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
- 27.12 MHz
 Wavelength
- 11 m
 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)
- 100 to 1000 watts
 Duration
- 20 minutes (5-15 acute; 10-20 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:
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

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: 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
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
 Active
CA
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.