faradic currents..pptx

8/11/2019 Faradic currents..pptx

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4 September 2014 BPHTI PTH 3201(Rev) 1


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4 September 2014 BPHTI PTH 3201(Rev)

Learning Objectives:

The lecture aims to brief students about the

following:

Nature of faradic currents

Therapeutic & Physiological effects of

faradic currents

Techniques of application

Clinical applications of faradic currents.

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Learning Outcomes:

Successful student therapist will be able to

explain about the following:1. Explain about accommodation

2. Explain about the nature of faradic currents

3. Explain about the therapeutic and physiological

effects

4. Techniques of application

5. Clinical applications of faradic currents.

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ACCOMMODATION

When a current flows at a constant intensity thenerve adapts itself, to the altered conditions, this

is known as accommodation. So an unvarying current is not effective in

initiating an impulse.

While the current flows at constant intensityaccommodation of the nerve takes place and thepotential difference resulting from the currentflow no longer affects the excitability of the nervefiber.

BPHTI PTH 3201(Rev)4 September 2014 4


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A fall in the intensity of current is less effective

than a rise in initiating an impulse.

It is the side of the nerve nearer to the anode

that is affected and so the anode produces agreater stimulation than the cathode.

Because the nerve has the property of

accommodation a current which rises or fallssuddenly in intensity is more effective in

initiating an impulse than one which changes

slowly. BPHTI PTH 3201(Rev)4 September 2014 5


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When the variation of the current is gradual

there is time for accommodation to take place

and a greater intensity is needed to be

effective, than if the variation is sudden.

A current that changes very slowly does not

initiate a nerve impulse.



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IMPORTANCE OF SURGING AND INTERRUPTION

When the current is interrupted the

contraction commences and ceases suddenly,

being maintained during the period of current

flow

When the current is surged the contraction

gradually increases and decreases in strength

in a matter similar to a voluntary contraction



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FARADIC

CURRENTS8


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Faradic current is unevenly alternating current

each cycle consists of two unequal phases, the

first of long duration and low EMF, the second

of short duration and high EMF.

Faradic currents have a stimulus with a

duration of 0.1to 1 milliseconds and repeated

50-100 times per second.



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PHYSIOLOGICAL EFFECTS

Stimulation of sensory nerves: a mild pricklingsensation is experienced. This is due to the

stimulation of the sensory nerves and is very mildbecause the stimuli are of short duration.

The sensory stimulation causes a vasodialation ofthe superficial blood vessels, so there is mild

reddening of the skin, or erythema.

This vasodialtion takes place only in thesuperficial tissues.



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Stimulation of motor nerves : faradic current

stimulates the motor nerve and if it is of

adequate intensity it causes contraction of the

muscles which they supply.

As the stimuli are repeated 50 times per

second or more, the contraction is tetanic.

So the current is surged or interrupted to

allow for muscle relaxation.



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Effects of muscle contraction: when a musclecontracts as a result of electrical stimulation, thechanges taking place are similar to that of a

voluntary contraction.increased metabolism.

increase in demands of oxygen and food stuffs.

an increased output of waste products, includingmetabolites.



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Metabolites cause dilatation of capillaries and

arterioles

Increased blood supply to muscle.



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As the muscles contract and relax they exert a pumpingaction on the veins and lymphatic vessels lying withinand around them.

Thus these vessels ensure the fluid they contain aremoved towards the heart.

If muscle contractions are strong enough to cause joint

movements this also exert a pumping effect.

Increased venous and lymphatic return.



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If a muscle contracts sufficient number of

times against the resistance of an adequate

load there is increase in the bulk of the musclefibers and the muscle is strengthened.

It is not sure if contractions caused by faradic

stimulation can cause this effect.



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Effects on denervated muscle: it is not

possible for a completely denervated muscle

to contract by a stimulus as short as 1

millisecond, because the impulse is too brief

to affect muscle tissue directly.

so faradic type of current is not effective for

the stimulation of denervated



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THERAPEUTIC EFFECTS1) Facilitation of muscle contraction

2) Re-education of muscle action

3) Training of a new muscle action4) Exercise for paralyzed muscle

5) Strengthening and increased bulk of muscle

6) Increase in blood supply7) Improved venous and lymphatic drainage

8) Prevention and loosening of adhesions

9) Counter irritation.BPHTI PTH 3201(Rev)4 September 2014 17


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Facilitation of muscle contraction: when a patient isunable to produce a muscle contraction,electrical stimulation may be of use in assistingvoluntary contraction

When contraction is inhibited by pain or recentinjury or there has been prolonged disuse orfaulty use of muscle.

For example active contraction of quadriceps inpainful rheumatoid arthritis of knee or aftermenisectomy, faradic stimulation may be helpfulin establishing voluntary contraction.



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Re-education of muscle action: when inability to

contract a muscle is the result of prolonged

disuse or incorrect use as seen in intrinsic foot

muscles in longstanding flat foot or the

abductor hallucis in hallux valgus, faradic

stimulation may be used to produce

contractions and so help to restore the senseof movement.



