Therapeutic Electrical
Modalities
Learning Objectives
Be familiar with the characteristics of
electric modalities that are applied for
therapeutic purposes
Identify physiological and therapeutic
effects of electric modalities
Be familiar with contraindications and
precautions in using electric modalities
Identify adverse effects for each
modality
Learning Objectives Cont’d . . .
Be familiar with the multiple uses of
electrical stimulation (ES)
When given a clinical scenario, be able
to:
–
–
–
–
Define goals of treatment with ES
Choose the appropriate device
Select the appropriate parameters
Apply the treatment safely and
competently
– Modify treatment if needed
Therapeutic Electrical
Currents
The application of electrical current to
the body for therapeutic purposes, such
as:
– Pain relief
– Neuromuscular Electrical stimulation
– Tissue/wound healing
– Direct stimulation of denervated
muscle
Terminology
Charge
Current
Resistance
Conductance
Impedance
Current:
– AC
– DC
– Pulsatile/pulsed
Amplitude
intensity
or
Pulsed currents
Monophasic or biphasic
Pulse duration
Pulse frequency
- interval between pulses
– can be manipulated independently
Modulations
– Frequency
– Amplitude
– Burst
Therapeutic Electrical
Stimulation Applications
Pain Relief
Neuromuscular Electrical Stimulation
(NMES)
Tissue/wound healing
Iontophoresis
Deinervated muscle
Transcutaneous Nerve
Stimulation
(TENS)
TENS
Stimulates nerve fibers for the
symptomatic relief of pain
Device applies an electrical signal through
lead wires and electrodes attached to the
patient's skin
Electrode placement varies:
– Typically placed in a peripheral nerve
distribution
– Locations can be distal or proximal to pain
site
How It Works
Gate Control Theory:
– Pain signals can be blocked at the level of
the spinal cord before they are
transmitted to the thalamus
– TENS stimulates large Ia myelinated
afferent nerve fibers that stimulate the
substantia gelatinosa in the spinal cord,
closing the gate on pain transmission to
the thalamus
Gate Control Theory
Physiological Effects of TENS
Selective stimulation of large diameter,
myelinated fibres
– Gate Control Theory
Stimulates release of endorphins
– Endorphin/opiate theory
Stimulates release of other transmitters
– NA, 5-HT
?mild heating  enhanced healing?
Placebo
Therapeutic uses of TENS
PAIN RELIEF:
–
–
–
–
–
–
Acute, Subacute, Chronic & Referred
Musculoskeletal
Neurologic
Obstetric
Oncologic*
Cardiac- angina
Modes of TENS
Conventional
Acupuncture
Burst mode
Brief-intense/noxious level
Conventional TENS
High-frequency, low-intensity stimulation
– most effective type of stimulation
Amplitude is adjusted to produce minimal
sensory discomfort
Pain relief begins after 10–15 minutes
and stops shortly after removing
stimulation
Useful for neuropathic pain
Duration of treatment is 30 minutes to
hours
Acupuncture
Low frequency, high intensity stimulation
Amplitude high enough to produce muscle
contraction
Onset of pain relief can be delayed several
hours
Pain relief persists hours after removing
stimulation
Useful for acute musculoskeletal conditions
Treatment sessions last 30–60 minutes
Burst Mode
High frequency stimulation bursts at
low frequency intervals
Delayed onset of pain relief
Treatment can range 30–60 minutes
Brief-intense/Noxious Level
Hyper-stimulation
High frequency, high intensity
stimulation
It is considered that this mode
stimulates C-fibers causing counterirritation
Rarely tolerated more than 15–30
minutes
TENS Unit
intensity
timer
Pulse width
frequency
mode
TENS Dosage
Conventional
Burst mode
Brief Intense
80-125 pps
2 bursts per
sec
220-250
125 pps
Comfortable
tingling
Muscle twitch
Strong
sensation
Acute pain,
fast relief
Deep, chronic
achy pain
Rapid relief
for intense
pain
60-100
microsec
250
Modulation Modes
SD: strength-duration
– Amplitude and width modulate alternately – subtle
change in sensation
– Allows higher total amount of charge to be used
MW: modulated width
– Stronger Weaker
MR: modulated rate
– Faster  Slower
CM: combination modulation
– Rate and width
– ‘Diffuse’ sensation
Electrode placement
Single channel:
– 2 electrodes
Dual channel:
– 4 electrodes
Single channel
Surround the pain
Over the pain
Within dermatome/myotome
On trigger points or acupuncture points
within dermatome
Spinal segment: one near spine, other
over pain or trigger point within the
dermatome/myotome
Dual channel
Bracket
Cross – fire
Bilateral placement- both limbs
Contralateral:
– Phantom pain, skin irritation or wound
General placement: flood the limb
– Overlap channels
Precautions
Decreased sensation
Pregnancy
Malignancy
Decreased mentation
Be careful with repeated applications and prolonged use, adhesives/tape
and gel can all cause dermatitis
Make sure the entire electrode has good coverage for gel and don’t
use too high a current - can cause electrical burns on the skin!
