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.
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