7 - Interrupted Direct Current
7 - Interrupted Direct Current
7 - Interrupted Direct Current
lecture 7
dr. amal hm. ibrahim
aebrahim123@hotmail.com
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.
Interrupted Direct Current IDC The term interrupted direct current (IDC) is used to describe continuous unidirectional current when it is interrupted to give pulses or phases of any duration, shape, or frequency.
Faradic-type Current
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Faradic-type Current
Faradic-type currents are short duration interrupted direct current of pulses ranged from 0.1 to 1ms and frequency of 30 to 100 Hz. With frequency 100Hz the time for each cycle is 10ms so, with a 1ms pulse the interval period will be 9ms. The waveform of faradictype current may be unidirectional or biphasic (asymmetrical)
Faradic-type Current
The faradic-type currents are always surged when used for therapeutic purposes. The comfortable pulse is either 0.1ms with frequency 70Hz or 1ms pulse with frequency 50Hz.
Faradic-type Current The effective nerve stimulus is the spike of the voltage which can be about 1ms in duration, the rest of the pulse having much lower voltage, does not cause nerve stimulation.
Faradic-type Current
Faradic current causes a titanic contraction of stimulated muscle. Treatment by faradic current is called faradism.
Faradic-type Current
The active electrode should be connected to the cathode as muscle contraction will be more easily produced with less current.
Stimulation of motor points can be done by using guide chart indicate all superficial muscles of body
Physiological Effects of Faradic-type Current 2. 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.
1. Facilitation of muscle contraction inhibited by pain like post operative or post-traumatic inability to achieve voluntary contraction of certain muscles. 2. Early stage of muscle reinnervation.
Contraindications
1- Skin lesions as cuts and abrasions to avoid the difference of skin resistance which may lead to more concentration of current on some points especially under electrodes causing discomfort and pain. 2- Cardiac pacemaker.
Contraindications
3- Infection to avoid spread of infection by low frequency current. 4- Superficial metal to avoid concentration of current on metal and cause burn.
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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
Electrotherapy: Evidence-based Practice By Sheila Kitchen, Sarah Bazin, Edward Bellis Clayton Contributor Sheila Kitchen, Sarah Bazin Published by Elsevier Health Sciences, 2002
Electrotherapy: Evidence-based Practice By Sheila Kitchen, Sarah Bazin, Edward Bellis Clayton Contributor Sheila Kitchen, Sarah Bazin Published by Elsevier Health Sciences, 2002
1- Conventional TENS
This mechanism is called pre-synaptic inhibition by Hi-TENS or traditional or conventional TENS. Conventional TENS is used for self treatment with recommended duration from 30 to 60 minutes, once or twice a day or may be used for all 24 hours of the day.
2- Acupuncture-like TENS
It is high intensity low frequency (less than 10Hz, commonly 2-4Hz), with pulse duration of around 0.2ms. The intensity is very high close to the patient tolerance to stimulate A and C fibers leading to the release of endorphins and encephalin.
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 become more superficial
Acupuncture-like TENS is applied once 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.
3- Burst TENS
Burst TENS consists of a train or burst of pulses of 2Hz (some times varying from 1-5Hz). Each burst lasts 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.
Burst TENS is combines both conventional and acupuncture-like TENS and therefore provides pain relief by both routs. Burst TENS is practically suitable for the treatment of deeperlying painful regions (myofascial pain) and cases of chronic pain.
The treatment duration is up to 30 minutes to be effective and treatment can be repeated during the same day.
4- Modulated TENS In modulated TENS the pulse width, frequency and intensity are all constantly and automatically varied. This type of TENS is useful for prevent adaptation of the nerve to the current.
Application of TENS
Before applying TENS to any patient you 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.
Application of TENS
Visual 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).
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 is like. The only objective way of pain assessment is the measurement of range of motion.
Electrode Placement
Over painful points. Over dermatome, myotome, or sclerotome. Trigger or acupuncture points which can be located by their lower resistance compared with surrounding 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.
Indications
Contraindications
Undiagnosed pain. Pregnancy (especially during first three months of pregnancy). Heart pacemaker. The eyes or near to them. Over carotid sinus to avoid cardiac arrhythmias.
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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