http://drop-kicker.com/wp-content/uploads/2014/01/kyle-bia.pdf

Bioelectrical impedance analysis--part I: review of principles and methods.

Bioelectrical impedance analysis-part II: utilization in clinical practice.

The autonomic nervous system.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-6143.2005.01175.x

Noninvasive discrimination of rejection in cardiac allograft recipients using gene expression profiling

Percentage of body fat is strongly associated with the risk of several chronic diseases but its accurate measurement is difficult. Bioelectrical impedance analysis (BIA) is a relatively simple, quick and non-invasive technique, to measure body composition. It measures body fat accurately in controlled clinical conditions but its performance in the field is inconsistent. In large epidemiologic studies simpler surrogate techniques such as body mass index (BMI), waist circumference, and waist-hip ratio are frequently used instead of BIA to measure body fatness. We reviewed the rationale, theory, and technique of recently developed systems such as foot (or hand)-to-foot BIA measurement, and the elements that could influence its results in large epidemiologic studies. BIA results are influenced by factors such as the environment, ethnicity, phase of menstrual cycle, and underlying medical conditions. We concluded that BIA measurements validated for specific ethnic groups, populations and conditions can accurately measure body fat in those populations, but not others and suggest that for large epdiemiological studies with diverse populations BIA may not be the appropriate choice for body composition measurement unless specific calibration equations are developed for different groups participating in the study.

/pdf/is-bioelectrical-impedance-accurate-for-use-in-large-rucqtw2o1b.pdf

Is bioelectrical impedance accurate for use in large epidemiological studies

Modern pacemaker technology renders possible the adaptation of pacing rate to hemodynamic requirements. The most ambitious approach aims at restoration of the physiological closed-loop system lay utilizing the information supplied by the autonomic nervous system (ANS) and extracted from myocardial contractile performance. Measurement is accomplished by the impedance method using the stimulation electrode as the measuring electrode. The ventricular inotropic parameter (VIP) has been identified as an ANS dependent parameter. A special detection algorithm, regional effective slope quantity (RQ), with high ANS sensitivity has been developed. Rate adaptation has been achieved by using an individually adjustable inotropic index (II). The concept has been evaluated in a multicenter study using a standardized exercise protocol. The results in patients with AV block demonstrate excellent agreement between spontaneous sinus rhythm and the ANS-controlled stimulation rate during different forms of exercise. Measurement of mean arterial blood pressure (MABP) supports the physiological approach of adapting the pacing rate to various types of hemodynamic challenges.

Intracardiac Impedance to Determine Sympathetic Activity in Rate Responsive Pacing

https://www.kidney-international.org/article/S0085-2538(15)59990-0/pdf

Effect of postural changes on the reliability of volume estimations from bioimpedance spectroscopy data

We have developed a novel model for the simulation of artefacts which are produced by stray capacitance during bioimpedance spectroscopy. We focused on whole body and segmental measurements in the frequency range 5-1000 kHz. The current source was assumed to by asymmetric with respect to ground as is the case for many commercial devices. We considered the following stray pathways: 1, cable capacitance; 2, capacitance between neighbouring electrode leads; 3. capacitance between different body segments and earth; 4, capacitance between signal ground of the device and earth. According to our results the pathways 3 and 4 cause a significant spurious dispersion in the measured impedance spectra at frequencies > 500 kHz. During segmental measurements the spectra have been found to be sensitive to an interchange of the electrode cable pairs. The sensitivity was also observed in vivo and is due to asymmetry of the potential distribution along the segment with respect to earth. In contrast to previously published approaches, our model renders possible the simulation of this effect. However, it is unable to fully explain the deviations of in vivo measured impedance spectra from a single Cole circle. We postulate that the remaining deviations are due to a physiologically caused superposition of two dispersions from two different tissues.

https://iopscience.iop.org/article/10.1088/0967-3334/19/2/012/pdf

A model of artefacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy

OBJECTIVE: Abdominal fat is of major importance in terms of body fat distribution but is poorly reflected in conventional body impedance measurements. We developed a new technique for assessing the abdominal subcutaneous fat layer thickness (SFL) with single-frequency determination of the electrical impedance across the waist (SAI). SUBJECTS AND MEASUREMENTS: The method uses a tetrapolar arrangement of surface electrodes which are placed symmetrically to the umbilicus in a plane perpendicular to the body axis. Twenty-four test subjects (12 male, 12 female) underwent SAI and abdominal magnetic resonance imaging (MRI). The SFL below the sensing electrodes was determined from MRI and correlated with the SAI data at four different frequencies (5, 20, 50 and 204 kHz). RESULTS: A highly significant linear correlation (r2=0.99) between SFL and SAI over a wide range of the abdominal SFL was found. Separate regression models for female and male subjects did not differ significantly, except at 50 kHz. CONCLUSION: SAI represents a good predictor of the SFL and provides an excellent tool for the assessment of central obesity. International Journal of Obesity (2001) 25, 502–511

Assessing abdominal fatness with local bioimpedance analysis: basics and experimental findings.

Background : Diagnosis of acute heart rejection after heart transplantation with the help of epimyocardial electrograms has been reported as a sensitive and practicable method. Long-term follow-up has been limited, however, by variations of signals, which can be avoided by using pacemaker-induced signals. Methods : For stimulation and detection of the ventricular evoked response, a new type of electrode with fractal surface structure was used. Seventeen patients undergoing heart transplantation were included in the study. Amplitudes of the depolarization and repolarization parts of ventricular evoked response signals were analyzed and related to the degree of acute rejection according to histologic findings from endomyocardial biopsy. Results : In cases of focal moderate rejection (grade 2, International Society for Heart and Lung Transplantation grading) and higher degrees of rejection, significant amplitude decreases were found. Conclusions : This sensitive noninvasive method for rejection monitoring with a high level of reliability provides the possibility of reducing the number of endomyocardial biopsies.

Helmut Hutten

Papers

Intracardiac Impedance to Determine Sympathetic Activity in Rate Responsive Pacing

Effect of postural changes on the reliability of volume estimations from bioimpedance spectroscopy data

A model of artefacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy

Assessing abdominal fatness with local bioimpedance analysis: basics and experimental findings.

Paced epimyocardial electrograms for noninvasive rejection monitoring after heart transplantation.