Electrical Currents for Pain Control

TENS

transcutaneous electrical nerve stimulation

Electrical stimulation to modulate pain

How does High rate TENS modulate pain?

Through gate controls theory of pain which activates non-nociceptor A-beta nerves and inhibits the transmission of nociceptive signals at the spinal cord level

How does Low rate TENS modular pain?

Through endogenous opioid release, with repetitive stimulation of motor nerves

High Rate TENS

Short duration pulse (50-80 microseconds)

High frequency (100-150 pps)

Amplitude to produce comfortable sensation (sensory level) only without muscle contraction

What is the caveat with High rate TENS?

Patient will accommodate adaptation, utilize time on and time off ratios

High rate TENS is most effective when?

When stimulation is applied?

Low Rate TENS

Stimulates endogenous opioid production and release, effective for 4-5 hrs after stimulation ends

Long duration pulse (100-300 microseconds)

Low frequency (2-10 pps) amplitude for small muscle interactions

What is the caveat for Low rate TENS?

Use no more than 30 mins per session to avoid delayed onset muscle soreness

Burst Mode TENS

Stimulation delivered in bursts or packages, same rate as low-rate TENS, but may be more effective due to more current being delivered

TENS for Acute Pain

Found to help with post-operative pain, may reduce analgesic medication intake, and helps get pain under control to prevent chronic pain

TENS for Chronic Pain

More for non-surgical management of OA, RA, patellofemoral syndrome

Contraindications and Precautions of TENS

Just like all other E-Stim, but do NOT use e-stim at the motor level when muscle contraction may disrupt or delay healing, for example a muscle or tendon tear

Would you use a high or low rate TENS for muscle tears?

High Rate TENS due to stimulation only at the sensory level

Pulsed Biphasic Waveform (TENS Standard)

waveform that alternates between positive and negative phases (biphasic), with distinct pulses that turn on/off (pulsed), typically symmetrical or asymmetrical

Placement: Usually 2 electrodes over or around pain site

Interferential Current (IFC)

Uses 2 medium-frequency AC currents (1000-10,000 Hz) that intersect in the tissue to produce a "beat frequency"(e.g., 100 Hz), modulating pain.

Placement: 4 electrodes in a crisscross pattern

Carrier Frequency

Set by machine (The original frequency of each alternating current (AC) used in IFC therapy)

Beat Frequency

Set by therapist (resultant frequency produced by the interference of two carrier frequencies.)

Quadpolar Technique

4 electrodes cross when IFC is used surrounding area of pain

Application Example for Sensory Level IFC

4100 Hz – 4000 Hz = 100 Hz beat frequency

This is the actual frequency that stimulates sensory nerves or motor fibers.

When currents are phase, there's a increase in?

Current, but when they are not, the current is reduced

Advantages of Inferential E-Stim

Comfort, more total current and larger treatment area, but no strong evidence that it's better than TENS for Pain

Premodualted E-Stim

Delivered through only 2 electrodes — and the interference of the two medium-frequency currents occurs inside the machine, not inside the tissue.

Sweep Mode (IFC)

modulates the beat frequency over time within a preset range (e.g., 80–150 Hz), to reduce nerve accommodation.

Target Mode (IFC)

Used to focus the stimulation at a specific point within the quadripolar IFC field (4 electrodes), by shifting the vector field.

direct the interference pattern to a precise location of pain

If the patient has pain, swelling, and muscle spasms, what is a good option for them?

IFC

Where do you place the electrodes?

Around painful area, sensory nerve distribution, over acupuncture points

If the electrodes are father apart, what is the indication?

Less current density and deeper the penetration, for deeper muscles and less pain

If the electrodes are closer, what is the indication?

High current density and more for superficial pain

High Rate TENS parameters

Frequency: 80-150 pps

Pulse Duration: 50-80 microseconds

Amplitude: Sensory

Treatment time: Unlimited but make sure to avoid accommodation at sensory level

Low Rate TENS parameters

Frequency: <10 pps

Pulse Duration: 200-300 microseconds

Amplitude: Small muscle contraction

Treatment time: 20-30 min every 2 hrs to avoid DOMS

High Rate TENS Duration of Action and Precautions

Duration of Action: Only while applied

Safety: Sensory only

Typical Conditions: Acute injury and repetitive strain

Low Rate TENS Duration of Action and Precautions

Duration of Action: 4-5 hr after treatment

Safety: Risks associated w/ muscle contraction

Typical Conditions: Chronic conditions, avoid repetitive strain injury