diathermy (1)

8/8/2019 Diathermy (1)

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DiathermyApplication of High-FrequencyElectromagnetic Energy

Used To Generate Heat In Body TissuesHeat Produced By Resistance of TissuesAlso Used For Non-Thermal Effects


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Physiologic Responses ToDiathermy

Not Capable of Producing Depolarization and

Contraction of Muscles Wavelengths Too Short


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Diathermy HeatingDoses Are Not Precisely Controlled ThusThe Amount of Heating Cannot BeAccurately Measured Basically means amount of heating patient

receives cannot be directly measured

Heating= Current 2 X Resistance


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Non-Thermal EffectsPulsed SWD Used To Treat Soft Tissue Injuries andWoundsRelated To Depolarization of Damaged Cells Loss of Cell Division Loss of Proliferation Loss of Regenerative capabilities

Repolarization Corrects Cell DysfunctionGenerates A Magnetic Field To Increase Na PumpActivity


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SWD Physiological Events SummaryElectromagnetic Radiation

CSWD PSWD

Electromag. Energy absorption

Incr. molecular KE cell ion-binding properties, proteinsynthesis, ATP production

Thermal Effect Athermal Effect

Increased cell metabolism and function

Enhanced soft-tissue healing


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Shortwave DiathermyRadio Transmitter With FCC AssignedFrequencies 2 7. 12 MHz at 11 M 13 .5 6 MHz at 22 M 40 .68 MHz at 7. 5 M


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Shortwave Diathermy UnitPower Supply Powers Radio FrequencyOscillator (RFO)RFO Provides Stable Drift-Free Oscillationsat Given FrequencyPower Amplifier Generate Power To DriveElectrodesOutput Resonant Tank Tunes In The Patientfor Maximum Power Transfer


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Possible Shortwave Diathermy Unit

A=Power SwitchB=Timer

C=Power Meter(monitors current from power supply notcurrent entering patient-volume control)D=Output Intensity(%max power to patient)E=Tuning Control(tunes output from RFO)


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Shortwave Diathermy UnitPower Output Should Provide Energy ToRaise Tissue Temp To Therapeutic Range

(40 -45 deg C) ( 8 0 -120 watts)Should Exceed SAR-Specific AbsorptionRate (rate of energy absorbed /unit area of tissue mass)


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Adjusting Resonance of SWD Unit(Tuning)

Manual vs Automatic Tuning When patients circuit (biologic tissue) oscillates at same

frequency as device frequency Only when tuned will is the electromagnetic energy fully delivered Most automatic Can lose tuning due to movement at skin/electrode interface

Manual Tuning (adjusts patient circuit) Set Output Intensity at 30 -40 % Adjust Tuning Control Until Power Output Meter Reaches Max Then Adjust Down to Patient Tolerance Which Is About 50 % If More Than 50 % Patient Is Out of Resonance


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Shortwave Diathermy UnitGenerates Both an Electrical and aMagnetic FieldRatio Depends on Characteristics of BothThe Generator and the Electrodes SWD Units at 1 3 .5 6 MHz= Stronger Magnetic

Field SWD Units at 2 7. 12 MHz = Stronger Electrical

Field


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SWD ElectrodesCapacitor ElectrodesInductor ElectrodesSelection of Appropriate Electrodes CanInfluence The Treatment


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Capacitor (Condenser) ElectrodesCreate Stronger Electrical Field Than MagneticField

Ions Will Be Attracted Or Repelled Depending onthe Charge of the Pole


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Capacitor Electrodes

Electrical Field Is The Linesof Force Exerted onCharged Ions That Cause

Movement From One PoleTo Another Center Has Higher CurrentDensity Than Periphery


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Capacitor Electrodes

Patient Is BetweenElectrodes and BecomesPart of CircuitTissue Is BetweenElectrodes in a SeriesCircuit Arrangement


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Electrical FieldThe Tissue That Offers The GreatestResistance To Current Flow Develops TheMost Heat Fat Tissue Resists Current Flow Thus Fat Is Heated In An Electrical Field

Precaution: electrical field may overheat areawith large fat content


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Capacitor Electrodes(Air Space Plates)

Two Metal Plates SurroundedBy Plastic GuardCan Be Moved 3 cm WithinGuardProduce High-Frequency

Oscillating Current


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Air Space Plate Electrodes

Area To Be Treated Is

Placed BetweenElectrodes BecomingPart of Circuit


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Air Space Place Electrodes

Sensation Of Heat In Direct Proportion ToDistance Of Electrode From SkinCloser Plate Generates More Surface HeatParts Of Body Low In Subcutaneous Fat BestTreated


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Capacitor Electrodes(Pad Electrodes)

Greater Electrical Field

Patient Part of CircuitMust Have UniformContact (toweling)Spacing Equal To Cross-sectional Diameter of PadsPart To Be TreatedShould Be Centered


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Pad ElectrodesIncreasing TheSpacing Will Increase

The Depth Of Penetration But WillDecrease The CurrentDensityCapacitive MethodGood for TreatingSuperficial SoftTissues


