Multi-lumen probe

Abstract

The apparatus (10) according to the application comprises a probe hose (14), in the center of which a conductor (31) is provided for the supply of an electrode (30). Around the conductor (31) a plurality of gas guide lumens (22, 23, 24) are arranged concentrically, which are isolated from one another by means of partition walls (18, 19, 20). The partition walls (18, 19, 20) support a central section (21), which is arranged centrally and accommodates the conductor (31). With this probe design, a particularly flexible and particularly thin probe with a particularly high dielectric strength can be produced.

Description

TECHNICAL FIELD

[0001] The present invention relates to an instrument for treating biological tissue, in particular for argon plasma coagulation of biological tissue in endoscopic applications. BACKGROUND

[0002] Endoscopic useable instruments for argon plasma coagulation are essentially known. WO 2008 / 090004 A1 discloses such an instrument having a flexible hose and two electrodes arranged therein between which an optical arc can be ignited. The hose-like instrument comprises one or two lumens, wherein in the variant with two lumens an outer probe hose and two inner hoses are provided in which the two lumens are formed. Each lumen is assigned to one of the two electrodes. The respective electrode is connected with a conductor which extends over the entire length of the instrument without its own insulation through the lumen assigned to it. The electrodes are held centrally in the gas outlet openings of the respective lumen. The outer probe hose thus comprises an elliptical cross-section.

[0003] From WO 2006 / 119892 A1 a multi-lumen instrument is known in which in the probe hose a further hose is arranged concentrically in which an electrode is held. In order to support it in the inner hose it comprises a helically wound section by which it is supported at the inner wall of the inner hose. In order to fasten the inner hose in the center of the outer hose a radially oriented spacer is provided.

[0004] Furthermore, from EP 3205301 B1 a bipolar instrument is known. The instrument comprises a probe hose with a lumen and two electrodes embedded in the probe hose. When one of the electrodes is provided with a metal ring on a ceramic sleeve, the other electrode is centrally located in a central passage of the ceramic sleeve. The ceramic sleeve forms an electrical insulator so that an electrical barrier discharge is formed inside it and thus a non-thermal plasma.

[0005] From EP 0353177 A1 a manual instrument is known which provides open surgery, which instrument comprises at its distal end an outlet channel and an electrode arranged therein. The line for the gas supply for this manual instrument comprises a plurality of lumens.

[0006] Further prior art is formed by EP 0738519 A1, JP 2002-301088 A and EP 3412234 A1.

[0007] Probes for generating thermal plasmas are subjected to significant thermal stress, which limits the design of such probes. Furthermore, high voltages are necessary for plasma generation, which requires a large wall thickness of the probe hose in order to achieve the necessary dielectric strength. The geometrical design of the probe must take this into account and, due to the usual design, this often leads to an interference with the stiffness of the probe. SUMMARY

[0008] It is therefore an object of the present invention to provide a basic concept for an instrument that allows an extended design possibility.

[0009] This object is solved by an instrument according to claim 1 :

[0010] The instrument according to the invention can be configured in particular as a monopolar instrument, which is suitable for plasma coagulation, in particular argon plasma coagulation of biological tissue. The instrument is a particularly flexible probe. The electric current flows between the (preferably single) electrode of the instrument and the biological tissue in the plasma formed at or out of the distal end of the probe.

[0011] The instrument (probe) comprises a probe hose, which comprises at least two, preferably three or more lumens that can be connected to a gas supply device. These lumens extend preferably from the proximal end through the entire probe hose to gas outlet openings located at the distal end. Preferably, no current-conducting elements or electrical conductors or electrodes are arranged in any of these lumens.

[0012] At the distal end of the probe hose, an electrode is preferably arranged centrally, whose active end is exposed, in the region of which there is no electrical insulation. The active end of the electrode is the section thereof that comes into contact with the gas stream exiting the gas outlet openings and ionizes this gas stream. The active end of the electrode can thus reach significant temperatures of up to several hundred °C. The gas outlet openings are grouped around the electrode.

[0013] Due to the multi-lumen configuration of the probe hose, the probe hose typically comprises an outer hollow cylindrical section, a approximately cylindrical hub or central section, which is preferably arranged concentrically therein, and flat partition walls, which are preferably arranged in the manner of spokes, therebetween. Preferably, each partition wall comprises a substantially constant thickness from the central section to the outer section. Preferably, the thickness varies by less than 20%. The central section, the partition walls and the outer hollow cylindrical section are preferably parts of the same plastic hose composed of the same material and seamlessly transition into one another. A high electrical insulation capability and a high flexibility are achieved. Such a hose allows an extension with small radii.

