Objectives. To study the influence of the electrosurgical generator on the vaporization efficacy during electrovaporization (EVAP) using different vaporization elements.

Methods. Electrical properties of human prostatic (in vivo) and bovine myocardium (in vitro) tissue were measured under electroresection and electrovaporization conditions. The effective output power of four different generators (“old generation” Force 4 and Force 40 and “new generation” Force 300 and Force FX) was measured at different impedance loads. In vitro, the coagulation and vaporization capabilities of the electrosurgical generators in combination with resection and vaporization elements were studied on homogeneous tissue (bovine myocardium).

Results. The electrical impedance of human prostatic tissue and bovine myocardium increases from 400 to 1000 Ω when coagulated. The effective output power of the old generation electrosurgical devices depends strongly on tissue impedance. This implies that working on already coagulated tissue using such devices is not well controlled and not reproducible. By contrast, new generation electrosurgical devices correct for the higher impedance of coagulated tissue, thus delivering constant output power and corresponding tissue effects.

Conclusions. For an effective application of the EVAP technique, the use of a new generation impedance independent electrosurgical unit is highly recommended.