Contraindications
UNDIAGNOSED PAIN
ANY electronic implant
– Some Pacemakers (fixed rate ok but
rate responsive are affected)
– Cardioverter-defribrillators
– Some Bladder stimulators
Metal implants???
Interferential Current
(IFC)
Interferential Current
Another form of TENS:
– Differs from TENS as it allows deeper
penetration with more comfort (compliance)
and increased circulation
AMC (amplitude modified current)
Frequencies interfere with the
transmission of pain messages at the
spinal cord level
How does it work?
2 “medium frequency” currents
– Low frequency (e.g. TENS) = <1000Hz
– Medium frequency 1000-10,000 Hz
2 currents with different frequencies
Currents ‘interfere’ with one another
“Beat frequency” is the difference
between the 2 currents
Example
– C1 = 5000 Hz
– C2= 5100 Hz
– fixed Beat
frequency = 100
bps
Indications for IFC
Urinary incontinence
Pain relief
Blood flow/edema management
– May be effective due to the combination
of pain relief (allowing more movement),
muscle stimulation and enhanced blood flow
TENS vs. IFC
Physiological effects:
– Depolarize sensory and motor nerves
Why not TENS?
– “Medium frequency”  less skin impedance
– Less impedance  more patient comfort
– More patient comfort  tolerate higher
amplitude current  deeper penetration
Contraindications
Same as TENS
Plus:
– With suction cup electrodes:
Bruising
Cross-infection from sponges
IFC Application
Stimulator type
Electrode placement
– As precisely as possible so that patient
feels the stimulation over the targeted
area
Electrode fixation
– Self-adhesive pads
– Non-adhesive taped in place
Coupling medium
– Gel for electrode pads
Sweep
Beat frequency is modulated
Thought to prevent adaptation
E.g.
– C1 fixed at 5000
– C2 varies
– Gives a VARIABLE BEAT FREQUENCY
Uses of sweep
Sweep ranges:
– Pain relief 80-150 bps
– Muscle rehab 10-100 bps
– Edema 1-10 bps (intermittent muscle
contractions)
– Selection of a wide frequency i.e 1-100Hz is
less efficent + ? Counter-productive
Set-Up of IFC
Bi-polar
Quadripolar
Quadripolar with scan
Bi-polar method
“Pre-mod”
2 electrodes
Single channel
Current is ‘modulated’ within the machine
Similar to TENS
Quadripolar method
4 electrodes
2 channels
Interference occurs where the fields cross one
another WITHIN the tissues
Cloverleaf pattern
Quadripolar field
Quadripolar With Scan
“Automatic vector scan”
AMPLITUDE is varied by the machine
E.g.
– C1 fixed amplitude/intensity
– C2 variable amplitude
Pattern of interference is different
Quad With Scan
IFC Scan
Uses of scan:
– Large area of treatment
– Diffuse pain
– Location of pain difficult to
pinpoint
Neuromuscular Electric
Stimulation
(NMES)
NMES
Consists of transcutaneous electrical
stimulation for muscles with or without
intact PNS, or central control
– More powerful than TENS unit
Multiple muscles can be activated in a
coordinated fashion to attain certain functional
goals (ambulation, transfers)
Types of Muscle Contraction
Voluntary:
– Recruits Type I first, then Type 2
– Spatial summation
Recruitment of additional motor units
– Temporal summation
Increased firing rate
– Gradual increase in force generated
Types of Muscle Contraction
Electrically stimulated contraction:
– Reverse pattern of recruitment
Type II Type I
– All motor units fire at once
– Easy to produce fatigue
Use “Ramp up” for comfort
Features of NMES Currents
Pulse duration
Pulse rate/frequency: 30-50 pps
Therapeutic Uses of NMES
Strengthens muscles
Motor Re-education
Increases ROM
Enhances endurance
Reduces muscle spasm/spacity
Strength Training
Recruits maximum numbers of motor
units
Used if volitional control affected by
– pain
– reflex inhibition
– motivation
Works by overload fatigue
Strength Training
Can improve strength but not as well as:
– voluntary contraction
– ES + voluntary contraction
“high load/low reps”
Longer rest periods
Motor Re-Education
Use NMES for:
– Contraction is not readily under
voluntary control (e.g. pelvic floor)
– Teaching a new action (e.g. tendon
transfer)
– Injured peripheral nerve is
regenerating
Motor re-education
Demonstration to convince patient that
contraction IS possible (e.g. hysterical
paralysis)
Enhanced recruitment or timing during a
functional movement:
– Functional Electrical Stimulation
Related to a particular task e.g. sit-to-stand,
hand to mouth
Increase ROM
Stretch contractures *
Contract-relax
Facilitate tendon glide
Break adhesions *
*Patient may not be able to generate
sufficient force
Enhance Endurance
Use sub-maximal force over longer
period of time
Similar to low load/high reps at the gym
Equal work and rest periods
Promote circulation
Muscle pump
Prolonged immobilization
Prevents complications from immobility
such as deep vein thrombosis (DVT), and
osteoporosis
Low load, high reps
Decrease spasm/spasticity
Stimulate antagonist
– reciprocal inhibition
Stimulate agonist
– fatigue
Stimulate both alternately
Contraindications and
Precautions
The Big Five
Carotid sinus
Venous or arterial thrombosis/
thrombophlebitis
Areas of skin irritation
Open wounds
Features of NMES Currents
On time
Off time
Rise time/ramp up
Fall time/ ramp down
IFC Set-Up
Size matters!
