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Phys Agents > IFC and Tens > Flashcards

IFC and Tens Flashcards

1
Q

General Overview of IFC and TENS

A

TENS and IFC use electric currents to stimulate peripheral nerves resulting in short-term pain relief (minutes to hours)

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2
Q

What is pain?

A

Unpleasant sensory and emotional experience associated with actual or potential tissue damage (acute-new to 3 months, persistent, chronic – synonymous with persistent)

Nociceptive input neither sufficient nor required

Ex: Nail in head vs paper cut

PERCEPTION

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3
Q

What is the biggest nerve type?

A

A Alpha Fibers

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4
Q

Ia afferent (Aa)

A

Myelinated: Yes
Conduction Velocity: 70-120 m/s
Specialized Ending: Muscle Spindle
Receptor Location: Skeletal Muscle
Sensory Function: Joint position/Movement

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5
Q

1b afferent (Aa)

A

Myelinated: Yes
Conduction Velocity: 70-120 m/s
Specialized Ending: GTO
Receptor Location: Musculotendinous junction
Sensory Function: Muscle Contraction Force

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6
Q

II afferent (AB)

A

Myelinated: Yes
Conduction Velocity: 25-70 m/s
Specialized Ending: Touch Receptors, Joint Receptors, Muscle Spindle Secondary
Receptor Location: Skin, Joint Capsule, Skeletal Muscle
Sensory Function: Touch/Pressure, Joint position/movement, Joint Position

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7
Q

What are the areas of the body process pain?

A

Dorsal Horn in Spine and Brain
- Each location can cause for the signal to turn up or turn down
- Brain is the only thing that can indicate pain.

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8
Q

Two mechanisms of pain inhibition we use clinically

A

Gate theory control (local spinal cord level)

Descending Pain Control (both supraspinal and spinal level – can be more systemic)
- Indigenous Opioids
- Internal NTs

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9
Q

Pain Gate Theory

A

Two sub-mechanisms:
- Basic mechanism: Highway analogy – explains temperature effects on pain perception: more temp sense = less “pain” sense
- Synaptic inhibition - explains effects of touch on pain (puscinian corpuscle, etc.)

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10
Q

Pain Gate Theory - Highway Analogy

A
  • Temperature effects on pain perception: more temp sense = less “pain” sense
  • Sensation and Nociception both carry Delta A and C (Travel into **spinal cord **at dorsal root ganglion at synapse)
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11
Q

Pain Gate Theory - Synaptic inhibition

A
  1. Stimulation of other receptors causes transmission on AB axons
  2. At spinal level, AB axons excite an interneuron which then inhibits the transmission of nociception in the spinothalamic tract (with the Delta A and C fibers)
  3. There are various types of inhibition and neurochemicals involved (pre- and post-synapse, GABA and Enkephalin, and probably others)
    - Pain system is complex
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12
Q

Pain Gate Theory occurs….

A

locally at the levels of the spinal cord involved with peripheral stimuli

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13
Q

Descending Pain Control

A

(Endogenous Opiate System)
Two systems operate at supraspinal level to impact:
1. Involved spinal cord level through neural connections from the periaqueductal gray (PAG) and Raphe Nucleus
2. General Systemic Effects

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14
Q

Involved spinal cord level through neural connections from the periaqueductal gray (PAG) and Raphe Nucleus

A

(Both in midbrain and have direct connections in spinal cord; in the spinal cord where it ends releases release enkephalins, norepinephrine, serotonin – inhibition effects)

Ex: Stub toe, this system kicks in to dull pain. Kick in a minute or two after initial stub of toe.

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15
Q

General Systemic Effects - Descending Pain Control

A

Hypothalamus and Pituitary
1. Beta Endorphin and Dynorphin (Dumped in blood)
a. Widespread release through CNS and circulatory system – explains the classic exercise pain inhibition or “runner’s high”
b. One of the best ways to stimulate this is through exercise

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16
Q

Endogenous Opiate System

A

Works locally and systemically

These mechanisms work together and simultaneously, HOWEVER, it is convenient to conceptualize them as being recruited progressively as the pain experience intensifies or persists

Longer half life

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17
Q

Other mechanisms involved in pain modulation – Placebo Response

A

Symptom improvement based on expectation, a possibility with any intervention

For E-stim, reported as high as 30-40% of the response

Response can be blocked by Naloxone, and opiate anatagonist meaning placebo is a neurophysiologic response!

18
Q

Other mechanisms of pain modulation with E-stim Vasodilation

A

Areas of myofascial pain (trigger points) may be ischemic, contributing to pain experience

Electrical stimulation induces local vasodilation in patients with myofascial symptoms

Vasodilation may reduce ischemic pain

19
Q

Indications for TENS (sensory component)

A

Treating pain syndromes
- Acute
- Chronic
- Post-Op
- Neurological (Ex: Shingles)
- Phantom

Before/during painful treatments
- Stretching
- Debridement

20
Q

Indications – Populations with Evidence of TENS efficacy

A

LBP
Neck pain
Myofascial pain
RA
OA
Dysmenorrhea
Labor/post labor
Post op pain: abdominal, thoracic, shoulder
Painful shoulder post CVA (stoke)
Peripheral neuropathy
Trigeminal neuralgia
Headache (migraine and other)
Post amputation and phantom limb
Acute pos-traumatic
And others…

21
Q

Precautions for TENS

A

Cardiac pacemaker
- Recommend ECG monitoring for 1st treatment

Implantable Cardioverter defibrillator
- Need to inactive during sessions
- ECG monitoring

