DIATHERMY

1. DIATHERMY PT 156: Physical Agents 1 AilaNica J. Bandong, PTRP Instructor Department of Physical Therapy UP-College of Allied Medical Professions

2. Objectives 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

3. What is DIATHERMY? • The use of non-ionizing electromagnetic energy from the radio-frequency spectrum as therapeutic agent

4. Types of Diathermy • 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

5. SHORTWAVE DIATHERMY

6. Superficial and deep heating modality • Frequency - 27.12 MHz • Wavelength - 11 m • Method of HeatTransfer - Conversion • Manner of Delivery - continuous - pulsed

7. Continuous vs Pulsed SWD

8. PULSED SWD • Pulse Repetition Rate (PRR) - 15 to 800 Hz • Pulse Duration (PD) - 25 to 400 microseconds • Peak Pulse Power (PPP) - 100 to 1000 watts • Duration - 20 minutes (5-15 acute; 10-20 chronic)

9. Calculating Mean Power in PSWD Cycle Duration = 1000 / PRR % cycle SWD delivered = (PD x 100) / Cycle Duration Mean Power delivered = PPP x % cycle SWD

10. SHORTWAVE DIATHERMY UNIT

11. HEAT PRODUCTION • Dependent on: SPECIFIC ABSORPTION RATE Tissue conductivity charged molecules dipolar molecules non-polar molecules Electrical field magnitude

12. Charged Molecules • Ions and certain proteins • Molecules are accelerated along lines of electric force • Most efficient way of heat production + - - + + - + -

13. Dipolar Molecules • 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

14. Non-Polar Molecules • Fat cells • Electron cloud is distorted but negligible heat is produced • Least efficient heat production

15. ! Clinical Implication ! • 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

16. SHORTWAVE DIATHERMYCondenser InductionField Field

17. CONDENSER FIELD • 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

18. Ways of Application • Contraplanar - aka Transverse positioning - plates are on either side of the limb

19. Ways of Application • Coplanar - plates parallel with the longitudinal section of the body part; same side

20. Ways of Application • Longitudinal - plates are placed at each end of the limb

21. In what way should SWD be applied? • No conclusive evidence as to the technique of application that will produce the most effect on the heated tissue (Kitchen and Bazin, 1996)

22. ! GUIDELINES ! Electrodes should be: • Equal in size • Slightly larger than the area treated • Equidistant and at right angles to the skin surface

23. INDUCTION FIELD • 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

24. Arrangement of Inductive Coil • Monode: coil arranged in one plane • Hinged Diplode: permits electrode to be positioned at various angles around the three sides of the body part, or in one plane

25. Which is more effective: condenser or induction field? • 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

26. THERAPEUTIC EFFECTS(continuous and pulsed) • Increase blood flow • Assist in resolution of inflammation • Increase extensibility of deep collagen tissue • Decrease joint stiffness • Relieve deep muscle pain and spasm

27. INDICATIONS • 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

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

29. INDICATIONS • 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

30. MICROWAVEDIATHERMY

31. Superficial and deep heating • Frequency: 300 MHz to 300 GHz • Wavelength: 1m to 1mm • Therapeutic Parameters: A. 122.5 mm – 2456 MHz B. 327 mm – 915 MHz C. 690 mm – 433.9 MHz • Dosage: acute 5 to 15 minutes chronic 10 to 20 minutes

32. MICROWAVE DIATHERMY APPARATUS

33. How is microwave produced? • 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

34. Fate of Microwave • 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

35. THERAPEUTIC EFFECTS • Increased blood flow or circulation to the area • Increased tissue temperature • Increased metabolism • Facilitate relaxation • Increased pain threshold • Decreased blood viscosity

36. INDICATIONS • Soft tissue injury • Mobilization • Pain relief

37. CONTRAINDICATIONS • 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

38. PRECAUTIONS • Operator should observe caution when handling the machine: same contraindications apply

39. References 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.