short and pulse wave diathermy

1. Quratulain Mughal
Batch IV
Doctor of physical therapy
Isra university
SHORT WAVE
DIATHERMY

2. DIATHERMY
 It is a Greek word meaning "through heating".
TYPES OF DIATHERMY
1. Short wave diathermy
2. Pulsed wave diathermy
3. Microwave diathermy

3. SHORT WAVE DIATHERMY
 It provides the deepest heat.
 It is the use of high frequency electromagnetic waves.
FREQUENCY:107 to108 Hz
WAVELENGHT: between 3 and 30m to generate heat
in the body tissues.

4. THERAPEUTICALLY USED
FREQUENCIES &WAVELENGTHS:
 27.12 MHz and 11m(commonly)
 40.68MHz and 7.5m and 13.56MHz and 22m (less common)

5. PRINCIPLES
 It is not possible to produce high frequency currents by some
mechanical device which produces sufficient rapid movements.
 This type of current can only be produced by discharging a
condenser through an inductance of low ohmic resistance.
 If a current of very high frequency is required, the capacitance
and inductance should be small.
 If a current of low frequency is required the capacitance and
inductance should be large.

6. CONSTRUCTION
 The system is consists of two circuits:
1.The machine circuits
2.The patient circuit

10. THE MACHINE CIRCUIT
 It consist of two transformers, whose primary coil are
connected to source ofAC.
 One is step-down transformer and its secondary coil supplies
current to the filament heating circuit of triode valve.
 The other is set-up transformer and connected to anode
circuit.
 Anode circuit carries the current produced by valve.
 Here it consists of triode valve and oscillator circuit.
 Oscillator circuit consists of condenser and inductor or oscillator
coil.

11. CONTIN....
 Current of different frequencies are obtained by
selecting suitable condensers and inductances.
 To produce a current of high frequency the capacitances
and inductance used must be small and is made to charge
and discharge repeatedly and for obtaining this an
Oscillator is incorporated in to machine circuit along
with valve circuit.
 Another coil AB lie close to oscillator coil and had one
end connected to the grid of the valve and other through
grid leak resistance to the filament.

12. THE PATIENT CIRCUIT
 Also known as resonator circuit.
 It‘s a coupled to machine circuit by a inductor coil lying
close to oscillator coil and also consist variable
condenser which is usually in parallel to patient
terminal.
 A matching high frequency current is produced in the
resonator circuit by electro magnetic induction.
 For this to happen the oscillator and resonator circuit
must be in resonance with each other,Which requires
that the product of inductance and capacitance must be
the same for both circuits.

13. WORKING
 TheAC from main passes through primary coils of the
transformers and EMF is induced in secondary coils.
 An EMF of 20-25volt is set-up in secondary coil of set-down
transformer and produces currents through filament of the
valve.
 The filament is heated and thermionic emission takes place
and current flows through valve.
 The EMF of about 4000volts is induced in the secondary coil
of set-up transformer and provided that anode of valve is
positive and filament is negative, current flows in Anode
circuit.

14. CONTIN…..
 The electrons flows to filament through anode valve, through
oscillator coil in direction C and D and to transformer back
to filament.
 The electron form in CD will induce EMF in coil AB in
direction that electrons will move to grid of valve making it
negative thus blocking the flow of electrons from filament.
 This will lead to dying of current in anode circuit.
 This reduction in current will lead to self-induced EMF.
 According to Lenz law, this EMF will try to prevent fall in
current by offering resistance to flow of current.

15. CONTIN…..
 This will charge condenser X(positive) andY(negative)
polarity opposite to earlier one.
 Now when self-induced EMF totally dies away, condensers
again discharges through oscillator coil, but in opposite
direction(D to C).
 Flow of current from D to C induce an EMF in AB such that
electrons move fromA to B and grid loses its negative charge
and anode current flows again.
 This sequence continues and each time condenser charges
and discharges through oscillator circuit leading to
production of high frequency current(SWD).

16. GRID LEAK
 When the current flows across the valve some electrons are
caught on the grid and grid leak is provided to enable these
electrons to escape back to the filament.
 The resonator coil lies within the varying magnetic field set
up around the oscillatory coil, so provided that two circuit
are in resonance high frequency current in induced in it.
 The current is similar to that in the oscillator circuit and is
supplied to patient.

17. METHODS OF APPLICATION
 The transfer of electrical energy to the patient tissues occurs
either by electrostatic field or by electromagnetic field.
1. Condenser/capacitor field method
2. Cable method

18. CONTINUE….
 When SWD is applied by the condenser field method, the
electrodes and the patients tissues form a capacitor.
 The capacitance of such a capacitor depends upon:
1. Size of electrodes
2. Distance b/w electrodes
3. Tissues b/w electrodes
 When the SWD is applied by the cable method, the cable and
the patients tissues forms an inductance, the valve of which varies
according to its arrangement.
 Consequently, either the capacitance or inductance of the pt’s
circuit is varied at each treatment, and so a variable condenser is
incorporated in the patients circuit to compensate for this.

