A re-evaluation of modelling of the current flow between electrodes: consideration of blood flow and wounds

Universal Recommendations on Planning and Performing the Auditory Brainstem Responses (ABR) with a Focus on Mice and Rats

Translational audiology research aims to transfer basic research findings into practical clinical applications. While animal studies provide essential knowledge for translational research, there is an urgent need to improve the reproducibility of data derived from these studies. Sources of variability in animal research can be grouped into three areas: animal, equipment, and experimental. To increase standardization in animal research, we developed universal recommendations for designing and conducting studies using a standard audiological method: auditory brainstem response (ABR). The recommendations are domain-specific and are intended to guide the reader through the issues that are important when applying for ABR approval, preparing for, and conducting ABR experiments. Better experimental standardization, which is the goal of these guidelines, is expected to improve the understanding and interpretation of results, reduce the number of animals used in preclinical studies, and improve the translation of knowledge to the clinic.

Reporting Data on Auditory Brainstem Responses (ABR) in Rats: Recommendations Based on Review of Experimental Protocols and Literature

Research in hearing science is accelerating, and a wealth of data concerning auditory brainstem responses (ABR) in various animal models is published in peer-reviewed journals every year. Recently, we reviewed studies using ABR measurements in tinnitus rat models. We found significant discrepancies in the outcomes of these studies, some due to different research approaches and others due to different methodologies. Thus, the present work aimed to collect comprehensive information on all factors influencing ABR recordings in rats and compile recommendations on ABR data reporting. A questionnaire with queries about animal husbandry, transfer, handling, and the exact test conditions before, during, and after ABR recordings was sent to 125 researchers who published the relevant studies between 2015 and 2021. Eighteen researchers provided detailed answers on factors related to ABR measurements. Based on the analysis of the returned questionnaires, we identified three domains reflecting animal-, equipment-, and experiment-dependent factors that might influence the ABR outcome, thus requiring reporting in published research. The analysis of survey results led to the compilation of recommendations for reporting ABR outcomes supported by a literature review. Following these recommendations should facilitate comparative and meta-analyses of ABR results provided by various research groups.

A new electrode design to improve outcomes in the treatment of chronic non-healing wounds in diabetes

BACKGROUND

Chronic wounds are life-threatening in people with diabetes. Some studies show that electrical stimulation (ES) can help wounds heal, while others do not. But, ES is usually applied using a two-electrode system, where current distribution is greatest in the center line between the electrodes. In the present study, a three-electrode system (three-channel ES) was developed. Current dispersion on the skin and in the quadriceps muscle was compared between the conventional two-electrode and three-electrode systems in controls and tested for its ability to heal chronic wounds in people with diabetes.

METHODS

In controls, current was delivered via a biphasic sine wave at a frequency of 30 Hz and pulse width of 100 microseconds. Stimulation electrodes 5 cm x 5 cm and 5 cm x 10 cm were placed at 10 cm and 15 cm separation distances above the quadriceps muscle. Skin currents were measured using five pairs of surface electrodes positioned in five separate locations on the skin. Muscle currents were measured using three pairs of needle electrodes positioned in three different locations in the muscle belly. In chronic wounds in eight subjects with diabetes, stimulation was applied for 1 month, and healing and blood flow were measured.

RESULTS

Current during three-channel ES was dispersed more evenly and more deeply than with conventional two-channel ES (P < 0.05). In wounds, there was almost complete healing in 1 month, and current was uniform in the wound.

CONCLUSIONS

Three-channel ES is more effective than two-channel ES in terms of better current dispersion across the skin and penetration into tissue and will probably be better for wound healing.

Effects of a 2-, 3- and 4-electrode stimulator design on current dispersion on the surface and into the limb during electrical stimulation in controls and patients with wounds

Electrical stimulation is a widely used modality in the field of physical therapy and exercise physiology. The most common method for the application of electrical stimulation is a two-electrode system where one electrode is the source and the other is a reference. However, recent studies report that a more effective delivery system can be achieved if more than two electrodes are used. In the present investigation, the circuitry to deliver electrical stimulation through a 2-, 3- or 4-electrode delivery system was designed. The system was evaluated by its ability to deliver current on the surface of the skin as well as deep into the quadriceps muscle in six control subjects and in and around wounds in six other subjects. The results of the experiments showed that much better depth of penetration was achieved in a 4-electrode system (one electrode was on the opposite side of the limb and three electrodes were on top of the limb) than in either a 2- or a 3-electrode delivery system. In non-wounded skin, given the same current from the stimulator, the current in the quadriceps muscle was found to be double with a 4-electrode versus a 2-electrode system. In wounds, this same finding was seen. Here, blood flow, an indicator of the effectiveness of electrical stimulation in wounds, was three times higher if a multi-channel stimulator was used versus a 2-channel stimulator. Thus a multi-channel electrical stimulation system is more effective than a 2-electrode system.

Estimation of the distribution of intramuscular current during electrical stimulation of the quadriceps muscle

Electrical stimulation is commonly used for strengthening muscle but little evidence exists as to the optimal electrode size, waveform, or frequency to apply. Three male and three female subjects (22-40 years old) were examined during electrical stimulation of the quadriceps muscle. Two self adhesive electrode sizes were examined, 2 cm x 2 cm and 2 cm x 4 cm. Electrical stimulation was applied with square and sine waveforms, currents of 5, 10 and 15 mA, and pulse widths of 100-500 micros above the quadriceps muscle. Frequencies of stimulation were 20, 30, and 50 Hz. Current on the skin above the quadriceps muscle was measured with surface electrodes at five positions and at three positions with needle electrodes in the same muscle. Altering pulse width in the range of 100-500 micros, the frequency over a range of 20-50 Hz, or current from 5 to 15 mA had no effect on current dispersion either in the skin or within muscle. In contrast, the distance separating the electrodes caused large changes in current dispersion on the skin or into muscle. The most significant finding in the present investigation was that, while on the surface of the skin current dispersion was not different between sine and square wave stimulation, significantly more current was transferred deep in the muscle with sine versus square wave stimulation. The use of sine wave stimulation with electrode separation distances of less then 15 cm is recommended for electrical stimulation with a sine wave to achieve deep muscle stimulation.