JP2007313145A - Instrument for measuring blood vessel elastic property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an instrument for measuring arterial elasticity capable of utilizing a merit to obtain a transmural pressure difference in a blood vessel in blood pressure measurement using a cuff in order to measure the arterial elasticity. <P>SOLUTION: In a process to measure blood pressure by using the cuff of a double cuff method, the blood vessel transmural pressure difference beneath the cuff is defined as zero when cuff pressure is systolic blood pressure, and a blood vessel volumetric change when the cuff pressure falls from the systolic blood pressure by prescribed pressure within 20mmHg is defined as the blood vessel volumetric change when the blood vessel transmural pressure difference beneath the cuff is imposed by prescribed pressure. The blood vessel volumetric change is calculated based on pressure pulse wave detected in blood pressure measurement through the use of air-pressure conversion relation acquired based on a cuff pressure change when prescribed air capacity is injected. The acquired blood vessel volumetric change is divided by the maximum volumetric change value of the pulse wave detected in the blood pressure measurement so as to perform normalization, and then, obtained as the elastic index of the blood vessel beneath the cuff. Accordingly, the influence of baroreflex from a cuff periphery is eliminated and also the edge effect of the cuff and an individual difference are made to be the minimum concerning the blood vessel elastic property measuring instrument. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an apparatus for measuring arterial elasticity characteristics under a cuff by measuring a volume change of an arterial blood vessel under the cuff using a pressure pulse wave detected in non-invasive blood pressure measurement using an ischemic cuff. In particular, when arterial elasticity deteriorates using this phenomenon, the volume which increases when a prescribed intravascular external pressure difference is applied to the measurement blood vessel is reduced, and the degree is measured, and this relates to a vascular elastic property measuring apparatus which is used as an index of arterial elasticity. Is.

For cardiovascular diseases, there is a quantitative abnormality in the degree of lesion progression due to thickening of the arteriosclerosis, and the fibrous film on the surface of various species called unstable plaques is thin and fragile. There are abnormalities that cause bleeding, obstruction, and stenosis to cause angina, myocardial infarction, and cerebral infarction. The purpose of the measurement of arteriosclerosis is to prevent the occurrence of cardiovascular disorders by correctly evaluating the asymptomatic risk factors and the progress of arteriosclerosis. Devices that measure arteriosclerosis without recent invasion can be divided into vascular elasticity, pulse wave propagation speed, diagnosis of physiological parameters, and diagnostic imaging such as CT, MRI, and ultrasound. Diagnostic imaging is suitable for seeing the qualitative and quantitative progression of arteriosclerosis, but has not yet achieved sufficient performance in terms of resolution, and there is a risk of contrast agents. It is large-scale and is unsuitable for application to mass screening for the purpose of prevention. Compared to this, the measurement of physiological parameters can be performed easily in a short time, and the device can be realized on a relatively small scale, so it is suitable for screening screening for prevention like mass screening. ing.

Physiological parameter measurement methods include pulse wave velocity measurement method, acceleration pulse wave method, Augustaion Index (AI method), and Korotkoff sound spectrum method, all affected by symmetric arterial stiffness. This is a method of indirectly detecting mechanical changes. A blood vessel is a kind of elastic tube, and the elastic tube has a property that its elasticity changes with elongation. Hard when stretched and soft when not stretched. Therefore, vascular elasticity is influenced by the blood pressure value, which is the pressure in the blood vessel. For example, when the vasoelasticity is measured, when the systolic blood pressure is 180 mmHg and 150 mmHg, 150 mmHg is measured softer, and even though the physical properties of the artery do not change, the blood pressure decreases. Misleading as the degree of arteriosclerosis is improved. In clinical application, there is a drawback that correction is required due to blood pressure, which is the pressure in the arterial blood vessel.

Recently, in order to solve these drawbacks, a method has been proposed in which the elasticity of an artery can be directly measured, for example, in the brachial artery, and the elasticity of the artery is shown as an elastic change characteristic depending on a blood pressure value (Patent Document 1: Special). Kaihei 7-124129). This method is a method in which the change characteristic of elasticity due to the difference in pressure inside and outside the artery is simultaneously performed in a non-invasive blood pressure measurement method using a cuff for ischemia. Using the amplitude of the pulse wave detected at the time of blood pressure measurement by the OSC method using the photoelectric volume pulse wave or impedance pulse wave, the internal and external pressure-intra-arterial volume characteristic, which is a mechanical characteristic of the artery, is obtained to determine the arterial elasticity. Measure.
JP 7-124129 A

This method uses a cuff for ischemia and gradually changes the cuff pressure from the systolic blood pressure to the diastolic blood pressure and measures the photoelectric volume pulse or impedance pulse wave detected when measuring the blood pressure. As an arterial volume change, the Y axis is the pulse wave amplitude, the X axis is the intravascular external pressure difference value (internal blood pressure-external blood pressure (cuff pressure)) with the diastolic blood pressure as the reference for the intravascular external pressure difference, For all detected pulse waves, for each detected pulse wave on the X-axis, on the Y-axis due to the difference between the corresponding intravascular external pressure and the intravascular external pressure difference higher than the corresponding intravascular external pressure difference by the pulse pressure (systolic blood pressure-diastolic blood pressure) This is a method of plotting so that the + Δ change of becomes the pulse wave amplitude value, obtaining a regression curve thereof, and indicating this as an intra-arterial external pressure-intravascular volume characteristic (arterial elastic characteristic).

