Characteristics of Intracellular and Extracellular Fluid Ratio for the Varying Body Impedances in Fixed Total Body Fluid

A bioelectrical impedance analysis is a proven method to measure body composition in clinical situations. It uses the relation between the body fluid and the impedances in a variety of frequencies. A body model can be simplified as a parallel combination of a capacitor and two resistors which represent a cell membrane, Intracellular Fluid (ICF), and Extracellular Fluid (ECF). Low frequency current passes through ECF and high frequency current also passes through ICF in a body. A Cole-Cole plot is a graphical interpretation of the path of impedances and each axis represents resistance and reactance with variable frequencies. A high value of resistance in a horizontal axis is a resistance value of ECF and a low value of resistance at a high frequency presents ICF. Interpolation technique is needed to find out the exact cross-point between impedance values and the horizontal axis. The two estimated impedance values are used to derive Total Body Water (TBW), ICF, ECF, Fat Free Mass (FFM), and Fat Mass (FM) from various published equations [1]. Minimizing the possible error of fluid volume assessment and accurate prediction of fluid status in a human body is essential for appropriate therapy. Different techniques of fluid status assessment in a human body can be applicable, such as physical examination, orthostatic vital signs, blood volume measurement, acoustic cardiograph, chest radiography, and thoracic ultrasonography [2]. In this study, a bioelectrical impedance spectroscopy device and simple body models were used to collect data such as TBW, ICF, ECF, FM, and FFM. The ratio between ICF and ECF was investigated for the same values of TBW, FM, and FFM by varying impedance values.