CN102551714A

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Info

Publication number: CN102551714A
Application number: CN2012100398005A
Authority: CN
Inventors: 覃开蓉; 陈英
Original assignee: ZHOUZHOU NEW TIMES ENVIRONMENTAL PROTECTION TECHNOLOGY Co Ltd; Dalian University of Technology
Current assignee: ZHOUZHOU NEW TIMES ENVIRONMENTAL PROTECTION TECHNOLOGY Co Ltd; Dalian University of Technology
Priority date: 2012-02-21
Filing date: 2012-02-21
Publication date: 2012-07-11

Abstract

本发明公开了一种动脉内皮功能的电阻抗检测装置及方法，属于医疗仪器技术领域。本发明的装置包括前臂上电极、前臂下电极、高频低幅恒流源发生器、交流电压检测电路、信号放大器、滤波电路、A/D转换电路和计算机。交流电压检测电路检测电压变化，交流电压经放大器、滤波，A/D转换将模拟的电压信号转换成数字信号输入计算机。通过计算电阻抗随时间的变化曲线再计算肱动脉血流介导性扩张，最后在显示器上显示曲线和动脉扩张分析结果。本发明的方法与传统技术相比，仪器简单、成本低，小型化，易于推广，市场前景广阔。

The invention discloses an electrical impedance detection device and method for arterial endothelial function, belonging to the technical field of medical instruments. The device of the invention comprises upper forearm electrodes, lower forearm electrodes, a high-frequency low-amplitude constant current source generator, an AC voltage detection circuit, a signal amplifier, a filter circuit, an A/D conversion circuit and a computer. The AC voltage detection circuit detects voltage changes, and the AC voltage is amplifier and filtered, and the A/D conversion converts the analog voltage signal into a digital signal for input to the computer. By calculating the change curve of electrical impedance over time, the blood flow-mediated expansion of the brachial artery is calculated, and finally the curve and the analysis result of arterial expansion are displayed on the monitor. Compared with the traditional technology, the method of the invention has simple instruments, low cost, miniaturization, easy popularization and broad market prospect.

Description

Translated fromChinese

动脉内皮功能的电阻抗检测装置及方法Electrical impedance detection device and method for arterial endothelial function

技术领域technical field

本发明属于一种医疗检测方法和仪器，涉及一种心血管疾病的无创伤早期诊断方法，特别涉及一种血管内皮功能的无创伤检测方法和仪器。The invention belongs to a medical detection method and an instrument, and relates to a non-invasive early diagnosis method for cardiovascular diseases, in particular to a non-invasive detection method and an instrument for vascular endothelial function.

背景技术Background technique

近年来，因心脏病和脑中风发病、致残、复发和死亡的人数急剧增多，每年直接治疗费用也呈急剧增加趋势，给患者家庭和社会造成沉重负担。大量研究表明，动脉粥样硬化是心脑血管疾病发生和发展的重要原因之一。动脉内皮作为血液流动和血管壁之间的功能性屏障，不仅维持血管结构的完整，还在调节血管细胞生长、调节抗凝及纤溶系统、介导炎症与免疫、调节白细胞与血小板在血管内皮黏附、调节脂质氧化、调节血管通透性等方面扮演十分重要的角色。动脉内皮功能受损或功能障碍是动脉粥样硬化早期的主要表现。早期逆转内皮功能是近年来心血管疾病防治的一个新方向。因此，正确评价动脉内皮功能，将为早期诊断和防治高血压、冠心病、糖尿病等常见病及其相应的靶器官病变提供有效的检测手段。In recent years, the incidence, disability, recurrence and death of heart disease and cerebral apoplexy have increased sharply, and the annual direct treatment costs have also shown a sharp increase, which has caused a heavy burden on patients' families and society. A large number of studies have shown that atherosclerosis is one of the important reasons for the occurrence and development of cardiovascular and cerebrovascular diseases. Arterial endothelium, as a functional barrier between blood flow and vascular wall, not only maintains the integrity of vascular structure, but also regulates the growth of vascular cells, regulates anticoagulant and fibrinolytic systems, mediates inflammation and immunity, and regulates the formation of white blood cells and platelets in the vascular endothelium. Adhesion, regulation of lipid oxidation, regulation of vascular permeability and other aspects play a very important role. Damage or dysfunction of arterial endothelium is the main manifestation of early atherosclerosis. Early reversal of endothelial function is a new direction in the prevention and treatment of cardiovascular diseases in recent years. Therefore, the correct evaluation of arterial endothelial function will provide an effective detection method for early diagnosis and prevention of common diseases such as hypertension, coronary heart disease, diabetes and the corresponding target organ lesions.

