SWD (Short wave diathermy)- Physiotherapy in electrotherapy

1. Dr. Mumux Mirani
BPT, MPT Sports, PhD Scholar,
Asst. Professor
SPB Physiotherapy College,
Surat.

2. Whenever I ask something, like…
What is SWD???
Le ME*
Le
SYBPT*
SWD

3. What patients tell us when we give
electrotherapy

6. EMF:
• it is the force producing the flow of electrons
from the more negative to the less negative
body if similar bodies are charged with
different qualities of electricity.
• If a path way is provided the EMF produces a
flow of electrons but if there is no pathway no
current can pass, but force still exist.
• The greater the potential difference the
greater is the EMF and both are measured in
the same unit volt.

7. • A volt is that EMF which when applied to
conductor with a resistance of one ohm
produces a current of one ampere.
• 1 volt ＝ 1 joule/coulomb
• It is a electrical energy produced per unit
charge inside the source.

8. • Electron moves only so long as a potential
difference exists between the ends of the
pathway so long as the EMF is maintained.
• a potential difference can be produced by
friction but when a pathway is completed the
charges quickly neutralize each other and
current causes to flow.

9. • Other methods of producing potential
difference and EMF are
• by the chemical action in cells
• by electromagnetic induction in dynamo,
• by heat in a thermocouple and
• from radiant energy in a photoelectric cell.

10. • With all these methods the potential
difference is maintained in spite of the
electron flow.
• As fast as electron moves away from the
negative end of the conductor they are
replaced by other from the generator while
those reach the positive end are drawn away
by the generator.
• Thus the potential difference is maintained
and current continue to flow.

11. • Resistance: it is the obstruction to the flow of
electrons in a conductor.
• Unit is ohm. Resistance is directly proportional
to length and inversely proportional to area of
cross section, temperature and numbers of
free electrons in a unit volume.

12. • Ohm’s law: the current flowing through a
metallic conductor is proportional to the
potential difference across its ends provided
that all physical conditions remain constant.
• The magnitude of an electric current varies
directly with the EMF and inversely with the
resistance.

13. • I＝E/R
• I＝ current in ampere
• R ＝ resistance in ohms
• E ＝ EMF in volts
• So 1 ohm is the resistance of a body in such
that 1 volt potential difference across the
body results in a current of 1 ampere through
it.)

14. • Displacement current:
• Ordinary electric current called conductive
current whether steady or varying produce
magnetic field in the vicinity of the current.
• A displacement of electrical energy occurs as
the result of polarization of the tissues and its
magnitude depends upon the capacitance of
the tissue and the frequency of the alternating
current.

15. • The use of inductive applicator relies on the
tissue being placed within a rapidly alternating
magnetic field which is generated by passing
the high frequency current through a coil
these results in the creation of eddy currents
within the tissues induced by the oscillating
electromagnetic field

17. SHORT WAVE DIATHERMY
• means the application of high
frequency electrical energy to the
body tissues in order to bring
physiological and therapeutic
effects, these effects can be
achieved by thermal or non
thermal effect.

19. • Radio waves are a type of electromagnetic
radiation with wavelengths in the
electromagnetic spectrum longer than infrared
light.
• Radio waves have frequencies from 300 GHz to
as low as 3 kHz, and corresponding wavelengths
ranging from 1 millimeter to 100 kilometers.

20. Characteristics of radio wave
• RF current does not penetrate deeply into
electrical conductors but tends to flow along
their surfaces; this is known as the skin effect.
For this reason, when the human body comes in
contact with high power RF currents it can cause
superficial but serious burns called RF burns.

21. • RF currents applied to the body often do not
cause the painful sensation of electric shock
as do lower frequency currents. This is
because the current changes direction too
quickly to trigger depolarization of nerve
membranes.
• RF current can easily ionize air, creating a
conductive path through it.

22. • Ability to appear to flow through paths that
contain insulating material, like the
dielectric insulator of a capacitor.
• When conducted by an ordinary electric cable,
RF current has a tendency to reflect from
discontinuities in the cable such as connectors
and travel back down the cable toward the
source, causing a condition called standing
waves, so RF current must be carried by
specialized types of cable called transmission
line.

23. Uses of radiowave
• For invasive surgeries, using radiofrequency
ablation and cryoablation, sleep apnea.
• Magnetic resonance imaging (MRI) uses radio
frequency waves to generate images of the
human body.
• Radio frequencies at non-ablation energy levels
are sometimes used as a form of cosmetic
treatment that can tighten skin, reduce fat, or
promote healing.

24. • It is also a method of heating tissue
electromagnetically for therapeutic purposes
in medicine.
• Surgically, the extreme heat that can be
produced by diathermy may be used to
destroyneoplasms, warts, and infected tissues,
and to cauterize blood vessels to prevent
excessive bleeding.

25. • The technique is particularly valuable
in neurosurgery and surgery of the eye.
Diathermy equipment typically operates in the
short-wave radio frequency (range 1–
100 MHz) or microwave energy (range 434–
915 MHz).

26. • Pulsed electromagnetic field therapy (PEMF) is
a medical treatment that helps to heal bone
tissue reported in a recent NASA study.
• This method usually employs electromagnetic
radiation of different frequencies - ranging
from static magnetic fields, through extremely
low frequencies (ELF) to higher radio
frequencies (RF) administered in pulses.

27. 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 30 – 3 m
Microwave

28. • Dia means through and Thermo
means temperature heat.
• so ‘diathermy’ is coined from a
GREEK word meaning ‘through
heating.
• SWD refers to deep heating
produced by electric or magnetic
fields which alternate at high
(shortwave radio) frequencies.

