Electrophysical Principles - Carlo De Giorgi SURGERY PLUS Manual De Instrucciones

ELECTROPHYSICAL PRINCIPLES
In the electrosurgical interventations the traditional use of blade surgical is substituted
by electrosurgical needle that allows making in a fast, simple and effective way the cut
and coagulation.
The electrosurgical needle is made on the principle of electrical energy conversion in
heat and it's constituted by:
●
a sinusoidal oscillator in radiofrequency
●
a generator of wave packets, with repetition frequency of packets equal to 15 –
30 kHz;
●
a mixer for the transfer, to the power amplification block, of the only wave form
adapt to the cut, or the only wave form for the coagulum, or a signal obtained by
an opportune mixing of the two;
●
a power amplification block able to supply the necessary power in terms of cur-
rent and to transmit to the electrodes, by transformer, the amplified signal;
●
a security circuit for the return electrode (for over 50W), to take possible cable
interruptions and disarm the radiofrequency supply;
●
by an active electrode opportunely shaped (handle);
●
by a return electrode (neutral) that close the circuit by the patient.
The current that crosses the biological tissue can cause:
1. Joule Effect
2. Faradic Effect
3. Electrolytic Effect
1) Joule Effect
In the biological tissue, crossed by electrical current, it's produced a heating (thermical
effect), dependent by the electrical resistance of the tissue, by the current density, by the
application time and that can determine many cellular transformations
The thermical effect influence (Joule Effect) is made by:
●
Current Intensity and output power
●
Modulation level
Parameters interpretable by the wave form of the high frequency current produced by
the generator.
●
Electrode shape
The electrode shape can be needle or rounded according to the necessity, it has re-
duced dimension; for this the current density on the point surface [A· m
electrodes with a thin section create a high current density, and high temperature, favor-
ing the cut action. Those with a big surface create a smaller current density, a smaller
temperature, realizing a coagulation effect.
●
State of active electrode
The thermical effects can be reported to the human body resistance, to which must be
added the electrode contact resistance. It's indispensable to maintain the active elec-
trodes perfectly clean to not have a reduction of it.
●
Characteristics of the tissue
The resistive characteristics change according to the biological tissues.
Biological tissue
(range from 0,3 to 1 MHz)
Blood 0,16 x 10
Muscle, kidney, heart 0,2 x 10
Liver 0,3 x 10
Brain 0,7 x 10
Lung 1,0 x 10
Fat 3,3 x 10
(Example of specific resistances of organic and metallic materials)
MA505a_IT-EN-ES-FR-DE
Q = I x R x T
2
3
3
3
3
3
3
Metals
Silver 0,16 x 10
-5
Branch 0,17 x 10
-5
Gold 0,22 x 10
-5
Aluminum 0,29 x 10
-5
EN
] is highest. The
-2
EN 5