[0014] The electrical insulation originates radially outward from the conductor, which is provided first and predominantly by the central section. The radius of the central section is preferably equal to or greater than the outer wall section of the hose.

[0015] Maximizing the diameter of the central section hardly influences the flexibility of the probe hose, since the central section contributes little to the bending stiffness of the probe. In contrast, the outer hollow cylindrical sheath can be configured in a relatively thin-walled manner. In this way, a fluid channel can be produced despite the high insulation capacity provided by the central section comprising a large free-flowing cross section.

[0016] The probe hose can be made of a plastic (e.g. a fluoroplastic, in particular PTFE and FEP) having a lower dielectric strength and / or comprising a higher modulus of elasticity than the material originally used for argon plasma probes.

[0017] A metallization or a metal inlay can be provided for the central section at its outer side and / or for the sheath section at its inner side in order to produce an equipotential surface. Likewise, the dielectric strength of the probe hose can thereby be further increased.

[0018] However, it is preferred that the radial thickness of the central section is dimensioned larger than the radial thickness of the sheath section, so that the electrical insulation is mainly provided by the central section.

[0019] The gas outlet openings are preferably arranged concentrically around the electrode. The partition walls arranged between the lumen of the probe hose can be inclined with respect to the radial direction. Thus, preferably not all partition walls are inclined in the same direction. The lumina can have a substantially triangular cross section with curved edges (two convex and one concave). In addition to sharp edges, curves can also be provided. Each of the above measures individually contributes to the probe hose having the same flexibility and being equally insensitive to the closure of the gas guiding lumina in all radial directions due to bending the probe hose. The partition walls inclined with respect to the radial direction also contribute to the flexibility of the probe hose and also lead to a uniform gas flow around the electrode.

[0020] Since the curvature of the partition walls manifests itself in the cross section as a curvature around an axis orthogonal to the cross-sectional plane, the flexibility of the probe hose is supported and the electrical insulation strength is also particularly guaranteed at the bending location of the probe hose. The partition walls are placed during bending the probe hose between the central section and the sheath section and increase the breakdown field strength. This is to the benefit of the dielectric strength.

[0021] In addition to this, a conductor which is not additionally insulated can be embedded in the central section of the probe hose, which is thereby electrically insulated. However, instead of a non-insulated conductor, an insulated conductor can also be embedded in the central section, so that this electrical conductor is surrounded by a multilayer insulation consisting of different materials. This can also be used for improving the electrical insulation, or vice versa, for miniaturization of the probe design. The conductor can be a wire or braid of metal or conductive plastic. The multilayer configuration of the insulation is a concept with which the variety of materials which can be used for the probe hose can be increased. For example, the central section can consist of a material which is optimized in terms of its electrical insulation capability, while the sheath section (and / or the partition wall) consists of a material which is optimized in terms of its flexibility.

[0022] The probe hose preferably comprises a constant cross section from the proximal end up to the gas outlet opening. The gas guide lumen can be arranged straight, parallel to the central axis, or can also have a helical extension.

[0023] The sheath section can extend beyond the gas outlet opening in the distal direction, so that a plasma chamber is formed at the distal end of the instrument, into which the distal end of the electrode lies. The sheath section can consist of the material of the probe hose. However, it is also possible to manufacture the end section which surrounds the plasma chamber from a different material, for example ceramic.

[0024] Furthermore, the electrode can also protrude out of the probe hose and be provided with a protection body at its free distal end. The protection body is preferably an electrically insulating body, for example a ceramic body, for example a ceramic ball or any other body. Preferably, the diameter of this protection body is significantly greater than the electrode diameter and, for example, approximately coincides with the outer diameter of the probe hose. The protection body is preferably rounded at its distal end surface and has no sharp ends or sharp edges. This concept is particularly suitable for radial probes which are able to output a plasma jet in any radial direction. In the case of an asymmetric configuration of the protection body, for example in the form of a ceramic disc which is oriented obliquely or the like, it is also possible to define a radial direction for the preferred plasma output.

