Principles of Electrical Currents

1
Principles of Electrical Currents

• HuP 272

2
Electricity is an element of PT modalities most
frightening and least understood.

• Understanding the basis principles will later aid
  you in establishing treatment protocols.

3
General Therapeutic Uses of Electricity

• Controlling acute and chronic pain
• Edema reduction
• Muscle spasm reduction
• Reducing joint contractures
• Minimizing disuse/ atrophy
• Facilitating tissue healing
• Strengthening muscle
• Facilitating fracture healing

4
Contraindications of Electrotherapy

• Cardiac disability
• Pacemakers
• Pregnancy
• Menstruation (over abdomen, lumbar or pelvic
  region)
• Cancerous lesions
• Site of infection
• Exposed metal implants
• Nerve Sensitivity

5
Terms of electricity

• Electrical current the flow of energy between
  two points
• Needs
• A driving force (voltage)
• some material which will conduct the electricity
• Amper unit of measurement, the amount of current
  (amp)
• Conductors Materials and tissues which allow
  free flow of energy

6
Fundamentals of Electricity

• Electricity is the force created by an imbalance
  in the number of electrons at two points
• Negative pole an area of high electron
  concentration (Cathode)
• Positive pole and area of low electron
  concentration (Anode)

7
Charge

• An imbalance in energy. The charge of a solution
  has significance when attempting to drive
  medicinal drugs topically via inotophoresis and
  in attempting to artificially fires a denervated
  muscle

8
Charge Factors to understand

• Coulombs Law Like charges repel, unlike charges
  attract
• Like charges repel
• allow the drug to be driven
• Reduce edema/blood

9
Charge Factors

• Membranes rest at a resting potential which is
  an electrical balance of charges. This balance
  must be disrupted to achieve muscle firing
• Muscle depolarization is difficult to achieve
  with physical therapy modalities
• Nerve depolarization occurs very easily with PT
  modalities

10
Terms of electricity

• Insulators materials and tissues which deter the
  passage of energy
• Semiconductors both insulators and conductors.
  These materials will conduct better in one
  direction than the other
• Rate How fast the energy travels. This depends
  on two factors the voltage (the driving force)
  and the resistance.

11
Terms of electricity

• Voltage electromotive force or potential
  difference between the two poles
• Voltage an electromotive force, a driving force.
  Two modality classification are
• Hi Volt greater than 100-150 V
• Lo Volt less than 100-150 V

12
Terms of electricity

• Resistance the opposition to flow of current.
  Factors affecting resistance
• Material composition
• Length (greater length yields greater resistance)
• Temperature (increased temperature, increase
  resistance)

13
Clinical application of Electricity minimizing
the resistance

• Reduce the skin-electrode resistance
• Minimize air-electrode interface
• Keep electrode clean of oils, etc.
• Clean the skill on oils, etc.
• Use the shortest pathway for energy flow
• Use the largest electrode that will selectively
  stimulate the target tissues
• If resistance increases, more voltage will be
  needed to get the same current flow

14
Clinical application of Electricity Temperature

• Relationship
• An increase in temperature increases resistance
  to current flow
• Applicability
• Preheating the tx area may increase the comfort
  of the tx but also increases resistance and need
  for higher output intensities

15
Clinical Application of Electricity Length of
Circuit

• Relationship
• Greater the cross-sectional area of a path the
  less resistance to current flow
• Application
• Nerves having a larger diameter are depolarized
  before nerves having smaller diameters

16
Clinical Application of Electricity Material of
Circuit

• Not all of the bodys tissues conduct electrical
  current the same
• Excitable Tissues
• Nerves
• Muscle fibers
• blood cells
• cell membranes

• Non-excitable tissues
• Bone
• Cartilage
• Tendons
• Ligaments
• Current prefers to travel along excitable tissues

17
Stimulation Parameter

• Amplitude the intensity of the current, the
  magnitude of the charge. The amplitude is
  associated with the depth of penetration.
• The deeper the penetration the more muscle fiber
  recruitment possible
• remember the all or none response and the
  Arndt-Schultz Principle

18
Simulation Parameter

• Pulse duration the length of time the electrical
  flow is on also known as the pulse width. It
  is the time of 1 cycle to take place (will be
  both phases in a biphasic current)
• phase duration important factor in determining
  which tissue stimulated if too short there will
  be no action potential

