MEDICAL SYSTEM FOR CONTROLLING THE POSITION AND ORIENTATION OF A CATHETERS TIP IN THE BODY OF A PATIENT

Description

[0001] The invention relates to a medical system for controlling the position and orientation of a catheter tip, in particular a central venous catheter, in the body of a patient.

[0002] Catheters, especially central venous catheters, are well-known in medicine. When inserting a catheter, its tip is inserted into an access point on the body and advanced to the desired location.

[0003] Central venous catheters are typically inserted into the venous system via a vein in the upper half of the body. The catheter tip is usually advanced to the area of ​​the right atrium. Insufficiently precise positioning of the catheter tip can lead to problems. To counteract this, monitoring the position of the catheter tip is necessary. Various methods are known for this purpose in clinical practice.

[0004] In a known procedure, the position of the catheter tip is X-rayed after or even during insertion. The associated radiation exposure for the patient limits the widespread use of this method. Furthermore, the procedure is comparatively time-consuming and expensive.

[0005] In another known method, position control is performed electrocardiographically (e.g., W. Schummer et al.: "Optimized positioning of central venous catheters through a modified application of intravascular electrocardiography," Anästhesist 54 (2005), pages 983-990). In this method, an ECG signal is recorded between a skin electrode attached to the patient's body surface and a Seldinger wire of the catheter. This known method utilizes the fact that the P wave of the ECG signal changes depending on the advancement of the catheter tip. The P wave represents the electrical excitation of the atrium. Upon entry of the catheter tip into the atrium, a characteristic change in the P wave occurs. Position control is thus achieved by observing the recorded ECG signal. This known electrocardiographic method requires, firstly, the application of the skin electrode to the patient's body surface.In addition, an ECG device and monitor for observing the ECG signal must be provided.

[0006] US 2018 / 132877 A1 discloses navigation and tissue detection systems and methods for navigating to and / or detecting selected tissue using the innate electrical activity of the selected tissue and / or other tissues.

[0007] US 2008 / 097232 A1 discloses a method for locating the tip of a central venous catheter (CVC) with a distal and a proximal electrode pair positioned in the superior vena cava, right atrium, and / or right ventricle. The method involves acquiring a distal and a proximal electrical signal from the distal and proximal electrode pairs and using these signals to generate a distal and a proximal P wave, respectively. A deflection value is determined for each P wave. A ratio of the deflection values ​​is then used to determine the position of the CVC tip.

[0008] US 2019 / 038897 A1 discloses a method for positioning an intravascular catheter, wherein the catheter comprises a plurality of electrodes and several electrodes of the plurality of electrodes are configured to emit electrical signals.

[0009] The object of the invention is to provide a medical system of the type mentioned above which offers advantages over the prior art.

[0010] To solve this problem, the invention provides a medical system with the features of claim 1. Advantageous embodiments are specified in the dependent claims. The wording of all claims is made clear by reference to the content of the description.

[0011] A method executable using the medical system according to the invention for controlling the position and orientation of a catheter tip, in particular a central venous catheter, in a patient's body comprises the following steps: a) detecting a first electrical potential by means of a first electrode arranged at the catheter tip and generating a first signal, which represents a time course of the detected first electrical potential; b) detecting a second electrical potential by means of a second electrode arranged at the catheter tip and spaced proximally from the first electrode, and generating a second signal, which represents a time course of the detected second electrical potential; c) generating a difference signal as a function of the first signal and the second signal.wherein the differential signal represents a time course of an electrical voltage between the first electrode and the second electrode; d) Controlling the position and orientation of the catheter tip by comparing the differential signal and a reference signal, which represents a desired position and orientation of the catheter tip. The invention is based on the consideration that catheters, in particular central venous catheters,The catheter is often not placed in the operating room. In other words, the patient is often not connected to an ECG device via skin electrodes when the catheter is inserted. Applying skin electrodes is time-consuming. Providing an ECG device solely for position verification represents an additional expense. The solution according to the invention eliminates the need to attach skin electrodes to the patient's body surface. This saves time, which is particularly advantageous in medical emergencies. Furthermore, the additional expense of providing the ECG device is eliminated, resulting in cost savings. Unlike the known electrocardiographic method, the invention specifically does not involve recording signals from the patient's skin surface. Instead, signals are recorded, preferably exclusively, from the catheter itself.namely the first signal and the second signal. For this purpose, the first and second electrodes are positioned at the catheter tip. The first and second signals represent the electrical potential at the respective electrode, with the electrical potentials resulting from the electrical activity of the heart muscle cells. The inventors recognized, in particular, that as long as the first and second electrodes are located in a vein, for example, the superior vena cava, in front of the right atrium, both electrodes have a similar electrical potential profile. This means that the electrical voltage between the first and second electrodes is small. As soon as the first electrode, positioned distally at the catheter tip, migrates into the atrium,The potential difference between the first and second electrodes changes. Consequently, the generated differential signal also changes. In simplified terms, a characteristic time course and / or amplitude change of the differential signal is used as a measurement signal to monitor the position. Furthermore, the differential signal, i.e., the voltage between the first and second electrodes, can be used to monitor the orientation of the catheter tip. As soon as the catheter tip, along with the first and second electrodes, moves away from the heart, the polarity of the differential signal changes. This polarity indicates whether the catheter tip is moving towards or away from the heart. Thus, even during catheter insertion, it can be determined whether the catheter tip—to put it simply—is turning towards the head instead of the heart.

[0012] The solution is particularly advantageous for central venous catheters, peripherally inserted central venous catheters (PICCs), and so-called midlines. However, the solution according to the invention is not limited to such catheters, but is also advantageously suitable, for example, for pulmonary artery catheters, dialysis catheters, and / or arterial catheters.

[0013] In one embodiment, the method includes the step of outputting the differential signal and / or a control signal, which represents a deviation between the differential signal and the reference signal. In other words, the control signal represents a deviation between the actual position and / or orientation and the desired position and / or orientation. The differential signal and / or the control signal is preferably output in a way that is visually and / or audibly perceptible to medical personnel. This is particularly user-friendly and allows for simple and reliable monitoring of the position and / or orientation.

[0014] According to the invention, monitoring the orientation of the catheter tip comprises the step of detecting and evaluating a change in the sign of the differential signal, wherein the change in sign represents a change in the polarity of the first and second electrodes. The inventors have recognized that the polarity of the first and / or the second electrode allows conclusions to be drawn about the orientation of the catheter tip relative to the heart. In other words, the polarity of the electrical voltage between the first and second electrodes indicates whether the catheter tip is oriented towards or away from the heart. Detecting and evaluating the associated change in sign of the differential signal is possible using simple means. With this embodiment of the invention, the orientation of the catheter tip can be monitored with comparatively little equipment.

[0015] In a further embodiment, the first signal is derived from the catheter tip by means of a first conductor wire and / or the second signal is derived from the catheter tip by means of a second conductor wire. Such wired signal derivation is possible with technically simple means. The first conductor wire and / or the second conductor wire extend from the respective electrode towards a proximal end of the catheter. Preferably, the first conductor wire and / or the second conductor wire extend longitudinally inside the catheter. At their distal ends, facing away from the catheter tip, the first conductor wire and / or the second conductor wire are connected to an evaluation unit designed for signal processing. In this embodiment of the invention, the first electrode and / or the second electrode can be formed by a distal end of the respective conductor wire.

[0016] In a further embodiment, the first signal is derived from the catheter tip via a fluid-filled first catheter lumen, and / or the second signal is derived from the catheter tip via a fluid-filled second catheter lumen. This embodiment of the invention eliminates the need for a wired transmission of the first and / or second signal. In the actual application of the catheter, the first and / or second catheter lumen is used to administer medication and / or to draw blood from the patient's venous system. This gives the first and / or second catheter lumen a particularly advantageous multiple function in this embodiment of the invention. This simplifies the catheter's design and ultimately allows for simple and cost-effective manufacturing.In this embodiment of the invention, the first electrode and / or the second electrode can be formed by a distal end opening of the respective catheter lumen. This allows for a further simplified catheter design.

[0017] In a further embodiment, the method comprises the following steps: detecting a third electrical potential by means of a third electrode arranged at the catheter tip and spaced proximally from the second electrode, and generating a third signal representing a time course of the detected third electrical potential; generating a further differential signal as a function of the second and third signals, wherein the further differential signal represents a time course of an electrical voltage between the second and third electrodes; wherein checking the position and / or orientation of the catheter tip includes comparing the differential signal and the further differential signal. In simplified terms, this embodiment of the invention detects the electrical potential at an additional location in the region of the catheter tip.For this purpose, a third electrode is provided and positioned proximally to the second electrode. The inventors recognized that this allows for greater safety. The additional differential signal and the differential signal are compared to control the position and / or orientation. This comparison can be performed using appropriate algorithms, for example, by subtracting the additional differential signal from the differential signal or vice versa. The third signal can be derived from the catheter tip in a manner analogous to the first and / or second signals. For example, a third conductor wire or a fluid-filled third catheter lumen can be provided for this purpose. Accordingly, the third electrode can be formed by a distal end of the third conductor wire or by a distal opening of the third catheter lumen.It is understood that in further embodiments of the invention, more than just the first, second, and third electrical potentials can be detected at the catheter tip. Accordingly, more than the first, second, and third electrodes can be arranged at the catheter tip. For example, the arrangement of four, five, six, more than six, or more than ten electrodes is conceivable.

[0018] The medical system according to the invention comprises: a catheter, in particular a central venous catheter, with a catheter tip on which at least a first electrode and a second electrode are arranged, wherein the second electrode is spaced proximal to the first electrode, wherein the first electrode is configured to detect a first electrical potential and to generate a first signal representing a time course of the first electrical potential, and wherein the second electrode is configured to detect a second electrical potential and to generate a second signal representing a time course of the second electrical potential; an evaluation device connected to the first electrode and the second electrode, wherein the evaluation device is configured to generate a difference signal depending on the first signal and the second signal.wherein the difference signal represents a time course of an electrical voltage between the first electrode and the second electrode. The medical system according to the invention enables simple, time-saving, and reliable control of the position and / or orientation of the catheter tip. For the sake of brevity, reference is made to the disclosure of the method executable using the medical system according to the invention. The points made there regarding the advantages associated with the solution according to the invention apply mutatis mutandis to the medical system according to the invention. The catheter is particularly suitable as a central venous catheter, PICC (Peripherally Inserted Central Venous Catheter), Midline, or pulmonary artery catheter.The catheter is designed as a dialysis catheter or arterial catheter. The first and second electrodes are arranged in the region of the catheter tip and are preferably each located on an outer surface of the catheter tip. The evaluation unit is configured to evaluate the first and second signals acquired and / or generated by the first and second electrodes. In particular, the evaluation unit is configured to generate the differential signal as a function of the first and second signals. The evaluation unit can be connected to the first and second electrodes via wired and / or wireless connections. For a wired connection, the catheter has at least one first conductor wire assigned to the first electrode and / or one second conductor wire assigned to the second electrode. Alternatively or additionally, a wireless connection via a first catheter lumen is possible.The catheter has one lumen assigned to the first electrode, and / or a second lumen assigned to the second electrode. In the actual application of the catheter, the first and / or second lumen is filled with (electrically conductive) fluid. This enables wireless signal transmission.

[0019] Furthermore, according to the invention, the evaluation unit is configured to compare the differential signal with a reference signal, which represents a desired position and orientation of the catheter tip. In other words, the evaluation unit is configured to analyze the curve of the differential signal. A significant change in the curve allows conclusions to be drawn about the position and orientation of the catheter tip.

[0020] In a further embodiment of the invention, an output device connected to the evaluation unit is provided, which is configured to output the differential signal and / or a control signal representing a deviation between the differential signal and the reference signal. The output device can be configured to output the signal optically and / or acoustically. The output device is preferably integrated into the evaluation unit, or vice versa. The output device can comprise a display, a screen, a projection device, or the like.

[0021] In a further embodiment of the invention, at least one further, third electrode is arranged at the catheter tip and spaced proximal to the second electrode, wherein the third electrode is configured to detect a third electrical potential and to generate a third signal, which represents a time course of the detected third electrical potential, wherein the evaluation device is connected to the third electrode and is configured to generate a further differential signal as a function of the second signal and the third signal, wherein the further differential signal represents a time course of an electrical voltage between the second electrode and the third electrode, and wherein the evaluation device is configured to compare the further differential signal and the differential signal.

[0022] Further advantages and features of the invention will become apparent from the claims and from the following description of preferred embodiments of the invention, which are illustrated with reference to the drawings. Fig. 1 shows, in a schematically simplified diagrammatic representation, individual steps of an embodiment of a method; Fig. 2 shows a highly simplified schematic representation of an embodiment of a medical system according to the invention, which is set up to carry out an embodiment of the method and comprises a catheter, an evaluation unit and an output unit; Fig. 3 shows a schematic detail representation of the catheter tip of the catheter according to Fig. 2 , wherein a first and second electrode are arranged at the catheter tip, Figs. 4 to 6 show different application situations when inserting the catheter according to Fig. 2 to clarify the procedure according to Fig. 1 Fig. 7 shows another application situation to illustrate the method, where two different positions and / or orientations of the catheter tip are superimposed. Fig. 8 shows schematic representations of different signal waveforms, which are based on Fig. 7 Figure 9 shows a further embodiment of a medical system according to the invention, wherein an additional, third electrode is arranged at the catheter tip, and Figures 10 to 12 show different application situations when applying the catheter of the medical system according to the invention. Fig. 9 in one of the Fig. 4 bis 6 corresponding presentation method.

[0023] According to Fig. 2 A medical system 1 is provided, comprising a catheter 2, an evaluation unit 3, and an output unit 4. The medical system 1 is based on Fig. 2 schematically simplified representation.

[0024] Catheter 2 is shown only in the region of its catheter tip 5. The catheter tip 5 is located at a distal end of catheter 2. In this case, catheter 2 is a central venous catheter.

[0025] In embodiments not shown in the drawing, the catheter may instead be a PICC catheter, a midline catheter, a pulmonary artery catheter, a dialysis catheter, or an arterial catheter.

[0026] The catheter 2 has a first electrode 6 and a second electrode 7 at its tip 5. The first electrode 6 is positioned closer to a distal end 8 of the catheter tip 5 than the second electrode 7. In other words, the second electrode 7 is located at a distance proximal to the first electrode 6 at the catheter tip 5. The distance between the second electrode 7 and the first electrode 6 is along a longitudinal axis 9 extending between the distal end 8 and a proximal end (not shown). The first and second electrodes 6 and 7 are each configured to detect an electrical potential. The electrical potential detectable or detected at the first electrode 6 can also be referred to as the first electrical potential P1. The electrical potential associated with the second electrode 7 can accordingly be referred to as the second electrical potential P2.

[0027] In the illustrated embodiment, the first and second electrodes 6, 7 are each configured to generate a signal representing a time course of the respective detected electrical potential. The first electrode 6 is configured to generate a first signal S1. The second electrode 7 is configured to generate a second signal S2. The first signal S1 represents the time course of the first electrical potential P1 detected by the first electrode 6. Accordingly, the second signal S2 represents the time course of the second electrical potential P2 detected by the second electrode 7.

[0028] Alternatively or additionally, the evaluation unit 3 can be set up to generate the first and second signals S1, S2 depending on the first and second electrical potentials P1, P2 detected by means of the first and second electrodes 6, 7.

[0029] The first and second electrodes 6, 7 are each connected to the evaluation unit 3. This connection serves to transmit the electrical potentials P1, P2 and / or the signals S1, S2 detected by the electrodes 6, 7, provided the latter are generated by the electrodes 6, 7. This transmission can also be referred to as a signal transmission, according to common medical terminology.

[0030] How based Fig. 3 As shown, the signal can be transmitted via wired or wireless connections. This illustrates... Fig. 3 Both variants, preferably either a wired or a wireless connection.

[0031] For wired data acquisition, a first conductor wire 10 and a second conductor wire 11 are provided. The first conductor wire 10 is assigned to the first electrode 6. The second conductor wire 11 is assigned to the second electrode 7. The conductor wires 10 and 11 establish an electrically conductive connection between the electrodes 6 and 7 on the one hand and the evaluation unit 3 on the other. Preferably, the conductor wires 10 and 11 extend longitudinally inside the catheter 2. The Fig. 3 The arrangement shown should be considered purely exemplary and a highly simplified schematic.

[0032] The electrodes 6, 7 can be manufactured as separate components and / or sections and subsequently electrically connected to the respective conductor wire 10, 11. Alternatively, the electrodes 6, 7 can be formed by a distal end of the respective conductor wire 10, 11.

[0033] For wireless data transmission, the catheter 2 can have a first catheter lumen 10' associated with the first electrode 6. A second catheter lumen 11' can correspondingly be associated with the second electrode 7. In the application of the catheter 2, the catheter lumens 10', 11' are provided for fluid conduction in a manner generally known to those skilled in the art. For example, a medical fluid can be administered or blood can be drawn via the catheter lumens 10', 11'. In this case, the catheter lumens 10', 11' also serve the aforementioned data transmission, which is effected via the electrically conductive fluid present in the catheter lumens 10', 11' during the application of the catheter 2. The catheter lumens 10', 11' are designed according to Fig. 3 The diagram is highly simplified and shown with dashed lines. The first electrode 6 can be formed by a distal end opening of the first catheter lumen 10'. The second electrode 7 can be formed by a distal end opening of the second catheter lumen 11'.

[0034] The evaluation unit 3 is designed for signal evaluation of the signals S1, S2 acquired or generated by the electrodes 6, 7. In the illustrated embodiment, the signal evaluation includes the generation of a differential signal D. The differential signal D is generated as a function of the first signal S1 and the second signal S2 and represents an electrical voltage prevailing between the first electrode 6 and the second electrode 7 (potential difference between the first electrical potential P1 and the second electrical potential P2).

[0035] In the illustrated embodiment, the evaluation unit 3 is connected to the output unit 4. The output unit 4 is configured here for the optical output of the differential signal D. For this purpose, the output unit 4 has a monitor 12. Based on Fig. 2 An exemplary time course of the difference signal D is schematically shown using monitor 12.

[0036] The insertion of the catheter 2 is carried out in a manner generally known to those skilled in the art. The catheter 2 is typically inserted into the patient's venous system via a vein in the upper half of the body. The catheter tip 5 is advanced to the region of the right atrium of the heart (H). Fig. 4 bis 6 The right atrium is hereinafter referred to as atrium A. It is known that insufficiently precise positioning of the catheter tip 5 in relation to atrium A is problematic. To avoid problems, therefore, verification of the position of the catheter tip 5 is necessary. The medical system 1 allows for such verification. For a more detailed explanation, particular reference is made below to the Fig. 4 bis 6 switched off.

[0037] The Fig. 4 bis 6 The following examples illustrate different situations during catheter insertion.

[0038] Fig. 4 This shows an initial situation in which the catheter tip 5 is advanced in a generally known manner via the superior vena cava V to just before atrium A. The following is shown. Fig. 4 The position of the catheter tip 5 shown can also be referred to as the first position. In this position, both the first electrode 6 and the second electrode 7 are located outside atrium A.

[0039] Fig. 5 This shows a second situation in which the catheter tip 5 has been advanced further from the first position towards atrium A. The following is shown. Fig. 5 The position of the catheter tip 5 shown can also be referred to as the second position. In this position, the first electrode 6 is located inside atrium A. In contrast, the second electrode 7 is located outside atrium A in the superior vena cava V.

[0040] Based on Fig. 6 A third situation is shown as an example. In this case, the catheter tip 5 is advanced further from the second position. Based on Fig. 6 The position of the catheter tip 5 shown can also be referred to as the third position. In the third position, the first electrode 6 and the second electrode 7 are located within atrium A.

[0041] During the insertion of the catheter and the associated advancement movement of the catheter tip 5, the electrical potentials P1, P2 and thus the electrical voltage represented by the differential signal D between the electrodes 6, 7 are preferably continuously detected.

[0042] The inventors recognized that the electrical voltage – and thus the differential signal D – changes depending on the position of the catheter tip 5 relative to the atrium A. In simplified terms, the position of the catheter tip 5 can be monitored based on the measured electrical voltage and thus the differential signal D.

[0043] As long as the first electrode 6 and the second electrode 7 are located in the vena cava V in front of the atrium A, a similar electrical potential is present at both electrodes 6, 7. In other words, the electrical voltage in the first position ( Fig. 4 ) comparatively small. This is due to the in Fig. 4 The exemplary time course of a difference signal D' resulting in the first situation is shown. The time course of the difference signal D' shows no significant deflection.

[0044] As soon as the first electrode 6 enters atrium A ( Fig. 5 ), a change occurs in the electrical potentials detected by electrodes 6, 7, and consequently in the voltage applied between electrodes 6, 7. Accordingly, the time course of the differential signal changes. This is in Fig. 5 This is illustrated by a difference signal D" . The difference signal D" differs from the difference signal D' in the first position ( Fig. 4 ) a changed signal pattern over time.

[0045] In third position ( Fig. 6 ) a further change in the voltage between the first electrode 6 and the second electrode 7 occurs. Accordingly, the time course of the difference signal changes, which can be seen from Fig. 4 This is exemplified by the difference signal D‴.

[0046] The characteristic change in the time course of the difference signal D, symbolized by the exemplary curves D', D" and D‴, allows conclusions to be drawn about the position of the catheter tip 5 in relation to the atrium A. This allows the position of the catheter tip 5 to be checked.

[0047] In the illustrated embodiment, the control includes comparing the differential signal D with a reference signal R. The reference signal R represents a desired position and / or orientation of the catheter tip 5.

[0048] The comparison of the difference signal D and the reference signal R can be performed visually by medical personnel using screen 12. Alternatively or additionally, the comparison can be performed using evaluation unit 3.

[0049] The underlying procedure is based on Fig. 1 This is a highly simplified schematic representation and includes steps a) to e). Here is a brief explanation: According to step a), the first signal S1 is generated based on the first electrical potential P1 detected by the first electrode 6.

[0050] According to step b), the second signal S2 is generated accordingly. This is based on the second electrical potential P2 detected by the second electrode 7.

[0051] According to step c), the difference signal D is generated. In this case, this is done using the evaluation unit 3.

[0052] According to step d), the position of the catheter tip 5 is checked. This is done in this case by comparing the (time course) of the difference signal D and the reference signal R. The comparison can be performed by visual inspection on the screen 12. Alternatively or additionally, the difference signal D and the reference signal R are compared with each other using the evaluation unit 3, preferably using suitable algorithms. In the simplest case, the comparison involves a simple subtraction.

[0053] If a visual comparison is provided, the difference signal D is output according to step e). Alternatively or additionally, a control signal representing the deviation between the difference signal D and the reference signal R can be output.

[0054] Medical system 1 allows, in addition to checking the position, alternatively or additionally also checking the orientation of the catheter tip 5. This is based on the Fig. 7 und 8 clarifies. Fig. 7 shows two superimposed situations during the insertion of catheter 2. The latter is shown in the diagram. Fig. 7 The illustrated embodiment is designed as a PICC catheter and is accordingly inserted into the venous system from the antecubital fossa. In both situations shown, the catheter tip 5 is located in a region B above the superior vena cava V.

[0055] In the first depicted situation, the catheter tip 5 is unintentionally advanced not towards atrium A, but instead towards the head. Reference symbols 6 and 7 of the first and second electrodes are assigned to this situation. In the second situation, the catheter tip 5 is instead advanced towards atrium A as required. Reference symbols 6' and 7' are assigned to this second situation in the enlarged area B.

[0056] The inventors recognized that the polarity of the difference signal changes depending on the orientation of the catheter tip 5 relative to the heart H. This is demonstrated by Fig. 8 This is illustrated. Two exemplary signal waveforms, D1 and D2, of the difference signal D are shown. Signal waveform D1 corresponds to the first situation, i.e., the orientation of the catheter tip 5 towards the head. The second signal waveform, D2, corresponds to the orientation of the catheter tip 5 towards the heart H (second situation). Depending on the orientation of the catheter tip 5, the polarity of the difference signal differs. In other words, the sign of the difference signal D changes. This is symbolized by the signal waveforms D1 and D2. Therefore, the orientation of the catheter tip 5 can be easily checked by means of appropriate signal analysis.

[0057] Fig. 9 shows a medical system 1a that is largely identical to the medical system 1 according to Fig. 2 The design is similar. The functionality is also largely identical. The following only highlights the key differences between medical system 1a and medical system 1. Fig. 2 received.

[0058] The key difference is the number of electrodes at the catheter tip 5a. In this case, in addition to the first and second electrodes 5, 7, a third electrode 13 is provided on the catheter 2a. The third electrode 13 is spaced proximally from the second electrode 7 along the longitudinal axis 9. The third electrode 13 is configured to detect a third electrical potential P3 and to generate a third signal S3. In simplified terms, the third electrode 13 is identical to the first and second electrodes 6, 7, except for its arrangement. The same principles apply to the derivation of signal S3 and the connection provided for this purpose between the third electrode 13 and the evaluation unit 3a as have already been stated regarding the derivation of signals S1, S2 ( Fig. 3 ).

[0059] In further contrast, the evaluation unit 3a is additionally configured to process the third signal S3. Depending on the third signal S3 and the second signal S2, a further differential signal d is generated. This further differential signal d represents a time course of an electrical voltage between the second electrode 7 and the third electrode 13.

[0060] In the embodiment according to Fig. 9 Checking the position and / or orientation of the catheter tip 5 involves comparing the differential signal D and the further differential signal d. In the simplest case, the further differential signal d is subtracted from the differential signal D. A comparison signal Dd resulting from this comparison can, for example, be output by the output device 4 and used as the basis for the check.

[0061] Based on the Fig. 10 bis 12 are in accordance with the Fig. 4 bis 6 Different situations during catheter insertion 2a are shown. The signal waveforms shown there symbolize different characteristic signal waveforms (Dd)', (Dd)", (Dd)‴ of the previously described comparison signal.

[0062] In the first position ( Fig. 10 ) the catheter tip 5a ( Fig. 9 The first, second, and third electrodes 6, 7, 13 are located outside atrium A in the superior vena cava V. In the second position ( Fig. 11 ) the catheter tip 5a is advanced further towards atrium A. The first electrode 6 is located inside and the second and third electrodes 7, 13 are located outside atrium A. In the third position ( Fig. 12 The catheter tip 5a is advanced further, with only the third electrode 13 still located outside atrium A. The resulting different voltages between electrodes 6, 7, and 13 lead to the different signal waveforms shown as examples. These can be compared to the results obtained using the Fig. 4 bis 6 The described procedure for controlling the position of the catheter tip is based on this. The inventors recognized that the additional, third electrode 13 allows for greater reliability in signal acquisition. This ultimately enables more reliable and / or precise control of the position. The same applies to controlling the orientation.

Claims

1. A medical system (1, 1a) for checking a position and an orientation of a catheter tip (5, 5a) in a patient's body, having a catheter (2, 2a), in particular a central venous catheter, with the catheter tip (5, 5a) on which at least a first electrode (6) and a second electrode (7) are arranged, the second electrode (7) being spaced apart from the first electrode (6) in the proximal direction, wherein the first electrode (6) is configured to detect a first electrical potential (P1) and to generate a first signal (S1) which represents a time curve of the first electrical potential (P1), and wherein the second electrode (7) is configured to detect a second electrical potential (P2) and to generate a second signal (S2) which represents a time curve of the second electrical potential (P2), an evaluation device (3, 3a) which is connected to the first electrode (6) and the second electrode (7), wherein the evaluation device (3, 3a) is configured to generate a differential signal (D) as a function of the first signal (S1) and the second signal (S2), wherein the differential signal (D) represents a time curve of an electrical voltage between the first electrode (6) and the second electrode (7), wherein the evaluation device (3, 3a) is configured to compare the differential signal (D) with a reference signal (R) which represents a desired position and orientation of the catheter tip (5, 5a), and wherein the evaluation device (3, 3a) is configured to detect and evaluate a change in sign of the differential signal (D), wherein the change in sign represents a change in a polarity of the first electrode (6) and the second electrode (7).

2. The medical system (1, 1a) as claimed in claim 1, characterized by an output device (4) which is connected to the evaluation device (3, 3a) and is configured to output the differential signal (D) and / or a check signal which represents a deviation between the differential signal (D) and the reference signal (R).

3. The medical system (1a) as claimed in one of the preceding claims, characterized in that at least one further, third electrode (13) is arranged on the catheter tip (5a) and is spaced apart from the second electrode (7) in the proximal direction, wherein the third electrode (13) is configured to detect a third electrical potential (P3) and to generate a third signal (S3) which represents a time curve of the detected third electrical potential (P3), wherein the evaluation device (3a) is connected to the third electrode (13) and is configured to generate a further differential signal (d) as a function of the second signal (S2) and the third signal (S3), the further differential signal (d) representing a time curve of an electrical voltage between the second electrode (7) and the third electrode (13), and wherein the evaluation device (3a) is configured to compare the further differential signal (d) and the differential signal (D).