Transcutaneous Electrical Nerve Stimulation (TENS)

Parameterization of electrotherapy interventions in physiotherapy for pelvic floor dysfunctions: a systematic review

OBJECTIVE

To determine which parameters of the currents used with electrotherapy in pelvic floor dysfunctions are more appropriate for the proposed objectives regarding the relief of the symptomatology of certain clinical conditions.

MATERIAL AND METHODS

A systematic review was performed in CENTRAL, PubMed/MEDLINE and PEDro databases. The risk of bias and methodological quality in the included studies was assessed using the ROBINS-I, JADAD and PEDro scales, respectively.

STUDY SELECTION

The review included randomized controlled trials, with adult patients aged 18 years or older, that incorporated the use of electrical currents in the conservative treatment of pelvic floor dysfunctions.

RESULTS

After meeting the evaluation and inclusion-exclusion criteria, 14 articles were selected following the PRISMA guidelines.

CONCLUSIONS

There is a certain lack of homogeneity in the choice of the parameters of the electrotherapy currents used in pelvic floor dysfunctions. There is evidence supporting the effectiveness of neuromuscular electrostimulation in pelvic floor muscle re-education due to its functional improvements, as well as the application of analgesic electrical current therapy such as TENS for the modulation of clinical conditions involving pain.

Volume conductor model of transcutaneous electrical stimulation with kilohertz signals

OBJECTIVE

Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequencies beyond those typically used in neural stimulation.

APPROACH

We implemented a multilayer volume conductor model including dispersion and capacitive effects, coupled to a cable model of a nerve fiber. We simulated voltage- and current-controlled transcutaneous stimulation, and quantified the effects of frequency on the distribution of potentials and fiber excitation. We also quantified the effects of a novel transdermal amplitude modulated signal (TAMS) consisting of a non-zero offset sinusoidal carrier modulated by a square-pulse train.

MAIN RESULTS

The model revealed that high-frequency signals generated larger potentials at depth than did low frequencies, but this did not translate into lower stimulation thresholds. Both TAMS and conventional rectangular pulses activated more superficial fibers in addition to the deeper, target fibers, and at no frequency did we observe an inversion of the strength-distance relationship. Current regulated stimulation was more strongly influenced by fiber depth, whereas voltage regulated stimulation was more strongly influenced by skin thickness. Finally, our model reproduced the threshold-frequency relationship of experimentally measured motor thresholds.

SIGNIFICANCE

The model may be used for prediction of motor thresholds in TES, and contributes to the understanding of high-frequency TES.