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What is the isoelectric line?

the baseline above and below which the waveform travels (in a biphasic wave)

What is an asymmetrical, biphasic wave?

A wave that is not symmetrical above and below the isoelectric line

Why is frequency/pulse rate important in TENS setup?

because different frequency settings target different nerve groups and the setting will determine if the "Gate Theory" or "Endorphin Theory" of TENS will be in effect
Why is pulse duration/pulse width important in TENS setup?

in general, the higher the pulse width, the more aggressive the stimulation feels (and less comfortable)

eventually, if the pulse width is high enough, it will usually elicit a muscle contraction, which may not be the desired result

if the pulse width is too low, however, the patient may not perceive the stimulation

Simply put, amplitude in a TENS unit is

what you feel when you turn the unit up, it's what causes the buzzing sensation of the TENS to go higher or lower

Which TENS modes work on the Gate Control theory?

conventional
(and to a degree, brief intense)

high frequency/pulse rate electrical activity is believed to block the pain by stimulating A–beta (large, heavily myelinated) fibers

Which TENS modes work on the Endorphin theory?

low frequency
burst
(and to a degree, brief intense)

low frequency or short bursts of mild electrical activity is believed to cause the body to release its own pain erasers (beta endorphins)

TENS is used only for

pain control

Which fibers are believed to open pain gates?

A–delta (small, myelinated, acute) and
C (small, unmyelinated, chronic) fibers

Which fibers are believed to close pain gates?

A–beta (large, heavily myelinated)

How do the Gate Control and Endorphin theories affect pain with the application of TENS?

– Gate Control tends to only work for the duration of the application; that is, there is little carry–over effect (thus treatment time for conventional is up to 24 hours)

– Endorphin theory modes (low frequency and burst) tend to have a carry–over effect due to the half–lives of the endorphins released

Another name for low–frequency TENS?
acupuncture TENS
Brief intense mode of TENS may achieve rapid relief of intense acute pain, however:
some patients may find the stimulation to be too much and may not be able to tolerate it for the treatment time required to achieve the desired results
Through which pain control theory is brief intense TENS thought to work?
through both
– Gate Control and
– Endorphin theories

because the
pulse duration/pulse width is high – Endorphin, and
frequency/pulse rate is high – Gate Control
What tends to happen to patients that are mobile during TENS application?
they tend to lose the electrodes
What is the minimum number of electrodes needed for TENS application?

2

Contraindications for ES
– cancer
– phlebitis, thrombus, thrombophlebitis
– pacemaker, other internal electrical device
– arrhythmia
– over carotid sinus
– transcerebral
– transthoracic
– over fresh fracture
– hemorrhage
How far apart should TENS electrodes be placed?
– at least one inch
– ideally, the width of the electrode
When a twitch is produced by a TENS treatment, where does it appear?
may be
– under the electrodes
– between the electrodes
How does pulse duration/pulse width of TENS relate to comfort?
imagine it like a needle

narrower needle goes into arm more comfortably
wider needle hurts more

Electricity is the force created by an imbalance in the number of negatively charged *** between two points known as ***

electrons, poles

Electric current takes the path of *** *** from the negative poles (cathode) an area of high electron concentration to the *** or positive pole and area of low electron concentration

least resistance, anode

What charged particles flow in human tissue?

ions

What is a charge?

an excess or deficiency of electrons

What is the charge of an atom?

neutral

What is an ion?

a particle with a charge (either positive or negative)

What is voltage?

the potential difference between two points in an electrical field,
the force that causes charged particles to move


V= I / R, volts = amps / ohms

What are Ohms (symbol R)

unit of electrical resistance


Ohm's Law says that current is directly proportional to voltage and inversely proportional to resistance


I = V / R amps = volts / ohms

Amperage (symbol I)

amperes (amps)


the rate at which electrical current flows. 1 amp = 1 coulomb/sec


I=V / R, amps = volts / ohms

Capacitance

the ability to store energy by means of an electrostatic field that provides frequency dependent resistance to electric current flow

One coulomb =

the basic unit of charge



1 ampere / sec

What is power (symbol P)?

voltage * current

P = V * I

measured in watts (W)

What is resistance?

opposition to movement by charged particles

How is resistance measured?

ohms

Inductance

the ability to store electrical energy by means of an electromagnetic field


measured by the henry

In AC inductance and capacitance resist current flow and are collectively known as ***

Impedance, uses symbol Z

What is Ohm's Law?

flow of current is directly proportional to EMF (current) and inversely proportional to resistance of circuit

V = I * R

What is conductance?

ease with which current is allowed to pass


symbol is mho

What is a conductor?

a material through which electricity flows easily

(e.g., nerve, muscle, blood)

What is an insulator?

a material through which electricity does not flow easily

(e.g., rubber, fat, bone, skin)

What is the best conductor in the body? Followed by....?

best conductor in body is nerves

then muscle, then anything with water (e.g., blood)

What is AC?

alternating current

bidirectional flow of charged particles

What is DC?

direct current

unidirectional flow of charged particles

Describe a DC and an AC waveform.

DC – unidirectional flow
AC – bidirectional flow

What is the conventional theory of current flow?

current flows from cathode to anode

(surplus to shortage)

What is the electron theory of current flow?

current flows from negative to positive pole

(negative to positive)

What types of modes are available for E–stim?

– continuous
– pulsed (monophasic / biphasic)
– burst
– interrupted

What is burst mode?

a finite series of pulses delivered in a package or envelope as a single pulse at a defined frequency

What is interrupted mode?

current flows for at least one second and ceases to flow for at least one second, usually with a hand–held electrode where one manually opens and closes the circuit

For what is interrupted mode used?

