SWD FINAL.pptx

SHORTWAVE DIATHERMY
PRESENTED BY
GROUP 1
MPT 2ND SEMESTER
COURSE: MPT19206 ELECTRODIAGNOSIS AND PHYSICAL
AGENTS
Saturday, 27 May 2023

INTRODUCTION
The term ‘diathermy’ is a Greek word
‘dia’ means ‘Through’
‘thermy’ means ‘heat’
Diathermy is applied using electromagnetic waves that produce heat, but are non
ionizing.
Short wave diathermy used for therapeutic purpose posses :
Frequency - 27.12 MHz
Wavelength - 11 m.
Short wave energy can be delivered via a continuous mode or a pulsed mode.
The continuous short wave is delivered by capacitive or inductive methods and
pulsed SWD is of same frequency & delivered in the form of pulses.

PRODUCTION
The shortwave diathermy consists of 2 circuits:
A. Oscillator circuit
B. Patient or Resonator circuit
COMPONENTS OF SWD:
A. Oscillator/ Machine circuit
It consists of:
Main supply
Triode valve
Grid leak circuit
Oscillator coil Saturday, 27 May 2023

B. Patient / Resonator circuit
It consists of:
Resonator coil- The high frequency and high magnitude current from the oscillator
flows in the resonator coil by EMI.
Resonator condenser- It is a variable condenser , used to store electric charge. It is
used for tuning both the circuits to obtain maximum heating of tissues. It consists of
two metal plates separated by a insulator called dielectric. If the plates are given two
opposite static charges, lines of forces concentrate between the plates and electric
field is created.
Electrodes- Output of SWD machine is connected to two types electrodes; Pad or
Disc electrode
Ammeter- It shows maximum reading when both circuit resonate.
Tissues Saturday, 27 May 2023

WORKING:
The step up and step down transformer is connected to power supply.
The current passing through the primary coil of step-down transformer induces
EMF in secondary coil, which produces current via cathode filament of the triode
valve.
THERMIONIC EFFECT – Once the cathode filament receives current from
secondary coil, the cathode omits electrons.
Similarly, the primary coil of the step up transformer induces EMF in the secondary
coil, which is connected to anode and now, anode is capable of conducting current.
The cathode filament releases electrons, which passes through grid to the anode.
The grid is neutrally charged now.

• The electrons flow from cathode to anode and passes via oscillator coil (CD),
which induces EMF in coil AB from B to A..
• The end of coil AB is connected to grid of triode valve, which accepts the
electrons from coil AB and gets negatively charged, thus blocking the flow of
electrons from cathode filament.
• Now the condenser gets depolarized.
• When the current flows in oscillating coil from D to C EMF is induced from
A to B and the Grid loses the negative charge and starts conducting the
current.

Resonator circuit is coupled to the patient circuit by inductors and a high
frequency current is produced in it by electromagnetic induction.
When both the circuits are in resonance, maximum current will flow in
resonator circuit and for this product of conductance and inductance must be
the same for both the circuits.
SWD current is obtained by discharging the condenser. The capacitor
discharges when accumulated charges are allowed to flow off the plates to
provide the high frequency current.
A condenser is made to charge and discharge regularly.

PHYSIOLOGICAL RESPONSES TO SHORT WAVE
DIATHERMY
THERMAL EFFECTS:
Not capable of producing depolarization and contraction of skeletal muscles.
-Wavelength too short in duration.

The primary effects of diathermy are those of heat in general.
-Rise in tissue temperature.
-Increased blood flow.
-Dilation of the blood vessels.
-Increased filtration and diffusion through different membranes.
-Increased tissue metabolic rate.
-Changes in enzyme reactions.
-Alterations in the physical properties of fibrous tissues.
-Decreases joint stiffness.
-Certain degree of muscle relaxation.
-Analgesia.

Diathermy heating doses are not precisely controlled thus the amount of
heating cannot be
-accurately measured.
Heating = Current density2 x Resistance.

NON-THERMAL EFFECTS:
Pulsed SWD used to treat soft tissue injuries and wounds.
Related to Depolarization of damaged cells
-Loss of cell division
-Loss of proliferation
-Loss of regenerative capabilities.
Repolarization corrects cell dysfunction.
Sodium pump reactivation ( allows the cell to regain normal ionic balance).

THERAPEUTIC EFFECTS OF SHORT WAVE DIATHERMY
 Effects on Inflammation
Effects in bacterial infections
Relief of Pain
Effects on muscle tissue
Traumatic conditions
Reducing healing time

EFFECTS ON INFLAMMATION
The dilatation of arterioles and capillaries results in an
increased flow of blood to the area which increases supply of
oxygen and nutritive material. This increased flow of blood
enhances the supply of more antibodies and white blood cells.
The dilatation of capillaries increases the exudation of fluid
into the tissues and this is followed by increased absorption
which along with the increased flow of blood through the area
assists in the removal of waste products.