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The brain appreciates movts not muscle

actions, so the current should be applied in

such a way that it causes the movement that

the patient is unable to perform

Active contractions should be attempted at

the same time as the electrical stimulation,

the treatment being a preliminary to activeexercise.



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Training a new muscle action: after a tendon

transplantation or other reconstructive

operations, a muscle may be required to perform

a different action from that which it did before.A new movement pattern has to be established.

The muscle is stimulated so that its new action is

performed and the patient must concentrate onthe movement and attempt to assist with

voluntary contraction.



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Exercise for paralysed muscle: when there is neuropraxiaof a motor nerve, impulses from the brain are unableto pass the site of lesion to reach the muscle suppliedby the affected nerve and so voluntary power is lost.

There is no degeneration of nerve so if it is stimulatedwith faradism below the site of lesion , impulses passesto the muscles causing them to contract.

It may be used to exercise the paralysed muscles tokeep them in good condition untill the nerve conductimpulses.



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When a nerve has been severed,

degeneration of the axon takes place.

In early period of degeneration interrupted DC

may be used but later has be replaced by

faradic current.

Faradism is used only to prevent disuse

atrophy and subsequent fibrosis of muscle.



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Strengthening and increased bulk of muscle:

When a muscle is very weak the weight of thepart to be moved forms an adequate load and

electrical stimulation can be of assistance inrestoring muscle bulk and power.

Inflammation,injury of joint- active exercise

not possibleThe stimulation along with an attempt to

perform active movement is used.



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It is better for the patient that the results of

the treatment should depend on his own

efforts, active exercise is of more value than

electrical stimulation in restoring normalfunction.

Muscle strength and endurance improvement

Overload, Specificity principle



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For strength gains: 50% of MVIC(healthy

muscle), 10% of MVIC (injured muscle)

For endurance: prolonged period of

stimulation along with lower force of

contraction.



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Increase in blood supply: increased blood supply isbrought about primarily by the vasodialation inthe working muscles.

The treatment is more effective if many musclesare stimulated.

Treatment is usually applied in baths andsinosoidal currents are chosen(more sensorystimulation)

The treatment may be used for circulatorydefects such as chill blains or following a longperiod of immobilization



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Improved venous and lymphatic drainage:

Increased venous and lymphatic return is

brought about by the pumping action of the

alternating muscle contraction and relaxation

and of joint movements on the veins and

lymphatics.

It is used in the treatment of oedema



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Prevention and loosening of adhesions:

When there is effusion into the tissues adhesionsare liable to form, but these can be prevented by

keeping the structures moving on each other. If adequate active exercise is not possible,

electrical stimulation may be used for thispurpose

When a generalized effect is required sinusoidalbaths are satisfactory but for localized applicationthe faradic current is used and may be appliedwith the muscles under tension.



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Counter irritation:

The faradic current may be used to relieve

pain by counter irritation.If a strong, unsurged current is applied in the

region of a sensory nerve, accommodation

first takes place and then the conductivity isreduced, blocking the pain impulses and thus

reducing the sensation of pain.



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TECHNIQUE OF

APPLICATION:FARADIC CURRENTS.



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PREPARATION OF APPARATUS:

The therapist tests the apparatus by attaching

leads and electrodes to the terminals, holding

the two electrodes in a moistened hand.

Increasing the intensity of current untill a mild

prickling sensation is felt.

Two types of electrodes are used-the active

electrode and the indifferent electrode.



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The active electrode may be a pen electrodeor a disc electrode or a small lint pad with aflat plate electrode.

A flat plate electrode and lint pad are usedfor the indifferent electrode to complete thecircuit.

The pads consist of 8 layers of lint so thatthey are thick enough to make good contactwith tissues and with the electrode.



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They should be folded evenly with no creases, orthere will be uneven distribution of current andso discomfort.

Electrodes should be half an inch smaller allround than the pads, to reduce the danger oftheir coming in contact with the skin and causinguncomfortable concentration of current.

Corners of the electrodes should be rounded aspoints may be become bent and dig in to thepad again causing concentration of current.



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PREPARATION OF THE PATIENT :Clothing is removed from the area to be treated

and the patient supported comfortably in goodlight.

If the aim of the treatment is to re educate amuscle action, the patient may be arranged sothat movement is produced when the musclecontracts e.g.

for training quadriceps muscle , the knee must bearranged in slight flexion so that extension takesplace when muscles are stimulated.



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APPLICATION OF ELECTRODES:

The skin has to be cleaned with soap and waterto remove the natural oils and to reduce the skin

resistance.The skin can be moistened using saline water

immediately before the application of pads asions can be provided by the saline water.

The area chosen to apply the indifferent padmust be such that it does not cause any musclecontraction other than those to be treated.



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It is usually applied over the nerve trunk supplying thegroup of muscles eg: over medial epicondyle ofhumerus for the flexor muscles of the forearm.

