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PubMed1978

Complications with permanent endocardial electrode systems. A comparison between two types of electrodes.

The study comprises 375 patients who had received an endocardial pacemaker electrode primarily. A stylet electrode of the Medtronic type was used in 165 patients and of the Elema type in 79 patients. Elema's flexible electrode model 588 EMT was used in 131 patients. The total number of electrode complications was surprisingly high. In 92 out of the 375 patients, 141 serious episodes of pacing failure occurred during the observation period of from 6 to 42 months. The complication rate increased with pacemaker function time. The stylet electrodes gave the highest complication rate. The choice of vein for introducing the electrode into the heart seems not to affect the complication rate significantly. Nor did the initial threshold value of stimulation influence the complication rate to any marked degree. The pacemaker manufacturers have devoted much effort to producing long-life impulse generators but there is also a great need for well-functioning long-life electrodes.

Clinical Trials as Topic↗
PubMed1995

Averaged electrode voltages: management of electrode failures in children, fluctuating threshold and comfort levels, and otosclerosis.

Implant-generated surface potentials, or averaged electrode voltages (AEVs), were collected by means of the electrode-by-electrode (E-E) mapping variable mode strategy. Three topics were investigated. 1) Eighteen children under the age of 7 were tested and the E-E map of 4 of them was found deviant; all 4 children were deaf owing to meningitis. Some electrodes marked as failing by E-E mapping did not cause problems during device fitting, and electrodes not usable in device fitting showed normal AEVs in 1 child. Overall, the AEVs agreed well with abnormalities in the behavioral threshold (T) and comfort (C) levels. The E-E maps provided useful clues for the audiologist in most cases. 2) Repeated E-E mapping in 2 children who displayed large fluctuations over time of T levels suggested a fluctuation in (neural) responsiveness in 1 child and new bone formation in the other. 3) Although massive phase reversals of AEVs in 2 patients deafened by otosclerosis seemed to indicate a very permeable cochlear bone, stimulation in the pseudomonopolar mode across the basal turn did not affect T levels, and affected pitch perception in only 1 patient. Deviant AEVs from abnormal cochleas should, therefore, not be interpreted too easily as an indication of an electrode failure, faulty electrode placement, or inadequate tonotopy.

Child↗
PubMed2002

Traceability of pH measurements by glass electrode cells: performance characteristic of pH electrodes by multi-point calibration.

Routine pH measurements are carried out with pH meter-glass electrode assemblies. In most cases the glass and reference electrodes are thereby fashioned into a single probe, the so-called 'combination electrode' or simply 'the pH electrode'. The use of these electrodes is subject to various effects, described below, producing uncertainties of unknown magnitude. Therefore, the measurement of pH of a sample requires a suitable calibration by certified standard buffer solutions (CRMs) traceable to primary pH standards. The procedures in use are based on calibrations at one point, at two points bracketing the sample pH and at a series of points, the so-called multi-point calibration. The multi-point calibration (MPC) is recommended if minimum uncertainty and maximum consistency are required over a wide range of unknown pH values. Details of uncertainty computations for the two-point and MPC procedure are given. Furthermore, the multi-point calibration is a useful tool to characterise the performance of pH electrodes. This is demonstrated with different commercial pH electrodes. ELECTRONIC SUPPLEMENTARY MATERIAL is available if you access this article at http://dx.doi.org/10.1007/s00216-002-1506-5. On that page (frame on the left side), a link takes you directly to the supplementary material.

Journal Article↗
PubMedDate not supplied

Comparison between Dawson, Trick, and Litzkow electrode and contact lens electrodes used in clinical electroretinography.

PURPOSE: To determine the reliability of the Dawson, Trick, and Litzkow (DTL) electrode in electroretinographic recordings (ERG) in subjects of all ages, we evaluated ERG responses obtained with the contact lens (CL) and DTL electrodes and estimated a DTL/CL ratio for each sample. METHODS: Seventy-nine volunteers aged 2-84 years (79 normal eyes) were recruited for the study. Electroretinographic recordings elicited by monocular single-flash stimuli delivered by an automatic ERG recording system were recorded using both CL and the DTL electrodes (CL-ERG and DTL-ERG, respectively). RESULTS: The relative amplitude of the DTL-ERG to the CL-ERG was 79.6-99.8% (mean = 93.4%) for the a-wave and 84.4-106.3% (mean = 92.3%) for the b-wave. The relative latency of the DTL-ERG to the CL-ERG was 86. 0-107.6% (mean = 98.2%) for the a-wave and 96.1-113.0% (mean = 97. 9%) for the b-wave. The a- and b-wave amplitudes differed significantly between DTL and CL electrodes only in the 40- to 49-year-old age groups (P <.05). Regression analysis indicated moderate to strong relationships between the electrodes for amplitude (a-wave, r = 0.690; b-wave, r = 0.824) and latency (a-wave, r = 0.667; b-wave, r = 0.725). CONCLUSION: The DTL electrode has as high stability as the conventional CL electrodes for ERG recordings in most age groups.