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Induction MethodCreates A Stronger Magnetic Field ThanElectrical FieldA Cable Or Coil Is WrappedCircumferentially Around An Extremity Or Coiled Within n Electrode


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Induction Electrodes

Passing Current Through A Coiled Cable Creates

A Magnetic Field By Inducing Eddy Currents(small circular electrical fields) That GenerateHeat


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Induction ElectrodesPatient In A Magnetic Field Not Part Of A CircuitGreatest Current Flow Through Tissue With Least

Resistance Tissues react like a parallel circuit Fat does not provide as much resistance to

electromagnetic energy

Tissue High In Electrolytic Content Respond BestTo A Magnetic Field Muscle and blood

Precaution: Not as much superficial sensation of heat with electromagnetic


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Induction Electrodes(Cable Electrode)

Two Arrangements: Pancake Coils

Wraparound CoilsToweling Is EssentialPancake Coil MustHave 6 in Center Then5 -10 cm SpacingBetween TurnsBest Frequency


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Induction Electrodes(Drum Electrode)

One Or MoreMonopolar Coils

Rigidly Fixed In AHousing UnitMay Use More ThanOne Drum DependingOn Area TreatedPenetration Deeper Soft Tissues

Toweling Important


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Heating With Continuous SWDPatient Sensation Provides Basis For Recommendations Of Continuous SWD

Dose I (Lowest) (< 3 8 W) - No Sensation of HeatDose II (Low) (~ 8 0 W)- Mild Heating SensationDose III (Medium) ( 8 0 -300 W) - Moderate or Pleasant Heating SensationDose IV (Heavy) (> 300 W) -Vigorous HeatingWithin Pain Threshold


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Pulsed SWDReferred To By Different Names Pulsed Electromagnetic Energy (PEME) Pulsed Electromagnetic Field (PEMF) Pulsed Electromagnetic Energy Treatment

(PEMET)


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Pulsed SWD


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PSWD Mean Power CalculationsPulse Period (Pulse on + off time) = Peak Pulse Power (W) / Pulse Rep Freq (Hz)

Percentage On Time = Pulse Duration (msec) / Pulse Period (msec)

Mean Power = Peak Pulse Power (W) / Percentage on Time


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ExamplePeak Pulse Power = 8 00 WPulse Duration = .4 msPulse Frequency = 200 HzPulse Period = 8 00 W / 200 Hz = 4 ms% on time = .4 / 4 = .10 or 1 0 %

Mean Power = 1 0 % of 8 00 = 8 0 W End Result = thermal effect < 3 8 W = no heating


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Pulsed SWDInterrupted Output Delivered In Series Of High-Frequency Bursts ( 40 -400 usec)Pulse Rate Selected With Pulse FrequencyControl (11 000 Hz)Off-Time Longer Than On-TimeLow Mean Power OutputUses Drum Electrode


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Shortwave Diathermy vs .Ultrasound

Pulsed SWD Produces The Same Magnitude And DepthOf Muscle Heating as 1MHz Ultrasound (Draper, JAT199 7 )


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Treatment TimeMost Typically SWD Treatments Last For

20 -30 MinutesRemember As Skin Temperature RisesResistance Falls


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When Should Diathermy

Be Used?If The Skin Or Some Underlying Soft TissueIs Tender And Will Not Tolerate PressureIn Areas Where Subcutaneous Fat Is Thick And Deep Heating Is Required

Induction methodWhen The Treatment Goal Is To IncreaseTissue Temperatures Over A Large Area

If The Skin Or Some Underlying Soft TissueIs Tender And Will Not Tolerate PressureIn Areas Where Subcutaneous Fat Is Thick And Deep Heating Is Required

Induction methodWhen The Treatment Goal Is To IncreaseTissue Temperatures Over A Large Area


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SWD GuidelinesIndications Continuous and Pulsed

PrecautionsContraindications


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Microwave DiathermyTwo FCC Assigned Frequencies- 245 6 MHz and

9 15 MHzMWD Has Higher Frequency and Shorter Wavelength Than SWDGenerates Strong Electrical Field and RelativelyLittle Magnetic Field

Advantage: better focus wave on body, therebymore local heating affectsDisadvantage: Depth Of Penetration Is Minimal In

Areas With Subcutaneous Fat > 1 cm


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Microwave Diathermy Unit

A= Power SwitchB=Timer

C=Output Meter (indicates relative output in wattsD= Power Output Level KnobE= Amber Light-Warming up / Red Light- Ready


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MWD Applicators (Electrodes)

Circular Shaped Applicators 4 or 6

Maximum Temperature At PeripheryRectangular Shaped Applicators 4 .5 x 5 or 5 x 2 1

Maximum Temperature At Center


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Microwave Applicator Set-UpMicrowave Applicator Beams Energy ToPatient

Must Pay Attention To Cosine LawIn 9 15 MHz Units Applicators Placed 1 cmFrom Skin

245 6 MHz Units Have Manufacturer Recommended Distances and Power Outputs(Uses Antenna)


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Best Treated areas for Microwave

Tendons of foot, hand and wristAC and SC jointsPatellar tendonDistal tendons of hamstringsAchilles tendonOther areas of low subcutaneous fat

diathermy (1)

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