29. SWD - INTRODUCTION
• A deep-heating modality
• Application of High-Frequency Electromagnetic Energy
• Non ionizing radiation of radiofrequency portion of
EMS
• wavelength lies between medium radio waves and
microwaves on the EMS
• All radio frequencies in the range of 10 MHz to 100 MHz
are called shortwave & because the device for producing
therapeutic heating is in this range, it is called “shortwave
diathermy”.
• wave length of 3 to 30 m
• Does Not stimulate MOTOR & SENSORY NERVES.
• No contraction of muscle is produced
• No Danger of CHEMICAL BURNS 29

30. • Therapeutic diathermy uses
radiofrequency of 27.12 MHz at
wavelength of 11 M
• widest band which prevents
interference with other frequency
bands used in communications

31. • other less common frequencies and
wavelengths are
40 .68 MHz with 7 . 5 m
13 .56 MHz with 22 m

32. Electromagnetic Phenomena
• Electromagnetic phenomena can be considered
from three different aspects:
• 1- Electrostatic
• concerns the electric force between the electric
charges.
• These forces act between any charges and their
strength and direction can be described by
drawing lines called lines of electric force.
• The area in which this force acts is called an
electric field.

34. Electromagnetic Phenomena
• 2- When charges move
it is referred to as an
electric current. An
inevitable consequence
of constantly moving
charges is the formation
of magnetic force at
right angles to the
direction of the charge
motion. The area in
which the magnetic
force is evident, called
the magnetic field.

35. Electromagnetic Phenomena
• 3. If an electric charge is
accelerated it causes the
production of an
electromagnetic radiations
which radiates away from
the moving charge and
once generated is
independent of the charge.
These radiations include
radio waves (SWD), visible
light and X-rays.

36. There Are Two Circuits Here:
Machine circuit : composed of a high frequency
generator, amplifier, oscillator coil.
Patient circuit: composed of a resonator coil, variable
capacitor, electrodes and the treated tissue.
1. (oscillator circuit) which produce high frequency
current coupled with
2. The patient circuit ( resonator circuit) through
inductors to transfer the electrical energy to the
patient.

37. Possible Shortwave Diathermy Unit
37
A=Power Switch
B=Timer
C=Milliameter (monitors current
from power supply not current
entering patient-volume control)
D= Intensity(%max power to patient)
E=Tuning Control(tunes output from
RFO)

38. • Generates Both an Electrical and a Magnetic
Field at 27.12 MHz = Stronger Electrical Field
• The amount of electric field to magnetic field
is dependent on:
1) The characteristic of the machine itself
(dependent on the manufacturer).
2) The type of electrodes that we use.

39. Machine circuit
1. Main supply:
it connected with AC mains that gives 220 to 240
V and frequency of 50 cycles /second
2. Transformer:
a) step down transformer whose secondary coil is
connected to the triode valve filament produces
potential of 20 V causes emission of electrons
from the cathode through thermo ionic emission

40. • b) step up transformer secondary coil is connected
to triode valve via oscillator circuit
3. Triode valve: Thermoionic valve which allows
electrons to move in one direction when electric
current flows through the filament from cathode
towards anode provided the grid is connected with
the grid leak resistance.
The grid acts as a regulator to the flow of current-
when positive allows flow of current and when
negative stops the current.

41. • 4.Grid leak resistance: consists of a resistance
coil connected to the grid of triode valve at
one end and the filament of cathode at other
end.
• 5. Oscillator: a stable condensor and oscillator
coil gives high magnitude, high frequency
oscillating currents to the resonator circuit.

42. 6. Ammeter/ Neon lamp: when oscillator
and resonator circuit are tuned it shows
maximum reading / maximum glow. some
machines are auto tuned.
7. part of the body: between two electrodes act
as a dielectric of a condenser.

43. mechanism of production of SWD

44. Principle of Production
44
•This type of high frequency current is
obtained by DISCHARGING a
CONDENSER through an INDUCTANCE
of LOW OHMIC RESISTANCE.

45. production of SWD
• current is produced by rapidly discharging
condenser through an inductance of low
ohmic resistance.
• To charge and discharge condenser
repeatedly oscillator is incorporated in a
valve circuit.
• To produce high frequency current
capacitance and inductance should be
small.

46. • dimension of capacitor
and inductance should be
such that it will allow
electrons to oscillate at a
frequency of 27 . 12 MHz
• the frequency of
oscillator circuit depends
on its electrical size
which is a product of
capacitance (c) and
inductance (L)

47. • To maintain regular oscillation an electric switch
either a thermoionic valve or a transistor is
introduced in the circuit so that current is added in
time with the oscillations.
• this will give low power so a separate amplifier
circuit is needed to increase power to produced
therapeutic frequency.
• power from the mains drawn with the voltage
stepped up around 1000 to 2000 v to operate the
circuit.

48. • Resonator circuit:
it is parallel to the oscillator circuit consists of variable
condenser and inductance coil.
1) Resonator coil: high magnitude current from
oscillator flows in the resonator coil by
electromagnetic induction.
2)variable condenser: helps to bring the two circuits in
resonance
3) Outside the machine we have two electrodes + the
part being treated
4)electrodes: the output of machine is connected to
the electrodes via cable.

49. • The part to be treated included in resonator or
patient circuit coupled inductively to the
oscillator circuit.
• coil in each circuit is placed closed together
forming a transformer.
• the magnetic field generated by oscillator
circuit induces a current in the resonator coil.

50. • energy will be effectively transfered if the two
circuits are in resonance.
• for that the product of capacitance and
inductance in one circuit is same as product of
capacitance and inductance in other.
• the capacity of resonator circuit will changed
because of tissues contributes to the capacity.

51. • Use of variable capacitor is to match the parameters
of each circuit and must be adjusted to bring the
circuits into resonance.
• tunning can be done manually using the ammeter
maximum reading or brightness of light.
• automatically where ammeter drives the tunning
capacitor which itself regulated by the output from
the resonator circuit.
• once tunned the heating of tissues is regulated by
output of the machine.

