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High voltage Galvanic stimulation or high
voltage pulsed Galvanic stimulation:
- This form of currents was originally
developed in the USA and given this name. That twin pulse waveform has almost
instantaneous arises with exponential Falls.
HVPGS PARAMETERS: - The pair of pulses last for only
0.1 millisecond and each peak lasts for only few microseconds; the shape and
duration are normally fixed.
- The frequency of the double pulse can be varied
usually from 2 - 100Hz. With search shorts peaks very high voltages are
needed to provide enough currents to stimulate nerve fibers.
- Peak currents of
2 - 2.5A maybe generated during the few microseconds of peak voltage, but of
course the total average current is very low at around 1.2 to 1.5 milliamp.
- Such pulsed current will pass easily through
the tissues, because they are so brief and will be relatively comfortable due
to their wide discrimination between sensory, motor and nociceptor nerve
fibers.
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HVPGS GENERATOR: - As well as the frequency the intensity can
be varies 0 to 500 volts and the polarity altered.
- The pattern of currents
can be changed by mode switch. In continuous mode the train of Twin pulses is
delivered continuously.
- Reciprocate mode refers to the alternate application
of trains of pulses to one or other of to active pads and does not mean
that's the current direction is reversed.
- Surge mode gives a train of pulses.
A meter to indicate peak currents may be provided. On some machines the
interval between the two peaks may be altered; this is called the interpulse
interval.
- The current is applied by flexible electrodes and sponges. The
electrodes are usually small and are sometimes mounted on a handle.
Various special electrodes are available.
Uses of HVPGS:
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Wound healing:
- Since a direct current albeit of very
low total intensity is being applied. There seems to be e evidence that
low-intensity currents lead to tissue healing.
Muscle stimulation:
- HVPGS is used for the stimulation of
innervated muscle and due to the short pulses and hence good transmission
in the tissues it is an efficient way of doing so.
- Consider the
strength duration curve which shows that short pulses at high intensities
will be more selective insulating motor, rather than pain nerves. HVPGS has
therefore been used for muscle strengthening and the reduction of disuse
atrophy of innervated muscle.
- Frequency of around 30 Hz has been
suggested with long intervals between bouts of tetanic contraction as the
optimum schedule.
Pain modulation:
- How pain may controlled by electrical
stimulation already been discussed since both the frequency and intensity
of HVPGS can be controlled it is possible to apply both high frequency,
low frequency stimulation for pain gate control and low frequency high
frequency stimulation for encephalin type pain control.
- HVPGS has been
recommended for controlling all kinds of pain success acute chronic
neurogenic and pain from many sources.
Other uses:
- Effects on vascular system are claimed
in that rhythmical muscle contraction and relaxation due to HVPGS of
motor nerves will have a pumping effects, increasing blood flow in muscle
and surrounding tissues as considered earlier.
- This effects can aid in
the relation of tissue edema. Fish et al found that anodal high voltage
pulsed current did not curb edema formation in frog Hind Limbs.
- This
contrast markedly with significant treatment effects found with cathodal
HVPGS. Direct effects on autonomic nerve leading to local vasodilation
increasing fluid exchange in the tissues and other beneficial effects
have been claimed.
- Consequent upon its ability to stimulate innervated
muscle HVPGS has been recommended in the treatment of muscle spasm and to
increase joint mobility.
- Some uncertainty exist over the advantages of
the Twin peaks waveform which is what makes this current unique. It has
been suggested that's a single pulse could be just as effective.
THOSE ABOVE ARE COLLECTED FROM SOME BOOKS AND
WEBSITES..
THANK YOU,
SRIKUMARAN PHYSIOTHERAPY CLINIC & FITNESS CENTER |
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