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 painEdema reductionMuscle spasm reductionReducing joint contracturesMinimizing disuse/ atrophyFacilitating tissue healingStrengthening muscleFacilitating fracture healing
4 Contraindications of Electrotherapy Cardiac disabilityPacemakersPregnancyMenstruation (over abdomen, lumbar or pelvic region)Cancerous lesionsSite of infectionExposed metal implantsNerve Sensitivity
5 Terms of electricityElectrical current: the flow of energy between two pointsNeedsA driving force (voltage)some material which will conduct the electricityAmper: 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 pointsNegative pole an area of high electron concentration (Cathode)Positive pole and area of low electron concentration (Anode)
7 ChargeAn 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 Coulomb’s Law: Like charges repel, unlike charges attractLike charges repelallow the drug to be “driven”Reduce edema/blood
9 Charge: FactorsMembranes rest at a “resting potential” which is an electrical balance of charges. This balance must be disrupted to achieve muscle firingMuscle depolarization is difficult to achieve with physical therapy modalitiesNerve depolarization occurs very easily with PT modalities
10 Terms of electricityInsulators: materials and tissues which deter the passage of energySemiconductors: both insulators and conductors. These materials will conduct better in one direction than the otherRate: How fast the energy travels. This depends on two factors: the voltage (the driving force) and the resistance.
11 Terms of electricityVoltage: electromotive force or potential difference between the two polesVoltage: an electromotive force, a driving force. Two modality classification are:Hi Volt: greater than VLo Volt: less than V
12 Terms of electricityResistance: the opposition to flow of current. Factors affecting resistance:Material compositionLength (greater length yields greater resistance)Temperature (increased temperature, increase resistance)
13 Clinical application of Electricity: minimizing the resistance Reduce the skin-electrode resistanceMinimize air-electrode interfaceKeep electrode clean of oils, etc.Clean the skill on oils, etc.Use the shortest pathway for energy flowUse the largest electrode that will selectively stimulate the target tissuesIf resistance increases, more voltage will be needed to get the same current flow
14 Clinical application of Electricity: Temperature RelationshipAn increase in temperature increases resistance to current flowApplicabilityPreheating 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 flowApplication:Nerves having a larger diameter are depolarized before nerves having smaller diameters
16 Clinical Application of Electricity: Material of Circuit Not all of the body’s tissues conduct electrical current the sameExcitable TissuesNervesMuscle fibersblood cellscell membranesNon-excitable tissuesBoneCartilageTendonsLigamentsCurrent 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 possibleremember the all or none response and the Arndt-Schultz Principle
18 Simulation ParameterPulse 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 depolarizationSlow rise: the nerve accommodates to stimulus and a action potential is not elicitedGood for muscle reeducation with assisted contraction - ramping (shock of current is reduced)
20 Stimulation Parameters Pulse Frequency: (PPS=Hertz) How many pulses occur in a unit of timeDo not assume the lower the frequency the longer the pulse durationLow 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 lineDC indicated that the energy travels only in the positive or on in the negative directionDCAC
22 Stimulation Parameter: Waveforms; the path of the energy. May be smooth (sine) spiked, square,, continuous etc.Method to direct currentPeaked - sharperSign - 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 occur1:1 Raito fatigues muscle rapidly1:5 ratio less fatigue1:7 no fatigue (passive muscle exercise)
24 Stimulation Parameter: Average current (also called Root Mean Square)the “average” intensityFactors effective the average current:pulse amplitudepulse durationwaveform (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 DensityThe 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 durationThe higher the capacitance the longer before a response. Body tissues have different capacitance. From least to most:Nerve (will fire first, if healthy)Muscle fiberMuscle 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 intensityThe onset of stimulation must be rapid enough that tissue accommodation is preventedThe lower the capacitance the less the charge can be storedIf 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 it’s 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 occurThe 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 Are described according to the pulse width 1 pps = twitch10 pps = summation25-30 pps = tetanus (most fibers will reach tetany by 50 pps)