52. • Depending on the form of SWD you can elicit an
thermal treatment or a non-thermal treatment.
• Heat is generated by the resistance of the passage of
energy through tissues.
• Non-thermal effects are elicited through
repolorization of damaged cells and the
• correction of their dysfunction.
• The depth of penetration of SWD is equal to or
greater than ultrasound and greater than any
infrared modalities

53. Types of units
1) Capacitance (the electric field is more than
the magnetic field) :
Can be achieved by using two space plates
together, or one space plate and a flexible
pad or diplodes.
2) Inductance (the magnetic field is more than
the electric field) :
Can be achieved by using the coil or the drums.

54. Relation of tissue with SWD
• In capacitor or condensor field method the
tissues are influenced by the oscillating
electric field where it act as part of dielectric
of a capacitor for SWD
• in cable or inductothermy method the tissues
are subjected to an oscillating magnetic field
which will induced oscillating current in the
tissues where it act as a part of load of an
inductance.

55. Capacitive Field Diathermy
• •Uses the patient’s tissues as a part of the
circuit
• •The tissues’ electrical resistance produces
heat Selectively heats skin
• • Muscle is heated via conduction from the
adipose
• • Also referred to as “condenser field
diathermy”

57. Induction Field Diathermy cable method
• Places the patient in the electromagnetic field
• Current flowing within the coil produces a
rotating magnetic field which produces eddy
currents in the tissues
• •Eddy currents cause friction that produce
heat
• •Although rare, cables are sometimes used in
place
• Selectively heats muscle

60. • the interaction between the field and the tissues is
affected by a macroscopic property of the tissues
called the complex permittivity.
• it is related with dielectric constant.
• the dielectric constant represents the depolarization
characteristics of a tissue and primarily depends
upon the water content.
• complex permittivity is also a function of the field
frequency and therefore the propagation and
attenuation of the electromagnetic waves are
dependent upon the frequency.

61. Effects of Shortwave on The Molecules
and Ions of Tissues:
 If it is charged  there will be vibration.
 If it is dipole  it will rotate.
 If it is not charged  it won’t be affected.
distortion

62. EFFECTS OF HIGH-FREQUENCY CURRENTS
ON THE TISSUE :-
• The major effect of induced currents of
sufficient intensity at frequencies above 1MHz is
to cause heating.
• High-frequency currents induced in tissue
increases the kinetic energy of molecules of
body & produces heating.

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

64. • The rise in tissue temperature during the
application of SWD depends on a factor
known as the specific absorption rate, (SAR).
• The SAR is the rate at which energy is
absorbed by a known mass of tissue and is
calculated in units of watts/kilogram.
• SAR and heat produced by SWD depends on
the electric properties of the tissue within the
electromagnetic field.

65. • The concentration of electric field will be
highest in the tissues with the high
conductivity.
• Different tissues contain varying proportion of
molecules influencing the conductivity and
hence the SAR.

66. Any living tissue consists of three types of
molecules:
• Charged molecules
• Dipolar molecules
• Non polar molecules
All of three types will influence the
conductivity and hence the heating produced
by SWD

67. SWD produces heat through tissue by:
- Vibration of charged molecules (ions and
certain proteins)
- Rotation of dipolar molecules (water and
some proteins)
- Distortion of non-polar molecules (fat cells)

68. VIBRATION OF IONS :-
• Tissues contain a large amount of ions, which are
charge carriers which move, producing a flow of
current.
• If an electric field is applied first in one direction &
then in other, the ions will be accelerated first one
way then the opposite, colliding with adjacent
molecules to give up some energy to them & so
increasing the total random motions, that is heating.

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

70. DIPOLE ROTATION :-
– Tissues are, of course, largely water. Water
molecules although electrically neutral, they
are polar; i.e. ends of molecule carry small
opposite charges. (because of this they are
sometimes called as dipoles)
– When rapidly reversing fields are applied to
polar molecules they will rotate to and fro.
– This rotational energy disrupts the motion of
adjacent molecules causing more total random
motion & hence heat.

71. 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

72. MOLECULAR DISTORTION :-
• Atoms & molecules which are not charged can also be affected
by a rapidly oscillating electric field in that the paths of their
orbiting electrons are distorted.
• As electric field changes direction one side becomes more
positive & the other more negative, so the position of ‘electron
cloud’ shifts, being attracted to positive & repelled from the
negative side.
• This does not cause motion of molecules but the interaction
with neighbouring molecules lead to more random motion &
some heating.
• little heat is produced by this mechanism explains why plastic
cover of electrodes and leads do not become hot.

73. SWD - Methods
73
1. Capacitor field Method /
condenser Method
2. Inducothermy / Cable Method
Selection of Appropriate methods
Can Influence The Treatment

74. Capacitor (Condenser) Electrodes
The electrodes acts as CAPACITOR
The patient tissues & Insulating material acts as
DIELECTRIC MEDIUM.
Heat production by conversion of ELECTROMAGNETIC
ENERGY
MECHANICAL ENERGY(HEAT)
74

75. Capacitor (Condenser) Electrodes
If the goal of treatment is to
increase tissue extensibility & the
limitation is primarily to capsular
tightness, then capacitor field
method of SWD is the more
appropriate choice.
75

76. Capacitor (Condenser) Electrodes
Create Stronger Electrical Field Than Magnetic
Field
Ions Will Be Attracted Or Repelled Depending
on the Charge of the Pole
76

77. Capacitor (Condenser) Electrodes
Center Has Higher
Current Density
Than Periphery
77

78. Capacitor (Condenser) Electrodes
Patient Is Between
Electrodes and
Becomes Part of
Circuit
78

79. • The Tissue That Offers The Greatest Resistance
To Current Flow Develops The Most Heat
• –Fat Tissue Resists Current Flow
• –Thus Fat Is Heated In An Electrical Field
• –Precaution: electrical field may overheat area
with large fat content

80. Types of Electrodes:
1) Flexible pads
2) Space electrode
3) Monode
4) Minode
5) Diplode
6) Coil
Minode and monode are called “drums”

81. Types of Electrodes in SWD
Flexible pads : consist of metal electrode encased in
rubber and produce an electrostatic field.
81

82. When using them you should insure it is in full
contact.
 We have to wrap it in towel that is 2 cm thick,
less than that could cause a burn, more than
that will affect the amount of heating created
in the body.
 Distance between the electrodes should be
equal the diameter of the electrode, if it is less
than that there will be a shock.

