Teaches by focusing the types of frequencys

1. Basic Concepts of Electrotherapy
Dr. Dheeraj Lamba
Associate Professor of Physical Therapy

2. General Principles of Electrical
Stimulation
• What is electrotherapy?
Electrotherapy is the use of different
electric currents (low frequency currents) to
the body to stimulate peripheral nervous
system to control pain, cause muscle
contraction or to speed healing.

3. timulate
General Consideration of Therapeutic
Currents
• The simple fact of electrotherapy is that all
currents used therapeutically are
transcutaneous electrical stimulation (TES),
or sometimes called transcutaneouselectrical
nerve stimulation (TENS) because they work
through skin to axcite nerve or s
muscle.

4. General Consideration of Therapeutic
Currents
• All stimulators must
provide sufficient
voltage in order to
conduct appropriate
current against the
impedance of the
conductive medium.

5. General Consideration of Therapeutic
Currents
• Most clinical stimulators are designed
electronically as either Constant-current or
Constant-voltage stimulator. Constant voltage
means that the voltage output level set by the
therapist will remain the same, if the impedance
of the tissue or of the tissue-electrode interface
or both are changed, the current will also
change but the voltage will remain constant.

6. General Consideration of Therapeutic
Currents
• Conversely, any change of impedance during
the application of a constant current stimulator
will change the voltage output but will leave the
current unaffected, provided that the stimulator
is appropriately designed to function in the full
range of tissue impedance.
• Basic physiological responses and clinical
results are most likely to be identical whether
constant- current or constant-voltage is used.

7. General Consideration of Therapeutic
Currents
• The clinical advantage of a constant-voltage
stimulator is the automatic reduction of current
when electrode size is reduced or if electrode
contact with the skin become loose.
• The disadvantage is apparent if the pressure
between the tissue and the electrode is suddenly
increased, impedance is reduced and current
amplitude is automatically increased.

8. General Consideration of Therapeutic
Currents
• The advantage of the constant-current is the
more consistent level of stimulation. The
disadvantage of the constant-current is apparent
when electrode size or pressure with the skin or
both is reduced and lead to a sudden increase of
current concentrations. The result is a sudden
discomfort of the stimulation and in extreme
cases, electrical burns.
• This hazard can be eliminated by limiting the
maximum voltage output.

9. Types of Electric Currents
• Therapeutically there are three types of
currents:
1- Direct current.

10. Types of Electric Currents
• Therapeutically there are three types of
currents:
2- Alternating current.

11. Types of Electric Currents
• Therapeutically there are three types of
currents:
3- Pulsed current.

12. Direct Current (DC)
• Direct current is the flow of electric charges
in one direction for 1 second or more.

13. Alternating Current (AC)
• Alternating current
(AC): is the continuous
bidirectional flow of
electric charge. An
electric current thatrises
to a maximum in one
direction, falls back to
zero and then rises to a
maximum in the
opposite direction and
then repeats.

14. Alternating Current (AC)
• In AC current there are inverse relationship
between frequency and pulse duration, as the
frequency increase the pulse duration decrease.
• Modulation of AC current:
Modulation of AC current is done by
modulating TIME or AMPLITUDE.

15. Alternating Current modulation
• The modulation by time
can be classified into
BURST and
INTERRUPTED modes.
1- Burst AC is created by
flow of current for a few
milliseconds and then
stop to flow (inter burst
interval or pause period)
and repeat cycle again.
The clinical example of
burst modulation is
Russian Current.

17. Alternating Current modulation
• Alternating current can also be modulated as
interrupted AC. This modulation done when
the current flow for few seconds then stop to
flow for 1 second or more. This interrupted AC
is differ from burst AC because the inter-pulse
interval is longer than the inter burst interval
and this is an advantage for the interrupted AC
because it permits relaxation from muscle
contraction.

18. Alternating Current modulation
• Amplitude Modulation:
the most common
example of amplitude
modulated AC is to mix
two AC current with
different frequency. This
is clinically known as
interferential current
(IFC).

