Surgery – Instruments – Electrical application
Reexamination Certificate
1999-08-23
2001-04-03
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S040000, C219S121510
Reexamination Certificate
active
06210410
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a coagulation apparatus, in particular a plasma coagulation apparatus.
BACKGROUND OF THE INVENTION
The German patent DE 37 10 489 C2 discloses a plasma coagulation apparatus intended for use in open surgery. In this apparatus argon is ejected from a nozzle in the center of which is a discharge electrode, with sufficient pressure and flow velocity that in addition to the coagulation effect produced by an arc formed between the electrode and the tissue to be coagulated, fluids “floating” on the tissue are pushed away. With this arrangement the risk of embolism is very high. Furthermore, it is extremely problematic to use this apparatus in body cavities because the large amounts of gas typically introduced in the cavities can lead to undesired insufflation effects.
A coagulation apparatus for use in an endoscope is known from U.S. Pat. No. 5,207,675. In this apparatus a tube, within which an electrode is slidably disposed, is inserted into the working channel of an endoscope in such a way that it can be manipulated within said channel by means of a handle, like an (ordinary) instrument. The electrode, which should simultaneously be constructed as an instrument, is kept in a state such that it projects from the tube when in the working (coagulating) mode, in which argon is expelled from the tube that houses the electrode. While in this state, if the electrode touches the tissue to be coagulated, considerable tissue damage can result. In the case of thin-walled tissues, the consequences (rupture, etc.) can be fatal.
In DE 195 35 811 A1 a coagulation apparatus of the kind cited above is described that goes some way toward avoiding the substantial problems associated with the arrangements just described. In particular, the end of the tube housing the electrode is so constructed that there is no danger of embolism even when a relatively strong gas stream is applied, during which time the electrode is withdrawn into the gas-emitting tube far enough that it cannot make direct contact with the tissue. However, this arrangement is relatively complicated to manufacture.
The object of the invention is to disclose a coagulation apparatus that ensures increased safety in use and improved operation, while reducing the manufacturing complexity and cost.
SUMMARY OF THE INVENTION
An essential point of the invention is that it departs completely from the idea that (noble) gas must be aimed directly at the site where coagulation is occurring, i.e. by means of a tube within which the current-supplying electrode is disposed. Instead, in the present invention the working channel itself is used as a conduit to transport the gas, while the electrode can be constructed as a fully insulated wire with no lumen. Surprisingly, it has been found that no disadvantageous effects are introduced by the fact that the gas emerges from an end of the working channel proximal to the distal end of the conductor—that is, proximal to the discharge section—and that the discharge section occupies no precisely specified position with respect to the end of the working channel, from which the gas emerges. On the other hand, it is considerably simpler to construct the conductor as an insulated wire without a lumen, which reduces the costs of manufacture and enables disposable conductors to the used. This in turn reduces the risk of infection.
Furthermore, conductors without a lumen are not only simpler to manufacture but, because conductors have small diameters it's possible for the coagulation apparatus incorporating such conductors to be further miniaturized as a whole. At the same time, however, a considerably larger cross section for flow through the gas-supply conduit is ensured, which offers the advantage that the regulation of the gas supply can be substantially improved in the simplest possible manner. That is, the gas pressure at the distal end of the working channel can be assumed to differ only negligibly from the gas pressure at its proximal end, because with the large flow cross sections achievable here, only a slight pressure drop (given the customary, not too large flow velocities) is to be expected. Hence it is possible simultaneously (with appropriate regulation of the gas-supply pressure) to eliminate in advance the danger that, if the gas does not flow away as intended, an uncontrolled, damaging insufflation will occur.
With absolute certainty the possibility is avoided that an excessively strong laminar gas stream will strike the region of the tissue to be coagulated, which, as mentioned, could cause an embolism.
Preferably the conductor comprises at least one wire, which by means of a closely apposed layer of insulation is insulated in particular from the endoscope, i.e. the wall of the working channel. The arrangement described here is thus particularly simple to manufacture. Preferably in this case the wire is chosen to be stiffly elastic so that proximal fixation of the conductor also ensures adequate fixation of its distal end and hence of the discharge section. It is therefore not necessary to guide the conductor so that it is precisely coaxial with the working channel and, in particular, to keep it exactly in position in the end region, because—surprisingly—the preferably gently outflowing current of noble gas forms a kind of “cloud” that fills the region between the discharge section and the tissue to be coagulated.
The layer of insulation is preferably so constructed that a specific capacitance, preferably matched to the frequency of the coagulation current, is produced between conductor and wall, so that optimal performance can be ensured. In particular, the capacitance (stray capacitance) between conductor and wall should be kept very low in order to minimize losses.
Preferably the insulation layer consists of thermally stable material, in particular polytetrafluoroethylene or a similar plastic resistant to high temperatures.
The protective device is preferably so constructed that a substantially undirected discharge at the discharge section is ensured. This measure is intended to make certain that the discharge current flows between the discharge section and a section of the tissue with a relatively high moisture content and hence a relatively low resistance (per unit area). As a result, it is ensured that the coagulation current “finds its way” automatically from the discharge section. An especially uniform and rapid coagulation effect can thus be guaranteed.
There are various possible ways to construct the protective device in such a way that no excessively large, potentially damaging coagulation currents will flow.
In a first embodiment of the invention the protective device is formed directly by the insulation layer, inasmuch as the ends thereof project beyond the current-conducting part (in the direction of the conductor). Many geometrical shapes are conceivable here.
the protective device can be constructed as a separate part, in particular as a sheath-, ball- or basket-shaped part made of insulating, thermally stable material. Ceramic material is especially suitable for this purpose.
Preferably the discharge section comprises substantially punctate or tip-shaped discharge electrodes. This measure ensures easy ignition of the plasma owing to the high field strengths at the pointed tips. It also increases safety in operation, because it is not necessary to use too-high voltages to trigger the discharge.
In an especially preferred embodiment of the invention the discharge section comprises a plurality of discharge electrodes arranged in parallel electrically and substantially defining a continuous surface, in which the electrodes are substantially equidistant from one another and separated by layers of insulation. When such uniformly distributed, punctate electrodes are used, which in addition are disposed substantially in a plane or in a convex surface, preferably flush with the end surface of the insulation, it is ensured that even if the electrodes make direct contact with the tissue, no serious damage to the tissue will result. The re
Farin Gunter
Grund Karl Ernst
Erbe Elektromedizin GmbH
Peffley Michael
St. Onge Steward Johnston & Reens LLC
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