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  • The basics
  • Electrotherapy for pain: why use it?
  • Tracing a pain impulse
  • Blocking pain
  • Clinical Selection of waveforms and parameter settings
 
     
   
 
  • Transcutaneous Electrical Nerve Stimulation
  • Externally applied
  • For pain management
  • “Electric Analgesia”

TENS: How it All Started...
1967- Shealy et al used portable TENS devices to predict if patients with chronic pain would be good
candidates for surgically implanted dorsal column stimulators.

Patients in the trial reported effective pain relief with TENS and requested to continue using portable TENS rather than surgically implanted devices.

Does it work?
TENS has been proven to be an effective non-pharmacologic and non-invasive method of treating
Pain Can reduce the need for narcotic pain medication by 50%
( 1. Ghoname EA, et al. J Anesthesia and Analgesia. 1999:88:841-846.)
 
     
   
 
  • Difference in electrical charge between two sides of a membrane
  • Nerve cell:

        - Positive outside
        - Negative inside
 
     
   
 
  • Polarity reverses temporarily
    - Positive inside
    - Negative outside
 
     
   
 
  • Depolarization travels towards
    muscle and/or spine
  • Results in
    - Contraction
    - Sensation
 
     
   
     
   
 
 
     
   
 
 
     
   
 

Phase duration and Pulse Durations (µsec)

  • Amplitude (mA)
  • Frequency (pps or Hz)

Recruitment order

  • Sensory>Motor>Pain
 
     
   
 

The width of the electrical event is noted as either the phase duration or the pulse duration and is measured in microseconds (µsec). The width determines which nerve fibers are recruited optimally.

Note: In the above biphasic pulse, each phase duration is 100 µsec.
The pulse duration is the time from the beginning to the end of the pulse
(200 µsec).

 
     
   
 
Phase Duration Nerve Fibers that are Preferentially Recruited
20 - 100 usec

Sensory Nerves

  • large diameter A-beta nerve fibers that are hyperstimulated to over-ride pain
200 - 400 usec

Motor nerves

  • recruits large diameter A-alpha motor nerves necessary for muscle contraction
400 - 1000 usec

Pain carrying nerve fibers

  • Used in noxious electrotherapy protocols
  • Concept of “pain relieving pain”
 
     
   
 
  • Amplitude is commonly measured in milliAmps (mA)
  • Amplitude depicts the height of the electrical event
 
     
   
 

As current amplitude (intensity) is increased a greater depth of penetration is achieved; resulting in the recruitment of more sensory and motor nerves

Amplitude should always be dosed to a specific desired physiologic response, rather than a set number of milliAmps since the required current will vary from
application to application based on the resistance to current flow both in the patient and the electrodes

 
     
   
 
  • Frequency is the number of pulses delivered per second (pps or *Hz)
  • Frequency is adjusted to create desired physiologic responses based on the available electrophysiology research

* Hz = Hertz (cycles per second). Used to denote frequency when Alternating Current waveforms are used.

  
     
   
 
Application Recommended Frequency
Sensory Tens
(sensory level electroanalgesia)
 80 - 120 pps
Motor level Tens
(motor level electroanalgesia)		 2 - 4 pps
Noxious Tens 2-4 or 50 -150 pps
Neuromuscular electrical stimulation 30 - 75 pps

Note: When using Alternating Current, frequency is noted as Hertz (Hz)

 
     
   
 

Cycle is comprised of two phases deviating in opposite direction
from baseline.

Note: There is no space between the end of one cycle and the
beginning of the next. This is why it can not be called a pulse.
 
     
   
 
 
     
   
 

How do you choose a phase duration or a cycle duration for an AC Waveform?

Carrier Frequency Cycle Duration (AC term for pulse duration) Phase Duration
2000 Hz 500 uSec 250 uSec
2500 Hz 400 uSec 200 uSec
4000 Hz 250 uSec 125 uSec
5000 Hz 200 uSec 100 uSec

Note: The carrier frequency indirectly describes the Cycle and Phase Duration

  
     
   
 
  • Direct Current: Historically referred to as “Galvanic Current”
    involves the continuous or uninterrupted flow of charged particles.
  • Clinical applications
        - Iontophoresis
        - Stimulating denervated muscle
 
     
   
 

Various configurations of the 3 electrotherapy currents

Waveform Primary Clinical Applications
Interferential Pain Modulation
Premodulated Pain Modulation
Russian Muscle training, pain (noxious e-stim)
Biphasic Pain modulation, muscle training, *swelling
“VMS Muscle training, *swelling
High Volt Pulsed current Pain Modulation, prevention of edema formation, wound healing
Microcurrent ???? Tissue healing
Direct current Iontophoresis, denervated muscle

*Note: to reduce swelling muscle pumping contractions of ≥ 10% of maximal volitional contraction are recommended

  
     
   
 
Choosing a Waveform to meet your objective.