EFFECTS IN BACTERIAL INFECTIONS
SWD increases the circulation of blood which increases the
number of WBC and antibodies in the affected region which
help in removing infection.

RELIEF OF PAIN
The mechanism of pain relief is explained by:
Sedative effect due to mild degree of heating
Removal of noxious chemical (waste products of metabolism)
Counter irritation effect due to superficial heating which block
the pain transmission at pain gate.
Relief of pain also accompanies resolution of inflammation by
SWD.

EFFECTS ON MUSCLE TISSUE
Induction Of Muscle Relaxation:
When SWD applied over spasmodic muscle in inflammatory and
traumatic conditions induces muscle relaxation and reduces
pain.

TRAUMATIC CONDITIONS
The beneficial effects of short wave diathermy on traumatic
lesions are similar to those produced in inflammation. The
exudation of fluid (followed by increased absorption) and the
increased flow of blood through the area assist in the removal
of waste products, while the improved blood supply makes
available more nutritive materials, so assisting the healing
processes.

EFFECT ON HEALING TIME
The beneficial effect of SWD in traumatic conditions includes
fluid exudation, increased blood flow, removal of waste
products etc. The increased blood flow makes more nutritive
material therefore assist in healing process.

INDICATIONS
Disorders of the musculo-skeletal system
Sprains
Strains
Capsule lesions
Muscle and tendon tears
Chronic inflammatory/infective conditions
Degenerative joint disorder

Joint stiffness
Hematoma
Chronic Rhematoid arthritis
Tenosynovitis
Synovitis
Bursitis
Sinusitis
Carbuncles
Abscesses
Infected surgical incisions
Dysmenorrhoea
Frozen shoulder
Cervical spondylosis
Lumbar spondylosis

CONTRA-INDICATIONS
Over Metallic Implants: If there's any metallic implant of the body in the field of SWD, it will cause
concentration of the field and will result in destruction of adjacent tissues.
Haemorrhagic Areas: The increase in circulation can precipitate haemorrhage. E.g:haemophilia.
Over ischaemic Tissues: In, ischaemia, the circulation is unable to disperse the heat that could lead to
burns or even gangrene.
Over Malignant Tissues: The increase in temperature causes increase in metabolism, which could
accelerate neoplastic growth or even lead to metastasis of malignancy.
Tuberculous Joints: It may cause spread of infection, thereby leading to joint damage.
Impaired Thermal Sensation: Application of a safe level of intensity requires patient's sensitivity to
heat. Disturbed and impaired thermal sensation could result in high intensity being applied with
consequent tissue destruction.

 Unreliable Patients: In very old or very young patients, the cooperation in monitoring the
administration of the level of intensity cannot be guaranteed.
 Excessive Oedema: Non-inflammatory oedema is likely to be aggravated by the
administration of any form of heat.
 Recent Radiotherapy: For a period up to 3 months following therapeutic doses of
radiotherapy, skin sensation and circulation is diminished.
 Hypersensitivity to Heat: When liniment is applied, the circulation increases and if heat is
then applied, further increase in circulation may not be possible to disperse the heat.
 Acute Infection: There may be exacerbation of infection by heat.Eg: in case of
osteomyelitis.
 Cardiac Pacemaker: The intensity of SWD interfere with the functioning of pacemaker.
 Over Wet Dressings and Adhesive Tape: The heat is more readily absorbed and the field is
concentrated on that area. A burn or scald could result.
 Intra-Uterine Contraceptive Devices (IUCD): Those women using IUCD for contraception
should not take diathermy over pelvic region since these are metallic and the field may
concentrate, thereby causing tissue damage of adjacent areas.
 Over Pregnant Uterus: SWD may be harmful to the developing foetus.
 Venous thrombosis: Heat applied to the affected area may result in formation of embolus.

ADVERSE EFFECT OF SHORT WAVE DIATHERMY
BURNS
SHOCK

BURNS
Short wave diathermy can cause soft tissue burns when used at normal or excessive
doses and because the distribution of this type of energy varies significantly with the
type of tissue, it can burn some layers of tissue while sparing others.
Fat layers are at greatest risk of burning, particularly when plate applicators are
used, because they are more effectively heated by this type of muscle or skin and
therefore is not cooled as effectively vasodilation.
Because water is preferentially heated by all forms of diathermy, the patients skin
should be kept dry by wrapping with towels to avoid scaling by hot perspiration.

SHOCK
 The danger of electrical shock is present in the use of short wave diathermy. In this
case, both the patient and the therapist are potentially at risk.

THANK YOU

SWD FINAL.pptx

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SWD FINAL.pptx