Faradic Stimulation

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Original Editor - Abdallah Ahmed Mohamed

Top Contributors - Abdallah Ahmed Mohamed, Kim Jackson and Aminat Abolade  

Identification

Faradic current is a short duration interrupted direct current with a pulse duration ranging from 0.1 to 1 ms with frequency of 50 to 100 Hz. Faradic current are surged to produce tetanic contraction and relaxation of muscle. treatment with faradic current usually called faradism.

Difference between farradic and galvanic current

Faradic current is a type of current with short duration interrupted direct current with a pulse duration of 0.1-1MS with a frequency 50-100Hz. This type of current is mainly used for partially or completely innervated muscle which the nerve still intact with muscle. As the innervated muscle need only a short duration to stimulate the intact nerve.When the current is applied, it stimulates the intact nerve by changing the permeability of cell membrane and varying the resting potential of the membrane. When the resting potential is exceeds the threshold level it will become excited, and the muscle supplied by the nerve will contract. The sensory stimulation of nerve will also be produced accompanied by the motor stimulation. The sensory stimulation resulting in the feeling of prickling sensation.There are few waveform types of faradic current which is also referred as pulse duration, for example, trapezoidal surging, triangular surging and saw tooth. Trapezoidal surging and triangular surging happen when the impulse increase and decrease gradually, so these two type of current is suitable for mild and moderate injury. While for saw tooth type to happen when the impulses increase gradually but suddenly fall and it is usually used for severe injury.Treatment is called farradism.

Galvanic current is an interrupted direct current with a long duration of more than 1 MS with a frequency of 30 pulses per minutes and is commonly used for denervated muscle either it is partially or completely denervated. The denervated muscle will not respond to a duration which is less than 1MS as the injured nerve needs time to respond and send impulses to the brain. When the current is applied, the nerve of the muscle close to the denervated muscle is contracted. The sensory stimulation of nerve will also be produced accompanied by the motor stimulation. The sensory stimulation resulting in the feeling of burning sensation.There are few type of pulse shape, rectangular, triangle, trapezoidal and saw tooth. The rectangular type is the current turn on and off intensity abruptly; triangular type is it slow rise and slow fall of intensity; trapezoidal type is it raise slowly, plateau’s and then falls slowly. Saw tooth is the gradual rise of current and abruptly falls.Treatment is called Galvanism.

Physiological Effect

The physiological effects of faradic current and galvanic current is almost the same, such as stimulation of sensory nerves and motor nerves. Both of the current will causes a reflex vasodilation of the cutaneous blood vessels, so there will be a slightly redness of the skin or erythema. Next, stimulation of motor nerves. Faradic current stimulates the motor nerves and causes the muscle supplied by the nerve to contract. The contraction is called as tetanic contraction. If this contraction is maintained for a long period, it may cause the muscle to become fatigued. So, to prevent this to happen, the current is surge to allow relaxation of muscle. So that, the muscle will contract gradually increase and decrease in the strength of muscle, which is similar to the voluntary muscle contraction. For galvanic current, it will stimulate the muscle to produce muscle twitch followed by immediate relaxation due to the repeated stimuli.

The electrical stimulation caused the muscle contraction which can help in increasing the metabolism and the removal of waste of products. The contraction and relaxation of the muscle exerts a pumping action on the blood vessels and increased the metabolism by pumping more blood supply and nutrients to muscle thus increase demand of oxygen and nutrients to muscle. Other than that, the pumping action will also occur on veins and lymphatic vessels within the muscle and around it, thus increase the removal of waste products. Then, the chemical effect of faradic current. Chemicals effects produced at the electrodes due to passing the direct current through electrolyte, which is introduce medicine into body through electricity, such as iontophoresis. But it do not allow considerable amount of collection of chemicals under the electrode. We have to examined the skin after every stimulation to rule out any chemical burn or erythema.

Then is the therapeutic effect of faradic current. First of all, is facilitation of muscle contraction. Electrical stimulation will help muscle to contract voluntary when the muscle contraction is inhibit by pain or recent injury. For example, rheumatoid arthritis, post fracture immobilization, etc. Next, is re-educate of muscle action. Muscle unable to contract may because of the prolonged disuse of the particular muscle. Faradic current can help to produce muscle contraction and enhance the sense of movement. When we observe a movement our brain will appreciate the movement and not muscle action. So, to enhance the rehabilitation of the patient, the patient should practice the movement actively along with observation which would improve the movement pattern effectively. Also, after the tendon transplantation or any other reconstructive procedures a muscle may need to perform the action that is different from it’s previous action. But the muscle will not able to know what is the action of the previous muscle. So, patient need to observe the new action and try do it actively along with the electrical stimulation. Then, it can help to improved venous and lymphatic drainage as electrical stimulation can produce pumping action which can increase the venous and lymphatic return. It can be more effective when applying under the pressure. It is good in reduced edema. Lastly, it can help in prevention and loosening of adhesion. The formation of adhesion can be stretched and loosen by muscle contraction, for example, the scar tissue binding to muscle and tendons.

Next is the therapeutic effect of galvanic current. The electrical stimulation can help in minimize the extent of muscle atrophy thru the period while the nerve is degenerating. Actually, electrical stimulation has no effect on the rate of nerve regeneration or muscle reinnervation. It is just provided a platform for the degenerative nerve. But if the reinnervation does not occur within 2 years, it means that the contractile element of muscle may have already replaced by the fibrous connective tissue and recovery of the muscle is not possible. In addition, Galvanic current can also limit the edema and venous stasis and result in delaying the muscle fiber fibrosis and degeneration by pumping action.

Indication

1. facilitation of muscle contraction when inhibited by Pain
2. Muscle re-education:muscle contraction is needed to restore the sense of movement.In cases of flat foot or in muscle transplantation.the brain appreciate movement not muscle actions so crrent should be applied to restore normal movement.
3. training of new muscle action
4. Improved venous and lymphatic drainage as edema and gravitational ulcer by pumping action of muscle contraction and relaxation.
5. Prevention and loosening of adhesion
6. Painful knee syndrome.

Contraindication

1. certain dermatological condition as psoriasis,tin ea and eczema.
2. Infection
3. Inflammation
4. Thrombosis
5. Loss of sensation
6. Cancer
7. Cardiac pacemakers

Practical Guidelines

• The patient is positioned so that the part to be treated is comfortably supported with the muscles to be stimulated in a shortened position although this may be modified with movement produced e.g,slight knee flexion allowing quadriceps stimulation to cause extension.
• The skin surface must be examined for any cuts or abrasions, treatment area should be washed to remove sebum and epithelial cells using hot water to lower resistance.
• Size of active electrode is chosen to considering size of treatment area.
• The electrode should be smaller than the pad to prevent the edge of the electrode being bent down on the skin.
• the pads should be soaked in warm tap water,saline or sodium bicarbonate solution before applied to the skin.
• Fixation is achieved with rubber strap or by body weight.
• explain to the patient sensation.
• when muscle is to be stimulated the active electrode is placed over motor point and small current is applied.The current may need to be increased and then decreased as the motor point found and good contraction obtain with less currnt.
• when muscle group is to be stimulated the active electrode placed at end of muscle group so current spread through the whole group.