外文文献翻译-压电传感器测定动脉脉搏波速度.doc

Piezoelectric sensor determination of arterial pulse wave velocityArterial pulse wave velocity (APWV) is a measure of the elasticity (or stiffness) of peripheral arterial blood vessels. The pulse referred to here will be the pressure pulse as opposed to the flow pulse measured by ultrasound Doppler.The pressure pulse velocity varies over the range from about 12 m s1 to15 m s1 in stiff peripheral arteries, whereas in normal arteries it has a velocity in the range of 7 to 9 m s1.The aim of this project was the development of a fast and easy to use system for the determination of peripheral arterial pulse wave velocity. The principle of the PWV measurement is based on simultaneous measurement of two pulse waves at two different positions, such as the radial artery at the wrist and the brachial artery just above the elbow. By determining the pulse transit time between these points and the distance measured between the two locations, pulse wave velocity may then be calculated. The pressure pulse detection is done by using two piezoelectric sensors which generate a measurable voltage at the output contacts if they are mechanically deformed. The deformation produced voltage is first amplified and filtered and then digitalized with a data acquisition card. The analysis of the data obtained from the sensors includes a filtering process, the calculation of the PWV with three different methods foot-to-foot, cross-correlation and peak-to-peakand the determination of the arterial pulse rate. Extensive measurements with human test subjects were carried out to optimize the techniques of data acquisition and analysis. For example, it was found that the best procedure was to hold the sensors in place using elastic straps alone. The data analysis was upgraded with an additional software module, which deletes, in effect, outriders or invalid measurements. With the optimized system, a series involving eight test subjects ranging in age from 22 to 32 years was completed (all normotensive). The arterial pulse wave velocities determined covered a range from 6 m s1to 12 m s1, with an average standard deviation of less than 2.5 m s1for individual results. These are slightly higher,but close to published APWV data. The results showed that reproducible results can be obtained with the existing PWV acquirement and analysis system.The measurement of arterial pulse wave velocity (APWV) is one of the methods used to measure physiological changes in peripheral vascular disease. Others include pressure pulse contour, arterial elasticity, pulsatile flow, complex vascular impedance and cardiac work.There have been many investigations over the past 30 years or so to relate changes in age and progress of arterial disease, to vessel pathology and distensibility based on the propagation characteristics of the arterial pulse (Malindzak and Meredith 1970, McCormack 1981, Persson et al 2001, Ramsey 1995, Wilkinson 1998). They have only been partially successful from a clinical point of view, mainly due to the difficulty in controlling the effects of patient parameters (autonomic system, patient movement, etc).Early on, the methods of determining APWV involved direct invasive measurement of the pulse pressure at two points along an arterial segment and measuring the time taken for the pulse to travel the length of the segment. Such