Impedimed Body Composition Analyzers from FaCT Canada

Single Frequency Bioimpedance for Determining Body Composition

Single frequency bioimpedance analysis (SF-BIA) refers to the determination of body composition by the use of one frequency to measure the impedance of a body. A transformation process is used to convert the "raw impedance data" into a body composition analysis: intracellular (ICF) and extracellular (ECF) fluid, total body water, fat mass, fat free mass, active tissue mass and extracellular mass. The measured impedance of that current is a property of ICF and ECF (called resistance) as well as a property of cellular and ionic components of cell membranes (called reactance). Devices that take both of these measurements into account are referred to as "phase sensitive", and give a more accurate reading than devices that just measure resistance.

Prediction equations: The transformation of raw impedance data into body composition is achieved through the use of linear regression prediction equations or algorithms. Prediction algorithms are created by collecting the ‘raw impedance data" from a study population of people. This same study population has their body composition determined by alternative known standards such as radioisotope dilution or hydrostatic weighing. Linear regression analysis is then conducted on these data and used to create a prediction equation. This prediction equation generates an equivalent body composition analysis to the reference standard when the impedance data of a subject within the population study is entered into the equation.

Many prediction algorithms for single frequency devices exist and these were generated in populations as diverse as pediatric, the critically ill, the elderly, obese and the general population. For greatest accuracy, the subject being tested should closely match the population from which the algorithm was generated. Age, sex and race all affect the physiology of a person and therefore their impedance measurements are also affected. For this reason, a good single frequency unit will provide a range of algorithms so the device can be applied to a diverse population.

50 kHz, the standard in single frequency bioimpedance: For each individual, there is a frequency that will travel through both the extracellular (ECF) and intracellular (ICF) compartments of the body. The particular frequency of an individual will depend on her or his physiology and studies have shown it can be as low as 35 kHz and as high as 110 kHz, with an average of 50 kHz. Therefore, 50kHz is referred to as the "average characteristic frequency" and is used in all SF-BIA devices.

The ImpediMed DF50: a single frequency bioimpedance device for the determination and monitoring of body composition

The ImpediMedTM DF50 device is a phase sensitive, single frequency body composition analyzer that utilizes a 50 kHz alternating current. The DF50 avoids the "one size fits all" approach that other single frequency devices use for body composition analysis by providing the user with 3 peer reviewed, public domain, prediction algorithms for body composition. These algorithms cover the child, general and obese population groups. Furthermore, the DF50 allows the user to track a subject’s body composition over time using the ImpediMed DF50 body composition analysis software. Access to all raw data and full onboard processing of body composition analysis make the DF50 a portable device, ideal for immediate determination of body composition in a mobile setting such as a clinic, wellness center, gym or for personal use. Unlike other portable single frequency devices such as body composition scales, the DF50 supine measurement procedure follows NIH established guidelines to ensure the most accurate, reliable and reproducible reading.

Introduction to Bioimpedance Spectroscopy (BIS)

Bioimpedance spectroscopy (or BIS) is next generation bioimpedance technology. Bioimpedance spectroscopy employs the measurement of impedance at many frequencies ranging from very low frequencies (4 kHz) to higher frequencies (1000 kHz). Most bioimpedance spectroscopes have used a minimum of 256 different impedance measurements at frequencies within this range. A sophisticated mathematical tool is used to model resistance versus reactance data for each frequency, allowing for a highly accurate determination of total body water, extracellular and intracellular fluid levels within that individual, without the use of prediction equations. Fat and fat-free mass are then calculated.

The ImpediMed SFB7: an accurate BIS device for the determination and monitoring of body composition

The Imp SFB7 BIS device uses a frequency range of 4-1000 kHz with a 256 data point analysis which allows for determination of the Complex Impedance plot with considerably more accuracy than competitive devices using fewer frequencies. In addition to the greater precision provided by testing over this range, the SFB7 is a very low noise device. This significant engineering advance translates into highly accurate and precise estimates of fluid status. The SFB7 BIS device is the benchmark of accuracy and precision providing excellent raw impedance data.

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