19. CAPACITOR FIELD METHOD
 The electrodes are placed on each side of the part of the body
treated.
 The electrodes are separated by the skin by means of an insulating
material.
 The electrodes act as the plates of the capacitor, while the pts
tissue together with the insulating material which separate them
from the electrodes for the dielectric.
 When the current is applied, rapidly alternating charges are setup
on the electrodes & gives rise to a rapidly alternating electric field
b/w them.
 The electric field also influences the material which lies within it.

20. EFFECT OF ELECTRIC FIELD ON
CONDUCTORS, INSULATORS AND
ELECTROLYTES
 As we know, conductors are the substances in which
electrons can easily be displaced from their atoms.
 When such a material lies within a varying electric field,
there is rapid oscillation of electrons & heat is produced.
 An insulator is substance in which the electrons are so firmly
held by the central nuclei that they can’t be easily displaced &
results in the distortion of molecules when varying electric
field is applied.

21. CONTINUE….
 An electrolyte is a substance which contains ions & when a
varying eclectic field is applied, the ions tends to move from
one direction to the other.
 Electrolytes also contain dipoles which contain two
oppositely charged ions, when a varying electric field is
applied, they rotates their direction.
 These dipoles are electrically neutral, but one end bears
positive & the other a negative charge.
 As a result of electric field they rotate themselves & come in
an alignment with the electrodes.

22. EFFECTS OF ELECTRIC FIELD ON
DIELECTRIC CONSTANTS OF THE BODY
TISSUE
 The dielectric constant of the various tissues differ
considerably.
 The tissues of low impedance such as blood & muscles have
higher dielectric constants.
 The tissues of high impedance such as fibrous tissues & fat
have low dielectric constant.

23. SELECTION OR PLACEMENT OF
ELECTRODES
 Types of electrodes
 Size of electrodes
 Spacing of electrodes
 Positioning of electrodes
(coplanar, contraplanar,
Monoplanar,crossfire)

24. CABLE METHOD OR INDUCTOTHERMY
 In this method a thick, insulated cable is used for treatment
purposes.
 Electric field or magnetic field or both are achieved by the
use of cable method.
 THE ELECTROSTATIC FIELD: is produced at the end of
the cable & effects are similar when the current is applied by
a condenser method.
 THE MAGNETIC FIELD : varies as the current oscillates &
an EMF is produced by electromagnetic induction.

25. CONTINUE….
 Thus, the electric field influences the material that lies b/w
the plates; this causes the oscillation of the ion, distortion of
the molecules & rotation of dipoles.
 This causes production of heat in the tissues by electric filed
of SWD, which is the primary function of SWD.
 The heat production is an accordance with joule’s law
(Q=I2 RT) , but depends upon the distribution of the electric
field.

28. PHYSIOLGICAL EFFECTS
 Metabolism of the body
 Effects due to increased blood supply
 Effects of heat on muscular tissue
 Effects of heat on sweat glands

29. THERAPEUTIC EFFECTS
 On inflammation
 Bacterial infections
 Relief pain
 Muscle tissue
 Traumatic conditions
 Reduction healing time

30. DANGERS
1. Burns
• Concentration of electric field
• Excess current
• Impaired blood flow
• Hypersensitive skin
• Leads touching skin
2. Scalds
3. Electric shock
4. Overdose
5. Precipitation of gangrene
6. Faintness
7. Giddiness
8. Dangers to hearing aids or cardiac pacemakers
9. Dangers to other equipments

31. PULSED SHORT WAVE DIATHERMY
 Also referred as PULSED ELECTROMAGNETIC ENERGY
OR FIELD, DIAPULSE, etc.
 It is created by simply interrupting the output of continuous
SWD at regular intervals.
 It was invented in 1930s but became popular only after 1950s
 FREQUENCY: 27.12MHz
 PULSE FREQUENCY: 25-600pps
 PULSEWIDTH: 20-40ms mostly 65ms is used.
 TREATMENT DURATION: 15-60min
 The heat develop in he tissues is dispersed by the circulation
and treatment is thus referred as nonthermal treatment.

32. THERAPEUTIC EFFECTS
 the reabsorption of hematoma
 cellular activity
 repair process
 inflammation
 swelling

33. REFERENCE
 JOGMOHAN SINGH: MANUAL OF PRACTICAL
ELECTROTHERAPY

34. CONTRAINDICATIONS
 Open wound or hemorrhage
 Metal implants or metal jewelry
 Sensory loss
 Pregnancy
 Deep X ray
 Tumors
 Menstruation
 Venous thrombosis or thrombophlebitis
 Arterial disease
 Children
 MR pts
 Unconscious pt
 Epileptic pts