83. Capacitor Electrodes (Pad Electrodes)
Greater Electrical Field
Patient Part of Circuit
Must Have Uniform Contact
(toweling)
Spacing Equal To Cross-
sectional Diameter of Pads
Part To Be Treated Should Be
Centered
83

84. Types of Electrodes in SWD
Air space electrodes or Space plates :
consist of a rigid metal electrode encased
in a Plastic cover  electrostatic field.
84

85. • Two Metal Plates
Surrounded By
Plastic Guard
• Can Be Moved 3cm
Within Guard

86. Air Space Electrodes
 They come in different sizes.
 Can be used in almost every part of the body, but
because they are rigid they will not fit every contour.
 It can be put on either side of the limb, or can be
used in the same side.
 If the electrodes are placed on the same side there
should be a distance between the electrodes,
because if there is no distance there would be a
shock, so we need to put a distance equal the
diameter of the electrode.

87.  Skin-electrode distance: is the distance
between the electrode and the skin.
 If we place two electrodes at the same
distance there will be even heating.
 If we placed one electrode closer to the skin
than the other, the heating won’t be even, it
will be more near the closer electrode.
 If we used a large electrode and a small one
the heating will be more near the small.

89. Sensation Of Heat In
Direct Proportion To
Distance Of Electrode
From Skin
Closer Plate
Generates More
Surface / superficial
Heat
89

90. Types of Electrodes in SWD
The monode: flat, rigid coil encased in
Perspex cover electromagnetic field.
90

91. • One Or More Monopolar Coils Rigidly Fixed In
A Housing Unit
• •May Use More Than One Drum Depending
On Area Treated
• •Penetration
• –Deeper Soft Tissues
• •Toweling Important

93. Types of Electrodes in SWD
• The minode
• The conical rigid coil encased in Perspex cover

94. Types of Electrodes in SWD
The diplode: or drum electrode , consists
of a flat coil electrode encased in a
Perspex cover with two wings
electromagnetic field
94

95. Drum Electrodes
 It is known to heat the deeper tissue without
heating the superficial tissue.
 Penetration to 3cm.
 Make sure that the fat layer of the patient is not
more than 2cm, because the penetration will be
limited and the absorption of heat will accumulate in
the fat layer which might cause a burn.
 The tissues that are heated are blood vessels,
muscles and sweat.

97. Types of Electrodes in SWD
Coil: or cable electrode consists of
a wire with plugs at either end
electromagnetic field.
97

98. Coil or cable
 Usually used for limbs
 Used in two ways:
1) wrapped around the part being treated.
2) Pancake (usually used on the back).
 When wrapping, the space between one turn and
the other should be 5 to 10cm and it is insure by
felt spacers (comes from the manufacturer).
 It is known to heat the deeper tissue without
heating the superficial tissue.

100. continuous SWD
• Capacitance technique- creates a stronger electrical
field rather than a magnetic field.
• The part is placed in-between the electrodes and
becomes part of the circuit.
• Thus, the tissues that provide the most resistance
inhibit the amount of heat transfer to the body. So
areas of the body that have lower amounts of body fat
tend to receive better electrical transmission.
• Capacitance uses air space plates and pad electrodes
to administer treatment.

101. METHODS OF PLACEMENT OF ELECTRODES –
CAPACITOR METHOD
1. COPLANAR METHOD
In this electrodes can
be placed side by side
on the same aspect of
the part, provided that
there is adequate
distance between them.
101

102. Increasing The
Spacing Will Increase
The Depth Of
Penetration. But Will
Decrease The Current
Density
Capacitive Method
Good for Treating
Superficial Soft
Tissues
102

103. • 2. CONTRAPLANAR
METHOD
• In this electrodes
are placed on
opposite sides of
the treatment part.
Most satisfactory
method for deeply
placed structures.
E.g. - Joints

104. 3. CROSSFIRE METHOD
• In this first half of
the treatment is
given with the
electrodes in one
contra planar
position & for the
second half the
electrodes are
repositioned at right
angles to it.

105. 4. MONOPOLAR
METHOD
The active electrode is
placed over the site of
the lesion & the
indifferent electrode is
applied to some
distant part of the
body.
105

106. continuous SWD
• Induction technique- creates a stronger magnetic
field and a lesser electrical field.
• Induction methods create a eddy currents, small
circular fields, within the tissues that cause heat
generation.
• In this method the patient is not part of the circuit
but part of a parallel circuit where the current will
flow through the tissues that provide the least
amount of resistance.
• Induction uses cable and drum electrodes to
distribute treatment.

108. • when the cable is wound like a spring over the
part treated there occur small capacitive
effect between each turn of the coil and large
effect at the ends.
• the center of turn have inductive effect due to
oscillating magnetic field generated by large
current at the center of the cable.
• electromagnetic induction of electric current
at right angle to the direction of magnetic
field.