Adolescent↗
PubMed2006

Comparison of electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb, Ge, Zr-added TiO2 composite electrodes.

Electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were examined to disclose the effects of partial substitution of Ti atom by the other metals in the composite electrodes. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were prepared by sol-gel process using laurylamine hydrochloride as a template for the formation of micellar precursors yielding well-defined mesoporous nanocrystalline structures, as in the cases of the formation of silica and titania tubules and nanoparticles by the templating mechanism. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were characterized by transmission electron microscopy, BET surface area analysis, X-ray diffraction analysis, Raman spectroscopy, and impedance measurements. The TiO2 anatase nanocrystalline structure is retained after doping a small amount (5 mol %) of Nb, Ge, or Zr into the TiO2 structure, suggesting the homogeneous distribution of the doped metals with replacing Ti atom by the doped metal. The power conversion efficiency of the porphyrin-sensitized solar cells increases in the order Zr-added TiO2 (0.8%) < Nb-added TiO2 (1.2%) < TiO2 (2.0%) < Ge-added TiO2 cells (2.4%) under the same conditions. The improvement of cell performance of the Ge-added TiO2 cell results from the negative shift of the conduction band of the Ge-added TiO2 electrode. The Ge-added TiO2 cell exhibited a maximum power conversion efficiency of 3.5% when the porphyrin was adsorbed onto the surface of the Ge-added TiO2 electrode with a thickness of 4 microm in MeOH for 1 h.

Journal Article↗
PubMed1993

Transmitter amino acid levels in rat brain regions after amygdala-kindling or chronic electrode implantation without kindling: evidence for a pro-kindling effect of prolonged electrode implantation.

Kindling is a chronic model of epilepsy characterized by a progressive increase in response to the same regularly applied stimulus. The biological basis of the kindling phenomenon requires to be determined, but several studies indicate that alterations in amino acidergic neurotransmission may be involved. In the present experiments, levels of glutamate, aspartate, GABA, glycine, and taurine were determined in 12 brain regions by HPLC in 3 groups of animals: (a) a group which was kindled via electrical stimulation of intraamygdala electrodes and was sacrificed 36 days after the last fully kindled seizure for neurochemical determinations; (b) a group of implanted but nonstimulated rats (surgical control group) in which neurochemical measurements were done at the same time after electrode implantation as the kindled group, and (c) a group of non-implanted, naive control rats. Compared to surgical controls, kindling induced a significant reduction of glutamate, GABA, and taurine in the brain stem (pons/medulla), whereas no differences between both groups were found in any of the other regions. However, both electrode-implanted groups differed significantly from non-implanted naive rats in several regions, indicating that electrode-implantation per se induced long-lasting alterations in transmitter amino acids. The most striking difference to naive controls was an increase of glycine levels in several regions in which this amino acid is known to potentiate glutamatergic transmission. In order to examine the functional consequences of prolonged electrode implantation, seizure thresholds were determined in groups of rats with short and prolonged electrode implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed2006

Current-level discrimination in the context of interleaved, multichannel stimulation in cochlear implants: effects of number of stimulated electrodes, pulse rate, and electrode separation.

The ability of cochlear implantees to detect an increment in current level at one of many stimulated electrodes was investigated. Such changes in the electric profile provide information for cochlear implantees to discriminate numerous sounds, especially vowels. In Experiment 1, sensitivity to increases in current level at one stimulation site in the electric profile decreased as the number of stimulated electrodes increased. This outcome was most likely a result of decreased stimulus levels at individual electrodes that were required to retain a comfortable loudness when the number of active electrodes was increased. Experiment 2 investigated the effects of pulse rate and separation between stimulation sites when the levels in percent of dynamic range and number of stimulated electrodes were held constant. The effect of pulse rate and electrode separation varied among listeners. The sensitivity of 6 of 9 listeners was best at the pulse rate that they used clinically. This might have been the result of adaptation to the clinical pulse rate, or listeners might have chosen their inherently best pulse rate during the clinical fitting.

Adult↗
PubMed1976

The sutureless electrode: comparison with transvenous and sutured epicardial electrode placement for permanent pacing.