肱动脉不仅是测量血压的部位，也是检测全身动脉功能的一个重要“窗口”。肱动脉血流介导性扩张(flow-mediated dilation，FMD)反映了动脉内皮在血流突然增加时的舒张能力。临床上，一般使用高分辨率的超声多普勒技术无创伤检测FMD引起的动脉管径扩张率，定义为The brachial artery is not only a site for measuring blood pressure, but also an important "window" for detecting the function of arteries throughout the body. Flow-mediated dilation (FMD) of the brachial artery reflects the ability of the arterial endothelium to relax when blood flow suddenly increases. Clinically, high-resolution ultrasound Doppler technology is generally used to non-invasively detect the expansion rate of arterial diameter caused by FMD, which is defined as

$FMD FMD = = \frac{{D D.}_{peak peak} - - {D D.}_{baseline baseline}}{{D D.}_{baseline baseline}} \times \times 100100 % %,,$

这里D_baseline表示静息状态下动脉搏动管径的平均值，D_peak表示动脉扩张后搏动管径平均值的最大峰值，来评价动脉的内皮功能。超声测量肱动脉内皮功能虽然被美国心脏学会认为是一项“有前途的技术”，但用该方法检测动脉管径的变化需要对动脉管径进行精确定位，不仅操作程序烦琐、耗时，而且相关的仪器设备价格昂贵，不便于推广到社区或者家庭简单使用。Here, D_baseline represents the average value of arterial pulsation diameter at rest, and D_peak represents the maximum peak value of the average value of pulsation diameter after artery dilation, to evaluate the endothelial function of the artery. Ultrasonic measurement of brachial artery endothelial function is considered a "promising technology" by the American Heart Association, but using this method to detect changes in arterial diameter requires precise positioning of the arterial diameter, which is not only cumbersome and time-consuming, but also Related instruments and equipment are expensive, and it is not easy to promote them to communities or families for simple use.

发明内容Contents of the invention

用气袖无创伤阻断肱动脉血流一定时间后释放，将引起下游前臂动脉的血流动力学环境特别是作用于动脉内皮的壁面剪应力发生改变，改变的剪应力将诱发前臂动脉内皮释放血管舒张因子NO，进一步引起前臂动脉的管径发生改变，这一过程称为肱动脉血流介导性扩张(FMD)。在该过程中动脉血流量发生改变，动脉血液的电导特性发生相应变化，引起前臂动脉的总电阻抗发生改变。通过检测静息和FMD实施过程电阻抗的变化情况可以反映FMD引起的动脉管径变化，从而达到间接评估动脉内皮功能的目的。Using the air cuff to block the blood flow of the brachial artery non-invasively and then release it for a certain period of time will cause changes in the hemodynamic environment of the downstream forearm artery, especially the wall shear stress acting on the arterial endothelium, and the changed shear stress will induce the release of the forearm artery endothelium The vasodilation factor NO further causes the diameter of the forearm artery to change, and this process is called brachial artery flow-mediated dilation (FMD). During this process, the arterial blood flow changes, and the electrical conductance characteristics of the arterial blood change accordingly, causing the total electrical impedance of the forearm artery to change. By detecting the change of electrical impedance at rest and during the implementation of FMD, the change of arterial diameter caused by FMD can be reflected, so as to achieve the purpose of indirect evaluation of arterial endothelial function.

