IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Mar 2012
A monitor-decoupled pharmacodynamic model of propofol in children using state entropy as clinical endpoint.
This paper presents a new monitor-decoupled model of propofol pharmacodynamics (PD) using the state entropy (SE) as the clinical endpoint of interest. In our model, the dynamics of the entropy monitor are separated from the PD response of the patient by explicitly accounting for the model of the entropy monitor in the PD identification process. The monitor model was then excluded from the identified PD model for the patient. ⋯ For the Paedfusor pharmacokinetic (PK) model, population-averaged effect site equilibration rate constant k(e0) was 5.4 and 3.0 for the proposed and traditional PD models ( p < 0.001), respectively. For the Kataria PK model, population-averaged k(e0) was 2.3 and 1.4 (p < 0.01). This significant difference suggests that the effects of the monitor must be considered when searching for the intrinsic PD of a patient that is free from the bias induced by the monitor characteristics.
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IEEE Trans Biomed Eng · Mar 2012
Improving myoelectric pattern recognition robustness to electrode shift by changing interelectrode distance and electrode configuration.
Pattern recognition of myoelectric signals for prosthesis control has been extensively studied in research settings and is close to clinical implementation. These systems are capable of intuitively controlling the next generation of dexterous prosthetic hands. However, pattern recognition systems perform poorly in the presence of electrode shift, defined as movement of surface electrodes with respect to the underlying muscles. ⋯ Additionally, for a constant number of channels, an electrode configuration that included electrodes oriented both longitudinally and perpendicularly with respect to muscle fibers improved robustness in the presence of electrode shift (p < 0.05). We investigated the effect of the number of recording channels with and without electrode shift and found that four to six channels were sufficient for pattern recognition control. Finally, we investigated different feature sets for pattern recognition control using a linear discriminant analysis classifier and found that an autoregressive set significantly (p < 0.01) reduced sensitivity to electrode shift compared to a traditional time-domain feature set.
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IEEE Trans Biomed Eng · Mar 2012
Electrode activation sequencing employing conductivity changes in irreversible electroporation tissue ablation.
Irreversible electroporation (IRE) uses high-voltage pulses applied to tissue, which cause dielectric breakdown of cell membranes resulting in cell death. IRE is a promising technique for ablation of nonresectable tumors because it can be configured to spare critical structures such as blood vessels. ⋯ We propose a novel IRE method introducing electrode switching and pulse sequencing in which tissue conductivity is first increased using preparatory pulses in order to form high-conductivity zones, which then helps provide higher electric field intensity within the targeted tissue as subsequent pulses are applied, and hence, enhances the efficiency and selectivity of the IRE treatment. We demonstrate the potential of this method using computational models on simple geometries.
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IEEE Trans Biomed Eng · Feb 2012
A direct dynamic dose-response model of propofol for individualized anesthesia care.
In an effort to open up new opportunities in individualized anesthesia care, this paper presents a dynamic dose-response model of propofol that relates propofol dose (i.e., infusion rate) directly to a clinical effect. The proposed model consists of a first-order equilibration dynamics plus a nonlinear Hill equation model, each representing the transient distribution of propofol dose from the plasma to the effect site and the steady-state dose-effect relationship. ⋯ The efficacy of the direct dynamic dose-response model over a traditional PKPD model was assessed using a mixed effects modeling analysis of the electroencephalogram (EEG)-based state entropty (SE) response to intravenous propofol administration in 34 pediatric subjects. An improvement in the mean-squared error and r(2) value of individual prediction, as well as the Akaike's information criterion (AIC) was seen with the direct dynamic dose-response model.
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IEEE Trans Biomed Eng · Jan 2012
Fascicle-selectivity of an intraneural stimulation electrode in the rabbit sciatic nerve.
The current literature contains extensive research on peripheral nerve interfaces, including both extraneural and intrafascicular electrodes. Interfascicular electrodes, which are in-between these two with respect to nerve fiber proximity have, however, received little interest. In this proof-of-concept study, an interfascicular electrode was designed to be implanted in the sciatic nerve and activate the tibial and peroneal nerves selectively of each other, and it was tested in acute experiments on nine anaesthetized rabbits. ⋯ Interfascicular electrodes could provide an interesting addition to the bulk of peripheral nerve interfaces available for neural prosthetic devices. Since interfascicular electrodes can be inserted without fully freeing the nerve and have the advantage of not confining the nerve to a limited space, they could, e.g., be an alternative to extraneural electrodes in locations where such surgery is complicated due to blood vessels or fatty tissue. Further studies are, however, necessary to develop biocompatible electrodes and test their stability and safety in chronic experiments.