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

 Superficial and deep heating modality  Frequency MHz  Wavelength - 11 m  Method of HeatTransfer  Method of Heat Transfer - Conversion  Manner of Delivery - continuous - pulsed

 Pulse Repetition Rate (PRR) - 15 to 800 Hz  Pulse Duration (PD) - 25 to 400 microseconds  Peak Pulse Power (PPP) to 1000 watts  Duration - 20 minutes (5-15 acute; chronic)

1.Cycle Duration = 1000 / PRR 2.% cycle SWD delivered = (PD x 100) / Cycle Duration 3.Mean Power delivered = PPP 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

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

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

 Longitudinal - 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:  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 heating  Frequency:  Frequency: 300 MHz to 300 GHz  Wavelength:  Wavelength: 1m to 1mm  Therapeutic Parameters: A mm – 2456 MHz B. 327 mm – 915 MHz C. 690 mm – 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

 Absorbed - energy is taken up by the material  Transmitted - pass through the material without being absorbed  Refracted - direction of propagation is altered  Reflected - 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 (4 th 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 (10 th ed). Philadelphia: W.B. Saunders Company. Low, R. Reed, A. (1995). Electrotherapy explained: Principles and practice (2 nd Ed). Oxford: Butterworth-Heinemann Ltd. Michlovitz, S. L. (1996). Thermal agents in rehabilitation (3 rd Ed). Philadelphia: F. A. Davis Company.