faradic current-1.pptx...................

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1. FARADIC CURRENTS K. GEETHA REDDY ASST. PROF

2. Original Form of Faradic Current Faradic current is an early form of stimulating current used for muscle stimulation. Characteristics: Type: Biphasic uneven alternating current. Pulse Duration: 1 ms. Frequency: 50 Hz Waveform Structure: Initial phase: Short intensity, large pulse duration. Followed by: Large intensity, short pulse duration. Equipment Used: Generated using a faradic coil or induction coil.

3. Faradic coils have now been replaced by electronic stimulators which almost have the same physiological effect but differs in the waveform.

4. TYPES Therapeutic Faradic current can be classified into 2 types: Plain: This includes single stimulation with no interruption i.e. it is continuous current. Surged Faradic: It is interrupted therapeutic current and it is also called "Modified Faradic Current". Usually the impulses, which rise and fall gradually, are better than pain because they produce less sensory irritation.

5. EFFECT OF FREQUENCY ON STIMULATION When single stimulus is given to a muscle, there is one complete contraction followed by complete relaxation. This is called 'Twitch or Contraction'. If the frequency is upto 20 Hz, there is a good time to relax. As the frequency increases beyond 20 Hz, the relaxation time decreases. When the frequency is reached upto 80 Hz, there is no time for relaxation and the current physiologically flows continuously and it is called 'Tetanic current '.

6. FARADIC TYPE CURRENT/MODIFIED FARADIC CURRENT Faradic type current is a short-duration interrupted direct current. Pulse Duration: Ranges from 0.1 to 1 millisecond. Frequency: Operates at 50-100 Hz. Used to produce near-normal tetanic-like contraction and relaxation of muscles. The current is surged to gradually increase and decrease impulse intensity, with each peak value exceeding the previous one. Surging is employed to overcome adaptation/accommodation of the muscles to the current. When the current flows at a constant level, accommodation of the nerve fibers occurs. This adaptation leads to a potential difference where the current no longer affects the excitability of the nerve fibers.

7. In the original faradic coils, the current was surged by hand but in modern stimulators an electronic device is used. The circuit can be modified to give surges of various durations, frequencies and waveforms. Various forms of surge are available, such as trapezoidal, triangular and saw-tooth impulses, and that most suitable for each patient must be selected

8. PARAMETERS OF FARADIC TYPE CURRENT Waveform Shape: Rectangular pulses are generally more comfortable than triangular pulses, based on subject preference. Pulse Duration: Ranges from 0.1 to 1 ms; the optimal duration is selected for comfortable near-normal muscle contraction. Surging Requirement: Faradic type current is always surged for therapeutic applications. Interphase Intervals/Pause Duration: The pause duration between pulses should be at least 2 to 3 times longer than the pulse duration to allow muscle recovery. Frequency: Operates within a range of 50-100 Hz. Intensity: Should be maximal tolerable and based on the patient's comfort level. Duty Cycle: Commonly set to 2 seconds on and 10 seconds off, or 5 seconds on and 15 seconds off.

9. Treatment Duration: Recommended treatment time is 15 minutes per session, 3 to 7 times per week. PHYSIOLOGICAL EFFECTS OF FARADIC TYPE CURRENT Effect on Sensory Nerve . Stimulation of motor nerve Effect on Blood Vessels. Effect on innervated Muscle. Effects on Denervated Muscle. Effects on Muscle Contraction.

10. Effect on Sensory Nerves: Faradic current : When applying a faradic type current mild prickling sensation is felt due to stimulation of sensory nerves. This stimulation is not very marked because the stimuli are of fairly short-duration. Interrupted Galvanic Current : This also stimulates sensory nerves and results in stabbing or burning sensation. This stimulation is very marked because the stimuli are long duration impulses. When sensory nerve is stimulated either by faradic or interrupted galvanic current, it also produces reflex vasodilatation of superficial blood vessels. So slight erythema is seen , this vasodilatation is limited up to superficial area only.

11. Stimulation of motor nerves by faradic current : Faradic current stimulates motor nerves and muscles if the intensity is sufficient. It causes tetanic contractions due to stimuli repeated 50 times per second. Prolonged contractions can lead to muscle fatigue. To prevent fatigue, the current is surged to allow for muscle relaxation. The surging current results in contractions that gradually increase and decrease in strength, mimicking voluntary contractions. By Galvanic Current: Interrupted galvanic current also stimulates motor nerves, leading to muscle contraction. This results in muscle twitches followed by immediate relaxation. The effects of galvanic current on muscles are generally less beneficial compared to faradic current.

