Influence Of Electrode Placement Research Articles

Influence of Electrode Placement on the Morphology of In Silico 12 Lead Electrocardiograms

Influence of Electrode Placement on the Morphology of In Silico 12 Lead Electrocardiograms

Cylindrical electrodes for neutralization of insulating flowing particles

This paper is aimed at studying charge neutralization of flowing particles using a DC corona discharge. The efficiency of two electrodes configurations, namely cone-grid and coaxial cylinder, was experimentally studied. The influence of electrode placement in the middle or at the end of a lab-scale canalization installation is highlighted. Surface potential distribution and charge measurements showed that both configurations can lead to excellent neutralization rates, of around 99%, depending on electrode voltage and placement. The performances of the cone-grid configuration were found to vary according to the electrode placement. Conversely, the coaxial configuration is more stable and, practically, placement independent. A theoretical calculation of required corona discharge to perfectly neutralize charges is also presented. The obtained formula was experimentally verified showing a good agreement between calculation and measurement. Furthermore, the influence of charged particles on the corona discharge when crossing the coaxial electrode is highlighted through discharge current measurement and electric field calculation using finite element software. The charged particles were found to alter the electric field distribution and discharge current resulting in the electric field increase near the wire and his decrease near the grounded cylinder. Therefore, the charged particles act as a dielectric barrier that can affect the discharge current.

Influence of Electrode Placement on Signal Quality for Ambulatory Pregnancy Monitoring

Noninvasive fetal health monitoring during pregnancy has become increasingly important in order to prevent complications, such as fetal hypoxia and preterm labor. With recent advances in signal processing technology using abdominal electrocardiogram (ECG) recordings, ambulatory fetal monitoring throughout pregnancy is now an important step closer to becoming feasible. The large number of electrodes required in current noise-robust solutions, however, leads to high power consumption and reduced patient comfort. In this paper, requirements for reliable fetal monitoring using a minimal number of electrodes are determined based on simulations and measurement results. To this end, a dipole-based model is proposed to simulate different electrode positions based on standard recordings. Results show a significant influence of bipolar lead orientation on maternal and fetal ECG measurement quality, as well as a significant influence of interelectrode distance for all signals of interest.

Maximum Fractal Dimension of Cerebral Seizure Remains Constant Through the Course of Electroconvulsive Therapy

Electroconvulsive therapy (ECT), in which electrical current is used to induce seizures, is an effective treatment in psychiatry. Different methods of analyzing the electroencephalogram (EEG) changes during ECT have been studied for predicting clinical outcome. Analysis of the fractal dimension (FD) is one such method. Mid-seizure and post-seizure FD has been shown to correlate with antidepressant effect. In this study, we examined whether the highest fractal dimension achieved during each ECT session changed over the course of 6 ECTs. The sample for this study came from a randomized controlled trial, comparing the efficacy of bifrontal and bitemporal electrode placements in schizophrenia. EEG was recorded using bilateral frontal pole leads during all ECT sessions. In 40 of the 114 randomized patients, we could obtain artifact-free EEGs for the first 6 ECT sessions. FD was calculated using standardized algorithms. For each session, the average of 5 highest FDs was calculated. The change in this value over a course of 6 ECTs was analyzed using repeated-measures analysis of variance. The average highest FD remained virtually unchanged across the 6 ECT sessions. Means (standard deviations) average maximum FDs over the 6 sessions were 1.57 (0.075), 1.57 (0.064), 1.56 (0.064), 1.57 (0.062), 1.55 (0.07), and 1.56 (0.067); occasion effect, F = 0.5, P = .75. Group effect (F = 0.01, P = .92) and group × occasion interaction effect (F = 1.88, P = .1) were not significant, suggesting no influence of electrode placement on maximum FD. Seizure duration, however, showed significant decline over the course of ECT. Maximum FD of ECT-induced EEG seizure remains fairly constant over frontal poles across the first 6 ECT sessions, which is true irrespective of ECT electrode placements.

