1
Q
General Uses of E-Stim
A
- Most forms of e-stim can be manipulated to cause the following:
~ Sensory sensation/tingle
~ Muscle contraction
~ Pain
2
Q
Principles of Electricity: Electrical Current
A
- Electrical Current
~ Flow of electrons is an attempt to
equalize the charges between points
> Electrons are very small particles
of matter possessing a negative
charge
~ Flows from the negative pole to the
positive pole on a path of least
resistance
> Electrons are transferred from
atom to atom
3
Q
Negative Pole vs Positive Pole
A
- Negative Pole
~ Area of high electron concentration
and high electrical potential - Positive Pole
~ Area of low electron concentration
and low electrical potential
> Attracts other electrons - Current always flows from negative to positive
4
Q
Principles of Electricity: Resistance or Impedance
A
- Degree of opposition to the flow of electrical current
- All materials have some resistance
- The higher the resistance, the lower the flow
~ Conductor is material that allows for
relatively free flow of electrons
(metals, electrolyte solutions)
> Electrolytes are minerals that
dissolve in solution as electrically
charged particles (Na, K, Cl, Mg)
~ Resistor is material that oppose the
flow of electrons (air, wood)
5
Q
Principles of Electricity: Electrical Circuits
A
- Path of a current from a power source through one or more components back to the generating source
- Series Circuit
~ Only one path for the flow of
electrons; current is constant - Parallel Circuit
~ Electron flow is given alternative
pathway for travel
> Electrons will travel on the paths
of least resistance
> The current fluctuates depending
on the resistance of the paths:
less resistance = current will
always chose it
6
Q
Principles of Electricity: Current Flow Through the Body
A
- Best conductors within the body are the tissues containing high amounts of water due to high electrolyte contact
~ More water = less resistance = more
current - Electrical current enters deeper tissues as a parallel circuit due to the differences in water content between the tissue types
- Nerves are the tissues we want to reach the most
7
Q
Principles of Electricity: Good Vs. Poor Conductors
A
- Good Conductors: 70-75% Water Content
~ Muscle
~ Nerve
~ Blood - Poor Conductors: 20-30% Water Content
~ Bone
~ Tendons
~ Fascia
~ Adipose
~ Skin
8
Q
Current Types: Direct
A
- Continuous flow of electrons in one direction (negative to positive)
- Pattern Flow
~ Square wave with continuous current
flow on only one side of the baseline - Return to baseline when current is interrupted
- Not used very often
- Only current that can directly tell muscle to depolarize = bad
9
Q
Current Types: Alternating
A
- Direction and magnitude of the flow reverses
- No true positive or negative pole, electrodes take turns being the negative and positive poles
~ Vibrating back and forth - Frequency
~ Number of times the current reverses
direction in 1 sec
10
Q
Pulsed Currents
A
- Direct or Alternating currents are interrupted by periods of non-current flow
- Phase
~ Individual section of a pulse that rises
above or below the baseline - Pulse
~ An individual waveform
> Monophasic: one phase to each
pulse
• Unidirectional; Direct
> Biphasic: two phases per pulse
• One phase above and one
phase below the baseline;
Alternating - Pulse Duration/Pulse Width
~ Time from the beginning of the
phase to the conclusion of the final
phase - Pulse Frequency
~ Number of pulses per second - Interpulse Interval
~ Time between the conclusion of one
pulse and the start of the next
~ Allows for repolarization of nerve
membranes and mechanical events
(muscle relaxation)
11
Q
Physiological Effects of Electrical Current
A
- Excitatory Effects (what we want)
~ Alter Membrane Charges
> Neve
> Muscle
> Cell - Nonexciatory Effects
~ Temperature rises in a conducting
tissue
> Higher resistance gives increased
heat
~ Chemical
12
Q
Electrical Nerve Stimulation: Intensity and Phase Duration
A
- The greater the intensity the greater the ability to stimulate nervous tissue
- The greater the phase duration the greater the ability to stimulate nervous tissue
- Overall current strength is a producer of both intensity and phase duration
~ If one is decreased the other must
increase for the same effect
13
Q
Order of Stimulation
A
- Related to depth and size of nerve
~ Sensory Nerves (most superficial)
~ Motor Nerves
> Deeper than pain receptors but
are larger in diameter and
therefore stimulated first
~ Pain Receptors
> Smaller in diameter and less
myelinated
14
Q
Chemical Effects of Electrical Current
A
- Only possible with Direct Current
