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Shortwave and Microwave Diathermy. Diathermy. Application of High-Frequency Electromagnetic Energy Used To Generate Heat In Body Tissues Heat Produced By Resistance of Tissues Also Used For Non-Thermal Effects. Physiologic Responses To Diathermy.

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Presentation Transcript
  • Application of High-Frequency Electromagnetic Energy
  • Used To Generate Heat In Body Tissues
  • Heat Produced By Resistance of Tissues
  • Also Used For Non-Thermal Effects
physiologic responses to diathermy
Physiologic Responses To Diathermy
  • Not Capable of Producing Depolarization and Contraction of Muscles
    • Wavelengths Too Short
physiologic responses to diathermy4
Physiologic Responses To Diathermy
  • Physiologic Effects Are Those of Heat In General
    • Tissue Temperature Increase
    • Increased Blood Flow (Vasodilation)
    • Increased Venous and Lymphatic Flow
    • Increased Metabolism
    • Changes In Physical Properties of Tissues
    • Muscle Relaxation
    • Analgesia
diathermy heating
Diathermy Heating
  • Doses Are Not Precisely Controlled Thus The Amount of Heating Cannot Be Accurately Measured
  • Heating= Current2 X Resistance
non thermal effects
Non-Thermal Effects
  • Pulsed SWD Used To Treat Soft Tissue Injuries and Wounds
  • Related To Depolarization of Damaged Cells
    • Loss of Cell Division
    • Loss of Proliferation
    • Loss of Regenerative capabilities
  • Repolarization Corrects Cell Dysfunction
shortwave diathermy
Shortwave Diathermy
  • Radio Transmitter With FCC Assigned Frequencies
    • 27.12 MHz at 11 M
    • 13.56 MHz at 22 M
    • 40.68 MHz at 7.5 M
shortwave diathermy unit
Shortwave Diathermy Unit
  • Power Supply Powers Radio Frequency Oscillator (RFO)
  • RFO Provides Stable Drift-Free Oscillations at Given Frequency
  • Power Amplifier Generate Power To Drive Electrodes
  • Output Resonant Tank Tunes In The Patient for Maximum Power Transfer
shortwave diathermy unit9
Shortwave Diathermy Unit
  • A=Power Switch
  • B=Timer
  • C=Power Meter(monitors current from power supply not current entering patient-volume control)
  • D=Output Intensity(%max power to patient)
  • E=Tuning Control(tunes output from RFO)
shortwave diathermy unit10
Shortwave Diathermy Unit
  • Power Output Should Provide Energy To Raise Tissue Temp To Therapeutic Range (40-45 deg C) (80-120 watts)
  • Should Exceed SAR-Specific Absorption Rate (rate of energy absorbed /unit area of tissue mass)
adjusting swd unit
Adjusting SWD Unit
  • Manual vs Automatic Tuning
  • 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
shortwave diathermy unit12
Shortwave Diathermy Unit
  • Generates Both an Electrical and a Magnetic Field
  • Ratio Depends on Characteristics of Both The Generator and the Electrodes
    • SWD Units at 13.56 MHz= Stronger Magnetic Field
    • SWD Units at27.12 MHz = Stronger Electrical Field
swd electrodes
SWD Electrodes
  • Capacitor Electrodes
  • Inductor Electrodes
  • Selection of Appropriate Electrodes Can Influence The Treatment
capacitor electrodes
Capacitor Electrodes
  • Create Stronger Electrical Field Than Magnetic Field
  • Ions Will Be Attracted Or Repelled Depending on the Charge of the Pole
capacitor electrodes15
Capacitor Electrodes
  • Electrical Field Is The Lines of Force Exerted on Charged Ions That Cause Movement From One Pole To Another
  • Center Has Higher Current Density Than Periphery