investigations had to be limited to animals usually dogs. The sensor technique used in this work involves the piezoelectric effect in polyvinyllidene fluoride (PVDF), which produces an output voltage in response to mechanical pressure on the material. Three methods of APWV determination are used: foot-to-foot APWV; peak-to-peak APWV and cross-correlation APWV. The FFAPWV and CCAPWV methods are less sensitive to pressure wave reflections at bifurcations, etc in the arterial tree, than the PPAPWV method. Mean values and standard deviations were computed for all three methods and compared.Foot-to-foot APWV (FFAPWV). This is based on the velocity of the foot, or leading edge, of the pressure pulse wave. The arrival times of the foot of the pulse wave at two positions along the artery are recorded. If t is the difference in arrival times and s the distance between the two recording positions (proximal and distal), the FFAPWV is simplyFFAPWV = s/t.Peak-to-peak APWV (PPAPWV). This is completely analogous to the FFAPWV except that the points of observation are the two (proximal and distal) peaks of the pulse wave andPPAPWV = s/t.Apparent pulse wave velocity (AAPWV). The pressure wave may be represented as aFourier series,P(t) = P0 +Pn sin(nt + n) Where P0 is the mean fluid pressure, n is the harmonic number, Pn is the amplitude of the nth harmonic and n is the phase angle of the nth harmonic.The spatial rate of change of the phase for one harmonic based on two simultaneous pressure measurements separated by a distance _s along an artery, is related to the apparent arterial pulse wave velocity (AAPWV) by the following equation,AAPWVn = (s)n(f )(360o)/(x1 x2)Where AAPWV n is the apparent pulse wave velocity for the nth harmonic, f is the heart rate,x1 is the phase angle for the proximal harmonic n and x2 is the phase angle for the distal harmonic n.Cross-correlation PWV. If the arterial pulse at the proximal measurement position is represented by the pressure time series P(x1, t) and that at the distal position by P(x2, t) andthe cross-correlation coefficient is x1,x2( ), then will have a maximum value at some time lag.The correlation function can be expressed asx1,x2( ) = (1/T )P(x1, t)P(x2, t) dt.The value of at which maximum correlation occurs represents the transit time (_t) of the pressure wave from position x1 to position x2 along the arterial segment. From the separation distance and transit time data the correlation arterial pulse wave velocity isCCAPWV = (x2 x1)/ t.In this work normal, young test subjects were used, and it has the primary objectives of optimizing the measurement procedures and establishing the statistical spread and mean values of the observed PWVs for a specific peripheral arterial segment. Based on this, it is planned to use the system in clinical trials involving patients with peripheral arterial disease (due to diabetes, hypertension, etc), pre-, during and post treatment (pharmaceutical or surgical).Analogue and digital circuitryAnalogue charge amplifier. Piezoelectric materials convert mechanical stress or strain into proportionate electrical energy, by producing a charge when subjected to mechanical stress. The charge is converted to a voltage by an operational amplifier connected as a current integrator, called a charge amplifier. The signal output of the amplifier is approximately 30 mV. It is augmented