Allergic skin reactions under electrode

Low cognitive function

Monitor Caffeine intake (3 cups/day or 200 mg/day; Can reduce effect)

Abnormal skin sensation

While driving

Keep out of reach of children

Be aware of medication usage (Ex: Opiods)

22
Q

Neural Depolarization

A

When considering activation of neural tissue with current, you must consider
- Relative size and myelination of neurons
– Larger are easier to stimulate
- Anatomical depth of tissue relative to depth of penetration of current
–Closer to the surface are easier to stimulate

23
Q

Typical Equipment - TENS/IFC

A

Intensity/Amplitude

Pulse rate/Frequency

Pulse duration

Common Wave characteristics:

  • Biphasic with a negative spike component
  • Monophasic with a positive rectangular component only (Charge imbalance, may get skin irritation)

Some modulation (change) option

24
Q

Typical Tens Devices

A

Battery Operated

Common ranges on parameters:

Pulse duration range

20-200 usec

Pulse rate (frequency) range

1-150 pps

Amplitude (intensity) for each channel range

1-80 mA

25
Q

TENS - Modes

A

3 types of application

Conventional-common

Low rate – not common

Noxious – rare at best

26
Q

Conventional or High Rate TENS

A

Short duration pulses of 20 to 80 microsec and with a current amplitude that causes strong but tolerable sensation
- AB fibers are larger and myelinated. This mode is selected for these
- **Trying to create a strong but tolerable tingly sensation **

Pulse frequencies of 80 to 150 pps are recommended.

Modulation selection based on what is available or patient preference

27
Q

Conventional TENS - Big Picture

A

Create a strong tingling sensation that reduced the perception of pain while the stimulus is present, primarily through spinal cord pain modulation (pain gate theory)

28
Q

Low Rate TENS

A

Create “pain” by stimulating delta A and C fibers to produce inhibitory effects with endogenous opiates

Generally less than 10 pps

Higher amplitude

Longer pulse duration (200-600usec)

Associated uncomfortable muscle contractions
- Twitch

Treatment Duration 20-40 min

29
Q

Low Rate TENS - Adv and Dis

A

Indicated for Chronic Pain Syndromes

Advantages
- Improved post treatment reduction of pain
- Low accommodation

Disadvantages
- Motor response – uncomfortable
- Not for acute conditions
- Less effective in patients on opiods

Half Life of endogenous opiates is 4-5 hours

Stimulation time limited due to potential muscle soreness

Onset of analgesia is generally delayed 20-30 minutes

Get a longer lasting effect from a shorter treatment – can get pain relief that doesn’t require constant use of the device

30
Q

Noxious level or brief intense TENS

A

Works in the same way Low Rate TENS but seems to be effective at eliciting endorphin release

May have longer lasting effects (6+ hours)

1-5 pps, longer pulse duration up to 1000 usec

30-45 seconds on, 2-3x per point

31
Q

IFC

A
  • Interferential current is an alternative to TENS
  • Same basic concepts as TENS
  • Different wave characteristics
32
Q

IFC Stimulation

A
  • Interferential current is the waveform produced by the interference of two sinusoidal alternating currents of slightly different frequencies
  • These are delivered through two different sets of electrodes via separate channels.
  • Electrodes are positioned so that the currents intersect.
  • When the two currents intersect they interfere.
  • This produces a higher amplitude if they are in the same phase and lower amplitude if they are in opposite phases
33
Q

IFC and Beats

A
  • When there is a difference in the two frequencies this produces an “envelope” of pulses referred to as beats.
  • Beat frequency is equal to the difference in frequencies of the two currents.
  • In this example the difference is 5100-5000=100 Hz therefore the beat frequency will be 100 Hz.
  • Carrier frequency by definition is the lower of the two frequencies, in this case 5000 Hz.
34
Q

IFC

A

Carrier frequency usually 1000 to 10,000 Hz
This overcomes skin impedance better due to high frequency
More adverse reactions have been reported

35
Q

Treatment Parameters for IFC

A

Based on the beat frequency (same range for TENS)

Spinal cord level pain inhibition (80-150 bps)

Endogenous opiate mechanisms (1-10 bps)

36
Q

TENS vs IFC: Which to choose?

A

Availability

Body area location (TENS can function with a single channel)

Tissue depth (IFC might stimulate deeper)

Patient preference

37
Q

TENS/IFC Skin Prep

A

Skin Prep Wipes for long term

38
Q

Electrode Placement

A

No consistent evidence for preferred sites:
- Place it near the pain site
- Along nerve path
- At the contralateral, homologous site
–Phantom limb pain
- Closer the electrode are the more superficial and concentrated to stimulus
– Should not be closer than 1 cm to each other

39
Q

Home Programs - Patient Education

A

Battery Changing

Reviewing hardware

Skin care

Removing electrode – peel skin away not electrode

Where/when to use/not use device

Prescribed schedule
- Conventional (during)
- Low rate (before)
- Pain dependent
- Time dependent
– Used for prescribed duration regardless of symptoms combined with activity

40
Q

Home Program Essentials

A

Verbal and written instructions

Supervised clinical trial

Home program of sufficient duration/intensity

Appropriate outcome measure (pain function, medication usage, others)

Follow up appt

41
Q

Increasing likelihood of success

A

Emphasize FUNCTION as the overall outcome, amongst many other complex outcomes beyond pain

Phys Agents (10 decks)

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