Capacitor Electrodes

  • Patient Is Between Electrodes and Becomes Part of Circuit
  • Tissue Is Between Electrodes in a Series Circuit Arrangement
electrical field
Electrical Field
  • The Tissue That Offers The Greatest Resistance To Current Flow Develops The Most Heat
  • Fat Tissue Resists Current Flow
  • Thus Fat Is Heated In An Electrical Field
  • Typical With Capacitor Electrodes
capacitor electrodes air space plates
Capacitor Electrodes(Air Space Plates)
  • Two Metal Plates Surrounded By Plastic Guard
  • Can Be Moved 3cm Within Guard
  • Produce High-Frequency Oscillating Current
  • When Overheated Discharges To Plate Of Lower Potential
air space plate electrodes
Air Space Plate Electrodes
  • Area To Be Treated Is Placed Between Electrodes Becoming Part of Circuit
air space place electrodes
Air Space Place Electrodes
  • Sensation Of Heat In Direct Proportion To Distance Of Electrode From Skin
  • Closer Plate Generates More Surface Heat
  • Parts Of Body Low In Subcutaneous Fat Best Treated
capacitor electrodes pad electrodes
Capacitor Electrodes(Pad Electrodes)
  • Greater Electrical Field
  • Patient Part of Circuit
  • Must Have Uniform Contact (toweling)
  • Spacing Equal To Cross-sectional Diameter of Pads
  • Part To Be Treated Should Be Centered
pad electrodes
Pad Electrodes
  • Increasing The Spacing Will Increase The Depth Of Penetration But Will Decrease The Current Density
induction electrodes
Induction Electrodes
  • Creates A Stronger Magnetic Field Than Electrical Field
  • A Cable Or Coil Is Wrapped Circumferentially Around An Extremity Or Coiled Within n Electrode
induction electrodes24
Induction Electrodes
  • Passing Current Through A Coiled Cable Creates A Magnetic Field By Inducing Eddy Currents (small circular electrical fields) That Generate Heat
induction electrodes25
Induction Electrodes
  • Patient In A Magnetic Field Not Part Of A Circuit
  • Tissues In A Parallel Arrangement
  • Greatest Current Flow Through Tissue With Least Resistance
  • Tissue High In Electrolytic Content Respond Best To A Magnetic Field
induction electrodes cable electrode
Induction Electrodes(Cable Electrode)
  • Two Arrangements:
    • Pancake Coils
    • Wraparound Coils
  • Toweling Is Essential
  • Pancake Coil Must Have 6” in Center Then 5-10cm Spacing Between Turns
induction electrodes drum electrode
Induction Electrodes(Drum Electrode)
  • One Or More Monopolar Coils Rigidly Fixed In A Housing Unit
  • May Use More Than One Drum Depending On Area Treated
  • Toweling Important
heating with continuous swd
Heating With Continuous SWD
  • Patient Sensation Provides Basis For Recommendations Of Continuous SWD Dose I (Lowest) - No Sensation of Heat Dose II(Low) - Mild Heating Sensation Dose III(Medium)- Moderate or Pleasant Heating Sensation Dose IV(Heavy)-Vigorous Heating Within Pain Threshold
pulsed swd
Pulsed SWD
  • Referred To By Different Names
    • Pulsed Electromagnetic Energy (PEME)
    • Pulsed Electromagnetic Field (PEMF)
    • Pulsed Electromagnetic Energy Treatment (PEMET)
pulsed swd31
Pulsed SWD
  • Interrupted Output Delivered In Series Of High-Frequency Bursts (20-400usec)
  • Pulse Rate Selected With Pulse Frequency Control
  • Off-Time Longer Than On-Time
  • Low Mean Power Output
  • Uses Drum Electrode
shortwave diathermy vs ultrasound
Shortwave Diathermy vs.Ultrasound
  • Pulsed SWD Produces The Same Magnitude And Depth Of Muscle Heating as 1MHz Ultrasound (Draper, JAT 1997)
treatment time
Treatment Time
  • Most Typically SWD Treatments Last For 20-30 Minutes
  • Remember As Skin Temperature Rises Resistance Falls
microwave diathermy
Microwave Diathermy
  • Two FCC Assigned Frequencies-2456 MHz and 915 MHz
  • MWD Has Higher Frequency and Shorter Wavelength Than SWD
  • Generates Strong Electrical Field and Relatively Little Magnetic Field
  • Depth Of Penetration Is Minimal In Areas With Subcutaneous Fat > 1 cm
microwave diathermy unit
Microwave Diathermy Unit
  • A= Power Switch
  • B=Timer
  • C=Output Meter (indicates relative output in watts
  • D= Power Output Level Knob
  • E= Amber Light-Warming up / Red Light- Ready
mwd applicators electrodes
MWD Applicators (Electrodes)
  • Circular Shaped Applicators
    • 4” or 6”
    • Maximum Temperature At Periphery
  • Rectangular Shaped Applicators
    • 4.5 x 5” or 5 x 21”
    • Maximum Temperature At Center
microwave applicator set up
Microwave Applicator Set-Up
  • Microwave Applicator Beams Energy To Patient
  • Must Pay Attention To Cosine Law
  • In 915 MHz Units Applicators Placed 1 cm From Skin
  • 2456 MHz Units Have Manufacturer Recommended Distances and Power Outputs (Uses Antenna)

When Should Diathermy Be Used?

  • If The Skin Or Some Underlying Soft Tissue Is Tender And Will Not Tolerate Pressure
  • In Areas Where Subcutaneous Fat Is Thick And Deep Heating Is Required

When Should Diathermy Be Used?

  • When The Treatment Goal Is To Increase Tissue Temperatures In A Large Area