Electrical Stimulation Goals and Treatment

Electrical Stimulation Goals and Treatment

Adapted from Therapeutic Modalities: Art & Science, Knight

& Draper (2008) for KIN 195

Competencies for Therapeutic Modalities

TM-C2

Explain the principles of physics, including basic concepts associated with the electromagnetic and acoustic spectra (e.g., frequency, wavelength) associated with therapeutic modalities.

TM-C3

Explain the terminology, principles, basic concepts, and properties of electric currents as they relate to therapeutic modalities.

TM-C4Describe contemporary pain-control theories.

Competencies for Therapeutic Modalities, cont.

TM-C6

Explain the body's physiological responses during and following the application of therapeutic modalities.

TM-C7

Describe the electrophysics, physical properties, biophysics, patient preparation and modality set-up (parameters), indications, contraindications, and specific physiological effects associated with commonly used therapeutic modalities.

TM-C8Identify appropriate therapeutic modalities for the treatment

and rehabilitation of injuries and illness.

Basics of Electricity• Must understand why as well as how to

use electrical stimulation.Or• You’ll be a knobologist.

Review: Requirements for Ion Migration: Chemical Effects

• Must have continuous monophasic DC electron flow to cause ion migration.

• Moving electrons against gradient– Like pushing a car uphill– When you pause, it rolls back down.

• Why does a twin-pulse high-volt current not produce a chemical effect?

Review: Polarization & Action Potentials

• Stimulation requires a polarized membrane (between inside and outside of nerve membrane).

– More positive ions than negative ions outside nerve and more negative ions than positive ions inside membrane

– When polarized, membranes have a potential of −70 to −90 mV between inside and outside of membrane

Review: Polarization and Action Potentials (cont.)

• Nerve action potential eventually causes– An ascending sensory impulse to the brain

Or– A descending muscle action potential

• Muscle action potential causes muscle contraction.

Review: Polarization and Action Potentials (cont.)

• Nerve repolarizes quickly.

• Absolute refractory periods vary from 0.4 to 2 msec

– Depends on specific nerve

Review Excitability: Nerve Size and Depth

• The larger the nerve, the easier it can be stimulated.• The more superficial the nerve, the easier it can be

stimulated.• In a practical sense:

– Large sensory nerves are more excitable than motor nerves.– Motor nerves are more excitable than pain fibers.

Review Excitability: Rate or Frequency

• Doesn’t effect individual threshold– Effects torque as it approaches tetany– Increased rate means increased fatigue rate.

fatiguetetany

5/sec

Review Electrodes: Physical Dimensions

• Shape is unimportant– Most are round or square or rectangular.

• Size and placement determine the number of motor units stimulated.

Review Electrode Function

• Active electrode– Electrode under which the current density

is great enough to elicit the desired response

• Indifferent (dispersive) electrode– Electrode under which the current density

is not great enough to elicit the desired response

Most Commonly Used Wave Forms

DC: DC

IF: Polyphasic

HV: Twin pulse

LV : Biphasic and polyphasic burst (Russian)

TENS: Biphasic

Review: Pulse and Cycle Characteristics

• Pulse: finite period of charged particle movement, separated from other pulses by a finite time during which no current flows

• Made up of one or more phases

Review: Pulse and Cycle Characteristics (cont.)

• Pulse named by number of phases– Monophasic

• One phase

• Current flows in one direction only.

– Biphasic• Two phases

• Current flows in both directions.

– Polyphasic• Many phases

Review: Burst Characteristics • Burst

– Finite series of pulses flowing for a finite time period followed by no current flow • Think of it as turning a pulse train or AC current on and off.

– Burst interval• Time during which burst occurs

– Interburst interval• Time between bursts, usually in milliseconds

Review: Current Timing & Modulation

• Pulse width (pulse duration) – Time required for each pulse

to complete its cycle

– Reported in microseconds or milliseconds

• Short pulse duration: <150 µsec

• Long pulse duration: >200 µsec

• Interpulse interval – Time between successive

pulses

Review: Surge Characteristics

• Ramp up– Time during which the

intensity increases

• Plateau– Time during which pulses

remain at maximum preset intensity

• Ramp down– Time during which the

intensity decreases

Commonly Used Wave Forms (p.142)

• Direct (galvanic) wave form– Pure DC current,

used for iontophoresis

Commonly Used Wave Forms (p. 142, cont.)

