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PubMed1997

Comparison of preoperative electrostimulation data using an ear-canal electrode and a promontory needle electrode.

OBJECTIVE: To compare the electrical stimulation results of the ear-canal electrode with those of a promontory needle. PATIENTS AND METHODS: In thirty-three adult patients, the ear-canal electrode test was compared with the needle electrode promontory test with respect to sound perception, rhythm detection, frequency, and disturbing side effects. RESULTS: The ear-canal electrode test, in comparison with the needle electrode promontory test, resulted in vibrotactile sensation in addition to auditory sensation in some patients, less auditory fatigue, higher threshold levels, and lower discomfort levels. CONCLUSION: Reliable assessment of deafness in children requires, in addition to electrical stimulation, determination of the electrical evoked auditory brainstem response with the patient under anesthesia.

Adult↗
PubMed2000

Endovascular neural stimulation via a novel basket electrode catheter: comparison of electrode configurations.

We previously showed that parasympathetic stimulation by a basket electrode catheter (BEC) positioned in the superior vena cava (SVC) can slow sinus rate (SR) or ventricular response (VR) during atrial fibrillation (AF). In 11 dogs, anesthetized with Na-pentobarbital, standard ECG leads II and aVR, blood pressure and right atrial electrograms were continuously monitored. Two different BEC configurations (B1, B2) were tested in the SVC. B1 consisted of five metal splines, each 3 cm in length. Stimulation was applied between adjacent splines. B2 consisted of 2 electrodes at opposite ends of each of 5 splines and a larger electrode at the middle of each spline. Stimulation was delivered between the two end electrodes and the middle electrode on the same arm. Stimulation consisted of square wave stimuli, each 0.1 msec duration, frequency 20 Hz at voltages from 1-40 V. Six dogs were studied with B1 and five were studied with the B2 configuration. The average voltage required to produce a 50% decrease in heart rate was 22+/- 12 V when stimulating between adjacent splines (B1) compared to 10+/- 5 V when stimulating along a single spline (B2), a 55% decrease (p</=0.05). During AF, the voltage required to reduce the average ventricular rate to 100 beats/min was 19+/- 13 V for B1 and 8+/- 5 V for B2, a 58% reduction (p</=0.05). Thus, the significant difference between B1 and B2 and in slowing SR or VR during AF was probably due to a greater current density delivered with B2 to the endovascular wall and adjacent neural elements.

Animals↗
PubMed2005

Regular arrays of microdisc electrodes: simulation quantifies the fraction of 'dead' electrodes.

Arrays of microdisc electrodes have found widespread use in electroanalysis. These are commonly produced lithographically and practical arrays may contain up to hundreds of individual disc electrodes (e.g. of gold, platinum, indium,...) to maximise sensitivity and minimise limits of detection. Typically, however, the lithographic fabrication process is imperfect resulting in a significant fraction (often tens of percent) of electrochemically inactive electrodes. We demonstrate that a 2-dimensional simulation based on the diffusion domain approximation in conjugation with simple experiments on the ferrocyanide redox couple in aqueous solutions can be used to rigorously 'count' the number of active electrodes in a non-destructive fashion. The agreement with an independent count in which active electrodes are identified via electro-plating with copper followed by ex situ microscopic examination is quantitatively excellent.

Calibration↗
PubMed2004

rf Electrode sheath formation near a concave electrode.

In this work we present experimental results concerning electrode sheath and ion flux formation near a concave electrode with the dimension of a cavity comparable to the electrode sheath length. It is shown that the secondary electron emission can play a crucial role in plasma molding over the electrode surface. It is also observed that plasma has a tendency to "self-leakage" in electrode cavities.

Journal Article↗
PubMed1975

Electrical stimulation of the brain. I. Electrodes and electrode arrays.