Patent Document 1 (Japanese Patent Application Laid-Open No. 7-124129) discloses a method for measuring arterial elasticity by determining intra-arterial / external pressure-vessel volume characteristics. In non-invasive blood pressure measurement using an ischemic cuff, cuff pressure is used. The pulse wave detected when the pressure is gradually changed from a pressure lower than the diastolic blood pressure to a pressure higher than the systolic blood pressure or from a pressure higher than the systolic blood pressure to a pressure lower than the diastolic blood pressure is used. When the cuff pressure is lower than the systolic blood pressure, this pulse wave flows into the arteries and venous blood vessels in the cuff's peripheral part (the forearm and hand when measuring with the upper arm) due to the blood flow flowing to the peripheral side of the cuff. The blood gradually accumulates, and the blood pressure inside the cuff peripheral blood vessel rises. This increase in pressure impedes blood flow under the cuff and reduces the generation of K sounds (Korotkoff sounds). On the other hand, the pressure applied in the radial direction of the cuff blood vessel is increased. When this pressure rises, a phenomenon occurs in which the amplitude of the pulse wave increases. This phenomenon usually occurs while the cuff pressure is from the systolic blood pressure to the average blood pressure, and affects the intra-arterial / external pressure-blood vessel volume characteristic obtained from this pulse wave. In addition, when the blood vessel is thick, the change in the blood vessel volume with respect to the pressure difference between the inside and outside of the blood vessel becomes large, so that the blood vessel compliance is measured larger than that when the blood vessel is thin, and it is affected by individual differences in the blood vessel thickness. have. In order to solve this problem, it is necessary to measure the diameter of the blood vessel using an ultrasonic tomography device or CT, which is a considerably large-scale examination, which is a great obstacle to use for preventive purposes such as health checkups. In addition, when the cuff for ischemia is wound around the measurement site, the center of the cuff in the width direction of the cuff has the strongest force to compress the measurement site, and the force of pressing in the both ends of the cuff in the width direction is attenuated. Has an edge effect where the pressing force is zero. The edge effect varies depending on the cuff structure, the winding method, and the thickness of the measurement site. The length of the artery to be measured under the cuff becomes unknown for each individual and for each measurement, and there is a problem that comparison between measured values cannot be performed.

Examining the relationship between the change in the inner diameter of an elastic tube made of an elastic material such as latex and the internal / external pressure difference (internal pressure-external pressure), when the internal / external pressure difference goes from a negative state to a positive state, A characteristic phenomenon that shows a large change in inner diameter is observed. In addition, if only the thickness of the tube wall is changed without changing the material of the elastic tube, it will not be able to be closed unless the external pressure is increased, and it will occur when the pressure difference inside the tube is increased from the closed state. There is a phenomenon that sudden changes in the inner diameter are less likely to occur. This phenomenon is very similar to that of arterial blood vessels when arteriosclerosis occurs. The present invention relates to a measurement apparatus that uses this phenomenon, and when the arterial elasticity deteriorates, the volume that increases when a prescribed intravascular / external pressure difference is applied to the measurement blood vessel is reduced, and the degree is measured and used as an index of arterial elasticity. Is. The arterial blood vessel under the cuff is a tube with elastic properties, and like the elastic tube, when the blood vessel wall thickness is normal and the normal pressure difference between the blood vessel and the blood vessel is positive, the capped blood vessel opens rapidly Have When arteriosclerosis is caused and the blood vessels are thickened, there is a phenomenon that the blood vessel compliance becomes small and the blood vessels are difficult to open. The intra- and external-pressure difference (intravascular pressure (blood pressure)-external blood pressure (cuff pressure)) applied to the blood vessel under the cuff at the time of blood pressure measurement is zero when the cuff pressure matches the systolic blood pressure, and the cuff pressure is the systolic blood pressure. When ΔP is further lowered, this is equivalent to the fact that ΔP has an intravascular pressure difference applied to the blood vessel under the cuff. That is, blood pressure measurement with a cuff wrapped around a measurement site is a method that can conveniently apply a difference in internal and external pressure to a blood vessel. However, in the blood pressure measurement process, when the cuff pressure is gradually reduced and the cuff pressure becomes lower than the systolic blood pressure, the blood pressure flowing toward the cuff distal side causes a phenomenon that the intravascular pressure on the cuff distal side gradually increases. . When the pressure on the peripheral side approaches the cuff pressure, pressure reflection from the peripheral side occurs, causing a phenomenon in which the volume change under the cuff increases, which has a significant effect on the measurement of the relationship between the intravascular external pressure difference and the volume change There is a point.