– trigger points
– acupuncture points

What shapes may a waveform take?

may take any of the following shapes and with each may also be symmetrical or asymmetrical
– rectangular
– square
– spiked / twin spiked
– sine

What pulse types may the waveform take?

– monophasic (pulse deviates in one direction––DC)
– biphasic (pulse is bidirectional––AC)
– polyphasic (pulse has more than 2 phases––Russian, Interferential)

//fce-study.netdna-ssl.com/images/upload-flashcards/back/8/5/51758402_m.jpg

How does the TENS unit convert the DC charge from the 9V battery to AC (biphasic)?

via a transducer in the unit

What are the characteristics of a balanced biphasic wave?

– it has the same amount of charge both above and below the isoelectric line

– the positive and negative phases do not have to have the same shape/waveform, just the same amplitude
(e.g., may be +5 mA rectangular pulse above the isoelectric line and a –5 mA spiked pulse below the isoelectric line)

Can a biphasic wave be balanced without being symmetrical?

Yes

the waveforms above and below the line may differ from each other (asymmetrical) but as long as the amplitude is equal they are balanced

How is DC frequency measured?

in pulses per second (pps)

How is AC frequency measured?

in cycles per second (cps)

a.k.a. Hz

Pulse width is also known as:

pulse duration

Waveform of a TENS unit?

biphasic, asymmetrical

What are the three main parameters to remember with E–stim?

Phase / pulse duration (width) – beginning to end of phase or pulse


Amplitude


Frequency


What is the intrapulse (a.k.a. interphase) interval?

the time between two successive components of a pulse when no electrical activity occurs

What is the interpulse interval?

the time between the end of one pulse and the start of the next pulse

What is rise time?

the time from baseline (0) to peak amplitude

What is decay time?

the time from peak amplitude back to baseline (0)

What is ramp time?

the time it takes to reach peak amplitude of a pulse train

What is total current?

current delivered to tissue/sec

= phase charge * number of phases/sec

How can one increase the total current delivered?

increase the
– intensity (amplitude),
– frequency (rate) and/or
– pulse duration (pulse width)

What is considered
– low volt?
– high volt?

– less than 100 volts

– 300 – 500 volts

What is considered
– low frequency?
– medium frequency?
– high frequency?

– up to 1,000 pps/cps/Hz
– 1,000 – 10,000 pps/cps/Hz
– > 10,000 pps/cps/Hz

How high does the frequency go in a TENS unit?

up to roughly 120 pps, which is considered "high" even though that rate places it in the "low frequency" category

What types of electrodes are used with E–stim?

metal plate (need wet sponges)
carbon rubber
self–adhering, reusable
– hand–held (wand; use gauze)
– invasive (implanted)

What are the considerations for electrode use?

– size should fit treatment area

– current density is inversely proportionate to electrode size (smaller electrode concentrates the energy)

– distance between electrodes affects penetration depth of energy (the further apart the electrodes are, the deeper the energy penetrates)

Pulse Period

pulse duration + interpulse interval + intrapulse interval

How can electrodes be placed to get deeper tissue penetration?
place them farther apart

Why does a smaller electrode deliver a higher current density?

How can the therapist use this to their advantage?

a smaller electrode is still conducting the same amount of current, therefore it will be concentrated in a smaller space

the therapist can place the smaller electrode on the target area to deliver more concentrated energy to that point

How does polarity affect treatment?

(DC only, as AC alternates being anode and cathode)

anode – positive pole
– repels positive ions
– sclerotic (toughening and desensitizing)
– analgesic effects

cathode – negative pole
– repels negative ions
– sclerolytic (softening)
– stimulating effect

What three types of electrode configurations can be used?

monopolar – 1 active electrode (smaller) on the target, and 1 dispersive electrode

bipolar – 2 equal–sized electrodes (spaced for needed depth)

quadrapolar – four same–size electrodes

What are the basic uses of ES?

pain modulation (gate control/endogenous opiates)
muscle relaxation (spasm reduction)
muscle re–education (innervated muscle)
– stimulation of denervated muscle
– edema reduction
– wound healing
– peripheral circulation
– iontophoresis

How are endogenous opiates (Endorphin theory) produced by ES?

– low rate (1–5 pps)

– muscle contraction (high pulse duration/pulse width)

Breakdown of E–stim:
– AC variants
– DC variants

NM – neuromuscular
F – functional
M – muscular

//fce-study.netdna-ssl.com/images/upload-flashcards/back/9/5/51759461_m.jpg

Precautions for ES

– cardiac disease
– CVA
– over pregnant uterus (ex. possibly 3rd trimester/labor)
– decreased sensation/mentation
– obesity
– extreme osteoporosis
– skin irritation, open wound
– superficial metal

When considering in ES:
– pulse duration/pulse width
– amplitude
– frequency/rate
what is more comfortable to the patient?
generally speaking
– shorter pulse duration/width is more comfortable
– amplitude varies by patient tolerance
– higher frequency/rate is more comfortable

What is interference?

the superposition of 2 or more waves, resulting in a new wave pattern

What is IFC?

– use of 2 sinusoidal current sources of medium frequency (1,000–10,000 Hz), created by two separate generators

– the two currents are intersected at 90 degrees

– the results create an interference wave

What is constructive interference?

– two superimposed waves of the same frequency (exactly aligned)

– the effects add together in the interference wave

– final wave has twice the amplitude

What is destructive interference?