19
Stimulation Parameter

• Pulse rise time the time to peak intensity of
  the pulse (ramp)
• rapid rising pulses cause nerve depolarization
• Slow rise the nerve accommodates to stimulus and
  a action potential is not elicited
• Good for muscle reeducation with assisted
  contraction - ramping (shock of current is
  reduced)

20
Stimulation Parameters

• Pulse Frequency (PPSHertz) How many pulses
  occur in a unit of time
• Do not assume the lower the frequency the longer
  the pulse duration
• Low Frequency 1K Hz and below (MENS .1-1K Hz),
  muscle stim units)
• Medium frequency 1K ot 100K Hz (Interferential,
  Russian stim LVGS)
• High Frequency above 100K Hz (TENS, HVGS,
  diathermies)

21
Stimulation Parameter

• Current types alternating or Direct Current (AC
  or DC)
• AC indicates that the energy travels in a
  positive and negative direction. The wave form
  which occurs will be replicated on both sides of
  the isoelectric line
• DC indicated that the energy travels only in the
  positive or on in the negative direction

DC
AC
22
Stimulation Parameter

• Waveforms the path of the energy. May be smooth
  (sine) spiked, square,, continuous etc.
• Method to direct current
• Peaked - sharper
• Sign - smoother

23
Stimulation Parameter

• Duty cycles on-off time. May also be called
  inter-pulse interval which is the time between
  pulses. The more rest of off time, the less
  muscle fatigue will occur
• 11 Raito fatigues muscle rapidly
• 15 ratio less fatigue
• 17 no fatigue (passive muscle exercise)

24
Stimulation Parameter

• Average current (also called Root Mean Square)
• the average intensity
• Factors effective the average current
• pulse amplitude
• pulse duration
• waveform (DC has more net charge over time thus
  causing a thermal effect. AC has a zero net
  charge (ZNC). The DC may have long term adverse
  physiological effects)

25
Stimulation Parameter

• Current Density
• The amount of charge per unit area. This is
  usually relative to the size of the electrode.
  Density will be greater with a small electrode,
  but also the small electrode offers more
  resistance.

26
Capacitance

• The ability of tissue (or other material) to
  store electricity. For a given current intensity
  and pulse duration
• The higher the capacitance the longer before a
  response. Body tissues have different
  capacitance. From least to most
• Nerve (will fire first, if healthy)
• Muscle fiber
• Muscle tissue

27
Capacitance

• Increase intensity (with decrease pulse duration)
  is needed to stimulate tissues with a higher
  capacitance.
• Muscle membrane has 10x the capacitance of nerve

28
Factors effecting the clinical application of
electricity

• Factors effecting the clinical application of
  electricity Rise Time the time to peak intensity
• The onset of stimulation must be rapid enough
  that tissue accommodation is prevented
• The lower the capacitance the less the charge can
  be stored
• If a stimulus is applied too slowly, it is
  dispersed

29
Factors effecting the clinical application of
electricity

• An increase in the diameter of a nerve decreased
  its capacitance and it will respond more
  quickly. Thus, large nerves will respond more
  quickly than small nerves.
• Denervated muscles will require a long rise time
  to allow accommodation of sensory nerves. Best
  source for denervated muscle stimulation is
  continuous current DC

30
Factors effecting the clinical application of
electricity

• Ramp A group of waveforms may be ramped (surge
  function) which is an increase of intensity over
  time.
• The rise time is of the specific waveform and is
  intrinsic to the machine.

31
Law of DuBois Reymond

• The amplitude of the individual stimulus must be
  high enough so that depolarization of the
  membrane will occur.
• The rate of change of voltage must be
  sufficiently rapid so that accommodation does not
  occur
• The duration of the individual stimulus must be
  long enough so that the time course of the latent
  period (capacitance), action potential, and
  recovery can take place

32
Muscle Contractions Frequency

• Are described according to the pulse width
• 1 pps twitch
• 10 pps summation
• 25-30 pps tetanus (most fibers will reach
  tetany by 50 pps)
• Frequency selection
• 100Hz - pain relief
• 50-60 Hz muscle contraction
• 1-50 Hz increased circulation
• The higher the frequency (Hz) the more quickly
  the muscle will fatigue

33
Frequency selection

• 100Hz - pain relief
• 50-60 Hz muscle contraction
• 1-50 Hz increased circulation
• The higher the frequency (Hz) the more quickly
  the muscle will fatigue

