(Transcutaneous Electrical Nerve Stim) TENS for Pain Control

Bodychart Pain Drawing

VAS

Spadoni G et al. The Evaluation of Change in Pain Intensity: A Comparison of the P4 and Single-Item Numeric Pain Rating Scales. J Orthop Sports Phys Ther 2004;34:187-193.

Chung Faces Pain Rating Scale

THEORIES & MODELS OF PAIN CONTROL MECHANISMS

ASSUMPTIONS These concepts involve OVERLAPPING PROCESSES that occur normally Use these to better understand pain perception and as a rationale for your direct interventions for pain control

STIMULATION OF MECHANORECEPTORS Accomplished everyday by: Rubbing a painful area “Walking off” the pain Stimulation of mechanoreceptors should be at the same neurological level as the pain. Stimulation of A-beta fibers does control the pain to some degree, BUT HOW ????????

Endogenous Opiates Theories Key neurotransmitters are Enkephalin Endorphin Serotonin Substance P Binding of endogenous opiates to receptor sites inhibits transmission of “pain signals” to the brain.

Presynaptic Inhibition @ the Dorsal Horn (Gate Control)

Gate Control / Presynaptic Inhibition: Clinical Application Massage, heat, ice, pressure, exercise, stretching, manual therapy TENS : rapid stimulation of large afferents by using - High Frequency - Short Pulse Duration (width) - Sensory amplitude Called Conventional / High Freq TENS Ideal for acute pain

Descending Inhibition of pain via PAG & RN

Inhibition of pain by Endorphin (also decending)

Descending Inhibition & Endorphin: Clinical Application massage, ice, pressure (massage), exercise, manual therapy TENS - activate small afferents; A delta & C fibers - Low Frequency - Long (high) pulse duration - High Amplitude; uncomfortable Called Low Freq / Acupuncture-likeTENS Targets chronic pain

A word about COUNTER-IRRITANT CREAMS Old concept - “brain gives preference to most prominent sensations” Many creams & rubs such as Ben-Gay, Icy-Hot, Mineral Ice, Atomic Balm, Cramergesic, and many “liniments” are classified as “counterirritant creams”; but think about how the application and the active ingredients CAN TRIGGER pain control mechanisms. Word of caution

TENS Devices: Parameters you must master for HF & LF TENS Amplitude Frequency Duration / Width Modulations - to delay the onset of accommodation Electrode Placement Patient Instruction in home use

Examples of Current Modulations used by TENS units to delay accommodation Name them

Electrode Placement Rationales On & over the area of pain Surround the area of pain (pass e-stim thru the area of pain) Away from the site of pain but still depolarize the nerve(s) that supply the area of pain: Stim the peripheral nerve carrying the pain (IF the nerve is superficial & proximal to the pain) Stim within the same dermatome or myotome as the area of pain. Stim the nerve plexus carrying pain stimulus (rare & only possible at brachial plexus) Acupuncture Points   

TENS for Pain: Knowledge you must convey Sensory fibers activated Pain control theories utilized Timeframe for pain control Treatment time Applicable to what type of pain?

Sampling of Evidence on TENS

Variation and Inconclusiveness Efficacy: Mixed results in research have occurred due to several factors, such as waveform type, frequency, pulse rate, intensity, electrode placement, treatment time, outcome measures (pain), systematic vs individualized Rx.