– two superimposed waves of different frequencies (out of sync)

– the effects detract from each other in the interference wave

Full field or amplitude summation IFC characteristics

– frequencies of both currents are equal
– interference is "constructive" or "summative"
– results in vector of twice the original amplitude
– stimulates both at the surface and within tissue
– as in above picture, third wave may be static or dynamic (scan on)
– with scan on the amplitude is modulated so patient feels it in different places (sweep is frequency modulation)

Frequency difference IFC characteristics

– the frequency of the two currents differs
– results in a clover–leaf vector (or beat frequency)
– produces polyphasic pulses
– interference is destructive
– primarily stimulation within tissue (deep)

//fce-study.netdna-ssl.com/images/upload-flashcards/back/9/1/51819145_m.jpg

Contrast frequency difference IFC with scan off and scan on

With scan off and scan on

//fce-study.netdna-ssl.com/images/upload-flashcards/back/9/1/51819196_m.jpg

What is the carrier frequency? Which is it in the picture?

it is the base frequency of the unit before modification (the slower/lower of the two currents when they differ)

In the picture, the blue waveform is the carrier frequency

Advantages of IFC

– medium frequency decreases skin impedance more effectively
– greater intensity can be used to drive current into underlying tissue, since less used to overcome skin impedance
– more comfortable

– in general, the higher the frequency, the more comfortable the sensation

What are the indications for IFC?

– pain
– inflammation
– muscle spasm
– edema

What are the contraindications for IFC?

same as for other ES:
– cancer
– phlebitis, thrombus, thrombophlebitis
– pacemaker, other internal electrical device
– arrhythmia
– over carotid sinus
– transcerebral
– transthoracic
– over fresh fracture
– hemorrhage

How many electrodes are required for true IFC?

four

Which tissue is more excitable, nerve or muscle?

nerve

Which tissue has higher capacitance, nerve or muscle?

muscle

What is an action potential?

– sequence of depolarization and repolarization of nerve (or muscle) in response to stimuli

– "the basic unit of nerve communciation" (Cameron)

– also occurs along muscle (Michlovitz)

//fce-study.netdna-ssl.com/images/upload-flashcards/back/3/2/51823008_m.jpg

What happens when nerve or muscle cell depolarizes?

– the cell at rest has a negative charge and there is a high concentration of sodium outside its membrane

– depolarization opens sodium channel, sodium rushes in and changes polarization of (depolarizes) the cell

//fce-study.netdna-ssl.com/images/upload-flashcards/back/3/2/51823098_m.jpg

What is habituation

the CNS process of filtering out a continuous non-meaningful stimulus

What is accommodation

when the nerve's rate of depolarization decreases while the electric current remains unchanged

Indication for Iontophoresis

Acute or Chronic Inflammation


Arthritis


Myositis ossificans


as a means to deliver local anesthetic

Iontophoresis Medication Dosage

- measured in terms of milliamperes/minute


- based on the relationship between amperage of the current and treatment duration



current amperage (mA)x treatment duration (min)= Ma*MIN

Iontophoresis Meds and indications

- Dexamethosone and Lidocaine: Inflammation & pain control


- Lidocaine & epinephrine: pain control


- acetic acid: heterotopic ossification

Microcurrent Electrical Stimulation

- uses monophasic, biphasic, DC or AC


- intensity below depolarization threshold of sensory nerves


- current produced is


about 1/1000 amps of TENS

Contrast natural physiologcial contraction (NPC) of muscle with an ES contraction (ESC) of muscle. ***

NPC
– AP occurs only in one direction
– small–diameter, slow–twitch fibers activated first; then large diameter, fast twitch fibers recruited
– small–diameter, slow–twitch fibers are more fatigue resistant
– less fatiguing to patient
– contractions are smoother

ESC
– AP may propagate in both directions
– large–diameter, fast–twitch fibers activated first; then small–diameter, slow–twitch fibers are recruited later
– large–diameter fibers fatigue more quickly
– more fatiguing to patient
– contractions are jerkier

ES can be used to facilitate action potential in:

– sensory nerves
– motor nerves
– denervated muscles

but require different amplitudes and durations

What is the relationship between strength and duration of ES application?

– they are inversely proportional

– the stronger the current, the shorter duration needed

//fce-study.netdna-ssl.com/images/upload-flashcards/back/4/2/51824173_m.jpg

What is rheobase?

– the intensity of amplitude, with long duration stimulus, required to produce an action potential

– essentially, "amplitude"

//fce-study.netdna-ssl.com/images/upload-flashcards/back/4/2/51824281_m.jpg

What is chronaxie?

– the duration of ES application required to stimulate tissue at 2X rheobase (amplitude)

– essentially, "duration"

//fce-study.netdna-ssl.com/images/upload-flashcards/back/4/2/51824282_m.jpg

Indications for NMES?

– decreased strength and endurance
– decreased ROM
– post injury or surgery
– muscle spasms
– edema reduction
– orthotic substitution and FES
– rehab post nerve injury (dennervated muscle) (EMS)

How is NMES used to treat decreased strength and endurance?

in conjunction with active exercise

How is NMES used to treat decreased ROM?

– to stimulate muscle groups that can increase ROM

(e.g., with elbow flexion contracture, stimulate the triceps; or, alternately, stimulate the agonist, then the antagonist)

How is NMES used post injury or surgery?

– assist in initiating movement in a muscle or muscle group

How is NMES used to treat muscle spasms?

– the involuntary contractions may fatigue the muscle and allow it to rest
– break the pain–spasm–pain cycle

How is NMES used for edema reduction?

