Johannes J. Struijk

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In epidural spinal cord stimulation it is likely that not only dorsal column fibers are activated, but that dorsal root fibers will be involved as well. In this investigation a volume conductor model of the spinal cord was used and dorsal root fibers were modeled by an electrical network including fiber excitation. The effects of varying some geometrical(More)
A model is presented for the calculation of single myelinated fiber action potentials in an unbounded homogeneous medium and in nerve cuff electrodes. The model consists of a fiber model, used to calculate the action currents at the nodes of Ranvier, and a cylindrically symmetrical volume conductor model in which the fiber's nodes are represented as point(More)
The cable model, used to calculate the membrane potential of an unmyelinated nerve fiber due to electrical stimulation, is reexamined under passive steady-state conditions. The validity of two of the assumptions of the cable model are evaluated, namely that the membrane potential be a function of the axial coordinate only and that the extracellular(More)
BACKGROUND Reliable continuous monitoring of fluid responsiveness is an unsolved issue in patients ventilated with low tidal volume. We hypothesised that variations in the pre-ejection period (PEP) defined as the time interval between electrocardiogram (ECG) R-wave and onset of systolic upstroke in arterial blood pressure could reliably predict fluid(More)
An electrical network model of myelinated dorsal column nerve fibers is presented. The effect of electrical stimulation was investigated using both a homogeneous volume conductor and a more realistic model of the spinal cord. An important feature of dorsal column nerve fibers is the presence of myelinated collaterals perpendicular to the rostro-caudal(More)
PURPOSE To investigate intradural geometry, which strongly influences the effects of epidural spinal cord stimulation. METHODS Axial MR images with turbo spin-echo were made of 26 healthy subjects at C-4 through C-6, T-5 and T-6, and T-11 and T-12, at T-11 and T-12 both in the supine and the prone position. Measurements were made of the dorsomedial and(More)
The long QT syndrome (LQTS) is a genetic disorder, typically characterized by a prolonged QT interval in the ECG due to abnormal cardiac repolarization. LQTS may lead to syncopal episodes and sudden cardiac death. Various parameters based on T-wave morphology, as well as the QT interval itself have been shown to be useful discriminators, but no single ECG(More)
New designs of cuff electrodes for the recording of signals from peripheral nerves are typically tested in acute animal experiments before long-term evaluation takes place. A reproducible, cost-effective and fast method is presented for evaluating cuff electrodes with respect to signal amplitude, noise rejection, and, in some cases, selectivity, as an(More)
A nerve stimulation model has been developed, incorporating realistic cross-sectional nerve geometries and conductivities. The potential field in the volume conductor was calculated numerically using the variational method. Nerve fiber excitation was described by the model of McNeal. Cross-sectional geometries of small monofascicular rat common peroneal(More)
OBJECTIVES The aim of this study was to investigate whether the heart rate-corrected QT (QTc) interval on the electrocardiogram (ECG) is associated with the onset of atrial fibrillation (AF). BACKGROUND Patients with hereditary short-QT or long-QT syndromes, representing the very extremes of the QT interval, both seem to have a high prevalence of AF. (More)