27/04/04 ©
Söring
Users manual RF-units
1
not valid for MBC600
-13-
smooth
cut
Cut, rich of
coagulation
Cut with eschar
Fig. 3.6
The smooth cut is largely comparable to the cut with a conventional scalpel, i.e. the cutting
surfaces are only slightly colored. This cutting mode is achieved with unmodulated RF-current and
by carrying-out the cut quickly.
A reduction of cutting speed gives a more coagulated cut even to the point of eschar with enough
speed reduction. The same result is achieved when using a pulse modulated RF current with the
same average power.
The power necessary for performing a RF cut depends on the shape of the electrode, type of
tissue and its resistance. If the power is too low, no cell rupture takes place and the tissue sticks
to the electrode. If the applied power is too high, spark discharges between electrode and tissue
are possible which causes carbonization of the cut surfaces.
3.2.2. Coagulation
For coagulation the tissue is heated more or less to such a degree that no cell rupture occurs.
The temperature for coagulation is above 50°C. This temperature leads to a coagulation of the
intra- and extra-cellular albumin (boiling of tissue). Perforated blood vessels contract so far that
the vessel is totally closed and no blood flows out. In order to obtain this effect, the electric
current must heat the tissue at a sufficiently slow speed so that the intra- and extra-cellular fluids
are vaporized without destroying the cell membranes. By this loss of fluid the cells contract and
the cell membranes are welded together.
This kind of coagulation is often called contact coagulation because the electrodes (shapes are
balls or plates) are brought into direct contact with the tissue. A supply of RF current causes a
light coloring of the tissue and a flow out of tissue fluid due to coagulation of cellular albumin.
3.2.3. Electrodessication
Electrodessication is a special mode of coagulation and is nowadays called Spray coagulation. By
means of a very high RF voltage, sparks or arcs between electrode and tissue surface are