12. Effect on Blood Vessels: Causes reflex vasodilation of superficial blood vessels. Leads to erythema (redness) of the skin. Reflex vasodilation increases capillary blood flow, reducing skin resistance and facilitating smoother current flow. Effect on Innervated Muscle: Produces a tetanic-like contraction followed by immediate relaxation when stimulated at frequencies of 50 Hz or more. Prolonged stimulation can lead to muscle fatigue; thus, the current is surged to allow relaxation similar to voluntary contractions. Effects on Denervated Muscle: Faradic current has no satisfactory effect on denervated muscles.

13. Requires intact nerve supply, as the intensity needed to depolarize the muscle membrane is uncomfortable without nerve function. Effects on Muscle Contraction: Mimics normal voluntary muscle contraction. Results in a temporary increase in metabolism and blood supply to the muscle . Chemical effects following stimulation : Chemical effects are produced at the electrodes due to passing of direct current through the electrolyte. It results in formation and accumulation of chemicals at the electrode site resulting in chemical or electrolytic burn. The risk is comparatively less with an intermittent current than with a direct current. When an alternative current is used, chemicals formed during one phase are neutralized during the next phase as the ions move one way during one phase and in reverse direction during the other phase. In a condition, where the two phases are equal, chemicals formed during one phase are neutralized during the next phase.

14. Therapeutic Effects of Faradic Type Current Strength Training: - Facilitates muscle contractions by depolarizing motor nerves, resulting in tetanic muscle contractions. Increases strength, particularly when voluntary contraction is impaired due to pain or injury. Examples: - Stimulation of quadriceps in knee joint injuries. - Targeted stimulation following compression of a motor nerve. 2. Re-education of Muscle Activity: - Used to re-educate muscles post-surgery when patients temporarily lose contraction ability. Examples: - Quadriceps weakness after knee surgery. Training muscles to perform new actions after tendon transfers or nerve grafts.

15. Oedema Control: Intermittent muscle contractions mechanically compress venous and lymphatic vessels, enhancing centripetal flow. Effective in reducing interstitial pressure for various types of oedema . Maintenance of Range of Motion: Electrical stimulation of antagonistic muscles promotes movement in stiff joints. Example: Stimulating lateral trunk muscles in scoliosis to increase range of motion. 4. Stress Incontinence: - Assists in re-educating detrusor muscles, particularly in early prolapse cases and stress incontinence. 5. Temporary Control of Spasticity: Stimulating antagonistic muscles temporarily inhibits spasticity through reciprocal inhibition.

16. Direct stimulation of spastic muscles induces fatigue, providing temporary relief from spasticity through autogenic inhibition. INDICATIONS OF FARADIC TYPE CURRENT The most significant use of faradic type current in electrotherapy is the stimulation of innervated muscle. Deltoid and Quadriceps inhibition. and * Flat foot. Compression of peripheral nerves ( Neuropraxia ). Post traumatic disuse atrophy of skeletal muscle. and * Lymph oedema . Reduced range of motion of joint. Stress incontinence/weakness of pelvic floor muscles following delivery. Spasticity following stroke, spinal cord injuries.

17. CONTRAINDICATIONS OF FARADIC TYPE CURRENT No sensation/marked loss of skin sensation. Metastatic tumours . Cardiac pacemaker. Deep vein thrombosis (DVT). Haemorrhage /active bleeding in the area to be treated. Active infection/active tuberculosis. Over superficial metal implants. Where active motion is contraindicated (e.g., fusion, non-union fracture, or recently sutured nerves or tendons). Unconscious and uncooperative patient. Epilepsy patient. Mentally retarded patients. Open wounds. Acute inflammation.

18. PRECAUTIONS Avoid anesthetic skin during treatment whenever possible. If stimulation must be given over anesthetic skin, use lower intensities and monitor the skin carefully. 2. Avoid open wounds in the treatment area. 3. Avoid areas of extreme edema. The very conductive fluid will prevent the current from reaching the target tissue.