scholarly journals Oxygen-Induced and pH-Induced Direct Current Artifacts on Invasive Platinum/Iridium Electrodes for Electrocorticography

2021 ◽  
Author(s):  
Sebastian Major ◽  
Nenad Gajovic-Eichelmann ◽  
Johannes Woitzik ◽  
Jens P. Dreier
Keyword(s):  
Direct Current ◽  
Silver Chloride ◽  
Brain Activity ◽  
Blood Oxygenation ◽  
Electrode Polarization ◽  
Voltage Pulses ◽  
Fraction Of Inspired Oxygen ◽  
Silver Silver ◽  
Inspired Oxygen

Abstract Background Spreading depolarization (SD) and the initial, still reversible phase of neuronal cytotoxic edema in the cerebral gray matter are two modalities of the same process. SD may thus serve as a real-time mechanistic biomarker for impending parenchyma damage in patients during neurocritical care. Using subdural platinum/iridium (Pt/Ir) electrodes, SD is observed as a large negative direct current (DC) shift. Besides SD, there are other causes of DC shifts that are not to be confused with SD. Here, we systematically analyzed DC artifacts in ventilated patients by observing changes in the fraction of inspired oxygen. For the same change in blood oxygenation, we found that negative and positive DC shifts can simultaneously occur at adjacent Pt/Ir electrodes. Methods Nurses and intensivists typically increase blood oxygenation by increasing the fraction of inspired oxygen at the ventilator before performing manipulations on the patient. We retrospectively identified 20 such episodes in six patients via tissue partial pressure of oxygen (ptiO2) measurements with an intracortical O2 sensor and analyzed the associated DC shifts. In vitro, we compared Pt/Ir with silver/silver chloride (Ag/AgCl) to assess DC responses to changes in pO2, pH, or 5-min square voltage pulses and investigated the effect of electrode polarization on pO2-induced DC artifacts. Results Hyperoxygenation episodes started from a ptiO2 of 37 (30–40) mmHg (median and interquartile range) reaching 71 (50–97) mmHg. During a total of 20 episodes on each of six subdural Pt/Ir electrodes in six patients, we observed 95 predominantly negative responses in six patients, 25 predominantly positive responses in four patients, and no brain activity changes. Adjacent electrodes could show positive and negative responses simultaneously. In vitro, Pt/Ir in contrast with Ag/AgCl responded to changes in either pO2 or pH with large DC shifts. In response to square voltage pulses, Pt/Ir falsely showed smaller DC shifts than Ag/AgCl, with the worst performance under anoxia. In response to pO2 increase, Pt/Ir showed DC positivity when positively polarized and DC negativity when negatively polarized. Conclusions The magnitude of pO2-induced subdural DC shifts by approximately 6 mV was similar to that of SDs, but they did not show a sequential onset at adjacent recording sites, could be either predominantly negative or positive in contrast with the always negative DC shifts of SD, and were not accompanied by brain activity depression. Opposing polarities of pO2-induced DC artifacts may result from differences in baseline electrode polarization or subdural ptiO2 inhomogeneities relative to subdermal ptiO2 at the quasi-reference.

scholarly journals A Novel Highly Durable Carbon/Silver/Silver Chloride Composite Electrode for High-Definition Transcranial Direct Current Stimulation

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1962
Author(s):  
Lingjun Li ◽  
Guangli Li ◽  
Yuliang Cao ◽  
Yvonne Yanwen Duan
Keyword(s):  
Service Life ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Silver Chloride ◽  
Cycling Performance ◽  
High Definition ◽  
Silver Silver ◽  
Sintered Ag ◽  
Silver Silver Chloride

