Experiment (10)
Electrosurgical unit
 objective
Electro surgery is the application of a high-frequency electric current to
biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue.
 Theory
Electro surgery is the application of a high-frequency electric current to
biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue.
Electrosurgical devices are frequently used during surgical operations
helping to prevent blood loss in hospital operating rooms or in outpatient
procedures.
Different levels can be set on the ETU, depending on the depth of the cut
and the point of operation.
• “Cut” is used for cutting tissue.
• “Blend” uses a mixture of blending and coagulation. It is used to both cut
as well as stem the resulting bleeding,
• “Coagulation” is used for the maximum Homeostasis.
• “Dissection” is used chiefly for destroying tissue.
Mono-polar modes are used for cutting and coagulation, while the bipolar
mode that has forceps like an electrode is usually used for dissecting and
destroying tissue.
Fig (27) Electrosurgical unit
 The configuration and parts of the system
Types of electrosurgical unit:
•
Mono-Polar Technique (flow of current)
Active Electrode tip
Patient
Neural Electrode
Generator
Fig (28) Mono-Polar Technique
•
Bipolar Technique
Generator
Active Electrode
Fig (29) Bipolar Technique
 Block diagram
Fig (30) Electrosurgical unit block diagram
ESU Waveforms
Fig (31) Electrosurgical unit waveforms
 The principle of work of the system
Electrosurgical units (ESU) use a high-frequency electrical current to cut
tissue and control bleeding by causing coagulation. Tissue resistance to the
high-density current causes a heating effect which results in tissue
destruction. Electrical current is delivered and received through cables and
electrodes. The electrodes may be activated by either a hand piece switch
or a footswitch. The ESU may use a monopolar or a bipolar mode.
 The procedure of operation
A circuit for discharging stored energy in an electrosurgical generator. The
circuit includes a pulse width modulator for controlling a high voltage
power supply, an error signal generating circuit configured for delivering
an error signal as a difference between an output signal voltages with a
feedback voltage generated by the high voltage power supply. The error
signal is transmitted to the pulse width modulator. The circuit further
includes a switching circuit configured to switch in a load in parallel with
an output of the high voltage power supply when the error signal is lesser
than a first predetermined threshold to discharge the output.
Fig (32 ) Electrosurgical unit circuit