- Current causes migration of the charged ions within tissues towards the pole opposite of polarity
~ Negative ions to positive and negative
to the negative
15
Q
Chemical Effects of Electrical Current: Concentration
A
- Concentration of negative ions produces a more ACIDIC environment in which there’s coagulation of protein and hardening of tissues
- Concentration of positive ions produces a more ALKALINE environment causing liquefying of proteins and softening of tissues
16
Q
Accommodation and How to Combat it
A
- Accommodation is specific nerves stimulated by a constant stimulus that become less excitable or unexcitable
~ Pt. doesn’t feel anything anymore
because the nerves started to become
used to it and ignore it - Combating it
~ Intensity Changes
~ Pulse Width Changes
~ Frequency Changes
~ Burst: period of non current flow
interrupting a number of pulses
17
Q
General Uses of Electrical Stimulation
A
- Most forms of electrical stimulation can
be manipulated to cause the following:
~ Muscle Contraction
~ Sensory Sensation
~ Pain
18
Q
General Uses of Electrical Stimulation: Muscle Contraction
A
- Causes contraction by stimulating motor nerves except for denervated muscle where only DC can be used to cause direct muscle fiber depolarization
~ Muscle strengthening /
neuromuscular re-education
~ Edema removal
19
Q
General Uses of Electrical Stimulation: Sensory Stimulation
A
- Ascending pain modulation
- Edema prevention
20
Q
General Uses of Electrical Stimulation: Pain Stimulation
A
- Descending pain modulation
21
Q
Venous and Lymphatic Return Mechanisms
A
- Skeletal Muscle Contraction
~ Veins and lymph vessels have one-
way valves
> Permit flow toward the heart
and prevents back-flow
~ Vessel compression increases the
pressure which closes upstream
valves and opens downstream valves
~ Contraction forces blood and lymph
forward in the vessels - If the concentration gradient is altered, fluid will flow from tissues to vessels which is good
22
Q
Electrode Placement for Motor Level Stimulation
A
- Electrodes/Electrical Current should be placed over or through the muscle’s motor point.
~ Location where motor nerves and
blood vessels enter muscle
~ Usually located in the middle or belly
of the muscle - Current needs to cross motor point in order to contract muscle
23
Q
Motor Level Stimulation: Intensity
A
- Strength of contraction increases as amount of current increases
~ Strength of contraction is limited by
the tolerance of pt. for the current
> Maximum tolerated is usually
around 30% of maximum
contraction - Depth of penetration increases as the amount of current increases
~ Increases the number of motor nerve
fibers stimulated
24
Q
Motor Level Stimulation: Pulse/Phase Width
A
- Narrow pulse/phase widths require more intensity for muscle contraction
- Wide pulse/phase widths require less intensity for muscle contraction
~ Produce strong contraction quicker,
but run into the pain threshold
quicker - The wider the pulse width, the better
25
Motor Level Stimulation: Pulse Frequency
- Rate = <15 pps
~ Produces distinguishable muscle
contraction for each pulse
~ Allows muscle to mechanically return
to resting length before the next
pulse
~ Edema Removal
- Rate = >30 pps
~ Produces tetany (constant
contraction)
~ Muscle Strengthening/
Neuromuscular Re-education
~ Needs a duty cycle
> If not, muscle would be
contracted for full Tx time = bad
- Low Frequency = on/off contraction
- High Frequency = tetany
26
Pain Modulation
- Ascending (Sensory)
~ Pulse/Phase Width = Narrow
~ Pulse Frequency = High
~ Intensity Level = Sensory
- Descending (Pain)
~ Pulse/Phase Width = Wide
~ Pulse Frequency = Low
~ Intensity Level = Pain
27
Electrodes
- Form a closed circuit between the generator and the body
~ Size: smaller electrodes result in high
current density and require less
intensity to be effective
28
Electrode Distance from Each Other
- Close
~ Current flows superficially and is
more specific
- Far
~ Current reaches deeper and is more
generalized
29
Electrode Placement for Muscle Stim
- Electrodes should be placed so that current flows in the same direction as the direction of the muscle
~ Increased conduction when current
flows in the same direction as muscle
fibers (4 times better)
30
Electrode Set Up: Monopolar
- Active Electrode: Placed in the treatment area
- Dispersive Electrode: Placed outside the treatment area to complete the circuit
- The dispersive electrode is significantly larger with low current density resulting in little or no stimulation outside the treatment area
- The high current density under the active electrode focuses the effect of the treatment within the treatment area
