USE OF PULSED ELECTROMAGNATIC ENERGY IN PHYSIOTHERAPY
Table of Contents
Introduction:
varying electromagnetic fields have been used by physiotherapist for many years for the thermal effects produced when they influence ions, dipoles and the molecules of insulators. short wave diathermy is claimed to be of benefit in treatment of many conditions such as osteoarthritis where the reduction of pain and increase in circulation is desirable. one of the major limitation in the use of short wave diathermy is that its thermal effect is greatest in fatty tissue and this limits the amount of energy which can be applied to the patient before thermal damage occurs.
beneficial effects can be produced when sub thermal dose of short wave is applied, thus promoting speculation that the electromegnetic field itself could influence tissue.
*Frequency:
this is 25 Hz through to 600 Hz with a varying number of intermediate steps.
*Pulse width
– 20 us is the shortest
– 40 ms is the largest
– more popular unit of pulse width 65 us.
*Power depth of penetration :
on some units this has to be controlled by adjustment of the frequency and pulse width. on others power controls exist which can vary the output for each pulse from 293 watts to 975 watts.
*Rest period
this depends upon the selected pulse width and frequency.for example ,if treatment is to be applied using pulse widths of 65 us at 600 Hz with a power of 975 watts, the rest period is 1600 us and the treatment/rest ratio is 1:25. the average power over the whole treatment period is only 38 watts, as the pilses of energy at 975 watts are spaced by long rest periods.
*Effects
the electrical potential across a normal cell membrane is maintained at around -60 to -90 millivolts due to the relative positions of ions on either side of the cell membrane. this potential may be as low as -40 mv in damaged cells and could have an adverse effect on the normal exchanges which occur across the cell membrane.
although the energy in a pulsed electromegnetic field is nowhere near the potential of the cell it is postulated that when applied to a damaged cell, this electromegnetic field might give the ‘push’ to start the system rolling , and thus allow the cell membrane potential to return to -60 mv.
this is an essential part of the repair process and a number of trials have been carried out which suggest that pulsed electromegnetic energy has a benificial effect on trauma and rate of repair.
*Containdication
pulsed electromegnetic fields are very safe as there is no danger of thermal injury, but caution should be exercised in the treatment of patients with cardiac pacemakers and pregnant women.
