A faradic current is a short duration interrupted direct current with a pulse duration of 0.1-1 ms and frequency of 50-100 Hz. It produces a biphasic, asymmetrical and spiked waveform. Faradic currents are used to produce near normal tetanic-like muscle contractions and relaxations. When applied to nerves and muscles, it causes sensory stimulation, muscle contraction, reduced swelling and pain, and increased metabolism. Faradic current is indicated for muscle reeducation, maintaining range of motion, loosening adhesions, and replacing orthosis. It involves placing electrodes on muscles or nerve trunks and gradually increasing and decreasing intensity to cause contraction and relaxation.
2. INTRODUCTION:
A faradic type current is a short duration interrupted
direct current with a
pulse duration of 0.1-1 ms and
frequency of 50-100 Hz.
3. WAVEFORMS OF FARADIC
CURRENT:
Waveform- Biphasic, asymmetrical, unbalanced,
spiked
Positive portion – Short duration, high amplitude and
spiked
Negative portion – Long duration, low amplitude and
curved
4. MODIFIED FARADIC CURRENTS
Faradic currents are always surged for treatment
purposes to produce a near normal tetanic-like
contraction and relaxation of muscle.
Current surging means the gradual increase and
decrease of the peak intensity.
5. PHYSIOLOGICAL EFFECTS OF
FARADIC CURRENT:
STIMULATION OF SENSORY NERVES:
1. When a faradic current is applied to the body, a mild
prickling sensation is experienced.
2. The sensory stimulation causes a reflex vasodilation
of the superficial blood vessels and is confined to the
superficial tissues.
6. STIMULATION OF MOTOR NERVES:
It occurs if the current is of a sufficient intensity, causing
contraction of the muscles supplied by the nerve distal to
the point of stimulus.
A suitable faradic current applied to the muscle elicits a
contraction of the muscle itself and may also spread to the
neighboring muscles.
The character of the response varies with the nature and
strength of the stimulus employed and the normal or
pathological state of muscle and nerve.
The contraction is tetanic in type because the stimulus is
repeated 50 times or more / sec.
7. If this type is maintained for more than a short time,
muscle fatigue occurs. So, the current is commonly
surged to allow for muscle relaxation i.e. “when the
current is surged, the contraction gradually increases
and decreases in strength in a manner similar to
voluntary contraction”.
Stimulation of the nerve is due to producing a change
in the semi-permeability of the cell membrane: This is
achieved by altering the resting membrane potential.
When it reaches a critical excitatory level, the muscle
supplied by this nerve is activated to contract.
8. Reduction of swelling and pain:
1. It occurs due to alteration of the permeability of the
cell membrane, leading to acceleration of fluid
movement in the swollen tissue and arterial
dilatation.
2. Moreover, it leads to increase metabolism and get
red of waste products.
9. CHEMICAL EFFECTS:
1) The ions move one way during one phase of the
current and in the reverse direction during the other
phase of the current if it is alternating.
2) If the two phases are equal, the chemicals formed
during one phase are neutralized during the next
phase. In faradic current, chemical formation should
not be great enough to give rise to a serious danger of
burns because of the short duration of impulses.
10. INDICATIONS :
FACILITATION OF MUSCLE CONTRACTION:
When a patient is unable to produce a muscle
contraction,electrical stimulation may be of use in
assisting voluntary contraction.
MUSCLE REEDUCATION:
Muscle contraction is needed to restore the sense of
movement in cases of prolonged disuse or incorrect
use; and in muscle transplantation. The brain
appreciates movement not muscle actions, so the
current should be applied to cause the movement that
the patient is unable to perform voluntarily.
11. MAINTAINING ROM:
Electrical stimulation of faradic current helps to
stretch the shortened tissue and increases ROM.
LOOSENING AND PREVENTION OF ADHESION:
• Adhesion is formed where there is no muscle
contraction.
• Electrical stimulation by faradic current causes
muscle contraction which loosen and stretches the
adhesion.
12. IMPROVEMENT IN VENOUS AND LYMPHATIC
DRAINAGE
NEUROPRAXIA OF MOTOR NERVE
FOR REPLACING ORTHOSIS:
low stimulation frequency used to enhance the
function of a paralyzed muscles thus eliminating the
need for a splint or brace or orthosis.
13. CONTRAINDICATIONS:
Skin lesions: The current collects at that point causing
pain.
Certain dermatological conditions: Such as psoriasis,
tinea and eczema.
Acute infections and inflammations.
Thrombosis.
Loss of sensation.
Cancer.
Cardiac pacemakers.
Superficial metals.
14. FARADISM FOR STIMULATION OF
DENERVATED MUSCLE:
Equipments Required:
Low frequency electronic stimulator
2 leads [1cathode & 1anode]
2 suitably sized carbon/metal electrode
Aqueous gel, a sand bag
• Bandage, straps, micropore or adhesive tape
2 small basin of warm water
Towels, soap
Insulating cream [petroleum jelly, vaseline]
15. PROCEDURE FOR STIMULATION:
Position the patient comfortably in a relaxed position
Support the muscle to be stimulated in pain- free
position with area to be treated adequately exposed
In case of supine lying knees should be flexed by
keeping the pillows or towels under the knee
Examine the area to be treated; note any cuts, skin
lesions and inflammations. Check that there is no
contraindication to treatment like sensation
16. PROCEDURE FOR STIMULATION:
Equipment should be tested prior to treatment by placing
the electrodes over the palm & increasing intensity to
check whether equipment is working properly.
Explain the procedure properly to patient that there will be
pricking sensation on area to be treated & there is no need
to panic & if intensity will be high he/she must tell.
Clean the electrodes with soap water to avoid any chemical
on electrode & also clean the area to be treated to remove
any grease on skin which helps in better penetration by
reducing the skin impedence.
17. PROCEDURE FOR STIMULATION:
Place the active electrode on muscle & inactive
electrode on nerve trunk if for group action. If it is for
stimulating individual muscle we will use pen
electrode.
Connect the electrodes properly to skin with the help
of tape/strap.
Explain the patient that during the procedure he/ she
should not move the limb suddenly or do not touch
the equipment.
19. GROUP MUSCLE STIMULATION:
Stimulation which makes all the muscles of a group
work together
Satisfactory method of re-educating the action of
muscles which normally work as a group, such as
quadriceps, the small muscles of the foot, and muscles
of pelvic floor
20. MOTOR POINTS STIMULATION:
This method has an advantage that each muscle
performs its own individual action & that the optimum
contraction of each can be obtained
Selected when training a new muscle action or when
isolation of one muscle is indicated; e.g. vastus
medialis may be stimulated to overcome a quadriceps
lag, or abductor hallucis for muscle weakness.