– contractions can help pump fluid from the area
– if DC is used, place the negative electrode at the area to repel negatively charged proteins

How is NMES used for orthotic substitution and FES?

– ambulation assistance––(e.g., attachment with heel switch to counter foot drop)
– shoulder rehab post shoulder subluxation

Rehab post nerve injury (dennervated muscle) is more specifically referred to as:

EMS

What factors need to be considered when using NMES for rehabilitation?

– how to apply
– placement of electrodes
– parameters to use
– diagnosis and goals
– patient age, tolerance, muscle size
– equipment available

What three variations of electrode setup can be used with NMES?

– monopolar
– bipolar
– quadrapolar

What should be considered in electrode placement with NMES?

– try to put one electrode on a motor point
– place electrodes parallel to direction of muscle fibers

What is a motor point?

– where the nerve enters the muscle
– where electrical stimulus produces greatest contraction with least amount of stimulus
(see pp. 25–35)

High TENS


Transcutaneous Electrical Nerve Stimulation

Intensity: Sensory


Pulse Frequency: 60 - 100 pps


Pulse Duration: 60 - 100 µsec


Mode: Modulated rate


Treatment duration: as needed


onset of relief: <10 min


Duration of relief: minutes to hours

Low TENS


Transcutaneous Electrical Nerve Stimulation

Intensity: Motor


Pulse Frequency: 2 - 4 pps


Pulse Duration: 150 - 250 µsec


Mode: Modulated burst


Treatment duration: 30 min


onset of relief: 20 - 40 min


Duration of relief: hours

TENS Electrode Placement


Direct Placement

Electrodes are placed directly on the painful site. The electrical channels run parallel to each other

Parameters for Russian

– middle frequency


2500 Hz carrier w/ burst
– AC

Frequency for NMES
– twitch
– vermicular
– tetanic contraction ***

– 5 pps
– between 5 and 35 pps
– over 35 pps

Pulse duration/width for NMES

– generally high (200–400 microsec)

– need to consider comfort

Voluntary Muscle Contraction

- small diameter type I fibers (slow twitch) muscle fibers are recruited first


- contractions and recruitment are asynchronous to decrease muscle fatigue


- Golgi tendon organs protect muscles from too much force production


- slow onset of fatigue

Electrically Induced Contractions

- large-diameter, fast twitch muscle fibers are recruited first (reversal of voluntary)


- contractions and recruitment are synchronous, based on the number of pps


- Golgi tendon organs can not override the developing tension within the musculotendinous unit


- faster onset of fatigue

Things to consider for contraction of denervated muscle

– muscle cannot contract physiologically
– does not respond to AC
– may respond to DC with a long–duration pulse (usually with a manual switch)
– presently, is not the recommended treatment, although it was in the past

What happens to an injured nerve during the first 14 days or so?

reaction of degeneration
– anterograde/Wallerian degeneration – distal to injury site
– retrograde degeneration – proximal to injury site

How fast can nerve tissue regenerate?

IF the nerve regenerates, it heals
– approx. 1 mm/day, or
– 1 inch/month

What should the therapist remember to do before changing ES treatment parameters?

TURN THE INTENSITY DOWN!

In what forms may AC be delivered? DC?

both AC and DC may be delivered either continuously or pulsed

At what pulse duration/pulse width is DC considered to be continuous?

if the pulse is >= 1 second

< 1 second is pulsed

Which is more comfortable to the patient, AC or DC?

DC is less comfortable than AC

it stings a bit

By what mechanisms has in vivo/vitro research suggested ES (specifically DC) can assist wound healing?

– alters cell membrane function
– increases protein synthesis
– has antibacterial effects
– promotes blood flow
– improves tissue oxygenation
– induces galvanotaxis

What is galvanotaxis?

occurs when charged cells are attracted to an electric field

(e.g., negatively charged ions are attracted to a positive electrode)

Describe the electrical potential difference within the skin.

the epidermis is negatively charged relative to the dermis

–––––– Epidermis
+++ Dermis

What happens to the electrical potential difference across the skin when there is a soft tissue injury?

the wound and adjacent epidermis become positive relative to the uninjured tissue

this electrical potential difference steadily declines over time, returning to normal only after the wound closes

ES may accelerate tissue healing by replicating or enhancing this process
Current of injury
– the transcutaneous potential of intact skin can be measured at 40–80 mV, but as soon as a full–thickness incision is made, this disappears so that a voltage gradient forms between the wound and surrounding intact skin (Jaffe & Vanabe, 1984)

– a microcurrent will then flow from the area of higher potential (the intact skin) into the wound so that a current of injury is generated

– the voltage peaks immediately after injury and gradually decreases as the wound heals (McGinnis & Vanable, 1986), leading to the concept that current flows may be defective in chronic wounds, and that applying electrical currents to wounds may stimulate healing (Kloth, 1995)

How can ES (specifically DC) help with wound healing?

– if barrier is broken, a flow of positive polarity occurs within the wound

– placing a negative charge (cathode) in the wound also attracts positive ions and is thought to trigger wound healing.

