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Physiological and therapeutic uses of low frequency(F/G) currents

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FARADIC AND GALVANIC CURRENTS A.THANGAMANI RAMALINGAM PT, MSc (PSY), MIAP
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Page 1: Physiological and therapeutic uses of low frequency(F/G) currents

FARADIC AND GALVANIC

CURRENTSA.THANGAMANI RAMALINGAM

PT, MSc (PSY), MIAP

Page 2: Physiological and therapeutic uses of low frequency(F/G) currents

HISTORY OF ES 420B.C-hippocrates-in torpaedo fish 46A.D-scribonius

largus-gout/headache 1700-luigi galvani & alessantro volta 1745-leyden jar for ES 1831-michael faraday 1850s-duchene-motor points(father

of ES) 1909-rheo/chron-louis 1916-SD curve-Adrian FES-1961-liberson 1962-HVPC-robert becker

Page 3: Physiological and therapeutic uses of low frequency(F/G) currents

Types of electrical stimulatorsConstant current stimulator

Constant voltage stimulator

Less areamore currentburn

Less arealess currentsafety

Page 4: Physiological and therapeutic uses of low frequency(F/G) currents

BLOCK DIAGRAM TO ILLUSTRATE ELECTRICAL PULSE GENERATORS.

Transformers Rectifiers Filters Regulators are used for pulse generation in circuits

Page 5: Physiological and therapeutic uses of low frequency(F/G) currents

PHYSIOLOGICAL EFFECTS OF ELECTRICAL STIMULATION Cellular level Tissue level Segmental level Systemic level

Page 6: Physiological and therapeutic uses of low frequency(F/G) currents

EFFECTS AT CELLULAR LEVEL Excitation of nerve cells Changes in cell membrane permeability Protein synthesis Stimulation of fibrobloast, osteoblast Modification of microcirculation

Page 7: Physiological and therapeutic uses of low frequency(F/G) currents

EFFECTS AT TISSUE LEVEL Skeletal muscle contraction Smooth muscle contraction Tissue regeneration

Page 8: Physiological and therapeutic uses of low frequency(F/G) currents

EFFECTS AT SEGMENTAL LEVEL Modification of joint mobility Muscle pumping action to change

circulation and lymphatic activity Alteration of the microvascular system

not associated with muscle pumping Increased movement of charged

proteins into the lymphatic channels

Page 9: Physiological and therapeutic uses of low frequency(F/G) currents

EFFECTS AT SEGMENTAL LEVEL Transcutaneous electrical stimulation

cannot directly stimulate lymph smooth muscle, or the autonomic nervous system without also stimulating a motor nerve

Page 10: Physiological and therapeutic uses of low frequency(F/G) currents

SYSTEMATIC EFFECTS Analgesic effects as endongenous pain

suppressors are released and act at different levels to control pain

Analgesic effects from the stimulation of certain neurotransmitters to control neural activity in the presence of pain stimuli

Page 11: Physiological and therapeutic uses of low frequency(F/G) currents

Electro chemical effect2cl2 +H20 4HCl+O2 - under anode-

coagulation/sclerosis2Na +2H202NaoH +H2 -under cathode –

sclerolytic/haemorrhage Electro thermal effect- H α I2 R t Electro physiological effect –

RMPAPconduction

Page 12: Physiological and therapeutic uses of low frequency(F/G) currents

THERAPEUTIC USES FOR ELECTRICAL STIMULATION Control acute & chronic pain Reduce edema Reduce & or inhibit muscle spasm Reduce joint contractures Minimize atrophy Facilitate tissue healing Facilitate muscle reeducation Facilitate fracture healing Strengthen muscle

Page 13: Physiological and therapeutic uses of low frequency(F/G) currents
Page 14: Physiological and therapeutic uses of low frequency(F/G) currents

FARADIC VS GALVANIC

AC/DC Short duration

pulse <1sec or micro

sec

DC Long duration pulse >1sec elicits a muscle

contraction from de -nervated muscle, but the phase duration is so long that C fibers are also stimulated