34
Electrodes used in clinical application of
current

• Electrodes used in clinical application of
  currentAt least two electrodes are required to
  complete the circuit
• The body becomes the conductor
• Monophasic application requires one negative
  electrode and one positive electrode
• The strongest stimulation is where the current
  exists the body
• Electrodes placed close together will give a
  superficial stimulation and be of high density

35
Electrodes used in clinical application of
current

• Electrodes spaced far apart will penetrate more
  deeply with less current density
• Generally the larger the electrode the less
  density. If a large dispersive pad is creating
  muscle contractions there may be areas of high
  current concentration and other areas relatively
  inactive, thus functionally reducing the total
  size of the electrode
• A multitude of placement techniques may be used
  to create the clinical and physiological effects
  you desire

36
General E-Stim Parameters
37
E-Stim for Pain Control typical Settings
38
High Volt Pulsed Stimulation
39
CURRENT CONCEPTSEVIDENCE BASED

• ES increased 20 verses control (no activity)
  demonstrating that ES can alter the blood flow
  in muscle being stimulated Currier et all 1996
• Currier et al 1988 Similar study but 15
• Bettany et al 1990 Edema formation in frogs
  decreased with HVPC 10 minutes after the trauma

40
CURRENT CONCEPTSEVIDENCE BASED

• Walker et al 1988 HVS at a pulse rate of 30 Hz
  and intensities to evoke 10 - 20 MVC did not
  increase blood flow to the popliteal artery. The
  exercise group demonstrated 30 increase
• Von Schroeder et al 1991 Femoral venous flow
  shown to increase greatest with passive SLR
  elevation, then CPM, active ankle dorsiflexion,
  manual calf compression and passive dorsiflexion

41
HVPS

• The application of monophasic current with a
  known polarity
• typically a twin-peaked waveform
• duration of 5 - 260 msec
• Wide variety of uses
• muscle reeducation (requires 150V)
• nerve stimulation (requires 150V)
• edema reduction
• pain control

42
Clinical Application

• Physiological response can be excitatory and
  non-excitatory
• Excitatory
• Peripheral nerve stimulation for pain modulation
  (sensory, motor and pain fibers)
• Promote circulation inhibits sympathetic nervous
  system activity, muscle pumping and endogenous
  vasodilatation

• Non-Excitatory (cellular level)
• Protein synthesis
• Mobilization of blood proteins
• Bacteriocyte affects (by increased CT
  micro-circulation there is a reabsorption of the
  interstitial fluids)

43
General Background

• Early in history HVS was called EGS, then HVGS,
  then HVPS
• Current qualifications to be considered HVS
• Must have twin peak monophasic current
• Must have 100 or 150 volts (up to 500 V)

44
HVPS

• Precautions
• Stimulation may cause unwanted tension on muscle
  fibers
• Muscle fatigue if insufficient duty cycle
• Improper electrodes can burn or irritate
• Intense stim may result in muscle spasm or
  soreness

• Contraindications
• Cardiac disability
• Pacemakers
• Pregnancy
• Menstruation
• Cancerous lesion
• Infection
• Metal implants
• Nerve sensitivity
• Indications
• past slide

45
Treatment Duration

• General - 15-30 minutes repeated as often as
  needed
• Pain reduction - sensory 30 minutes with 30
  minute rest between tx

46
Current Parameters

• greater than 100-150 V
• usually provides up to 500 V
• high peak, low average current
• strength duration curve short pulse duration
  required higher intensity for a response
• high peak intensities (watts) allow a deeper
  penetration with less superficial stimulation

47
Current Parameters

• Pulse Rate
• ranges from 1-120 pps
• varies according to the desire clinical
  application Current
• Pulse Charge
• related to an excess or deficiency of negatively
  charged particles
• associated with the beneficial or harmful
  responses (thermal, chemical, physical)

• Modulations
• intrapulse spacing
• duty cycle reciprocal mode usually 11 ratio
• ramped or surged cycles
• Clinical Considerations
• always reset intensity after use (safety)
• electrode arrangements may be mono or bipolar
• units usually have a hand held probe for local
  (point) stimulation
• most units have an intensity balance control