- Better for smaller areas and used if a positive pull is just wanted
31
Electrode Set Up: Bipolar
- Use of electrodes of near-equal size, both located in the treatment area
32
Electrode Set Up: Quadripolar
- Two sets of electrodes are used, each with a separate channel
- May intersect or be used parallel
33
Indications for E-Stim
- Pain
- Edema
- Muscle Spasm
- Muscle Weakness/Dysfunction
34
Contraindications for E-Stim
- Pacemaker
- Pregnancy
- Cancer
- Exposed Metal implants (external fixation)
35
Controversies in Treatment
- Sensory Level Edema Prevention - few studies have shown any effect and all are using an animal model
- No direct evidence that electrical current affects cell function to increase "healing"
- No direct evidence that electrical current
"drives out edema" in the absence of muscle contraction
36
High Voltage Pulse Stimulation
- Application of a pulsed monphasic (direct) current to the body with a known polarity under each electrode
- Short pulse width (narrow)
- Ability to deliver low pulse width allows for optimal activation of sensory and motor nerves while minimizing stimulation of pain fibers
- Interpulse interval is very long relative to the pulse duration
~ May allow for the dissipation of the
ions underneath the electrodes,
areas may not become acidic or
basic
37
High Volt Pain Control
- Ascending Control
~ Intensity = Sensory
~ Pulse Frequency = High
~ Pulse Width = Narrow
~ Electrode Placement = directly over
painful site
38
High Volt Muscle Stimulation: Intensity and Pulse Frequency
- Poor strengthening qualities due to short pulse width
- Intensity: Motor
- Pulse Frequency
~ Low/<15 pps for an individual
muscle contraction for each pulse
> Used for Edema Reduction
> Best results when multiple
muscle groups are used
~ High/35-50 pps for tetany
> Used for Re-education
39
High Volt Muscle Stimulation: Electrode Placement and Duty Cycle
- Electrode Placement
~ Bipolar
> Placed at proximal and distal ends
of muscle
~ Monopolar
> Active electrode placed over
motor point of muscle
• Negative Polarity
- Duty Cycle (Overall On/Off Time)
~ 20 % for re-education
~ Alternating for Edema Reduction
> One channel contracts while other
is off
40
High Volt Edema Prevention Effects
- Theory/Effects of Negative Polarity
~ Changes membrane charge:
decreases vessel permeability (limits
edema)
~ Vasoconstriction (limits circulation)
~ Negatively charged blood cells and
plasma proteins are repelled
creating gradient that encourages
reabsorption of fluids
41
High Volt Edema Prevention: Parameters
- Intensity = Sensory
- Pulse Frequency = High
- Pulse Width = Wide
- Polarity = Negative
- Electrode Placement
~ Monopolar: on or around affected
area
- Water Immersion
~ Whatever is immersed gets a tingle
instead of where one electrode is
placed
42
High Volt Wound Healing
- Theorized that negative polarity stimulates fibroblasts activity and epidermal cell migration
~ Indirectly observed through study of
pressure ulcers and the effect HVPC
has on wound healing size
~ Two groups of patients with
pressure ulcers or burns and
compare the level healing
43
Interferential E-Stim
- Two separate channels produce continuous biphasic current (AC)
~ Channel 1: high-frequency
4000-5000 Hz
~ Channel 2: variable frequency
- Currents from the two channels interfere with one another combining to form a new wave
~ New wave has a “beat” frequency
~ Not a pulsed waveform, but some
manufacturers refer to the beat
frequency as the pulse frequency
44
Interferential E-Stim: Beat Frequency
- Difference between channel 1 and channel 2
- The greater the difference between the two channels the greater the beat frequency
~ Ex. If channel 1= 4000Hz & channel
2 = 4050Hz the beat frequency is
50Hz
45
Advantages of IFC
- Electrical currents with lower frequency encounter more resistance at the skin, which means more current must be used to get past the skin
- IFC is able to penetrate deep tissues without discomfort due to high frequencies used in 2 channels
- Able to utilize low beat frequencies for strong motor response with less electrical current and discomfort
- Range = 1 to 299
46
IFC Pain Control
- Utilizes Ascending Control Mechanisms
~ High beat frequencies (80-150 z) at a
sensory intensity activate release of
endogenous analgesics
~ Theorized that low beat frequencies
(1-10 Hz) at a motor intensity
activate a release of Beta Endorphins
> Unable to confirm through
study, fairly easy to test this effect
47
IFC Edema Management
- Low beat frequency at a motor intensity
- How will this reduce edema?
