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.


(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)


total body water in kilograms =

= (0.59 * (impedance index)) + (0.065 * (body weight in kilograms)) + 0.04

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