48
Application Techniques

• Monopolar 2 unequal sized electrodes. Smaller
  is generally over the treatment site and the
  large serves as a dispersive pad, usually located
  proximal to the treatment area
• Bipolar two electrodes of equal size, both are
  over or near the treatment site
• Water immersion - used for irregularly shaped
  areas
• Probes one hand-held active lead
• advantages can locate and treat small triggers
• disadvantages one on one treatment requires full
  attention of the trainer

49
Electrodes

• Material
• carbon impregnated silicone electrodes are
  recommended but will develop hot spots with
  repeated use
• you want conductive durable and flexible material
• tin with overlying sponge has a decreased
  conformity and reduced conductivity

50
Electrodes

• Size
• based on size of target area
• current density is important. The smaller the
  electrode size the greater the density

51
Neuromuscular Stimulation

• Roles
• re-educate a muscle how to contract after
  immobilization (does not produce strength
  augmentation but retards atrophy)

52
Pain Control
Roles Control acute or chronic pain both sensory
(gate control - 100-150 pps)) and motor level
(opiate release - through voltage)
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Pain Control - Opiate Release Setting
54
Evidence Based

• Clinical Studies on HVPC and pain modulation is
  misleading pain associated with muscle spasm is
  decreased secondary to muscle fatigue/exhaustion
  (Belanger, 2003)
• Studies on muscle strengthening have indicated no
  effect (Alon 1985, Mohr et al, 1985 Wong 1986)

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Control and Reduction of Edema
Roles Sensory level used to limit acute
edema Motor-level stimulation used to reduce
subacute or chronic inflammation
56
Motor-Level Edema Reduction
Cell Metabolism increased and may increase blood
flow Wound Healing May increase collagnase
levels and inhibit bacteria in infected wounds
(for this effect 20 min - polarity followed by 40
min polarity recommended)
57
Russian Current

• Continuous sine-wave modulation of 2,5000 pps and
  burst-modulated for fixed periods of 10 msec
  resulting in a frequency of 50 bursts per second.
• Thought to depolarize both sensory and motor
  concomitantly (knots 1977). Thus simulating
  muscle training.
• No North American has been able to duplicate
  Knots claims

58
T.E.N.S.
59
General Concepts

• An Approach to pain control
• Trancutaneous Electrical Nerve Stimulation
• Any stimulation in which a current is applied
  across the skin to stimulate nerves
• 1965 Gate Control Theory created a great
  popularity of TENS
• TENS has 50-80 efficacy rate
• TENS stimulates afferent sensory fibers to elicit
  production of neurohumneral substances such as
  endorphins, enkephalins and serotonin (i.e. gate
  theory)

60
TENS

• Indications
• Control Chronic Pain
• Management post-surgical pain
• Reduction of post-traumatic acute pain

• Precautions
• Can mask underlying pain
• Burns or skin irritation
• prolonged use may result in muscle spasm/soreness
• caffeine intake may reduce effectiveness
• Narcotics decrease effectiveness

Research is variable regarding the benefits of
TENS Therapy (see Table 2-2 Belanger, 2001)
61
TENS may be

• high voltage
• interferential
• acuscope
• low voltage AC stimulator
• classical portable TENS unit

62
Biophysical Effects

• Primary use is to control pain through Gate
  Control Theory
• (between 0-100 can be placebo effect
  (Thorsteinsson et al., 1978, Wall,1994)
• Opiate pain relief through stimulation of
  naloxone (antagonist to endogenous opiates)
• May produce muscle contractions
• Various methods
• High TENS (Activate A-delta fibers)
• Low TENS (release of ??-endorphins from
  pituitary)
• Brief-Intense TENS (noxious stimulation to active
  C fibers)

63
Techniques of TENS application

• Conventional or High Frequency
• Short Duration , high frequency and low to
  comfortable current amplitude
• Only modulation that uses the Gate Control Theory
  (opiate all others)
• Acupuncture or Low Frequency
• Long pulse duration, Low frequency and low to
  comfortable current amplitude
• Brief Intense
• Long pulse duration, high frequency, comfortable
  to tolerable amplitude
• Burst Mode
• Burst not individual pulses, modulated current
  amplitude
• Modulated
• Random electronic modulation of pulse duration,
  frequency and current amplitude

64
Protocol for Various Methods of TENS
65
Conventional Tens/High Frequency TENS

• Paresthesia is created without motor response
• A Beta filers are stimulated to SG enkephlin
  interneuron (pure gate theory)
• Creates the fastest relief of all techniques
• Applied 30 minutes to 24 hours
• relief is short lives (45 sec 1/2 life)
• May stop the pain-spasms cycle

