PHYSIOLOGICAL MODELS

The BCM – Body Composition Monitor is the only device that identifies overhydration as a third compartment on the basis of a unique body composition model.

The clinically relevant output parameters

Overhydration (OH)
Lean Tissue Mass (LTM)
Adipose Tissue Mass (ATM)

are obtained by using two advanced validated physiological models:

In a state of normal hydration with no excess fluid

lean tissue (mainly muscle) consists of 70% water whilst the remaining mass is protein and mineral.
adipose tissue (the majority of which is lipid) consists of 20% water.
excess fluid (overhydration) is almost 100% extracellular water.

The two compartments ATM and LTM bind a completely different ratio of intracellular and extracellular water (Wang & Pierson 1976, Morse & Soeldner 1963) in

lean tissue intracellular water is predominant
in adipose tissue extracellular water is predominant

A volume model describing electrical conductance in a cell suspension enabling the total body water and extracellular water as well as the intracellular water (ICW) to be calculated.¹
A body composition model calculating the three relevant body compartments overhydration, lean tissue and adipose tissue from ECW and TBW information.²

¹ Moissl, U et al., Body fluid volume determination via body composition spectroscopy in health and disease. Physiol. Meas 2006; 27: 921-933.

² Chamney, P et al., A whole-body model to distinguish excess fluid from the hydration of major body tissues. Am J Clin Nutr 2007; 85: 80-89

Even in healthy subjects the distribution of lean and adipose tissue mass will lead to significant differences in the ratio of extracellular to intracellular water (E/I). Therefore E/I alone does not provide sufficient information about the hydration status. Overhydration as a third body compartment has to be introduced.

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