© 2005 – fa davis electrical stimulation techniques

© 2005 – FA Davis© 2005 – FA Davis

Electrical Stimulation Electrical Stimulation TechniquesTechniques

Current FlowCurrent Flow Electron FlowElectron Flow

(shown in red)(shown in red)

– Between the generators Between the generators and electrodesand electrodes

– To and from the generatorTo and from the generator Ion FlowIon Flow

(shown in yellow)(shown in yellow)

– Occurs within the tissuesOccurs within the tissues– Negative ions flow towards Negative ions flow towards

the anode and away from the anode and away from the cathodethe cathode

– Positive ions flow towards Positive ions flow towards the cathode and away the cathode and away from the anodefrom the anode

+

+

-

-

ElectrodesElectrodes

PurposePurpose– Completes the circuit between the generator Completes the circuit between the generator

and bodyand body– Interface between electron and ion flowInterface between electron and ion flow– Primary site of resistance to currentPrimary site of resistance to current

MaterialsMaterials– Metallic (uses sponges)Metallic (uses sponges)– SilverSilver– Carbon rubberCarbon rubber– Self-adhesiveSelf-adhesive

Electrode SizeElectrode Size

Determines the Current DensityDetermines the Current Density Equal sizeEqual size

– Bipolar arrangementBipolar arrangement– Approximately equal effects under Approximately equal effects under

exach exach

Electrode ArrangementsElectrode Arrangements

Based on:Based on:Current DensityCurrent DensityProximity to Each OtherProximity to Each OtherAnatomic Location (Stimulation Anatomic Location (Stimulation Points)Points)

Current DensityCurrent Density Bipolar TechniqueBipolar Technique

– Equal current densitiesEqual current densities– Equal effects under each electrodeEqual effects under each electrode

(all other factors being equal)(all other factors being equal)

Monopolar TechniqueMonopolar Technique– Unequal current densitiesUnequal current densities

At least 4:1 differenceAt least 4:1 difference– Effects are concentrated under the smaller Effects are concentrated under the smaller

electrodeelectrode ““Active” electrode(s)Active” electrode(s)

– No effects under larger electrodeNo effects under larger electrode ““Dispersive” electrodeDispersive” electrode

Quadripolar TechniqueQuadripolar Technique– Two bipolar electrode arrangementsTwo bipolar electrode arrangements– Two independent electrical channelsTwo independent electrical channels– TENS is a common exampleTENS is a common example

“Active” “Dispersive”

Electrode ProximityElectrode Proximity Determines the Determines the

number of parallel number of parallel pathspaths

The farther apart the The farther apart the electrodes the more electrodes the more parallel paths are parallel paths are formedformed

More current is More current is required to produce required to produce effects as the effects as the number of paths number of paths increasesincreases

Stimulation PointsStimulation Points Motor PointsMotor Points

– Superficial location of motor nerveSuperficial location of motor nerve– Predictably located Predictably located – Motor nerve chartsMotor nerve charts

Trigger PointsTrigger Points– Localized, hypersensitive muscle spasmLocalized, hypersensitive muscle spasm– Trigger referred painTrigger referred pain– Arise secondary to pathologyArise secondary to pathology

Acupuncture PointsAcupuncture Points– Areas of skin having decreased electrical resistanceAreas of skin having decreased electrical resistance– May result in pain reductionMay result in pain reduction

Traumatized AreasTraumatized Areas– Decreased electrical resistance (increased current flow)Decreased electrical resistance (increased current flow)

Path of Least ResistancePath of Least Resistance Ion flow will follow the path Ion flow will follow the path

of least resistanceof least resistance– NervesNerves– Blood vesselsBlood vessels

The current usually does The current usually does not flow from electrode-to-not flow from electrode-to-electrode (the shortest electrode (the shortest path)path)

The path of least resistance The path of least resistance is not necessarily the is not necessarily the shortest pathshortest path

Selective Stimulation of Selective Stimulation of Nerves Nerves

Nerves always depolarize in the same Nerves always depolarize in the same orderorder– Sensory nervesSensory nerves– Motor nervesMotor nerves– Pain nervesPain nerves– Muscle fiberMuscle fiber

Based on the cross-sectional diameterBased on the cross-sectional diameter– Large-diameter nerves depolarize firstLarge-diameter nerves depolarize first

Location of the nerveLocation of the nerve– Superficial nerves depolarize firstSuperficial nerves depolarize first

Phase Duration and Phase Duration and Nerve Depolarization Nerve Depolarization

Phase duration selectively Phase duration selectively depolarizes tissuesdepolarizes tissues

Phase DurationPhase Duration TissueTissue

ShortShort Sensory nervesSensory nerves

MediumMedium Motor nervesMotor nerves

LongLong Pain nervesPain nerves

DCDC Muscle fiberMuscle fiber

Adaptations Adaptations Patients “get used” to the treatmentPatients “get used” to the treatment More intense output needed More intense output needed HabituationHabituation

– Central nervous systemCentral nervous system– Brain filters out nonmeaningful, repetitive informationBrain filters out nonmeaningful, repetitive information

AccommodationAccommodation– Peripheral nervous systemPeripheral nervous system– Depolarization threshold increasesDepolarization threshold increases

Preventing AdaptationPreventing Adaptation– Vary output (output modulation) to preventVary output (output modulation) to prevent– The longer the current is flowing, the more the current The longer the current is flowing, the more the current

must be modulated.must be modulated.


