When a probe emitting gas is placed at an adequate distance from a tissue and high-frequency voltage is applied between the probe and the tissue, the gas between the probe and the tissue becomes ionized and electrically conductive. If the gas between the probe and the tissue is a noble gas (argon, helium, etc.), an electric strength for ionization is 500 V/mm. Among the noble gases, argon is relatively cheap, argon is preferred. The ionized argon gas forms argon plasma beams. It can be visualized as sparks. Argon plasma beams conduct the high-frequency current to the tissue, and result in coagulation and drying. The thermal effect of APC is limited to the devitalized tissue. The electrically active argon beams are directed from the probe to electrically conductive tissue closest to the probe. After the target tissue becomes dry and loses conductivity, the argon beams move from dry tissue to wet tissue. Because of the loss of conductivity at a treated tissue, the depth of drying, coagulation, devitalization is limited [5–7].

Argon plasma coagulator is consisted of argon tank, flow valves, probe and electrosurgical generator (Fig. 5.3). The argon tank is a cylinder with a pressure-reducing valve. Argon tank must have automatically controlled flow rates and limitation of the pressure.

An APC probe for endoscopy consists of a nonconductive flexible tube. The distal end of APC probe has electrode which is connected to the high-frequency generator by a wire within the lumen of flexible tube (Fig. 5.4). For safety, the electrode is receded from the distal end of the tube so that it cannot contact with tissue (Fig. 5.5).

An electrosurgical generator must be a high-frequency current source so that it must provide sufficiently high voltage for the ionization of argon.

The depth of coagulation depends on setting, application time and application technique. For a shallower depth, movement of activated probe tip is needed. If the activated probe is not moved for about 3–10 s, the depth of thermal effect is up to about 2 mm. Over 10 s, the depth of thermal effect increases to about 3–4 mm.

Several endoscopic clipping devices are commercially available. All devices have two components: metallic clips and deployment catheter-handle . Clips are double or triple pronged metals. The clip fixing device consists of a control section and insertion tube. The control section is a plastic parts that manipulate clip loading and firing. With the rotatable version, a rotator disk located on the control section and is used to turn the clip to the desired orientation. The insertion tube is made up of a metal coil and outer plastic sheath. At a distal end of the metal coil, there is a hooking apparatus for attaching of clip. The length of insertion tube is up to 230 cm.

The clips are basically multiangled stainless-steel ribbon . Standard hemoclips is measured 6 mm in length and 1.2 mm in width. The clips are available in several lengths (short/standard/long) and have an opening angle of 90° or 135°. Clips open from 6 to 12 mm, depending on the specific type.

Several endoscopic clips are currently available. (EZ clip and QuickClip (Olympus Medical, Tokyo, Japan), Resolution Clip (Microvasive Endoscopy, Boston Scientific Inc., Natick, MA, USA), Triclip (Cook Endoscopy, Winston-Salem, NC, USA), Multi-Clip (InScope Inc., a Division of Ethicon Endosurgery, Cincinnati, Ohio) (Fig. 5.6).

A single use clip-deploying device (QuickClip ) with a preloaded clip offsets the need for clip loading. Its configuration and function are otherwise similar to the reusable device, though it lacks the clip rotator in its original model. The QuickClip opens to 6 mm. A further modification on the single-use clipping device (QuickClip 2) includes the rotating mechanism, with a prong opening of 9.5 mm. A newly developed QuickClip Pro has open-and-close function to facilitate correct positioning prior to deployment. The arms can be closed, reopened and repositioned. QuickClip Pro includes the rotating mechanism, and can open to 11 mm. The QuickClip Pro is suitable for use in magnetic resonance (MR) environments.