Health

Electrostimulation for pain relief

El_alivio_del_dolor_con_la_electroestimulacion

In musculoskeletal or neuromuscular pathologies, one of the main problems which arise in and during kinaesthetic therapy is pain. What techniques can we use to produce analgesic effects in the rehabilitation process of these pathologies?

The physiotherapist uses physical agents to intervene the body with healing and analgesic purposes. Some consider that these are empirical, and others consider them a simple placebo. However, the increase of scientific publications has led to a rise of the knowledge of the effectiveness of certain physiotherapeutic agents in relation to pain.

The studies on in-vitro axonal stimulation suggests that the excitability of the nerve fibers, and consequently the activation of endogenous analgesic mechanisms, depend on the characteristics of the stimulation pattern.

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How do we deal with the pain of an injury?

Within this range we find the transcutaneous electrical nerve stimulation (TENS), which is one of the four pillars in pain treatment. Schematically we can say that noxious stimulation is the cause of a series of chemical and electrical processes, known as: transduction, transmission, modulation and perception.

Currently, there is a consensus that the receiver cannot be considered as a static structure, its function is modulated both through a chemical and a mechanical way, as nervous. The concept of modulation and plasticity affects the nervous system, which explains the different behaviors, either under experimental conditions or under pathological conditions.

What fibers can be found in this process?

There are three main groups of nerve fibers: A, B and C. Group A comprises all somatic nerve fibers and a part of the visceral nerves. Within them, and according to its conduction velocity, there are four groups: alpha, beta, gamma and delta. Group B comprises myelinated preganglionic fibers of the vegetative system. The Group C includes all afferent fibers not myelinated and postganglionic sympathetic fibers. A characteristic of nerve fibers is the conduction velocity and its perception threshold, so that fast conduction velocity axons are excited more quickly than the slower ones. (Table 1)

 

Table 1: Nerve fibers

A-beta FIBERS

A-delta FIBERS

C FIBERS

Myelinated

Slightly myelinated

Unmyelinated

Caliber: 6 to 12 microns

Caliber: 1 to 6 microns

Caliber: 0.2 to 1 micron

Conduction velocity 50-70 m/sg.

Conduction velocity: 20-25 m/sg.

Conduction velocity: 1-2 m/sg.

Discriminative sensibility (epicritic and kinesthetic)

They transmit well localized pain

They transmit the poorly localized pain

 

A-beta fibers have a faster conduction velocity than C fibers, so applying a stimulus on a painful area, they can postsynaptically block the terminations of the C fibers and the projection neurons, inhibiting the painful stimulus.

Transcutaneous electrical stimulation is based on the action that the electrical impulses produced by a generator of alternating current, through the application of two or four electrodes. In this way we can inhibit the painful stimulus and increase the production of natural analgesic substances (beta-endorphins). These impulses have different morphology, intensity, width and frequency.

The reaction mechanism of the nervous system to the pain responds to the law of all or nothing. Therefore, what is really important is that the applied frequency range is able to override the pain signals. Therefore, the regulation of the frequency is made by bands, which facilitates its application.

The combination of the parameters of the generator, abovementioned, allows several types of stimulation: stimulation of high frequency (conventional) (I); stimulation of low frequency (acupunturalike) (II); brief and intense stimulation (III); modulated stimulation (IV); intermittent stimulation (burst) (V). (Table 2)

 

Table 2: Types of electrical stimulation characeristics.

Type of stimulation

I

II

III

IV

V

Frequency

80 Hz

2 Hz

130 Hz

40-80-130 Hz

80-2 Hz

Intensity

Until the paresthesia

Muscular fibrillation

The most tolerable

Variable paresthesia

Variable rhythmicity

Pulse width

75 micro-sg.

200 m-sg

200 m-sg

Variable

Variable in groups

Analgesia beginning

Quick

Slow

Intermediate

Variable

Intermediate

Analgesia duration

Short

Long

Short

Long

Long

Mechanism

Impulse block

Release of endorphins

Release of endorphins

Imp. block

Rel.endorph.

Release of endorphins

Stimulation time

60 minutes

4 times/day

20-30 min.

3 times/day

5-10 min.

3 times/day

10 minutes

3 times/day

15 minutes

3 times/day

In pain

Severe

Chronic

Chronic

Severe

Chronic

Chronic

Severe

Chronic

 

 

Therapies to relieve pain with an electro-stimulation device

Generally, the placement of the electrodes is variable, they usually are placed so that the stimulation is perceived in the painful area (on the dermatome, the myotome, or the route of the related nerve, as well as on the trigger and motor points).

The variability of currents that the i-motion electrical stimulation device delivers generates ease and innovation to make this kind of therapies, because there is a total management by the therapist of the different programs that it offers. It provides the freedom to modify each parameter, allowing you to manipulate the applied frequency so this can cancel the pain trigger mechanism.

In addition, with Biojacket i-motion can cover one larger surface, applied to muscle groups, including comprehensive active stimulation combined with the action of the movement of the stimulation impulse (according to the type of power each one needs) In this way, it would increase its pain effectiveness as it combines stretching and relaxation exercises. Electro-stimulation pain relief is a technique increasingly used by physiotherapists.

This information is important to manage it as therapists, since it will determine the correct use of electrical stimulation. As we saw earlier, it is very diverse and allows you to choose the type of current that it will be used according to the objectives of each user or patient.

 

Bibliography:

  1. Plaja J. Analgesia por medios físicos. Madrid: McGraw-Hill/Interamericana; 2003, p. 238-68.
  2. Johnson M., Martinson M. Efficacy of electrical nerve stimulation for chronic musculoskeletal pain: a meta-analysis of randomized controlled trials. 2007; 130:157-65.
  3. Walsh D.M., Howe T.E., Johnson M.I., Sluka K.A. Transcutaneous electrical nerve stimulation for acute pain. Cochrane Database Syst Rev. 2009; 2:CD006142.
  4. DeSantana J.M., Santana-Filho V.J., Guerra D.R., Sluka K.A., Gurgel R.Q., da Silva Jr. Hypoalgesic effect of the transcutaneous electrical nerve stimulation following inguinal herniorrhaphy: a randomized, controlled trial. J Pain. 2008; 9:623-
  5. Guevara-López U, Covarrubias-Gómez A, Rodríguez-Cabrera R et al. – Parámetros de práctica para el manejo del dolor en México. Cir Ciruj, 2007; 75:385-407.