66
Application of High TENS

• Pulse rate high 75-100 Hz (generally 80),
  constant
• Pulse width narrow, less than 300 mSec generally
  60 microSec
• Intensity comfortable to tolerance

67
Set up

• 2 to 4 electrodes, often will be placed on
  post-op. Readjust parameters after response has
  been established. Turn on the intensity to a
  strong stimulation. Increase the pulse width and
  ask if the stimulation is getting wider (if
  deepergood, if stronger...use shorter width)

68
Low Frequency/Acupuncture-like TENS

• Level III pain relief, A delta fibers get Beta
  endorphins
• Longer lasting pain relief but slower to start
• Application
• pulse rate low 1-5ppx (below 10)
• Pulse width 200-300 microSec
• Intensity strong you want rhythmical
  contractions within the patients tolerance

69
Burst Mode TENS

• Carrier frequency is at a certain rate with a
  built in duty cycle
• Similar to low frequency TENS
• Carrier frequency of 70-100 Hz packaged in bursts
  of about 7 bursts per second
• Pulses within burst can vary
• Burst frequency is 1-5 bursts per second
• Strong contraction at lower frequencies
• Combines efficacy of low rate TENS with the
  comfort of conventional TENS

70
Burst Mode TENS - Application

• Pulse width high 100-200 microSec
• Pulse rate 70-100 pps modulated to 1-5 burst/sec
• Intensity strong but comfortable
• treatment length 20-60 minutes

71
Brief, Intense TENS hyper-stimulation analgesia

• Stimulates C fibers for level II pain control
  (PAG etc.)
• Similar to high frequency TENS
• Highest rate (100 Hz), 200 mSec pulse width
  intensity to a very strong but tolerable level
• Treatment time is only 15 minutes, if no relief
  then treat again after 2-3 minutes
• Mono or biphasic current give a bee sting
  sensation
• Utilize motor, trigger or acupuncture points.

72
Brief Intense TENS - Application

• Pulse width as high as possible
• Pulse rate depends on the type of stimulator
• Intensity as high as tolerated
• Duration 15 minutes with conventional TENS unit.
  Locus stimulator is advocated for this treatment
  type, treatment time is 30 seconds per point.

73
Locus point stimulator

• Locus (point) stimulators treatment occurs once
  per day generally 8 points per session
• Auricular points are often utilized
• Treat distal to proximal
• Allow three treatment trails before efficacy is
  determined
• Use first then try other modalities

74
Modulated Stimulation

• Keeps tissues reactive so no accommodation occurs
• Simultaneous modulation of amplitude and pulse
  width
• As amplitude is decreased, pulse width is
  automatically increased to deliver more
  consistent energy per pulse
• Rate can also be modulated

75
Electrode Placement

• May be over the painful sites, dermatomes,
  myotomes, trigger points, acupuncture points or
  spinal nerve roots.
• May be crossed or uncrossed (horizontal or
  vertical

76
Contraindications

• Demand pacemakers
• over carotid sinuses
• Pregnancy
• Cerebral vascular disorders (stroke patients)
• Over the chest if patient has any cardiac
  condition

77
Interferential Current - IFC
78
Interferential Current

• History In 1950 Nemec used interference of
  electrical currents to achieve therapeutic
  benefits. Further research and refinements have
  led to the current IFC available today
• Two AC are generated on separate channels (one
  channel produces a constant high frequency sine
  wave (4000-5000Hz) and the other a variable sine
  wave
• The channels combine/interface to produce a
  frequency of 1-100 Hz (medium frequency)
• Evidence Based Although IFC has been used for 40
  years, only a few clinical studies have been
  published regarding use (DeDomenico, 1981,1987
  Savage, 1984 Nikolova, 1987).

79
Effects of IFC treatment

• Primary Physiological Effect Capacity of IFC to
  depolarize Sensory and motor nerve fibers
• Main Therapeutic Effects
• Sensory nerve fibers - Pain reduction - receive
  a lower amplitude stimulation than the area of
  tissue affected by the vector, thus IFC is said
  to be more comfortable than equal amplitudes
  delivered by conventional means
• Blood flow/edema management
• Muscle fatigue - muscle spasm - is reduced when
  using IFC versus HVS due to the asynchronous
  firing of the motor units being stimulated

80
Positive effects of IFC include

• reduction of pain and muscle discomfort following
  joint or muscle trauma
• these effects can be obtained with the of IFC and
  without associated muscle fatigue which may
  predispose the athlete to further injury.

