TENS

A.THANGAMANI RAMALINGAMPT, MSc (PSY), MIAP

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. The different methods of applying TENS relate to these different physiological mechanisms

Transcutaneous Electrical Neuromuscular Stimulation

Pain control treatment Can cause muscle contractions, but that is not

why it is used Decreases patient’s pain perception by

decreasing the conductivity & transmission of noxious impulses from small pain fibers (effects large diameter fibers)

Moderate caffeine levels (200 mg, approx 2-3 c. coffee) may decrease effectiveness of TENS

What is pain?

“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” ISAP (1979)

DEFINITION Pain is a noxious unwanted perception in

which the patient seeks medical intervention. “Pain is subjective, individual and modified

by degrees of attention, emotional state and the conditioning of past experiences.” (Livingstone 1943). The intensity of the pain is not directly proportional to the degree of suffering. Because it is basically a psychological experience and depends on how it is interpreted or experienced

TYPES Acute pain – shorter duration up to six months

Acute monophonic pain Recurrent acute non-malignant pain

Chronic pain – longer duration > six months Chronic malignant pain - progressive Intractable-benign Chronic pain associated with non-malignancy disease –

identifiable pathology Chronic non-malignant pain syndrome Recurrent acute – migraine

Chronic and acute pain may have different causes – behavioral factors may be involved in acute pain

PAIN RECEPTORS

How do we experience pain? Specificity theory – Desecrates

posits that there are specific sensory receptors for different types of sensations (i.e., pain, touch, pressure)

Pattern theory – Melzack & Wall (1982) posits that pain results from the type of stimulation received by the

nerve ending and the key determination of pain is the intensity of the stimulation

Both theories have limitations pain can be experienced without tissue damage tissue damage can occur without pain being felt Phantom limb pain experience not accounted for by the theories –

Fordyce (1988) study of amputees

PHYSIOLOGY OF PAIN

Receptors

A fibers – Localized and quick type of pain C

fibers – Slow acting type of pain(Peripheral

Nervous System)Spinal Cord (Substantia

Gelatinosa)

Spinothalamic Tracts (Lateral / Anterior)

Thalamus

Cerebral Cortex (Somatosensory Cortex)

Influenced by Limbic system & Reticular formation

Gate Control Theory

Gate control theory – Melzack & Wall (1965) severity of pain sensation determined by balance between

excitatory and inhibitory inputs to T cells in spinal cord C & A-delta nociceptor afferents give excitatory input to dorsal root

ganglion of spinal cord– A-delta (myelinated) about 40 mph and C fibers (unmyelinated) about 3 mph, other sensory information travels at about 180 -240 mph

Substantia gelatinosa, large diameter A-beta non-nociceptor afferents give inhibitory input

Increased firing of non-nociceptor afferents causes presynaptic inhibition of T cells and the spinal gate from excitatory cells to the brain is closed. –

Physical agent modalities and physical activities believed to close the gate by activating the non-nociceptor afferents

The theory does not explain pain modulation descending from brain

Central Control Mechanisms of Pain

Not well understood Periaqueductral gray seems to be

involved in pain – electrical stimulation can block the experience of pain

Spinothalamic tract which carries the impulses up the spinal cord, through the brain stem to the thalamus

Cerebral cortex sensory area of parietal lobe: localization

and interpretation of pain - somatosensory cortex

limbic system: affective and autonomic response

temporal lobe: pain memory

The same part of the brain – the anterior cingulate cortex – responds to physical and emotional pain.

Where is pain in the brain?