– Monophasic, rectangular, pulsed

• Also called a modified square wave• Similar to DC but modulated from AC input

current• On and off times are not necessarily equal

Commonly Used Wave Forms (p. 142, cont.)

– Polyphasic, symmetrical, balanced, sinusoidal• Wave form generated and sold by utility

companies

Commonly Used Wave Forms (p. 142, cont.)

• Faradic wave form– Induced asymmetrical AC current– Biphasic, asymmetric, unbalanced, spiked – Positive portion: short duration, high amplitude, and spiked – Negative portion: long duration, low amplitude, and curved

Commonly Used Wave Forms (p. 142, cont.)

• Biphasic wave form– Symmetrical, balanced, rectangular, pulsed

Commonly Used Wave Forms (p. 142, cont.)

• Russian wave form– Polyphasic, symmetrical, sinusoidal, burst

– Developed by Russian scientist Kots; thus the name

– Initially a 2500 Hz AC current burst, modulated every 10 msec, now many frequency choices

Commonly Used Wave Forms (p. 142, cont.)

• Twin pulse wave form– Monophasic, pulsed, twin spiked– Common wave form of high-volt muscle simulators

– Has been called high-volt galvanic and pulsed direct current – However, not direct or galvanic current– Result of misunderstanding physiology

Commonly Used Wave Forms (p. 142, cont.)

• Interferential wave form– Symmetrical, sinusoidal, high frequency (2000–5000 Hz) AC

– Two channels, with different frequencies, used simultaneously

– Two currents cause a tissue current amplitude modulation

Commonly Used Wave Forms (p. 142, cont.)

• Interferential wave form: current amplitude modulationTwo identical currents

Two opposite currents

Two offset currents

Usually accomplished with two different frequency currents

Use of Electrical Current Stimulation for Pain Relief

• Transcutaneous electrical nerve stimulation (TENS)

• Interferential current therapy (IFC)• Iontophoresis• Neuromuscular electrical stimulation

(NMES)

For all modalities…• Know the effects, indications, contraindications,

& precautions• Verify the modality is set up correctly before

treatment begins• Prepare the patient psychologically & physically

for the treatment• Begin treatment conservatively and ask for

patient feedback• At the end of treatment, clean up the modality

and instruct the patient about next treatment and activity level until then

• Maintain the machines appropriately

TENS• TENS

– Transcutaneous: through the skin

– Electrical– Nerve: sensory– Stimulation:

depolarize• Stimulate sensory

nerves with pulsed current via surface electrodes

TENS: Physiological Aspects• Electrode placement

– Usually at the site of pain

• Clinician can change the patient’s perception of acute and chronic pain.

• Selective depolarization of afferent nerves

How does TENS work?

• Many theories

• Gate system and sensory TENS

– 80-150 pps

• Endogenous Opiate system stimulated

– Motor TENS and brief-intense TENS• Low beat frequency 1–5 pps• Slight muscle twitch

Brief Research Findings on TENS

• Research is difficult.• TENS has relieved pain associated with

– Osteoarthritis– Rheumatoid arthritis – Dysmenorrhea – Low back pain

• Postoperative TENS

TENS

Advantages1. Portable

a. Can be used during activity

2. Self-treatment

3. Alternative to cold during cryokinetics

Disadvantages1. Eliminates pain; not

cause of pain

2. May mask more serious problems

3. We don't know enough about it yet

4. May become a panacea (too reliant on it, maybe even after healthy)

TENS: Indications & Contraindications

Indications

1. Pain of peripheral origin

2. Acute pain

3. Chronic pain

Contraindications1. Do not use on person

with:a. An implanted pacemaker

b. History of heart disease

2. Do not treat trans-thoracic area

3. Discontinue use if a skin irritation develops

TENS: Precautions

G. Precautions1. Treatment over an area with:

a. Impaired sensation

b. Skin lesions (cuts, abrasions, new skin, recent scar tissue)