Consecutive series of 50 transvenous and 50 sutureless pacemaker insertions were reviewed and compared with a nonsimultaneous series of 50 patients who received sutured epicardial pacemakers. It is concluded that: (1) the sutureless electrode has a lower initial stimulation threshold than the transvenous type; (2) complications from sutureless electrodes are greater than with transvenous electrodes and similar to the incidence with sutured epicardial pacemakers; (3) initial pacing is more satisfactory with the sutureless electrode compared with the transvenous model; and (4) late electrode failure due to threshold rise is greater with the sutureless electrode than with the transvenous or sutured epicardial type.

Action Potentials↗
PubMed1997

A new type of hydrophilic carbon paste electrodes for biosensor manufacturing: binder paste electrodes.

The effect of two types of carbon pastes and two osmium-based redox mediators on the response of amperometric enzyme electrodes for glucose was examined. A hydrophobic mediator and a hydrophilic cationic mediator were prepared and mixed in a paste that contained either mineral oil as the pasting liquid, or a polycationic electrolyte without oil. It was found that the current densities were increased by a factor of 25 when the oil-based paste was replaced by the hydrophilic one (binder paste, BP) and five- to six-fold when the hydrophilic mediator was used in place of the hydrophobic. The linear range for the glucose oxidase electrodes was extended to concentrations higher than 60 mM. The glucose electrodes were preliminary optimized and their half-life time reached more than 12 h when operated continuously under vigorous stirring when the 'pasting' polyelectrolyte was crosslinked. At a working potential of 400 mV versus the Ag/AgCl saturated electrode, the saturating current densities per geometric surface area were 1.2 mA/cm2 +/- 0.2 (n = 7). These 'binder paste electrodes' are the first reported bulk modified electrodes without hydrophobic pasting liquid or cover membranes, and present an interesting research and application tool.

Biosensing Techniques↗
PubMed2001

Rotating electrode potentiometry: lowering the detection limits of nonequilibrium polyion-sensitive membrane electrodes.

A rotating electrode configuration is evaluated as a means to lower the detection limits of newly devised polyion-sensitive membrane electrodes (PSEs). Planar potentiometric polycation and polyanion PSEs are prepared by incorporating tridodecylmethylammonium chloride and calcium dinonylnaphthalenesulfonate, respectively, into plasticized PVC or polyurethane membranes and mounting disks of such films on an electrode body housed in a conventional rotating disk electrode apparatus. Rotation of the PSEs at 5000 rpm results in an enhancement in the detection limits toward heparin (polyanion) and protamine (polycation) of at least 1 order of magnitude (to 0.01 unit/mL for heparin; 0.02 microg/mL for protamine) over that observed when the EMF responses of the same electrodes are assessed using a stir-bar to achieve convective mass transport. A linear relationship between omega(-1/2), where omega is the rotating angular frequency, and C1/2, the polyion concentration corresponding to half the total maximum deltaEMF response toward the polyion species, is observed. It is further shown that the rotating polycation sensor can be used as an end-point detector to greatly enhance (relative to nonrotated indicator electrode) the analytical resolution and precision for measurement of low concentrations of heparin when such samples are titrated with protamine. The theoretical basis for lowering the detection limits by rotating PSEs is discussed based on the unique nonequilibrium response mechanism of such sensors.

Electrodes↗
PubMed2003

Characterization of electrode fouling and surface regeneration for a platinum electrode on an electrophoresis microchip.

A method of electrochemically cleaning noble metal electrodes is presented and characterized for electrophoresis microchips with electrochemical detection. First, the loss of sensitivity due to electrode fouling by serotonin is characterized as a function of injection number and analyte concentration. Signal attenuation is observed to be greater at high concentrations (100 microM) and negligible at very low concentrations (approximately 1 microM). Next, an electrochemical treatment procedure is optimized to yield sensitive and reproducible amperometric detection of the highly adsorptive compounds, serotonin and histamine. Thus, the performance of the electrode is reproducibly regenerated following as much as a approximately 99% reduction in surface activity. Utilizing the optimized three-level waveform, derived from that used for pulsed amperometric detection, detection limits as low as 78 nM and 17 microM have been obtained for serotonin and histamine, respectively. In the case of serotonin, this represents the lowest detection limit for a neurotransmitter by microchip electrophoresis with amperometric detection and the first report of amperometric detection of histamine detection at an unmodified platinum electrode. Repeated use of the electrode and application of electrochemical treatment did not appear to measurably affect the noise, longevity, metal adhesion, or physical appearance of the electrode.