Concept: “the waveform is not the treatment”

  • We use waveforms to deliver a specific electrotherapy intervention
    (e.g. sensory level electroanalgesia)
  • Always choose treatment first than choose suitable waveform

 
 
     
   
 
  • What is pain?
  • What Physiologic and psychological effect does it have on our patients?
        - Inhibition of muscle
        - Lack of confidence, tentativeness, depression
        - Poorly managed acute
    pain can lead to chronic pain, chronic inhibition of mm, disuse atrophy and contracture
 
     
   
 

Tracing a Pain Impulse...

Source → peripheral nerve towards spinal cord → enters dorsal horn of spinal
cord → crosses to opposite side of spinal cord → ascends up spinal cord
(lateral spinal thalamic tract)→ thalmus → sensory cortex

 
     
   
 

Theories of pain control using electrotherapy

  • Gate Control Theory
  • Opiate-mediated Control
 
     
   
 
  • Melzak and Wall 19651, provided the physiological rational for electroanalgesia
  • Substantia Gelatinosa (“gate” in SC) controls nerve impulses to the brain. Only allow one impulse through at a time; like a gate.
         A-delta afferents “fast pain” 4-30 m/s
         C- fibers “slow pain” 0.5 -2 m/s
         A-beta afferents “pleasant/fast” 36-72 m/s

1. Melzack R, Wall PD. Pain Mechanisms: A New Theory. Science.
1965;150: 971-979.
asending model
(adapted from Denegar et al. Mod for Musculoskel injuries 2005)
 
     
   
 
  • Descending endogenous opiate system
  • Supraspinal pain modulation that produces a descending inhibition of pain chemically at the
    dorsal horn of the spinal cord
  • The spinal gate is closed from influence from above
  • The periductal gray matter secretes endogenous opiates in the blood plasma and cerebral spinal fluid


  • Chronic pain patients have been found to have below normal levels of endorphins in their cerebral spinal fluid
  • Endorphins have been shown to increase in the cerebral spinal fluid with twitch level electrical stimulation.
  • Goal of electrotherapy is to boost the levels of Endorphins in a patients

Opiate System

  • Peripheral sensory neurons (A) stimulate endorphin release (CNS)
  • Released endorphins stimulate descending neurons to spinal cord
  • These stimulate inhibitory spinal neurons

 
 
     
   
 
  • Bracket structure
  • Directly over the site of pain (most common)
  • Interferential: quad polar (4) electrode application.
    The Rx area should be bracketed in the center of the “X”.


Bi-polar placement
(2 electrodes)

Structure and Innervation

  • Major nerve root
  • Dermatome
  • Superficial peripheral nerve
  • Acupuncture and trigger points


Quad-polar placement
(4 electrodes)
 
     
   
 
Treatment Name Also Known As... Waveform Options
Sensory Level Electroanalgesia - High freq TENS
- Conventional TENS		 Biphasic, HVPC,
Premod, IFC
Motor Level Electroanalgesia - Low freq TENS
- Acupuncture like TENS - Twitch level stimulation		 Biphasic, Premod, IFC
Brief Intense TENS N/A Biphasic, Russian
High Intensity Noxious E-stim N/A Russian
(other waveforms can be substituted)
 
     
   
 

AKA: High frequency TENS or Conventional TENS

  • Indication: Acute Pain Management
  • Mechanism: Gate Control Theory (non-opiate)
  • Phase Duration: 50-100 microseconds
  • Frequency: >80 pps or sweep 80-120 pps
  • On/off time: none
  • Amplitude: strong comfortable tingling, no motor or pain response should be elicited
  • Duration of Rx: 20 min to hours
         - Amplitude, frequency or duration modulations can be used to minimize accommodation
  
     
   
 

(IFC or Premod waveform)

  • Indication: Acute Pain Management
  • Mechanism: Gate Control Theory
         - Carrier frequency: 4000 - 5000 HZ (often pre-programmed in machine)
         - Beat Frequency: >80 Hz or sweep 80-120 Hz
         - Amplitude: strong comfortable tingling, no motor or pain response should be elicited
         - Duration: 20 min to hours
         - Amplitude, frequency or duration modulations can be used to minimize accommodation
  
     
   
 
  • Gate control theory of pain modulation via hyperstimulation of A-beta nerves
  • Treatment of choice for acute conditions
  • Amplitude: increase to twitch and back off slightly
  • Literature reports short-term pain relief post Rx; longer-term pain relief may be experienced in instance where the pain-spasm cycle is interrupted
  • Waveforms: Biphasic (PC), *HVPC, IFC(AC), Premod (AC)

Note: *Highvolt Pulsed Current is also used to prevent the formation of edema.

