Therapatic Currents

2. Different Wave Forms
Wave form means
Graphical representation of the direction, shape, amplitude, &
pulse
A pulse may contain either one or two phases
It rise above or goes below the base line for some specific
period of time
Direct current/mono phasic current
Have only single phase
Current flow in unidirectional
Flow in same direction towards positive or negative pole
Alternating current/biphasic current
Have two separate phases
Current flow is bi directional
Wave form may be symmetrical or asymmetrical

4. Wave form shape
Could be of any type like sine, rectangular or triangular
Depends on the capabilities of the generator

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Pulse amplitude
Magnitude of current
The peak current is the maximum amplitude of the current
Maximum amplitude of pulse can be shown by tip of highest
point of each phase

6. `
Pulse frequency
Number of pulses per second
As frequency of wave form is increased the amplitude
tends to increase & decrease more rapidly

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Pulse duration
Length of time that current is flowing in one cycle

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Current Modulation
Physiologic response to various wave forms mainly depend on current
modulation
Modulation refers to any alteration in the magnitude or any variation in the
duration of the pulses
1. Continuous modulation
amplitude of the current remains the same for several seconds or minutes
2. Interrupted modulation
current flows for some period of time called on-time & periodically turned
off during off time
3. Burst modulation
occurs when pulsed current flows for a short duration & in a repetitive
cycle
4. Ramping modulation
also called surging modulation
current increases gradually or decreases gradually in its intensity

9. Surging of current
The intensity of each successive pulse gradually increases
Each impulse reaches to higher intensity than that of
preceding one
After the peak levels either falls suddenly or gradually

10. 555
Classification of Currents
a. On the basis of direction of flow of current
• Alternating current: flow in both direction
• Direct current: flow in one direction
b. On the basis of frequency
• Low frequency: range of 50 to 100 Hz
e.g. IDC, Faradic, galvanic, sinusoidal, TENS
• Medium frequency: range of 100 to 4000
e.g. interferential currents
• High frequency currents: frequency more than 1MHz
e.g. SWD, MWD, UST
c. On the basis of voltage
• Low voltage currents: less than100 Volt
• High voltage currents: greater than 100 volt
d. On the basis of amperage
low amperage currents: 1 to30 mAmp e.g.- high TENS
high amperage currents: 500 to2000 mAmp

11. Interrupted Direct Currents (Galvenic
Current)
•Interruption is the most useful modification of direct current
•It makes the flow of current commence & cease at regular
intervals
•Rise & fall of intensity may be
sudden- rectangular
gradual-trapezoidal, triangular, saw tooth
•Commonly used for stimulation of denervated muscles & electro
diagnosis purpose
•Impulse duration & frequency can be adjusted
•Duration of 100ms commonly used
•Impulse duration ranges between 0.01 to 300 msec
•Frequency vary as per the pulse duration & interval selected
e.g- pulse duration 100msec requires frequency of 30 per min

12. Shape of the pulsed
waves
– Monophasic
• Rectangular pulses
• Trapezoidal pulses
• Triangular pulses
• Saw tooth pulses
– Biphasic: risk of skin damage
is less with balanced pulses
(chemical reactions taking
place are reversed)
Slow rising wave forms can be used because muscle has less
ability to accommodate than nerves.

13. Rectangular pulses have sudden rise where as others
like trapezoidal, triangular & was tooth have gradual
rise
The impulses in which current rises gradually are
often termed “selective”
A contraction of denervated muscle can often
produced with an intensity of current that is sufficient
to stimulate motor nerves because accommodation
occurs

14. Selection of impulses
Rectangular impulse is capable of producing muscle
contraction but selective impulse is always satisfactory
With rectangular impulses rise is sudden where as with
trapezoidal it is slow, with triangular even slower & with saw
tooth still slower
A low intensity & gradual rise is often best for stimulation
of denervated muscle as it brings about satisfactory
contraction with less sensory stimulation than with
rectangular impulses
Proper selection of current leads to eliminate unwanted
contraction of innervated muscles present in closes proximity
In long standing denervation a muscle contraction may be
obtained with a slowly rising current when there no longer
response to rectangular impulse

15. Faradic Type Currents
Short duration interrupted direct current
Pulse duration 0.1-1 ms
Frequency 50-100 Hz
Produced by induction coil known as Faradic coil
Used for stimulation of innervated muscles
Each cycle consists of two unequal phases
1. Low intensity long duration currents
2. High intensity short duration currents
Faradic coils are now being replaced by electronic stimulators
They almost have same physiological effect, but differs in wave
form

17. Modified Faradic Currents
•Faradic current can be interrupted at regular intervals to avoid
fatigue of muscles
•For better result in treatment faradic current is surged to produce a
near normal tetanic like contraction & relaxation of muscle
•The apparatus should have sufficient control to surge the current
•In original Faradic coils current was surged by hand but in modern
stimulators an electronic an electronic device is used
•The circuit can be modified to give surges of various durations,
frequencies & wave forms
•Various forms of surges are trapezoidal, triangular,, saw tooth etc.

18. Original Faradic current
Modern Faradic current

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