Page 15: Physiological and therapeutic uses of low frequency(F/G) currents

UNEVEN AC/ FARADIC Two phases PD: 1 ms No polarity

needed Surged Mild prickling

sensation

Freq:50 HzPD: 1 ms

Page 16: Physiological and therapeutic uses of low frequency(F/G) currents

GALVANIC Faradic is high

frequency current(50-100Hz), where as galvanic is low frequency

single phase PD: >1 ms polarity needed

galvanic give stabing type of sensation

Page 17: Physiological and therapeutic uses of low frequency(F/G) currents

TECHNIQUES OF APPLICATION/PRINCIPLES

OF APPLICATION

Page 18: Physiological and therapeutic uses of low frequency(F/G) currents

TYPES OF ELECTRODES Metal electrode Rubber/silicon Water bath Adhesive Needle Probe electrode Pad electrode

Page 19: Physiological and therapeutic uses of low frequency(F/G) currents

ELECTRODE PLACEMENT

Unipolar method Bipolar method

Stabile Labile

Nerve conduction method

Group stimulation method

Page 20: Physiological and therapeutic uses of low frequency(F/G) currents

CURRENT DENSITY

Current Density- - Refers To The Volume Of Current In The Tissues

Highest At Surface And Diminishes In Deeper Tissue

Page 21: Physiological and therapeutic uses of low frequency(F/G) currents

ALTERING CURRENT DENSITY

Change The Spacing Of ElectrodesMoving Further Apart Increases Current

Density In Deeper TissuesCurrent density for any electrode/skin contact

area should not exceed 2 mA rms/cm’

Page 22: Physiological and therapeutic uses of low frequency(F/G) currents

SKIN RESISTENCE LOWERING washing the

surface to remove some of the keratin and sebum and leaving the skin wet.

Warming the skin

If the adhesion of the electrode to the skin surface alters, or the pressure of sponge or pad decreases, this can lead to a higher resistance

Page 23: Physiological and therapeutic uses of low frequency(F/G) currents

PHYSIOLOGICAL EFFECTS Sensory nerves:

Marked prickling sensation longer duration

Motor nerves: Tetanizes, with a sequence of contraction followed by relaxation

NO chemical effects

Swelling: Absorption of exudate

Circulation: Superficial vasodilation via axon reflex (capillary vasodilation) hyperaemia

Page 24: Physiological and therapeutic uses of low frequency(F/G) currents

THERAPEUTIC EFFECTS Give as a group activity Facilitate muscle contraction Re-educate muscle action Train new muscle action Exercise for paralyzed muscles Hypertrophy Increase strength Improve circulation Prevent and loosen adhesions

Page 25: Physiological and therapeutic uses of low frequency(F/G) currents

ELECTROTHERAPEUTIC WINDOWS •  Amplitude window

• Frequency window

• Acute window

• chronic window

• Energy based window

• Time based window

• Interval based

window

Page 26: Physiological and therapeutic uses of low frequency(F/G) currents

THE ARNDT-SCHULZ RULE OR LAW

For every substance, small doses stimulate, moderate doses inhibit, large doses kill.

Page 27: Physiological and therapeutic uses of low frequency(F/G) currents

VOLUNTARY CONTRACTION VS ELECTRICAL STIMULATION

Recruitment order small->large Fibre type slow->fast twitch Central fatigue Fatigue resistant motor

units first More force-more fatigue

Opp

Opp

Peripheral fatigue Opp

high/low-no difference

Page 28: Physiological and therapeutic uses of low frequency(F/G) currents

Muscle Re-Education Muscular inhibition after surgery

or injury is primary indication Patient feels the muscle

contract, sees the muscle contract, and can attempt to duplicate this muscular response

Current intensity must be adequate for muscle contraction but comfortable

Pulse duration must be set as close as possible to the duration needed for chronaxie of the tissue to be stimulated

Pulses per second should be high enough to give a tetanic contraction (20 to 40 pps)

Interrupted or surged current must be used

High-voltage pulsed or medium-frequency alternating current may be most effective

On time should be 1 to 2 seconds

Off time should be 4 to 10 seconds

Total treatment time should be about 15 minutes, repeated several times daily

Next, patient should alternate voluntary muscle contractions with current-induced contractions

Page 29: Physiological and therapeutic uses of low frequency(F/G) currents

Muscle Pump Contractions Used to duplicate the

regular muscle contractions that help stimulate circulation by pumping fluid and blood through venous and lymphatic channels back to the heart

Can help in reestablishing proper circulatory pattern while keeping injured part protected

Current intensity must be high enough to provide a strong, comfortable muscle contraction

Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated if not preset

Pulses per second should be at beginning of tetany range (20 pps).

