Write a note on Faradic current? Explain its physiological effects and indications.

 FARADIC CURRENT:

A Faradic current is a short-duration interrupted direct current with a pulse duration of 0.1-1 ms and a frequency of 50-100 Hz.

Modified Faradic Currents:

Modified faradic currents include the surging of current. they produce a near-normal tetanic like contractions and relaxation. The current is surged, so that intensity of impulses increases gradually. The circuit can b modified by giving surges of different durations and frequencies.

Various forms of surges may b available, which are trapezoidal, triangular and saw-tooth impulses.

Physiological Effects :

The physiological effects of faradic currents are as follows:

1. Stimulation Of Sensory nerves:

                                                         When a current of faradic type is applied to the body, a mild prickling sensation is felt. This is due to the stimulation of sensory nerves. The sensory stimulation causes a reflex vasodilation of the superficial blood vessels, thats why slight reddening of skin occurs.

2. Stimulation Of Motor nerves:

                                                             A faradic type current stimulates the motor nerves and if the current is of sufficient intensity, causes tetanic contraction of the muscles.  When the current is surged, the contraction gradually increases or decreases in strength.

3. Stimulation Of Denervated Muscle:

                                                                        The faradic type current is not satisfactory for the stimulation of denervated muscles because faradic current produces a contraction of 1 ms which is too great to be tolerable for denervated muscle.

4. Chemical Effects Of Faradic Current:

                                                                            When a direct current is passed through an electrolyte, chemical changes take place at the electrode. If the chemicals formed come in contact with the tissues there is a danger of electrolyte burns. 

When the current is alternating,  the ions move one way during one phase of current and in the reverse direction during the other phase. And if the two phases are equal the chemicals formed during one phase are neutralized during the nxt phase.

Indications Of Faradic Current:

There are following indications of faradic current:

1. Facilitation Of Muscle Contraction:

• Excitation of the small efferent fibers, which causes the contraction of intrafusal fibres.
• Stretching of the muscle spindle which stimulates the primary nerve endings causing an excitation of the extrafusal muscle fibres.
• Inhibition of the anterior horn cells supplying the antagonistic muscle group.

2. Re-Education Of Muscle Action:

Inability to contract a muscle voluntarily may be the result of prolonged disuse. In this condition, faradic stimulation may b used to produce contractions and so help to restore the sense of movement. 

3. Training A New Muscle Action:

After tendon transplantation, a muscle may be required to perform a different action which is carried out previously. The muscle is stimulated with the faradic current so that is movement is carried out.

4.Neuropraxia Of A Motor Nerve:

In it, impulses from the brain are unable to pass the site of lesion to reach the muscles supplied by the affected nerve. its voluntary power is reduced or lost. That's why, a faradic current is applied to stimulate the muscles.

5. Improved Venous And Lymphatic Drainage:

Increased venous and lymphatic return is brought about by the pumping action of alternate muscle contraction and relaxation and of joint movement on the veins and lymphatics. The treatment is more effective if the current is applied by the method called Faradism under pressure.

References:

Claytons's Electrotherapy

( Angela Forster, Nigel Palastanga )

About Author:

Tayyba Saleem ( PT )

Doctor Of Physical Therapy.