DIATHERMY What is DIATHERMY? • The use of non-ionizing electromagnetic energy from the radio-frequency spectrum as therapeutic agent 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 Microwave SHORTWAVE DIATHERMY Superficial and Method of Heat deep heating Transfer modality - Conversion Frequency Manner of Delivery - 27.12 MHz - continuous Wavelength - pulsed - 11 m Continuous vs Pulsed SWD PULSED SWD

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) Calculating Mean Power in PSWD

1. Cycle Duration = 1000 / PRR

2. % cycle SWD delivered = (PD x 100) / Cycle Duration

3. Mean Power delivered = PPP x % cycle SWD SHORTWAVE DIATHERMY UNIT

HEAT PRODUCTION

• Dependent on: SPECIFIC ABSORPTION RATE Tissue conductivity charged molecules dipolar molecules non-polar molecules Electrical field magnitude Charged Molecules Ions and certain proteins Molecules are accelerated along + -

lines of electric force + -

+ -

Most efficient way of + - heat production 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 Non-Polar Molecules

• Fat cells • Electron cloud is distorted but negligible heat is produced • Least efficient heat production Clinical Implication !

• 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 SHORTWAVE DIATHERMY

Condenser Induction Field Field CONDENSER FIELD

• 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

Ways of Application Contraplanar - aka Transverse positioning - plates are on either side of the limb Ways of Application Coplanar - plates parallel with the longitudinal section of the body part; same side Ways of Application Longitudinal - plates are placed at each end of the limb In what way should SWD be applied?

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

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

• 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 Arrangement of Inductive Coil 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 Which is more effective: condenser or induction field?

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 THERAPEUTIC EFFECTS (continuous and pulsed)

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

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 INDICATIONS

• Recent ankle injuries - inconclusive results following three double-blind protocols (Kitchen and Bazin) INDICATIONS A. Nerve Regeneration Pain Syndromes - studies were done on cats - Pulsed SWD may and rats provide better - PSWD induced regeneration of axons, pain relief in some acceleration and recovery of musculoskeletal nerve conduction conditions (neck B. Osteoarthritis and back) than - no established effect SWD C. Post-operative - insignificant (abdominal MICROWAVE DIATHERMY 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 MICROWAVE DIATHERMY APPARATUS How is microwave produced?

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 Fate of Microwave

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 THERAPEUTIC EFFECTS

• Increased blood flow or circulation to the area • Increased tissue temperature • Increased metabolism • Facilitate relaxation • Increased pain threshold • Decreased blood viscosity INDICATIONS

• Soft tissue injury • Mobilization • Pain relief CONTRAINDICATIONS • Pacemakers • Malignant CA • Metal implants • Active TB • Impaired • Fever sensation • Thrombosis • Pregnancy • X-ray exposure • Hemorrhage • Uncooperative • Ischemic Tissue patient • Testicles and eyes • Areas of poor circulation PRECAUTIONS

• Operator should observe caution when handling the machine: same contraindications apply

Production of Microwave: - Produced by high frequency current and have same frequency as the currents which produce them - Not produced by Oscillators/ Vacuum tube valves / Solid state devices Magnetron: - Consists of cylindrical cathode surrounded by an anode structure with cavities opening into the cathode Anode space by means of slot. • O/P energy is derived from the resonator system by means of a coupling loop forced into one of the cavities. • The energy picked up on the coupling loop is carried out of the magnetron on the central conductor of a co-axial o/p tube throgh a glass seal to the director • Director has radiating element of antenna • Electrical current transformed to antenna & emits EM radiation. Then a reflector which direct energy to the patient. Components of Microwave Diathermy

• Main supply voltage • Interference Suppression filter( Bypass the high frequency pick up generated by Magnetron) • Fan motor connected with power supply ( Used to cool magnetron) Delay Circuit

• Magnetron has to warmup for 3 to 4 minutes before power may be delivered from it • Delay ckt – connects the anode supply to the magnetron after this time elapse • Lamp lights up after 5 minutes – For indicates that apparatus is ready to use Magnetron Circuit

