1. A LABORATORY ACTIVITY IN BIOELECTRICAL IMPEDANCE ANALYSIS Elliot Mylott (emylott@pdx.edu) Sabrina Hoffman Ralf Widenhorn (ralfw@pdx.edu) Physics Department Portland State University, Portland, OR European Journal of Clinical Nutrition 63, 619-626 (May 2009) OMRON Body Fat Analyzer (healthgoods.com)

2. Bioelectrical Impedance Analysis OMRON Body Fat Analyzer (healthgoods.com) RJL Bioelectric Impedance Analyzer (rjlsystems.com\products)

3. The Body as an RC Circuit (Liedtke, Principles of Bioelectrical Impedance Analysis 1997) Reactive components due to cellular walls Resistive components due to both intra- and extracellular fluid Current flows primarily through Fat Free Mass

4. Series Equivalent Circuit Body impedance frequency dependant Single Frequency BIA uses 50kHz More complex body models approximated with series circuit Single Frequency Series Equivalent Bio-Impedance Analysis BIA Evaluation of Nutrition and Hydration Status Using Vectorgram and BiaGram, (rjlsystems.com)

5. Circuit Analysis Measured Impedance and Phase Leads to Reactance and Resistance Comparison of voltage across a known resistor gives gain and phase

6. Current Impedance Phase Measurement I – NI ELVIS and LabView DAQ must have a high sampling rate.

7. Measurement II – Apparatus Competition

8. Mass Calculation Wikipedia, Electrical resistivity and conductivity In human testing Cylinder model Measure of Fat Free Mass Length Height Density approximately equal to that of water Coefficients and fitting factors empirically derived http://nutrition.uvm.edu/bodycomp/bia/lesson4.html Lukaski and Bolonchuk, Aviation Space and Environmental Medicine 59 1163-1169, 1988)

9. Multi-frequency BIA American Journal of Clinical Nutrition 1996; 64: 388S-96S Students can explore Series and Parallel impedance combinations More accurate models for human electrical characteristics Relationship between frequency and impedance

10. Summary Introductory Physics Level Laboratory Exercise Exploring: Resistance, reactance Parallel and Series Impedance Phasor diagrams and phase shifts Waveform measurement Resistivity, density and mass RC Circuits Electrical Characteristics of the body