WO1997048446A1

WO1997048446A1 - A method and a probe for treatment of incontinence

Info

Publication number: WO1997048446A1
Application number: PCT/DK1997/000265
Authority: WO
Inventors: Lise Ebdrup
Original assignee: Inmedico ApS
Current assignee: Inmedico ApS
Priority date: 1996-06-18
Filing date: 1997-06-18
Publication date: 1997-12-24
Anticipated expiration: 1998-12-18
Also published as: AU3166397A

Abstract

The invention relates to a probe (1) for intrarectal or intravaginal treatment or monitoring. The probe (1) comprises means for determining the orientation of the probe in use in the form of a marking (5) on the handle (4) of the probe (1). The probe (1) thus allows a very specific treatment and monitoring of e.g. incontinence.

Description

A METHOD AND A PROBE FOR TREATMENT OF INCONTINENCE

Field of the invention

The invention relates to a method of treating inconti¬ nence as stated in the introductory portion of claim 1, and to a probe unit as stated in the introductory portion of claim 6.

GB-A-2 284 991 discloses an example of a probe for the treatment of urinary and anal incontinence. The probe is constructed in consideration of physiological parameters, so that the probe, when inserted in the vagina, assumes precisely one stationary position in accordance with physiological conditions.

This, as well as other known probes, however, has the drawback that the effectiveness is relatively poor m connection with the treatment of e.g. incontinence or the achievement of measurement results, as known probes can only be used for stationary stimulation and measurements, thereby providing a very uncritical stimulation or meas¬ urement of a relatively large muscular area. Thus, it is not possible to perform a more specific treatment or training of smaller muscular areas, as all muscles are stimulated at the same time.

Pelvic floor exercises have moreover been used for the treatment of incontinence in men and women, but not al- ways with the desired effect. Although the wish is there, it is not always possible to re-activate muscles which have not been trained sufficiently, or which have been damaged and subsequently have not been re-trained opti¬ mally. The object of the invention is to provide a probe which may be used for selective stimulation of individual mus¬ cular areas.

Summary of the invention

When, as stated in claim 1, the intrarectal or intravagi- nal measurement or stimulation of the probe electrode ar¬ rangement is adjusted by rotating the probe about its longitudinal axis in its intrarectal or intravaginal po¬ sition for the stimulation of selectively selected muscles or parts of muscles, it is ensured that intrarec¬ tal or intravaginal muscular activity may be treated or monitored selectively and precisely.

The arranged electrodes may thus be positioned with a relative reproducible orientation, thereby allowing mus¬ cular tissue to be stimulated and/or monitored selec¬ tively during the stimulation with relatively small elec- trical currents and voltages.

Thus, it will be possible to perform an orientation-de¬ termined identification and thereby a more specific de¬ termination of weak muscular parts. This identification may then form the basis for a specific stimulation of a determined weak muscular area.

A stimulation of a weak muscular area inter alia serves to "visualize" the physical position of the weak muscular area or areas (the position is sensed) , thereby enabling the patient himself to perform a selective re-training of the areas concerned.

Since the diagnosis as well as the treatment is very se- lective, a more efficient and thereby useful method of treatment is thus possible. When, as stated in claim 2, the stimulation is formed by bursts applied to the electrode with a frequency which is preferably 30-55 Hz, each individual burst comprising a signal with an internal frequency which is greater than twice the burst frequency, an optimum contraction is achieved as a function of the stimulation, as the burst frequency substantially corresponds to the natural fre¬ quency of the nerves.

When, as stated in claim 3, at least one additional elec¬ trode, arranged externally with respect to the probe, de¬ fines an associated current path in muscular tissue be¬ tween the probe electrode arrangements and the externally arranged electrode or electrodes, a good and controllable current path is provided between the external electrode or electrodes and the probe electrode/electrodes. Thus, a well-defined current path having a low contact impedance is provided, and a precise physiological effect is moreo¬ ver achieved.

It should also be noted that the method of the invention can provide a strong and specific useful signal between the intrarectal or intravaginal electrodes and the exter¬ nally arranged electrode or electrodes. While the posi- tion and dimensioning of two external electrodes are usually critical and sensitive to very small irregulari¬ ties of position and contact, the method of the invention is thus more insensitive to irregularities of position and contact in the sense that a correct position of the internal electrode is easy to achieve according to the invention.