81
Evidence Based Research

• Low frequency
• This has been claimed as the key to IFC (Savage,
  1984, Nikolova, 1987)
• Palmer, 1999 IFC unlikely to produce
  physiological and therapeutic effects different
  from those achieved by TENS
• Alon, 1999 states that IFC simply provides a more
  expensive, different, least effective and
  somewhat redundant approach to achieving the same
  effects as other electrical stimulation
  parameters/waveforms
• Pain sensation Although the physiological
  changes are not different with IFC, Pain
  perception is decreased with IFC (Palmer, 1999)

82
Evidence Based Literature

• IFC does not lower skin impedance (Alon, 1999
  Gerleman et al, 1999)
• Any pulsed biphasic current, regardless of
  waveform, having a medium frequency are capable
  of a deeper stimulating effect (Alon, 1999
  Hayes, 2000 Kloth, 1991) Snyder-Mackler, et al
  1989)
• Increased Circulation is an anecdotal claim and
  has not been recreated in studies (Bersglien et
  al, 1988 Indergand et al.k 1995 Johnson, 1999
  Nusswbaum et al., 1990 Olson et al., 1999)
• Analgesic Effect Similar not superior to other
  stimulations (TENS) (DeDomenico, 1982, 1987
  Nikolova, 1987 Savage, 1984)
• Stephenson et al., 1995 Superior to a control
  group with ice/pain
• Cramp et al., 2000 Failed to demonstrate any
  effective pain relief with IFC

83
Principles of wave interference - Combined Effects

• Constructive, Destructive, Continuous
• Constructive interference when two sinusoidal
  waves that are exactly in phase or one, two,
  three or more wavelengths our of phase, the waves
  supplement each other in constructive interference

84
Principles of wave interference - Combined Effects

• Destructive interference when the two waves are
  different by 1/2 a wavelength (of any multiple)
  the result is cancellation of both waves

85
Principles of wave interference - Combined Effects

• Continuous Interference
• Two waves slightly out of phase collide and form
  a single wave with progressively increasing and
  decreasing amplitude

86
Amplitude-Modulated Beats

• Rate at which the resultant waveform (from
  continuous interference) changes
• When sine waves from two similar sources have
  different frequencies are out of phase and blend
  (heterodyne) to produce the interference beating
  effect

87
IFC

• Duration of tx 15-20 minutes
• Burst mode typically applied 3x a week in 30
  minute bouts
• Precautions
• same as all electrical currents

• Contraindications
• Pain of central origin
• Pain of unknown origin
• Indications
• Acute pain
• Chronic pain
• Muscle spasm

88
IFC Techniques of treatment

• Almost exclusively IFC is delivered using the
  four-pad or quad-polar technique.
• Various electrode positioning techniques are
  employed
• Electrodes (Nemectrody vacuum electrodes)
• four independent pads allow specific placement of
  pads to achieve desired effect an understanding
  of the current interference is essential
• four electrodes in one applicator allows IFC
  treatment to very small surface areas. The field
  vector is pre-determined by the equipment

89
Quad-polar Technique

• Pads placed at 45º angles from center of tx area
• Can reduce inaccuracy of appropriate tissues by
  selecting rotation or scan

Channel B
Channel B
Channel A
SCAN
Channel A
90
Bipolar Electrode Placement

• The mix of two channels occurs in generator
  instead of tissues
• Biopolar does not penetrate tissues as deeply,
  but is more accurate
• When effects are targeted for one muscle or
  muscle group only one channel is used

91
Two-circuit IFC

• At other points along the time axes the wave
  amplitude will be zero because the positive phase
  from one circuit cancels the negative phase from
  the second circuit (destructive interference)
• The rhythmical rise and fall of the amplitude
  results in a beat frequency and is equal to the
  number of times each second that the current
  amplitude increases to its maximum value and then
  decreases to its minimum value

92
Special Modulations of IFC

• Constant beat frequencies (model) the difference
  between the frequencies of the two circuits is
  constant and the result is a constant beat
  frequency. That is, if the difference in
  frequency between the two circuits is 40 pps, the
  beat frequency will be constant at 40 bps.