109. • Two Arrangements:
Pancake Coils
Wraparound Coils
• Toweling Is Essential.
• Pancake Coil Must Have 6” in
Center and 5-10cm Spacing Between
Turns

110. 110

111. • insulated drum contains the coil of the cable .
• flat helix called magnaplode and grid arrangement -
the ends of the cable are connected to the machine.
center part is used to treat large and flat areas.
• double helix where eddy currents produced in the
tissues lying between the two helices. Heating effect
in superficial area with low impedance.
• cable used with one condenser electrode in case of
deformed joints.

112. FACTORS INFLUENCE FIELD DISTRIBUTION IN
S.W.D
• 1- Spacing:
• It allows the lines of force in the electrostatic
field to diverge before entering the tissues.
• This prevents concentration of heat in the
super-facial tissues and ensures more heating
through the part.

113. • Spacing provided by:
• 1- wrapping flexible pads in towel.
• 2-flat felt spacing pads between pad
electrode and skin.
• 3-air when using space plates.

114. • a- Normal spacing
 even field
distribution.
• b- Increased
spacing  deep
field
concentration.
• c- Decreased
spacing 
superficial
concentration

115. • About 4 cm distance will give heating of
the deep tissues.
• Conversely the minimum skin electrode
distance is about 2 cm, will give
superficial heating.
• Note: the spacing refers to the distance of the
metal electrode, not the plastic cover, from
the skin.

116. Position of electrode relative to the tissue
- Electrode parallel to skin surface
Uniform field
- The distance between electrodes less than
the combined skin electrode distances
Most of field passes through air space
- Electrode isn't parallel to skin surface
Superficial heat under closest part of
electrode

117. • 2.Electrode size :
• If the electrodes are too small than the
diameter of treated part line of force will be
concentrated superficially.
• -If the electrodes are markedly larger the
line of force will be lost in the air.
• Ideally, the electrodes should be slight larger
than the area treated.

118. When Choosing The Size of Electrode
We Should Consider:
1) The size of the area treated.
2) Location of the area to be treated.
3) The depth of the targeting tissue.
4) Treatment goals.
5) The contraindications.

119. 119

120. • 3. Metal
• metal causes the lines of force to
concentrate on the metal

121. • 4. Air in cavities:
• As sinuses or uterus, the lines of force deviate
to avoid air as it offers a high resistance.
• As a result only the sides of air cavity will be
heated.

123. Important Rule
 Chronic cases  you can treat it with thermal
or non thermal shortwave.
 Acute  only use non thermal shortwave

124. Advantages of Shortwave
 The deep penetration, it goes deep to 5cm.
 You can use it while attending to another
patient, which allows you to manage your time
in the clinic.
 It covers large areas.
 It can heat the deeper tissue without heating
the superficial tissue
 It can be used with sensitive tissues because it
doesn’t need to be in contact with the treated
tissue.

125. Uses
Thermal Effects
Deep heat
Increased blood flow
Increased cell metabolism
Increased tissue extensibility
Muscular relaxation
Possible changes in enzyme
reactions
125
Non-thermal Effects
•Edema reduction
•Lymphedema
reduction
•Superficial wound
healing
•Treatment of
venous stasis ulcers

126. Physiologic Responses To SWD
Tissue Temperature Increase
Increased Blood Flow (Vasodilatation)
Increased Venous and Lymphatic Flow
Increased Metabolism
Changes In Physical Properties of Tissues
Muscle Relaxation -
Analgesia -
126

127. Indications of SWD - A condition that
could benefit from a specific modality.
• Disorders of Musculoskeletal System:
Low back pain, O.A., R.A., Sprain, Strain,
Muscle & Tendon tear, Capsule lesion, Joint
stiffness, Hematomas, frozen shoulder,
myelegia, traumatic arthritis, ankylosing
spondylitis, Chronic Inflammatory
Conditions;
• Tenosynovitis, Bursitis, Synovitis, Sinusitis,
Fibrositis, Myositis)

128. 2. Sports injury:
muscular strain of rectus femoris,
harmstrings, tensor facia lata etc.., contusion
of thorax.
3. Surgical conditins:
infected surgical incisions, stiched abcess

129. • 4. ENT:
chronic sinusitis, chronic otitis media
5. non specific pelvic inflammatory diseases.
6. Chest disorders:
To relieve muscle spasm in some forms of
bronchial asthma.
Sub-acute and chronic bronchitis.
7 - Neurological disorders:
Neuritis, Sciatica.

130. Contraindications - A condition that could be
adversely affected if a particular modality is used.
Metal implants or metal jewelry (be aware of body
piercings) – Concentration of the field.
Cardiac pacemakers – Interference with function
Ischemic areas – The inability of the circulation to
disperse heat could result in high temperature – Burns.
130

131. • Perspiration and moist dressings :
The water collects and concentrates the
heat.
• Tendency to hemorrhage, including
menstruation – Increase vasodilatation,
prolong hemorrhage.
• Pregnancy – Miscarriage
• Hyperpyrexia

132. • Sensory loss / Impaired thermal sensation
• Cancer / Malignant tissues – Accelerate the
rate of growth & Metastasis
• Active TUBERCULOSIS – Increase the rate of
development of the infection.
• Recent Radiotherapy – Skin sensation &
Circulation may be decreased.

133. • Dermatological Conditions – Will exacerbate
• Severe Cardiac conditions – Greater demand
of Cardiac output.
• DVT

134. Areas of particular sensitivity:
Epiphysis plates in children
The genitals
Sites of infection
The abdomen with an implanted
intrauterine device (IUD)
The eyes and face
Application through the skull
134

135. Therapeutic Effects of SWD
135
1- Pain relief:
Stimulation of Sensory heat receptors – Pain Gate
Mechanism.
2-Muscle spasm
Heating Secondary Afferent muscle spindle –
Inhibitory influence to motor pool.
3- Inflammation : Assists in removal of cellular debris
and toxins.
Nonthermal: Alters diffusion rate across the cell membrane
Thermal: Increases intramuscular metabolism

136. Therapeutic Effects of SWD
136
4- Accelerate wound healing : by increase cutaneous
circulation, Vasodilatation increases:
Blood flow
Capillary filtration
Capillary pressure
Oxygen perfusion
5- Infection : increase circulation and increase white
blood cells and antibodies – Reinforcing body’s
normal defense mechanism.
6- Fibrosis : increase extensibility of fibrous tissues
such as tendons, joint capsule and scars. Alters
collagen properties, allowing it to elongate.