2. While driving or operating heavy machinery

3. Temporary decrease in pain does not mean cause of pain has gone.

4. Delicate unit, not a cheap radio a. Treat it kindly.

Electrode placement techniques for TENS

Electrode placementa. Over acupuncture or trigger points

b. Directly over the pain

c. Proximal or distal to pain

d. Crisscross over pain (two-channel unit)

e. Over motor point (helps with spasms)

f. Dermatome placement

Adjust pulse width and ratea. Go through entire range and select most

comfortable settings.b. Specific settings for specific conditions.

i. Acute pain: narrow pulse width (75 µsec) and high pulse rate (80–200 pps)a) Pain relief is almost immediate, but short lasting (1–60 min)

ii. Chronic pain: wide pulse width (200 µsec) and low pulse rate (1–5 pps)

a) Pain relief may take ½ hr but will be long lasting (6–7 hr)

Application Parameters: TENS

Length of application1. Extremely variable

2. Some treat for 30–60 min, others for hours

Frequency of application1. Three or four times a day as needed for pain

Duration of therapy

1. Use until TENS is no longer effective.

Application Parameters: TENS (cont.)

Interferential Current

• Interference or superimposition of two separate medium-frequency sinusoidal currents on one another

• Symmetrical, sinusoidal, medium frequency (2000–5000 Hz) AC

• Invented in 1950; used in United States by 1980s

• Fifth most frequently used physical agent

• Basic principle– Decrease tissue impedance (resistance) so

simulation is less painful• Impedance at 50Hz = ~3200 Ω • Impedance at 4000 Hz = ~40 Ω• Current passes more easily through skin

• Advantages of vector pattern– Surface and deep stimulation– Targeted tissues for added benefit– Treatment of easily localized pain– Treatment of large areas– Treatment of poorly defined pain

What Is IFC Therapy? (cont.)

How Does IFC work? (cont.)

• Example: One channel runs at 5000 Hz another at 5100 Hz– Use a dynamic vector (or scan for poorly

defined pain)

– Use target for easily localized pain

– Treats most of the area bracketed by the electrodes (scan or dynamic vector)

Is IFC Therapy Effective? (cont.)

• Those who have had success – Correctly position vector– Use appropriate size and positioning of

electrodes– Use appropriate stimulation parameters– Persevere, if pain relief is not immediately

obtained

IFC advantages & disadvantages

Advantages1. More comfortable than

a TENS a. Medium-frequency

currents meet with less skin resistance than low frequency currents.i. TENS uses low frequency

currents

2. Stimulates tissues deeper than a

TENS unit3. Larger coverage area

than TENS

Disadvantages1. Eliminates pain;

doesn't deal with cause of the pain2. May mask more

serious problems3. Few portable units

available4. Sometimes

becomes a panacea

IFC: Indications & Contraindications

Indications1. Acute pain

2. Chronic pain

3. Muscle spasm

4. Pain that covers a large area

Contraindications1. Do not use on a

person who has:a. Implanted pacemaker

b. History of heart disease

2. Do not treat transthoracic area

3. Discontinue if skin irritation develops

IFC Precautions

Precautions1. Be cautious when using IFC over:

a. Impaired sensation

b. Skin lesions (cuts, abrasions, new skin, recent scar tissue, etc.)

2. Use caution when using IFC while driving or operating heavy machinery.

3. A temporary decrease in pain does not mean the cause of the pain has gone.

Application Parameters: IFC Adjust pulse rate settings for specific injury

a. For acute paini. Use a high pulse rate of 80–200 ppsii. Pain relief is almost immediateiii. Lasts only a few minutes to 1 hr

b. For chronic pain i. Use a low pulse rate of 1–5 pps ii. Pain relief may take ½ hr iii. May last 6–7 hr

Target or vectora. Pain that is easily identifiable and pinpointed

i. Use target or vector buttons to move spot where current intersects to area directly over pain

b. Pain that is hard to pinpointi. Use dynamic vector

Application Parameters: IFC (cont.)

