Shortwave and Microwave Diathermy

Jennifer Doherty-Restrepo, MS, LAT, ATCJennifer Doherty-Restrepo, MS, LAT, ATCEntry-Level ATEPEntry-Level ATEP

Therapeutic ModalitiesTherapeutic Modalities

Diathermy

• Application of high-frequency ___________________ energy

• ______________ diathermy– Used to generate ______ in body tissues– ______ produced as a result of the __________ of

tissues to the passage of energy

• ___________ diathermy– Used for ________________ effects– Renewed interest due to research documenting

efficacy

Physiologic Responses To Diathermy: Thermal Effects

• Tissue temperature __________

• Increased blood flow (vasodilation)

• ___________ venous and lymphatic drainage

• ___________ metabolism

• Changes in physical properties of tissues

• Muscle _________

• Analgesia

Diathermy Heating

• Diathermy parameters are not precisely controlled, thus the amount of heating cannot be accurately measured

• Heating occurs in proportion to the square of the current density and in direct proportion to the resistance of the tissue– Heating = ______ X ________

Physiologic Responses To Diathermy: Non-Thermal Effects

• Pulsed shortwave diathermy is used to treat ________ injuries and wounds

• Mechanism of effectiveness is related to the _____________ of damaged cells– Loss of cell division– Loss of proliferation– Loss of regenerative capabilities

• ____________ occurs with treatment, thus correcting cell dysfunction

• Not capable of producing _____________ to elicit muscle ______ – Wavelengths too short

Shortwave Diathermy

• Shortwave diathermy unit is a radio transmitter

• Three frequencies available:– ______ MHz, wavelength of 11 m– ______ MHz, wavelength of 22 m– ______ MHz, wavelength of 7.5 m

Shortwave Diathermy Unit

• _______________: provides power to radio frequency oscillator (RFO)

• ____: provides stable, drift-free oscillations at given frequency

• _____________: generates power to drive electrodes

• __________________:tunes in the athlete as part of the circuit to allow for maximum power transfer

Shortwave Diathermy Unit

• A =Power switch• B = Timer• C = Power meter

– Monitors current from power supply, not current entering patient

• D = Output intensity (% max power to patient)• E = Tuning control (tunes output from RFO)

Shortwave Diathermy Unit

• Power output should provide energy to ______ tissue temperature to therapeutic range – Therapeutic range = ___________

• ____________________________: represents the rate of energy absorbed per unit area of tissue mass– Power range required to elicit tissue temperature

increase = ____________

Adjusting the Shortwave Diathermy Unit

• ________________: adjusts patient circuit– Set output intensity at ______ of maximum – Adjust tuning control until power output meter reaches

______ – Then adjust down to ______________, which is about

50% of maximum output– If patient is able to tolerate more than 50% of

maximum output, he/she is ___________________

• ________________: automatically sets output intensity– Automatically turns off if patient is _______________

Shortwave Diathermy Unit

• Generates both an _______ and a _______ field

• Ratio depends on characteristics of both the ______ and the _________– SWD units at 13.56 MHz = stronger ________

field– SWD units at 27.12 MHz = stronger ________

field

SWD Electrodes

• 2 types of electrodes– _____________________

• Air space plates • Pad electrodes

– _____________________• Cable electrodes • Drum electrodes

• Selection of appropriate electrodes can influence the treatment

Capacitor Electrodes

• Create stronger ______ field than ______ field• Ions will be attracted or repelled depending on the

charge of the ______

Capacitor Electrodes

• Electrical field– Lines of force exerted on

charged ions that cause _____________________ ________________r

• ______ has higher current density than __________

Capacitor Electrodes

Patient is between electrodes Becomes part of circuit

Tissue is between electrodes __________ circuit

arrangement

Electrical Field

• The tissue that offers the greatest resistance to current flow develops the __________

• Fat tissue ______ current flow

• Therefore, tissues with a ______ fat content are heated in an electrical field

• Typical with capacitor-type electrodes

Capacitor Electrodes: Air Space Plates

• Two metal plates surrounded by glass or plastic guard

• Metal plates can be adjusted 3cm within guard

• Produce ________________ oscillating current

• When one metal plate is overloaded, it discharges to other plate of lower potential

