2. Interrupted Direct current (IDC)
• If continuous unidirectional current is
interrupted, it give rise to series of pulses or
phases of unidirectional current.
• Pulse-duration
• Inter-pulse duration
4. Duration & Frequency of IDC:
• The duration and frequency of the impulses can be
adjusted.
• Frequency of the current reduces with increase in the
pulse duration. Pulse duration of 100ms will have
frequency of 30 cycles/minute.
• The interval between the impulses should never be
shorter duration than the impulses themselves and is
usually appreciably longer.
5. Types of IDC
• Currents produced for therapeutic purposes may
have sudden or gradual fall, hence depending on this
there are several types, which are as follows:
1) Rectangular
2) Trapezoidal
3) Triangular
4) Saw-tooth
5) Depolarized
• Rectangular pulses have sudden rise whereas others
like trapezoidal, triangular and saw-tooth have
gradual rise.
6. Cont…
• The impulses in which current rises gradually
are often termed ‘selective’
• Some equipment allows for low-intensity
reversed current between the impulses. Here
the chances of electrolyte burns are very less.
The reverse wave of current between the
impulses reduces the chemical formation, and if
the quantity of electricity passed in the reversed
current is equal to that in the forward one any
chemicals formed are neutralized and the
danger of burns eliminated.
7. Selection of impulses
• Rectangular impulse is capable of producing muscle
contraction but selective impulse is always
satisfactory.
• A low intensity and gradual rise in current is
often best for stimulation of denervated muscle as it
brings about satisfactory contraction with less
sensory stimulation than with the rectangular
impulses.
• Proper selection of current leads to elimination of
unwanted contraction of innervated muscles present
in the closed proximity.
8. Effects of IDC
1. ELECTRICALEXCITABILITY
2. NERVE FIBRE
0.02-1ms Generate Action Potential
Longer duration Less Intensity
Shorter Duration More Intensity
3. MUSCLE FIBRE
Don’t respond to Shorter duration impulses ??
0.02-1ms Require More intensity
100-1000ms requires less intensity
9. Physiological & Therapeutic Effects of IDC
SensoryStimulation:
During the passage of direct currents the patient is
aware of a mild tingling or prickling sensation,
which may merge into a mild irritation or itching.
Hyperaemia :
If sufficient current has passed for long enough an
erythema of the skin will be evident under both
electrodes, and is more marked under the negative
(cathode). This erythema is confined to the area of
the applied Electrode indicating a capillary
hyperaemia, unlike that due to heat in which
arteriolar dilatation occurs.
10. Cont…
Reliefof Pain:
• Strong sensory stimulation blocks the pain
transmission at the level of spinal cord by pain
gate theory.
• The hyperaemia occurring may help to remove
the nociceptive substances and thus reducing
pain.
11. Cont…
Accelerationof Healing:
• Electrical stimulation by direct current
enhances healing process.
• It has also got effects on healing of superficial
and open wounds.
Motor nerve stimulation
Denervatedmusclestimulation
12. IDC used in
• To re-educate muscle
• To gain range
• Facilitate muscle contraction
• Increase strength
• Improve circulation
13. Techniques of Treatment
• Among the several indications of IDC, muscle stimulation is
most important one. Here, treatment should be given in
such a way that all muscle fibres get stimulated properly.
There are several methods to achieve this:
1) Labile Technique:
Here one electrode is fixed over the origin of muscle group
and other electrode, which is preferably disc or pen
electrode is held over the lower end of the muscle belly to
be stimulated or is stroke down it. This is known as labile
technique.
• The movement of the electrode ensures proper contraction
or stimulation of all the muscle fibres. Also there is less skin
irritation by this technique
14. Cont…
2-Group Stimulation:
• In this technique active electrode is placed over the
muscle group to be stimulated (E.g.:- extensor
muscles of wrist in case of radial nerve palsy) and
large indifferent electrode is placed over convenient
site to complete the circuit. This is known as group
stimulation technique.
15. Contraindications to electrical stimulation:
• Metal implants.
• Strong muscle contraction might cause joint or
muscle damage; detachment of a thrombus;
spread of infection; and hemorrhage.
• Stimulation of autonomic nerves might cause
altered cardiac rhythm or other autonomic
effects.
• Currents might provoke undesirable metabolic
activity in healed tuberculous infections.