C. Length of application1. 20–30 min

D. Frequency of application1. Once or twice daily, as needed for pain

E. Duration of therapy

1. Use until IFC is no longer effective.

NeuroMuscular Electrical Stimulation

• NMES is used for– Muscle reeducation and prevention of

disuse atrophy – Decreasing muscle spasm– Decreasing edema

History of NMES • 1980 companies started manufacturing

Russian current

• No North American scientist has been able to duplicate Kots’s claims of 30% increase in force vs. voluntary contractions and lasting gains up to 40% in healthy athletes– Great amount of pain (as the current

amplitude was increased to try to replicate a voluntary muscle contraction)

Why NMES?

• Used on patients who cannot perform a voluntary muscle contraction– Peripheral nerve innervation is intact, yet muscle

is too weak to contract from atrophy, pain, immobilization, etc.

• Promotes early AROM in postsurgical and immobilized limbs

• Break pain-spasm-pain cycle of muscle spasms

Don’t Replace Strength Training with NMES

• NMES recruits fibers in the opposite order than that of a voluntary contraction.– Machine = large fibers followed by small– Voluntary = small fibers followed by large

• Patient needs to move on to more traditional weight training ASAP.

Tetanic Contraction to break Muscle Spasm

• Goals– Increase local circulation– Remove metabolic wastes– Mechanically stimulate muscle fibers– Induce some muscle spasm fatigue

NMES for Decreasing Edema

• Produce cyclic muscle contractions to help pump chronic edema– 5–10 sec on; 5–10 sec off

NMES Effects

Effects1. Muscle contraction

a. Increase blood flowb. Retard atrophy developmentc. Decrease and retard neuromuscular inhibitionsd. Increase muscle relaxation; decrease spasm

2. Decrease paina. Possibly by decreasing muscle spasm

NMES Advantages & Disadvantages

C. Advantages1. Can be applied to

immobilized body part

D. Disadvantages1. Sometimes

becomes a panacea

NMES Indications & Contraindications

Indications1. Residual or chronic muscle

spasm

2. Any time normal neuromuscular function is not possible

3. Muscle strains

4. During cast immobilization or disuse atrophy

5. Pain owing to muscle spasm

Contraindications1. Do not use:

a. On a person with a pacemaker

b. Over the heart or brain

c. Over recent or non-union fractures

d. Over potential malignancies

NMES Precautions

G. Precautions1. Be cautious over an area with:

a. Impaired sensation

b. Skin lesions (cuts, abrasions, new skin,

recent scar tissue)

c. Decreased range of motion

d. Extensive torn tissue

Application Parameters:NMES

C. Length of application1. 10–30 min

2. See individual manufacturer’s instructions.

D. Frequency of Application1. As often as twice per day if separated by

3–4 hr

Iontophoresis: Basic Principle Like charges repel like charges,

Drug ions are repelled or pushed into the underlying tissue. Two electrodes

– One drug delivery– One larger dispersive electrode

How Does Iontophoresis Work?

• When an electrical DC current is applied

– Positively charged electrode delivers positively charged drug ions into skin and surrounding tissues

– Negatively charged electrode delivers negatively charged drug ions into skin and surrounding tissues

Why Use Iontophoresis?

• Delivering medicine such as anti-inflammatories and pain relievers directly without the negative effects of

– Painful needle injections– Risk of infection from nonsterile needle

injections– Avoid the gastrointestinal side effects of

NSAIDs and COX-2 inhibitors– Localized drug delivery; doesn’t travel through

entire system– Machine is Portable and easy to transport

Common Drug Ions Used in Sports Medicine

• Dexamethasone– Negative ion

– Reduces inflammation by inhibiting biosynthesis of prostaglandins and various other inflammatory substances

• Acetate– Negative ion

– Assists in dissolving calcium deposits and scar tissue in soft tissues

Common Drug Ions Used in Sports Medicine (cont.)

• Hydrocortisone– Positive ion– Assists in decreasing tissue inflammation

by inhibiting biosynthesis of prostaglandins

• Lidocaine– Positive ion– Assists in decreasing local pain by

blocking nerve impulse transmission

Is Iontophoresis Effective?