93
Special Modulations of IFC

• Variable beat mode the frequency between the two
  circuits varies within preselected ranges. The
  time taken to vary the beat frequency through any
  programmed range is usually fixed by the device
  at about 15 sec. IFC machines often allow the
  clinician to choose from a variety of beat
  frequency programs.

94
Pain Control

• Similar to TENS - beat frequency 100Hz
• Low beat frequencies when combined with motor
  level intensities (2-10Hz) initiate the release
  of opiates
• 30 Hz frequencies affects the widest range of
  receptors

95
Neuromuscular Stimulation

• Beat frequency of approximately 15 HZ is used to
  reduce edema
• General Parameters

96
IFC Technique of treatment

• Electrode placement
• The resultant vector should be visualized in
  placing the electrodes for a treatment . The
  target tissue should be identified and the vector
  positioned to hit that area. Typically at 45º
  angles is most effective.
• Segregation of the pin tips is essential in the
  proper electrode positioning for IFC. The
  electrodes may be of the same size or two
  different sizes (causing a shift in the
  intersecting vector). Treatment through a joint
  has also been advocated without adequate research
  to establish efficacy of the treatment technique.

97
Bone Stimulating Current

• Bone Stimulating CurrentBone Stimulating
  CurrentIFC has been used (Laabs et al) studied
  the healing of a surgically induced fracture in
  the forelegs of sheep. Their study indicated an
  acceleration of healing in the sheep treated with
  IFC as compared to the control group

98
Bone Stimulating Current

• This study validated an earlier study by Gittler
  and Kleditzsch which showed similar results in
  callus formation in rabbits. Several other
  studies have shown an increase in the healing
  rate of fractures but the exact mechanism by
  which the healing occurs is not understood.

99
Bone Stimulating Current

• Some speculation is that an increased blood flow
  to the injured area is produced which allowed
  natural healing processes to occur more rapidly.
• In one study (mandible fractures ) the IFC caused
  very mild muscle contraction of the jaw and this
  muscle activity was thought to have been a
  potential accelerator of the healing.

100
MENS or LIDC (low-intensity direct current)
101
MENS

• No universally accepted definition or protocol
  has yet to be substantiated
• This form of modality is at the sub-sensory or
  very low sensory level
• current less than 1000?A (approx 1/1000 amp of
  TENS)
• Theorized that this is the current of injury
  (Becker et al 1967, Becker Seldon, 1987)

102
Biophysical Effects

• Theory
• Currents below 500?A increases the level of ATP
  (high Amp decreases ATP levels)
• Increase in ATP encourages amino acid transport
  and increased protein synthesis
• MENS reestablishes the bodys natural electrical
  balance allowing metabolic energy for healing
  without shocking the system (other types of
  e-stim)
• Studies conducted indicate no difference from
  control group for wound healing

103
MENS

• Duration
• 30 min to 2 hours up to 4x a day
• Research suggests high degree of variability on
  tx protocols
• Precautions
• Dehydrated patients
• on Scar tissue (too much impedance)
• Contraindications
• Pain of unknown origin
• Osteomyelitis
• Inconclusive Data
• DOMS as an indication (Allen et al 1999, Weber et
  al 1994)

• Indications
• Acute Chronic Pain
• Acute Chronic Inflammation
• Edema reduction
• sprains Strains
• Contusion
• TMJ dysfunction
• Neuropathies
• Superficial wound healing
• Carpal Tunnel Syndrome

104
Electrode Placement

• Electrodes should be placed in a like that
  transects the target tissues
• Remember that electrical current travels in path
  of least resistance, thus it is not always a
  straight line.
• Either the or electrode can be placed on the
  injured tissue (Research is inconclusive Lampe
  1998, Sussmen et al 1999)
• Suggest alternating and - electrode

TARGET
105
Application Techniques

• Standard electrical stimulation pads
• generator may have bells Whistles since MENS is
  sub-sensory
• Probe

106
Bone Stimulating Current

• MENS
• Has been advocated in the healing of bone, using
  implanted electrodes and delivering a DC current
  with the negative pole at the fracture site.
  Further use of MENS has allowed increased rate
  of fracture healing using surface electrodes in a
  non-invasive technique. Theories on the
  physiology behind the healing focus on the
  electrical charge present in the normal tissue as
  compared to the electrical charge found with the
  injured tissue. MENS is said to allow an
  induction of an electrical charge to return to he
  tissues to a better healing environment
• Research on bone stimulating current is
  inconclusive.