  
     
   
 

“Twitch Level Stimulation”

  • Endorphins are released at a pulses rate range of 1 to 15 pps (approx.) Twitch level stimulation
  • Enkephalins are released at the higher pulse rates of 80 pps and up. Twitch level stimulation
  • Endorphin induced pain suppression lasts longer than pain suppression induced by enkephalins
  
     
   
 

AKA: Low frequency TENS, acupuncture Like TENS, Opiate induced electroanalgesis, twitch level stimulation

  • Indication: Chronic Pain
  • Mechanism: Opiate system
  • Phase Duration: ≥ 200 microseconds
  • Frequency: 2-4 pps
  • On/off time: None
  • Amplitude: Strong visible muscle contraction
  • Duration of treatment: Literature suggests 30- 45 minutes
  
     
   
  (Premod or IFC waveform)
  • Indication: Chronic Pain
  • Mechanism: Opiate system
  • Carrier frequency: 2000 – 5000 Hz (often pre-programmed in machine)
  • Beat Frequency: 2-4 Hz
  • On/off time: none
  • Intensity Level: Strong visible rhythmic muscle contraction
  • Duration: 30-45 minutes
  
     
   
 

Clinical Application Notes

  • Believed to reduce pain through the activation of endogenous opiates
  • The literature reports greater carry over of pain relief; up to several hours
  • Research suggests that stronger contractions produce greater analgesia
  • Not a good choice for acute injuries
  • Waveforms: biphasic,”VMS”, IFC (AC), and Premod (AC)
  
     
   
 
  • Type of Stimulator: Alternating Current unit (Russian)
  • Carrier Frequency: 2500 Hz
  • Frequency: 50 bursts / second
  • On / Off Time: 12 sec on / 8 seconds rest
  • Electrode Placement: Small electrodes (1x2cm) directly over the site of pain
  • Amplitude: maximum tolerable
  • Treatment time: 10-15 minutes

Clinical note: especially good clinical results for pain relief in chronic tendon injuries.

Muller et al J Orthop Sports Phys Ther. 2000;30:138-142.

  
     
   
  AKA: Hyperstimulation analgesia
  • Indication: Chronic Pain and Spasm
  • Phase Duration: > 300 microseconds
  • Frequency: 100-150 pps
  • Amplitude: Noxious with visible and palpable muscle contraction
  • On time: 10 -15 seconds
  • Off time: 4-7 seconds
  • Duration of Rx: 15-30 minutes

Clinical Application Notes

  • The high frequency (pps) and limited rest between contractions is believed to induce electrical fatigue of muscles in spasm
  • Since this is an aggressive treatment method, not all patients are candidates
  • Not indicated for acute injuries
  • Good clinical results for reduction of muscle spasm associated with LBP (opinion)
  
     
   
     
 
  • Cardiac pacemaker
  • Cardioverter defibrillator
  • Over the carotid sinus/anterior transcervical area
  • Over heart transthoracic area
  • Over the abdominal, lowback and pelvic area during pregnancy
  • Areas of venous or arterial thrombosis
  • Thrombophlebitis
  • Phrenic nerve or urinary bladder stimulator
  • Neoplasm (malignancy)
  • Superficial metal (e.g. staples, pins, external fixators)
  • Patients prone to seizures
  • Transcerebral stimulation
  • Stimulation over the eyes
  • Pain of unknown etiology
  
     
   
 
  • Utilize the continuum of electrotherapy treatments based on stage of healing
  • Sensory level electroanalgesia is indicated for acute pain management
  • Motor level analgesia is indicated for subacute and chronic pain management
  • Assess pain pre- and post-treatment to determine effectiveness of electrotherapy the intervention
 
     
   
 
  1. Sluka K. Am Pain Society. 2001;vol 11(2).
  2. Johnson M, Martinson M. Efficacy of electrical stimulation for chronic musculoskeletal pain: A meta-analysis of RCTs (2007), doi:1016/j.pain. .2007.02.007
  3. 3. Electrotherapy News (Tim Watson) Electrotherapyonline.co.uk
  4. 4. Belanger AY. Evidence Based Guide to Ther Phys Agents. Lippincott Williams & Wilkins, 2003.
 
     
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