Cornish B H, Thomas B J, Ward L C
Centre for Medical and Health Physics, Queensland University of Technology, Brisbane, Australia.
Phys Med Biol. 1993 Mar;38(3):337-46. doi: 10.1088/0031-9155/38/3/001.
Bioelectrical impedance analysis (BIA) using a frequency of 50 kHz is an established method of predicting total body water (TBW). However, very little research has been performed to determine whether 50 kHz is the optimum frequency for the prediction of TBW from impedance measurements. This paper analyses a mathematical expression describing the equivalent electrical circuit for biological tissue, and derives a graphical representation of the resistive and reactive components. The nature of the resulting impedance locus was used in the analysis of measured whole-body impedance of 42 rats over a range of frequencies to determine the impedance at the characteristic frequency, Zc, and also the impedance at zero frequency, R0. The standard error associated with the prediction of TBW (determined by isotope dilution) using Zc was 5.9% compared with a standard error of prediction of 10.1% using the established BIA method at 50 kHz on the same data. Predictions of extracellular water (ECW) using the impedance at zero frequency, R0, yielded a standard error of 3.2% compared with standard errors of 4.8% and 4.2% using single frequency BIA measurements at 5 kHz and 1 kHz, respectively. These results demonstrate a significant (P < 0.01) improvement in the prediction of TBW and ECW using multiple frequency bioelectrical impedance analysis (MFBIA).
使用50千赫兹频率的生物电阻抗分析（BIA）是预测总体水（TBW）的既定方法。然而，为确定50千赫兹是否是从阻抗测量预测TBW的最佳频率所开展的研究极少。本文分析了描述生物组织等效电路的数学表达式，并得出了电阻性和电抗性分量的图形表示。所得阻抗轨迹的性质被用于分析42只大鼠在一系列频率范围内的全身阻抗测量值，以确定特征频率Zc处的阻抗以及零频率处的阻抗R0。使用Zc预测TBW（通过同位素稀释法确定）的标准误差为5.9%，而在相同数据上使用既定的50千赫兹BIA方法预测的标准误差为10.1%。使用零频率处的阻抗R0预测细胞外液（ECW）的标准误差为3.2%，而分别使用5千赫兹和千赫兹的单频率BIA测量预测时标准误差分别为4.8%和4.2%。这些结果表明，使用多频率生物电阻抗分析（MFBIA）预测TBW和ECW有显著（P < 0.01）改善。
