B, 15C, 15D Central processing unit 16 Output unit 17 Communication pipe 18A Biological information processing unit 19A, 19B, 19C Linear conversion unit 20A, 20B, 20C Curing degree measurement unit 21 Blood pressure measurement unit 22 Blood pressure correction unit 181 Pulse wave processing unit 182 Pulse wave amplitude characteristic information storage unit 183 Pressure-internal volume characteristic conversion Unit 184 Pressure-internal volume characteristic information storage unit 191A Pulse wave amplitude characteristic logarithmic linear conversion unit 191B Pressure-internal volume characteristic logarithmic linear conversion unit 191C Pressure-internal volume characteristic difference linear conversion unit 201A Pulse wave amplitude characteristic logarithmic arterial wall stiffness determination Unit 201B Pressure-internal volume characteristic logarithmic arterial stiffness determination unit 201C Pressure-internal volume characteristic difference arterial stiffness determination unit 202A Pulse wave amplitude characteristic logarithmic arterial stiffness Determination table storage unit 202B Pressure-internal volume characteristic logarithmic arterial stiffness determination table storage unit 202C Pressure-internal volume characteristic difference arterial stiffness determination table storage unit

Claims (7)

A compression part that compresses a predetermined part of the living body;
A pressure detection unit for detecting the pressure of the compression unit;
A compression pressure control unit that changes a compression pressure at which the compression unit compresses the predetermined part; and
A pulse wave information detection unit that detects pulse wave information related to the magnitude of the pulse wave generated in the artery at the predetermined site by a heartbeat in the process of changing the compression pressure of the compression unit based on the detected pressure;
Based on the pulse wave information detected by the pulse wave information detection unit and the compression pressure of the compression unit at the time when the pulse wave information is detected, the heart rate in the process of changing the compression pressure of the compression unit A biological information processing unit for obtaining a data pair of first and second biological information based on deformation generated in the artery;
A linear conversion unit that converts a non-linear correlation between the three or more data pairs into a linear correlation using three or more data pairs obtained by the biological information processing unit;
An arterial stiffness measurement apparatus comprising: a stiffness measurement unit that obtains the arterial stiffness of the artery based on a slope of a straight line obtained from the data pair transformed by the linear transformation unit. The artery according to claim 1, wherein the data pair is a data pair on a pulse wave envelope in which the first biological information is the compression pressure and the second biological information is the pulse wave amplitude. Wall hardening degree measuring device. The three or more sets of data pairs are data pairs related to a lower pressure side region than the compression pressure when the pulse wave amplitude is maximum, including the data pair having the maximum pulse wave amplitude. 2. The arterial stiffness measurement apparatus according to 2. The data pair is a data pair on a pressure-internal volume characteristic curve in which the first biological information is an internal / external pressure difference of the artery and the second biological information is an internal volume of the artery. The arterial stiffness measurement apparatus according to claim 1. The arterial wall according to claim 4, wherein the three or more data pairs are data pairs related to a positive region in which the internal / external pressure difference is 0 or more, including a data pair in which the internal / external pressure difference is 0. Curing degree measuring device. The linear conversion unit uses the predetermined value of the first biological information as reference first biological information and the second biological information corresponding to the reference first biological information as reference second biological information. By calculating the logarithm of the value obtained by dividing the first biological information of the pair by the reference first biological information and calculating the value obtained by dividing the second biological information of the data pair by the reference second biological information, the 3 The arterial stiffness measurement apparatus according to any one of claims 1 to 5, wherein a non-linear correlation between at least a set of data pairs is converted into a linear correlation. The linear conversion unit uses the predetermined value of the first biological information as reference first biological information and the second biological information corresponding to the reference first biological information as reference second biological information. By calculating a value obtained by subtracting the reference first and second biological information from the pair of first and second biological information, respectively, by the reference first and second biological information, the three or more sets of the first and second biological information are obtained. The arteriosclerosis measuring apparatus according to any one of claims 1 to 5, wherein a nonlinear correlation between the data pairs is converted to a linear correlation.

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