~ Muscle contraction causes
compression of the lymphatic and
venous systems in order to “pump”
out edema
48
IFC Variables: Scan/Vectoring
- Varying the output of each channel
~ Channel intensities are scanned
alternately at a set % up or down
- Causes the field to rotate within the treatment area
~ Treats more surface area
49
IFC Variables: Beat Frequency
- Sweep (use for pain)
~ Frequency ramps from a high
frequency to a low frequency and
back to a high frequency
~ Allows for less accommodation
- Continuous/Fixed
~ Beat frequency remains constant for
the entire Tx
50
IFC Variables: Balance
- Dial that allows control of electrical current under each set of electrodes
- Used to equalize the sensory stimulation felt in the treatment area
51
Downside of IFC
- Needs a large treatment area in order to be beneficial
52
Premodulated E-Stim
- AC that’s mixed within the generator that produces a current similar to IFC
~ Produces beat frequencies similar to
IFC
~ Just like IFC, this isn’t a pulsed
frequency, but beat and pulse
frequency are used interchangeably
- Same applications as IFC when 4
electrode set up is practical
- Able to use same IFC variables (scan, sweep etc.)
- Should not be as good as IFC in reaching deep tissues without discomfort
- Frequencies are lower but it does not result in increased discomfort compared to IFC
53
Transcutaneous Electrical Nerve Stimulation (TENS)
- Application of an asymmetrical biphasic pulsed current
~ Low current flow and very narrow
pulse widths
~ Used for pain control
- Name is misleading
~ Usually refers to hand held
stimulators
> All forms of electrical stimulation
are technically transcutaneous
electrical nerve stimulation
54
TENS: Ascending Control
- Sensory
~ Intensity = Sensory
~ Pulse Frequency = High and/or
modulated
~ Pulse Width = Narrow
- Motor
~ Intensity = Motor
~ Pulse Frequency = Low
~ Pulse Width = Wide
55
TENS: Descending Control
- Intensity = Pain
- Pulse Frequency = Variable (Low is better)
- Pulse Width = Wide
56
TENS: Combating Accommodation
- Modulated
~ Unit alters the pulse frequency above
and below the initial setting
> Ex: 100 pps modulated between
90 and 110 pps for the duration
of Tx
- Burst
57
TENS: Electrode Placement
- Directly Over Pain
- Proximal/Distal to Pain
- Over Acupuncture Points
- Over Motor Point
- Along Dermatome
58
Russian Stim
- Used by Russian athletes prior to the 1972 Summer Olympics
~ Reported 30-40% increase over
voluntary muscle contraction
~ Claimed to be painless
~ Results never duplicated in scientific
studies
- 2500 Hz AC With a Burst Frequency (NOT PULSED)
~ Able to penetrate to deeper tissues
(muscle) with less discomfort just like
IFC
~ Able to cause strong muscle
contraction due to burst frequency
30-60 burst/second
~ Used to produce muscle contraction
for muscle reeducation mostly
59
Russian Stim Variables
- Ramp Time
~ Length of time to reach maximum
intensity (gradual contraction)
- Duty Cycle
~ Needed for multiple contractions
over course of treatment
- Contraction Time
~ Length of time (s) that the
contraction is maintained during
each cycle
- Rest Time
~ Length of time (s) that the muscle is
not contracting including ramp time
60
Neuromuscular Electrical Stimulation (NMES)
- Application of pulsed biphasic low frequency current
~ Produces strong muscle contractions
for re-education, strengthening or
muscle pump
~ Optimal for strong contractions due
to long pulse duration
~ Only form of electrical stimulation
that has been shown to strengthen
muscle
61
So which one do you use?
- First rule is to realize what all forms of e-stim can be manipulated to do
~ Muscle Contraction
~ Sensory Sensation
~ Pain
- Second rule is to understand what is different about each form and how it can be an advantage
- Third Rule is to use what works
62
Summary of Each Stim
- High Volt
~ Polarity
~ Pulse Width (narrow)
- TENS
~ Pulse Width (narrow)
~ Wave Form (asymmetrical)
~ Unit/Portable
- IFC
~ Initial Frequency/Beat (high)
- Premod
~ Beat
- Russian
~ Burst Frequency
- NMES
~ Pulse Width (wide)
