7- Interrupted Direct Current

7/27/2019 7- Interrupted Direct Current

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Interrupted directcurrentIDClecture 7

dr. amal hm. ibrahim

[email protected]


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Objectives

To define the different types of IDC.

To know the IDC current characteristics

and uses.

To know the Faradic current characteristics.

To know physiological effects of faradic

current. To define the TENS current.

To know physiological effects of TENS.


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Interrupted Direct Current

IDC

The term interrupted direct current

(IDC) is used to describe continuous

unidirectional current when it isinterrupted to give pulses or phases

of any duration, shape, or frequency.


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IDC

Interrupted direct current is

commonly described the currents oflong duration (1msec or more).


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IDC There are two types of long duration

interrupted direct current:

1- Rectangular wave pulses.

2- Accommodation pulses.


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IDC 1- Rectangular wave pulses: pulses of any

duration between 1 and 600msec separated

by pulse interval of any duration from 1 to

many seconds. Used to stimulate sensory and

motor nerves but it is unique in stimulation of

denervated muscles.


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IDC 2- Accommodation pulses: have many types

like triangular, trapezoidal, and saw-tooth.

The pulse duration ranged from 300 to

1000msec. These pulses are used for

stimulation of denervated muscle.


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Faradic-type Current

[email protected]


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Faradic-type currents are short durationinterrupted direct current of pulses ranged

from 0.1 to 1ms and frequency of 30 to 100

Hz. With frequency 100Hz the time for eachcycle is 10ms so, with a 1ms pulse the interval

period will be 9ms. The waveform of faradic-

type current may be unidirectional or biphasic

(asymmetrical)


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The faradic-type currents are always

surged when used for therapeutic

purposes. The comfortable pulse iseither 0.1ms with frequency 70Hz or

1ms pulse with frequency 50Hz.


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The effective nerve stimulus is

the spike of the voltage which

can be about 1ms in duration, therest of the pulse having much

lower voltage, does not causenerve stimulation.


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Faradic current causes a titaniccontraction of stimulated muscle.

Treatment by faradic current is called

faradism.


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The active electrode should be

connected to the cathode as muscle

contraction will be more easily produced

with less current.


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Physiological Effects of Faradic-type

Current1. Stimulate innervated muscles whose motor

nerves are intact producing titanic

contraction. The number of motor units

brought into action will depend on the

strength of current and placement of

electrodes.


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Current Stimulation of motor points can

be done by using guide chart

indicate all superficial muscles of

body


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Current

As mentioned before if you stimulate muscleby using fixed pad electrodes it is preferableto use constant current to be morecomfortable as the skin resistance fluctuates(change) the voltage will fluctuate tomaintain constant current.

But if you move the pad, it is better to useconstant voltage because the current will bealtering.


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Current2. Stimulation of sensory nerves to

produce a mild prickling sensation

for reducing pain feeling

3. Stimulate motor nerves of large

proximal muscles to reduce edema.


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Clinical Uses of Faradic-type

Current

Faradic-type current is still frequently applied

in the form of functional electrical stimulation

(FES). In this technique the application of the

faradic current is combined with the patient

activity.


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Clinical Uses of Faradic-type Current

1. Facilitation of muscle contraction

inhibited by pain like post operative

or post-traumatic inability to achievevoluntary contraction of certain

muscles.

2. Early stage of muscle re-

innervation.


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Clinical Uses of Faradic-type Current

3. Treatment of hysterical paralysis.

4. Treatment of atrophied and weak

muscles following long duration

immobilization.


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Clinical Uses of Faradic-type Current5. Treatment of muscle

imbalance as in faulty posture

(flat foot and scoliosis).

NOTE: Faradic-type currents

never used to stimulate

denervated muscles.


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Contraindications1- Skin lesions as cuts and abrasions

to avoid the difference of skin

resistance which may lead to moreconcentration of current on some

points especially under electrodes

causing discomfort and pain.

2- Cardiac pacemaker.


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Contraindications 3- Infection to avoid spread of

infection by low frequency current.

4- Superficial metal to avoidconcentration of current on metal

and cause burn.


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Transcutaneous ElectricNerve StimulationTENS

[email protected]


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Transcutaneous electrical

nerve stimulation (TENS) is anon invasive modern

electrical method of

managing both acute (short

term pain) and chronic (long

term pain).


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It is used for providing a degree

of pain relief (symptomatic) by

stimulating sensory nerves.