The present invention has been made in view of the above problems, and sets the intravascular external pressure difference for measuring the elasticity of the artery as small as possible, and the internal pressure side of the cuff peripheral blood vessel rises due to the blood pumping out to the cuff peripheral side. An arterial elasticity measurement device that eliminates the effects of pressure reflection from the cuff distal side by measuring before approaching the pressure, and makes use of the advantage that the blood pressure measurement method using the cuff can be conveniently applied to the blood pressure inside and outside the blood vessel is provided. There is.

In order to achieve the above object, the blood vessel elastic characteristic measuring device according to the present invention is a pulse wave detecting air bag located between a measuring site at a substantially central portion of the ischemic air bag and the ischemic air bag and the ischemic air bag. Cuff with pressure, pressurizing means for pressurizing the cuff, exhaust and decompression means for leaking air from the cuff, pressure detection for detecting the cuff pressure of the air bag for ischemia and the pulse wave from the air bag for detecting the pulse wave Means, signal processing means for amplifying and separating the cuff pressure and the pressure pulse wave signal from the signal from the pressure detection unit and converting them into a digital signal, and air injection for injecting a specified air volume into the pulse wave detection air bag at a constant speed Means, a volume estimation means for estimating a change in blood volume under the cuff from the pressure pulse wave signal when the blood pressure under the cuff at the time of systolic blood pressure is zero, and when the pressure falls below the systolic blood pressure, and a maximum under the cuff. Maximum volume estimation to estimate blood vessel volume change from pressure pulse wave Stage and is characterized in that it has a volume normalization means for normalizing with said maximum volume change of the cuff under arterial volume change when dropped specified pressure from systolic blood pressure. The specified pressure value is 20 mmHg or less. In addition, the air injection means includes a syringe pump and a syringe capable of injecting a constant speed and a constant volume. Further, the volume estimation means is characterized in that, under the cuff pressure of systolic blood pressure, the transfer function is obtained when the injection volume waveform of the air injected by the air injection means is input and the change in cuff pressure is output. The maximum volume estimating means is characterized in that, under the cuff pressure of the diastolic blood pressure, an input volume waveform of the air injected by the air injecting means is input and a transfer function is obtained when a change in cuff pressure is output. The volume normalizing means is characterized in that it is performed by dividing the subcuff blood vessel volume when the pressure is lower than the systolic blood pressure obtained by the volume estimating means by the maximum volume change under the cuff.