33 Frequency selection: 100Hz - pain relief 50-60 Hz = muscle contraction 1-50 Hz = increased circulationThe 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 current:At least two electrodes are required to complete the circuitThe body becomes the conductorMonophasic application requires one negative electrode and one positive electrodeThe strongest stimulation is where the current exists the bodyElectrodes 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 densityGenerally 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 electrodeA multitude of placement techniques may be used to create the clinical and physiological effects you desire
39 HVPS The application of monophasic current with a known polarity typically a twin-peaked waveformduration of msecWide variety of uses:muscle reeducation (requires 150V)nerve stimulation (requires 150V)edema reductionpain control
40 Clinical Application: Physiological response can be excitatory and non-excitatoryExcitatoryPeripheral nerve stimulation for pain modulation (sensory, motor and pain fibers)Promote circulation: inhibits sympathetic nervous system activity, muscle pumping and endogenous vasodilatationNon-Excitatory (cellular level)Protein synthesisMobilization of blood proteinsBacteriocyte affects (by increased CT micro-circulation there is a reabsorption of the interstitial fluids)
41 General BackgroundEarly in history HVS was called EGS, then HVGS, then HVPSCurrent qualifications to be considered HVSMust have twin peak monophasic currentMust have 100 or 150 volts (up to 500 V)
42 HVPS Precautions Contraindications Stimulation may cause unwanted tension on muscle fibersMuscle fatigue if insufficient duty cycleImproper electrodes can burn or irritateIntense stim may result in muscle spasm or sorenessContraindicationsCardiac disabilityPacemakersPregnancyMenstruationCancerous lesionInfectionMetal implantsNerve sensitivityIndicationspast slide
43 Treatment Duration General - 15-30 minutes repeated as often as needed Pain reduction - sensory 30 minutes with 30 minute rest between tx
44 Current Parameters greater than 100-150 V usually provides up to 500 V high peak, low average currentstrength duration curve = short pulse duration required higher intensity for a responsehigh peak intensities (watts) allow a deeper penetration with less superficial stimulation
45 Current Parameters Pulse Rate: Modulations Pulse Charge ranges from ppsvaries according to the desire clinical application CurrentPulse Chargerelated to an excess or deficiency of negatively charged particlesassociated with the beneficial or harmful responses (thermal, chemical, physical)Modulationsintrapulse spacingduty cycle: reciprocal mode usually 1:1 ratioramped or surged cyclesClinical Considerations:always reset intensity after use (safety)electrode arrangements may be mono or bipolarunits usually have a hand held probe for local (point) stimulationmost units have an intensity balance control
46 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 areaBipolar: two electrodes of equal size, both are over or near the treatment siteWater immersion - used for irregularly shaped areasProbes: one hand-held active leadadvantages: can locate and treat small triggersdisadvantages: one on one treatment requires full attention of the trainer
47 ElectrodesMaterialcarbon impregnated silicone electrodes are recommended but will develop hot spots with repeated useyou want conductive durable and flexible materialtin with overlying sponge has a decreased conformity and reduced conductivity
48 Electrodes Size based on size of target area current density is important. The smaller the electrode size the greater the density
49 Neuromuscular Stimulation Roles:re-educate a muscle how to contract after immobilization (does not produce strength augmentation but retards atrophy)
50 Pain ControlRoles:Control acute or chronic pain both sensory (gate control pps)) and motor level (opiate release - through voltage)
52 Control and Reduction of Edema Roles:Sensory level used to limit acute edemaMotor-level stimulation used to recude subacute or chronic inflammation
53 Motor-Level Edema Reduction Cell Metabolism: increased and may increase blood flowWound Healing: May increase collagnase levels and inhibit bacteria in infected wounds (for this effect 20 min - polarity followed by 40 min + polarity recommended)