前臂可看成一个电导体，其电阻抗由前臂内所有动脉、静脉、皮肤、肌肉、骨骼和其他组织的电导特性共同决定。由于FMD过程中只有动脉血流的电导特性才发生明显变化，因此所测量的前臂电阻抗的改变就是前臂内动脉段电阻抗的改变。将前臂内的动脉等效于一个纵向长度L不变的圆筒形腔室，其半径r则在动脉正常搏动和FMD过程中发生改变。当在这样的一个圆筒形的弹性腔室两端加上一个交流电时，其等效电路可认为是一个电阻R_a与一个电容C_a的并联。这里，R_a是当电流沿着这个圆筒形腔室的轴向通过时的电阻，表达为The forearm can be thought of as an electrical conductor whose electrical impedance is determined by the conductance properties of all arteries, veins, skin, muscles, bones, and other tissues within the forearm. Since only the conductance characteristic of the arterial blood flow changes significantly during the FMD process, the measured change in the electrical impedance of the forearm is the change in the electrical impedance of the forearm arterial segment. The artery in the forearm is equivalent to a cylindrical chamber with a constant longitudinal length L, and its radius r changes during the normal beating of the artery and the process of FMD. When an alternating current is applied to both ends of such a cylindrical elastic chamber, its equivalent circuit can be considered as a parallel connection of a resistance R_a and a capacitance C_a . Here,_Ra is the resistance when the current passes along the axial direction of this cylindrical chamber, expressed as

${R R}_{a a} = = {ρ ρ}_{a a} \frac{L L}{A A},, - - - - - - ((11))$

式中，ρ_a为圆筒形腔室中血液的电阻率，L为圆筒形腔室的长度，A为圆筒形腔室的截面积，满足A＝πr²，其中r为圆筒形腔室的半径。此外，C_a为圆筒形腔室两端电极之间的等效电容，可表示为In the formula, ρ_a is the resistivity of blood in the cylindrical chamber, L is the length of the cylindrical chamber, and A is the cross-sectional area of the cylindrical chamber, satisfying A=πr² , where r is the cylindrical The radius of the chamber. In addition,_Ca is the equivalent capacitance between the electrodes at both ends of the cylindrical chamber, which can be expressed as

${C C}_{a a} = = Kϵ Kϵ \frac{A A}{L L},, - - - - - - ((22))$

式中，ε为两电极之间介质的介电常数，K为小于1的修正系数。这个电容C_a的容抗为In the formula, ε is the dielectric constant of the medium between the two electrodes, and K is a correction coefficient less than 1. The capacitive reactance of this capacitor C_a is

${Z Z}_{c c} = = \frac{11}{jω jω {C C}_{a a}},, - - - - - - ((33))$

其中，

ω为所通过交流电的圆频率。电阻R_a与电容C_a并联等效电路的总阻抗为in,

ω is the circular frequency of the passing alternating current. The total impedance of the parallel equivalent circuit of resistor R_a and capacitor C_a is

${Z Z}_{a a} = = {((\frac{11}{{R R}_{a a}} + + \frac{11}{{Z Z}_{c c}}))}^{- - 11} = = {R R}_{a a} \frac{11 - - j j {R R}_{a a} {C C}_{a a} ω ω}{11 + + {R R}_{a a}^{22} {C C}_{a a}^{22} {ω ω}^{22}} . . - - - - - - ((44))$

将(1)和(2)代入(4)，可得总阻抗表达式为Substituting (1) and (2) into (4), the total impedance can be expressed as

${Z Z}_{a a} = = {K K}^{' '} {ρ ρ}_{a a} \frac{L L}{A A} = = {K K}^{' '} {ρ ρ}_{a a} \frac{L L}{π π {r r}^{22}},, - - - - - - ((55))$

式中In the formula

${K K}^{' '} = = \frac{11 - - j j {ρ ρ}_{a a} Kϵω Kϵω}{11 + + {ρ ρ}_{a a}^{22} {K K}^{22} {ϵ ϵ}^{22} {ω ω}^{22}},,$

它是一个由血液的电阻率ρ_a与介电常数ε、电容形状以及交流电频率ω决定的常数，与圆筒形腔室截面积A的变化(即半径r的变化)无关。It is a constant determined by the resistivity ρ_a of blood, the dielectric constant ε, the capacitance shape and the AC frequency ω, and has nothing to do with the change of the cross-sectional area A of the cylindrical chamber (that is, the change of the radius r).

