心阻抗图形成机制的初步探讨

Initiatory Investigation on Formation Mechanism of Impedance Cardiography

目的探讨心阻抗图测量中血管阻抗变化转换为胸部体表电压变化的机制。方法基于胸部内的电场分布,定性分析血管阻抗变化转换为胸部体表电压变化的过程。用模型实验研究转换的规律,将装满稀盐水溶液的塑料圆桶模拟胸部圆柱形容积导体,10~50V的交流电压模拟血管阻抗变化在血管两端产生的电压变化(ΔU_b),同时通过测量圆桶侧壁两检测电极之间的输出电压变化(ΔU_(bs)),研究ΔU_(bs)与相关参数的关系。结果胸部体表两检测电极之间的电势差变化正是通过转换得到的ΔU_(bs)。胸部体表测量的ΔU_(bs)与血管阻抗变化在血管两端产生的电压变化ΔU_b、胸部体表两检测电极之间的距离(L)均呈现正比例关系。结论本文的研究结果可为血管阻抗变化转换为胸部体表电压变化的机制提供依据。

Objective To investigate the mechanism of transforming the impedance change of blood vessel to the voltage change on chest surface in the measurement of impedance cardiography(ICG).Methods The process of transforming the impedance change of blood vessel to the voltage change on chest surface was qualitatively analyzed on the basis of the electrical field distribution within thorax.The transformational law was studied by means of the model experiment.The plastic barrel filling with dilute NaCl solution was used to simulate the cylindrical volume conductor of thorax,and the alternating voltage in 10-50 V ranges was used to simulate the voltage change(ΔU b),which was caused at two ends of the blood vessel by the impedance change of blood vessel.The relations between output voltage change(ΔU bs)and relative parameters were investigated by measuring theΔU bs between two detection electrodes on the side wall of the drum.Results The electrical potential difference between two detection electrodes on chest surface was just theΔU bs obtained by transformation.In the measurement of ICG,theΔU bs measured on chest surface was directly proportional to theΔU b caused at two ends of blood vessel by the impedance change of blood vessel,and to the distance between two detective electrodes on chest surface.Conclusion The investigated results in this article can provide the foundation for the mechanism of transforming the impedance change of blood vessel to the voltage change on chest surface.