Electrochemistry↗
PubMed1991

A new class of electrodes of 'intermediate invasiveness': preliminary experience with epidural pegs and foramen ovale electrodes in the mapping of seizure foci.

Non-invasive electroencephalographic (EEG) recording with scalp and sphenoidal leads is often insensitive to precise localization of ictal onset, and can be distorted by skull defects and underlying lesions or deformities of the brain. We present preliminary experience with epidural pegs and foramen ovale electrodes used in 30 cases of intractable partial epilepsy where non-invasive EEG did not define a zone of epileptogenesis with sufficient precision to recommend resection, or to dictate precise placement of depth electrodes or subdural girds. Custom designed mushroom shaped peg electrodes were implanted via 4.5 mm twist-drill skull holes for epidural recording from cortical areas of suspected epileptogenesis. Foramen ovale electrodes (flexible 3-contact leads) were introduced via percutaneous puncture of Meckel's cave cistern for recording from mesiotemporal regions. Chronic recording was performed for 4 to 26 days (mean 9.2 days). There were no serious complications and signal quality was excellent in every electrode. Based on interictal and ictal records, resective surgery was performed in 8 cases, more focused further invasive recording was recommended in 15 cases (with subsequent resective surgery), and surgical options were excluded in 7 cases. It is concluded that these electrodes of 'intermediate invasiveness' represent a safe and effective tool in the armamentarium for mapping complicated or elusive epileptic foci. They can be used in lieu of, in addition to, or prior to more invasive measures. Their greatest advantage lies in their relative safety and ability to survey extensive zones of suspected epileptogenesis so as to guide and focus further mapping and surgical intervention.

Adolescent↗
PubMed2001

Interaction of array of finite electrodes with layered biological tissue: effect of electrode size and configuration.

A hybrid scheme, combining image series and moment method has been utilized for the calculation of the intramuscular three-dimensional (3-D) current density (CD) distribution and potential field transcutaneously excited by an electrode array. The model permits one to study the effect of tissue electrical properties and electrode placement on the CD distribution. The isometric recruitment curve (IRC) of the muscle was used for parameter estimation and model verification, by comparison with experimentally obtained IRCs of functional electrical stimulation (FES)-activated quadriceps muscle of paraplegic subjects. Sensitivity of the calculated IRC to parameters such as tissue conductivity, electrode size, and configuration was verified. The resulting model demonstrated characteristic features that were similar to those of experimentally obtained data. The model IRCs were insensitive to the electrode size; however, the inclusion of the bone-fascia layer significantly increased the intramuscular CD and, consequently, increased the IRC slope. Of the different configurations studied, a four-electrode array proved advantageous because, in this case, the CD between the electrodes was more evenly distributed, providing better resistance to fatigue. However, due to the steeper linear portion of the IRC, this configuration suffered from a somewhat reduced controllability of the muscle.

Electric Conductivity↗
PubMed1997

Transmembrane voltage changes produced by real and virtual electrodes during monophasic defibrillation shock delivered by an implantable electrode.

INTRODUCTION: Epicardial point stimulation produces nonuniform changes in the transmembrane voltage of surrounding cells with simultaneous occurrence of areas of transient positive and negative polarization. This is the phenomenon of virtual electrode. We sought to characterize the responses of epicardial ventricular tissue to the application of monophasic electric shocks from an internal transvenous implantable cardioverter defibrillator (ICD) lead. METHODS AND RESULTS: Langendorff-perfused rabbit hearts (n = 12) were stained with di-4-ANEPPS. A 9-mm-long distal electrode was placed in the right ventricle. A 6-cm proximal electrode was positioned horizontally 3 cm posteriorly and 1 cm superiorly with respect to the heart. Monophasic anodal and cathodal pulses were produced by discharging a 150-microF capacitor. Shocks were applied either during the plateau phase of an action potential (AP) or during ventricular fibrillation. Leading-edge voltage of the pulse was 50 to 150 V, and the pulse duration was 10 msec. Transmembrane voltage was optically recorded during application of the shock, simultaneously from 256 sites on a 11 x 11 mm area of the anterior right ventricular epicardium directly transmural to the distal electrode. The shock effect was evaluated by determining the difference between the AP affected by the shock and the normal AP. During cathodal stimulation an area of depolarization near the electrode was observed, surrounded by areas of hyperpolarization. The amplitude of polarization gradually decreased in areas far from the electrode. Inverting shock polarity reversed this effect. CONCLUSION: ICD monophasic defibrillation shocks create large dynamically interacting areas of both negative and positive polarization.