In addition, the blood vessel elastic property measuring apparatus of the present invention has a blood pressure detecting air bag for blocking blood vessels at a measurement site, a blood pressure detecting air bag, and a pulse wave detection air bag at a substantially central portion in the cuff width direction between the measurement sites. The cuff and the signal from the pressure sensor are separated from the cuff pressure of the air bag for ischemia and the pressure pulse wave detected by the air bag for pulse wave detection, and converted into a digital signal, and the cuff is pressurized. Pressurization means, exhaust / decompression means for leaking air from the cuff, blood pressure measurement data detection section for detecting pulse wave and cuff pressure data for blood pressure measurement by the double cuff method, and blood pressure measurement section for determining blood pressure A blood pressure measuring means comprising: an air injecting means for injecting a prescribed air volume into a pulse wave detection air bag at a constant speed; Cuff generated by change in volume of air injected by injection means From the change, the transfer function when the volume of the injected air is input and the change in the cuff pressure generated thereby is output is obtained. Using this transfer function, the pulse wave that is one beat higher than the systolic blood pressure is specified from the systolic blood pressure. A volume change detecting unit 1 that estimates a volume change corresponding to a pressure pulse wave that has been detected up to a pulse wave that is one beat lower than the reduced pressure, and a blood vessel volume with a cuff pressure that is a prescribed pressure lower than the systolic blood pressure is the volume. Generated by the volume change of the injected air in the same manner as the volume estimation means comprising the volume estimation section estimated from the volume change obtained by the change detection section 1 and the cuff pressure being increased to the approximate diastolic blood pressure value and held. From the change in cuff pressure, the transfer function when the volume of the injected air is input and the change in cuff pressure generated as a result is output is obtained. Using this transfer function, the cuff pressure is higher than the diastolic blood pressure by a specified pressure. Detected by A volume change detecting unit 2 for obtaining a volume change corresponding to a pulse wave; a maximum volume estimating unit comprising a maximum volume change estimating unit for obtaining a maximum value from the obtained volume change and estimating a maximum volume change amount; and The volume normalization means for calculating the ratio between the volume change estimated value obtained from the above and the maximum volume change estimated value obtained from the maximum value estimating means, and the blood vessel volume change rate and error signal, which are normalized volumes of the calculation results, It consists of a display unit that displays. The blood pressure measurement data detector of the blood pressure measurement means raises the cuff pressure from the systolic blood pressure to about 30 mmHg, and then gradually reduces the cuff pressure at a substantially constant predetermined pressure reduction rate of 2 to 3 mmHg / sec. Then, until the cuff pressure becomes lower than the diastolic blood pressure, the cuff pressure and the pressure pulse wave signal superimposed on the cuff pressure are separated and recorded in pairs in the internal memory every 10 ms (predetermined every second). To do. The blood pressure measurement unit of the blood pressure measurement means checks the amplitude of the pressure pulse wave signal recorded in the blood pressure measurement data detection unit in time series after the cuff decompression is started, and the amplitude suddenly increases. The cuff pressure is recorded as systolic blood pressure, and the cuff pressure when the amplitude starts decreasing is recorded as diastolic blood pressure. The volume change detection unit 1 of the volume estimation means detects the cuff and the compliance of the living body as a transfer function in a state in which the systolic blood pressure value is pressurized after the blood pressure measurement is finished. With pressurization and pressure held again, the air injection pump injects a specified amount of air close to the volume change of the pulse wave into the pulse wave detection cuff in a rectangular wave shape, and detects the pressure change generated by this injection Then, using the volume as the input value and the cuff pressure change at that time as the output value, the transfer function between the input and output is obtained. The volume estimation unit of the volume estimation means includes a pulse wave first detected at a cuff pressure higher than a pressure value obtained by reducing a prescribed pressure value from the systolic blood pressure recorded in the blood pressure measurement data detection unit, and a systolic period An average value of volume changes corresponding to a pulse wave first detected at a cuff pressure lower than the pressure value obtained by reducing the prescribed pressure value from the blood pressure is obtained and stored in the data storage unit. The volume change detector 2 of the maximum volume estimator obtains the transfer function using the cuff pressure of the diastolic blood pressure as in the volume pulse wave detector 1. The volume change of the pulse wave is obtained from the pressure pulse wave detected between the diastolic blood pressures from the pressure whose cuff pressure is higher than the diastolic blood pressure by a specified pressure value, and recorded in the internal memory. The maximum volume estimation unit obtains the maximum volume change value recorded at the time of blood pressure measurement in order to obtain the volume when the blood vessel under the cuff is fully opened. The maximum volume change is detected from the volume change with respect to the pulse wave detected from the cuff pressure higher than the diastolic blood pressure recorded in the data storage unit to the diastolic blood pressure and recorded in the memory. Volume normalization means is in the systolic phase until the blood vessel is closed in the central part of the cuff ischemic air bag, which is not caused by the blood flow flowing to the cuff peripheral side, to the vicinity of the vascular pressure closure site. In order to eliminate the volume change caused by the blood flow entering from the cuff upstream portion, the volume corresponding to the pulse wave immediately before the systolic blood pressure point is stored in the central pulse wave detection air bag of the ischemic cuff. The change in the volume of the blood vessel under the cuff and the noise removal unit is larger when the blood vessel is thicker than when it is thin, and there is a variation due to individual differences in the diameter of the blood vessel.To eliminate this variation, the blood vessel under the cuff It consists of a normalization part which normalizes with the volume which will be in a fully open state. In the normalization unit, the volume of noise recorded in the memory is subtracted from the volume change recorded in the memory, and the volume of noise is similarly subtracted from the maximum volume change. Divide by one, multiply by 100, convert to%, and store in the memory as the blood vessel opening ratio. The display unit displays an error when measurement is not possible due to artifacts such as systolic blood pressure value, diastolic blood pressure value, blood vessel volume change rate, and body movement artifacts and noise stored in the memory. The contents are displayed on an LCD or the like.

In the method of determining arterial elasticity by determining intra-arterial / external pressure-vessel volume characteristics disclosed in Patent Document 1, the cuff pressure is lower than the diastolic blood pressure in non-invasive blood pressure measurement using an ischemic cuff. The pulse wave detected when the pressure is gradually changed from a pressure higher than the systolic blood pressure to a pressure lower than the diastolic blood pressure is used. When the cuff pressure is lower than the systolic blood pressure, this pulse wave flows to the arterial and venous blood vessels in the peripheral part of the ischemic cuff (forearm and hand when measured with the upper arm) due to the blood flow flowing to the distal side of the cuff The blood gradually accumulates, and the blood pressure inside the cuff peripheral blood vessel rises. This increase in pressure will impede blood flow under the cuff. On the other hand, the pressure applied in the radial direction of the blood vessel is increased. When this pressure rises, a phenomenon occurs in which the amplitude of the pulse wave increases. This phenomenon occurs while the cuff pressure changes from the systolic blood pressure to the average blood pressure, and affects the intra-arterial / external pressure-blood vessel volume characteristic obtained from this pulse wave. However, according to the vascular elastic property measuring apparatus of the present invention, the specified pressure of the intravascular external pressure difference is a large value such that the blood pressure on the cuff distal side due to the pumping approaches the cuff pressure and the influence of baroreflex from the cuff peripheral appears. This effect can be eliminated by not making it. In addition, when the blood vessel is thick, the change in the blood vessel volume with respect to the pressure difference between the inside and outside of the blood vessel becomes large, so that the blood vessel compliance is measured larger than that when the blood vessel is thin, and it is affected by individual differences in the blood vessel thickness. have. In addition, when the cuff for ischemia is wound around the measurement site, the center of the cuff in the width direction of the cuff has the strongest force to compress the measurement site, and the force of pressing in the both ends of the cuff in the width direction is attenuated. Also has an edge effect where the pressing force is zero. This edge effect has a problem that it varies depending on the structure of the cuff, how to wind the cuff, and the thickness of the measurement site. To solve this problem, it is necessary to measure and correct the cuffed blood vessel compression situation using an ultrasonic tomograph or CT. This is a very large test and can be a major obstacle to preventive purposes such as health checkups. On the other hand, according to the blood vessel elastic property measuring apparatus of the present invention of the present invention, by detecting the pulse wave with the pulse wave detecting air bag completely covered with the central part of the air bag for ischemia, By detecting the pulse wave with a cuff that is uniformly compressed to the edge, and by maximizing the vascular volume change under the specified vascular internal / external pressure difference with the maximum vascular volume under the cuff, the individual of the vascular diameter It is possible to measure arterial elastic characteristics excluding the influence of the difference and the cuff edge effect.