137. Dangers and Precautions in SWD
1- Burn -
 Heat burn caused by SWD so word 'burn' use to warn
the patient for this possible danger.
 burn occur if the patient is unaware of the heat
mild case tissues are not destroyed but a bright red
patch is seen and blister will occur.
in severe case coagulation occur followed by destruction
of tissues results in white patch surrounded by a reddened
area of inflammation.
damage should be visible on removal of electrodes after
complition of the treatment.
137

138. • burns may occur due to
1) concentration of electric field
2) leads touching the skin
3) use of exess current
4) hypersensitivity of the skin
5) impaired blood flow

139. 1) concentration of electric field:
this causes overheating of the tissues in the
affected area. if in the field a material of high
dielectric constant is present like metal or
moisture which will concentrate the electric
field and burn occur.
it depends on the size, shape and orientation
of the metal with respect to the field.

140. • all metals are relatively low resistance conductors
and even enclosed in plastic will provide a low
impedence pathway.
• e.g. armpiece of spectacles, metal in clothing-
hooks, zip fastners, buckles, earings, ornaments,
keys, embroidary, etc.
• a long slender pointed piece of metal like a key lies
parallel to the line of force of the field touching the
skin at its point provide a good conductor
concentrating the current at contact point results in
burn due to maximum heating.

141. • if a person is in an electromagnetic field
touches any conductor connected to the earth
provide a route to ground for a charge to
induced in the tissues. (earth shock)
• Metal implants: metal embedded in the
tissues in case of fixation of fracture, metal
arthroplasty or accidently embedded in the
tissues can cause burn at the junction of the
metal with the tissues depending upon the
position with electric field.

142. • burn occurs due to concentration of field rather than heating
of the metal.
• if metal implant lies parallel to the line of field it provides
pathway of low impedence for a considerable distance and it
liable to cause serious concentration of field.
• if it lies across the field the easier pathway is provided for a
short distance and concentration of field is less so there is less
effect.

143. • large wired dental splints, contact lences,
spects, hearing aids may be a risk when SWD
is given for sinus.
• IUCD considered as hazard during treatment
of the pelvis and lower lumber region in
female.

144. • Moisture: if the area being treated is damp
from prespiration or damp towels are used
with the cable a scald is caused by moist heat.
• if moisture is not localised it will not
concentrate the field but may be overheated
and skin damage occur.

145. • 2) Leads touching the skin:
if a lead approaches close to the patient's
body heat is produced in the area can cause
burn.
if spacing between two electrodes is
inedequate concentration of field occurs at
the electrode nearer to the skin results in
burn.

146. • 3). exess current: the patient's sensation is the
only indicator of the intensity of the
application and burn occur due to
• patient does not understand the high
intensity of current
• defective thermal cutaneous sensation
• fall asleep during treatment session
• unconcious patient

147. • if the intensity of machine increase quickly in
the begining of the treatment it will reach at
dangerous level and failure to reduce the
current immidiately when heat becomes
intense results in burn.
• Overdose: causes increase in symptoms
especially pain and mostely occur in acute
inflammation within a confined area. it is a
indicator to reduce intensity of application.

148. • 4). Hyper sensitive skin:
due to x-ray therapy or recent use of liniment
skin become hypersensitive where SWD dose
which is normally be safe may cause damage
to the tissues.

149. • 5) Impaired blood flow:
 the blood circulating through the tissues
normally dissipates the heat and prevent
exessive rise of temperature. due to impaired
blood flow this is not possible result in heat at
the area to be treated.
Heat accelerates chemical changes including
metabolic process in the tissues which
increases the demand for oxygen.

150.  due to impaired arterial supply to the tissues
the demand for oxygen is not met and
gangrene is liable to occur.

151. Burns can be avoided by
 Test of thermal skin sensation.
 Aware patient about mild comfortable warmth effect of
SWD
 Taking care during application over a bony prominence.
 Never apply SWD over clothing.
 Do not apply SWD directly to an area of impaired arterial
blood supply.
 Making sure that the skin is dry.
 If you apply over two skin surfaces in contact, they must be
separated by absorbent material towel.

152. • Making sure that the leads from the machine are
not touching or within 25 mm electromagnetic
field around the lead.
• Making sure that there is adequate spacing
between the electrodes and the skin.
• Remove metal, hearing aids, contact lences,
orthoses .
• Allowing 2 or 3 minutes on each intensity setting
maximum heat.

153. Dangers and Precautions in SWD
2- Electric shock -
it can occur if
 contact is made with the appratus circuit while switch is
on.
if any metal lies in the electromagnetic field is touched.
if corner of machine or electrodes is touched when
machine is on sparking may occur.
153

154. Electric shock can be avoided by:
• -Not increasing intensity unless the leads and electrodes are
connected to machine.
• -Making sure that the machine is earthed.
• -Not touching the machine, electrodes and leads when
machine is on.
• -Making sure that there is no metal within the range of
300mm.
• patient should be treated on wooden treatment table
without metal inside.
• -If the patient is wearing a hearing aid or electrophysiologic
orthoses  switch it off.

