low intensity current and short impulse applied largely for pain relief
stimulate a nerve across the skin
- uses biphasic current, although this is not often symmetrical
- the current is balanced- this helps prevent the accuulation of charge = decrease pts risk
- pusle duration or pulse width varies between 50 and 400 us
- current amplitude varies between 0.1 and 120 mA (milliamps)
What are the physiological effects of TENS?
- selective depolaristion of peripheral sensory, sensorimotor and sensorimotor nociceptive nerve fibres in the skin layers exposed to the ulsed current via surface electrodes positioned over the skin
Depolaristaion and AP
What is selective depolaristaion?
sensory fibres- using a combination of low currentamplitude and short pulse duration
- can be recognised if no mm contraction is apparent and the pt perceives the contraction as comfortable
sensroy motor and sensory motor nociceptive fibers- the combination of higher current amplitudes and longer pulse durations
- preferential stimulation of s-m fibres can be ascertained if an evoked mm contration is apparent either visually or on palpation and the level of sensation is still perceived as confortable
- preferential stimulation of s-m-n fibres can be identified if a mm contraction is clearly apparent and the pt describes the stimulation as tolerable, just below the threshold of being intolerable
- depending on stimulus depends on where the pain relief is
- spinal or supraspinal gating mechanism
- A beta helps prevent the pain in relation to delta
- A beta fibres are stimulated with short or long duration fibre. - TENS is used when certain pain is present. Can be used all the time for pain relief
- mm spasm TENS canbe used as it prevents the pain and the spams are helped to stop
- opioid system (in central and peripheral systems)- supraspinal level- uses neurons in the brain to secrete such as endorphines
- this inhibits the t cell transmission cell activity. Maxakin- used when in pain
- under 10Hz is better opiod relief
What are the 5 basic therapetic modes of TENS
- acupuncture like
- brief- intense- long duration, high frequency, tolerable amplitude. Intensity higher
- burst TENS- bursts of pilses- low frequency- comfortable amplitude
- modulation TENS- low frequency in a random manner. Not used much
What are the indications of TENS?
- well support
- acute and some neurogenic pains appear to produce better results than for chronic pain
- proved to be beneficial post op pain and obsterics
Positive results for TENS
- labour and post labour pain
- post abdominal surgery
- post thoracic surgery
- post stroke shoulder pain
- post herpetic nuralgia
- post orthopaedic surgery/ jt arthroplasty
- post cholecystectomy
- neck pain
What are the contraindications and precautions?
1. Ant transcervical area
2. Pharyngeal region- breathing and swallowing
3. Transthoracic- stimulate the heart and make the heart contract
4. Cardiac pacemakers- can affect pacemaker. Leg is safe
5. Insensitive skin: if it isnt going to cause a stimulus response- it wont work. Risk of burn high- cant feel stimulus
6 prenancy- back or belly
7. lotions on skin- ions in solution- concentration of chemicals around electrode- chemical burn
8. Inability to understand dangeers and instructions
- where pain is worse and percieved
- in the same dermatome, myotome, sclerotome
- trigger or acupuncutre points
- electrodes may be placed in the line of peripheral nerve where it is particular superficial. Such as shingles
- over spinal nerve roots close to vertebral column
The distance between electrodes affects the depth and course of the current. The closer together the electrodes are configured, the more superficial the current travels. The greater the distace between them, the deeper the current travel.
is a decrease in the frequency of AP and a decrease in the subjective senstation of stimulation while electrical stimulation is applied if there are no changes in the applied stimulus.
- caused by a decreased excitability of the nerve membrane with repeated stimulation
- conventional TENS is modulated to limit adaptation
Duration of the benefit
- it is variable
- studies have varied between 30 min to 4-7 hours depending
- johnson et al (1991) studied long 47% had ain reduced
- acupuncture- 4-5hr
- conventional 30 mins
What is the skin test for TENS?
- Sharp blunt discrimination test
- over area you put your electrodes
What is the warning for TENS?
When having electrical stimulation you should feel … [a ‘tingling’ sensation for sensory stimulation and/or muscle contraction if motor level stimulation is used]. If you feel anything other than this, or any pain or discomfort, you must call me immediately. Otherwise, you may risk skin and other tissue damage under the electrodes.
Please do not move or touch the equipment during treatment. If you become uncomfortable, call me.
Do you understand what I have said? Do you have any questions? Are you happy for me to proceed?