Embodiments of the present invention will be described below with reference to the drawings. In addition, an Example is an example and is not limited to this. FIG. 1 is a block diagram showing the configuration of the arterial elasticity measurement system of this embodiment. The arterial elasticity measuring device 30 includes a cuff 1 for a so-called double cuff system, and a cuff 1 for a so-called double cuff system, which has an air bag for ischemia (ischemic cuff) 2 and a bag for detecting a pulse wave (cuff for detecting a pulse wave) 3 attached to a measurement site. Exhaust and decompression means by a valve 6 having both the function of opening 1 air to the atmosphere, the function of sealing, and the function of gradually exhausting, the pressurizing means by a pressurizing pump 7 that pressurizes the cuff 1, and the cuff 1 measure A pressure sensor 8 for detecting a cuff pressure signal for pressurizing a part, a pressure pulse wave signal for detecting a pulse wave detection air bag 3 superimposed on the cuff pressure signal, and a pressure pulse detected by the pulse wave detection air bag 3 A fluid resistance 5 and a buffer tank constituting a mechanical filter for attenuating only the pressure pulse wave signal detected by the ischemic air bladder 2 to detect only the wave signal and detecting only the ischemic pressure of the ischemic air bladder 2 4 and Am to amplify the signal 9, a filter 10 that separates the pressure pulse wave signal superimposed from the cuff pressure signal, and an A / D converter that converts the pressure pulse wave signal separated from the cuff pressure signal into a digital signal and sends it to a CPU (central control unit) 13. The cuff 1 is cuffed from the cuff 1 while the cuff 1 is pressurized by the pressurizing pump 7 above the systolic blood pressure and reduced to a cuff pressure below the diastolic blood pressure by the valve 6 at a constant speed. The blood pressure measurement data detector (1) 14 that measures the pressure pulse wave and stores it in the blood pressure measurement database 22 of the storage unit 20, and the cuff pressure stored in the blood pressure measurement database 22 The blood pressure measurement unit 15 obtains systolic blood pressure and diastolic blood pressure using the pressure pulse wave and stores them in the blood pressure value database of the storage unit 23, and is used to obtain the volume pulse wave from the pressure pulse wave In order to obtain a transfer function to be stored, after blood pressure measurement, it is stored in the blood pressure value database 23. The cuff 1 is pressurized again to the systolic blood pressure value, and the cuff pressure is held. The air injection pump 12 injects a specified amount of air at a specified speed, and the cuff 1 changes at that time. Is detected from the signal of the pressure sensor 8, a transfer function is obtained, and using the transfer function, a volume change is calculated from the pressure pulse wave stored in the blood pressure measurement database, and the data storage unit 20 The volume change detection unit (1) 16 stored in the volume database 24 and the cuff pressure is again pressurized to the diastolic blood pressure value, and the cuff pressure is held by the air infusion pump 12. An amount of air is injected at a specified speed, the change in cuff pressure of the cuff 1 at that time is detected from the signal of the pressure sensor 8, a transfer function is obtained, and the transfer function is used to obtain a blood pressure measurement database. The volume change is calculated from the stored pressure pulse wave and the volume data in the data storage unit 20 is calculated. -From the volume change detection unit (2) 17 stored in the source 24 and the data in which the volume change stored in the volume database 24 and the intra-vascular external pressure difference are paired, the noise removal unit 18 In order to remove noise generated in the upstream part of the cuff, the change in blood vessel volume when a prescribed internal / external pressure difference is applied to the blood vessel under the cuff is estimated, and the maximum volume change is performed in the normalization unit 19 Is normalized and stored in the memory (4) 28 of the data storage unit 20. The display unit 21 for outputting the measured systolic blood pressure value and diastolic blood pressure value, using the blood vessel volume change rate when the prescribed intravascular external pressure difference as the final result is applied as an index of arterial elasticity, and control of each department And a CPU 13 for performing calculations, a data storage unit 20 for storing various data, and a main bus for connecting the respective components. Reference numeral 13a denotes a ROM (EEPROM) in which a control program and the like for the entire apparatus 30 are stored, and reference numeral 13b denotes a RAM, which is read from the CPU 13 to execute control (processing flow) for the entire apparatus 30.