Investigators engaged in studying the effects of electrical stimulation on the blood-brain barrier (BBB) and brain usually find it necessary to fabricate the electrodes and electrode arrays required in their acute and chronic experiments. Techniques for fabricating spring-mounted, concentric and salt-bridge electrodes and electrode arrays are described in this report.

Blood-Brain Barrier↗
PubMed1990

Comparisons between surface electrodes and intramuscular wire electrodes in isometric and dynamic conditions.

The purpose of this study was to compare EMG surface electrodes (SE) and intramuscular wire electrodes (IWE) for isometric and dynamic contractions during an occupational cervico-brachial working task (OCWT). Six normal adult male subjects were tested on two days (two conditions with three trials each). Raw EMG signals from middle deltoid, anterior deltoid and trapezius muscles were recorded by both IWE and SE for two conditions (isometric and dynamic contractions). Full wave rectified and low pass filtered EMG, and integrated EMG were processed from raw EMG signals. The statistical analysis performed on the integrated EMG was a factorial analysis model with repeated measures. Statistical results confirmed that EMG signals, from both SE and IWE, are reliable between trials on the same day. These statistical results also confirmed that SE are more reliable than IWE on day-to-day investigations. Both electrodes recorded statistically similar signals, although the coefficient of variability between electrodes was very high (STDE%; 48% and 84%, for isometric and dynamic conditions respectively).

Adolescent↗
PubMedDate not supplied

Enzyme electrode composed of the pyruvate oxidase from Pediococcus species coupled to an oxygen electrode for measurements of pyruvate in biological media.

Pyruvate oxidase from Pediococcus species was immobilized with gelatin and insolubilized in film form by tanning with glutaraldehyde. The film was fixed onto the tip of an oxygen electrode. The enzyme electrode was specific for pyruvate measurements. This electrode was sensitive to 0.1 mM and could be used up to a final pyruvate concentration of 2 mM. At each step of the enzymatic film preparation and assay 0.7 mM thiamine pyrophosphate, 10 microM flavin adenine dinucleotide, 5 mM Mg2+ and 10 mM phosphate buffer were necessary. A computerized probe allowed successive measurements every 3 min for more than 20 h with the same enzymatic film. The reproducibility for the same pyruvate concentration was 2% during 400 assays without special optimization. This enzyme electrode has many applications in basic (metabolism, enzymology) and applied (blood, yoghurt) research. Results obtained from assays carried out in yoghurt are presented.

Electrodes↗
PubMed2006

A comparison of subdermal wire electrodes with collodion-applied disk electrodes in long-term EEG recordings in ICU.

OBJECTIVE: To compare long-term electroencephalographic (EEG) recordings of standard collodion-applied scalp disk electrodes (SDEs) with newly developed subdermal wire electrodes (SWEs) in comatose intensive care unit (ICU) patients. METHODS: Ten comatose ICU patients had simultaneous recordings from 8 active SDEs and 8 active SWE for >24 h. The timing and number of 60 Hz and other electrode artifacts were compared for each set of electrodes by an EEGer who read the recordings in a blinded manner. RESULTS: Sixty Hertz artifact was seen in 16 of 80 SDE and one of 80 SWEs within the first 6 h (P=0.0002). Large, persistent artifacts occurred in 30/80 SDE and 8 of 80 SWE (P=0.0001). Motion artifact with chest physiotherapy was more common in SWEs. CONCLUSIONS: SWE are less susceptible to artifacts and are more suitable for the long-term EEG monitoring in ICU. SIGNIFICANCE: This is the first controlled study that demonstrates the superiority of SWEs compared to SDEs in an ICU population.

Adolescent↗
PubMed2005

The role of electrode impedance and electrode geometry in the design of microelectrode systems.

