Endoscopy Practice and Safety
Peter B. Cotton
6. Principles of electrosurgery, laser, and argon plasma coagulation with particular regard to colonoscopy
G. Farin & K.E. Grund
Fig. 1 Diagram of the wall of the right and left colon with scale representation of thickness as well as small, medium, and large
Fig. 2 Thermal effects in biological tissue resulting from application of high or low (peak) voltage high-frequency current.
Fig. 3Modalities of heat surgery. (a) Heat (h) from a heat source flows into tissue. (b) Heat (h) from the tissue flows into a heat
sink such as a blood vessel. (c) Electric current IHF becomes converted to heat (h) within the tissue. (d) Laser becomes converted
to heat (h) within the tissue.
Fig. 4 (a,b,c) Injection of fluid into the submucosa will increase the distance between a target tissue which is to be heated and
adjacent tissue which should not be heated.
Fig. 5 Heat flow (h) within tissue must be taken into account during use of electrosurgery. IHF, high-frequency current; UHF, high-frequency
Fig. 6 (a) Heater probe can be used to compress and coagulate medium-sized vessels. (b) Thermal damage to the muscularis propria
may result from several factors such as temperature, pressure, and duration.
Fig. 7 Application techniques of electrosurgery: (a) monopolar; (b) bipolar; (c) quasi bipolar.
Fig. 8 Current density and the resulting penetration depth of thermal effect in the tissue is dependent on the size of the contact
Fig. 9 Schematic of electro-hydro-thermo (EHT) probes.
Fig. 10 Schematic depiction of current flow of bipolar coagulation probes.
Fig. 11 Schematic of the electrosurgical cut effect. (a) Electric sparks ignite between an electrode and tissue if the HF voltage UHF is sufficiently high. (b) The high temperature of the electric sparks evaporates the tissue adjacent to the electrode which will cause a cut if moved
Fig. 12 Electrosurgical effects on tissue. The cut edges become devitalized, coagulated (k) and carbonized in proportion to the peak
voltage (UHF) and the intensity of the electric sparks (F). (a) Graphic depiction. (b) Photograph of effect on tissue with
low and high voltage.
Fig. 13 Depiction of mechanical friction at different parts of the polypectomy snare.
Fig. 14 Unintended thermal effects. (a) If part of a polyp touches the colon wall during polypectomy HF current can flow through this
contact point into the colon wall. The closer the snare to this point, the higher the flow of HF current through it. (b) If
an endoloop is placed around the polyp the HF current must flow through the strangulated part of the polyp and heat will increase
at the point of constriction because of the higher current density. (c) Photographic demonstration of (b) with increased heat
damage at point of narrowing.
Fig. 15 The principle of argon plasma coagulation (APC).
Fig. 16 Equipment for APC: argon tank, flow valves, probe, electrosurgical generator.
Fig. 17 An APC probe and its distal end.
Fig. 18 The depth of APC coagulation depends on the application time and power setting.
Fig. 19 The profile of argon gas flow from an APC probe.
Fig. 20 The effects of forward- and side-firing APC probe application.
Fig. 21 The influence of power as well as the distance between the distal end of the laser fiber and tissue, where P2 > P1 and X1
Fig. 22 Tissue effect is related to the distance between the distal end of the laser fiber and the tissue.
Fig. 23 Optimum treatment required by case.
Copyright © Blackwell Publishing, 2005