FIG. 2 is a flowchart showing the entire processing flow in the arterial elasticity measuring apparatus according to the embodiment of the present invention. In step S201, data obtained by pairing the pressure pulse wave and cuff pressure necessary for blood pressure measurement are measured at a constant sampling rate while reducing the pressure at a constant speed, and stored in the blood pressure measurement database. A specific data collection method will be described later with reference to FIG.
In step S202, systolic blood pressure and diastolic blood pressure are calculated using the data stored in the blood pressure measurement database 22, and stored in the blood pressure value database 23. A specific blood pressure determination method will be described later with reference to FIG.

In step S203, the cuff pressure is increased again to the systolic blood pressure value and the diastolic blood pressure value at which the pulse wave volume is to be measured, held at the cuff pressure, and the specified air volume is injected at the specified speed. The change in cuff pressure at that time is collected, a transfer function when the volume is input and the cuff pressure is output is obtained, and the pressure pulse wave data stored in the blood pressure measurement database 22 is obtained using this transfer function. From the data, the blood vessel volume change when the prescribed pressure is reduced from the systolic blood pressure value and the maximum volume change due to the pulse wave are calculated. A specific volume change measurement method, a specific prescribed air volume injection method, and a method for obtaining a specific transfer function will be described later with reference to FIGS. 5, 6, and 7. In step S204, the ratio of the change in blood vessel volume when a prescribed internal / external pressure difference is applied to the blood vessel under the cuff is calculated to the extent of the total blood vessel volume under the cuff. In step S205, the calculation result is output to the display unit as the blood vessel opening ratio, and together with the measured systolic blood pressure value and diastolic blood pressure value. A specific method for calculating (calculating) the blood vessel volume change rate will be described later with reference to FIGS. 8, 10, and 11.

FIG. 3 is a flow chart showing a detection flow of blood pressure measurement data according to the embodiment of the present invention. In step S301, the pressure sensor is zero-set. The valve is closed in step S302, the pressurizing pump 7 is turned on in step S303, a pressure higher than a systolic blood pressure (for example, a pressure higher by about 30 mmHg) is set as a target cuff pressure, and the cuff pressure is set in step S304. It is checked whether the cuff pressure has been reached. If the target cuff pressure is exceeded, the pressure pump 7 is turned off in step S305. In step S306, the valve 6 is controlled, and the cuff pressure is started to be reduced at a pressure reduction speed of 2 to 3 mmHg / sec. When the pressure reduction starts, the cuff pressure and pressure are detected at predetermined intervals (for example, every 10 ms) from the A / D converter in step S307 until it is detected in step S308 that the cuff pressure has become 30 mmHg or less. By repeatedly acquiring the pulse wave signal and storing it in the blood pressure measurement database 22, time series data in which the cuff pressure and the pressure pulse wave signal are paired is created. When the cuff pressure becomes 30 mmHg or less, the valve 6 is opened to atmospheric pressure in step S309.

FIG. 4 is a flowchart showing a blood pressure value determination method according to the embodiment of the present invention. In step S401, the pressure pulse wave data stored in the blood pressure measurement database 22 is searched for a change in signal from the oldest to the newer one, and if a sudden rise point is detected, the pulse wave data If the following convex point is detected as a peak point as a bottom point, this bottom and peak are detected as a pair of pressure pulses. The cuff pressure value at the bottom point is stored in the blood pressure measurement database 22 as the cuff pressure of the pressure pulse wave from the peak of the pressure pulse wave detected in step S402 as the amplitude. This is repeated until the END of the time series data every 10 ms of the blood pressure measurement database 22 is detected in step S403. In step S404, the blood pressure measurement database 22 stores the blood pressure. The amplitude of the pressure pulse wave and the cuff pressure value are paired, and the amplitude of the pressure pulse wave is retrieved from the oldest to the newest in the time series data time, and the first pressure pulse wave that has increased stepwise is used as the systolic blood pressure. As a point, the cuff pressure value paired with the pressure pulse wave is stored in the blood pressure value database 23 as a systolic blood pressure value. In step S405, the database is searched in a time direction newer than the systolic blood pressure point, the pulse wave amplitude is maximized, and the pulse wave at the first decreased point is paired with this pressure pulse wave as the diastolic blood pressure point. The cuff pressure value is stored in the blood pressure value database 23 as a diastolic blood pressure value.

