Short Wave Diathermy Used in Medical Field

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

4.  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

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

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

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

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

13.  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.  Fat cells
 Electron cloud is distorted but
negligible heat is produced
 Least efficient heat production

15.  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

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

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

20.  Longitudinal
- plates are placed at each end of the
limb

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

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

23.  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.  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.  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.  Increase blood flow
 Assist in resolution of inflammation
 Increase extensibility of deep
collagen tissue
 Decrease joint stiffness
 Relieve deep muscle pain and spasm

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

29.  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

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

33.  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.  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.  Increased blood flow or circulation to
the area
 Increased tissue temperature
 Increased metabolism
 Facilitate relaxation
 Increased pain threshold
 Decreased blood viscosity

36.  Soft tissue injury
 Mobilization
 Pain relief

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

39. 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.