by signal amplification.Analogue signal amplification . This is done by use of an inverting amplifier. Because a dc signal appears at the output of the charge amplifier, dc offset removal is essential and is implemented in the inverting summing The next phase of the analogue circuitry is a low pass filter to remove the 50 Hz noise interference.Digital controlled data acquisition and analysis. A data acquisition board (DAQ) is required when the transducer signals need interfacing with a PC. The board contains 12 bit plus sign and a successive approximation and self-calibrating analogue-to-digital (ADC) converter. The ADC incurs a systematic error known as the quantization error. It is due to limited resolution and with the analogue input limit set at 5 to +5 V, the quantization error of the A/D converter used here was calculated to be 0.122 mV.The data acquisition and analysis was done using Lab Viewa powerful instrumentation and analysis programming language for PCs.Digital data acquisition program. The data acquisition circuit performs all the necessary operations for the data acquisition with Lab View. The functions of the circuit initialize the data acquisition and read the data from the acquisition card. These data are stored for later use in the data analysis part of the program.Lab View programs are called virtual instruments (VIs) because of their appearance and operations are analogous to measuring instruments. A VI that is called within another VI is called a sub-VI and is analogous to a subroutine in text-based languages.The data acquisition, analysis and presentation are comprised of three main procedures:(1) Data acquisition card to interface the hardware to the PC.(2) Data acquisition program to acquire and store data in a spreadsheet file.(3) Data analysis to carry out digital signal processing, calculate PWV and present results.PWV Calculation 1. PWV calculation using peak detection. To calculate PWV using peaks, the location of the peaks must first be determined, so that the transit time of the wave between the peaks can be determined. It was found that the best method of peak detection is the derivative of the curve method. If the first derivative of a curve is zero, then an extreme value can existeithera peak or a turning point. It is necessary to take the second derivative at this pointif this is also zero, then an extreme value exists. The second VI used to determine the PWV is PWVcalc, using the time separation between the located peaks.2. PWV with pressure wave foot detection. The VI named PWV Foot determines the leading edge (foot) of the pressure wave at the upstream and downstream locations. The VI named PWVcalc is again used to compute the PWV from the time separation between the two leading edges (foot-to-foot APWV or FFAPWV).3. PWV with cross-correlation. The PWV determination with cross-correlation is done with the VI named CalcPWV. The VI is in two parts: a part for the initialization function and a part for the calculation of the CCAPWV.In all cases PWV values are assembled in an array and the mean value, standard deviation and variance are calculated. Sensor positioningSensor placement is critical to obtaining consistent measurements. A screw mechanism was first used to apply the sensors to the skin. But readings were very variable and so this technique was replaced by that in which the