Single fiber electromyographic jitter and detection of acute changes in neuromuscular function in young and adult rats

Introduction Exposure to irreversible cholinesterase (ChE)-inhibiting compounds, such as organophosphates may produce neuromuscular dysfunction. However, less is known about changes in neuromuscular transmission after treatment with reversible ChE-inhibitors. These studies adapted single fiber electromyography (SFEMG) techniques to quantify neuromuscular jitter in adult and juvenile rats after treatment with agents that alter cholinergic neurotransmission. Methods Anesthetized adult and juvenile rats were tested using stimulation SFEMG, recorded in the gastrocnemius muscle, after stimulation in the sciatic notch region. The influence of electrode placement, treatment with decamethonium (to disrupt neuromuscular transmission) or physostigmine (reversible ChE inhibitor), and the impact of varied stimulation frequency were quantified. Results No significant effects of needle placement or criterion amplitude were observed when calculating the mean consecutive difference (MCD). Treatment with decamethonium did not alter MCD values in adult or juvenile rats. However, decamethonium produced an increased blocking of muscle action potentials (MAP) in juveniles. Also, when stimulated at 9.09 Hz, both adult and juvenile animals had a greater decrease in MAP amplitude between the first and fourth responses ( T 1– T 4 decrement) after treatment with decamethonium. Prior to treatment with decamethonium, the T 1– T 4 decrement averaged about 3 fold greater in juveniles than adults, and was larger at 3.03 and 9.09 Hz than with 0.91 Hz stimulation. Treatment with physostigmine resulted in at least 50% inhibition of muscle ChE activity, but produced minimal changes in the MCD values in adults or juveniles. Combined over treatments and stimulation frequencies, the median MCD for juveniles (11.6 µs) was less than that for of adults (18.8 µs). In juveniles, the median MCD increased from 9.3 µs to 13.9 µs as the stimulation rate was increased from 0.91 to 9.09 Hz. This stimulus-dependant change was more evident in juveniles than in adults. Discussion A technique was developed to record stimulation SFEMG and neuromuscular jitter, in vivo, in adult and juvenile rats. The method was sufficiently sensitive to detect age-related differences, potentially allowing developmental processes to be examined. Based on the literature and the current data, the technique appears to be more sensitive to prolonged inhibition of ChE enzymes than the reversible inhibition produced by physostigmine.

Day-to-day variability of electrocardiographic diagnosis of left ventricular hypertrophy in hypertensive patients. Influence of electrode placement

Although electrocardiography (ECG) is recommended in all subjects with hypertension, no information is available on the influence exerted by random changes in the placement of electrodes on the day-to-day variability of ECG criteria for diagnosis of left ventricular hypertrophy (LVH). In a multicentre, randomized study, two standard 12-lead ECG were recorded, 24 h apart, from 276 consecutive hypertensive patients (mean age 65 +/- 12 years, 49.6% men). Overall, 142 patients were randomized to ECG with the position of electrodes marked on the skin using a dermographic pen and 134 to traditional ECG without marking the position of electrodes. Day-to-day variability of ECG criteria for LVH was compared between the two groups. Coefficients of variation (SD of the difference between paired voltage measurements divided by the mean value) varied consistently among subjects randomized to ECG without dermographic pen, ranging from 30% (R wave in lead I) to 81% (R wave in lead V5). Dermographic pen led to a lesser variability of ECG voltages with consequent reduction in the coefficients of variation, which ranged from 26% (R-wave amplitude in lead I) to 43% (R-wave amplitude in lead V5). The proportion of subjects who changed classification status for LVH ('reclassification rate') from the first to the second ECG session (LVH present in session 1 and absent in session 2, or vice versa) decreased for effect of dermographic pen from 11 to 4% (P = 0.040) with the Cornell voltage, from 19 to 11% (P = 0.029) with the Sokolow-Lyon voltage, and from 18 to 7% with the Romhilt-Estes criterion (P = 0.018), but not with other criteria. In particular, the typical strain and the Cornell strain were associated with the lowest reclassification rates regardless of dermographic pen. Random changes in the position of ECG electrodes strongly impair the day-to-day reproducibility of Cornell voltage, Sokolow-Lyon and Romhilt-Estes criteria for LVH. The typical strain and Cornell strain criteria showed a lesser spontaneous day-to-day variability.