[0025] The electrode can be configured at its end section as a bare wire end. For example, the wire can consist of chrome-nickel steel, which has poor thermal conductivity and thus introduces low heat in the central section of the probe hose, where it is in direct contact with the plastic of the probe hose. It is also possible to provide the electrode with a coating, which extends along the total length or at least in its distal end section, for example in the active end section, through the wire of the probe hose. The coating is preferably made of an electrically conductive material. Preferably, this material is a metal, which has a lower melting temperature than the electrode. For example, the coating can be made of silver or a silver alloy. It is also preferred that a further layer, for example an adhesive layer, for example in the form of a gold layer, can be provided between the base material of the electrode, for example chrome-nickel steel, and the low-melting coating. Such an electrode is stable and transfers less heat in the probe hose. Due to the coating and the lower thermal stress achieved thereby, it is now possible to attach the electrode directly in the probe hose. For example, the plate electrodes or needle electrodes with spiral base used hitherto have achieved enhanced cooling by convection and the discharge zone being spaced apart from the hose by a certain distance. In the present invention, both can be dispensed with, whereby a configuration of a flexible and miniaturized probe becomes possible.

[0026] Furthermore, it is also possible to provide an electrode extension on the distal end of the wire extending through the probe hose. It can be provided, for example, with the coating described above. BRIEF DESCRIPTION OF DRAWINGS

[0027] Further details of advantageous embodiments of the invention result from the dependent claims, the drawings and the associated description. The drawings show:

[0028] Figure 1 the instrument of the invention connected to a supply device in a schematic perspective view,

[0029] Figure 2 the distal end of the instrument in a perspective view,

[0030] Figure 3 the instrument in a front view, Figure 1 and 2 the instrument in a front view,

[0031] Figure 4 the instrument according to Figure 3 in a longitudinal section, which illustrates details,

[0032] Figure 5 a modified embodiment of the instrument according to Figure 4 in a longitudinal section, which illustrates details,

[0033] Figure 6 a further modified embodiment of the instrument according to Figure 4 in a longitudinal section, which illustrates details,

[0034] Figure 7A further embodiment of the inventive instrument is shown in a partial cross-sectional side view of the distal end,

[0035] Figure 8 and 9 the instrument with a modified probe hose is shown in a front view, respectively. DETAILED DESCRIPTION

[0036] Figure 1 A surgical instrument 10 in the form of a multi-lumen probe connected to a supply device 11 is shown. The multi-lumen probe can be used for the surgical treatment of a patient and can thus be introduced into the patient's body through a working channel of an endoscope. The device 11 serves to supply the instrument 10 with media and electrical current required for operation. For example, the device 11 can thus comprise a gas source 12 and a generator 13. The gas source 12 can be, for example, an argon gas source, which is formed from a gas stock, for example an argon stock, disposed in a pressure vessel, as well as corresponding control elements, such as valves, pressure regulators, etc. The generator 13 is preferably a radio frequency generator for outputting a radio frequency alternating voltage with a desired peak voltage, preferably with adjustable modulation and / or adjustable power.

[0037] The instrument 10 comprises a probe hose 14 extending from a proximal end 15 to a distal end 16. The probe hose 14 is a flexible hose, preferably composed of plastic, for example PTFE, FEP or also PA, TPE, HDPE or PP. As can be seen from the Figure 3 It is apparent that the probe hose 14 comprises a preferably circular cross section on the outer side. Alternatively, the cross section on the outer side can also be polygonal, for example hexagonal or octagonal. The cross section on the outer side is defined by a circular sheath 17, from the inner side of which a plurality of partition walls 18, 19, 20 extend to a hub-like central section 21 arranged in the center of the probe hose, preferably having a cylindrical outer surface. Preferably, there are an uneven number of partition walls, whereby a uniform stiffness, i.e. a stiffness equal in all radial directions, is produced. By means of the partition walls 18, 19, 20, at least two, preferably three or more, tube lumens 22-24 are partitioned from one another in the probe hose 14, which extend from the proximal end 15 to the distal end 16 or to gas outlet openings 25, 26, 27 disposed there, respectively, and are grouped around the central section. Depending on the material and the accuracy of the extrusion, the cross section of the outer surface and / or the cross section of the central section can also be defined as polygonal.

[0038] From Figure 4It is apparent that the gas outlet openings 25, 26 (and 27) are displaced rearward in the proximal direction relative to the end face of the probe hose 14, such that a chamber-like recess is formed on the distal end 16 of the probe hose 14. The active end 29 of the electrode 30 extends into this, in which the electrode 30 is held centrally in the central section 21. The chamber-like recess is a plasma chamber, in which the current from the electrode 30 is converted on the plasma to be formed.