TENS is an alternating current

characterized by variable phase

duration and a variable phase

interval which can be used to

vary frequency


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Electrotherapy: Evidence-based Practice

By Sheila Kitchen, Sarah Bazin, Edward Bellis Clayton

Contributor Sheila Kitchen, Sarah Bazin

Published by Elsevier Health Sciences, 2002


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The phase duration is very short, varying from

0.01 to 0.4ms. The frequency is usuallyvariable and ranged from 2 to 200Hz. The

maximum peak current is about 100mA.

Although it is a small current but it is sufficient

because the primary target for the therapy is

the sensory nerves.


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Electrotherapy: Evidence-based Practice

By Sheila Kitchen, Sarah Bazin, Edward Bellis Clayton




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1- Conventional TENS

It is a current withhigh frequency from

50-100Hz, pulse

duration around0.05ms and low

intensity Electrotherapy: Evidence-based PracticeBy Sheila Kitchen, Sarah Bazin, Edward Bellis Clayton




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1- Conventional TENS

The intensity is turned up slowly until a prickling or

tingling sensation is felt without painful feeling ormuscle contraction.

This current with low intensity, high frequency will

stimulate large low threshold mechanoreceptors A

fibers which go up in the spinal cord without synapse

and give collateral to A and C fibers to inhibit them.


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1- Conventional TENSThis mechanism is called pre-synaptic

inhibition by Hi-TENS or traditional or

conventional TENS. Conventional TENS isused for self treatment with

recommended duration from 30 to 60

minutes, once or twice a day or may beused for all 24 hours of the day.


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2- Acupuncture-like TENS

It is high intensity low frequency (less than10Hz, commonly 2-4Hz), with pulse duration

of around 0.2ms. The intensity is very high

close to the patient tolerance to stimulate Aand C fibers leading to the release of

endorphins and encephalin.


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The acupuncture-like

TENS is applied to

acupuncture point

which is

considered as a

place where a

small bundle of A

and sympathetic

efferent fibers

pierce the deep

fascia to becomemore superficial


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Acupuncture-like TENS is appliedonce per day for 20 to 30 minutes.Although this type of TENS is more

effective than conventional TENS, but

many patients can not tolerate the

high intensity. The acupuncture TENS

is applied for patient who do not

respond to conventional TENS.


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3- Burst TENS Burst TENS consists of a train or burst of pulses of2Hz (some times varying from 1-5Hz). Each burstlasts for 70 ms and as the internal frequency of the

bursts is at the usual conventional TENS frequency of

50- 100Hz, this result in release of endorphins at the

central level which have a pain reducing effect.


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Burst TENS is combines both

conventional and acupuncture-like TENS

and therefore provides pain relief byboth routs. Burst TENS is practically

suitable for the treatment of deeper-

lying painful regions (myofascial pain)and cases of chronic pain.
http://2.bp.blogspot.com/-VHQQK3giI44/TezbVkNWU4I/AAAAAAAAAAc/fcbqJHVyw9s/s1600/tens-use.jpg


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The treatment duration is upto 30 minutes to be effectiveand treatment can be

repeated during the same

day.
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4- Modulated TENS In modulated TENSthe pulse width,frequency and

intensity are all

constantly andautomatically

varied. This type of

TENS is useful for

prevent adaptation

of the nerve to the

current.


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Application of TENSBefore applying TENS to any patientyou must make pain assessment to

evaluate the treatment results. There

are many methods for pain

assessment, the common subjective

way is known as visual analogue scale

or VAS.


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Application of TENSVisual analogue scale or VAS. (on which a 10 cm line,

start with no pain, in its middle tolerable pain and at

the end worst pain) and the patient marks the

intensity of pain between no pain and worst pain).


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Another subjective method is faces at which there

are six faces start with happy face and end with very

angry and crying face, the patient chose one who islike. The only objective way of pain assessment is the

measurement of range of motion.


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Electrode Placement Over painful points.

Over dermatome, myotome, or sclerotome.

Trigger or acupuncture points which can be

located by their lower resistance compared withsurrounding skin. To determine acupuncture

point we use an electronic probe.

Electrodes are placed over the line of nerve

superficially.

Electrodes are covered with gel and fixed to the

skin with adhesive tape or bandage. Electrodes

may be self adhesive and gelled.


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Indications


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Contraindications Undiagnosed pain.

Pregnancy (especially during first three

months of pregnancy).

Heart pacemaker.

The eyes or near to them.

Over carotid sinus to avoid cardiacarrhythmias.


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Contraindications Over pharyngeal region to avoid interfere

with normal breathing and swallowing.

Skin lesions or wounds (different

resistance).

Over non sensation area.

With implanted hear aid.

Over infected or inflamed area.


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Questions?????

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7- Interrupted Direct Current