Surgery – Instruments – Electrical application
Reexamination Certificate
1999-07-09
2001-03-06
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S040000, C219S121500
Reexamination Certificate
active
06197026
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electrosurgical instrument for the coagulation of biological tissues.
Plasma surgery is a method of monopolar high-frequency surgery (HF surgery) in which a high-frequency electrical current (HF current) produced by a high-frequency generator (HF generator) is sent through an ionized noble gas (plasma), for example argon (argon plasma), from an electrical pole within a suitable surgical instrument onto the tissue to be treated and from there is conducted back to the HF generator through a so-called neutral electrode applied to the patient (G. Farin et al.: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications; Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 71-77). As a result heat is introduced to the tissue, both endogenously by the HF current and exogenously by the higher temperature of the plasma relative to the tissue, so that the temperature of the tissue rises. Depending on the temperature various thermal effects are caused in the tissue, which can be used by surgeons for various therapeutic purposes such as blood coagulation or hemostasis and/or the thermal devitalization or destruction of pathological tissues (K. E. Grund et al.: Argon Plasma Coagulation in Flexible Endoscopy, Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 42-46).
A substantial physical prerequisite for plasma surgery is a noble gas, such as the aforementioned argon or helium, which must be present between the electrical pole formed by an electrode within the instrument and the tissue to be treated. The reason is that noble gases can be ionized with relatively low electrical field strengths in comparison to oxygen and/or nitrogen or air, and they do not react chemically with the tissue. Hence the tissue is not carbonized or even vaporized.
Within the last five years plasma surgery, in particular in the course of flexible endoscopy, has found a broad indication spectrum (K. E. Grund: DMW), so that a variety of demands are made with respect to the application techniques and the instruments, HF generators and gas sources required.
The U.S. Pat. No. 5,207,675 discloses an electrosurgical instrument that is problematic inasmuch as the electrode of the instrument can unintentionally come into direct contact with the tissue. Because of the relatively high HF voltage at the electrode, there is thus a risk that in particular thin-walled organs, such as those that are ordinarily present in the gastrointestinal tract and in the tracheobronchial system, may be perforated.
The patent DE 41 39 029 A1 discloses an electrosurgical instrument in which the electrode is disposed within the instrument in such a way that it does not touch the tissue, as long as the instrument is used according to instructions. A problem with this instrument is that the noble gas flows out of one or several openings at the distal end of the instrument in a predetermined direction. As a result the HF current can also flow to the tissue only in this directed (ionized) gas stream. When large-area lesions are to be treated this is disadvantageous inasmuch as the instrument must be moved several times over the tissue to be treated in order that the HF current and thus also the intended thermal effects are applied as uniformly as possible over the entire large area of the lesion.
In DE 195 35 811 C1 an electrosurgical instrument of the kind cited above is disclosed in which a diffusor is provided at the gas outlet, which is intended to prevent a mechanical action on liquid and tissue. In particular during the treatment of large-area lesions, however, it has been found that as a result of the unavoidable or even desired turbulences in the current of noble gas, mixing of the noble gas with the ambient gas (which as a rule is air) occurs, so that the specific advantages of plasma surgery are partially abolished.
SUMMARY OF THE INVENTION
The object of the invention is to develop a surgical instrument of the kind cited above further in such a way that the treatment of even large-area lesions is improved.
More particularly, the invention is an electrosurgial instrument for the coagulation of biological tissue, comprising a body including at least one outlet opening, and a gas source to supply an inert gas, in particular a noble gas, to the at least one outlet opening. The outflow opening is constructed in the shape of a slit so that the inert gas emerges in a flat laminar stream, so that the inert gas arrives at the tissue substantially without becoming mixed with ambient air. The instrument also further includes an HF source to supply a coagulation current to an electrode device disposed in the region of the at least one outflow opening.
One of the principle features of this invention is the provision of an electrosurgical instrument that on one hand forms a fan-shaped stream of noble gas and on the other hand structures this stream so that mixing with ambient air practically does not occur. At the same time the gas pressure is so regulated by the invention as to avoid blowing liquid away from the tissue and to prevent the gas from entering an open blood vessel. These measures ensure that large-area lesions can be rapidly treated by a relatively slight gas stream, while still avoiding the above-mentioned danger of tissue destruction.
Preferably the electrode devices comprise at least one electrode that is disposed in the region of the outflow opening in such a way as reliably to avoid direct touching of the tissue by the electrode. Preferably in addition the electrode should be such as reliably to prevent an ignition of an arc or plasma in an inert gas contaminated by ambient air or even in air alone, both of which would be associated with the negative effects cited above.
The electrode devices comprise at least one electrode that is disposed at a substantially uniform distance from substantially all regions of the outflow opening. This feature ensures that if a uniform distance is maintained between outflow opening and tissue, a uniform band of plasma is produced, which in turn has a uniform action on the tissue to be treated.
The outflow opening is preferably so shaped and/or arranged that the pressure of the emerging inert gas is constant over substantially the entire cross section of the outflow opening. The result is, first, that a particularly uniform gas stream is produced, in which turbulence and stream deformations are avoided owing to the absence of pressure differences within the gas; on the other hand, it is ensured that all regions of the gas stream impinge “gently” on the tissue, so that a uniform plasma production is ensured.
The outflow opening is preferably so shaped and positioned on the instrument that the contact area of the stream is substantially perpendicular to a main direction of movement of the instrument. As a result, a large lesion can be treated in a minimal number of movement sequences.
The cross section of the outflow opening is preferably small in relation to the cross section of a gas-supply conduit through which the inert gas is delivered from the gas source to the outflow opening. This measure minimizes the pressure gradients within the region of the ouflow opening.
The outflow opening in one preferred embodiment of the invention is surrounded by ceramic material. Particularly in the case of re-usable probes, this ensures that no changes in shape of the outflow opening occur during use.
It is especially preferred to construct the instrument as a tubular probe and to use it in endoscopic operations in which the probe is passed through a working channel of an endoscope.
The outflow opening in this case is preferably disposed at the outer circumference of the probe at a distance from its distal end, i.e. opposite the gas source. This distance of the outflow opening from the distal end of the probe does not only offer advantages with respect to flow technology; rather, it is also an advantage for the person operating the instrument if the opening is not quite at the distal end.
Farin Gunter
Grund Karl Ernst
Erbe Elektromedizin GmbH
Peffley Michael
St. Onge Steward Johnston & Reens LLC
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