Influence of electrode placement on effective field strength in the superficial digital flexor tendon of horses

To determine the relationship between the output of an electrical treatment device and the effective field strength in the superficial digital flexor tendon of horses. Cadaver horse forelimbs without visible defects (n = 8) and 1 live pony. Microcurrents were generated by a microcurrent electrical therapy device and applied in proximodistal, dorsopalmar, and mediolateral directions in the entire forelimbs, dissected tendons, and the pony with various output settings. Corresponding field strengths in the tendons were measured. A linear relationship was detected between current and field strength in all conditions and in all 3 directions. In dissected tendons, significant differences were detected among all 3 directions, with highest field strength in the proximodistal direction and lowest in the dorsopalmar direction. In the entire forelimbs, field strength in the proximodistal direction was significantly lower than in the mediolateral direction. Results in the pony were similar to those in the entire forelimbs. Electrode placement significantly affected field strength in the target tissue. Many surrounding structures caused considerable reduction of field strength in the target tissue. These factors should be taken into account when establishing protocols for electrical current-based therapeutic devices if these devices are proven clinically effective.

The Influence of Electrical Variables on Analgesia Produced by Low Current Transcranial Electrostimulation of Rats

Pulsed low current transcranial electrostimulation (TE) has been shown to induce analgesia in rats as measured by the wet tail flick test. This study investigates the effect of varying stimulus frequency, pulse width, charge balance and polarity, as well as the influence of electrode placement and time of day at which stimulus occurred. A biphasic, charge balanced waveform with a first phase duration of 2 msec, current 10 microA and repetition rate 10 Hz was found to induce maximum tail flick latency changes. The effects of morning or nighttime stimulation were statistically indistinguishable, as were the differences between monophasic and biphasic stimulation. Analgesia was maximized when a positive first phase was delivered into the right ears of the rats, but monolateral stimulation with both electrodes on either the left or the right ear produced no measurable effect. Examination of TE responses in sham and stimulated populations reveals normal response distributions with the stimulated group skewed toward a positive effect.

The influence of electrode placement in the reconstruction and analysis of body surface potential maps from limited thoracic arrays

Despite their capacity to indicate abnormality outside the scope of routine electrocardiography, body surface maps remain extensive, time-consuming research procedures. By contrast, a 35-electrode grid which sums precordial ST segment deviations has received wide attention as a clinical monitor of acute myocardial infarction. First, this study examined the feasibility of recovering essential data from a small electrode array to construct maps equal to those obtained from a much larger array. Such a small-array technique would offer economy, easy application, plus the comprehensiveness and clinical correlation of the large system. Second, the relationships between map, small-array and a 35-component equivalent multipolar generator were explored for a transformation system which both expands the small-array data to map displays and reduces such data to non-redundant waveforms. Comparisons were made between direct maps and those derived from two 35-electrode sets on normal subjects and patients with myocardial infarction or cardiomyopathy. Electrode placement did not conform to the conventional rectangular grid; for one, the electrodes encircled the thorax symmetrically; in the other they were statistically selected for signal information content. We found 1) symmetrical electrode placement and analytic reconstruction of maps from multipolar lead components consistently reproduced known maps well (.91 correlation, 120 microvolts error); but 2) empirical electrode placement and statistical prediction of known maps averaged .99 correlation and 20 microvolts error for the normal training population and .97 and 60 microvolts for the abnormal test sample. Worsening occurred when placement and prediction methods were mixed; however, maps reconstructed by the empirical-statistical approach reduced to a reasonable approximation of equivalent generator scalar leads.