– exogenous ES may mimic body’s own bioelectric currents, facilitating or reinitiating (in a chronic wound) the wound healing process

At what stage of healing should negative polarity be used?

negative polarity (cathode) should be used in the acute stage of healing (3–7 days)

(Kloth)

When should the therapist switch to treatment with positive polarity in wound healing?

change to positive polarity (anode) in proliferative phase to facilitate epithelial cell migration

When would the therapist continue with treatment with negative polarity after the acute stage? ***

continue with negative polarity (cathode) if infection and/or inflammation present

What treatment should be used if tissue necrosis without inflammation is noted?

use positive polarity (anode)

What do some other wound treatment protocols suggest?

alternating polarities every few days

Protocol for DC wound ES

– place one electrode in wound
(saline–soaked gauze, aluminum foil, attached to alligator clip)

– another option is to place the electrodes around (outside) the wound with the target electrode proximal

– place the larger, dispersive electrode at convenient site
(Prentice suggests anode should be placed proximally, while Michlovitz, Behrens suggest placement away from the wound where skin is intact)

– some argument as to whether better to place proximal or distal
(go with proximal)

Cathode

Anode

– negative, usually black

– positive, usually red

What physiological effects tend to occur under the cathode?

– sodium combines with water to form sodium hydroxide
– alkaline reaction
– can cause softening (sclerolysis) of tissues

– stimulating effect on nerves, muscles
– bacteriostatic or bacteriocidal effects
– attracts fibroblasts (evolve into collagen), mast cells, platelets

What physiological effects tend to occur under the anode?

– chloride combines with water to form hydrochloric acid
– acidic reaction
– can cause hardening (sclerosis) of tissues, especially skin.

– analgesic effect
– attract macrophages

What is the other use of DC ES?

– can be used to treat edema

– place cathode at site of swelling to repel negatively charged proteins

What is iontophoresis?

introduction of ionic substances into the body for therapeutic purposes by use of DC

Why is iontophoresis used?

most common uses:
– reduction of inflammation (most often)
– pain relief
– alternative to injection
– less chance of systemic side effect

What forms of medication are used in iontophoresis?

– aqueous solutions
– ointments
– creams

What are the two most common medications used in iontophoresis, and what are their polarities?

– Decadron (dexamethasone) – negative (–)
– Lidocaine – positive (+)

How deeply do medications delivered by iontophoresis typically penetrate? ***

3–20 mm

What are some other uses for iontophoresis?

– calcium deposits– acetic acid (–)
– scar tissue– sodium chloride (–)
– athlete’s foot– copper sulphate (+)
– plantar warts– salicylate (–)


(Need to know other indications; but do not need to know the polarity needed in treatment for these.)

Parameters for iontophoresis delivery

– current type is most commonly continuous DC
– dosage is written as mA.min (mA minutes, NOT mA per minute!!)

– current (mAmp)
– time (minutes)

What are the typical dosages for
– phoresor unit?
– patches?

Recommended dosage with a
– phoresor unit is 40 mA.min
– patches may be higher: 80 mA.min

How is the 40 mA–min dosage administered with the phoresor unit?

time X mA
– if amplitude is set at 4 mA, it would take 10 min. to complete tx.
– if amplitude is set at 2 mA, it would take 20 min. to complete tx.

(It all depends upon what level of mA the patient can tolerate.)

Electrode configuration for iontophoresis

– active electrode over pathology
– indifferent is proximal or distal, but nearby

– medication goes under active electrode

– meds with a negative charge go under cathode.
– meds with a positive charge go under anode

(Thus opposites repel and medication is driven into skin.)

Which electrode in DC/iontophoresis tends to be a bit more irritating?

the negative electrode (cathode)

What can be done to reduce skin irritation with DC/iontophoresis?

if skin irritation occurs, increase size of negative electrode, regardless of which is active

(because of alkaline reaction)

What are the contraindications and precautions for iontophoresis?

besides
– allergy to medication
– use with other modalities
the same as other ES
CONTRAINDICATIONS
– cancer
– phlebitis, thrombus, thrombophlebitis
– pacemaker, other internal electrical device
– arrhythmia
– over carotid sinus
– transcerebral
– transthoracic
– over fresh fracture
– hemorrhage

PRECAUTIONS
– cardiac disease
– CVA
– over pregnant uterus (ex. possibly 3rd trimester/labor)
– decreased sensation/mentation
– obesity
– extreme osteoporosis
– skin irritation, open wound
– superficial metal

An electrical current is:

a flow of charged particles (electrons or ions)

The effects of electrical currents include:

– nerve depolarization
– muscle depolarization
– ionic effects

Most uses of electrical stimulation are based on its ability to depolarize nerves to produce:
action potentials
An electrically stimulated action potential can affect both:

– sensory nerves, producing a pleasant or painful sensation, or

– motor nerves, producing a muscle contraction

Sensations produced by electrically stimulated action potentials in sensory nerves can:
control pain
The muscle contractions produced by electrically stimulated action potentials in motor nerves can:
– strengthen muscles,
– increase muscle endurance,
– improve function,
– assist with joint positioning,
– decrease spasticity,
– increase circulation,
– control pain
– reduce edema due to poor circulation or lack of use
The ionic effects of electrical currents can be used to:
– facilitate tissue healing
– control the formation of inflammation–related edema
– promote transdermal drug penetration
What parameters must be considered for application of electrical stimulation?
– electrode placement
– waveform
– polarity
– current amplitude
– pulse duration
– pulse frequency
– on:off times
– ramp time
– treatment time
Another term for low–rate TENS
acupuncture–like TENS

Acupuncture–like or low–rate TENS is used for what type of pain?

acute or chronic, but mainly chronic
PD/PW = 200 – 300 microsec. (HIGH)
A = local motor contraction
F/R = 2–10 cps (LOW)
Time = approx. 30 min.

wide PD/PW is less comfortable

so this is continuous, unlike burst mode, which uses the same PD/PW and A, but F/R of 1–10 bps

The anode is the:

positive electrode

Burst mode TENS is used for what type of pain?

