Raaijmakers E, Faes T J, Goovaerts H G, Meijer J H, de Vries P M, Heethaar R M
Department of Medical Clinical and Informatics, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
Med Biol Eng Comput. 1998 Sep;36(5):592-7. doi: 10.1007/BF02524429.
In thoracic impedance cardiography (TIC) measurements the neck electrodes are often positioned at the basis of the neck, close to the neck-thorax transition. Theoretically, this neck-thorax transition will cause inhomogeneities in the current density and potential distribution. This was simulated using a 3D finite element method, solely representing the geometrical neck-thorax transition. The specific conductivity was 7 10(-3) (omega cm)-1 and the injected current was 1 mA. As expected, the model generated inhomogeneities in the current distribution at the neck-thorax transition, which reached as far as 5 cm into the neck and 20 cm into the thorax. These results are supported by in vivo measurements performed in 10 young male subjects, in which the position of the neck electrodes was varied. A two-way ANOVA revealed that the stroke volume of the lowest neck position was significantly different from the other positions. Small shifts in the position of the neck electrode resulted in large changes in impedance and stroke volume (127 to 82 ml for the Kubicek equation). To standardise the electrode position, the authors strongly recommend placement of the neck electrodes at least 6 cm above the clavicula.
在胸部阻抗心动图（TIC）测量中，颈部电极通常置于颈部根部，靠近颈胸交界处。从理论上讲，这种颈胸交界处会导致电流密度和电位分布不均匀。使用三维有限元方法对此进行了模拟，该方法仅体现了颈胸交界处的几何形状。电导率为7×10⁻³（Ω·cm）⁻¹，注入电流为1 mA。不出所料，该模型在颈胸交界处产生了电流分布不均匀的情况，这种不均匀延伸至颈部5 cm深处和胸部20 cm深处。在10名年轻男性受试者身上进行的体内测量结果支持了这些结果，测量过程中颈部电极的位置有所变化。双向方差分析显示，颈部最低位置时的心输出量与其他位置有显著差异。颈部电极位置的微小变化会导致阻抗和心输出量的大幅变化（根据 Kubicek 方程，从127 ml变为82 ml）。为了使电极位置标准化，作者强烈建议将颈部电极置于锁骨上方至少6 cm处。
