Algorithm for tissue ischemia estimation based on electrical impedance spectroscopy.

The purpose of this paper is to present an algorithm developed for real-time estimation of skeletal muscle ischemia, based on parameters extracted from in vivo obtained electrical impedance spectra. A custom impedance spectrometer was used to acquire data sets: complex impedance spectra measured at 27 frequencies in the range of 100 Hz-1 MHz, and tissue pH. Twenty-nine in vivo animal studies on rabbit anterior tibialis muscle were performed to gather data on the behavior of tissue impedance during ischemia.

Microstructural properties of bone in rat vertebra after long-term clodronate treatment.

Bisphosphonates (BPs) are known to increase bone mineral density, but it is not known how this increase manifests at low hierarchic levels of the bone structure. The present study aimed to clarify the effects of the long-term use of clodronate on the microstructure and chemical composition of bone. The second lumbar vertebral body (L2) in growing rats, subjected to 32 weeks' treatment with clodronate at either a therapeutic dose of 2 mg/kg, or a high dose of 10 mg/kg, or physiological saline (control group), was studied by scanning electron microscopy for morphology, by backscattered electron image (BSE) for density, and by energy dispersive spectrometry for material analysis.

Supplemental systemic oxygen support using an intestinal intraluminal membrane oxygenator.

An intraluminal membrane oxygenator (IMO) prototype was surgically inserted in the ileum and evaluated as a method of supporting systemic oxygenation in an acutely hypoxemic porcine model. Animals were assigned randomly to the test (n = 12) or the control (n = 8) groups, which underwent identical protocols with the exception of the O2 flow in the IMO device, which was shut off in the control group. In each case, hypoxia was induced by a reduction in the inspired oxygen fraction (FiO2) to 0.

Selection of measurement frequencies for optimal extraction of tissue impedance model parameters.

The results are presented of a study performed to determine the measurement frequencies that provide optimal extraction of tissue impedance model parameters from in vivo measured electrical impedance spectra. Measurement frequency sets that are logarithmic and quasi-linear, and frequency sets that produce angularly equidistant points on the Nyquist loci are used to test the parametric fitting algorithm that calculates R0, R infinity, alpha and tau tissue parameters from complex impedance spectra. Simulated data, calculated in the presence of < or = 5% measurement noise, and in vivo experiments indicate that the quality of the fitted parameters depends upon the selection of measurement frequencies.

Effects of sample geometry and electrode configuration on measured electrical resistivity of skeletal muscle.

Over the past 40 years, researchers from a variety of scientific backgrounds have been using Rush's equations to analyze results of their electrophysiological studies. A lack of understanding of the constraints and the domain in which these equations are valid, often results in situations in which it is challenging to evaluate and compare results obtained by different investigators. In this paper, we reanalyzed the conditions for which Rush's equations were derived, and using mathematical modeling, computer simulation and in vitro measurements, we delineated areas of their appropriate application.