55 General Concepts: An Approach to pain control Trancutaneous Electrical Nerve Stimulation:Any stimulation in which a current is applied across the skin to stimulate nerves1965 Gate Control Theory created a great popularity of TENSTENS has 50-80% efficacy rateTENS stimulates afferent sensory fibers to elicit production of neurohumneral substances such as endorphins, enkephalins and serotonin (i.e. gate theory)
56 TENS Indications Precautions Control Chronic Pain Management post-surgical painReduction of post-traumatic & acute painPrecautionsCan mask underlying painBurns or skin irritationprolonged use may result in muscle spasm/sorenesscaffeine intake may reduce effectivenessNarcotics decrease effectiveness
57 TENS may be: high voltage interferential acuscope low voltage AC stimulatorclassical portable TENS unit
58 Biophysical EffectsPrimary use is to control pain through Gate Control TheoryMay produce muscle contractionsVarious methodsHigh TENS (Activate A-delta fibers)Low TENS (release of -endorphins from pituitary)Brief-Intense TENS (noxious stimulation to active C fibers)
59 Techniques of TENS application: Conventional or High FrequencyAcupuncture or Low FrequencyBrief IntenseBurst ModeModulated
61 Conventional Tens/High Frequency TENS Paresthesia is created without motor responseA Beta filers are stimulated to SG enkephlin interneuron (pure gate theory)Creates the fastest relief of all techniquesApplied 30 minutes to 24 hoursrelief is short lives (45 sec 1/2 life)May stop the pain-spasms cycle
62 Application of High TENS Pulse rate: high Hz (generally 80), constantPulse width: narrow, less than 300 mSec generally 60 microSecIntensity: comfortable to tolerance
63 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 deeper=good, if stronger...use shorter width)
64 Low Frequency/Acupuncture-like TENS: Level III pain relief, A delta fibers get Beta endorphinsLonger lasting pain relief but slower to startApplicationpulse rate low 1-5ppx (below 10)Pulse width: microSecIntensity: strong you want rhythmical contractions within the patient’s tolerance
65 Burst Mode TENSCarrier frequency is at a certain rate with a built in duty cycleSimilar to low frequency TENSCarrier frequency of Hz packaged in bursts of about 7 bursts per secondPulses within burst can varyBurst frequency is 1-5 bursts per secondStrong contraction at lower frequenciesCombines efficacy of low rate TENS with the comfort of conventional TENS
66 Burst Mode TENS - Application Pulse width: high microSecPulse rate: pps modulated to 1-5 burst/secIntensity: strong but comfortabletreatment length: minutes
67 Brief, Intense TENS: hyper-stimulation analgesia Stimulates C fibers for level II pain control (PAG etc.)Similar to high frequency TENSHighest rate (100 Hz), 200 mSec pulse width intensity to a very strong but tolerable levelTreatment time is only 15 minutes, if no relief then treat again after 2-3 minutesMono or biphasic current give a “bee sting” sensationUtilize motor, trigger or acupuncture points.
68 Brief Intense TENS - Application Pulse width: as high as possiblePulse rate: depends on the type of stimulatorIntensity: as high as toleratedDuration: 15 minutes with conventional TENS unit. Locus stimulator is advocated for this treatment type, treatment time is 30 seconds per point.
69 Locus point stimulator Locus (point) stimulators treatment occurs once per day generally 8 points per sessionAuricular points are often utilizedTreat distal to proximalAllow three treatment trails before efficacy is determinedUse first then try other modalities
70 Modulated Stimulation: Keeps tissues reactive so no accommodation occursSimultaneous modulation of amplitude and pulse widthAs amplitude is decreased, pulse width is automatically increased to deliver more consistent energy per pulseRate can also be modulated
71 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
72 Contraindications: Demand pacemakers over carotid sinuses Pregnancy Cerebral vascular disorders (stroke patients)Over the chest if patient has any cardiac condition
74 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 todayTwo AC are generated on separate channels (one channel produces a constant high frequency sine wave ( Hz) and the other a variable sine waveThe channels combine/interface to produce a frequency of Hz (medium frequency)
75 Effects of IFC treatment: 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 meansMuscle fatigue - muscle spasm - is reduced when using IFC versus HVS due to the asynchronous firing of the motor units being stimulated
76 Positive effects of IFC include: reduction of pain and muscle discomfort following joint or muscle traumathese effects can be obtained with the of IFC and without associated muscle fatigue which may predispose the athlete to further injury.