107
Iontophoresis
108
Iontophoresis

• Categorized as continuous direct electric current
• The transfer of ions across the skin
  (transdermal)by use of continuous direct current
• Iontophoresis is based on the principle that an
  electrically charged electrode will repel a
  similarly charged ion (first reported by LeDuc in
  1903).
• This is pore dependant (Banga et al 1998)
• Delivers a low-volt High-amp DC current
• Local blood flow is increased for 1 hour post tx

109
Iontophoresis

• Duration of Tx
• Based on intensity desired usually every other
  day for 3 weeks
• Indications
• Acute or Chronic Inflam
• Arthritis
• Myositis
• Myofacial Pain Syndromes
• Invasive method for delivering drugs

• Contraindications
• Hypersensitivity to electrical currents
• Contraindications to meds.
• Pain of unknown origin
• Precautions
• Prescription
• Dosage
• Do not reuse electrode
• Burns if intensity to great

110
Iontophoresis

• Effects of treatment depends on the ion(s)
  delivered
• musculoskeletal inflammatory conditions
  (tendonitis, bursitis) have been successfully
  treated
• Using desamethosone sodium phosphate (decadron)
  and Xylocaine
• Reduction of edema has been achieved by driving
  hyaluronidase
• Transitory (5min) local anesthesia has been
  produced by delivering lidocaine to the tissues.
  The anesthesia was better than that achieved by
  topical application but less effective than
  infiltration of the area with lidocaine.

111
Medication Dosage

• Medication dose delivered during tx is measured
  in mA based on relationship of amperage, tx
  duration
• Current Amp (mA) x Tx Duration - mA/min
• Iontophoresors are dose-oriented - where user
  indicated desired tx does and generator
  calculated duration and intensity

112
Indications evidence based
Condition Ions Benefit Reference
Plantar Faciitis Dex/lido. Yes Kahn, 1982, Reidle et all 2000, Montorsi et all 2000, Rothfield et al 1967
Inflamm. Disorders Musc. Dex Yes Bertolucci, 1982, Delacerda, 1982Harris, 1982, Pellecchia et al 1994,
TMJ Dex dex/lido Yes Braun 1987 Reid et al 1994Schiffman et al 1996
TMJ Hydrocort/US No Kahn, 1980
Epicondylitis Dex No Panus et al 1996
Epicondylitis Na Salcycil. Yes Demiratas et al 1998
Carpal tunnel Dex Yes Banta, 1994
Edema Hualuronidase Yes Magistro 1964, Boone 1969
113
Iontophoresis Evidence Based
Condition Ions Benefit Reference
Scar Tissue Iodine Yes Tennenbaum, 1980
Tendon Adhesion Iodine Yes Langley 1984
Subdeltoid Bursa Magnesium Yes Weinstein et al 1958
Plantar warts Salicylate Yes Gordon et al 1969
Heel Pain Acetate Yes Japour et al, 1999
Myositis Oss. Acetate Yes Weider, 1992
Myopathy Calcium ? Kahn, 1975
Postsurgical hip pain Salicylate Yes Garzione, 1978
114
Biophysical Effects

• Dependant on Medication
• See following chart

115
Sample Medications
116
Electrode Placement

• Delivery Electrode (drug electrode)
• placed over target tissue
• Active electrode (dispersive electrode)
• place 4-6 inches from drug electrode

117
Side Effects Tissue burning

• An alkaline reaction occurs under the cathode
  (negative electrode) which is much more caustic
  to the skin than the acidic reaction occurring at
  the anode. The cathode may be increased in size
  to attempt to decrease this caustic reaction

118
Side Effects Tissue burning

• Continuous unidirectional current (as needed for
  iontophoresis) tends to cause tissue irritation
  because skin will not tolerate current density
  greater than 1mA/sq.cm. Thin tissue areas, areas
  of skin abrasion and areas of scarring are
  certain areas to avoid. This potential for burn
  is exacerbated by the fact that there is an
  anesthetic effect of DC under the electrode.
  Thus tissue irritation may develop without the
  patients realization
• Dont need to drive every day 1-2x a week