Care must be taken not to cover motor points of any

muscles to be stimulated.

The indifferent pad must be large, to reduce thecurrent density under it to a minimum, thus preventingexcessive skin stimulation.

The indifferent electrode may be bandaged in positionor secured with rubber straps or body weight may beused to hold them in position.



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APPLICATION OF CURRENT:

The active electrode is placed over the motorpoint of the muscle to be stimulated.

The motor point is the point at which the bestcontraction is obtained, usually being situatedover the point at which the main nerve enters themuscle.

It is frequently present at the junction of theupper and middle one thirds of the fleshy belly ofthe muscle, although there are exceptions.



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The exact position of motor points varies indifferent individuals.

The intensity of the current is slowly raised

untill a good contraction is obtained.The duration of treatment depends upon the

condition of the patients muscles and on thepurpose for which it is being used.

Muscle fatigue is indicated by weakening ofcontraction but it does not happen rapidlywith faradic stimulation.



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Treatments lasts for 20- 30 minutes and about

90 contractions can be obtained for each

muscle and this is regarded as the minimumtreatment that can be effective.

Usually 20-30 contractions are produced on

one motor point.



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METHODS OF APPLICATION:

Stimulation of motor points: This method hasthe advantage that each muscle performs its

own individual action and the optimumcontraction of each muscle can be obtained.

It has the disadvantage that if many musclesare to be stimulated then large number ofcontractions for each muscle can not beproduced.



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Stimulation of muscle groups: in this method allthe muscles of a group work together.

Two electrodes are fixed one over the nerve trunksupplying the group of muscles or over theirorigin and the other so that it covers the motorpoints or over the lower ends of the fleshy belliesof the muscles.

All muscles of the group work together and it is asatisfactory method to re educate the group ofmuscles which work together normally as a groupsuch as quadriceps or small muscles of foot.



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This method also permits many morecontractions to be elicited from each muscle

than if individual motor points are

stimulated.It is important that a satisfactory contraction

of each muscle in a group is obtained. If some

muscles contract less strongly than others,because they are weaker or more deeply

placed this method is not suitable.



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Nerve conduction: if a motor nerve is

stimulated contractions are produced of all

the muscles that is supplied beyond the point

of stimulation.

For this method an indifferent electrode is

applied to a convenient area and the active

electrode to some point where the nervetrunk is superficial.



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The motor points may be inaccessible because ofwound or splinting or in the case of oedema thecurrent spreads in fluid and so it may be difficultto obtain contractions on attempting to stimulate

the motor points.It is the most comfortable method of stimulating

the muscles of facial expression. For this purposethree points over the branches of the facial nerve

are stimulated , one behind the lateral corner ofthe eye, one in front of ear and one just abovethe angle of jaw.



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Bath treatment: application of current in baths

have the advantage that the water makes good

contact with the tissues and the prolonged

soaking reduces the skin resistance and

widespread effects are produced.

It is particularly valuable when the aim of the

treatment is to increase the blood supply tothe area.



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The main disadvantage is the treatment can not belocalized and although many muscles are stimulatedthey do not all contract to the same degree, thosewhich are strongest and most superficial respondingmost readily.

Using this method flat foot can be treated by applyingfaradic foot bath. The electrodes may be arranged indifferent ways.

One method for stimulation of muscles of the

longitudinal arch is to place electrodes transverselyacross the bottom of the bath, one under the heels andother under the anterior part of the feet.



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The muscles of the anterior transverse arch

may be stimulated by placing the electrodes

one on each side of the feet, level with

metatarsal shafts and with the edges of theelectrodes just under the lateral borders of

the feet.

In the both the methods the water in the bathshould just cover the toes.



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Faradism under pressure: this method is usedto increase the venous and lymphatic drainagefrom an oedematous area.

Contractions of many muscles are requiredand may be obtained by placing large pads sothey cover motor points of many groups of

muscles or by nerve conduction, the nervetrunks supplying the limb are stimulated abovethe oedematous area.



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The limb is supported in elevation so that gravityassists the venous and lymphatic drainage andthe limb is covered by elastic bandage.

The elastic bandage increases the pressure on thevessels when the muscles contract and its recoilon muscle relaxation exerts a further pumpingaction.

The current is applied and surged fairly slowly, in

order to obtain a good pumping effect. Thetreatment lasts up to 20 minutes and adequaterest periods given in between as it is fatiguing.



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Faradism under tension: the aim of this

treatment is to stretch and loosen adhesions.

The limb is fixed so that the muscles involved

are in a stretched position.

The current is then applied either to individual

motor points or to whole group of muscles and

increased untill a contraction is obtained.



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Movement is not permitted and so

contractions are isometric and so increased

tension in the muscle stretches the muscle

adhesions

The current is usually surged, but may be

interrupted . Interruption causes a more

sudden stretch but needs high skill of theoperator for its use.



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REFERENCES:

Claytons Electrotherapy and Actinotherapy

4thedition.



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`

QUESTIONS



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faradic currents..pptx

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