FIG. 5 is a flowchart showing the entire volume change detection according to the embodiment of the present invention. When the cuff pressure is the systolic blood pressure value in step S501, the fluid injection volume signal (air injection volume signal) injected by the air injection means (air injection pump) 12 as the fluid injection means is input and generated Obtain the transfer function when the cuff pressure signal is output. Similarly, in step S502, the transfer function when the air injection volume signal when the cuff pressure is the diastolic blood pressure value is input and the cuff pressure signal is output is obtained. In step S503, using the transfer function when the cuff pressure is the systolic blood pressure value, from the pressure pulse wave detected one beat before the systolic blood pressure point to the cuff pressure that has fallen by the prescribed pressure from the systolic blood pressure value The volume change of the pressure pulse wave detected first at the cuff pressure lower than the cuff pressure lower than the specified pressure from the systolic blood pressure value is calculated. In step S504, using the transfer function when the cuff pressure is the diastolic blood pressure value, the volume change of the pressure pulse wave detected up to the diastolic blood pressure point is calculated from the cuff pressure higher than the diastolic blood pressure by the specified pressure. To do.

FIG. 6 shows a predetermined fluid volume (air volume) injected at a constant speed in the form of a rectangular wave to obtain the transfer function in steps S501 and S502 of the entire volume change detection flowchart shown in FIG. A specific method for measuring the change in cuff pressure is shown. In step S601, the valve 6 is closed and the pressure pump 7 is turned on. Whether the cuff pressure has reached the target cuff pressure is checked in step S602. When the cuff pressure exceeds the target cuff pressure, the pressurizing pump 7 is turned off in step S603. In step S604, the system waits for a predetermined time (for example, about 10 seconds) until the pressure system including the cuff settles. When a predetermined time (for example, 10 seconds) elapses, the cuff pressure is read from the A / D converter 11 every predetermined time (for example, 10 ms) in step S605 and is stored in the volume database 24. In step S606, the air injection means 12 injects a predetermined amount of air close to the actual volume change of the pulse wave of the human body in a rectangular wave shape at a constant speed. After completion of air injection in step S607, a predetermined second (for example, about 10 seconds) is waited until the air system is stabilized. When a predetermined time (for example, about 10 seconds) has elapsed, cuff pressure data collection is terminated in step S608. In step S609, the valve 6 is opened to atmospheric pressure.

FIG. 7 shows a specific method for obtaining the transfer function in steps S501 and S502 of the entire volume change detection flowchart shown in FIG. In step S701, the input infused air volume (injected fluid volume) is set as Qn, and the output is set as the cuff pressure change Yn that varies depending on the infused air. Since it is considered equivalent to a state in which the input and output are connected in parallel, the following recurrence formula (1) is established between the input and output.
_{Y n = A (Q n +} Q n-1) + BY n-1 (1)
The coefficients A and B are obtained by the least square method using the volume data of the air injected into the measured volume database 24 and the cuff pressure change data. In order to evaluate the validity of the recurrence formula obtained in step S702, the pressure change calculated using the recurrence formula (1) using the volume data of the injected air, and the actual measured volume data. A correlation coefficient with the cuff pressure change stored in the table 24 is obtained. It is checked whether the correlation coefficient obtained in step S703 is greater than or equal to a predetermined value (for example, 0.95 or higher). In step S705, an error is output to the display unit 21 and the measurement is interrupted and terminated. When the correlation coefficient is not less than a predetermined value (for example, not less than 0.95), the recurrence formula (1) is stored as the calculated transfer function.

FIG. 8 is a flowchart showing a blood vessel volume change rate calculation method according to the embodiment of the present invention. In step S801, the change in blood vessel volume when the prescribed pressure is reduced from the systolic blood pressure is calculated to obtain the change in blood vessel volume when the prescribed internal / external pressure difference is applied to the blood vessel under the cuff. In step S802, the maximum volume change value is obtained from the volume change stored in the volume database 24. In step S803, in order to normalize the vascular volume change when the specified internal / external pressure difference is applied to the blood vessel under the cuff by the maximum volume under the cuff, the obtained blood vessel volume change is divided by the obtained maximum volume change value. Calculate the vessel opening rate.

FIG. 10 shows a specific preferred embodiment of step S801 of the blood vessel volume change rate calculation method flowchart shown in FIG. In step S1001, the volume change of the pulse wave initially detected at the cuff pressure lower than the cuff pressure P lower than the systolic blood pressure value from the volume database 24 is detected to be Vn _{+ 1} . . Similarly, in step S1002, the volume change of the pulse wave first detected by the cuff pressure higher than the cuff pressure P lower than the systolic blood pressure value by the specified cuff pressure P is detected from the volume database 24. _{Let n-1} . In step S1003, V _n = (V _n−1 + V _{n + 1} ) / 2 is obtained. In step S1004, a cuff pressure value higher than the systolic blood pressure value is removed in order to eliminate volume change noise caused by the blood flowing into the cuff pressure closure part from the central side of the cuff at a cuff pressure higher than the systolic blood pressure. first detected in which the pulse wave volume changes the volume data of in - eat - as noise component so determined from the scan 24, a value obtained by subtracting from the V _n, as arterial volume change when added intravascular external pressure difference defined Record.

