Technological fundamentals of endoscopic haemostasis.
In order to perform endoscopic haemostasis there exist several different mechanical, biochemical and thermal methods, which may be applied together with rigid or fully flexible endoscopes in different situations. The technological fundamentals of convective, conductive and radiative heat transfer, the irradiation with coherent electromagnetic waves like microwaves and laser radiation and the resistive heating by RF-current are described. A review of the state of the art of haemostatic coagulation by laser radiation (photocoagulation) and radio-frequency currents (surgical diathermy, high-frequency coagulation) is given. The wavelength-dependent interactions of coherent light waves are compared especially for the three mainly different laser types, i.e., carbon-dioxide-, neodymium-YAG- and argon-ion-laser. The well-known disadvantages of the conventional RF-coagulation are overcome by the so-called electrohydrothermosation (EHT), i.e. the liquid-assisted application of resistive heating of biological tissues to perform haemostasis. Different technological solutions for bipolar RF-coagulation probes including ball-tips and forceps are shown and the first experimental results are discussed in comparison.