Electrical Stimulation Electrical Stimulation GoalsGoals

Muscle ContractionsMuscle Contractions[Instructor Note: More detail on [Instructor Note: More detail on

these techniques are found in the these techniques are found in the CH 13 ppt: Treatment Strategies]CH 13 ppt: Treatment Strategies]

Motor-level StimulationMotor-level StimulationComparison of Voluntary and Electrically-Induced Comparison of Voluntary and Electrically-Induced

Contractions Contractions

VoluntaryVoluntary Type I fibers Type I fibers

recruited firstrecruited first AsynchronousAsynchronous

– Decreases fatigueDecreases fatigue GTO protect GTO protect

musclesmuscles

Electrically-inducedElectrically-induced Type II fibers Type II fibers

recruited firstrecruited first Synchronous Synchronous

recruitment recruitment – Based on PPSBased on PPS

GTOs do not limit GTOs do not limit contractioncontraction

Motor-level StimulationMotor-level Stimulation Parameters:Parameters:

AmplitudeAmplitude: Contraction strength increases : Contraction strength increases as amplitude increasesas amplitude increasesPhase durationPhase duration: 300 to 500 µsec targets : 300 to 500 µsec targets motor nerves:motor nerves:– The shorter the phase duration, the more The shorter the phase duration, the more

amplitude requiredamplitude required– Longer durations will also depolarize pain nervesLonger durations will also depolarize pain nerves– Pain often limits quality and quantity of the Pain often limits quality and quantity of the

contractioncontractionPulse frequencyPulse frequency: Determines the type of : Determines the type of contraction contraction

Pulse FrequencyPulse Frequency

Frequency determines the time for Frequency determines the time for mechanical adaptationmechanical adaptation

Lower pps allows more time (longer Lower pps allows more time (longer interpulse interverals)interpulse interverals)LabelLabel RangeRange ResultResult

Low Low < 15 pps* < 15 pps* TwitchTwitch: Individual contractions: Individual contractions

MediumMedium 15-40 pps* 15-40 pps* SummationSummation: Contractions blend: Contractions blend

High High >40 pps* >40 pps* TonicTonic: Constant contraction: Constant contraction

* Approximate values. The actual range varies from person-* Approximate values. The actual range varies from person-

to-person and between muscle groupsto-person and between muscle groups

Effect of Pulse Frequency on Effect of Pulse Frequency on Muscle ContractionsMuscle Contractions

1 pulse per second

Twitch Contraction

The amount of time between pulses – the interpulse interval – is long enough to allow the muscle fibers to return to their original position

20 pulses per second

Summation

The amount of time between pulses allows some elongation of the fibers, but not to their starting point.

40 pulses per second

Tonic Contraction

The current is flowing so rapidly that there is not sufficient time to allow the fibers to elongate



Pain ControlPain Control

Pain ControlPain Control

Sensory-levelSensory-level Motor-LevelMotor-Level Noxious Noxious LevelLevel

TargetTarget A-beta fibersA-beta fibers Motor nervesMotor nerves A-deltaA-delta

TissueTissue C fibersC fibers

PhasePhase < 60 < 60 µsecµsec 120 to 250 µsec120 to 250 µsec 1 msec1 msec

DurationDuration

PulsePulse 60 to 100 pps60 to 100 pps 2 to 4 pps2 to 4 pps VariableVariable

FrequencyFrequency 80 to 120 pps80 to 120 pps

IntensityIntensity SubmotorSubmotor Moderate toModerate to To tolerance To tolerance

Strong contractionStrong contraction



Edema Control and ReductionEdema Control and Reduction

Edema ControlEdema Control

Cathode placed over Cathode placed over injured tissuesinjured tissues

High pulse High pulse frequencyfrequency

Submotor intensitySubmotor intensity Thought to decrease Thought to decrease

capillary capillary permeabilitypermeability

Do not use if edema Do not use if edema has already formedhas already formed

Edema ReductionEdema Reduction

Muscle contractions Muscle contractions “milk” edema from “milk” edema from extremityextremity

Electrodes follow Electrodes follow the vein’s paththe vein’s path

Alternating rate Alternating rate targets muscle targets muscle groupsgroups

Elevate during Elevate during treatmenttreatment



Fracture HealingFracture Healing

Fracture HealingFracture Healing Electrical current Electrical current

triggers bone growthtriggers bone growth Piezoelectric effect Piezoelectric effect

within the collagen within the collagen matrixmatrix

Alternating currentAlternating current– Applied transcutaneouslyApplied transcutaneously– Similar to diathermy Similar to diathermy

units (no heat units (no heat production)production)

Direct currentDirect current– Implanted electrodes Implanted electrodes


Contraindications and Contraindications and PrecautionsPrecautions

Contraindications and Contraindications and PrecautionsPrecautions

Areas of sensitivityAreas of sensitivity– Carotid sinusCarotid sinus– EsophagusEsophagus– LarynxLarynx– PharynxPharynx– Around the eyesAround the eyes– Temporal regionTemporal region– Upper thoraxUpper thorax

Severe obesitySevere obesity EpilepsyEpilepsy In the presence of In the presence of

electronic monitoring electronic monitoring equipment equipment

Cardiac disabilityCardiac disability Demand-type Demand-type

pacemakerspacemakers Pregnancy (over lumbar Pregnancy (over lumbar

and abdominal area)and abdominal area) Menstruation (over Menstruation (over

lumbar and abdominal lumbar and abdominal area)area)

Cancerous lesions (over Cancerous lesions (over area)area)

Sites of infection (over Sites of infection (over area)area)

Exposed metal implants Exposed metal implants

© 2005 – fa davis electrical stimulation techniques

Documents

current flow slide

shortest path slide

resistance ion flow

type of contraction

pain nerves pain

electrode size

electrode proximity

order nerves