[0039] In Figure 4 In the apparatus 10 shown for emitting an axial plasma jet, the active end 29 of the electrode 30 is arranged completely inside the apparatus 10 and thus in the plasma chamber. The tip of the active end 29 of the electrode 30 is therefore displaced rearward in the proximal direction relative to the end face 28 of the probe hose 14. The electrode can also lie in one plane with the end face of the probe hose 14.

[0040] From the electrode 30, an electrical conductor preferably extends centrally through the central section 21 up to the proximal end 15 in order to be connected there to the pole of the generator 13. The other pole of the generator 30 can be connected with a not shown neutral electrode, which can be attached to the patient in order to conduct the current back. The apparatus 10 is therefore a monopolar apparatus, in which the patient is part of the treatment current circuit.

[0041] The electrode 30 can be configured in one piece with the power supply line 31, which extends away in the proximal direction, and thus can be a part thereof. However, the electrode 30 can also be formed by a separate metal element, which is connected with the power supply line 31. Preferably, the electrode 30 consists of a material with a low thermal conductivity, such as, for example, stainless steel, in particular chrome-nickel steel, for example with the following composition:

[0042] Fe C Cr Mn P S Si Ni N Mo Min 0.05 16.0 6.0 Max 47.605 0.15 19.0 2.0 0.045 0.15 2.0 9.5 0.11 0.8 .

[0043] At least the active end 29 or also the entire electrode 30 can be provided with a coating. The coating can also extend over the entire length of the conductor 31. The coating is preferably a metal coating, which has a melting temperature which is lower than the melting temperature of the electrode 30 or of the active end 29, respectively. In particular, the coating can be formed by a silver layer. Between the silver layer and the electrode material or the active end 29 of the electrode 30, an adhesive layer can be provided. The adhesive layer is preferably composed of a material which has a melting temperature which is lower than the melting temperature of the electrode 30 or of the active end 29 thereof. Preferably, however, the melting temperature of the adhesive layer is at least as high as the melting temperature of the coating. The adhesive layer can be, for example, a gold layer.

[0044] In operation, the electrode 30 and the conductor 31 are subjected to high voltages, the amount of which can be in the range of several hundred to several thousand volts. For the electrical insulation of the conductor 31, the central section 21 comprises a thickness in the radial direction, which is preferably greater than the thickness of the sheath 17 to be measured in the radial direction. The central section 21, as well as the sheath 17, contribute to the electrical insulation of the conductor 31 with respect to the surrounding endoscope and / or the surrounding biological tissue. Due to the shown material strength profile in favor of the central section 21, a high flexibility of the probe hose 14 is obtained. In addition, the flow cross sections of the lumen 22, 23, 24 are as large as possible. If necessary, the radial thickness of the central section 21 can be increased significantly, for example, as shown by the dashed circle 32 in Figure 3 This significantly improves the electrical insulation of the conductor 31 without substantially affecting the flow cross sections of the lumen 22, 23, 24.

[0045] In order to further increase the flexibility and / or to equalize the bendability in all radial directions, and in order to avoid lumen closure during bending of the probe hose 14, the partition walls 18, 19, 20 can be configured in an inclined and also curved manner, as can be seen from Figure 3 If such a probe hose 14 is bent with a small bending radius, the partition walls 18, 19, 20 can rest against the central section 21 at the side of the bend, while the other partition walls 19, 20 can stand upright. Thus, always at least one, mostly two or three lumens are open so that the gas flow can flow freely in the distal direction. No bending of the probe hose 14 due to lumen blockage occurs.

[0046] The instrument 10 described so far is supplied with gas, for example argon, during operation, which flows through the lumens 22, 23, 24 parallel to one another and exits from the gas outlet openings 25-27. It flows around the electrode 30 or its active end 29, which ionizes the gas flow and thus generates a plasma flow that exits distally from the instrument 10, which impinges on the surrounding tissue. This is made possible by the aforementioned counter-pole connection of the neutral electrode to the generator 13, so that an electrical current is established between the active end 29 of the electrode 30 and the tissue.

[0047] Due to the combination of several measures, namely

[0048] - uniform gas flow from the outlet openings 25, 26, 27,

[0049] - coating of the electrode 30 with, for example, silver at least at the distal end,

[0050] - concentration of the electrical insulation in the center of the probe cross section,

[0051] The instrument 10 can be miniaturized to a large extent. The outer diameter of the probe hose 14 can be reduced to less than 1 mm without the heat emanating from the active end 29 of the electrode 30 causing a rapid damage of the probe hose 14. This is even the case if the wire- or rod-shaped electrode 30, i.e. preferably configured in a straight manner, is in two-dimensional contact with the probe plastic at the periphery. A rapid thermal damage of the probe hose is particularly avoided if the active end 29 is provided with a suitable coating causing the discharge to be concentrated to the distal end of the active end 29 of the electrode 30, such as, for example, the mentioned silver coating. Finally, a highly miniaturized probe is obtained which is very flexible and which offers hitherto unreached fields of application for argon plasma coagulation.