acute or chronic, but mainly chronic

PD/PW = 200 – 300 microsec. (HIGH)
A = local motor contraction
F/R = 1–10 bps (LOW)
Time = approx. 30 min.

wide PD/PW is less comfortable

so this is burst, unlike low–rate or acupuncture–like mode, which uses the same PD/PW and A, but F/R of 2–10 cps (thus continuous)

What is another name for conventional TENS?

high–rate TENS

Conventional or high–rate TENS is used for what type of pain?

acute and chronic, but primarily acute

PD/PW = 50 – 80 microsec (LOW)
A = sub–motor, tingling
F/R = 100 – 150 cps (HIGH)
Time = as needed up to 24 hrs.

narrower PD/PW is more comfortable for acute pain
The cathode is:
the negative electrode
Charge is:

one of the basic properties of matter (which is either neutral, negative, or positive)

it is noted as Q and measured in Coulombs (C)

Charge is equal to:

current X time

Q = I * t

What is current density? How can it be altered?

the amount of current delivered per unit area
a larger electrode reduces current density, a smaller electrode increases it

What is electrical current?

the movement or flow of charged particles though a conductor in response to an applied electrical field

noted as I and measured in amperes (A)

What is electrical muscle stimulation (EMS)?

application of an electrical current directly to muscle to produce a muscle contraction

What is functional electrical stimulation (FES)?

application of an electrical current to produce muscle contractions that are applied during a functional activity

(e.g., electrical stimulation of dorsiflexion in a patient with foot drop during the swing phase of gait)

What is galvanotaxis?

the attraction of cells to an electrical charge

specific cells, including neutrophils, macrophages, lymphocytes, and fibroblasts can be attracted to an injured healing area by an electrical charge because the cells themselves carry a charge

What is the gate control theory?

a theory of pain control and modulation that states pain is modulated at the spinal cord level by inhibitory effects of nonnoxious afferent input

What is impedance?
the total frequency–dependent opposition to current flow

noted by Z and measured in Ohms

for biological systems, impedance describes the ratio of voltage to current more accurately than resistance because it includes the effects of capacitance and resistance
What is iontophoresis?
the transcutaneous delivery of ions into the body for therapeutic purpose using an electrical current
What is a motor point?
the place in a muscle where electrical stimulation will produce the greatest contraction with the least amount of electricity

generally located over the middle of the muscle belly
What is neuromuscular electrical stimulation (NMES)?
application of an electrical current to motor nerves to produce contractions of the muscles they innervate
What is Ohm's law?

a mathematical expression of how voltage, current, and resistance relate where voltage equals current multiplied by resistance

V = I * R

What is the overload principle?

a principle of strengthening muscle that states the greater the load placed on a muscle and the higher force contraction it produces, the more strength that muscle will gain

What is phase?

in pulsed current, the period from when current starts to flow in one direction to when it stops flowing or starts to flow in the other direction

a biphasic pulsed current is made up of two phases;
– the first phase begins when current starts to flow in one direction and ends when the current starts to flow in the other direction, which is also the beginning of the second phase
– the second phase ends when current stops flowing.

What is polarity?

the charge of an electrode that will be
– positive (the anode) or
– negative (the cathode)

with a direct or monophasic pulsed current and constantly changing with an alternating or biphasic pulsed current

What is pulse?

in pulsed current, the period when current is flowing in any direction

What is resistance?

a material's opposition to the flow of electrical current

noted as R and measured in Ohms

What is TENS?

transcutaneous electrical nerve stimulation

application of electrical current through the skin to modulate pain

What is voltage?

the force or pressure of electricity

the difference in electrical energy between two points that produces the electrical force capable of moving charged particles through a conductor between those two points

voltage is noted as V and is measured in volts (V); also called potential difference

Voltage is also known as:
potential difference
What is alternating current?
a continuous bidirectional flow of charged particles

AC has equal ion flow in each direction, and thus no pulse charge remains in the tissues

most commonly, AC is delivered as a sine wave

with AC, when the frequency increases, the cycle duration decreases and when the frequency decreases, the cycle duration increases
What is medium frequency AC?
an AC with a frequency between 1,000 and 10,000 Hz (1–10 kHz)

most medium frequency currents available on clinical units have a frequency of 2500 to 5000 Hz

medium frequency AC is rarely used alone therapeutically but two medium frequency ACs of different frequency may be applied together to produce an interferential current
What is continuous current?

a continuous flow of charged particles without interruptions or breaks, a continuous current that goes in one direction only is known as a direct current (DC)
a continuous current that goes back and forth in two directions is known as an alternating current (AC)

What is a direct current (DC)?

a continuous unidirectional flow of charged particles
it is used for
– iontophoresis
– stimulating contraction of denervated muscle
– occasionally to facilitate wound healing

What is interferential current?

interferential current is the waveform produced by the interference of two medium frequency (1,000 to 10,000 Hz) sinusoidal ACs of slightly different frequencies

these two waveforms are delivered through two sets of electrodes through separate channels in the same stimulator

the electrodes are configured on the skin so that the two ACs intersect

when the currents intersect, they interfere, producing a higher amplitude when both currents are in the same phase and a lower amplitude when the two currents are in opposite phases

this produces envelopes of pulses known as beats

the beat frequency is equal to the difference between the frequencies of the two original ACs

the frequency of the original AC is called the carrier frequency

(for example, when a carrier frequency of 5000 Hz interferes with a current with a frequency of 5100 Hz, a beat frequency of 100 Hz will be produced in the tissue)

typically, electrical stimulation units that produce interferential stimulation allow the clinician to set the beat frequency and some also allow the clinician to select the carrier frequency