根据(5)式，不难求得圆筒形腔室截面半径r的变化量dr与圆筒形腔室的电阻抗Z_a的变化量dZ_a之间的关系为According to formula (5), it is not difficult to obtain the relationship between the variation dr of the cylindrical chamber section radius r and the variation dZ_a of the electrical impedance Z_a of the cylindrical chamber as follows:

$\frac{dr dr}{r r} = = - - \frac{11}{22} \cdot &Center Dot; \frac{d d {Z Z}_{a a}}{{Z Z}_{a a}},, - - - - - - ((66))$

这个公式说明，前臂动脉等效半径的相对变化量等于前臂动脉电阻抗相对变化量的-1/2。This formula shows that the relative variation of the equivalent radius of the forearm artery is equal to -1/2 of the relative variation of the forearm artery electrical impedance.

假定除动脉外的组织和器官总阻抗为常量Z_o，则前臂总电阻抗Z为Z_o和Z_a的并联，表示为Assuming that the total impedance of tissues and organs except arteries is a constant Z_o , the total electrical impedance Z of the forearm is the parallel connection of Z_o and Z_a , expressed as

$Z Z = = \frac{{Z Z}_{o o} {Z Z}_{a a}}{{Z Z}_{o o} + + {Z Z}_{a a}},, - - - - - - ((77))$

由(7)式可得From (7) can get

$dZ dZ = = \frac{{Z Z}_{o o}^{22}}{{(({Z Z}_{o o} + + {Z Z}_{a a}))}^{22}} d d {Z Z}_{a a} = = \frac{{Z Z}^{22}}{{Z Z}_{a a}^{22}} d d {Z Z}_{a a},, - - - - - - ((88))$

代(8)式入(6)，得Substituting (8) into (6), we get

$\frac{dr dr}{r r} = = - - \frac{11}{22} \cdot &Center Dot; \frac{d d {Z Z}_{a a}}{{Z Z}_{a a}} = = - - \frac{11}{22} \cdot &Center Dot; \frac{{Z Z}_{a a}}{Z Z} \cdot \cdot \frac{dZ dZ}{Z Z},, - - - - - - ((99))$

进一步由(7)式可知Further from formula (7), we can know

$\frac{dr dr}{r r} = = - - {K K}^{' '' '} \cdot \cdot \frac{dZ dZ}{Z Z},, - - - - - - ((1010))$

式中In the formula

${K K}^{' '' '} = = \frac{11}{22} \cdot &Center Dot; \frac{{Z Z}_{a a}}{Z Z} = = \frac{11}{22} \cdot \cdot \frac{{Z Z}_{o o} + + {Z Z}_{a a}}{{Z Z}_{o o}} . . - - - - - - ((1111))$

对每一个体而言，在FMD实施之前K″是一个具有相对稳定值的参数。在检测FMD过程中，由于动脉舒张，前臂动脉的管径随心跳搏动的同时总体上一开始随时间呈上升趋势，达到峰值后逐步恢复到静息状态的水平。因此根据(10)式，电阻抗Z的变化趋势与管径的变化趋势正好相反，即：一开始随时间呈下降趋势，达到最小值后逐步回复到静息状态的水平。定义阻抗的最大变化率FMD_z，For each individual, K" is a parameter with a relatively stable value before the implementation of FMD. During the detection of FMD, due to arterial dilation, the diameter of the forearm artery pulses with the heartbeat and generally increases over time at the beginning trend, and gradually return to the resting state level after reaching the peak value. Therefore, according to (10) formula, the change trend of the electrical impedance Z is just opposite to the change trend of the pipe diameter, that is, it shows a downward trend with time at the beginning, and after reaching the minimum value Gradually return to the level of the resting state. Define the maximum rate of change of impedance FMD_z ,

${FMD FMD}_{z z} = = | | \frac{{Z Z}_{min min} - - {Z Z}_{baseline baseline}}{{Z Z}_{baseline baseline}} | | \times \times 100100 % %,, - - - - - - ((1212))$

式中，Z_min为前臂动脉管径为D_peak时的前臂电阻抗最小值，Z_baseline为前臂电阻抗基准值。公式(12)可间接了解FMD：In the formula, Z_min is the minimum value of forearm electrical impedance when the forearm artery diameter is D_peak , and Z_baseline is the baseline value of forearm electrical impedance. Formula (12) can indirectly understand FMD:

FMD＝K″FMD_Z， (13)FMD=K″ FMD_Z , (13)

从而达到间接评估动脉内皮功能的目的。So as to achieve the purpose of indirect assessment of arterial endothelial function.