Chemical processes involved in pain

Substance P Chemical mediator thought

to be involved with transmission of pain.Associated with inflammatory painIt excites pain transmitting

neurons when releasedIts mechanism is not fully

understood Glutamate – release affects

amount of pain experienced

Prostaglandins, bradykinin – released when tissue damaged

Chemical processes involved in pain Endorphins

Pain perception modulated by these opiate like neurotransmitters

The endorphins bind to certain sites on the nervous system including peripheral nerves

They suppress pain transmission at the spinal cord level by inhibiting the release of the neurotransmitter gamma aminobutyric acid (GABA) in the periaqueductal gray matter (PAGM) and raphe nucleus of the brain

High concentration of opiate receptors in limbic area of brain explains the stress relief and euphoria associated with opiates

Limbic system involved with emotional component of pain

Tens&parameters

Conventional tens

acupunturetens

Brief intense tens

Rapid pain relief 15-30minutes High frequency& more pulse width

Burstmode of conventional tens

Stimulation of appropriate nerve root(s) Stimulate the peripheral nerve (best if

proximal to the pain area) Stimulate motor point (innervated by the

same root level) Stimulate trigger point(s) or acupuncture

point(s) Stimulate the appropriate dermatome,

myotome or sclerotome

PRINCIPLES OF APPLICATION

RECEIVING THE PATIENT

Introduce yourself to patient

Give assurance/confidence

Case sheet reading

Go through the medical reports Find out diagnosis/general contra-

indications/previous physiotherapy treatment

Checking general contraindications

Hyper pyrexia Epilepsy Severe renal and cardiac problems Severe hypo/hypertension Cardiac pacemakers Infections Pregnant women Metal implants Mentally retarded/upset patients Malignancy Anterior aspect of neck/carotid sinus/eyes

Tray preparations

Skin resistance lowering/testing tray

Pillows Cotton Soap Towel Mackintosh Petroleum jelly Test tubes ( hot &cold) U-pin (sharp &blunt) Clips Bowl of water IR lamp Hot &cold packs

Treatment tray Pillows Towel Bed sheet Cotton Adhesive tapes Straps/goggles Salt/Powder Scissor/ Inch tape Paper Graph paper Pencil/scale/eraser Machine& accessories Sand bags/crepe bandages

Checking local contraindications

Open wounds Scars Local skin infections Cuts Abrasions Eczema Local hemorrhagic spots Skin sensitivity (testing)

Apparatus preparation

Check the apparatus& accessories like electrodes, leads, cables, plugs, power sockets, switches, controls, dials and others

Apparatus checking

Demonstration of the treatment Check the functioning of machine in

front of the patient Explanation of treatment

Positioning the patient

Comfortable Relaxed appropriate

Skin resistance lowering

Do skin resistance lowering Neatly &perfectly Use items required in an orderly manner

Selection of technique

Use proper technique of application

Placement of electrodes

Appropriate placement according to the condition &patient

Use adhesives &straps Apply gel evenly on electrode Maintain good contact with the skin No leads crossing each other Confirm connections &above all

Instructions & warnings

Instructions Don’t move Don’t sleep Don’t touch leads,

apparatus, therapist and any other metal near by you

Warnings Inform more

heating/uncomfortable sensations

Inform burning sensation immediately

Treatment

Proper execution of treatment Appropriate intensity should be used Set duration of treatment acc. to

condition status Supervise the treatment through out the

session

Termination

Put knobs to zero Remove electrodes Switch off the machine &mains Clean the area &inspect for adverse

reactions Manage if anything &give instruction

regarding next coming Winding up procedure

Recording

Accurate record of all parameters of treatment including area treated , technique, dosage and the outcomes

CONTRAINDICATIONS Patients who do not comprehend the physiotherapist’s instructions or

who are unable to co-operate • It has been widely cited that application of the electrodes over the trunk,

abdomen or pelvis during pregnancy is contraindicated BUT a recent review suggests that although not an ideal (first line) treatment option, application of TENS around the trunk during pregnancy can be safely applied, and no detrimental effects have been reported in the literature (see www.electrotherapy,org for publication details)

• TENS during labour for pain relief is both safe and effective • Patients with a Pacemaker should not be routinely treated with TENS

though under carefully controlled conditions it can be safely applied. It is suggested that routine application of TENS for a patient with a pacemaker or any other implanted electronic device should be considered a contraindication.

• Patients who have an allergic response to the electrodes, gel or tape • Electrode placement over dermatological lesions e.g. dermatitis,

eczema • Application over the anterior aspect of the neck or carotid sinus

PRECAUTIONS

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 treated at the discretion

of the therapist in consultation with the appropriate medical practitioner as there have been 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