Why is interferential current thought to be more comfortable?

it is proposed that interferential current is more comfortable than other waveforms because it allows a low–amplitude current to be delivered through the skin, where most discomfort is produced, while delivering a higher current amplitude to deeper tissues

interferential current also delivers more total current than pulsed waveforms and may stimulate a larger area than other waveforms

however, although a number of studies have found that interferential current can decrease pain associated with inflammation or ischemia in animals and humans, the few studies where biphasic pulsed currents (as typically used for TENS) have been compared with interferential current have not found one to be more effective than the other, although one study found that the effects of interferential current lasted longer

What is premodulated current?

an alternating current with a medium frequency and sequentially increasing and decreasing current amplitude, produced with a single circuit and only two electrodes

this current has the same form as an interferential current that is produced by the interference of two medium–frequency sinusoidal ACs that requires four electrodes

the advantages of interferential current, including a lower current amplitude being delivered to the skin and a larger area of stimulation, are not reproduced by premodulated current

What is pulsed current?

an interrupted flow of charged particles where the current flows in a series of pulses separated by periods when no current flows

the current may flow in one direction only or flow back and forth during each pulse

a series of pulses where the charged particles move only in one direction is known as a monophasic pulsed current

a series of pulses where the charged particles move in one direction and then in the opposite direction is known as a biphasic pulsed current

What is monophasic pulsed current?

monophasic pulsed currents may be used for any clinical application of electrical stimulation but are most commonly used in tissue healing and acute edema management applications

the most commonly encountered monophasic pulsed current is HVPC, (also known as pulsed galvanic current)

this waveform is made up of pulses composed of–a pair of short, exponentially decaying phases, both in the same direction

What is biphasic pulsed current?

a biphasic pulsed current may be symmetrical or asymmetrical, and if asymmetrical, may be balanced or unbalanced

with a symmetrical or a balanced asymmetrical biphasic pulsed current the charge of the phases are equal in amount and opposite in polarity, resulting in a net charge of zero

with an unbalanced asymmetrical biphasic current the charge of the phases are not equal, and there is a net charge

in general, the biphasic pulsed current waveforms available are balanced

although there is often little clinical difference in the effects of symmetrical and asymmetrical pulsed currents, one study found that subjects found asymmetrical biphasic waveforms to be more comfortable when used to produce contractions of smaller muscle groups, such as the wrist flexors or extensors, and symmetrical biphasic waveforms to be comfortable when used to produce contractions of larger muscle groups, such as the quadriceps

What is Russian protocol?

Russian protocol is a waveform with specific parameters intended for quadriceps muscle strengthening

this protocol was developed by Kots who was involved in the training of Russian Olympic athletes

it uses a medium frequency AC with a frequency of 2500 Hz delivered in 50 bursts/second

each burst is 10 ms long and is separated from the next burst by a 10 ms interburst interval

this type of current is also known as medium–frequency burst AC (MFburstAC), and when this term is used, the frequency of the medium–frequency current or the bursts may be different from the original protocol

What is frequency?
the number of cycles or pulses per second

frequency is measured in Hertz (Hz) for cycles or pulses per second (pps) for pulses
What is the interphase interval (intrapulse interval)?
the time between phases of a pulse
What is the interpulse interval?
the time between pulses
What is on:off time?
on time is the time during which a train of pulses occurs

off time is the time between trains of pulses when no current flows

on and off times are usually only used when electrical stimulation is used to produce muscle contractions

during the on time, the muscle contracts, and during the off time it relaxes

the off times are needed to reduce muscle fatigue during the stimulation session

the sequential on and off times also attempt to mimic the voluntary contract and relax phases of normal physiological exercise

the relationship of the on and off time is often expressed as a ratio, for example, if a muscle is stimulated for 10 seconds and then allowed to relax for 50 seconds, this may be written as a 10:50 second on:off time or a 1:5 on:off ratio
What is phase duration?
the duration of one phase of a pulse

phase duration is generally expressed in microseconds (μs = 10 –6 seconds) or milliseconds (ms = 10 –3 seconds)
What is pulse duration?
the time from the beginning of the first phase of a pulse to the end of the last phase of a pulse

pulse duration is generally expressed in microseconds (μs= 10 –6' seconds)
What is ramp up/ramp down time?
the ramp up time is the time it takes for the current amplitude to increase from zero, at the end of the off time, to its maximum amplitude during the on time

a current ramps up by having the amplitude of first few pulses of the on time gradually be sequentially higher than the amplitude of the previous pulse

the ramp down time is the time it takes for the current amplitude to decrease from its maximum amplitude during the on time back to zero
Why is ramp time used?
ramping is used to produce a "soft start," allowing patients to become accustomed to the stimulation as it increases to reach motor threshold

the ramp up time is generally included in the on time while the ramp down time is generally included in the off time

ramp up and ramp down time are different from rise and decay time; the latter describe the time for the current amplitude to increase and decrease during a phase.
What is rise time/decay time?
rise time is the time it takes for the current to increase from zero to its peak during any one phase

decay time is the time it takes for the current to decrease from its peak level to zero during any one phase

note that this is different from ramp up/ramp down time
What is wavelength?
the duration of 1 cycle of AC

a cycle lasts from the time the current departs from the isoelectric line (zero current amplitude) in one direction and then crosses the isoelectric line in the opposite direction to when it returns to the isoelectric line

the wavelength of alternating current is similar to the pulse duration of pulsed current
What is amplitude (intensity)?
the magnitude of current or voltage
What is amplitude modulation?
variation in peak current amplitude over time
What is burst mode?
a current composed of series of pulses delivered in groups known as bursts

the burst is generally delivered with a preset frequency and duration

burst duration is the time from the beginning to the end of the burst

the time between bursts is called the interburst interval

PD/PW = 200 – 300 microsec (HIGH)
A = local motor contraction
F/R = 1 – 10 bps (LOW)
Time = approx. 30 min.