sensors are fixed to the skin by elastic strips. This led to better results.Arm position is another critical feature of measurement. Two positions, normal and dependent, were analyzed in detail, using one test subject. In the normal position, the subject sits with the arm resting on a table. All test subject measurements were made in this position. In the dependent position, the subject sits with the arm hanging straight down.The PWV values were smaller in this position and the variability was much greater, so this technique was discarded.A correction module, Delete Incorrect, was used to delete PWV values resulting from aberrant signals, caused commonly by arm movement during the measurement. These unrealistic values were deleted before the PWV values were passed to the analysis VI. 压电传感器测定动脉脉搏波速度动脉脉搏波速度(APWV)是一个测量的弹性(或刚度)的外周动脉血管。这里指的脉冲将压力脉冲,而不是流脉冲多普勒超声测量。压力脉冲速度变化范围从12ms1到15ms1,而在正常动脉有速度范围,在7到9 ms1。这个项目的目标是开发一种快速和易于使用的系统测定外周动脉脉搏波速度。测量仪的原理是基于同时测量两个脉冲波在两个不同的位置,比如桡动脉在手腕和上臂肱动脉略高于肘部。通过测定脉冲过境时间这些点之间和距离测量这两个地点,脉搏波速度可能会被计算。压力脉冲检测是通过使用两个压电传感器产生一个可测量的电压输出联系人如果他们是机械变形。变形产生电压是第一放大和过滤,然后用数据采集卡数字化。分析中获得的数据传感器包括一个过滤过程中,计算有三种不同的方法foot-to-foot APWV; peak-to-peak APWV 和 cross-correlation APWV。与人类测试受试者广泛进行测量，以优化数据采集和分析的技术。例如，这是发现，最好的方法是采用弹性的地方按住传感器独自带。数据分析进行了升级与额外的软件模块，它删除，实际上，企业联合或无效的测量结果。与优化的系统，一系列涉及八个测试受试者年龄范围2232岁完成（所有血压正常）。动脉脉搏波确定的速度覆盖范围为6毫秒，1要12 MS-1，与小于2.5毫秒，1对于各个结果的平均标准偏差。这些都是略高，但接近出版APWV数据。结果表明，可重复的结果可以与现有的PWV采集和分析系统来获得。动脉脉搏波速度（ APWV ）的测量是用于其中一种方法测量生理变化的周围血管疾病。其他包括压力脉冲轮廓，动脉弹性，脉动流，复杂的血管阻抗和心脏的工作。已经有许多研究在过去的30年左右的时间与变化年龄和动脉疾病的进展，血管病变和扩张的基础上，动脉搏动（ Malindzak和Meredith 1970年，麦考马克的传播特性1981年，佩尔森等人2001年，拉姆齐1995，1998威尔金森） 。他们只取得了部分成功从临床的观点来看，主要是由于在控制效果的难度的患者参数（自主神经系统，患者的运动，等等）。在早期，确定APWV的方法所涉及的直接侵入式测量在两个点处沿动脉段和测量所采取的时间的脉冲压力旅行的片段的长度的脉冲。这种调查必须限于动物，通常狗。 Malindzak和Meredith （ 1970）进行了动脉的比较研究对麻醉犬通过记录管腔内压力测量脉搏波传导速度两个站点（近端和远端）沿腹主动脉轴。非侵入性的方法都包括血流多普勒（McCormack1981）和组织多普勒（ Persson的等人，2001 ），使用人类测试受试者的传感器。比较研究简称以上是必需的，因为脉冲速度测量换货投到签署，如果我着地修改，并不同于真实脉冲速度（ TAPWV ）由于流体的粘度，存在反射组件（从分叉，狭窄及周围血管床），并因改变动脉壁的弹性组合物。所有这些导致在改变脉动波的特性，这样，所测量的是一个明显的脉搏波传导速度（ AAPWV ） 。真正的PWV是动脉压脉冲的速度在哪个压力波会在无限均质管（传播的长度比大得多波长） 。为了可靠地预测动脉壁的弹性参数（刚性），这是基金梅子人重视动脉系统的机制的理解，依赖于得到真正的动脉脉搏波传导速度的精确测量。建模的外周动脉段作为薄壁各向同性的，不可压缩的管包含氮化铟镓不可压缩的，非粘性的流体，则PWV由Moens的- Kortweg相关的壁弹性方程（ Moens的1878 ） ，C0 = （ Eh/2R ）（1）其中h是壁厚， R是管腔半径，E是壁的弹性模量，是的流体（血液）的密度。传感器技术用于这项工作涉及到压电效应在聚偏二氟乙烯(PVDF),它产生一个输出电压响应机械压力对材料。三种测定动脉脉搏波速度的方法是: foot-to-foot APWV; peak-to-peak APWV and cross-correlation APWV。FFAPWV和CCAPWV方法不敏感,压力波反射在分支等在动脉树,比如PPAPWV方法。平均值和标准偏差是这三种方法分别要计算并比较的。 Foot-to-footAPWV (FFAPWV)。 这是基于压力脉冲波速度的“脚”,或前缘。脚的到达时间的脉冲波在两个位置沿动脉被记录。t是到达时间之差和s是两个记录位置(近端和远端)之间的距离,FFAPWV是 FFAPWV =s /t。 Peak-to-peakAPWV (PPAPWV)。 这是完全类似于FFAPWV，只是点的观测是脉冲波的两个(近端和远端)的山峰 PPAPWV =s /t。Apparent pulse wave velocity (AAPWV)。压力波可以表示为一个傅里叶级数, P (t) = P0 +Pn (nt +n)P0是流体压力,n是谐波数,Pn是第n次谐波的振幅和相位角的n是第n次谐波。空间变化速度的阶段的一个谐波是沿着动脉基于两个同时压力测量距离s,与明显的动脉脉搏波速度(AAPWV)由以下方程表示, AAPWVn = (s) n(f)(360 o)/(x1x2) 在AAPWVn是明显的脉搏波速度的第n次谐波,f是心率、x1是相角为近端谐波n和x2是相角为远端谐波n。Cross-correlation PWV.。如果动脉脉冲在近端测量位置代表的压力时间序列P(x1,t)、远端位置P(x2,t)和互关联系数的x1,x2(),然后有一个最大值将在某个时间滞后。相关函数可以表示为 x1,x2()=(1 / T) P(x1, )P(x2, )dt。 的价值的最大相关性发生代表时间差(t)的压力波从位置x1,x2位置沿动脉段。从分离距离和时间数据相关动脉脉搏波速度 CCAPWV =(x2x1)/t。 在这个工作正常,年轻的测试对象被使用,而且它的主要目标优化测量程序和建立统计传播和观测到的PWVs平均值为一个特定的外周动脉段。在此基础上,它是计划利用系统在临床试验中涉及外周动脉疾病患者(由于糖尿病、高血压等)、前、中、后的治疗(药物或手术)。模拟和数字电路模拟电荷放大器。压电材料机械应力或应变转换成适当的电能,通过产生一个电荷当受到机械应力。电荷转换成电压通过一个运算放大器连接作为当前积分器,称为电荷放大器。信号输出的放