77 Principles of wave interference - Combined Effects Constructive, Destructive, & ContinuousConstructive 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=+
78 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=+
79 Principles of wave interference - Combined Effects Continuous InterferenceTwo waves slightly out of phase collide and form a single wave with progressively increasing and decreasing amplitude=+
80 Amplitude-Modulated Beats: Rate at which the resultant waveform (from continuous interference) changesWhen sine waves from two similar sources have different frequencies are out of phase and blend (heterodyne) to produce the interference beating effect
81 IFC Duration of tx 15-20 minutes Precautions Contraindications Burst mode typically applied 3x a week in 30 minute boutsPrecautionssame as all electrical currentsContraindicationsPain of central originPain of unknown originIndicationsAcute painChronic painMuscle spasm
82 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 essentialfour electrodes in one applicator allows IFC treatment to very small surface areas. The field vector is pre-determined by the equipment
83 Quad-polar Technique Pads placed at 45º angles from center of tx area Can reduce inaccuracy of appropriate tissues by selecting rotation or scanChannel BChannel BChannel ASCANChannel A
84 Bipolar Electrode Placement The mix of two channels occurs in generator instead of tissuesBiopolar does not penetrate tissues as deeply, but is more accurateWhen effects are targeted for one muscle or muscle group only one channel is used
85 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
86 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.
87 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.
88 Pain Control Similar to TENS - beat frequency 100Hz Low beat frequencies when combined with motor level intensities (2-10Hz) initiate the release of opiates30 Hz frequencies affects the widest range of receptors
89 Neuromuscular Stimulation Beat frequency of approximately 15 HZ is used to reduce edemaGeneral Parameters
90 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.
91 Bone Stimulating Current: Bone Stimulating Current:Bone Stimulating Current:IFC 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
92 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.
93 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.
95 MENSNo universally accepted definition or protocol & has yet to be substantiatedThis form of modality is at the sub-sensory or very low sensory levelcurrent less than 1000A (approx 1/1000 amp of TENS)
96 Biophysical Effects Theory: Currents below 500A increases the level of ATP (high Amp decreases ATP levels)Increase in ATP encourages amino acid transport and increased protein synthesisMENS reestablishes the body’s natural electrical balance allowing metabolic energy for healing without shocking the system (other types of e-stim)
97 MENS Duration Precautions Contraindications Indications 30 min to 2 hours up to 4x a dayPrecautionsDehydrated patientson Scar tissue (too much impedance)ContraindicationsPain of unknown originOsteomyelitisIndicationsAcute & Chronic PainAcute & Chronic InflammationEdema reductionsprains & StrainsContusionTMJ dysfunctionNeuropathiesSuperficial wound healingCarpal Tunnel Syndrome
98 Electrode PlacementElectrodes should be placed in a like that transects the target tissuesRemember that electrical current travels in path of least resistance, thus it is not always a straight line.TARGET
99 Application Techniques Standard electrical stimulation padsgenerator may have bells & Whistles since MENS is subsensoryProbe
100 Bone Stimulating Current: MENSHas 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
102 Iontophoresis:The transfer of ions across the skin (transdermal)by use of continuous direct currentIontophoresis is based on the principle that an electrically charged electrode will repel a similarly charged ion (first reported by LeDuc in 1903).Delivers a low-volt High-amp DC currentLocal blood flow is increased for 1 hour post tx
103 Iontophoresis Duration of Tx: Indications Contraindications Based on intensity desired usually every other day for 3 weeksIndicationsAcute or Chronic InflamArthritisMyositisMyofacial Pain SyndromesInvasive method for delivering drugsContraindicationsHypersensitivity to electrical currentsContraindications to meds.Pain of unknown originPrecautionsPrescriptionDosageDo not reuse electrodeBurns if intensity to great
104 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 XylocaineReduction of edema has been achieved by driving hyaluronidaseTransitory (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.
105 Current Amp (mA) x Tx Duration - mA/min Medication DosageMedication dose delivered during tx is measured in mA based on relationship of amperage, tx durationCurrent Amp (mA) x Tx Duration - mA/minIontophoresors are dose-oriented - where user indicated desired tx does and generator calculated duration and intensity
106 Biophysical EffectsDependant on MedicationSee following chart
108 Electrode Placement Delivery Electrode (drug electrode) placed over target tissueActive electrode (dispersive electrode)place 4-6 inches from drug electrode
109 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
110 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 patient’s realizationDon’t need to drive every day 1-2x a week