Microelectromechanical systems (MEMS) employing spatially and/or temporally nonuniform electric fields have been extensively employed to control the motion of suspended particles or fluid flow. Design and control of microelectromechanical processes require accurate calculations of the electric field distribution under varying electrolyte conditions. Polarization of electrodes under the application of an oscillating voltage difference produces dynamic electrical double layers. The capacitive nature of the double layers significantly inhibits the penetration of the electric field through the double layer and into the surrounding bulk electrolyte at low frequencies. This paper quantitatively discusses the effect of electrode impedance on the electric field distribution as a function of field frequency, electrolyte composition, and electrode zeta potential in microelectrode systems. The design principles for the electrode geometry and configuration are also discussed in terms of their effects on the electric field magnitude and nonuniformity.

Electrodes↗
PubMed1991

Use of ion-selective electrodes in kinetic flow injection: determination of phenolic and hydrazino drugs with 1-fluoro-2,4-dinitrobenzene using a fluoride-selective electrode.

A flow injection (FI) kinetic potentiometric method for the determination of phenolic (acetaminophen and isoxsuprine) and hydrazino (isoniazid) drugs is described. This work shows the usefulness of ion-selective electrodes as detectors in FI systems, not only for direct ion determination but also in routine kinetic analysis. The method is based on the reaction of 1-fluoro-2,4-dinitrobenzene (FDNB) with the analytes in a weakly alkaline medium, which proceeds through the liberation of fluoride from the reagent. The slow reactions with phenols are catalysed by micelles of cetyltrimethylammonium bromide. The reaction rate is monitored with a fluoride-selective electrode in a wall-jet configuration and is used to construct a calibration graph of antilog(delta E/S)-1 versus c (where E = potential, s = slope of the electrode and c = concentration), using the fixed-time approach. The response time and the long-term stability of the electrode were found to be adequate for such kinetic determinations. The proposed method overcomes problems associated with end-point spectrophotometric methods using FDNB and allows measurements in highly coloured or turbid solutions. The optimized method has a linear concentration range of 1 x 10(-4)-50 x 10(-4) mol dm-3, a measurement throughput of 20 or 40 per hour and the precision ranges from 1.8 to 3.6% relative standard deviation (n = 3). Results obtained for commercial pharmaceutical formulations compare favourably with those given by reference methods.

Acetaminophen↗
PubMedDate not supplied

[Spinal cord stimulation (SCS) using an 8-pole electrode and double-electrode system as minimally invasive therapy of the post-discotomy and post-fusion syndrome--prospective study results in 34 patients].

AIM: Therapy of a pronounced post-discotomy (PDS) and post-fusion syndrome (PFS) is often unsatisfactory because of the complexity and multifactorial pain genesis. If surgical interventions cannot promise relief and if the entire interdisciplinary spectrum of conservative treatment measures is inadequate, the area of neuromodulative procedures offers spinal cord stimulation (SCS). The objective of this study was to examine the therapeutic possibilities of SCS using an 8-pole electrode and double electrode system in PDS and PFS with extensive back-leg pain areas. METHOD: An appropriate SCS system was implanted in 34 patients with PDS and PFS. Follow-up examinations were made prospectively over a period of 24 months using general criteria and psychometric test measuring instruments validated for German-language use. RESULTS: An 8-pole double electrode system was implanted 23 times, a single electrode sufficed in 11 cases. The area of pain was covered in all patients. This required special technical capabilities of the SCS system. The results remained constant over 24 months. The morphine dose could be reduced by at least 50 %. All measuring instruments confirmed a clear reduction in pain and improvement in quality of life as a result of SCS implantation. CONCLUSION: The SCS is an minimally invasive surgical procedure which can enlarge the therapeutical possibilities of pronounced PDS and PFS resistant to other modes of treatment. Special technical possibilities of parameter setting are required to cover the pain areas.

Adult↗
PubMed2006

[Use of permanent electrodes in the peripheral nerve evaluation test (PNE-Test) in comparison to conventional wire electrodes].