155. Dangers and Precautions in SWD
3.Synthetic Material
These do not absorb moisture as readily as normal
materials
They ignite more easily
The material may alter the field either by
absorbtion of energy or concentrating the field.
can be avoided by
ask patient to wear cotton clothes or remove the
clothes during the treatment
155

156. Dangers and Precautions in SWD
4. Giddiness
electric current applied to the head may cause giddiness due to its
effect on semicircular canals
can be avoided by
proper positioning of the patient with the head in a horizontal or erect
position.
5. Obese Patients
Fat layers more readily heated than the muscles
Fat absorbing power 8 times that absorbed in muscle.
156

157. • 6. Pregnancy:
• exposure in early pregnancy especially in 1st
trimester theremay be malformation in foetus
occur.
• can be avoided by
• restrict exposure to patient and therapist keep
the distance from the SWD machine about 1m
for contineous SWD, 0.5 for pulsed SWD.

158. • 6. Damage to the equipment
• the action of cardiac pacemakers, hearing aids and
other electronic devices( mobile, watch, calculator)
may be affected by disturbances set up by SWD.
• Leads may be damaged by overheating if they are
allowed to make contact with the conductor or a
break in the continuety of the wire.
• crack in the electrode within the rubber insulation
results in sparking and overheating.

159. can be avoided by
• remove all electronic equipment from the
vicinity of SWD field.
• leas should not touch or cross eachother.
• cable wire of main supply and output circuit
must be checked frequently.
• malleable electrodes should be checked for
any damage.

160. Continuous short wave diathermy
Increases tissue temperature
Increased risk of burns
Pulsed short wave diathermy
May or may not increase temperature
Pulses allow for increased treatment intensity and duration
Not the same as “non-thermal”
160

161. • Continuous SWD is of benefit in treatment of many
conditions such as osteoarthritis where reduction of
pain & increase in circulation are desirable.
• But one major limitation in use of SWD is that its
thermal effect is greatest in fatty tissues & this limits
the amount of energy which can be applied before
thermal damage occurs.
• Beneficial effects can be produced when sub-thermal
dose of shortwave is applied.

162. Continuous vs Pulsed SWD

163. Pulsed SWD (PSWD)
 A number of machine now exists which produce
electromagnetic energy with the aim of stimulating
tissue repair in a non-thermal way.
 Most operate at the radio frequency of 27.12 MHz,
which is same as CSWD & named
• PULSED SWD
• PULSED ELECTROMAGNETIC ENERGY (PEME)
• PULSED ELECTROMAGNETIC FIELD (PEMF)
• PULSED ELECTROMAGNETIC ENERGY TREATMENT
(PEMET).

164. When using the pulsed shortwave, there are
certain parameters that we need to know:
• Pulse width: measured by micro seconds.
• Pulse frequency: how many pulses we have
per second measured by Hz or pulses per
second (PPS)
• Peak power output: in watts, usually is a set
value that is determined by the manufacturer.
• Mean power output: is variable and is
determined by factors such as the pulse width
and the pulse frequency.

165. Pulsed SWD
By incorporating a timing circuit , the output can be
turned on & off allowing bursts of Oscillations.
Off-Time Longer Than On-Time
Low Mean Power Output
Uses Drum Electrode
Some machines give fixed – length pulses (65 or
400µsec)
165

166. Pulsed SWD
-The pulse frequency range is from 15 to 800 Hz.
-The maximum intensity is 1000 watts.
-The pulse duration is constant at 0.4 ms in square
pulse.
-The advantage of pulsed S.W.D. is that a very high
intensity of power can be administered with minimal
effect.
166

167. Pulsed SWD
167

168. PSWD - Physiological Effects
• effect is by thermal and non thermal mechanism.
• Total average power is high due to high peak power
and frequency - heat is produced.(effect of heat)
• 1-Increases the growth & activity of cells in the
injured region and there by repair
• 2-Reabsorption of hematoma .
• 3-Reduces swelling & Inflammation
• 4-Increases rate of fibrin deposition & orientation
• 5-Increases collagen deposition & organization
• 6-Increase nerve growth & repair.
• 7- pain control

169. Indications
• 1- Acute Sprains.
• 2- Contusions.
• 3- Acute Haematoma.
• 4- Bursitis.
• 5- Sinusitis.
• 6-Synovitis
• 7-Sports Injuries
• 8-Superficial Ulcers, incisional wound, burn related
injuries
• 9- Neurogenic Pain (Phantom Pain , Causalgia )
nerve injuries

170. Contraindications
• low average power -little danger of burn due to
concentration of field by metal or moisture
• otherwise all the contraindication of SWD is applicable.
• 1- Cardiac Pacemakers.
• 2- High fever.
• 3- Precancerous Tissues and malignant lesions
• 4- Metal in the area , including implants if thermal effect is
required.
• 5-Pregnant Women
• 6-Impaired sensation
• 7-Uncooperative / Unconscious patients
• 8-Tuberculosis
• 9-Hearing aids and other electronic equipments

171. PSWD - Therapeutic Effects
• 1- Decrease of pain & Swelling – Tissue
trauma.
• 2- Acceleration of Inflammatory & Healing
Process
• 3- Relaxation of Muscle Spasm
• 4- Decreases the rate of hematoma formation
• 5- Superficial ulcers are treated successfully –
Bed sores
• 6- Acceleration of bone growth

172. PSWD - Advantages
1-Effective in treatment of post
traumatic & Infective conditions
2-Often used in conditions where
continuous SWD is contraindicated.
172

173. Dosage of PSWD
• Based on principle of lower dose for acute
conditions and higer dose for chronic
conditions.
• can be applied for longer duration, high
frequency and mean power output.
• 25 min of treatment is effective

174. Dosage of Continuous SWD
• Patient Sensation Provides Basis For
Recommendations Of Continuous SWD
depends on perception of the patient
clinical experience of the therapist
15 - 20 min require for vascular adjustments
to occur so treatment duration is of 20 - 30
mins.

