Medical Electronics Surgical Diathermy

SURGICAL DIATHERMY

DIATHERMY: • Used during cutting and coagulation of the tissues • Consists of high frequency power oscillators • Spark gap oscillators • Undamped current: clean cutting • Damped current: coagulation

Electro surgical unit:

Requirement: • • • • • •

High temperature exceeding 1000 degree C 1 mm diameter of cross section of arc High current density Frequency : 250 Hz to 1 MHz Cutting : 400 W Coagulation : 150 W (10-15 s & 15 KHz)

Block diagram: • Control panel & logic board: produces the basic signal and timing informations • Operates the relays, give visual indications and determine the alarm conditions • Isolated and carefully insulated • Avoid contact to conducting surfaces.

Automated electro-surgical systems: • • • • •

Size and shape of cutting electrode Type and speed of cut Tissue properties Voltage control or spark control Programmed processors decides the spark intensity

Contd. • Soft coagulation: no electric arcs, prevents skin from carbonized • Forced coagulation: arcs are intentionally generated between the coagulation electrode and the tissue (deeper coagulation) • Spray coagulation: arcs are deliberately produced. Contact is not necessary

Electro surgery techniques: • Mono polar technique: depends on the contact area • Bi polar technique : two electrodes. Contact area is less. Safer and precise.

Electrodes used: • Needle electrode: desiccation • lancet electrode: cutting • Loop electrode : ecsecting (opening) the channels, extirpating growth • Performance: improper placement of electrode • Loss of energy ( Mono phasic electrode)

LASER Physiotherapy and electrotherapy equipments • Heat radiation by the application of high frequency radiation (through heating) • Muscles, bones, internal organs etc. • Polarity of the electric field alters, continuous re-alignment of the molecules • Microwaves and ultrasonic waves are used for heating purpose

Short wave diathermy: • Hot towels, infrared lamps, electric heating pads • Heat is produced within the body rather not transferred through the skin (to avoid discomfort and skin burns) • Can be controlled precisely • AC frequency : 27.12 MHz ( no muscle contraction)

Circuit diathermy and automatic tuning: • Page no: 762

• Anode voltage: 4000 V • Controlling the anode voltage, filament heating current • Adjusting the grid leak resistance, R1.

Application technique: • Capacitor plate method: • Tissues are kept sandwiched between the two pads • No direct contact • Also called as Condenser method

Contd. • Inductive method: • The cable is coiled around the arm • RF current is passed and the magnetic field applies the heat (electro static action) • Also called as inductohermy

Diapulse therapy: • • • •

Increase in energy output avoids the dangers of heat Pulse width : 65 micro second Interval : 1600 micro second

Micro wave diathermy: • Frequency : 300 to 30,000 MHz (2450 MHz) • Wavelength : 10 mm to 1 m (12.25 cm)

Contd. • Delay circuit • Magnetron circuit • Safety circuit

Ultrasonic therapy unit: • Absorption property of the tissues • Piezo electric effect

Contd. • • • • •

Controlling the firing angle Frequency of ultrasound Intensity of ultrasound Duration of exposure Avoids injury

Apparatus: • Galvanic current: Steady flow of current 10-20 minutes

Contd. • Exponentially progressive current: Independent pulse duration

Contd. • Faradic current: Sequence of pulses With defined shape and current 80 mA of magnitude 25 surges per minute

Functional diagram:

Contd. • • • •

Distortion free Irrespective of patient’s resistance Position of the electrodes should be rigid Mono-polar electrode : indifferent electrode is placed near to the active electrode.

Transcutaneous electrical nerve stimulator: • Gate control theory: prevents pain carrying messages • Endorsphin release theory: stimulation of pain killing substance (Endorsphin)

Spinal cord stimulator: • Not for patients using triggered or inhibited type of pacemakers

Magnetic stimulator: • Electrical stimulator is very painful • Magnetic pulse is generated by passing a brief, high-current pulse through a coil of wire • Still experimental

Diaphragm pacing by radio frequency for the treatment of chronic ventilatory insufficency: • Only one phrenic nerve could affect normal oxygen and carbon-di-oxide exchange

Contd. • • • • •

Bladder stimulators: Reflex actions can be controlled Possible kidney malfunction Cerebellar stimulators: Inhibiting intractable epilepsy