1. Therapeutic 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

5. ` 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

7. `
Pulse duration
Length of time that current is flowing in one cycle

8. `
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
Continuous modulation
amplitude of the current remains the same for several seconds or minutes
Interrupted modulation
current flows for some period of time called on-time & periodically turned off during off time
Burst modulation
occurs when pulsed current flows for a short duration & in a repetitive cycle
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. Classification of Currents
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Classification of Currents
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 ms
Frequency Hz
Produced by induction coil known as Faradic coil
Used for stimulation of innervated muscles
Each cycle consists of two unequal phases
Low intensity long duration currents
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. Modern Faradic current
Original Faradic current
Modern Faradic current

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