175. • Dose I (Lowest) - No Sensation of Heat
• Dose II (Low) - Mild Heating Sensation
• Dose III (Medium) - Moderate or
Pleasant Heating Sensation
• Dose IV (Heavy) -Vigorous Heating
Within Pain Threshold
• When increasing the intensity wait 2-3
minutes to allow the temperature to build in
the tissue before moving to the next stage.

176. How To Set The Parameters When
Using Pulsed Shortwave
If we want to set the pulsed shortwave:
 In acute conditions, the mean power output should
be 3 and the treatment time is 10 minutes.
 In sub acute, the mean power output should be 2-5
and the treatment time 10 to 15 minutes.
 In chronic conditions, the mean power output is
from 5-7 and the treatment can go up to 30
minutes.

177. Mean power output = peak pulse power /
percentage of on time
On time = pulse duration / pulse period
Pulse period = peak pulse power / pulse repetition
rate

178. When Using Thermal Shortwave
1) Adjust the machine.
2) Ask the patient.
3) If the temperature is too hot decrease it.
4) The patient is not feeling heat increase it.
• Dosage with the continuous shortwave depending
on the thermal sensation reported from the
patient.
• Use your clinical judgment in administering the
dosage .

179. Frequency of The treatment
 Daily or every other day.
 Depends on the patient’s response.
 If the condition is very acute, daily treatment will
give better results.
 Chronic condition, every other day treatment.
 If it didn’t improve  do it everyday.

180. TECHNIQUE OF APPLICATION
• Determine the case & side/site.
• Receiving the patient
• HISTORY
- name
- father’s & mother’s name
- age & occupation
- address
- chief complains & duration
- present, past, family, social & occupational history
- contraindications
- treatment history & investigations

181. PREPARATION OF TRAY
• Two test tubes for skin test
- one with hot water
- one with cold water
• Neon tube to ensure the machine is working.
• Cotton towels or felt pads for spacing.
• Pillows
• Sand bags
• Straps

182. • Positioning of patient
Put the patient in a comfortable position and well
support, allow the area to be treated to be
completely uncovered.
• Checking for general & local contraindications
• Inspection & palpation of part
• Checking skin sensation
• Ensure there is no metal (jewellery or hairpin) within
300mm of treatment area. Remove mobile, coins,
belt, metal instruments, etc.
PREPARATION OF PATIENT

183. • Instruction to patient
 Explain the procedure and feeling to the
patient, tell immediately on uncomfortable
heat feeling.
 Not to move, sleep or touch cable or any
other thing
 If the machine has a patient safety switch
instruct the patient to switch the machine
off if he feel more heat.

184. PREPARATION OF APPARATUS
• Shortwave machine with chosen electrodes
and its test tube to ensure the machine is
working.

185. • Check insulation of wires & cable
• Check plugs, socket, fuse & all knobs to be
placed at zero
• Testing of apparatus
• Positioning of electrodes & adequate spacing

186. • If using space electrodes adjust the distance
according to the concentration needed.
• If using flexible pad electrodes, wrap them
in several layers of toweling or place them
between felt pads to ensure the required
amount of spacing.

187. • switch the power on.
–Switch the intensity on and wait 2-3
minutes on the minimum intensity and ask
the patient about her/his feeling of heat.
–Adjust the timer to the required treatment
time.
–Intensity to be increased & do tuning

188. TERMINATION
• After treatment time has finished, turn the
intensity switch to zero and remove the
electrodes.
• Switch off machine
• Inspect part for erythema or any other adverse
effects
• Palpate for any pain
• ask the patient to stay few minutes for rest and
to regain to normal temperature.
• Record patient’s name, condition, dosage, type
of pad, spacing & duration.

189. PRACTICAL POINT OF VIEW
• If duration of condition is up to 10th day then it is
acute condition.
• If duration of condition is between 2 weeks to 6
months, then it is subacute condition & if it is above
6 months then it is a chronic condition.
• Spacing disc electrodes pad electrodes
narrow (for acute case) 1 inch 2 to 4 folds
medium (for subacute) 2 inch 4 to 6 folds
wide (for chronic case) 3 inch 6 to 8 folds
• Duration & Dosage
acute case - 10 to 15 minutes mild thermal
subacute case - 15 to 20 minutes subthermal
chronic case - 20 to 30 minutes thermal

190. Technique of Application
1-Application using two flexible pads or space
plates:
A- The electrodes should be slightly larger than the
area treated and spaced from the skin by
approximately 25 mm.
B- To concentrate heat on one aspect of the part the
electrode should be unequal in size (smaller one
placed over the area where concentration of heat is
required).
190

192. Technique of Application
C- Coplanar application to treat structures on one aspect of
the body.
The distance between adjacent ends (x) must be greater
than the sum of skin electrode distance (A+B) otherwise
the line of force will pass directly between electrodes
rather than tissues.
192

193. Technique of Application
D- Application using a coil electrode:
1- The coil wound evenly firmly
2- Pancake application
193

194. Technique of Application
E- Application using diplode:
Adjust wings of diplode parallel to the skin of the treated
area, electromagnetic field will produce.
194

195. Technique of Application
F- Applications to two limbs:
Two flexible pads, two space plates or flexible pad with a
space plate are used. It is essential to put a cotton towel
between the two limbs to absorb any perspiration.
195

196. Technique of Application
G- Cross-fire application:
For the treatment of sinuses, space plates positioned
diagonally, after half of treatment time the positions are
alternate. This ensures that all aspects of the sinus
membrane are heated. Care must be taken to avoid direct
placement over the eye.
196

197. Treatment Time
Most Typically SWD Treatments Last For 10-20-
30 Minutes
Remember As Skin Temperature Rises
Resistance Falls
197

199. 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

200. References
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.