for acute and chronic pain, but primarily chronic because producing a contraction and a long pulse duration would likely be too uncomfortable for acute pain
What is frequency modulation?
variation in the number of pulses or cycles per second delivered
What is modulation?
any pattern of variation in one or more of the stimulation parameters

modulation is used to limit neural adaptation to an electrical current and may be cyclic or random
What is phase duration or pulse duration modulation?
variation in the phase or pulse duration
What is scan?
amplitude modulation of an interferential current

amplitude modulation of an interferential current moves the effective field of stimulation, causing the patient to feel the focus of the stimulation in a different location

this may allow the clinician to target a specific area in soft tissue.
What is sweep?
the frequency modulation of an interferential current
What is accommodation?
a transient increase in threshold to nerve excitation
What is adaptation?

a decrease in the frequency of action potentials and a decrease in the subjective sensation of stimulation that occurs in response to electrical stimulation with unchanging characteristics

What is accommodation?

When a stimulus sufficient to cause depolarization of a cell membrane remains unchanged, the resting potential of the membrane rises to above its pre-stimulus level. When the nerves rate of depolarization decreases while the depolarization stimulus remains unchanged.

What is habituation?

the CNS process of filtering out a continuous, non-meaningful stimulus.

What is Sensory level?

Stimulation depolarizes only sensory nerves. This level is found by increasing the output to the point at which a slight muscle twitch is seen or felt and then decreasing the output intensity by ~10%

What is motor level?

Stimulation is an intensity that produces a visible muscle contraction without causing pain.

Direct Current


(Ionto)

uninterrupted, unidirectional flow of electrons



DC can produce polarity-based changes in the tissue, resulting in ions being moved to and from the area


iontophoresis: medication delivery low voltage stimulation

Alternating Current


(Interferential)

uninterrupted, bidirectional flow of electrons


high frequency of the AC decreases skin resistance leading to a more comfortable current


Interferential - pain control, muscle contractions


Premod - NEMS - muscle contractions

Pulsed Current


(Hi Volt Pulsed)

Monophasic unidirectional flow of electrons marked by periods of non-current flow



monophasic currents are applied to the body with a known charge under each electrode. The resulting current can depolarize sensory and motor nerves.


HI Volt pulsed - muscle contractions, pain control

Biphasic Symmetrical


(NMES)

each phase is a mirror image of the other


the electrode carries equal positive and negative charges


there is no residual electrical charge


NEMS

Biphasic Asymmetrical Balanced


(TENS)

the two phases do not match each other


the two phases carry equal electrical charges


the shape of the pulse allows for greater positive (anodal) or negative (cathodal) effects. Net electrical charge is 0


TENS pain control

Biphasic Asymmetrical Unbalanced


(NmENS)

the two phases do not carry equal electrical charges


the shape of the pulse allows for greater positive (anodal) or negative (cathodal) effects



NEMS

Excitable Tissues

Nerves, muscle fibers, cell membranes

Non-Excitable Tissues

bones, cartilage, tendons, adipose tissue and ligaments

Electrode size

the size of the electrode is inversely proportional to the current density. as the size of the electrode increase the current density decreases

Muscle fibers and conductivity

muscle fibers are 4x more conductive when the current flows in the direction of the fibers than when it flows across them

Bipolar technique

bipolar technique requires the use of electrodes that are equal or nearly equal in size



if electrode A is placed over a motor point or other hypersensitive area and electrode B is not, the effects of the treatment will be weighted towards electrode A

Monopolar technique

this technique involves the use of 2 classifications of electrodes



1. active electrode


2. a dispersive electrode

Quadrapolar technique

involves the use of two sets of electrodes, each originating from its own electrical channel


this is the concurrent application of two bipolar circuits


ex. interferential

Subsensory level

stimulation occurs between the point at which the output intensity rises from zero to the point where the patient first receives a discrete electrical sensation

Sensory level

stimulation depolarizes only sensory nerves. This level is found by increasing the output to the point at which a slight muscle twitch is seen or felt and then decreasing by intensity 10%

Motor level

stimulation is an intensity that produces a visible muscle contraction without causing pain

Noxious level

stimulation is current applied at an intensity that stimulates pain fibers

Voltage vs. Amperage

Voltage: measures the pressure, or FORCE, of electricity, the force that causes charged particles to move



Amperage (Amps): is a measure of the AMOUNT of electricity used, the rate at which electrical current flows


The amps multiplied by the volts gives you the wattage (watts),

Interferential Stimulation


Pain Control via Gate Mechanism

Carrier Freq. based on patient comfort


Burst Freq: 80 - 150 Hz


Sweep: fast


Electrode Arrangement: quadrapolar


Output Intensity: strong sensory level


Treatment duration: 20 - 30 minutes

Interferential Stimulation


Pain Control via Opiate Release

Carrier Freq. based on patient comfort


Burst Freq: 1 - 10 Hz endorphin


80 - 120 Hz enkephalin


Sweep: slow


Electrode Arrangement: quadrapolar


Output Intensity: moderate to strong sensory level


Treatment duration: 20 - 30 minutes