PURPOSE: Prior to implantation of a chronic sacral neurostimulator, it is important to establish which patients might profit from this kind of therapy in order to ensure, by means of a PNE (peripheral nerve evaluation) test, that the implantation of a permanent stimulating device is effective. In this study we compared the two different techniques used in our department (implantation of the permanent neurostimulation electrodes, the so-called "two-stage-implantation" vs. conventional PNE). MATERIALS AND METHODS: We performed a sacral nerve stimulation in 53 patients (mean age: 49.7 years, range: 14 - 75 years) over a minimum of 5 days. In 42 patients we performed a conventional PNE, 11 patients underwent "two-stage implantation" with implantation of the permanent electrodes. RESULTS: 52 of 53 patients received bilateral test stimulation (9 % at S2, 91 % at S3). One patient underwent unilateral PNE (S3) because of an anatomic deformity of the os sacrum. In 20 cases the conventional PNE-test (cPNE) was successful according to standard criteria (47.6 % of all cPNE). The response rate of "two-stage implantation" with implantation of the permanent electrodes was 81.8 % (9 of 11 patients). CONCLUSIONS: The success rate of implantation of permanent neurostimulation electrodes in selecting patients for the permanent implant is significantly higher than the conventional PNE. In this group patients with neurogenic and overactive bladder dysfunctions showed the highest response rates to sacral nerve stimulation and are the most likely to benefit from sacral neuromodulation.

Adolescent↗
PubMed2006

Concentric needle electrodes are superior to perineal surface-patch electrodes for electromyographic documentation of urethral sphincter relaxation during voiding.

OBJECTIVE: To compare interpretations of electromyographic (EMG) recordings from perineal surface patch electrodes (PSPEs) to those from urethral concentric needle electrodes (CNEs) during voiding. PATIENTS AND METHODS: Consenting women underwent urodynamic testing with a 30 G, 3.8 cm CNE at the 12 o'clock position in the striated urethral sphincter muscle, and with PSPEs placed at the 2 and 10 o'clock positions around the anus. Pressure-flow studies were conducted with simultaneous input from both EMG electrodes. Representative, de-identified paper copies of EMG signals were assembled by chronology and electrode type. Six examiners unaware of the patient details were asked to determine if the tracings were interpretable and whether there was quiescence of the urethral sphincter motor unit during voiding. The agreement between the interpretations of each tracing was assessed using McNemar and kappa statistics. RESULTS: Twenty-two women undergoing urodynamic testing for incontinence (16), voiding dysfunction (two) or urinary retention (four) participated in this study. CNE tracings were consistently more interpretable than PSPE tracings (mean 89% vs 67%). When tracings were interpretable, a significantly higher percentage of CNE EMG tracings (mean 79%) had urethral sphincter motor unit quiescence than PSPE EMG tracings (mean 28%). The kappa values for agreement among the reviewers' interpretations were highly variable and none were statistically significant. Reviewers unanimously agreed on only 12 of the 44 tracings, and 11 of these showed quiescence when using a CNE. CONCLUSIONS: CNEs are more often interpretable than PSPEs for determining motor unit quiescence during voiding. CNE EMG appears to have greater clinical utility for central reading than PSPEs.

Electrodes↗
PubMed2004

Experimental comparison of electrodes for intracavitary cardioversion of atrial fibrillation: effectiveness and safety of a new electrode.

UNLABELLED: The right atrium (RA)-external thorax (ET) arrangement has several advantages when used for intracavitary cardioversion of atrial fibrillation (AF): it utilizes a single catheter, the procedure does not need radioscopic follow-up, little endovascular contact results, and there is flexibility in the positioning of the ET electrode. However it is not commonly used and only scantly studied. OBJECTIVES: To evaluate experimentally in animals the efficacy and safety of a new loop electrode placed in the RA in the RA-ET arrangement and to compare it with the RA-pulmonary artery (PA) configuration. METHOD: Ten mongrel dogs with acute induced AF are to be cardioverted with the two arrangements, using increasing levels of energy and its efficacy compared. If lesions show up in the anatomic pathology, a complementary study with three animals will be carried out to assess its origin. RESULTS: The average energy needed for cardioversion was similar in the two arrangements (P = 0.86). Myocardial lesions found were not attributable to the new electrode but supposedly to the AF induction catheter. CONCLUSION: The new electrode model is effective and safe, besides being easy to use and of low cost.