– Small electrodes  concentrates the
charge  greater effect
– Larger electrodes  dissipates the charge
 can tolerate greater amplitude
Match electrode size to the size of the
muscle
Set-Up Continued
Conductivity matters!
– Skin prep
Sensation testing
Skin prep
– Coupling medium:
Lots of gel
Cover ENTIRE electrode
No gel on skin between electrodes
Set-Up Continued
Location matters!
– Parallel to muscle fibers
– Over motor points
– Farther apart  deeper penetration of
current?
– No closer than ½ the diameter of each
electrode
– Precision vs. overflow
Adverse Affects
Electrical burn due to fold or poor gel
technique
Skin irritation
Iontophoresis
What is it?
Introduction of ions into the body using
direct electrical current
Transports ions across a membrane or
into a tissue
Painless, sterile, noninvasive technique
Demonstrated to have a positive effect
on the healing process
Continued . . .
Low-level electrical current carries drug
ions through the skin and into underlying
tissue
Type of medication used will be based
on the desired effect to the treated
area
– Most common medication is Dexamethasone
How it Works
Electrical unit uses a direct current
that is either a positively or negatively
charged active electrode
An oppositely charged dispersive
electrode is attached
The medication is placed on the active
electrode so that the active electrode
has the same charge as the medication
Continued . . .
When the electrodes are placed on the
skin and activated, the charge from the
electrode will drive the medication away
from the electrode and into the area
being treated
The electrical charge will push the
medication through the skin and into
the tissue to be treated
Indications
Inflammation
Edema
Bone spurs/calcium deposits
Fungal infections
Scars
Wounds
Muscle spasms
Physiological and Therapeutic
Effects
Physiological:
– Decreased edema and
inflammation
– Pain control
– Tissue adhesion
– Decreases muscle
spasm
– Wound healing
Therapeutic:
– Delivers medication
at a constant rate so
the effective plasma
concentration
remains within the
therapeutic window
for an extended
period of time
Therapeutic window
The range between the minimum plasma
concentration of a drug necessary for a
therapeutic effect and the maximum
effective plasma concentration (above
which adverse effects may occur)
Preparing the Patient for ES
Sensory testing:
– Which sensation?
– Why?
Skin prep
– Remove oil
– Moisten
Hair
– Clip, don’t shave
Iontophoresis Generator
 Intensity: 3-5 mA
 Unit adjusts to
normal variations
in tissue
impedance
Reduces the
likelihood of burns
 Automatic
shutdown
Iontophoresis Generator
 Adjustable Timer
Up to 25 min
Iontophoresis Generator
 Lead wires
Active electrode
Inactive electrode
Current Intensity
Low amperage currents are more
effective than high currents
– Higher currents tend to reduce effective penetration
Recommended current: 3-5 mA
Maximum current may be determined by
the size (surface area) of the active
electrode
– Current may be set so that the current density
under the active electrode falls between 0.1 0.5 mA/cm2
Current Intensity
Increase current slowly until patient
reports tingling or prickly sensation
If pain or a burning sensation occurs,
current is too great and should be
decreased
When terminating treatment, current
should be slowly decreased to zero
before electrodes are disconnected
Treatment Time
Ranges between 10-20 min
Check skin every 3-5 minutes for signs
of irritation
Decrease current during treatment to
accommodate for decrease in skin
impedance to avoid pain or burning
Dosage of Medication
Dosage is expressed in milliampereminutes (mA-min)
Total drug dose delivered (mA-min) =
current X treatment time
Typical iontophoresis drug dose is 40
mA-min
Traditional Electrodes
Older electrodes made of tin, copper,
lead, aluminum, or platinum backed by
rubber
Completely covered by sponge, towel, or
gauze which contacts skin
Absorbent material is soaked with ionized
solution (medication)
Commercial Electrodes
Electrodes have a small chamber covered by
a semi-permeable membrane into which
ionized solution may be injected
The electrode self adheres to the skin
Electrode Preparation
Shave and clean skin
prior to attaching the
electrodes to ensure
maximum contact
Do not excessively
abrade the skin during
cleaning
Damaged skin has lower
resistance to current
– Increased risk of
burns
Electrode Preparation
Attach self-adhering
active electrode to
skin
Electrode Preparation
Inject ionized solution
into the chamber
Electrode Preparation
Attach self-adhering
inactive electrode to
the skin and attach
lead wires from the
generator
Electrode Placement
Size of electrodes can cause variation in
current density
– Smaller = higher density
– Larger = lower density
Electrodes should be separated by at least
the diameter of active electrode
 Wider separation minimizes superficial current
density
 Decreased risk for burns
Electrode Placement
Selecting the Appropriate Ion
Negative ions (medication) driven into
tissues by the negative lead
– Accumulation of negative ions in the tissues
 Produces an acidic reaction through the
formation of hydrochloric acid
Results in hardening of the tissues by
increasing protein density
Continued . . .