• Debate– Research has shown it to deliver

medication from 6 to 20 mm below the skin

• Effective in reducing pain and inflammation associated with

• Plantar fasciitis • Temporomandibular disorders • Epicondylitis

– When dexamethasone, lidocaine, or sodium salicylate is used

Ionto Advantages & Disadvantages

AdvantagesCompared to injections:

Virtually painless

Noninvasive, minimizing…

Risk of infection

Risk of tissue necrosis, tendon rupture, etc.

Compared to oral medications:

Localized drug delivery, nonsystemic

Avoid risk of systemic side effects

Disadvantages1. Eliminates pain or

inflammationa. Doesn't deal with the

cause of the pain/inflammation.

2. Slight risk of electrode burns

3. Some believe transdermal drug delivery is not possible.

Iontophoresis Indications & Contraindications

Indications

Used to administer water-soluble ionic medications

Contraindications

Damaged or denuded skin Recent scar tissue

Drug allergies

Transcranial

Orbital region

Electrically sensitive support systems Pacemakers

Iontophoresis: Precautions

Precautions

Diabetes

Pregnancy

Over external metal fixation devices

Elderly skin

TMJ

Dizziness

Metallic taste

Ionto: Drug Dose Calculation

Dosage (mA/min) = Current (mA) × Treatment time (min)

•  Examples:• 40 mA/min = 4.0 mA (current) × 10 min (time)

• 40 mA/min = 2.0 mA (current) × 20 min (time)

• 24 mA/min = 2.0 mA (current) x 12 min (time)

Reported Sensation of Iontophoresis

Some patients feel little or no sensation; others describe it as a tingling or warm sensation.

The intensity of the sensation varies among patients and depends on the site being treated.

These sensations usually decrease or disappear after a few minutes.

Typical Skin Reactions to Ionto

DC causes capillary dilatation, leading to erythema (reddening) of the skin under one or both electrodes.

Less frequent: appearance of small fluid-filled bumps caused by the release of histamine from dermal mast cells

Note: These skin reactions disappear over the course of a few minutes but may last longer in patients with particularly sensitive skin. Also, some patients with sensitive skin may react to the adhesive on the electrode.

Reduce Negative Effects from Iontophoresis

• To help reduce the risk of skin irritation – Clean the skin with an alcohol scrub.– After treatment, apply a lotion containing

aloe vera.– Increase the size of the anode or cathode

to decrease current density.– Increase the spacing between electrodes

to decrease current intensity.

Application Parameters: Ionophoresis

C. Length of application1. Dose specific

D. Frequency of application1. Every other day

E. Duration of application1. Up to 3 weeks

High Voltage Pulsed Current Stimulation for Wound Healing

• Electrical stimulation for the purpose of repairing tissues includes management of open wounds and edema reduction.

• Production of a twin-peak, monophasic, pulsed current driven by its characteristically high electromotive force or voltage

• Positive or negative polarity

HVPC (cont.)

• Versatile and can perform several functions:

– Pain modulation– Edema reduction– Muscle reeducation and spasm reduction– Wound healing

Characteristics of High-Volt Stimulator• Low volt stimulators generate <150 V

• High volt stimulators generate >150 V

• HVPC uses between 150 and 500 V.

• High peak voltages

• Low average current

• Twin peak monophasic waveform – Resembles a double spike with a fast rise

followed by a fast decline

• Short pulse widths (100–200 µsec)

• Pulse rates of 1–200 Hz

HVPC: Uses & Techniques

• Monophasic current used for– Pain reduction– Disuse atrophy– Reduction of edema – Wound management

• Monopolar or bipolar technique– Monopolar used when treatment is directed

over a large area – Bipolar used for muscle contraction or

chronic pain

HVPC: Advantages

• Less resistance to the current by the skin

• Short phase duration allows for moderately high-intensity muscle contraction with little discomfort

– Other types of stimulators provide a stronger contraction

• Highly variable in its functions

• Can be used for – Pain modulation

a. Sensory level (acute pain)

b. Motor level (chronic pain)