• Filament heating voltage is obtained directly from the secondary winding of the transformer • Cathode circuit contains suppression filters • Anode supply may be DC or AC. • DC voltage from full wave rectifier followed by voltage doubler circuit • A high wattage variable resistance in series controls current applied to the anode circuit • AC voltage is applied to the anode of the through series connected thyrotron sothat AC voltages of both tubes are equal in phase. • The amount of the current through the magnetron /output power can be varied by shifting the phase of the control grid voltage with respect to the phase of the anode voltage • Phase shift can be achieved – By using capacitor resistor network. Safety circuit

• Fuse(500 mA) in the anode supply circuit • Large self inductance coils in primary supply– For considerable interference • Due to small dimensions – cores become saturated- to avoid that coils are split up in such a way that no magnetization • Duration of irradiation – 10 to 25 minutes. • Skin should be dry as these waves are absorbed by water. Electrotherapy i-t curve • First stimulated with long impulses ( first 1s pulse duration then 0-05ms) • For each impulse duration the current intensity is adjusted until the stimulation threshold has been exceeded. • So the current intensity has to be achieved to keep threshold value • Impulse Duration(1000-300-100-10-3-1-0.05ms)

Chronaxie Period: Minimum duration of impulse that will produce a response with a current of double of the rheobase Rheobase: Minimum intensity of current that will produce a response if the stimulus is of finite duration

Galvanic current • Steady flow of direct current • Movement of ions and their collection at the skin areas lying beneath the electrodes • Bright red coloration due to increased blood flow • For atonic Paralysis, for treatment of disturbance in blood flow, iontophoresis • Current intensity – 0.3 to 0.5 ma/sq.cm • Duration : 10-20 minutes Faradic current

• Sequence of pulses with defined shape & current intensity • Pulse duration – 1minute triangular waves with interval 20 minutes • Acts upon muscle tissue and upon the motor nerves to produce muscle contractions • No ion transfer & No chemical effect • Treatment of muscle weakness after immobilization and disuse atrophy & functional paralysis treatment Surging current

• Peak current increases & decreases rhythmically & the rate of increase and decrease of peak amplitude is slow • Surge rate: 6-60 surges / minute • Ratio of interval to the duration of surging is varied • For the treatment of spasm and pain Exponentially progressive current • For the treatment of severe paralysis • Possibility of providing selective stimulation • Slope of the exponential pulse is varied Biphasic Stimulation • Stimulating pulse is followed by a pulse of opposite polarity of 1/10th amplitude & 1o times the width • Neutralize the polarization of the electrodes • Reduces muscle fatique

Multivibrators role in Functional Electrical simulation • M1 – Set basic stimulus Frequency. Variable rate MV – Trigger M2 • M2 Monostable MV – sets the pulse width- Provide an interrupted Galvonic output (Rate and duration can be controlled • M4 – Astable MV- produces short duration faradic current • M3 – Faradic current modulated at the frequency set by M1- output is surged faradic ( Slow rate of increase and decrease in intensity) • By integrating the output of M2 interrupted galvanic pulses – can be modified to have an exponential rise and fall • Galvonic current – By suitably tapping the DC supply • Selector switch to emitter follower stage – To Low impedance constant voltage output • Floating type – isolated from earth • Isolation transformer or RF Coupling Different types : Constant voltage / constant current type Advantages of Constant current Therapy • Current flow is constant irrespective of the patients resistance • Distortion free • Avoids irradiating stimulatory sensation between electrodes by keeping electrodes firmly to the skin and in one position Interferrential Current therapy

• Fixed Frequency – 4000 Hz • Second adjustable Frequency: 4001 – 4400 Hz • By Heterodyning Interference frequency is created • Concentrated at the point of intersection between the electrodes • Current perfuse over the greater depth and over a larger volume of tissue then other forms of electrical therapy

• At interferential range ( 4000Hz) – Rsistance is 80 times lower at 50 Hz(in conventional system) • So current crosses the skin easily with less stimulation • Tolerable – Dosage can be increased • To deep structures Equipment Details

• 2 Channel + 4 electrodes ( In Quad Polar arrangement • Each channel – Sinusoidal symmetrical a.c at high Frequency (2000- 5000Hz) • Both undergone constructive and Destructive Interference