Interrupted or surged current must be used

On time should be 5 to 10 seconds. Off time should be 5 to 10 seconds. The part to be treated should be

elevated Total treatment time should be 20 to

30 minutesrepeated two to five times daily

Page 30: Physiological and therapeutic uses of low frequency(F/G) currents

Retardation of Atrophy Electrical stimulation reproduces

physical and chemical events associated with normal voluntary muscle contraction and helps to maintain normal muscle function

Current intensity should be as high as can be tolerated

Contraction should be capable of moving the limb through the antigravity range or of achieving 25% or more of the normal maximum voluntary isometric contraction (MVIC) torque for the muscle

Patient can be instructed to work with electrically induced contraction, but voluntary effort is not necessary

Total treatment time should be 15 to 20 minutes, or enough time to allow a minimum of 10 contractions

Treatment can be repeated two times daily

duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated

Pulses per second should be in the tetany range (20 to 85 pps)

Interrupted or surge type current should be used

Medium-frequency alternating current stimulator is the machine of choice

On time should be between 6 and 15 seconds

Off time should be at least one minute preferably two minutes.

Muscle should be given some resistance, either gravity or external resistance provided by the addition of weights or by fixing the joint so that the contraction becomes isometric

Page 31: Physiological and therapeutic uses of low frequency(F/G) currents

Muscle Strengthening Current intensity should make

muscle develop 60% of torque developed in a maximum voluntary isometric contraction (MVIC)

Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated

Muscle is given an isometric contraction torque equal to or greater than 25% of the MVIC torque

Patient instructed to work with the electrically induced contraction, but voluntary effort is not necessary

Total treatment should mimick normal active resistive training protocols of 3 sets of 10 contractions

Pulses per second should be in the tetany range (20 –85 pps)

Surged or interrupted current with a gradual ramp to peak intensity most effective

On time should be 10-15 seconds

Off time should be 50 seconds to 2 minutes

Medium-frequency alternating current stimulator is machine of choice

Page 32: Physiological and therapeutic uses of low frequency(F/G) currents

Increasing Range of Motion Electrically stimulating a muscle

contraction pulls joint through limited range

Continued contraction of muscle group over extended time appears to make contracted joint and muscle tissue modify and lengthen

Pulses per second should be at the beginning of the tetany range (20 to 30 pps)

Interrupted or surged current should be used

On time should be between 15 and 20 secs

Off time should be equal to or greater than on time, fatigue is a big consideration

High-voltage pulsed or medium-frequency alternating current stimulators are suggested

Current intensity must be of sufficient intensity and duration to make muscle contract strongly enough to move the body part through antigravity range

Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated

Stimulated muscle group should be antagonistic to joint contracture and patient should be positioned so joint will be moved to the limits of available range

Patient is passive in treatment and does not work with electrical contraction

Total treatment time should be 90 minutes daily broken into 3 x 30-minute treatments

Page 33: Physiological and therapeutic uses of low frequency(F/G) currents

Reducing EdemaSensory level direct current used

as a driving force to make charged plasma protein ions in interstitial spaces move in the direction of oppositely charged electrode

Distal electrode should be negative

Treatment should begin immediately after injury

Thirty minute treatment showed good control of volume for 4 to 5 hours

High voltage pulsed generators are effective, low voltage generators are not effective

Current intensity should be (30V-50V) or 10% less than needed to produce a visible muscle contraction

Preset short duration interrupted DC currents with high pulse frequencies (120 pps) on high voltage equipment are effective

Page 34: Physiological and therapeutic uses of low frequency(F/G) currents

Stimulating Denervated Muscle Purpose for electrically stimulating

denervated muscle is to help minimize the extent of atrophy while the nerve is regenerating

Degenerative changes progress until muscle is reinnervated by axons regenerating across site of lesion

If reinnervation does not occur within 2 years fibrous connective tissue replaces contractile elements and recovery of muscle function is not possible

Length of pulse should be as short as possible but long enough to elicit a contraction

Current waveform should have pulse duration = or > than chronaxie of denervated muscle