[0052] The structure formed in particular on the distal end 16 of the instrument 10 can be produced by the manufacturing method of the probe hose extruded on the conductor 31, in which method the partition walls 18, 19, 20 are subsequently introduced at the distal end 16 and from there Figure 4 the plasma chamber 33 is evident. For this purpose, the distal sections of the partition walls 18, 19, 20 and, if necessary, a part of the central section 21 are removed, for example mechanically. The electrode 30 can also be shortened slightly so that it does not protrude beyond the end face 28 of the probe hose 14. However, it is also possible to produce the plasma chamber 33 in which, during the first use on a patient or also by the manufacturer under controlled conditions, a brief operation is carried out on the already cut probe hose 14 so that the active section 29 of the electrode 30 melts or burns off a part of the partition walls 18, 19, 20 and the central section 21 due to thermal development. This process can be supported in which another suitable gas is used instead of argon (for example a reactive gas, such as C02, air, etc.).

[0053] Many modifications can be made on the described probe so far. For example, the walls 18, 19, 20 can tangentially adjoin the central section 21 as shown. However, they can also adjoin there radially and can then transition into an inclined orientation. The walls 18, 19, 20 can also tangentially adjoin the sheath 17. However, they can also adjoin there radially and separate there in an inclined orientation.

[0054] In all embodiments, the distal end 16 of the probe hose 14 can be provided with a sleeve-shaped element 35 made of a material different from the material of the probe hose 14. For this purpose, Figure 6The probe hose 14 is illustrated as an example, wherein the element 35 is formed by a ceramic sleeve. It can be connected to the probe hose 14 by means of a dull joint in the stepped joint or also on the conical interface. The connection can be implemented by means of gluing, welding, for example ultrasonic welding, or by other form- and / or substance-bonding connection techniques. The explanations given above apply correspondingly to the above-described embodiments with regard to the configuration and positioning of the electrode 30 and its active end 29.

[0055] However, in all of the above-described embodiments, the active end 29 of the electrode 30 can also protrude beyond the end face 28 of the probe hose 14, as is illustrated in Figure 7 It is apparent. In this case, the end of the electrode 30 can be provided with a protection body 36, for example in the form of an insulator, for example in the form of a ceramic element. The protection body 36 is preferably configured rotationally symmetrically with regard to the active end 29 of the electrode 30. For example, it is plate-shaped, pyramid-shaped, spherical, mushroom-shaped, etc. Preferably, it is configured such that all radial directions are free when viewed from the electrode 30. Thus, the plasma flow can be directed in any arbitrary radial direction over 360°. However, it is also possible to configure the protection body 36 asymmetrically and to combine or connect it with the element 35. In this way, a probe can be designed which operates asymmetrically.

[0056] The above-described description of the embodiments according to Figures 1-7 assumes that the conductor 31 is in direct contact with the material of the probe hose 14. However, in all of the above-described embodiments, it is also possible to provide a cable 37 instead of the bare conductor 31, the cable 37 consisting of the conductor 31 and a cable insulation 38 applied thereon. The cable insulation can be formed, for example, by an insulating lacquer or a plastic hose. The material of the probe hose 14 is applied on the cable insulation 38, such that the interior of the central section 21 consists of the material of the cable insulation 38 and the material of the probe hose applied on the cable insulation 38. With this concept, the safety against voltage breakdown can be further improved. The material of the cable insulation 38 can be optimized with regard to the maximum dielectric strength. Thus, the stiffness of the material plays a subordinate role. On the other hand, in this case, the material of the probe hose 14 can be optimized in terms of the desired flexibility.

[0057] In order to improve the dielectric strength at the boundary between the cable insulation 38 and the material of the probe hose 14 applied thereon, a metallization can be provided which defines a cylindrical equipotential surface. This can increase the dielectric strength.

[0058] Furthermore, as is illustrated in Figure 9 It is also possible to orient the partition walls 18, 19, 20 radially and thus to configure them straight or also curved.