– Edema reduction – Treating muscle

weakness– Wound healing

HPVC: Disadvantages

Disadvantages1. Cannot provide as strong of a contraction as

NMES

2. Many aren’t portable.

3. Sometimes trial and error are needed to determine electrode polarity for wound healing.

4. Effects (muscle contraction) are as strong as low-volt units.

HPVC: Indications & Contraindications

Indications1. Wound lesions

(pressure sores, scarring from incisions)

2. Edema control and reduction

3. Residual or chronic muscle spasm (when low-volt unit unavailable)

4. Pain

Contraindications1. Do not use on patient

with pacemaker

2. Do not use overa. Heart or brain

b. Lumbar and abdominal area of pregnant women

c. Potential malignancies

d. Anterior cervical area

HPVC Precautions

G. Precautions1. Be cautious when using HVPC over an

area with:a. Impaired sensation

b. Extensive torn tissue

c. Hemorrhagic area

2. Patients with epilepsy should be monitored during treatment.

HVPC: Edema Management

• Curbing edema formation– HVPC is not DC– Decreases the permeability of

microvessels – Decreases the leaking of vessels, reducing

the number of plasma proteins and amount of fluid that leave the vessels to enter the interstitial spaces

HVPC: Edema Management (cont.)

• Two protocols for curbing edema Water immersion

-Negative polarity -120 pps -90% of visible motor threshold-30 min treatments every 4 hr-Apply ASAP postinjury or as long as edema is still forming

Resolution of edema once formed-Can be employed in a muscle pumping action to get rid of edema-Intensity increased until strong muscle contraction -Setting of 1–10 pps for muscle contraction

HVPC: Pain Modulation

• Ineffective in reducing the pain of delayed-onset muscle soreness

• Yet has been shown to help relieve pain caused by muscle spasm

HVPC: Wound Management

• How does HVPC stimulate wound repair? – Body possesses bioelectric currents in the

vascular and interstitial tissues.

– Blood vessel walls, insulating tissue matrix, interstitial fluid, and intravascular plasma are capable of conducting bioelectricity.

– When tissues are damaged, an electrical potential is created between injured and noninjured tissues.

HVPC: Wound Management (cont.)• DC may stimulate cellular activity when injured.• Stimulating débridement of injured tissues• Tissue regeneration and remodeling• May speed up healing by promoting the natural

healing process• May develop a difference in potential between

wound area and the surrounding healthy tissue• Injury potential typically becomes positive 24–48

hr after injury & negative 8–9 days after injury.• As the wound heals, the difference slowly returns

to baseline.– Can be used to enhance the natural process of tissue

recovery and healing

HVPC: Electrode Polarity

• Negative polarity– Increases

• Vascularity• Stimulation of

fibroblastic growth• Collagen

production• Epidermal cell

migration– Inhibits bacterial

growth

• Positive polarity – Increases macrophages– Promotes epithelial

growth

HVPC: Electrode Polarity (cont.)

• Most treatments begin with the negative polarity– Encourages blood clots to dissolve and

increases the inflammatory by products• Necrotic tissues

• Positive polarity encourages clot formation around the wound and granulation tissue.

Application Parameters: HVPC

D. Frequency of application1. As often as three per day if separated by

3–4 hr

Microcurrent Electrical Nerve Stimulation

• Therapeutic use of constant (DC) and pulsed (interrupted) currents where the stimulus amplitude is in the microamperage range

• Proposed Uses– Tissue healing– Pain control– Edema control– Slow healing skin lesions

MENS Names• Many names of microcurrent

– MENS does not accurately describe this device. – Current intensity is too low (<1 mA) to cause motor nerve

depolarization

• Other than MENS, these devices have been referred to as:– Low-voltage pulsed microamp stimulation– Biostimulation– Bioelectric therapy– Low-intensity direct current – Low-intensity electrical stimulation

MENS: Theory

• Brief research– No clear-cut

research supporting the use of microcurrent therapy

– Positive effect in treating• Pressure ulcers• Diabetic ulcers• TMJ disorders

• No effect in treating– DOMS– Pressure ulcers– Coracoacromial

arch pain– Surgically induced

wounds

MENS: Theory (cont.)

• Might play a positive role in wound healing, an area athletic trainers typically don’t deal with

• It is safe.