At the end of the lecture, the students should be able to:

Define diathermy Identify the parts of the SWD/MWD machine Describe how heat is produced in SWD/MWD Enumerate the therapeutic effects of diathermy Differentiate the types of SWD Enumerate the indications, contraindications,

and precautions/guidelines for the use of the modality

Use clinical decision making skill in choosing appropriate modality

Apply evidence regarding use of SWD/MWD

The use of non-ionizing electromagnetic energy from the radio-frequency spectrum as therapeutic agent

Long waveLong wave- longest wavelength 300 – 30 m- most penetrating- no longer utilized due to high potential of causing burns and interference with radio transmissions

ShortwaveShortwave MicrowaveMicrowave

Superficial and Superficial and deep heating deep heating modalitymodality

FrequencyFrequency- 27.12 MHz

WavelengthWavelength- 11 m

Method of Method of HeatHeat TransferTransfer- Conversion

Manner of Manner of DeliveryDelivery- continuous- pulsed

Pulse Repetition Rate (PRR)Pulse Repetition Rate (PRR)- 15 to 800 Hz

Pulse Duration (PD)Pulse Duration (PD)- 25 to 400 microseconds

Peak Pulse Power (PPP)Peak Pulse Power (PPP)- 100 to 1000 watts

DurationDuration- 20 minutes (5-15 acute; 10-20 chronic)

1.1. Cycle Duration = 1000 / PRRCycle Duration = 1000 / PRR

2.2. % cycle SWD delivered =% cycle SWD delivered =

(PD x 100) / Cycle Duration(PD x 100) / Cycle Duration

3.3. Mean Power delivered =Mean Power delivered =

PPP x % cycle SWDPPP x % cycle SWD

Dependent on:SPECIFIC ABSORPTION RATE

Tissue conductivity

charged molecules

dipolar molecules

non-polar molecules

Electrical field magnitude

Ions and certain proteins

Molecules are accelerated along lines of electric force

Most efficient way of heat production

+

+

+

+

-

-

-

-

Water and some proteins

Positive pole of the molecule aligns itself to the negative pole of the electric field (vice versa)

Moderately efficient heat production

Fat cells Electron cloud is distorted but

negligible heat is produced Least efficient heat production

Blood, having high ionic content, is a good conductor vascular tissues as well

Metal and sweat are good conductors if metal implants and sweat are present within the electric field, may cause burn

Patient’s tissues are used as DIELECTRIC between the conducting electrodes

Oscillation and rotation of the molecules of the tissues produces heat

Either flexible metal plates (malleable) or rigid metal discs can be used as electrodes

Can be applied in 3 ways: contraplanar, coplanar, or longitudinal

ContraplanarContraplanar- aka Transverse positioning- plates are on either side of the limb

CoplanarCoplanar- plates parallel with the longitudinal section of the body part; same side

LongitudinalLongitudinal- plates are placed at each end of the limb

No conclusive evidence as to the technique of application that will produce the most effect on the heated tissue (Kitchen and Bazin, 1996)

Electrodes should be:Electrodes should be: Equal in size Slightly larger than the area treated Equidistant and at right angles to

the skin surface

Patient is in the electromagnetic field or the electric circuit produce strong magnetic field induce electrical currents within the body (EDDY currents)

Utilizes either an insulated cable or an inductive coil applicator

Monode:Monode: coil arranged in one plane

Hinged Diplode:Hinged Diplode: permits electrode to be positioned at various angles around the three sides of the body part, or in one plane

Some studies argue that inductive diathermy produces greater increase in temperature of deeper tissues compared to condenser/capacitive technique

Any deep effects following capacitive technique requires considerable increase in superficial tissue temperature

Increase blood flow Assist in resolution of inflammation Increase extensibility of deep

collagen tissue Decrease joint stiffness Relieve deep muscle pain and

spasm

Soft tissue healing- conflicting evidence as regards effectiveness of SWD- controlled animal studies revealed insignificant results as well as trials involving human subjects (Kitchen and Bazin, 1996); to date, no studies in the treatment setting was conducted

Recent ankle injuries- inconclusive results following three double-blind protocols (Kitchen and Bazin)

Pain Syndromes- Pulsed SWD may provide better pain relief in some musculoskeletal conditions (neck and back) than SWD

A. Nerve Regeneration- studies were done on cats and rats- PSWD induced regeneration of axons, acceleration and recovery of nerve conduction

B. Osteoarthritis- no established effect

C. Post-operative- insignificant (abdominal surgery

Superficial and deep heatingSuperficial and deep heating Frequency:Frequency: 300 MHz to 300 GHz Wavelength:Wavelength: 1m to 1mm Therapeutic Parameters:Therapeutic Parameters:

A. 122.5 mm – 2456 MHzB. 327 mm – 915 MHzC. 690 mm – 433.9 MHz

Dosage:Dosage: acute 5 to 15 minutes chronic 10 to 20 minutes

Direct current (DC) is shunted to the cathode in the magnetron valve

Release of electrons from the cathode to the multi-cavity anode valve

Electrons oscillate at predetermined frequency

High frequency alternating current is transmitted along a coaxial cable

Coaxial cable transmits energy to a director

AbsorbedAbsorbed- energy is taken up by the material

TransmittedTransmitted- pass through the material without being absorbed

RefractedRefracted- direction of propagation is altered

ReflectedReflected- turned back from the surface

Increased blood flow or circulation to the area

Increased tissue temperature Increased metabolism Facilitate relaxation Increased pain threshold Decreased blood viscosity

Soft tissue injury Mobilization Pain relief

Pacemakers Metal implants Impaired

sensation Pregnancy Hemorrhage Ischemic

Tissue Testicles and

eyes

Malignant CA Active TB Fever Thrombosis X-ray exposure Uncooperative

patient Areas of poor

circulation

Operator should observe caution when handling the machine: same contraindications apply

Gorgon, E. J. (2004). Lecture notes on high frequency currents: Shortwave and microwave diathermy. University of the Philippines- College of Allied Medical Professions.

Hayes, K. W. (1993). Manual for physical agents (4th Ed). Connecticut: Appleton and Lange.

Hecox, B., Mehreteab, T. A., and Weisberg, J. (1994). Physical agents: A comprehensive text for physical therapists. Connecticut: Appleton and Lange.

Kitchen, S. and Bazin, S. (1996). Clayton’s electrotherapy (10th ed). Philadelphia: W.B. Saunders Company.

Low, R. Reed, A. (1995). Electrotherapy explained: Principles and practice (2nd Ed). Oxford: Butterworth-Heinemann Ltd.

Michlovitz, S. L. (1996). Thermal agents in rehabilitation (3rd Ed). Philadelphia: F. A. Davis Company.