The combination enables very specific stimulation not only of a very weak muscular part, but also of e.g. the front part and the rear part of the pelvic floor, respec¬ tively. The pelvic floor is difficult to "reach" partly because of location and partly because of function. It has a long extent, the only "carrying structure" being a muscle which is moreover subjected to the constant load of gravity.

The electrode may e.g. be positioned so that the current hits precisely a portion of or the entire anus, and the additional electrode is positioned exactly in the central line above the sacral roots 2-4. This results in a spe- cific training of the muscular part that is weakest, which is a requirement for the balance between the two parts of the levator muscle to be re-established.

When, as stated in claim 4, the physical extent of the current path between the probe electrode arrangement and the external electrode or electrodes is adjusted by changing the intrarectal or intravaginal position of the probe in longitudinal direction of the probe, an addi¬ tional degree of flexibility is achieved, permitting a three-dimensional specific treatment or monitoring.

When, as stated in claim 5, at least one of the external electrodes is positioned at the os sacrum or the os pu- bis, an effective method of the invention is achieved.

When, as stated in claim 6, the probe handle comprises at least one visible marking to indicate the orientation of the probe electrode arrangement with respect to the probe handle, it is possible to use the probe for a very selec- tive intravaginal or intrarectal stimulation and measure¬ ment of muscular activity, as a professional now has the possibility of determining the orientation of the elec¬ trode or electrodes of the probe unit and thereby of per¬ forming a very specific measurement or stimulation. It will thereby also be possible for a professional or a pa¬ tient himself to perform this selective treatment of weak muscular areas without any risk that, by mistake, the probe electrodes touch the urinary tracts and thereby cause strong and non-desired pain to the patient. Thus, the probe unit makes it possible to achieve very selec- tive and reproducible treatment results and monitoring signals, which are two very important factors in connec¬ tion with an effective and successful treatment of e.g. incontinence.

It is preferred most frequently to mark the actual posi¬ tion of the electrode or electrodes, but it should be noted that it is within the scope of the invention to construct the electrode with a single reference point which identifies the relative position of electrode or electrodes.

When, as stated in claim 7, the marking or markings com¬ prise a colour or bar marking on the probe handle, a simple embodiment of the invention is achieved.

When, as stated in claim 8, the marking or markings com¬ prise a visible depression or elevation in the probe handle, a likewise simple and advantageous embodiment of the invention is achieved. Such a marking may thus be sensed by the hand, so that the specific position of electrodes may be indicated without required visual at¬ tention, thereby allowing a professional to devote more attention to the palpation itself.

Another advantage of making a direct physical marking is that this is relatively insensitive to cleaning in e.g. autoclave.

When, as stated in claim 9, the probe nit comprises a de- pression which, as a minimum, extends from a starting point on the probe itself to a termination point on the probe handle, it is possible to use the probe for simul¬ taneous stimulation and palpation, as a finger may be placed in the depression so that the contraction level of the individual muscular parts may be sensed in response to a stimulation applied to the electrodes.

It will hereby be possible to identify the weak muscular parts with the probe and also possible to re-train these areas with electrical stimulation.

In use, the simultaneous stimulation and palpation may thus be performed with minimum discomfort for the patient as the finger is placed in the depression.

This enables a professional to register a result of the directionally orienting stimulation action during simul¬ taneous rotation and stimulation.

Known probes have the drawback that a professional has no possibility of currently following the result of the treatment, primarily because they do not permit palpa¬ tion, which is the common method of examining the func¬ tion of the muscular tissue, irrespective of the posi¬ tions of the muscles. Nor does the use of known probes allow palpation during stimulation.

This means that first palpation and then stimulation are performed, which causes considerable uncertainty as to where the stimulation is directed.

Not is it possible to observe an improvement, if any, as it can just be observed from the outside that the probe possibly moves, and not whether there is an actual muscu¬ lar response from the area which is to be stimulated. A weak pelvic floor may be regarded as a bone which has been in plaster for a long time; many muscular fibres have been inactive, i.e. atrophied. These may be re-acti¬ vated by means of electrical stimulation as they have a full nerve supply.

Vaginally, it must be known with certainty that precisely the atrophied area is stimulated, as the muscle cannot be seen from the outside. This can only be done by simulta- neous palpation and stimulation. It is so that the area of most pronounced atrophy will give the smallest palpa¬ tion response, and the stimulation must therefore be pal^¬ pated and directionally determined.

When, as stated in claim 10, the probe handle comprises a completely or partly encircling flange which adjoins the probe, a particularly advantageous embodiment of the in¬ vention is achieved, since the flange permits exact and reproducible positioning of the probe in its longitudinal direction in its position of use.

This advantage will be even more distinct in use when the probe is to be rotated about its axis. A rotational im¬ pact will thus not cause the position of the probe unit to be changed in its longitudinal direction.

It will be appreciated in this connection that the flange is considered to be part of the probe handle in the sense that a marking or drawing of the annular positions of the electrodes may also be made on the flange itself within the scope of the invention.

When, as stated in claim 11, the probe additionally com¬ prises at least one EMG sensor which is connected to measurement or monitoring equipment via electrical con- nections, it will be possible to reproduce the current muscular response electronically.

Monitoring may be reproduced e.g. visually or with audio signals and/or video signals.

When, as stated in claim 12, the measurement or monitor¬ ing equipment is external, an advantageous embodiment of the invention is achieved.

When, as stated in claim 13, the electrodes on the probe are replaceable, it is possible to mount electrodes on the probe which are optimized for the contemplated use. Thus, with the same probe, it will be possible to perform an optimized treatment or monitoring with different sizes and shapes of the electrodes.

When, as stated in claim 14, the probe comprises means for adjusting the length of the electrode area in the longitudinal direction of the probe, it is possible to perform a reproducible treatment and monitoring which is specific in the longitudinal direction of the probe.

These means might e.g. comprise an adjustable flange which is movable with respect to the handle of the probe and/or the probe itself.

When, as stated in claim 15, the probe comprises means for adjusting the probe or electrode diameter, an addi- tional possibility of adjusting the probe in the longitu¬ dinal direction is achieved.

When, as stated in claim 16, the flange of the probe is slidable in the longitudinal direction of the probe, a simple means for providing a distinct and reproducible position of the probe electrode arrangement in the longi¬ tudinal direction of the probe is achieved.

When, as stated in claim 17, the electrode arrangement of the probe is asymmetrical with respect to the cross-sec¬ tion of the probe, a simple directionally oriented probe electrode arrangement is achieved.

When, as stated in claim 18, the electrode arrangement is formed by precisely one longitudinal electrode, a par¬ ticularly advantageous embodiment of the invention is achieved, which may be used in a simple manner for a di¬ rectionally oriented muscular stimulation. The embodiment is also economically advantageous and simple, since the probe electrode is relatively simple to manufacture rela¬ tive to more complicated probe electrode arrangements. An additional advantage of such a simple embodiment is achieved in the sense that the necessary cleaning of the probe may take place on a simple and compact probe.

When, as stated in claim 19, the exact position and ex¬ tent in an annular direction of the electrode arrangement is shown by a visual marking on the probe handle, a par¬ ticularly advantageous embodiment of the invention is achieved, since a professional or a user will thereby know with complete certainty how the electrode or elec¬ trodes are oriented, although the probe unit is placed in the anus or the vagina.

This makes it possible to perform continuos and repro¬ ducible treatments.

Drawings

The invention will be explained below with reference to the drawings, in which figs, la-c show a probe unit according to the inven¬ tion,

figs. 2a-c show a preferred embodiment according to the invention,

figs. 3a-c show a probe unit with an EMG sensor ac¬ cording to the invention, and

figs. 4a-c show a probe unit with two palpation de¬ pressions according to the invention.

Example

Fig. la shows a probe unit according to the invention.

The probe unit comprises a probe 1 with a handle 4, said probe 1 being provided with an electrode 2. The probe unit is provided with a flange 3 between the electrode 2 and the handle 4, and the probe is additionally provided with a longitudinal depression 6 with respect to the un¬ interrupted circumference, said depression 6 extending from the handle 4 through the flange 3 and into the probe 1 itself.

It will be seen that the depression extends from a start¬ ing point 6" on the probe itself 1 through the flange 3 to a termination point 6' in the probe handle 4.

The electrode 2 is electrically connected to at least one output terminal (not shown) .

Figs, lb and lc are end views of the probe unit seen from the handle side and the probe side, respectively. 97/48446 11 PC1YDK97/00265

It will thus appear that the probe 1 has a transverse section which forms the depression 6.

The probe unit is provided with a visual colour marking 5 on the handle 4. This colour marking might also be made as a colour marking which marks the entire annular extent and position of the electrode.

The probe unit is also provided with an electrical con- nection 8 on the handle 4.

When the probe unit is provided with a visual marking 5, stimulation of delicate structures, such as the urinary tracts, may be avoided, and it is possible to perform a reproducible treatment of the individual weak muscular structures .

The "shallow" depression 6 also allows palpation during stimulation so that the treatment result may be opti- mized, as a professional can thereby ensure that stimula¬ tion is performed to a sufficient contraction level, and that specifically the weakest muscles are stimulated.

Fig. 2a shows a preferred embodiment of a probe unit ac- cording to the invention.

The probe unit comprises a probe handle 4 and a probe 1 with an electrode 2. The probe unit is provided with a flange 5 between the electrode 2 and the handle 4, and the probe is additionally provided with a longitudinal downward depression 6 which extends from the handle 4 through the flange 3 and into the probe 1 itself. The electrode 2 is electrically connected to at least one output terminal (not shown) . The depression 6 extends from a staring point 6" on the probe 1 itself through the flange 3 to a termination point 6' in the probe handle 4.

Figs. 2b and 2c are end views of the probe 1 seen from the handle side and the electrode side, respectively.

It will thus appear that the probe 1 has a transverse downwardly rounded section which forms the depression 6.

The probe unit is provided with a visual colour marking 5 on the handle 4.

As will be seen from fig. 2, the probe has a depression 6 which gives the palpation advantages and possibilities corresponding to fig. 1 and, because of the shape, addi- tionally ensures minimum discomfort for the patient.

Fig. 3 shows a probe unit according to the invention.

The probe unit comprises a handle 4 with a probe 1, said probe being provided with an electrode 2. The probe unit is provided with a flange 5 between the electrode 2 and the handle 4, and the probe unit is additionally provided with a longitudinal depression 6 relative to the uninter¬ rupted circumference, said depression 6 extending from the handle 4 through the flange 3 and into the probe 1 itself. The depression 6 additionally contains an EMG sensor 7.

It will be appreciated that the depression may contain several EMG sensors at the same time. The electrode 2 and the EMG sensor are electrically con¬ nected to at least one output terminal (not shown) .

It will be seen that the depression extends from a start- ing point 6" on the probe 1 itself through the flange 3 to a termination point 6' in the probe handle 4.

Figs. 3b and 3c are end views of the probe unit seen from the handle side and the electrode side, respectively.

The probe unit is provided with a visual colour marking 5 on the handle 4.

The probe unit is also provided with an electrical con¬ nection 8 on the handle 4.

The EMG sensor 7 makes it possible to take a monitoring signal for the intrarectal or intravaginal muscular ac¬ tivity according to various guidelines and for various possible purposes.

A typical sensor will convert a force on the sensor into a corresponding electrical signal, with automatic and se¬ lective determination of the muscular activity. This sig¬ nal may then be converted additionally into other target figures, if this should be desired. An example of such a target figure may be latency period measurement.

Fig. 4a shows a probe unit according to the invention.

The probe unit is constructed as a probe 1 with a handle 4, said probe comprising an electrode 2. The probe unit is provided with a flange 5 between the electrode 2 and the handle 4, and the probe unit is additionally provided with two longitudinal depressions 6 relative to the unin¬ terrupted circumference, said depressions extending from the handle 4 through the flange 3 and into the probe 1 itself.

It will be seen that the depressions 6 extend from a starting point 6" on the probe 1 itself through the flange 3 to a termination point 6' in the probe handle 4.

Figs. 4b and 4c are end views of the probe unit 1 seen from the handle side and the electrode side, respec¬ tively.

It will thus appear that the probe 1 has two transverse sections which form the depressions 6.

The probe unit is provided with a visual colour marking 5 on the handle 4.

The probe is also provided with an electrical connection 8 on the handle 4.

As a common denominator for all the probes shown, the longitudinal depressions 6 may be used for palpation pur¬ poses, as a professional may place a finger in the de- pression and thereby achieve a simultaneous stimulation and palpation. The preferred embodiment is the structure shown in fig. 2, as the depression in this probe is shaped as a downwardly extending depression which allows the palpation finger to be placed ergonomically in the probe. It has thus been found that an ergonomical shape is particularly advantageous, as this results in minimum discomfort for the patient in use and provides an optimum palpation quality, since the palpation area, i.e. the touched tissue, is tensioned minimally by the palpation finger.

The invention thus makes it possible to use an electrode placed directly on the muscles which are to be stimulated

(musculus levator ani) , and an external electrode placed over the nerve which feeds the pelvic floor muscle where this is closest to the skin (above the sacral roots of the nervus pudendus corresponding to the foramina sacra- lia posterioria, sacral roots 2-4) . This opens up the possibility of providing an efferent action on the cen¬ tral branches of the nervus pudendus, which, when emerg- ing from the foramina sacralis anteriora, twist around the spina ischiadica and then run through the foramen is- chiadica minus. It has the following branches: nn. rec- tales, nn. perineales and n. dorsalis penis and clitoris, respectively. The nerve is predominantly a motor nerve and feeds all muscles in the minor pelvis.

In case of urge incontinence, the external electrode is placed over the os pubis corresponding to the position of the bladder; with the vaginal electrode placed on the le- vator ani, the afferent impulses will go directly through the bladder and then run through the sacral reflex arc.

In terms of position, e.g. the following possibilities exist within the scope of the invention:

Probe vaginally + sacrally: With this stimulation the current may be directed toward possibly weak muscles rearwardly in the pelvic floor, the sacral electrode be¬ ing used as an indifferent electrode. Probe vaginally + os pubis: With this stimulation it is possible to stimulate weak areas forwardly in the pelvic floor (the front loop) . Cathode placed vaginally, anode over the os pubis.

Probe anally + sacrally: Directionally determined par¬ ticularly in connection with anal incontinence.

Probe anally + os pubis: If position in the vagina is compromised, or where the insufficiency is on the rear wall of the vagina.

Probe with two electrodes vaginally + os pubis + os sa¬ crum: Here, each of the electrodes placed on the vaginal probe forms a circuit having an external electrode of its own. May be used if one of the above-mentioned combina¬ tions is not sufficient. This combination is particularly useful in case of very large vaginal/anal spaces.

Finally, a single probe may be placed vaginally and a single probe anally, thereby creating a larger circuit m the muscle than by using a vaginal position of both elec¬ trodes (cf. the stimulation physiology saying that the more the electrodes are spaced, the deeper the stimula- tion penetrates down into the tissue) .

The rationale of electrical stimulation inter alia for re-traming as old known technique is to provide an af¬ ferent impulse via surface electrodes which, via the lim- bic system, causes an efferent action on the organ/organs in whose vicinity the surface electrodes are positioned. The action is to produce a physiologically supermaximum muscular contraction, which is achieved m that the pro¬ tein chains in the individual muscular fibres turn so that the contact points of ATP are visible. No matter whether the contraction is natural or produced electri- cally, this process is brought about in that the poten¬ tial over the muscular cell membrane changes upon activa¬ tion of the sodium/potassium pump.

The electrodes may be replaceable and thereby be opti¬ mized for the actual physical use relative to e.g. size and the desired measurement or stimulation.

The colour marking mentioned in the examples may alterna- tively be made as a visible or sensible recess or eleva¬ tion according to the invention.

The electrical stimulation is provided by bursts applied to the electrode with a frequency which is preferably 20- 60 Hz, each individual burst comprising a signal with an internal frequency which is greater than twice the burst frequency.

Thus, an additionally optimized contraction as a function of stimulation is achieved, and the burst frequency sub¬ stantially corresponds to the natural frequency of the nerves .

A typically used pulse train will be applied with a cur- rent of 40 to 70 mA and with a voltage of up to 100 volts, and the discomfort for the patient may therefore be minimized according to the invention.

It should also be noted that the method and the probe of the invention may advantageously be used for the treat¬ ment and monitoring of anal incontinence.

Known probes have the drawback that a professional has no possibility of currently following the result of the treatment, primarily because they do not permit palpa¬ tion, which is the common method of examining the func- tion of the muscular tissue, irrespective of the posi¬ tions of the muscles. Not does the use of known probes allow palpation during stimulation.

This means that first palpation and then stimulation are performed, which causes considerable uncertainly as to where the stimulation is directed.

Nor is it possible to observe an improvement, if any, as it can lust be observed from the outside that the probe possibly moves, and not whether there is an actual muscu¬ lar response from the area which is to be stimulated.

A weak pelvic floor may be regarded as a bone which has been in plaster for a long time; many muscular fibres have been inactive, i.e. atrophied. These may be re-acti¬ vated by electrical stimulation as they have a full nerve supply.

Vaginally, it must be known with certainty that precisely the atrophied area is stimulated, as the muscle cannot be seen from the outside. This can only be done by simul¬ taneous palpation and stimulation. It is so that the area of most pronounced atrophy will give the smallest palpa- tion response, and the stimulation must therefore be pal^¬ pated and directionally determined.

Claims

P a t e n t C l a i m s

1. A method for intrarectal or intravaginal measurement or stimulation of muscular activity with a probe (1) com- prising a probe electrode arrangement with one or more associated electrical connection terminals and a probe handle (4), c h a r a c t e r i z e d in that the in¬ trarectal or intravaginal measurement or stimulation of the probe electrode arrangement is adjusted selectively by rotating the probe (1) about its longitudinal axis in its intrarectal or intravaginal position for the stimula¬ tion of selectively selected muscles or parts of muscles.

2. A method according to claim 1, c h a r a c t e r - i z e d in that the stimulation is formed by bursts ap¬ plied to the electrode with a frequency which is prefer¬ ably 30-55 Hz, each individual burst comprising a signal with an internal frequency which is greater than twice the burst frequency.

3. A method according to claim l or 2, c h a r a c ¬ t e r i z e d in that at least one additional electrode, arranged externally with respect to the probe, defines an associated current path in muscular tissue between the probe electrode arrangement and the externally arranged electrode or electrodes.

4. A method according to claims 1-3, c h a r a c t e r ¬ i z e d in that the physical extent of the current path between the probe electrode arrangement and the external electrode or electrodes is adjusted by changing the in¬ trarectal or intravaginal position of the probe (1) in the longitudinal direction of the probe.

5. A method according to claims 1-4, c h a r a c t e r - i z e d in that at least one of the external electrodes is placed at the os sacrum or the os pubis.

6. A probe unit comprising a probe (1) with a probe handle (4) for intrarectal or intravaginal measurement or stimulation of muscular activity, said probe (1) compris¬ ing a probe electrode arrangement with one or more asso¬ ciated electrical terminals, said probe electrode ar¬ rangement comprising at least one electrode placed on the probe, c h a r a c t e r i z e d in that the probe handle (4) comprises at least one visible marking (5) to indicate the orientation of the probe electrode arrange¬ ment with respect to the probe handle (4) .

7. A probe unit according to claim 6, c h a r a c ¬ t e r i z e d in that the marking or markings comprise a colour or bar marking on the probe handle (4) .

8. A probe unit according to claim 6 or 7, c h a r a c - t e r i z e d m that the marking or markings comprise a visible depression or elevation m the probe handle (4) .

9. A probe unit according to claims 6-8, c h a r a c ¬ t e r i z e d m that the probe unit comprises a depres- sion (6) which, as a minimum, extends from a starting point (6") on the probe (1) itself to a termination point (6') on the probe handle (4) .

10. A probe unit according to claims 6-9, c h a r a c - t e r i z e d in that the probe handle (4) comprises a completely or partly encircling flange (3) which adjoins the probe (1) .

11. A probe unit according to claims 6-10, c h a r a c - t e r i z e d in that the probe (1) additionally com¬ prises at least one EMG sensor (7) which is connected to measurement or monitoring equipment via electrical con¬ nections .

12. A probe unit according to claims 6-11, c h a r a c - t e r i z e d in that the measurement or monitoring equipment is external.

13. A probe unit according to claims 6-12, c h a r a c ¬ t e r i z e d in that the electrodes (2) on the probe are replaceable.

14. A probe unit according to claims 6-13, c h a r a c ¬ t e r i z e d in that the probe also comprises means for adjusting the length of the electrode area in the longi- tudinal direction of the probe.

15. A probe unit according to claims 6-14, c h a r a c ¬ t e r i z e d in that the probe comprises means for ad^¬ justing the probe or electrode diameter.

16. A probe unit according to claims 6-15, c h a r a c ¬ t e r i z e d in that the flange (3) of the probe unit is slidable in the longitudinal direction of the probe unit .

17. A probe unit according to claims 6-16, c h a r a c ¬ t e r i z e d in that the electrode arrangement of the probe unit is asymmetrical with respect to the cross-sec¬ tion of the probe.

18. A probe unit according to claims 6-17, c h a r a c ¬ t e r i z e d in that the electrode arrangement is formed by precisely one longitudinal electrode (2) .

19. A probe unit according to claims 6-18, c h a r a c t e r i z e d in that the exact position and extent of the electrode arrangement is shown by a visible marking (5) on the probe handle (4) .