Animals↗
PubMed2000

In vivo potentiostatic studies at the electrode tissue interface: filter properties of the monophasic action potential (Ag/AgCl) electrode in living rat heart.

The monophasic action potential (Franz) catheter is regarded as the criterion standard for high fidelity recording of a class of physiological signals. However, its signal modulation characteristics have never been reported. Broadband impedance spectroscopy was performed in perfused living rat heart in a three-electrode potentiostatic configuration to determine the filtering characteristics of the MAP and model Ag/AgCl electrode-tissue interfaces. The filter transfer function H(f) (attenuation [dB] vs log(f) [log(Hz)]) was derived for the frequency range 10 Hz-10(6) Hz. As a filter, the MAP interface is characterized by two ranges of filtering behavior. At high frequency the MAP interface is a high-pass filter with passband frequency 54 kHz-549 kHz (median 321 kHz) and with -3 dB cutoff points ranging from 10 kHz to 302 kHz. In this high frequency range the transfer function is characterized by decreasing attenuation per decade. However, in the lower frequency range relevant to physiological signals (the monophasic action potential, 0.1-40 Hz), it is a severely attenuating nondiodic high-pass filter element with an average attenuation of 16.87 dB relative to passband. In this physiological range, rolloff is nonlinear with increasing attenuation per decade. While the MAP electrode and model Ag/AgCl electrodes are high-pass filters with robust transfer functions for high frequency signals in the living heart, the attenuation of signals in a frequency range relevant to in vivo physiological recording imparts extreme attenuation that may distort physiological signals unpredictably. This disadvantage may be mitigated by amplitude scaling to a calibrated pure tone signal within the physiological frequency band to recover a reproducible signal.

Action Potentials↗
PubMed1986

Anterior zygomatic electrodes: a special electrode for the study of temporal lobe epilepsy.

The position of a surface electrode over the anterior zygomatic arch is described. Epileptiform activity recorded at this position is compared with that recorded by sphenoidal electrodes in 21 cases of temporal lobe epilepsy. In 100% of the cases abnormalities were detected with both electrodes, although in 11% of the cases the findings could not be definitely described as epileptiform in the anterior zygomatic electrodes.

Adolescent↗
PubMed1987

Analysis of a four-year experience with depth electrodes and a two-year experience with subdural electrodes in the evaluation of ablative seizure surgery candidates.

Chronically implanted depth and subdural electrodes have both been shown to be satisfactory means of localizing epileptogenic foci. Utilizing bilateral mesial temporal depth electrodes, we have localized mesial temporal foci in a large percentage of patients. Depth electrode investigation of a more limited number of patients with suspected extramesial temporal foci has not been as reliable in giving localizing information. We have more recently used subdural electrodes to investigate this latter category of patients, and preliminary findings suggest that this technique may be of localizing value in several subcategories.

Electrodes, Implanted↗
PubMed1996

Modification of a glassy carbon electrode with diols for the suppression of electrode fouling in biological fluids.

The surface of a glassy carbon (GC) electrode was modified covalently with ethyleneglycol, diethyleneglycol, 1,2-propanediol, and 1,3-propanediol by electrochemical oxidation in order to suppress the electrode fouling originating from non-specific adsorption of serum proteins. Human serum albumin (HSA) was adsorbed significantly on the surface of a bare GC electrode, which was monitored by cyclic voltammetry in the presence of Fe(CN)6(4)-/Fe(CN)6(3)-ions. In contrast, the diol-modified GC electrodes were scarcely fouled in HSA solution and even in human serum. The results were explained reasonably based on the hydrophilic nature of the diol-modified GC surface.

Adsorption↗