【作者】 卢宗武；

【导师】 李刚；

【作者基本信息】 天津大学 ， 生物医学工程， 2007， 博士

【摘要】 阻抗谱法血液成分无创检测方法通过在体无创测量血液在不同频率下的电阻抗特性,利用不同成分与血液电特性关系检测其浓度变化,具有很广阔的发展前景。但在电阻抗谱测量时,电极与人体皮肤接触介面、电极类型、测量部位等实验条件和人体皮肤状况、血管分布、血流状况、体温等个体差异因素影响严重,测量精度难以提高。本论文提出了“脉搏波阻抗谱”的概念,可以基本上消除测量条件和被测对象个体差异对人体阻抗测量的影响,建立了基于脉搏波阻抗谱的血液电特性无创检测方法,为最终实现电阻抗法血液成分无创检测打下了基础,具有重大的临床应用价值。论文主要研究内容包括:在阻抗血流图技术原理基础上,根据人体单支血管与周围组织并联模型,提出了脉搏波阻抗谱的概念,理论推导了人体阻抗谱和脉搏波阻抗谱与血液电特性参数的关系,分析了脉搏波阻抗谱消除阻抗测量中个体差异影响的原理。研究了人体阻抗测量的原理和特点,提出了基于正交解调的脉搏阻抗谱测量方法,研究了脉搏波阻抗谱测量系统中各电路模块设计要求和实现方案,构建了实验测量系统并进行了测量精度初步测试,实现了在较宽频率范围内对人体复阻抗谱和脉搏波阻抗谱的高精度测量分析了脉搏波信号的特征和影响脉搏波检测精度的影响因素;以傅立叶变换理论为基础,研究了脉搏波阻抗谱频域提取的方法和脉搏波数据段的截取长度对检测精度的影响;研究了基于小波变换理论的阻抗脉搏波信号中奇异点剔除方法。根据人体解剖学特点,建立了手臂并联电阻抗模型和耳垂串连电阻抗模型,采用有限元方法对模型内电流和电压分布进行了计算。对实验对象进行了测量,得到了实验对象的手臂和耳垂部位的基础阻抗谱和脉搏波阻抗谱。有限元计算和实验结果证明,两个模型能够较好地描述人体手臂和耳垂的电阻抗特性。同时也表明,由于手臂各组织电阻抗的并联,测量段的脉搏波阻抗谱不能完全消除基础阻抗的影响,在此部位进行实现血液电阻抗特性的无创检测是困难的。而耳垂脉搏波阻抗谱几乎完全消除了个体差异的影响,能够实现血液电特性的无创检测。更多还原

【Abstract】 There is a concrete relation between the electrical properties of blood and its components concentration pattern. The method of electrical impedance spectroscopy (EIS) using this relation to non-invasively measure the blood component has a broad prospect in medical research and practice. However,high accuracy of impedance measurement is rather difficult to acquire because of the serious influence of several factors to measurement process. These factors include experimental conditions, such as the skin-electrode interface, electrode type, and measurement position as well as the individual variations such as skin status, blood vessel pattern, blood flow, and body temperature. The concept of Pulse Wave Electrical Impedance Spectroscopy (PWEIS) is presented to reduce or eliminate the above-mentioned influences. And a novel method for non-invasive measurement of blood electrical properties is constructed on PWEIS. The method is of great prospect in non-invasive measurement of blood component and great value in medical applications.The concept of PWEIS is presented based on the model of the paralleled single blood vessel and peripheral tissue used in electrical impedance plethysmography (IPG). The relation between human impedance spectroscopy & PWEIS and blood electrical properties is theoretically deduced to analyze the principle of the influence reduction by PWEIS in impedance measurement.The principle and characteristics of electrical impedance measurement on human body is studied, and a method for measurement of PWEIS based on quadrature demodulation is presented. The experimental measurement system is constructed and tested after analysis of the performance demand for circuit modules needed in the system. High accuracy of the impedance spectroscopy and PWEIS is acquired at a wide frequency range.Characteristics of pulse wave and the adverse factors in pulse wave detection are analyzed, and the calculation method of PWEIS in frequency domain is studied. The optimal length of pulse wave data is investigated using DFT. Outliers in the pulse wave signal is diminished using wavelet method.Parallel electrical impedance model of forearm and serial electrical impedance model of earlobe is built up according to their anatomy and the current and voltage distributions in the models are calculated using finite element method (FEM). Experimental measurement is conducted on several subjects and the impedance spectroscopy and PWEIS is acquired. The results show that the models comprehensively describe the electrical prosperities of the forearm and the earlobe. The individual variations cannot be completely eliminated by the PWEIS of forearm because of its parallel impedance of the tissues in forearm. And Earlobe PWEIS can reduce the individual variation influences to a rather low level and makes non-invasive measurement of blood electrical properties practically possible.更多还原