为了检测前臂电阻抗的变化情况，如图1所示，给前臂上电极和前臂下电极加一个一定频率ω的高频低幅的恒流电源，使前臂通过一个强度恒定的交流电流I，这样在前臂长度为L段两端就建立起一定的交流电压U。由交流电的欧姆定律可知，前臂L段的电阻抗Z与电压U及电流I的关系为In order to detect the change of the forearm electrical impedance, as shown in Figure 1, add a constant current power supply with a certain frequency ω of high frequency and low amplitude to the upper electrode of the forearm and the lower electrode of the forearm, so that the forearm passes an AC current I with constant intensity, so that A certain AC voltage U is established at both ends of the forearm length L. According to Ohm's law of alternating current, the relationship between the electrical impedance Z of the forearm segment L and the voltage U and current I is

$Z Z = = \frac{U u}{I I} - - - - - - ((1414))$

由(14)式可见，在前臂通过的电流强度I为恒定值的情况下，前臂阻抗Z将与电压U成正比，因此可通过检测这个交流电压U的变化来求得电阻抗Z的变化。It can be seen from formula (14) that when the current intensity I passing through the forearm is a constant value, the impedance Z of the forearm will be proportional to the voltage U, so the change of the electrical impedance Z can be obtained by detecting the change of the AC voltage U.

本发明的装置包括前臂上电极、前臂下电极、高频低幅恒流源发生器、交流电压检测电路、信号放大器、滤波电路、A/D转换电路和计算机。前臂上电极置于待测手臂的上部，前臂下电极置于待测手臂的下部；高频低幅恒流源发生器、前臂上电极和前臂下电极构成电流回路，交流电压检测电路检测该电流回路中的电压变化。交流电压检测电路检测到的交流电压U经放大器、滤波，A/D转换将模拟的电压信号转换成数字信号输入计算机。The device of the invention comprises upper forearm electrodes, lower forearm electrodes, a high-frequency low-amplitude constant current source generator, an AC voltage detection circuit, a signal amplifier, a filter circuit, an A/D conversion circuit and a computer. The upper forearm electrode is placed on the upper part of the arm to be tested, and the lower forearm electrode is placed on the lower part of the arm to be tested; the high-frequency low-amplitude constant current source generator, the upper forearm electrode and the lower forearm electrode form a current loop, and the AC voltage detection circuit detects the current The voltage change in the circuit. The AC voltage U detected by the AC voltage detection circuit is amplifiered, filtered, and A/D converted to convert the analog voltage signal into a digital signal for input to the computer.

根据公式(14)计算FMD实施过程电阻抗Z随时间的变化曲线：Calculate the change curve of electrical impedance Z over time in the FMD implementation process according to formula (14):

$Z Z = = \frac{U u}{I I} - - - - - - ((1414))$

根据实施FMD前的电阻抗基准值Z_baseline和实施FMD后的电阻抗最小Z_min，代入公式(12)计算FMD_z(％)，最后在显示器上显示曲线图和结果。According to the electrical impedance reference value Z_baseline before implementing FMD and the electrical impedance minimum Z_min after implementing FMD, the FMD z (%) is substituted into formula (12) to calculate FMD_z (%), and finally the graph and results are displayed on the monitor.

${FMD FMD}_{z z} = = | | \frac{{Z Z}_{min min} - - {Z Z}_{baseline baseline}}{{Z Z}_{baseline baseline}} | | \times \times 100100 % % - - - - - - ((1212))$

本发明专利的原理和方法、以及用类似原理和方法制作的仪器也同样适用于股动脉内皮功能的测试。The principles and methods of the patent of the present invention, as well as instruments made with similar principles and methods, are also applicable to the test of femoral artery endothelial function.

