The controls
The amplitude, pulse rate, pulse width and the mode selectors operate independently of each other, but interact to give pain control which is unique to TENS. As individual pain syndromes differ, the controls are adjusted by the patient to a setting which gives him/her optimal comfort and pain relief. There is no benefit in painful stimulation.
The amplitude
The amplitude controls the intensity and the depth of the pulse. The higher the amplitude, the higher the pulse peak and the stronger the pulse. If the unit is to be used on areas of scar tissue or thick skin density, test that, the amplitude is strong enough to penetrate the adipose tissue and cause sufficient stimulation.Low frequency TENS (usually hand held types) have an amplitude range between 0 and 10 milliamp (m.A.). High frequency TENS units range will usually 24 be between 0-100 m.A. Units using NiCad batteries may give out slightly less amplitude.
The pulse width control
The pulse width control governs the width of the pulses. The wider the pulse width the deeper the stimulation. The narrower the pulse width the more shallow the stimulation. Basically, large areas of deep pain require wide pulse widths between 120-200 US, shallow surface pain is best treated with narrow pulse widths between 40-120 US.
A comfortable sensation covering the injured area is the main purpose of the pulse width control. As each patient is an individual with different skin thicknesses and tolerance to pain etc., it is often a matter of trial and error in selecting the optimal pulse width control.
The above instructions are general as pulse width specifications will vary according to the type of TENS selected. Refer to your instruction manual or health practitioner for further specific details.
The Pulse Rate
This controls the number of pulses emitted through the electrodes to the skin. The pulse rate is also referred to as:
1. Frequency.
2. Cycles per second (c.p.s.).
3. Pulses per second (p.p.s.).
A Hertz is a unit of frequency equal to one pulse per second, e.g. 50 Hertz=50 p.p.s.
Which pulse rate (Hertz) should I select?
As a guide, high pulse rates are used for blocking pain (sedation) and low pulse rates are used for treating pain (tonification). Some machines can only be used for chronic pain syndromes, i.e. their range is not high enough to block acute pain signals. Hertz range is a major deciding factor in the selection of TENS.
30 Hertz
Hand-held TENS units have a minimum of 1 Hertz and maximum of 30 Hertz. The extra low frequency has proved to be the most successful in the treatment of arthritic-type pains. The lower the frequency used, the longer the pain relief fasts. This unit is used for chronic pain syndromes.
200 Hertz
Most home use (Walkman type) TENS units will have a pulse rate control within the 1-200 pps range. This has been found to be more than sufficient for most acute and chronic pain syndromes.
500 Hertz
Units with maximum pulse rates of between 1-500 Hertz are initially used with clinical supervision for difficult to treat pain syndromes such as cancer. Many hospitals and clinics are using extra high frequencies for childbirths, dental, post-operative and post-surgical pain. Units with this range can also be used for all pain syndromes by the lay person with very little training.
1000 Hertz
Units on a fixed frequency cycle range of 1000 Hertz or more are mainly used for chemical addictions such as opium, morphine, alcohol, prescribed medicine addictions and nicotine. These machines should be used initially under professional supervision.
Mode selectors
The mode selector is used to alter the sequence of stimulation from a regular conventional continuous waveform, to an irregular one. A conventional TENS ha only one waveform conventional. More sophisticated TENS have a variety mode selectors — burst, modulation and conventional. The wave forms are dialled up automatically by the mode selector control.
A TENS with a selection of waveforms is useful for a patient whose body has adapted itself to the conventional waveform and thus the efficacy of the treatment is reduced. Some patients find switching to burst or modulation mode gives longer pain relief due to the regenerative effect these two waveforms have on the endogenous opiate system.
Some waveforms will provide better pain relief than others. Selection is usually done on a trial and error basis by the patient in the comfort of his own home and at his own pace. The patient will progressively find the waveform which gives him the most pain relief. Try each waveform for at least one day before changing to another as sometimes the beneficial effects are not experienced until treatment has ceased
Conventional waveforms
Conventional waveforms are also known as square or normal waveforms. They are continuous wide-ramped waveforms which emulate a natural muscle movement. Most patients prefer the comfort of the square waveform to start off with as there are no sudden ‘spikes’ of contraction. For acute and chronic pain syndromes.
On conventional TENS units the waveform is fixed by the frequency pulse rate control.
Burst waveform
This is a narrow spiky waveform which consists of approximately seven bursts which are interrupted every 1-3 seconds for a period of 1-3 seconds. The low frequency and fixed pulse width of burst mode increases the tolerance factor for patients using the stimulator for extended periods. For chronic pain syndromes.
Modulation waveform
Modulation waveform automatically varies between wide and narrow in regular cycles. Whilst one waveform is increasing the other is decreasing. This mixed mode provides variation for acute and chronic pain syndromes which may have become accommodated to the conventional waveform.
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