[0059] The apparatus 10 according to the application comprises a probe hose 14, in the center of which a conductor 31 is provided for the supply of the electrode 30. Around the conductor 31 a plurality of gas guiding lumen 22, 23, 24 is arranged concentrically, which are isolated from one another by means of partition walls 18, 19, 20. The partition walls 18, 19, 20 support a central section 21, which is arranged centrally and accommodates the conductor 31, wherein the central section 21 decisively serves for the electrical insulation of the conductor 31. With this probe design, a particularly flexible and particularly thin probe with a particularly high dielectric strength can be produced.

[0060] List of reference signs:

[0061] 10 apparatus

[0062] 11 device

[0063] 12 gas source

[0064] 13 generator

[0065] 14 probe hose

[0066] 15 proximal end of the probe hose 14

[0067] 16 distal end of the probe hose 14

[0068] 17 sheath

[0069] 18 - 20 partition wall

[0070] 21 central section

[0071] 22 - 24 lumen

[0072] 25 - 27 gas outlet opening

[0073] 28 end face of the probe hose 14

[0074] 29 active end of the electrode 30

[0075] 30 electrode

[0076] 31 supply line

[0077] 32 circle for the improved electrical insulation of the line 31

[0078] 33 plasma chamber

[0079] 34 sleeve

[0080] 35 element

[0081] 36 insulator

[0082] 37 cable

[0083] 38 cable insulation

[0084] 39 Radially inner start of face 28

[0085] 40 Transition between end face 28 and outer surface.

Claims

1. A monopolar instrument, having a probe hose (14) comprising at least two lumens (22, 23) connectable to a gas supply device (12), having an electrode (30) supported in the probe hose (14) and comprising an active end (29), wherein each lumen (22, 23) comprises a gas outlet opening (25, 26), respectively, wherein a plurality of gas outlet openings (25, 26) are arranged in the vicinity of the active end (29) of the electrode (30), and a partition wall (18, 19) is arranged between the lumens, which on the inside adjoins a central section (21) and on the outside adjoins a sheath (17), and the electrode (30) is arranged in the central section (21) in an insulating manner, wherein the central section (21) of the probe hose (14) does not comprise a lumen for the passage of gas supplied from a gas supply device (12) therethrough, the central section and the partition wall extend substantially over the entire length of the probe hose (14), and the central section (21), the partition wall (18, 19) and the outer hollow cylindrical section are parts of one and the same plastic hose composed of the same material and seamlessly transition into one another, the gas outlet openings (25, 26) are arranged concentrically around the electrode (30), and wherein none of the lumens contains any electrically conductive element.

2. The apparatus of claim 1, wherein The central section (21) has a greater radial thickness than the sheath (17).

3. The apparatus of claim 1, wherein The partition wall (18, 19) is arranged in an inclined manner with respect to the radial direction.

4. The apparatus of claim 1, wherein The partition wall is configured in a curved manner.

5. The apparatus of claim 1, wherein The probe hose (14) has a circular cross-section on the outside.

6. The apparatus of claim 1, wherein Only one single electrode (30) is arranged in the probe hose (14), and the electrode (30) is arranged centrally in the probe hose (14).

7. The apparatus of claim 1, wherein The electrode is embedded in the central section (21) of the probe hose (14) in an electrically insulating manner.

8. The apparatus of claim 1, wherein The probe hose (14) comprises a sheath section (17, 35) which extends beyond the gas outlet openings (25, 26) in the distal direction.

9. The apparatus of claim 8, wherein, The sheath section (35) is composed of a different material than the probe hose (14).

10. The apparatus of claim 1, wherein The electrode (30) comprises a distal end arranged inside the probe hose (14).

11. The apparatus of claim 1, wherein The electrode (30) comprises a distal end arranged outside the probe hose (14) and provided with an insulator (36).

12. The apparatus of claim 1, wherein, The electrode (30) is formed by a bare end section of a wire which is embedded in the probe hose (14) along its entire length from the bare end section.

13. The apparatus of claim 12, wherein, The bare end section supports an electrically conductive electrode extension (34).

14. The apparatus of claim 1, wherein, The monopolar instrument is used for argon plasma coagulation of biological tissue.

15. The apparatus of claim 1, wherein, None of the lumens contains the electrode or an electrical conductor.

16. An apparatus according to any one of the preceding claims, characterised in that, The electrode (30) is at least partially provided with an electrically conductive coating. The monopolar instrument is used for argon plasma coagulation of biological tissue. None of the lumens contains the electrode or an electrical conductor. The electrode (30) is at least partially provided with an electrically conductive coating.

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