BODY COMPARTMENTS
The different body composition analysis models
Biochemistry
Direct measurement performed on cadavers and serving as a reference for other techniques.
Anatomy
Indirect measurement used in medical imaging.
Physiology
Indirect measurement used in bio-impedance.
Schematic representation: proportions vary with sex, age and body build.
Reminder of the measurement principles: multi-frequency and spectroscopy
The resistance of tissues to the passage of current varies with the type of tissue and the frequency used: this is what makes it possible to determine body compartments.
- At high frequencies (50 to 500 kHz), the current passes through cell membranes: total body water is measured.
- At low frequencies (1 to 7 kHz), the current does not cross the cell membrane: extracellular water is measured.
Multi-frequency
Multi-frequency bioimpedance uses a few fixed frequencies, generally between 5 and 250 kHz. Below 5 kHz, the current has difficulty crossing the skin barrier, and above 200 kHz repeatability decreases.
«International Journal of Clinical Nutrition, 2014, Vol. 2, No. 1, 1-10 Available online at http://pubs.sciepub.com/ijcn/2/1/1 © Science and EducationPublishing DOI:10.12691/ijcn-2-1-1 : Poor reproducibility has been observed at frequencies below 5 kHz and above 200 kHz, especially for reactanceat low frequencies ( Hannan WJ, Cowen SJ, Fearson KCH, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bioimpedanceanalysis for the assessment of extracellular and total body water in surgical patients. Clin Sci 1994; 86: 479-85. )»
Spectroscopy (BIS)
Spectroscopy continuously sweeps the entire spectrum, from 1 to 1000 kHz, across 54 points. Rather than relying on a single frequency, it models the overall electrical response of the tissues (Cole-Cole plot). From this it derives the resistance at zero frequency (R0, related to extracellular water) and at infinite frequency (R∞, related to total body water). The extreme frequencies, which are poorly reproducible on their own, thus contribute to an overall fit instead of being used in isolation.
Result: a more physiological estimate of the body water compartments, and real-time quality control of every measurement.
Our devices use spectroscopy: they continuously sweep the spectrum from 1 to 1000 kHz (54 points) for a complete and reliable analysis of body compartments.
Physiological Models used in Bio-impedance
The models that allow the body to be broken down into more or less detailed compartments are described below.
The addition of these compartments in each model represents the total weight of the measured individual.
Models with 2 to 6 compartments
- FFM Fat-free mass
- FM Fat mass
- SLM Soft lean mass
- BMC Bone mineral content
- DFFM Dry fat-free mass
- TBW Total body water
- BCM Body cell mass
- ECF Extracellular fluid
- ECS Extracellular solids
- ICW Intracellular water
- ECW Extracellular water
- MP Metabolic protein mass
- SP Extracellular (structural) proteins
- SM-R Non-bone minerals
Schematic representation: proportions vary with sex, age and body build.
Our system delivers results for models from 2 to 6 compartments, allowing the practitioner to choose the model that seems most appropriate for the measured patient and to build their dashboard accordingly.