medical electronics surgical diathermy

8/22/2019 Medical Electronics Surgical Diathermy

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SURGICAL DIATHERMY


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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


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Electro surgical unit:


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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)


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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.


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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


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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


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Electro surgery techniques:

Mono polar technique: depends on the contact

area

Bi polar technique :two electrodes. Contact

area is less. Safer and precise.


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Electrodes used:

Needle electrode: desiccation

lancet electrode: cutting

Loop electrode : ecsecting (opening) thechannels, extirpating growth

Performance:improper placement of

electrode Loss of energy ( Mono phasic electrode)


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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 forheating purpose


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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)


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Circuit diathermy and automatic tuning:

Page no: 762

Anode voltage: 4000 V

Controlling the anode voltage, filament heatingcurrent

Adjusting the grid leak resistance, R1.


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Application technique:

Capacitor plate method:

Tissues are kept sandwiched between the two

pads

No direct contact

Also called as Condenser method


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Contd.

Inductive method:

The cable is coiled around the arm

RF current is passed and the magnetic fieldapplies the heat (electro static action)

Also called as inductohermy


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Diapulse therapy:

Increase in energy output

avoids the dangers of heat

Pulse width : 65 micro second Interval : 1600 micro second


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Micro wave diathermy:

Frequency : 300 to 30,000 MHz (2450 MHz)

Wavelength : 10 mm to 1 m (12.25 cm)


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Contd.

Delay circuit

Magnetron circuit

Safety circuit


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Ultrasonic therapy unit:

Absorption property of the tissues

Piezo electric effect


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Contd.

Controlling the firing angle

Frequency of ultrasound

Intensity of ultrasound Duration of exposure

Avoids injury


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Apparatus:

Galvanic current:

Steady flow of current

10-20 minutes


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Contd.

Exponentially progressive current:

Independent pulse duration


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Contd.

Faradic current:

Sequence of pulses

With defined shape and current80 mA of magnitude

25 surges per minute


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Functional diagram:


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Contd.

Distortion free

Irrespective of patients resistance

Position of the electrodes should be rigid Mono-polar electrode : indifferent electrode is

placed near to the active electrode.


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Transcutaneous electrical nerve

stimulator:

Gate control theory: prevents pain carrying

messages

Endorsphin release theory: stimulation of pain

killing substance (Endorsphin)


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Spinal cord stimulator:

Not for patients using triggered or inhibited

type of pacemakers


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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


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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


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Contd.

Bladder stimulators:

Reflex actions can be controlled

Possible kidney malfunction Cerebellar stimulators:

Inhibiting intractable epilepsy

medical electronics surgical diathermy

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