FIG. 11 shows a specific example of step S802 of the blood vessel opening ratio calculation method flowchart shown in FIG. In step S1101, the volume de - Eat - from scan 24, detects the maximum value _{V max} of the volume change. In step S1102, even in a state where the blood vessel is ischemic, the contraction is performed in order to eliminate volume change noise generated by the blood flow entering the cuff closed portion from the central side of the air bag 2 of the cuff 1. The volume change of the pulse wave first detected with a cuff pressure value higher than the blood pressure value in the period is obtained from the volume database 24, and this is used as a noise component, and the value subtracted from Vmax is the _maximum value of the blood vessel volume change. Record as. FIG. 9 shows a specific calculation method of steps S502 and S503 of the volume change detection method flowchart of FIG. Since the high frequency component is not included in the volume change signal of the pulse wave, the recurrence formula for determining the volume change is the data volume of the cuff pressure change which is the pressure pulse wave to be substituted with Q _n for the data volume to be obtained. motor when the column _{Y n Q n = (Q n} + Q n-1) / 2 = (1/2) × ((Y n -BY n-1) / a) (2)
And

It is a block diagram which shows the structure of the arterial elasticity measuring system of the Example of this invention. It is a flowchart which shows the whole process flow in the arterial elasticity measuring apparatus of the Example of this invention. 2 is a flowchart showing a detection flow of blood pressure measurement data according to an embodiment of the present invention. It is the flowchart which showed the blood-pressure value determination method of the Example of this invention. 1 is a flowchart showing the entire volume change detection of an embodiment of the present invention. Measures the change in cuff pressure when a prescribed air volume is injected at a constant speed in a rectangular wave shape to obtain the transfer function in steps S501 and S502 of the entire volume change detection flowchart shown in FIG. It is a figure which shows the specific method to do. FIG. 6 is a diagram showing a specific method for obtaining a transfer function in steps S501 and S502 of the entire volume change detection flowchart shown in FIG. 5; 1 is a flowchart showing a blood vessel volume change rate calculation method according to an embodiment of the present invention. FIG. 6 is a diagram showing a specific calculation method of steps S502 and S503 of the volume change detection method flowchart of FIG. 5; It is a figure which shows the specific Example of step S801 of the vascular volume change rate calculation method flowchart shown in FIG. It is a figure which shows the specific Example of step S802 of the vascular volume change rate calculation method flowchart shown in FIG.

Explanation of symbols

1 cuff, 2 air bag for ischemia, 3 air bag for pulse wave detection, 8 pressure sensor 12 air injection means, 13 CPU, 13a ROM, 13b RAM, 14 blood pressure measurement data detection unit, 15 blood pressure measurement unit, 16 volume change detection Unit (1), 17 volume change detection unit (2), 19 normalization unit, 20 data storage unit, 21 display unit, 22 blood pressure measurement database, 23 blood pressure value database, 24 volume database, 30 arterial elasticity measurement device

Claims (6)

  A cuff having a pulse wave detection air bag positioned between the measurement site in the central part of the air bag for ischemia and the air bag for ischemia and a blood bag for detecting a pulse wave located between the air bag for ischemia, a pressurizing means for pressurizing the cuff, and the cuff Exhaust and decompression means for leaking air, pressure detection means for detecting the cuff pressure of the air bag for ischemia and the pulse wave from the air bag for pulse wave detection, and cuff pressure and pressure pulse wave from the signal from the pressure detection unit Signal processing means for amplifying and separating signals and converting them into digital signals, air injecting means for injecting a prescribed air volume into the pulse wave detection bladder at a constant speed, and zero cuff blood vessel volume during systolic blood pressure A volume estimation means for estimating a cuff blood vessel volume change from a pressure pulse wave signal when a prescribed pressure falls below systolic blood pressure, a maximum volume estimation means for estimating a maximum blood vessel volume change under the cuff from a pressure pulse wave, The subcuff vascular volume when the specified pressure falls below the systolic blood pressure Cuff under blood vessel elasticity characteristic measuring apparatus characterized by having a volume normalization means for normalizing with said maximum volume change changes. The apparatus according to claim 1, wherein the specified pressure value is 20 mmHg or less. 2. The subcuff blood vessel elastic characteristic measuring device according to claim 1, wherein the air injection means comprises a syringe pump and a syringe capable of injecting a constant speed and a constant volume. The volume estimation means obtains a transfer function when an injection volume waveform of air injected by the air injection means is input and a change in cuff pressure is output under the cuff pressure of the systolic blood pressure. The sub-cuff blood vessel elastic characteristic measuring device according to claim 1. The maximum volume estimation means obtains a transfer function when an injection volume waveform of air injected by the air injection means is input and a change in cuff pressure is output under the cuff pressure of the diastolic blood pressure. Item 2. The cuff vascular elasticity measurement apparatus according to Item 1. 2. The volume normalizing means is performed by dividing a subcuff blood vessel volume when a prescribed pressure is lower than a systolic blood pressure obtained by the volume estimating means by a maximum volume change under the cuff. Cuff vascular elasticity measurement device.

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