High-definition transcranial direct current stimulation (HD-tDCS) is a promising non-invasive neuromodulation technique, which has been widely used in the clinical intervention and treatment of neurological or psychiatric disorders. Sintered Ag/AgCl electrode has become a preferred candidate for HD-tDCS, but its service life is very short, especially for long-term anodal stimulation. To address this issue, a novel highly durable conductive carbon/silver/silver chloride composite (C/Ag/AgCl) electrode was fabricated by a facile cold rolling method. The important parameters were systematically optimized, including the conductive enhancer, the particle size of Ag powder, the C:Ag:PTFE ratio, the saline concentration, and the active substance loading. The CNT/Ag/AgCl-721 electrode demonstrated excellent specific capacity and cycling performance. Both constant current anodal polarization and simulated tDCS measurement demonstrated that the service life of the CNT/Ag/AgCl-721 electrodes was 15-16 times of that of sintered Ag/AgCl electrodes. The much longer service life can be attributed to the formation of the three-dimensional interpenetrating conductive network with CNT doping, which can maintain a good conductivity and cycling performance even if excessive non-conductive AgCl is accumulated on the surface during long-term anodal stimulation. Considering their low cost, long service life, and good skin tolerance, the proposed CNT/Ag/AgCl electrodes have shown promising application prospects in HD-tDCS, especially for daily life scenarios.

In vitro evaluation of delays in the adjustment of the fraction of inspired oxygen during CPAP: effect of flow and volume

2020 ◽  
pp. fetalneonatal-2020-319058
Author(s):  
Christoph E. Schwarz ◽  
Gordon Lightbody ◽  
Ingo Müller-Hansen ◽  
Jörg Arand ◽  
Christian F. Poets ◽  
...  
Keyword(s):  
Gas Flow ◽  
Closed Loop ◽  
Volume Flow ◽  
Target Range ◽  
Equilibration Time ◽  
Ventilator Circuit ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen

BackgroundAdjusting the fraction of inspired oxygen (FiO2) delivered to preterm infants to keep their oxygen saturation within target range remains challenging. Closed-loop automated FiO2 control increases the time infants spend within the assigned target range. The delay with which FiO2 adjustments at the ventilator result in a change in the inspired gas limits the performance of both manual and automated controls.ObjectiveTo evaluate the equilibration time (Teq) between FiO2 adjustments and changes in FiO2 reaching the patient.MethodsIn vitro determination of the delay in FiO2 adjustments at the ventilator at 5 and 8 L/min of gas flow and two different humidifier/ventilator circuit volumes (840 and 432 mL).ResultsTeq values were 31, 23, 20 and 17 s for the volume–flow combinations 840 mL+5 L/min, 840 mL+8 L/min, 432 mL+5 L/min and 432 mL+8 L/min, respectively.ConclusionThe identified delay seems clinically relevant and should be taken into account during manual and automatic control of FiO2.

DIRECT CURRENT POTENTIAL AND pH OF SEVERAL VARIETIES OF SKIN NEOPLASMS

1954 ◽  
Vol 32 (1) ◽  
pp. 519-525 ◽  
Author(s):  
W. R. Inch
Keyword(s):  
Direct Current ◽  
Silver Chloride ◽  
Skin Neoplasms ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Absolute Value ◽  
Silver Silver ◽  
Silver Silver Chloride ◽  
Current Potential

A study of 36 subjects having skin neoplasms of three degrees of malignancy is described. The hydrogen ion concentration was determined using a Beckman model G pH meter with glass and calomel electrodes while d-c. potentials were measured using a d-c. vacuum tube amplifier and silver – silver chloride electrodes.The results indicate that there is no correlation between malignancy and absolute value of potential, but a correlation between malignancy and pH difference (pH neoplasm − pH normal) and between malignancy and the 'extra positivity' (absolute d-c. potential − 0.059 pH difference) does exist.

Mathematical Modeling of Carbon Monoxide Exposures from Anesthetic Breakdown

2001 ◽  
Vol 94 (3) ◽  
pp. 457-460 ◽  
Author(s):  
Harvey J. Woehlck ◽  
David Mei ◽  
Marshall B. Dunning ◽  
Franklin Ruiz
Keyword(s):  
Carbon Monoxide ◽  
Gas Flow ◽  
Pediatric Population ◽  
Production Data ◽  
Published Data ◽  
Patient Factors ◽  
Co Concentration ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen

