Evaluation of a new impedancemeter to independently measure extracellular, intracellular and total body water volumes: application to the measurement of hydration.

The objective of this study was to evaluate the accuracy of independent hydric data for the quantification of total body water (V t), extracellular water (V e) and intracellular water (V i), obtained by a multifrequency impedancemeter Z-Métrix(®) (ZM), in standing and lying position, with respect to the Xitron reference. In a second step, the aim was to consider whether it is possible to quantify daily hydration. The average repeatability error of the ZM impedancemeter is less than 0.5 %. For total body water (V t), we note a low R (2) dispersion with an average of 0.9 for men and 0.6 for women. The estimation of extracellular water is equivalent to a maximum error of 3.1 % in standing position for women against 2.97 % for men in the same position. The estimation of the total body water by direct measurement and by summing the volumes of extracellular and intracellular water obtained by the Z-Metrix(®) shows very low dispersions with R (2) = 0.89 and average error from 1.3 % for healthy women in lying position to 3.9 % for healthy women in standing position. Finally, despite the impact of events on the daily measurements, it is viable to track a subject's overall hydration.