Capacitor Electrodes: Air Space Plates

• Area to be treated is placed between electrodes

• Treatment area becomes part of the external circuit

Capacitor Electrodes: Air Space Plates

• Sensation of heat in _____ proportion to the distance of metal plate from the skin

• The closer the plate to the skin, the _____ the energy transmission (______ reflection)– Generates more surface heat in ____ and _____________

Capacitor Electrodes:Pad Electrodes

• Greater ______ field than ______ field• Patient is between electrodes

– Becomes part of external circuit

Capacitor Electrodes:Pad Electrodes

• Must have uniform contact pressure on the body– Toweling to prevent burns

• Spacing between electrodes is equal to the ____________ ________ of pads

Capacitor Electrodes:Pad Electrodes

• Area to be treated should be ______ between electrodes

• Increasing the space between electrodes will ______ the depth of penetration but will _________ the current density– Vice versa also true

Induction Electrodes• Creates a stronger ________ field than ________

field• A cable or coil is wrapped circumferentially

around an extremity or coiled within an electrode• Passing electrical current through coiled cable

creates a ________ field by inducing ________ _________ – Small circular electrical fields that generate heat

Induction Electrodes

• Patient placed in a magnetic field – NOT part of a circuit

• Tissues in treatment area are in _________ arrangement to magnetic field– Greatest current flow through tissue with least

resistance– Tissue high in __________________ respond

best to a magnetic field

Induction Electrodes:Cable Electrode

• Two arrangements: – Pancake coils

– Wraparound coils

• Requires at least ____ of toweling between skin and coil

• Spacing between turns in coil must be ______

Induction Electrodes:Drum Electrode

• One or more monopolar coils rigidly fixed in a housing unit

• May use more than one drum depending on treatment area

• Toweling important to prevent ______

Continuous Shortwave Diathermy

• Patient sensation provides basis for recommendations of continuous SWD

• Dose I (______): no sensation of heat

• Dose II (______): mild heating sensation

• Dose III (______): moderate or pleasant heating sensation

• Dose IV (______): vigorous heating with pain threshold

Pulsed Shortwave Diathermy

• Pulsed electromagnetic energy (PEME)

• Pulsed electromagnetic field (PEMF)

• Pulsed electromagnetic energy treatment (PEMET)

Pulsed Shortwave Diathermy

Pulsed Shortwave Diathermy

• Interrupted output delivered in series of high-frequency bursts (______)

• ______ _____selected with pulse frequency control

• Off-time ______ than on-time

• Mean power output is ______

• Uses drum electrode

Shortwave Diathermy vs. Ultrasound

Pulsed SWD produces the same magnitude and depth of muscle heating as 1 MHz ultrasound

(Draper, JAT 1997)

Shortwave Diathermy:Treatment Time

• Typically, 20 - 30 minutes

• Reminder: – As skin temperature rises, resistance falls

Microwave Diathermy

• Two frequencies available:– 2456 MHz – 915 MHz

• ______ frequency and ______ wavelength as compared to shortwave diathermy

• Generates strong ______ ______ and relatively little ________ field

• Depth of penetration is minimal in areas with subcutaneous fat > 1 cm

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

Microwave Diathermy Electrodes

• Circular-shaped electrodes– 4” or 6” in diameter

– Maximum temperature at periphery

• Rectangular-shaped electrodes– 4.5” x 5” or 5” x 21”

– Maximum temperature at center

Microwave Diathermy: Electrode Set-Up

• 915 MHz units– Electrodes are placed 1 cm from skin

• 2456 MHz units – Manuel includes manufacturer recommended

distances and power outputs (uses antenna)

• Reminder: Cosine Law– Energy should be administered at ______ to

reduce ______

When Should Diathermy Be Used?

If the skin or some underlying soft tissue is tender and is unable to tolerate pressure

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

In areas where subcutaneous fat is thick and deep heating is required

If the skin or some underlying soft tissue is tender and is unable to tolerate pressure

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

In areas where subcutaneous fat is thick and deep heating is required