Background Carbon monoxide (CO) is produced by reaction of isoflurane, enflurane, and desflurane in desiccated carbon dioxide absorbents. The inspiratory CO concentration depends on the dryness and identity of the absorbent and anesthetic. The adaptation of existing mathematical models to a rebreathing circuit allows identification of patient factors that predispose to more severe exposures, as identified by carboxyhemoglobin concentration. Methods From our companion study, the authors used quantitative in vitro CO production data for 60 min at 7.5% desflurane or 1.5% isoflurane at 1 l/min fresh gas flow. The carboxyhemoglobin concentration was calculated by iteratively solving the Coburn Forster Kane equation modified for a rebreathing system that incorporates the removal of CO by patient absorption. Demonstrating good fit of predicted carboxyhemoglobin concentrations to published data from animal and human exposures validated the model. Carboxyhemoglobin concentrations were predicted for exposures of various severity, patients of different sizes, hematocrit, and fraction of inspired oxygen. Results The calculated carboxyhemoglobin concentrations closely predicted the experimental results of other investigators, thereby validating the model. These equations indicate the severity of CO poisoning is inversely related to the hemoglobin quantity of a subject. Fraction of inspired oxygen had the greatest effect in patients of small size with low hematocrit values, where equilibrium and not the rate of uptake determined carboxyhemoglobin concentrations. Conclusion This model predicts that patients with low hemoglobin quantities will have more severe CO exposures based on the attainment of a higher carboxyhemoglobin concentration. This includes patients of small size (pediatric population) and patients with anemia.

scholarly journals Yeast-derived biosynthesis of silver/silver chloride nanoparticles and their antiproliferative activity against bacteria

RSC Advances ◽  
2016 ◽  
Vol 6 (12) ◽  
pp. 9893-9904 ◽  
Author(s):  
Mateus Eugenio ◽  
Nathalia Müller ◽  
Susana Frasés ◽  
Rodrigo Almeida-Paes ◽  
Luís Maurício T. R. Lima ◽  
...  
Keyword(s):  
Antiproliferative Activity ◽  
Silver Chloride ◽  
Yeast Strains ◽  
Agcl Nanoparticles ◽  
Silver Silver ◽  
Silver Silver Chloride

Here, we provided the first evidence of Ag/AgCl-nanoparticles production in yeast strains fromin vitrocultures.

scholarly journals Reexamination of Electrical Stimulation on Sarcoplasmic Reticulum Fragments In Vitro

1973 ◽  
Vol 62 (6) ◽  
pp. 773-786 ◽  
Author(s):  
H. Miyamoto ◽  
M. Kasai
Keyword(s):  
Electrical Stimulation ◽  
Sarcoplasmic Reticulum ◽  
Silver Chloride ◽  
Electrical Response ◽  
Platinum Electrodes ◽  
Irreversible Denaturation ◽  
Ca Uptake ◽  
Silver Silver ◽  
Silver Silver Chloride

The effect of direct electrical stimulation on suspensions of sarcoplasmic reticulum membrane fragments (SRF) was carefully re-examined using the method of Lee et al. (1966) J. Gen. Physiol. 49:689. Inhibition of Ca++ uptake or release by electrical stimulation was observed. When platinum electrodes were used as stimulating electrodes, the effect was dependent on the total current passed through the suspension. On the contrary, when silver-silver chloride electrodes were used, no effect was observed even if voltage and current were the same as in the case of the platinum electrodes. In addition, apparent re-uptake of Ca++ after cessation of electrical stimulation using platinum electrodes was shown to be due to a binding of Ca++ to denatured SRF which did not require an energy supply such as ATP, although such re-uptake had been taken as strong evidence of electrical response of SRF in Lee's paper. Finally, it was concluded that the effect of electrical stimulation on SRF was attributable to the irreversible denaturation of SRF due to the oxidation caused by the chlorine generated at the platinum electrode.

DIRECT CURRENT POTENTIAL AND pH OF SEVERAL VARIETIES OF SKIN NEOPLASMS

1954 ◽  
Vol 32 (5) ◽  
pp. 519-525 ◽  
Author(s):  
W. R. Inch
Keyword(s):  
Direct Current ◽  
Silver Chloride ◽  
Skin Neoplasms ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Absolute Value ◽  
Silver Silver ◽  
Silver Silver Chloride ◽  
Current Potential

A study of 36 subjects having skin neoplasms of three degrees of malignancy is described. The hydrogen ion concentration was determined using a Beckman model G pH meter with glass and calomel electrodes while d-c. potentials were measured using a d-c. vacuum tube amplifier and silver – silver chloride electrodes.The results indicate that there is no correlation between malignancy and absolute value of potential, but a correlation between malignancy and pH difference (pH neoplasm − pH normal) and between malignancy and the 'extra positivity' (absolute d-c. potential − 0.059 pH difference) does exist.

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