Bioimpedance

Kinter, L.B. and Johnson, D.K., Remote monitoring of experimental endpoints in animals using radiotelemetry and bioimpedance technologies, in Proceedings of the International Conference on Humane Endpoints in Animal Experiments for Biomedical Research, Hendriksen, C.F.M. and Morton, D.B., Eds., The Royal Society of Medicine Press, London, 1999, pp. 58-65. 

There was significant improvement in signs of mitochondrial toxicity in 49 patients who switched from stavudine to abacavir compared with 63 patients who continued to take stavudine in a non-randomized study for 12 months (152). Only patients who remained on their assigned treatment were included in the analysis. Lactate concentrations were assessed at baseline, week 24, and week 48, and electrical bioimpedance was performed in 22 cases and 12 controls at baseline and week 48. There were significant falls in serum lactate concentrations at weeks 24 and 48 in cases compared with controls. Patients who switched had a trend towards fat gain, while controls had significant reductions in total body fat and percentage of body fat. 

Complications related to pulmonary artery catheter insertion, maintenance, and removal include damage to vessels and organs during insertion, arrhythmias, infections, and thromboembolic damage. To avoid the complications associated with pulmonary artery catheterization, other less invasive tools were developed to obtain similar information. For example, cardiac output determinations have been made by Doppler, bioimpedance, dye, and ionic dilution techniques, although such measurements would not provide other data that are obtained routinely with pulmonary artery catheters (e.g., left-sided heart-filling pressure). Additionally, advances in... 

Waluga M, Janusz M, et al. Cardiovascular effects of ephedrine, caffeine, and yohimbine measured by thoracic electrical bioimpedance in obese women. Clin Physiol 1998 18 6976. 

Bioimpedance Measurements Sverre Grimnes and 0rjan G. Martinsen.10-1... 

What Is Bioimpedance Conductors and Dielectrics Living Tissue Electrical... 

Variables Measured with Two Electrodes Bioimpedance in Electrosurgery Body Composition Electrical Impedance Tomography Some Additional Applications References.10-28... 

Schwan Plonsey and Barr (2000), which focuses on bioelectricity and Grimnes and Martinsen (2008) on bioimpedance and bio electricity. 

Constant phase elements (CPEs) have been used in bioimpedance models since the late 1920s. A CPE can be modeled by a resistor and capacitor, both having frequency-dependent values, in such a way that the phase angle is frequency independent. A CPE is mathematically simple, but not so simple as to realize with discrete, passive components in the real world. A particular type of CPE is the Warburg element, known from electrochemistry and solid state physics. It is diffusion controlled with a constant phase angle of 45° (Warburg 1899). 

Bioimpedance is measured with an electric current applied to the CC electrodes. If the current waveform is sinusoidal, the signal from the PU electrodes should also be a sine. If it is not, the system is nonhnear and the current amplitude should then be reduced until the PU signal is sinusoidal. Signal-to-noise ratio is also reduced so, a trade-off may be necessary in the choice of the best amplitude. 

For humans, bioimpedance methods use currents, which are not perceptible and of course not harmful. Only AC sinusoidal currents and DC are considered in this section, not pulse excitation. The biological effects of externally applied electromagnetic fields (through the air) are treated elsewhere (Polk and Postow 1996). For practical reasons, perception and hazard levels are usually quoted as current, energy, or charge in the external circuit (Dalziel 1954,1972). The current density field in the tissue is usually unknown. 

The application field of bioimpedance is very wide—from single-cell measurements with micro- and nanoelectrodes to whole-body composition analysis from healthy to ischemic, pathological, and dead tissue. We have selected some typical bioimpedance application examples. 

Volume measurements by impedance were proposed early and became one of the first widespread impedance applications in hospital instrumentation. It is a part of the usual bedside patient monitor present in all intensive-care units impedance adds respiration to the ECG and blood pressure channels. It is embedded in the monitors rather anonymously, uses the ECG electrodes already there, and passes unnoticed as a clinical bioimpedance method by most users. 

Electrosurgery (ES) units are used in all operating rooms throughout the world. HF currents are used for tissue cutting, coagulation, desiccation, and sealing. Several bioimpedance systems are used to increase performance and safety. 

Although not evident from the title, rheoencephalography is a plethysmographic technique based on bioimpedance and with focus on cerebral blood flow (Bodo et al. 2004 Grimnes and Martinsen 2008 Bodo 2010). 

Bernstein DP. 1986. A new stroke volume equation for thoracic electrical bioimpedance Theory and rationale. Crit Care Med 14 (10), 904-909. 

Cornish BH, Jacobs A, Thomas BJ, Ward LC. 1999. Optimising electrode sites for segmental bioimpedance measurements. Physiol Meas 20,241-250. 

De Lorenzo A, Andreoli A, Matthie J, Withers P. 1997. Predicting body cell mass with bioimpedance by using theoretical methods A technology review. / Appl Physiol 82,1542-1558. 

Grimnes S, Martinsen 0G. 2008. Bioimpedance and Bioelectricity Basics. Amsterdam, Elsevier-Academic Press. 

Hettrick DA, Zielinski TM. 2006. Bioimpedance in Cardiovascular Medicine. Encyclopedia of Medical Devices and Instrumentation, 2nd edition. New York, lohn WUey Sons, Inc. pp. 197-216. 

Modeling the dynamics of lung tissue with pulsating blood-flow in pulmonary arteries for bioimpedance simulation... 

Keywords Lung bioimpedance pulmonary arteries vascular system modeling simulation pulse wave velocity arterial tree constrained constructive optimization... 

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