Action Potentials↗
PubMed2002

Evaluation of skin barrier function using direct current I: effects of conductivity, voltage, distance between electrodes and electrode area.

The objective of this study was to evaluate the reduction in skin barrier function caused by direct current iontophoresis by measuring resistance in the short term. The experiments were carried out using rat abdominal skin in vivo. The resistance was measured every 125 ms and analyzed using a two-compartment model consisting of surface and skin resistance. Moreover, the initial value and the rate constant of each resistance were calculated with the non-linear approximation program. The proposed method could evaluate the reduction in barrier function from the initial value and the rate constant of surface resistance with high sensitivity and accuracy. Using this proposed method, the effects of the conductivity of an adhesive pad, voltage, the distance between electrodes and the area of electrode were examined. The increase in conductivity of the adhesive pad decreased the initial value since the rate constant increased. The reduction in barrier function depends on voltage. Although the barrier function decreased up until an electrode distance of 1 cm, it increased beyond 1 cm. These phenomena contributed to the current pass portion in the skin because the resistance was in the order of the stratum corneum, epidermis and dermis. The initial value decreased with increasing electrode area. However, the rate constant was little affected since the current density of a topical electrode adjacent to the other electrode was high.

Administration, Cutaneous↗
PubMed2001

Anodization in oligo(ethylene glycol) as an initial derivatization tool for preparing glassy carbon electrodes covalently modified with amino compounds: effective access to a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-modified glassy carbon electrode.

Anodization in HO(CH2CH2O)nH (1a, n=2; 1b, n=3; 1c, n=4) as an initial derivatization tool for preparing glassy carbon (GC) electrodes covalently modified with amino compounds was explored. As an amino compound to be immobilized, 4-amino-2,2,6,6-tetramethylpiperidinyl-1-oxyl (4-amino-TEMPO) was selected. When GC electrodes anodized at 2.0 V vs. Ag wire coated with AgCl in 1 containing RCH2CH2SO3Na (2a, R=H; 2b, R=OH) were treated with a N,N-dimethylformamide (DMF) or CH2Cl2 solution of 4-amino-TEMPO and 1,3-dicyclohexylcarbodiimide (DCC), TEMPO-modified GC electrodes were afforded. Coverage (gammaTEMPO) of the electrode surfaces by TEMPO was estimated by cyclic voltammetry in CH3CN containing NaClO4. A TEMPO-modified GC electrode with the best gammaTEMPO (1.36 x 10(-10) mol/cm2) was obtained by anodization in 1b containing 2a at the expense of 3.0 C followed by amidization in DMF for 7 d. On cyclic voltammetry, the TEMPO-modified GC electrode showed good and stable electrocatalytic ability for oxidation of allyl alcohol in the presence of 2,6-lutidine.

Carbon↗
PubMed1990

Effects of electrode placement on the auditory brainstem response using ear canal electrodes.

The effects of electrode placement on the latency and amplitude of the auditory brainstem response (ABR) were investigated in normal-hearing subjects. Ear canal (EC) electrodes were used in conjunction with surface electrodes to obtain ABRs. Three electrode combinations were evaluated: (1) vertex-EC-EC; (2) vertex-EC-neck; and (3) forehead-EC-neck. Absolute and interwave latencies and absolute and relative amplitudes were computed for Waves I, III, and V at 75 dB SL. Standard errors of measurement (SEmeas) revealed excellent test-retest reliability for latency (SEmeas = 0.06 ms) but only fair reliability for amplitude (SEmeas = 55 nv). No reliability differences were observed among the three electrode combinations. No significant latency or interwave latency differences were found among the three montages. No amplitude differences were found for Waves I and III among the montages. However, the Wave V amplitude was larger for the vertex-EC-EC and vertex-EC-neck montages than for the forehead-EC-neck montage. Because the vertex-EC-EC montage does not require additional electrodes on the contralateral neck, this montage is recommended.

Acoustic Stimulation↗
PubMed1977

Avulsion of a tricuspid valve leaflet during traction on an infected, entrapped endocardial pacemaker electrode. The role of electrode design.

Endocardial pacemaker electrodes rely in part upon endocardial fixation proximal to the electrode tip to prevent ejection of the tip from the ventricular apex. Fixation of these electrodes to the superior vena cava and tricuspid valve, in particular, has been reported. Infection of endocardial electrodes necessitates their removal. This report concerns avulsion of a tricuspid valve leaflet during traction on an infected electrode. With the availability of new methods of apical fixation, the utilization of electrode sheathing materials which discourage endocardial fixation would increase the safety of their removal under the circumstances reported herein.

Aged↗