本发明提出一种通过无创伤检测肱动脉血流介导性扩张(FMD)过程中前臂电阻抗的变化间接评估动脉内皮功能的方法。与超声检测技术相比，电阻抗检测方法制作的仪器将具备简单易行、价格低廉的特点，很容易小型化推广到社区和家庭使用。The invention proposes a method for indirect evaluation of arterial endothelial function by non-invasively detecting the change of forearm electrical impedance in the process of brachial artery flow-mediated dilatation (FMD). Compared with ultrasonic testing technology, the instrument made by electrical impedance testing method will have the characteristics of simplicity and low price, and it is easy to miniaturize and promote to communities and families.

附图说明Description of drawings

图1是电阻抗法测量FMD结构示意图。Figure 1 is a schematic diagram of the structure of FMD measured by electrical impedance method.

图2是图1中动脉等效圆筒。Figure 2 is the equivalent cylinder of the artery in Figure 1.

图3是本发明的结构框图。Fig. 3 is a structural block diagram of the present invention.

图4是FMD实施过程前臂电阻Z抗随时间t变化的示意图。Fig. 4 is a schematic diagram of the change of forearm impedance Z with time t during the implementation of FMD.

具体实施方式Detailed ways

如图1所示，将电极置于待测前臂的两端；用图3所示的检测电路和计算机系统，采集、存储和分析检测信号。As shown in Figure 1, the electrodes are placed at both ends of the forearm to be tested; the detection circuit and computer system shown in Figure 3 are used to collect, store and analyze detection signals.

本实施例中，铂金丝作为电极，常规血压计附带的袖带作为肱动脉加压装置。In this embodiment, the platinum wire is used as the electrode, and the cuff attached to the conventional sphygmomanometer is used as the brachial artery pressure device.

首先检测并记录人体在静息状态下的前臂阻抗Z_baseline；用类似常规水银血压计自带的气袖给肱动脉加压，阻断肱动脉血流一定时间(一般5分钟左右)后释放，检测并记录阻断、释放过程中前臂动脉总电阻抗随时间的变化曲线，如图4所示；计算曲线的最小值Z_min。最后根据公式(12)计算电阻抗的最大变化率FMD_z。First, detect and record the forearm impedance Z_baseline of the human body in a resting state; pressurize the brachial artery with a gas cuff similar to that of a conventional mercury sphygmomanometer, block the blood flow of the brachial artery for a certain period of time (usually about 5 minutes), and then release it. Detect and record the time-varying curve of the total electrical impedance of the forearm artery during the blocking and releasing process, as shown in Fig. 4; calculate the minimum value Z_min of the curve. Finally, the maximum change rate FMD_z of electrical impedance is calculated according to formula (12).

Claims

1. An electrical impedance detection device of artery endothelial function, including forearm upper electrode, forearm lower electrode, high-frequency low-amplitude constant current source generator, alternating voltage detection circuit, signal amplifier, filter circuit, A/D switching circuit and computer; the device is characterized in that a forearm upper electrode is arranged at the upper part of an arm to be tested, and a forearm lower electrode is arranged at the lower part of the arm to be tested; the high-frequency low-amplitude constant current source generator, the upper forearm electrode and the lower forearm electrode form a current loop, and the alternating voltage detection circuit detects the voltage change in the current loop; the AC voltage U detected by the AC voltage detection circuit is converted into a digital signal by amplifier, filter and A/D conversion, and the digital signal is input into a computer.

2. An electrical impedance detection method using the apparatus of claim 1,

the variation of the electrical impedance Z with time is calculated according to equation (14):

Z = \frac{U}{I} - - - (14)

according to obtaining Z_baselineAnd Z_minSubstituting into equation (12) to calculate FMD_z(%), and finally the graph and the results are shown on the display;

<math> <mrow> <msub> <mi>FMD</mi> <mi>z</mi> </msub> <mo>=</mo> <mo>|</mo> <mfrac> <mrow> <msub> <mi>Z</mi> <mi>min</mi> </msub> <mo>-</mo> <msub> <mi>Z</mi> <mi>baseline</mi> </msub> </mrow> <msub> <mi>Z</mi> <mi>baseline</mi> </msub> </mfrac> <mo>|</mo> <mo>×</mo> <mn>100</mn> <mo>%</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>12</mn> <mo>)</mo> </mrow> </mrow></math>

calculating the minimum Z of the curve_min. Finally, the maximum change rate FMD of the impedance is calculated according to the formula (12)_z。