Interrupted direct current (IDC) is a pulsing current used for therapeutic and diagnostic purposes, characterized by varying pulse durations, waveforms, and electrical properties. IDC can stimulate sensory and motor nerves, producing different physiological effects, including muscle contractions and skin responses. Proper application techniques and consideration of contraindications are essential to ensure safe and effective treatment.

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2. Interrupted Direct current
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3. objectives
• What is Interrupted direct current
• Terminologies
• Wave form types
• Physiological effects
• Therapeutic and diagnostic uses
• General technique of application
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4. Interrupted Direct Current
IDC
 (IDC) is used to describe continuous
unidirectional current when it is
interrupted to give pulses or phases
of any duration, shape, or frequency.
• commonly described the currents of
long duration (1msec or more).
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5. ON time
 The length of time an impulse is allowed
to flow.
 It is the same as pulse duration
50ms 50ms
Flow
50ms
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6. Off time/ Interpulse duration
 The duration of no flow, is the same as
inter-pulse duration
50ms 50ms
50ms
No flow
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7. Rise time/on ramp
 Is the duration the current takes to
reach the desired intensity (0 to desired
intensity)
Rise time Decay time
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8. Decay time/off ramp
 Is the time taken for the current to come
down to base line(zero)
Decay time
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9. ELECTRIC PULSE
Can be more fully describe according to
• PULSE DURATION: expressed in seconds
• INTENSITY: expressed in amperes or volts
• SHAPE: wave form
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10. WAVE FORM
Describe the rise and fall pattern of a pulse
the shape of the wave form reflects the time
required for the current to reach to maximum
intensity
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11. WAVE FORM
 There are two types of long duration
• interrupted direct current:
 • 1- Rectangular wave pulses.
 • 2- Accommodation pulses.
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12. 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
 Wave form with sudden rise in intensity are suitable for
innervated muscles
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13. 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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14. EXCITABILITY OF NERVE
• SIGNAL
• RESTING MEMBRANE POTENTIAL
• CHANGE IN RESTING MEMBRANE POTENTIAL
• ACTION POTENTIAL GENERATE
• NERVE EXCITATION
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15. • POLARITY:
• Cathode is used as active electrode because it causes
decrease in potential difference
• ACCOMODATION:
• The nerve and muscle tissue posses the property to adapt
itself to slowly increasing stimulation intensities.
• This causes a decrease of excitability of the membrane,
and thus requiring more intensity of stimulating current.
• Nerve fibre has a high accommodation rate.
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17. Motor point
• Is a region of a muscle
where a great density of
terminal motor end
plates is found near the
surface.
• Stimulation of motor
point isolate a muscle or
segment of a muscle
• It is generally present at
the middle of the
longitudinal axis of the
muscle
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18. Electro tonus
 Sub threshold nerve stimuli do not
cause an action potential but they
do affect the membrane potential. This
phenomenon is known as electro tonus.
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19. • Catelectrotonus:
The cathode produces a local depolarizing
potential that rises rapidly but falls exponentially
with time making the outer nerve membrane
surface less positive lowers the threshold, which
increases the nerve’s excitability known as
catelectrotonus
• Anelectrotonus:
The anode produces hyperpolarization making the
outer membrane surface more positive, which has
the reverse effect known as anelectrotonus
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20. Physiological effects of IDC
 A change in the concentration of ions at
the cell membrane when an electric
current is passed.
 The ionic concentration occurring at the
nerve membrane causes a muscle
contraction
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23.  Sensory nerve stimulation:
 Long pulse duration stimulates the
sensory nerve and cause stabbing or
burning sensation
 The sensory nerve irritation bring
about an increase in dilation of
superficial blood vessels which is
manifested in the form of erythema
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24. Motor nerve stimulation:
 Stimulation of motor nerve cause
contraction in the muscle (in form
of brisk twitches)
Denervated muscle stimulation:
 IDC of sufficiently long pulse
duration are required to produce
muscle twitches
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25. Hyperaemia
 Since this erythema is confined it indicates a
capillary hyperaemia unlike that due to heat in
which arteriolar dilatation occurs.
 The erythema causes vasomotor stimulation
and increased circulation may promote
improved nutrition of the area and speed up
the resolution of inflammatory products.
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27. USES
• THERAPEUTIC:
• MUSCLE STIMULATION
• PAIN REDUCTION
• EDEMA REDUCTION
• DIAGNOSTIC:
• testing the electrical activity of muscles.
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28. 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.
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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29. GENERAL TECHNIQUE OF APPLICATION FOR
IDC
• PREPARATION OF EQUIPMENT
• Select the apparatus that provides interrupted direct current
impulses.
• Check to see that:
– No current is leaking onto the casing.
– The polarity is marked.
– The duration of impulses and the frequency controls are available
as desired.
• The current output is smooth.
• Keep all controls at zero.
• Connect wire and electrodes.
• Select the appropriate probe, if used.
• Make appropriate size of indifferent electrode.
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30. PREPARATION OF PATIENT.
1. Have patient in an carefully selected position and that the position is
comfortable, the part is adequately supported.
2. Explain the patient in simple words about the treatment, its procedure
and what sensation he/she will experience.
3. Explain to the patient the characteristics of muscle twitches.
4. Warn the patient not to touch the machine and not to manipulate any
control, especially when both electrodes are tied to patients part.
Report any other sensation then explained.
5. Expose only the area to be treated, cover the rest of the body.
6. Inspect the skin, avoid stimulation where the skin has rashes.
7. Test skin sensation for “pin-prick”.
8. Wash the area with soap and water then dry and then soak the area
with warm saline for five minutes.
9. Place the indifferent electrode to appropriate area and secure with
bandage.
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31. TREATMENT.
1. Before switching on the mains and selector switch,
check to see that the intensity control is at zero.
2. Select the desired duration of impulse.
3. Set the repetition rate – frequency and rest periods.
4. Turn the main switch and selector switch on.
5. Place the probe near the motor point of the muscle.
6. Give a total of 90 to 120 contractions (twitches)
7. When all required muscles have been treated,
switch the apparatus and mains off. Remove the
indifferent electrode.
8. Clean the area and note skin reaction, if any.
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32. • FREQUENCY: 1 pps = twitch
• REST PERIOD: Usually 3-5 sec
• REPETITIONS: 90-120 REPS
• TIME DURATION: 20 -30mins
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