Positive ions (medication) driven into
tissues by the positive lead
– Accumulation of positive ions in the tissues
 Produces an alkaline reaction through
the formation of sodium hydroxide
Results in softening of the tissues by
decreasing protein density
 Useful in treating scars or adhesions
 Some positive ions may also produce an
analgesic effect
Selecting the Appropriate Ion
Inflammation
 Dexamethasone (-)
 Hydrocortisone (-)
 Salicylate (-)
Spasm
 Calcium (+)
 Magnesium (+)
Analgesia
 Lidocaine (+)
 Magnesium (+)
Edema
 Hyaluronidase(+)
 Salicylate (-)
 Mecholyl (+)
Open Skin Lesions
 Zinc (+)
Scar Tissue
 Chlorine (-)
 Iodine (-)
 Salicylate (-)
Adverse Effects
Chemical burns
Thermal burns
Skin irritations
Patient Preparation
For All Types of ES
Preparing the Patient
Explain what, why, how
– What:
full name plus ‘translation’ of what it is
– Why:
Pain relief, muscle strengthening, etc
– How:
Gate control?
Opiate release?
Preparing the Patient
Sensation testing
Test/demonstrate on yourself first
– Check for
broken leads
dead batteries
Sensitive dials
– Gain confidence of patient
Preparing the Patient
Prepare electrodes
– Plug the leads in first
– Use correct gel
No gel BETWEEN electrodes!
– Moisten self-adhesive electrodes or IFC
pads WELL
Tape or strap electrodes securely
Questions??
Comprehension Check
1. What are the 4 main purposes of
2.
3.
4.
5.
applying therapeutic electric currents?
What pain mechanism is affected by
the use of TENS?
What are the 4 modes of TENS?
Which would be used for chronic pain?
What are the contraindications for
TENS?
When and why is IFC used over TENS?
Comprehension Check
6. How should the electrodes be set up to
achieve a quadipoloar field for IFC?
7. What are the therapeutic uses for
NMES?
8. What are the indications for
iontophoresis?
9. How is the maximum current of
iontophoresis determined?
10. What is the typical dosage of a drug for
iontophoresis?
Answers
1. The 4 main purposes of applying
therapeutic electric currents are:
–
–
–
–
Pain relief
Neuromuscular Electrical stimulation
Tissue/wound healing
Direct stimulation of denervated muscle
2. The pain mechanism affected by the
use of TENS is the gate control theory
Answers
3. The 4 modes of TENS are:
– Conventional
– Acupuncture
– Burst mode (used for chronic pain)
– Brief-intense/noxious level
Answers
4. The contraindications for TENS are:
– UNDIAGNOSED PAIN
– ANY electronic implant
Some Pacemakers (fixed rate ok but rate
responsive are affected)
Cardioverter-defribrillators
– Some Bladder stimulators
– Metal implants???
Answers
5. IFC is used over TENS because:
– “Medium frequency”  less skin impedance
– Less impedance  more patient comfort
– More patient comfort  tolerate higher
amplitude current  deeper penetration
6. To achieve a quadipolar field for IFC
the electrodes from the same circuit
diagonal to each other forming a box
around the target site
Answers
7. The therapeutic uses for NMES are:
–
–
–
–
–
Strengthens muscles
Motor Re-education
Increases ROM
Enhances endurance
Reduces muscle spasm/spacity
Answers
8. The indications for iontophoresis are:
– Inflammation
– Edema
– Bone spurs/calcium deposits
– Fungal infections
– Scars
– Wounds
– Muscle spasms
Answers
9. The maximum current of iontophoresis
is determined by the size (surface
area) of the active electrode
10. The typical dosage of a drug for
iontophoresis is 40 mA-min