Amplitude of current along with pulse duration must be sufficient to stimulate a denervated muscle with a prolonged chronaxie while producing a moderately strong contraction of muscle fibers

Muscle fibers experience a decrease in size, diameter and weight of the individual muscle fibers

There is a decrease in amount of tension which can be generated and an increase in the time required for contraction

A current with an asymmetric, biphasic (faradic)waveform pulse duration < 1 ms may be used during the first 2 weeks

After 2 weeks, either an interrupted DC square wave or a progressive DC exponential wave with long pulse duration > 10 ms, or a AC sine wave with frequency < 10 Hz will produce a twitch contraction

Pause between stimuli should be 4 to 5 times longer (about 3-6 seconds) than stimulus duration to minimize fatigue

Either a monopolar or bipolar electrode setup can be used with small diameter active electrode placed over most electrically active point

Stimulation should begin immediately using 3 sets of 5 -20 repetitions 3 x per day

Page 35: Physiological and therapeutic uses of low frequency(F/G) currents

Basic Model of Electrotherapy

Page 36: Physiological and therapeutic uses of low frequency(F/G) currents

Denervated muscle stimulationES may disrupt regenerating NMJTrauma of the muscleTime consumingThree stimulation sessions/day three to five sets of 5-20 isometric

contractions5s –rest period/contraction 1m-rest period /set pW >than chronoxie

Page 37: Physiological and therapeutic uses of low frequency(F/G) currents

Muscle Contractions 1 pps = twitch

10 pps = summation 25-30 pps = tetanus (most fibers will reach

tetany by 50 pps)

50-100 micro sec –sensory stimulation 200-300 micro sec –motor stimulation

Page 38: Physiological and therapeutic uses of low frequency(F/G) currents

Frequency selection:100Hz - pain relief50-60 Hz = muscle contraction1-50 Hz = increased circulationThe higher the frequency (Hz) the more

quickly the muscle will fatigue1-4 Hz-beta endorphin40-100Hz-enkepalin,serotonin

Page 39: Physiological and therapeutic uses of low frequency(F/G) currents

Electrocution and dangersElectric and earth shockELCB BF/CF areasGuidelines by Robertson et al(2001)AC is more dangerous than DC(P=V*I)

The strongest stimulation is where the current exits the body

Page 40: Physiological and therapeutic uses of low frequency(F/G) currents

Unexpected effects of ESOver and above the normal physiological and

psychological limitsSkinEyesGeneral symptomsCardio-respNeurologicalAttitudemusculoskeletal

Page 41: Physiological and therapeutic uses of low frequency(F/G) currents

Risk ManagementRisk grading-0,(1,2),3Safety& maintenance( quality assurance)InfectionAversionChildren (guidelines)

Page 42: Physiological and therapeutic uses of low frequency(F/G) currents

ContraindicationOther Low Frequency (e.g. muscule stim, diadynamics etc) 

Pregnancy (local) CI** SEE NOTE

Local Circulatory Insufficiency

PRECAUTION

Pregnancy (general)   Epilepsy CI NECK

Malignancy LOCAL CI Devitalised Tissues PRECAUTION

Specialised Tissues

EYE,TESTIS

Active Epiphysis LOCAL CI

Active Implants (incl Pacemakers)

CI TESTS  

Tissue Bleeding CI Thermal Skin

Test  

Metal Implant   Sharp/Blunt Skin Tests YES

Page 43: Physiological and therapeutic uses of low frequency(F/G) currents
Page 44: Physiological and therapeutic uses of low frequency(F/G) currents

Polarity With Continuous DC CurrentImportant Consideration When Using Iontophoresis

Positive PoleAttracts - IonsAcidic ReactionHardening of TissuesDecreased Nerve Irritability

Negative Pole• Attracts + Ions• Alkaline Reaction• Softening of

Tissues• Increased Nerve

Irritability

Page 45: Physiological and therapeutic uses of low frequency(F/G) currents
Page 46: Physiological and therapeutic uses of low frequency(F/G) currents
Page 47: Physiological and therapeutic uses of low frequency(F/G) currents
Page 48: Physiological and therapeutic uses of low frequency(F/G) currents
Page 49: Physiological and therapeutic uses of low frequency(F/G) currents

Motor points


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