Total body water (TBW) can be estimated from a person's bioelectrical impedance, height and weight. The impedance index (height in centimeters, squared, divided by the resistance in ohms) is a significant predictor of total body water. This can be used for neonates, children and adults, both male and female.
Procedure:
(1) Bioelectrical impedance analysis (BIA) was performed with a body composition analyzer (model BIA-101, RJL Systems, Detroit) with a right-sided tetrapolar placement of electrodes.
(2) The whole body resistance was recorded 3-5 times and the mean value calculated.
impedance index =
= ((height in centimeters)^2) / (resistance in ohms)