20. 3- Pulsed Current (PC)
• A pulsed current is defined
as an electric current that is
conducted as signal (or
signals) of short duration.
Each pulse lasts for only a
few milliseconds (ms) or
microsecond (µsec) followed
by an interpulse interval. AC
has many names according
to waveform like pulsating
DC, square, faradic and
triangular.

21. 8AKAMGED ASYMMCTRIGAL
BfPHASIC WAVMFORM
B
a UOfiOPflA9f0 WhVCFORM

22. Parts of The Wave Form
• A wave form is a visual
shape of a pulsed
electrical current. It
include the following
components:
1- Amplitude: the
magnitude or intensity
of the current. Measured
in peak mA.
time

23. Parts of The Wave Form
2- Phase duration: the
time elapsed from the
beginning to the
termination of one
phase. Measured in
microsecond (µsec).
phase
duration
pulse phase

24. Parts of The Wave Form
3- Pulse duration (pulse
width): the time elapsed
from the beginning to
the end of all phases
plus the interphase
interval within one
pulse. Measured in
microsecond (µsec).
duration
phase
duration
duration
pulse phase

25. interpulse
interval
interphase
interval
Parts of The Wave Form
4- Interphase interval
(interpulse interval):
the time between two
successive
components of pulse
when no electrical
activity occurs.
Measured in
microsecond (µsec).

26. Parts of The Wave Form
5- Interpulse interval: thetime
between two successive
pulses.
6- pulse rate (frequency): the
number of pulses per
measure time (one second).
interpulse
interval

27. The role of rate change of the electric
pulse on physiologic changes
1- If there is very slow changes or even no
changes due to steady flow of ions (as in
unidirectional currents). This will cause
chemical changes at the electrode tissue
junction.

28. The role of rate change of the electric
pulse on physiologic changes
2-If the rate of changes is somewhat faster and
the pulse has a long enough duration, the ionic
balance across the excitable membrane is
disturbed stimulating nerves and muscles. If
the current is unidirectional it will lead to
chemical changes.

29. The role of rate change of the electric
pulse on physiologic changes
3-if the rate of changes is fast and the current is
alternating current no changes can occur
because any changes in one direction will be
cancelled when the current reversed.

30. The role of rate change of the electric
pulse on physiologic changes
4-if the rate of changes is very high there is
insufficient time for trans-membrane
excitation to occur so that much longer
currents can be employed which lead to
heating.

31. Rate of Rise of The Pulse
• If the rate of rise of the current is very slow it
will not provoke a nerve impulse because the
ionic balance across the nerve fiber membraneis
able to adjust itself, this process is called
accommodation.
• The rate at which accommodation occur is
limited so that the threshold may be reached by
the slow rising pulses at higher intensity. This
fact is used to discriminate between innervated
and denervated muscle.

32. The Role of Current Intensity on
Physiological Changes
• If we apply low current density (current
intensity /unit area²) to the skin, the nerves
transmit touch, temperature and pressure are
the first to be stimulated causing mild
tapping sensation.
• Higher current densities will affect more
sensory nerves causing tingling sensation.

33. The Role of Current Intensity on
Physiological Changes
• increase of current will affect more motor units
resulting in strong and wide As still higher
currents are applied the impulses will spread to
the motor nerves causing muscle contraction.
Further spread of muscle contraction.
• Much increase of current density will stimulate
pain fibers causing pain.

34. Stimulating Different Nerves
• The amplitude (intensity) of current needed to
stimulate a nerve fiber is inversely proportional
to its diameter. The larger fibers have a lower
electrical resistance.
• The difference in sensitivity between motor and
sensory fibers is due to their different depth;
sensory nerves in the skin receive higher current
density than deep motor fibers.

35. Stimulating Different Nerves
• From strength
duration curve you
can see that it easy
to excite sensory
and motor nerves
without eliciting
pain by using short
duration pulses say
around 0.05msec.

36. Questions ???????????????