Design and implementation of a hand-to-hand multifrequency bioimpedance measurement scheme for Total Body Water estimation

TLDR: The design and implementation of a hand-to-hand bioimpedance spectrometer for TBW estimation which can measure impedances within the range of5.3 Ω to 5.3 kΩ in the β dispersion region of tissue between 500 Hz and 1 MHz is presented.

Abstract: Human body has an intricate regulatory mechanism to maintain the Total Body Water (TBW) content and thereby sustain normal hydration levels. However, chronic fluid variations can occur and are often associated with pathological conditions like renal insufficiency and/or medications. Hence, a sensitive and precise estimation of TBW is of much clinical significance. Recent years have seen the emergence of Bioimpedance Spectroscopy (BIS) as a potential tool for TBW estimation with a unique capacity to differentiate between the extracellular and intracellular water content. The design and implementation of a hand-to-hand bioimpedance spectrometer for TBW estimation which can measure impedances within the range of 5.3 Ω to 5.3 kΩ in the β dispersion region of tissue between 500 Hz and 1 MHz is presented in this paper. A three reference calibration algorithm based on quadratic Lagrange interpolation is employed in order to mathematically correct the systematic errors in the measurements. The Cole parameters are extracted from the calibrated spectroscopy measurements by applying a Non-Linear Least Square (NLLS) iterative fitting on the resistance spectrum and further used to determine the extracellular, intracellular and total body water content. Measurements are done on 18 subjects (9 males and 9 females, age 23.3 ± 2.5 years, mean ± SD) at 17 different frequencies within the range of 3 kHz to 1 MHz. TBW estimated using the implemented BIS device prototype is validated against an FDA approved segmental body composition monitor from TANITA. The estimates show a strong positive correlation with Pearson's r of 0.83. The Bland-Altman analysis done on two systems indicate a similarity in TBW estimations with a bias of only 0.17 L while the 95% limits of agreement lie between −6.47 L and 6.81 L.