IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Oct 1994
Application of pattern recognition and image classification techniques to determine continuous cardiac output from the arterial pressure waveform.
The shape of the arterial pressure waveform is a non-linear function of stroke volume, heart rate and many other cardiovascular parameters. Previous attempts have been made to exploit this relationship and derive cardiac output (CO) from the arterial pressure waveform. These classical "pulse-contour" methods utilized simplifying linear assumptions, as a result they failed to adequately estimate CO over a sufficiently wide range of hemodynamic conditions. ⋯ Computer simulations were used to develop the basic pattern recognition algorithms and compare their performance with that of published classical "pulse-contour" methods. Animal models were subsequently used to demonstrate proof of the concept. For over 200,000 individual heart beats, covering a wide range of hemodynamic conditions, the mean error, in calculated CO compared to ultrasonic flow probe determined CO, was 2.8% with a standard deviation of 9.8%.
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An electronic circuit for analog processing of neural (electroneurogram or ENG) and muscular (electromyogram or EMG) signals in functional electrical stimulation (FES) systems is described in this paper. The basic circuit consists of a low-noise gated preamplifier, band-pass filter, amplifier, and a blanking circuit to minimize stimulation artifacts during electrical stimulation. ⋯ The device was used for nerve recordings in the presence of electrical stimulation of muscles in the same leg. The recordings showed rejection of stimulation and muscle (M-wave) artifacts, while retaining the information of interest.
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IEEE Trans Biomed Eng · Jul 1994
Comparative StudyAction potential classification with dual channel intrafascicular electrodes.
Using recordings of peripheral nerve activity made with carbon fiber intrafascicular electrodes, we compared the performance of three different recording techniques (single channel, differential, and dual channel) and four different unit classification methods (linear discriminant analysis, template matching, a novel time amplitude windowing technique, and neural networks) in terms of errors in waveform classification and artifact rejection. Dual channel recording provided uniformly superior unit separability, neural networks gave the lowest classification error rates, and template matching had the best artifact rejection performance.
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IEEE Trans Biomed Eng · Jun 1994
Silicon-substrate microelectrode arrays for parallel recording of neural activity in peripheral and cranial nerves.
A new process for the fabrication of regeneration microelectrode arrays for peripheral and cranial nerve applications is presented. This type of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafter held fixed with respect to the microelectrodes. The process described is designed for compatibility with industry-standard CMOS or BiCMOS processes (it does not involve high-temperature process steps nor heavily-doped etch-stop layers), and provides a thin membrane for the via holes, surrounded by a thick silicon supporting rim. ⋯ Versions of the devices were implanted in the rat peroneal nerve and in the frog auditory nerve. In both cases, regeneration was verified histologically and it was observed that the regenerated nerves had reorganized into microfascicles containing both myelinated and unmyelinated axons and corresponding to the grid pattern of the via holes. These microelectrode arrays were shown to allow the recording of action potential signals in both the peripheral and cranial nerve setting, from several microelectrodes in parallel.
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IEEE Trans Biomed Eng · May 1994
Selective stimulation of sacral nerve roots for bladder control: a study by computer modeling.
The aim of this study was to investigate theoretically the conditions for the activation of the detrusor muscle without activation of the urethral sphincter and afferent fibers, when stimulating the related sacral roots. Therefore, the sensitivity of excitation and blocking thresholds of nerve fibers within a sacral root to geometric and electrical parameters in tripolar stimulation using a cuff electrode, have been stimulated by a computer model. ⋯ The model predicts that an asymmetrical tripolar cuff can generate unidirectional action potentials in small nerve fibers while blocking the large fibers bidirectionally. This result shows that selective activation of the detrusor may be possible without activation of the urethral sphincter and the afferent fibers.