Shortwave

and

Microwave Diathermy

Jennifer Doherty-Restrepo, MS, LAT, ATC Entry-Level ATEP

Therapeutic 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