TENS 2 Flashcards
What is TENS
TENS is a method of electrical stimulation which primarily aims to provide a degree of symptomatic pain relief by exciting sensory nerves and thereby stimulating either the pain gate mechanism and/or the opioid system.
Acute Tens
- Assymetrical Biphasic waveform 2. Pulse Frequency: 80 – 150 Hz
- Pulse Width:
- Intensity: pt tolerance (0-80)
- Duration: (30-40mins)
- Electrode placement: either side of pain
• Pretesting: Sharp / dull patient test Machine output test
- Tell me about the Pain Gate Theory
Involves activation (excitation) of the A beta (A,B) sensory fibres, and by doing so reduces noxious stimulus from the 'c' fibres, through the spinal cord and hence to higher centres. The AB fibres appear to appreciate being stimulated at a relatively high rate (80-130 hz or pps) -clinically its important to enable patients to find tehir optimal treatment frequency- varies between individuals. -setting machine and telling patients whats what aint gonna work that greta.
- Opoid Mechanism
There isnt a single frequency that works best for everyone.
- more for chronic pain
- use as long as required
- typically 1-2 hrs on followed by 1-2 hrs off
- lower frequency 2-4 Hz
- A definite strong sensation
- Both Types?
Use a BURST mode stimulation Typically involves higher frequency
stimulation ( 100Hz)
2 – 3 bursts per second
When the machine is “on” pulses at 100 Hz trigger the Aβ or pain gate
Bursts trigger the Aδ thus opioid mechanism
Patients find it less tolerable as more a “grabbing” or “clawing” type sensation
Hints on TENS
Vary the frequency for optimal results
• Stimulation intensity works best when the patient says something to the effect of “definitely there but not painful”.
Precautions to TENS
If there is abnormal skin sensation, the electrodes should preferably be positioned elsewhere to ensure effective stimulation
Electrodes should not be placed over the eyes
Patients who have epilepsy should be tx by therapist with a GP as anecdotal reports of adverse outcomes, most especially (but not exclusively) associated with treatments to the neck and upper thoracic areas
Avoid active epiphyseal regions in children (though there is no direct evidence of adverse effect)
The use of abdominal electrodes during labour may interfere with foetal monitoring equipment and is therefore best avoided
Contraindications of TENS
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Electrical stimulation can be used to help?
Electrical stimulation can be used to help retrain the neuromuscular function that is lost from arthrogenic muscle inhibition after injury or surgery.
• The muscular inhibition that results from injury needs to be overcome before the patient can participate in active rehabilitation.
• The goal of the treatment is to elicit a strong muscle contraction through stimulating the alpha motor neuron.
• The injured individual is taught to contract the muscle with the stimulation to overcome the natural inhibition.
NMES can also be used to prevent disuse atrophy of muscles but should not be applied following unstable acute fractures.
Muscle Strength Vs Force Capacity Enhancement
For strength to increase merely through utilization of electrical stimulation, the stimulation must be as great as a similar overload imposed in the form of exercise. This level of electrical stimulation is rarely tolerable.
If there is inhibition of a muscle from effusion or prolonged immobilisation, electrical stimulation can be used to help teach the athlete to contract the muscle. Thus, the force capacity or ability of the muscle to contract is enhanced.
• Electrical muscle stimulation always occurs through the motor nerve whenever the peripheral nerve is intact.
Fatigue and NMES
In order to reduce fatigue with electrical stimulation, a duty cycle or rest time must be imposed.
• Generally, a 1:5 on-to-off time is required to allow enough time to regenerate the local energy utilised for the contraction.
The phosphocreatine energy system is depleted rapidly (in 10-15 sec) and requires 30 sec to 1 min to replace.
The rest time allows quality contractions to be produced throughout the treatment.
• Generally a 10 sec contraction is followed by a 40 to 50 sec rest time.
• As the athlete accommodates to the overload (after 1 to 2 weeks of training), the rest time can be reduced to 30 sec.
• Because of muscle fatigue, the duty cycle is probably the most important feature of a neuromuscular stimulator.
• To increase strength shorter contractions should be applied, to increase endurance longer contractions should be applied
What are the parameters for NMES
slide 22 onward
EMG- when do you use it?
Once the patient is able to contract the muscle on their own you can use EMG (electromyographic) biofeedback to assist in restoring voluntary control and help physically active individuals regain control of muscle contractions and transition to functional activities..
EMG can also be used to correct muscle imbalances by providing feedback for the patient regarding the muscle they are using eg VMO training.
Direct stimulation of Denervated Muscle
Once the aplpha motor neurons impulses are disrupted the muscles it supplies becomes de-innervated.
- alpha motor neurons are able to regenerate but occur slowly.
- Electrical stimulation can be used to prevent atrophy and maintain muscle function.
- A low frequency AC or DC current must be applied to overcome the capacitance of the muscle.
Iontophoresis
Iontophoresis is the process in which ions in solution are transferred through the intact skin via an electrical potential.
• It is based on the electrical principle that “like” charges are repelled.
• A DC generator is required as other monophasic stimulators do not have phase durations that are long enough.
- Iontophoresis is useful for chronic inflammation
- Specially made electrodes contain the medication.
- Iontophoresis requires the ions to be in a water soluble substance. This causes a change in pH when an electrical current is passed through the water and can result in burns to the skin.
- Electrodes which contain the medicine and a buffering solution prevent the change in pH.
