Blood pump

Abstract

To provide a blood pump that is easy to handle.SOLUTION: A blood pump comprises: a flexible drive shaft (3); a conveying element (6) connected to the drive shaft (3) in a distal region of the drive shaft (3); and a motor (7). The motor (7) comprises a stator (36), and a rotor (30). The stator (36) comprises a winding (37). The rotor (30) comprises a rotor magnet (31). The drive shaft (3) is connected to the rotor (30) at a proximal end part of the drive shaft (3). The stator (36) and the rotor (30) are non-detachably connected to each other, and form a gap (40) defined by the rotor (30) and the stator (36).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present application relates to a blood pump according to the preamble of claim 1. In particular, the present application relates to a blood pump equipped with a motor. [Background technology]

[0002] Blood pumps with a proximal and distal end and a catheter arranged therebetween, inside which a flexible drive shaft is guided, are known in the state of the art. Such blood pumps usually comprise a pump head at the distal end, which comprises a foldable housing and a foldable delivery element, which delivery element is connected to the distal region of the drive shaft. Such a pump head can be guided to hard-to-reach locations. For example, such a pump head can be inserted through the femoral artery via the aortic arch into the region of the aortic valve of a patient in order to deliver blood from the left ventricle of the heart to the aorta. The drive shaft is driven at the proximal end of the blood pump by a motor, which is usually located outside the patient's body. Such blood pumps are described, for example, in the document EP 2 868 331 A2.

[0003] The document US Patent No. 4,895,557 discloses a motor arrangement for a drive device of a blood pump. The motor arrangement comprises a sterilizable, liquid-tight rotor housing, in which the rotor is located. The rotor housing is designed such that, during operation, the rotor is guided into a recess in the stator housing such that the rotor is surrounded by the stator. After operation, the rotor housing is withdrawn from the recess in the stator housing and disposed of.

[0004] A drawback of such a motor configuration is that it is rather bulky, which may cause problems, especially when fixing the motor configuration to the patient's leg.Furthermore, such a motor configuration may generate a significant amount of undesirable heat during operation.Furthermore, there is also the drawback that the stator may become quite contaminated during assembly of the system, for example by impurities on the user's gloves, which may require extensive cleaning and sterilization of the reusable stator. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to propose an easy-to-handle blood pump which overcomes the drawbacks of the known devices mentioned above. [Means for solving the problem]

[0006] This object is achieved by a blood pump with the features of the main claim. Further developments can be made from the features and embodiments of the dependent claims.

[0007] The proposed blood pump comprises a flexible drive shaft guided in a catheter, a delivery element connected to the drive shaft at a distal region of the drive shaft, and a motor comprising a stator and a rotor rotatably mounted in the stator, the stator comprising windings and the rotor comprising rotor magnets, and the drive shaft is further connected to the rotor at a proximal end of the drive shaft, the stator and the rotor being non-releasably connected to each other and forming a gap defined by the rotor and the stator.

[0008] The proposed blood pump can be constructed compactly, in particular in comparison with the modular construction of the motors of blood pumps known from the state of the art, in which the rotor and the stator are designed to be removable by the user. In the proposed blood pump, the stator and the rotor form one unit and can be connected to each other, for example, by friction or material joints. Due to the compact construction, a lighter motor can be realized, which is therefore less stressful when fixed to the patient's leg.

[0009] The windings can have an inner diameter that corresponds to at most 1.5 times, preferably at most 1.25 times, particularly preferably at most 1.15 times, the outer diameter of the rotor magnet. The distance between the windings and the rotor magnets results in a magnetic air gap. A small distance between the rotor magnets and the windings allows for an efficient conversion of electrical power into pump power, thus allowing low heat losses of the motor when operating at the desired pump power. Due to the single-component construction of the proposed motor, no housing parts are required in the magnetic air gap, allowing a small distance between the windings and the rotor magnets to be realized compared to constructions in which the stator and the rotor are designed to be housed separately. