ENDOTRACHEAL TUBE FOR INTRA-OPERATIVE NEUROMONITORING

Abstract

The present invention relates to endotracheal tubes for intra-operative monitoring of nerve and muscle tissue (neuromonitoring), a system for intra-operative neuromonitoring, a method for deriving stimulus responses in intra-operative neuromonitoring, and a method for classifying tissue types, having the purpose of preventing damage to nerves and muscles which run within the area of operation.

Claims

1. Endotracheal tube (1a) for intra-operative neuromonitoring, comprising: a tube (2) of substantially circular cross-section configured to be inserted into a trachea of a patient; a fixation element (3) configured, when the tube (2) is inserted into the trachea of the patient, to fix the tube (2) in the trachea; and at least two electrodes (4) configured as stimulating electrodes (4a) for electrically stimulating tissue or as deriving electrodes (4b) for deriving stimulus responses from tissue, or configured as combination electrodes (4c) for electrically stimulating tissue and deriving stimulus responses from tissue, and forming at least one electrode array (5) which is arranged at a predefined array distance from a distal end of the tube (2) on the tube outer side and completely surrounds the tube outer side, wherein the at least two electrodes (4) are arranged in the at least one electrode array (5) such that they are at a predefined electrode spacing from their respective adjacent electrode (4) and are substantially parallel to each other and are circular over 360° [degrees] around the tube (2); wherein the at least two electrodes (4) extend axially or circularly in a predefined range along the tube (2); and wherein the endotracheal tube (1a) comprises: either at least two stimulation electrodes (4a) and at least two conduction electrodes (4b); or at least two combination electrodes (4c); wherein the electrode array (5) is divided into at least two sub-arrays (5a, 5b, 5c); and wherein the sub-arrays (5a, 5b, 5c) are arranged such that each has a predefined sub-array spacing to its adjacent sub-array (5a, 5b, 5c).

2.-4. (canceled).

5. Endotracheal tube (1a) according to claim 1, further comprising at least one lining (6) associated with at least one of the at least two electrodes (4) and having elasticity in radial direction, wherein the at least one lining (6) is attached to an underside of the at least one electrode (4) and supports the at least one electrode (4) on the tube exterior such that, under the influence of force in the radial direction, the at least one lining (6) is elastically deformed, and wherein the at least one electrode (4) can be displaced in the radial direction and, when the force is removed, the at least one lining (6) can deform back and the at least one electrode (4) can be displaced back.

6. Endotracheal tube (1a, 1b) according to claim 1, wherein the lining comprises a foam structure (6a) and/or a spring element (6b) and/or an elastic balloon (6c) filled with a gas or gas mixture.

7. Endotracheal tube (1a, 1b) according to claim 1, wherein at least one of the electrodes (4) or at least one of the paddings (6) with the corresponding at least one electrode (4) is fully integrated into the tube (2), and/or wherein at least one of the electrodes (4) or at least one of the paddings (6) with the corresponding at least one electrode (4) is formed as an adhesive electrode (9) and is attached to the tube exterior, and/or wherein at least one of the electrode arrays (5) is formed as an electrode sleeve and is attached tangentially around the tube outer side.

8. Endotracheal tube (1a, 1b) according to claim 7, wherein the at least one adhesive electrode (9) and/or the at least one electrode cuff comprises a distance indicator (9.2) which is formed to indicate the optimum distance of the at least one adhesive electrode (9) and/or of the at least one electrode cuff to the distal end of the tube (2) or to the fixation element (3).

9. Endotracheal tube (1a, 1b) according to claim 1, further comprising: an optics (12) configured to visually check the position of the endotracheal tube (1a, 1b) in a trachea and to visually check the vocal cords and their movement.

10. System (20) for intra-operative neuromonitoring, comprising: an endotracheal tube (1a, 1b) according to claim 1, wherein at least one electrode (4) is configured as a stimulating electrode (4a) for electrically stimulating tissue, or is configured as a combination electrode (4c) for electrically stimulating tissue and deriving stimulus responses from the tissue; and at least one separate conduction electrode (14) configured to be attached on the patient in proximity to the stimulated tissue and to derive stimulation responses from the stimulated tissue.

11. System (20) according to claim 10, further comprising: at least one counter electrode (15) configured to be externally attached to a patient, and configured to stimulate, in combination with the at least one stimulation electrode (4a) or the at least one combination electrode (4c), the tissue in a monopolar manner.

12. System (10) according to claim 10, wherein the at least one counter electrode (15) is formed as a needle electrode or as a surface electrode, and is formed to stimulate tissue subcutaneously or transcutaneously in combination with the at least one stimulation electrode (4a) or the at least one combination electrode (4c).

13. Method for deriving stimulus responses in intra-operative neuromonitoring comprising an endotracheal tube, the method comprising the steps of: electrically stimulating (S1) tissue by means of at least one stimulation electrode (4a) or at least one combination electrode (4c) of the endotracheal tube (1a, 1b); and deriving (S2) a stimulus response of the stimulated tissue by means of at least one conduction electrode (4b) or at least one combination electrode (4c) of the endotracheal tube (1a, 1b), or by means of at least one separate conduction electrode (14) of the system (20).

14. Method according to claim 13, wherein the step of electrically stimulating (S1) of tissue is additionally performed by means of at least one counter electrode (15) of the system (20).

15. Method according to claim 13, wherein the step of electrically stimulating (S1) is performed in a monopolar fashion by means of the at least one stimulation electrode (4a) or the at least one combination electrode (4c) of the endotracheal tube (1a, 1b) and the at least one counter electrode (15) of the system (10), is performed in a bipolar fashion by means of at least two stimulation electrodes (4a) and/or combination electrodes (4c) of the endotracheal tube (1a, 1b), or is performed in a multipolar fashion by means of multiple stimulation electrodes (4a) and/or combination electrodes (4c) of the endotracheal tube (1a, 1b).

16. Method of classifying tissue types, comprising the steps of: inducing (S11) at least one alternating electrical signal with at least two different predefined frequencies into tissue by means of at least two inducing electrodes (31); measuring (S12) a current waveform and a voltage waveform of the induced alternating electrical signal in the tissue by means of the at least two inducing electrodes (31) or by means of at least two measuring electrodes (32); calculating (S13) at least two impedances of the tissue by means of the measured current waveform and the measured voltage waveform; and classifying (S14) a tissue type of the tissue based on the calculated at least two impedances, wherein the at least two inducing electrodes (31) are formed by stimulation electrodes (4a), inducing electrodes (4b), or combination electrodes (4c) on a tube outer side of a tube (2) of an endotracheal tube (1a, 1b).

17. (canceled).

18. Endotracheal tube for classifying tissue types configured to be able to perform the method according to claim 16, wherein the at least two inducing electrodes (13) and optionally the at least two measuring electrodes (14) are arranged on a tube outer side of a tube of the endotracheal tube.

19. Endotracheal tube (1a, 1b) according to claim 1, wherein at least two of the electrodes (4) are the at least two inducing electrodes (31), and optionally wherein at least two further ones of the electrodes (4) are the at least two measuring electrodes (32).

20. System (20) according to claim 10, wherein at least two of the electrodes (4) are either the at least two inducing electrodes (31) or are the at least two measuring electrodes (32), and wherein at least two separate deduction electrodes (14) or counter electrodes (15) are, respectively, either the at least two measuring electrodes (32) or the at least two inducing electrodes (31).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0175] The present invention is explained in more detail below with reference to the examplary embodiments shown in the schematic figures, wherein:

[0176] FIGS. 1a to 1d represent four embodiments of the endotracheal tube according to the first aspect of the present invention;

[0177] FIGS. 2a to 2b represent arrangements of electrodes in an electrode array or sub-array;

[0178] FIGS. 3a to 3c represent arrangements of circularly extending stimulation electrodes, conduction electrodes and combination electrodes in sub-arrays;

[0179] FIGS. 4a to 4c represent arrangements of axially extending stimulation electrodes, conduction electrodes and combination electrodes in sub-arrays;

[0180] FIG. 5 represents an embodiment of the endotracheal tube according to the second aspect of the present invention;

[0181] FIGS. 6a to 6b represent sectional views of the exemplary embodiment of the endotracheal tube according to the second aspect of the present invention;

[0182] FIGS. 7a to 7c represent various paddings with electrodes arranged thereon;

[0183] FIG. 8 represents an adhesive electrode;

[0184] FIG. 9 represents an exemplary embodiment of an endotracheal tube according to the first or the second aspect of the present invention with X-ray contrast strips;

[0185] FIG. 10 represents an embodiment of an endotracheal tube according to the first or the second aspect of the present invention including depth marking;

[0186] FIG. 11 represents an embodiment of an endotracheal tube according to the first or the second aspect of the present invention including integrated optics;

[0187] FIGS. 12a to 12c represent three embodiments of an endotracheal tube according to the first or the second aspect of the present invention with pressure sensors;

[0188] FIG. 13 represents an exemplary embodiment of a system according to the third aspect of the present invention;

[0189] FIG. 14 represents the method for deriving stimulus responses during intra-operative neuromonitoring according to the fourth aspect of the present invention;

[0190] FIG. 15 represents a schematic representation of an overall system;

[0191] FIG. 16 represents the method for classifying tissue types according to the fifth aspect of the present invention;

[0192] FIG. 17 represents an embodiment of the endotracheal tube according to the first or second aspect of the present invention, which is configured to perform the method for classifying.

[0193] The accompanying figures of the drawing are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in connection with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the advantages mentioned will be apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale with respect to each other.

[0194] In the figures of the drawing, identical elements, features and components which have the same function and the same effect are each given the same reference signs, unless otherwise stated.

Description Of Exemplary Embodiments

[0195] In FIGS. 1a to 1d, four embodiments of an endotracheal tube 1a according to the first aspect of the present invention are schematically illustrated.

[0196] The endotracheal tube la can be used in intra-operative neuromonitoring to monitor nerve and muscle activity and comprises a tube 2, a fixation element 3 and an electrode array 5.

[0197] The tube 2 has a proximal end 7 and a distal end (tube tip) 8. Over its entire length, the tube has a substantially circular cross-section with a constant inner diameter or outer diameter. The thickness of the wall of the tube 2 is very small compared to its inner diameter, which means that the inner diameter of the tube 2 is essentially equal to its outer diameter.

[0198] The tube 2 is made of reinforced PVC and has an opening at the proximal end 7 in the axial direction with a connector that can be connected to a ventilator (see FIG. 13) by means of a suitable tube. At the distal end 8, the tube 2 also has an opening in the axial direction and also an additional opening laterally.

[0199] At a predefined element distance from the tube tip 8, a fixation element 3 in the form of an inflatable balloon is located on a tube outer side of the tube 2. The balloon is made of silicone and can be inflated by means of a tube running along an inner side of the tube 2 with a Luer connection at its proximal end by means of a disposable syringe.

[0200] Further proximal than the balloon 3, an electrode array 5 is arranged on the tube exterior at a predefined array distance from the tube tip 8. The electrode array 5 comprises at least two electrodes (see FIGS. 2a and 2b), which can be formed as stimulation electrodes and/or conduction electrodes and/or combination electrodes. The electrodes can be connected to an IOM system by means of a suitable connector (see FIG. 13). The electrode array 5 extends in the axial direction over a predefined array length and completely surrounds the tube 2 in a circular manner. On the outside of the tube, the at least two electrodes are distributed over 360° around the tube 2 in the electrode array 5. The electrodes can extend in an axial direction or circularly (annularly) along the tube 2 within the electrode array (see FIGS. 2a and 2b).

[0201] The electrode array 5 can be divided into several sub-arrays 5a, 5b, 5c, 5n. The exemplary embodiment shown in FIG. 1a has an electrode array (5) without subdivision or with only one sub-array 5a. The exemplary embodiment shown in FIG. 1b has an electrode array 5 divided into two sub-arrays 5a, 5b. The preferred exemplary embodiment shown in FIG. 1c has an electrode array 5 divided into three sub-arrays 5a, 5b, 5c. The exemplary embodiment shown in FIG. 1d has an electrode array 5 divided into four or more sub-arrays 5a, 5b, 5c, . . . , 5n. Each sub-array 5a, 5b, 5c, 5n fully comprises at least two of the electrodes of the electrode array 5. In other words, at least two electrodes of the electrode array 5 each form a sub-array 5a, 5b, 5c, 5n. The sub-arrays 5a, 5b, 5c, 5n are each arranged at a predefined sub-array spacing from each other in the axial direction.

[0202] The endotracheal tube 1a is inserted into the trachea of a patient during a surgical procedure such as a thyroid operation and is advanced sufficiently to allow the patient to be ventilated under anaesthesia by a ventilator during the surgical procedure. The balloon 3 is inflated once the endotracheal tube 1a is correctly advanced and positioned to ventilate the patient. This fixes the endotracheal tube 1a or the tube 2 in the trachea so that the endotracheal tube 1a can be prevented from moving or twisting during the surgical procedure. The electrode array 5 or the electrodes 4 are arranged at a predefined array distance on the outside of the tube in such a way that the electrodes 4 are in contact with the vocal folds when the endotracheal tube 1a is correctly advanced and positioned to ventilate the patient and is fixed in place by means of the inflated balloon 3. Muscle tissue can be stimulated on the vocal folds by means of the electrodes 4 during the surgical procedure and, additionally or alternatively, stimulus responses can be derived from the stimulated muscle tissue and thus monitored by means of intra-operative neuromonitoring of the NLR, particularly during thyroid surgery.

[0203] In FIGS. 2a and 2b, a sub-array 5a/5b/5c/5n or an electrode array, if this only comprises a sub-array 5a, is shown schematically on the tube 2.

[0204] The sub-array 5a/5b/5c/5n completely comprises at least two, in this case exemplarily five, electrodes 4. The electrodes 4 are exemplarily formed here as substantially rectangular strips of conductive material. The electrodes 4 can extend in the sub-array 5a/5b/5c/5n in the axial direction, as shown in FIG. 2b, or circularly, as shown in FIG. 2a, along the tube 2. In this case, the electrodes 4 are each spaced apart from each other at an equal predefined electrode distance. The electrodes 4 can be stimulation electrodes, conduction electrodes or combination electrodes (see FIGS. 3a to 4c).

[0205] In the sub-array 5a/5b/5c/5n shown in FIG. 2a, the electrodes 4 running circularly over 360° around the tube 2 are spaced from each other in the axial direction by the electrode spacing. In the sub-array 5a/5b/5c/5n shown in FIG. 2b, the electrodes (4) running in the axial direction along the tube 2 are distributed circularly over 360° around the tube 2, and are spaced apart from each other in each case by the electrode spacing.

[0206] In FIGS. 3a to 3c, a tube 2 with two sub-arrays 5a, 5b, each comprising stimulation electrodes 4a and/or conduction electrodes 4b or combination electrodes 4c, is shown schematically.

[0207] The two sub-arrays 5a, 5b are spaced apart from one another in the axial direction at the predefined sub-array spacing and comprise here, by way of example, four electrodes 4a, 4b, 4c in each case, which extend circularly over 360° around the tube 2 and are arranged spaced apart from one another in the axial direction at the predefined electrode spacing. The sub-array spacing is greater than the electrode spacing.

[0208] Each stimulation electrode 4a or combination electrode 4c can form a stimulation pole alone or in combination with one or more further stimulation electrodes 4a or combination electrodes 4c. Thus, depending on the number ks of stimulation or combination electrodes 4a/4c, 1 to k.sub.s stimulation poles can be formed. By means of stimulation poles, tissue (e.g. the muscle tissue on the vocal folds) or the nerves connected to it can be stimulated by means of alternating electrical signals.

[0209] Each conduction electrode 4b or combination electrode 4c can form a stimulation pole alone or in combination with one or more other conduction electrodes 4b or combination electrodes 4c. Thus, depending on the number k.sub.A of the conduction electrodes or combination electrodes 4b/4c, 1 to k.sub.A conduction poles can be formed. Stimulus responses from stimulated tissue can be derived as EMGs by means of conduction poles.

[0210] In the sub-arrays 5a, 5b shown in FIG. 3a, the first sub-array 5a comprises exclusively four stimulation electrodes 4a, and the second sub-array comprises exclusively four conduction electrodes 4b. Thus, the stimulation pole(s) are clearly spatially separated from the conduction poles, resulting in an improved signal-to-noise ratio (SNR).

[0211] In the sub-arrays 5a, 5b shown in FIG. 3b, the first sub-array 5a and the second sub-array 5b each comprise two stimulation electrodes 4a and two conduction electrodes 4b. The stimulation electrodes 4a and the conduction electrodes 4b are arranged alternately in the two sub-arrays 5a, 5b, in this case as an example. In particular, if each stimulation electrode forms a separate stimulation pole and each conduction electrode forms a separate conduction pole, the tissue to which the electrodes are applied can be monitored with high spatial resolution.

[0212] In the sub-arrays 5a, 5b shown in FIG. 3b, the first sub-array 5a and the second sub-array 5b each comprise four combination electrodes 4c. The combination electrodes can each form a stimulation pole for stimulating tissue, and can then form a discharge pole for discharging stimulus responses from the stimulated tissue. Depending on how the combination electrodes are connected, EMGs with high SNR or high spatial resolution can be derived.

[0213] FIGS. 4a to 4c each schematically show a tube 2 with, by way of example, two sub-arrays 5a, 5b, each comprising stimulation electrodes 4a and/or conduction electrodes 4b or combination electrodes 4c. The sub-arrays 5a, 5b shown in FIGS. 4a to 4c differ from those shown in FIGS. 3a to 3c essentially only in the course of the electrodes 4a, 4b, 4c within the sub-arrays 5a, 5b. Therefore, only the differences with respect to FIGS. 3a to 3c are explained below and otherwise reference is made with respect to the explanations given with respect to FIGS. 3a to 3c.

[0214] The two sub-arrays 5a, 5b are spaced apart from each other in the axial direction at the predefined sub-array spacing and comprise here, by way of example, in each case several electrodes 4a, 4b, 4c (three each visibly shown) which extend in the axial direction and are arranged distributed over 360° and spaced apart from each other around the tube 2 at the predefined electrode spacing. The sub-array spacing is greater than the electrode spacing.

[0215] In the case of the sub-arrays 5a, 5b shown in FIG. 4a, the first sub-array 5a comprises exclusively stimulation electrodes 4a and the second sub-array comprises exclusively conduction electrodes 4b. Thus, the stimulation pole(s) are clearly spatially separated from the conduction poles, resulting in an improved signal-to-noise ratio (SNR).

[0216] In the sub-arrays 5a, 5b shown in FIG. 4b, the first sub-array 5a and the second sub-array 5b each comprise a plurality of stimulation electrodes 4a and a plurality of conduction electrodes 4b. The stimulation electrodes 4a and the conduction electrodes 4b are arranged alternately in the two sub-arrays 5a, 5b as an example. Here, in the second sub-array 5b, stimulation electrodes 4a are also opposite the stimulation electrodes 4a in the first sub-array 5a. The same applies to the conduction electrodes 4b. The electrodes of the second sub-array 2b can also be circularly displaced with respect to those of the first sub-array 5a. Stimulation electrodes 4a in the first sub-array 5a can also be opposed by conduction electrodes 4b in the second sub-array 5b, and likewise conduction electrodes 4b in the first sub-array 5a can be opposed by stimulation electrodes 4a in the second sub-array 5b. In particular, if each stimulation electrode forms a separate stimulation pole and each conduction electrode forms a separate conduction pole, the tissue to which the electrodes are applied can be monitored with high spatial resolution.

[0217] In the sub-arrays 5a, 5b shown in FIG. 4b, the first sub-array 5a and the second sub-array 5b each comprise a plurality of combination electrodes 4c. The combination electrodes can each form a stimulation pole for stimulating tissue, and can then form a discharge pole for discharging stimulus responses from the stimulated tissue. Depending on how the combination electrodes are connected, EMGs with high SNR or high spatial resolution can be derived.

[0218] FIG. 5 schematically illustrates an embodiment of an endotracheal tube 1b according to the second aspect of the present invention. The endotracheal tube 1b shown in FIG. 5 differs from the endotracheal tube 1a of FIGS. 1a to 4c with its electrode array comprising at least two electrodes essentially in that at least one electrode 4 or electrode array such as that of FIGS. 1a to 4c is included, and in that a padding 6 is associated therewith. Therefore, only the differences to the endotracheal tube 1a of FIGS. 1a to 4c will be discussed below, wherein reference is otherwise made with respect to the explanations of FIGS. 1a to 4c.

[0219] The at least one electrode 4 or at least one electrode of the electrode array 5 is supported by the padding 6 on the tube outer side of the tube 2. For this purpose, the padding 6 is arranged on the tube outer side and the electrode(s) 4 is/are applied to the padding 6. The padding 6 has an elastic deformability (elasticity) at least in the radial direction towards the tube 2. When force is applied to the padded electrode(s) 4 in the radial direction towards the tube 2, the padding 6 deforms elastically towards the tube 6 so that the padded electrode(s) 4 is/are displaced towards the tube 2. As soon as the force on the electrode(s) 4 decreases or ceases, the padding 6 elastically deforms back so that the electrode(s) 4 are moved away from the tube 2 to their original position.

[0220] The padding 6 can be formed separately for each electrode 4 (see FIGS. 6a and 7a to 7c), or can be formed essentially annularly/circularly around the tube 2.

[0221] When the endotracheal tube 1b is inserted into the trachea, the padding 6 is compressed by the wall of the trachea. The at least one padded electrode 4 or the at least two padded electrodes of the electrode array 5 are pressed against the trachea or the vocal folds by the padding 6 (see FIG. 6b). The padded electrode(s) thus nestle(s) optimally against the tissue to be stimulated (e.g. muscle tissue). At the same time, the electrodes are prevented from moving by the padding 6. This means that the tissue can be stimulated particularly well and stimulus responses can be derived from it.

[0222] In FIGS. 6a and 6b the endotracheal tube 1b is shown schematically in section through the at least one electrode 4 or the electrode array 5 and through the padding 6.

[0223] In this case the padding 6 is divided into eight segments. Each segment of the padding 6 supports an electrode 4, for example of the electrode array, on the tube 2.

[0224] If the endotracheal tube 1a is inserted into a trachea 110, the padding 6 or its segments are elastically deformed towards the tube 2 at the points where electrodes 4 rest against the wall of the trachea 110 or the vocal folds 111. Due to the elasticity of the padding 6, it exerts a counterforce on the corresponding electrodes 4 so that they are pressed against the wall of the trachea 110 or the vocal folds 111.

[0225] FIGS. 7a to 7c schematically show three examples of paddings 6 or their segments.

[0226] The padding 6 shown in FIG. 7a has an elastic foam structure 6a which elastically supports the electrode 4 relative to the tube 2.

[0227] The padding 6 shown in FIG. 7b has an elastic spring element 6b which elastically supports the electrode 4 relative to the tube 2.

[0228] The padding 6 shown in FIG. 7c has an elastic balloon 6c filled with a gas or gas mixture, which elastically supports the electrode 4 relative to the tube 2.

[0229] In FIG. 8 an adhesive electrode 9 is shown schematically. The adhesive electrode 9 comprises an electrode section 9.1, a distance indicator 9.2 and an electrode connection 9.3.

[0230] The electrode section has at least one electrode 4, here exemplarily five electrodes 4. The electrode section 9.1 can also have a sub-array or an electrode array with one or more sub-arrays.

[0231] The distance indicator 9.2 is formed on the electrode section 9.1 and indicates the optimum distance or array distance to the tube tip/distal end or fixation element of the endotracheal tube of FIGS. 1a to d or 5.

[0232] The electrode connector is formed on a proximal end of the adhesive electrode 9 and is used to connect to an IOM system.

[0233] The adhesive electrode 9 is first optimally positioned on a tube 2 by means of the distance indicator 9.2 (e.g., at the predefined array distance), and is then attached around the tube 2 and fixed, for example, by means of an adhesive. The endotracheal tube with the adhesive electrode 9 can then be inserted into the trachea and connected to an IOM system by means of the electrode connection 9.3.

[0234] In FIG. 9, an exemplary embodiment of an endotracheal tube 1a, 1b according to the first or second aspect of the present invention is shown schematically. The endotracheal tube 1a, 1b comprises an X-ray contrast strip 10.

[0235] The X-ray contrast strip 10 is radiopaque, and extends in an axial direction from the tip 8 of the tube to the proximal end 7 of the endotracheal tube 1a, 1b. The X-ray contrast strip can be arranged on the outside of the tube, the inside of the tube 2 or in the wall of the tube 2.

[0236] By means of the X-ray contrast strip 10, the position of the endotracheal tube 1a, 1b in the trachea can be checked under X-ray control.

[0237] In FIG. 10, an exemplary embodiment of an endotracheal tube 1a, 1b according to the first or second aspect of the present invention is schematically shown. The endotracheal tube 1a, 1b has a depth marker 11 for intubation depth.

[0238] The depth marker 11 has a plurality of depth indications on the tube outer surface indicating the distance from the tube tip 8 in millimetres, and extends in axial direction.

[0239] By means of the depth marker 11, the intubation depth of the endotracheal tube 1a, 1b in the trachea and the position of the electrode(s) relative to the vocal folds can be checked.

[0240] FIG. 11 schematically illustrates an exemplary embodiment of an endotracheal tube 1a, 1b according to the first or second aspect of the present invention. The endotracheal tube 1a, 1b comprises an integrated optic 12.

[0241] The optics 12 comprises at least two light guide bundles. At least one of the light guide bundles guides light from a light source at the tip of the tube 8 into the surgical field. At least one other of the light guide bundles transmits an image (of the surgical field) from the tube tip 8 to a processing unit for displaying the image on a monitor. For this purpose, the light guide bundles preferably run on an inner side of the tube 2, or alternatively run on the tube outer side. The light guide bundles can be connected at the proximal end 7 of the endotracheal tube 1a, 1b by means of an adapter to an overall system such as an IOM system, whereby this also comprises the light source in addition to the monitor.

[0242] Thus, by means of the optics 12, it is possible to visually check the position of the endotracheal tube 1a, 1b in a trachea, and to visually check the vocal cords as well as their movement, in particular during insertion and/or removal of the endotracheal tube 1a, 1b into/from the patient's trachea.

[0243] In FIGS. 12a to 12c, three embodiments of an endotracheal tube 1a, 1b according to the first or second aspect of the present invention are schematically shown. The endotracheal tube 1a, 1b comprises at least one pressure sensor 13.

[0244] The at least one pressure sensor 13 can be formed as a ring as is shown in FIG. 12a, or as two rings as is shown in FIG. 12c. The at least one ring-shaped pressure sensor 13 is arranged circularly over 360° on the tube exterior around the endotracheal tube 1a, 1b. Alternatively, several individual pressure sensors can be arranged circularly over 360° or tangentially distributed on the tube outer side around the endotracheal tube 1a, 1b as shown in FIG. 12b. The pressure sensor(s) 13 are (is) arranged between the fixation element 3 and the at least one electrode 4 (of the electrode array 5).

[0245] The pressure sensor or the pressure sensors 13 can consist of a thin membrane, and can in particular be strain gauges which record the mechanical strain and/or compression caused by pressure (muscle contractions in a trachea), and convert the mechanical strain and/or compression into electrical signals.

[0246] The pressure sensor(s) 13 allow, in addition to EMG conduction by means of the electrodes 4 (of the electrode array 5), a second physiological derivation that can be used to monitor the nerve or muscle tissue during intra-operative neuromonitoring. Furthermore, the pressure measurement is not susceptible to artefacts, and thus enables an almost artefact-free derivation.

[0247] FIG. 13 schematically illustrates an exemplary embodiment of the system 20 according to the third aspect of the present invention. The system 20 comprises the endotracheal tube 1a, 1b of FIGS. 1a to 12c, and at least one separate conduction electrode 14, and at least one counter electrode 15. At least one electrode 4 (of the electrode array 5) is formed as a stimulation electrode 4a or as a combination electrode 4c.

[0248] The at least one separate conduction electrode 14 is formed as a surface electrode, and can be attached to the patient in the vicinity of the stimulated tissue (e.g. on the outside of the patient's neck). The separate conduction electrode 14 can be used to derive stimulus responses from the stimulated tissue instead of or in addition to the conduction electrode(s) 4b or combination electrode(s) 4c of the endotracheal tube 1a, 1b on the tube outer side of the stimulated nerve tissue. The conduction of the stimulus responses thus is carried out optionally by means of at least one of the conduction electrodes 4b/combination electrodes 4c of the endotracheal tube 1a, 1b, and additionally or alternatively by means of the at least one separate conduction electrode 14.

[0249] The optional at least one counter electrode 15 is formed as a needle electrode, and can be attached externally to the patient. With the optional at least one counter electrode 15 and with the at least one stimulation electrode 4a or the at least one combination electrode 4c, the tissue can be stimulated in a monopolar fashion. For this purpose, the at least one counter electrode 15 is attached to the patient at a different location than the stimulation electrode(s) 4a or combination electrode(s) 4c of the endotracheal tube 1a, 1b, and serves as a counter pole to the stimulation pole(s) formed by the stimulation electrode(s) 4a/ combination electrode(s) 4c. In particular, by means of a stimulation electrode or combination electrode 4a/4c of the endotracheal tube 1a, 1b on its tube outer side (a stimulation pole) and a 15 counter electrode (counter pole), the (nerve) tissue can be stimulated in a monopolar fashion.

[0250] Alternatively, the counter electrode 15 can be formed by a stimulation electrode 4a or combination electrode 4c located on the outside of the tube, or alternatively can be formed by an interconnection of several of the electrodes on the outside of the tube. The monopolar stimulation of (nerve) tissue is performed accordingly by means of the counter electrode 15 on the outside of the tube and a further stimulation electrode 4a or combination electrode 4c.

[0251] In FIG. 14, the method for deriving stimulus responses during intra-operative neuromonitoring according to the fourth aspect of the present invention is schematically illustrated. The method for deriving stimulus responses during intra-operative neuromonitoring comprises the steps of electrical stimulation S1 and derivation S2, and is performed using the endotracheal tube 1a, 1b of FIGS. 1a to 12c or the system 20 shown in FIG. 13.

[0252] In step S1, tissue (e.g. muscle tissue) is electrically stimulated. The step of electrically stimulating is performed by means of at least one stimulation electrode 4a or at least one combination electrode 4c of the endotracheal tube 1a, 1b, and optionally additionally by means of at least one counter electrode 15 of the system 20. The step of electrically stimulating can be performed in a monopolar fashion by means of the at least one stimulation electrode 4a/combination electrode 4c and the at least one counter electrode 15. Further, the step of electrically stimulating can be bipolar by means of at least two stimulation electrodes 4a/combination electrodes 4c. Furthermore, the step of electrically stimulating can be multipolar by means of multiple stimulation electrodes 4a/combination electrodes 4c.

[0253] In step S2, a stimulus response of the stimulated tissue (e.g. at the vocal folds) is derived. The deriving is carried out by means of at least one conduction electrode 4b, or at least one combination electrode 4c of the endotracheal tube 1a, 1b, or by means of at least one separate conduction electrode 14 of the system 20.

[0254] In FIG. 15, an overall system 200 is shown schematically. The complete system 200 comprises the endotracheal tube 1a, 1b of FIGS. 1a to 12c, or the system 20 shown in FIG. 13 as well as an IOM system 210 and a ventilator 220.

[0255] The tube of the endotracheal tube 1a, 1b is fluidly connected to the ventilator 220 by means of a suitable tube connected to the proximal end of the tube. The electrodes of the endotracheal tube 1a, 1b and, if present, the separate conduction electrode and optional counter electrode of the system 20 are electrically connected to the IOM system 210 by means of one or more suitable connecting cables.

[0256] The endotracheal tube 1a, 1b is inserted into the trachea of a patient 100 during a surgical procedure, and fixed there by means of its balloon. During the surgical procedure, the patient is ventilated with air by the ventilator 220 by means of the tube of the endotracheal tube 1a, 1b, and is thus supplied with oxygen. For intra-operative monitoring of the muscle and nerve tissue in the area to be operated, the muscle tissue at the vocal folds is stimulated by means of the stimulation electrode(s)/combination electrode(s) of the endotracheal tube 1a, 1b and optionally the counter electrode(s) of the system 20 in a monopolar, bipolar or multipolar fashion by delivering an appropriate alternating electrical signal from a signal generator of the IOM system 210 to the electrodes, and by inducing the signal by means of the electrodes into the muscle tissue. The stimulus responses from the stimulated muscle tissue are recorded by means of the conduction electrode(s)/combination electrode(s) of the endotracheal tube 1a, 1b, and/or the separate conduction electrode(s) of the system 20 and are transmitted to the IOM system for displaying as EMGs on a monitor of the IOM system, or for further processing of the stimulus responses.

[0257] FIG. 16 schematically illustrates the method for classifying tissue types according to the fifth aspect of the present invention. The method for classifying tissue types comprises the steps of inducing S11, measuring S12, calculating S13 and classifying S14. The method can be performed in particular by means of the endotracheal tube 1a, 1b of FIGS. 1a to 12c, or can be performed by the system shown in FIG. 13.

[0258] In step S11, at least one alternating electrical signal with at least two different frequencies is induced into tissue by means of at least two inducing electrodes. For this purpose, the at least two inducing electrodes are applied to the tissue. The alternating electrical signal is preferably a sinusoidal signal, square-wave signal, triangular signal or the like in which the at least two frequencies are superimposed, or follow one another in time at defined intervals.

[0259] The induced alternating electrical signal causes a current to flow between the inducing electrodes through the tissue to be categorised.

[0260] In step S12, a current curve and a voltage curve of the induced alternating electrical signal are measured in the tissue by means of the at least two inducing electrodes or by means of at least two measuring electrodes. The voltage and the current in the tissue resulting from the application of the current of the alternating electrical signal are measured. Preferably, the at least two measuring electrodes are used for this purpose.

[0261] In step S13, at least two impedances of the tissue are calculated on the basis of the measured current curve and the measured voltage curve. The at least two impedances are calculated on the basis of the measured current curve and voltage curve at each of the at least two frequencies of the induced alternating electrical signal.

[0262] In step S14, a tissue type of the tissue is categorised based on the calculated at least two impedances. For example, a look-up table of impedances at different frequencies and corresponding tissue types can be used to categorise the tissue type based on the calculated impedances of the tissue. In particular, target tissue can be categorised as at least either muscle tissue or other tissue based on the calculated impedances.

[0263] FIG. 17 schematically shows an exemplary embodiment of the endotracheal tube 1a, 1b of FIGS. 1 to 12c configured to perform the method for categorizing tissue types shown in FIG. 16. The endotracheal tube 1a, 1b comprises two inducing electrodes 31 and two optional measuring electrodes 32.

[0264] The two inducing electrodes 31 are formed by at least two of the stimulation electrodes and/or conduction electrodes and/or combination electrodes of the endotracheal tube 1a, 1b. The two optional measuring electrodes 32 are formed by at least two other of the stimulation electrodes and/or conduction electrodes and/or combination electrodes of the endotracheal tube 1a, 1b.

[0265] The alternating electrical signal can be generated by a signal generator or a stimulator to which the inducing electrodes 31 are electrically connectable. The signal generator can be integrated into an IOM system.

[0266] The actual measurement of the voltage and/or current can be performed by a measuring unit to which the two optional measuring electrodes 32 can be connected. The measuring unit can be integrated into the IOM system.

[0267] A calculation unit, which can be integrated into the IOM system, can calculate the at least two impedances for each of the at least two frequencies of the induced alternating electrical signal from the measured voltage waveform and the measured current waveform.

[0268] Subsequently, a categorisation unit, which can be integrated into the IOM system, can perform the categorisation of the tissue type based on the at least two calculated impedances of the tissue.

[0269] Although the present invention has been fully described above with reference to preferred embodiments, the present invention not limited thereto, but can be modified in a variety of ways.

[0270] List of Reference Signs

[0271] 1a, 1b Endotracheal tube

[0272] 2 Tube

[0273] 3 Fixation element

[0274] 4 Electrode

[0275] 4a Stimulation electrode

[0276] 4b Conduction electrode

[0277] 4c Combination electrode

[0278] 5 Electrode array

[0279] 5a, 5b, 5c, . . . , 5n Sub-arrays

[0280] 6 Lining

[0281] 6a Foam structure

[0282] 6b Spring element

[0283] 6c Elastic balloon

[0284] 7 Proximal end

[0285] 8 Distal end

[0286] 9 Adhesive electrode

[0287] 9.1 Electrode section

[0288] 9.2 Distance indicator

[0289] 9.3 Electrode connection

[0290] 10 X-ray contrast strip

[0291] 11 Depth marker

[0292] 12 Optics

[0293] 13 Pressure sensors

[0294] 14 Separate conduction electrode

[0295] 15 Counter electrode

[0296] 20 System

[0297] 21 Counter electrode

[0298] 22 Separate conduction electrode

[0299] 31 Inducing electrode

[0300] 32 Measuring electrode

[0301] 100 Patient

[0302] 110 Trachea

[0303] 111 Vocal fold

[0304] 200 Total system

[0305] 210 IOM system

[0306] 220 Ventilator

[0307] S1 Electrical stimulation

[0308] S2 Deriving

[0309] S11 Inducing

[0310] S12 Measuring

[0311] S13 Calculating

[0312] S14 Classifying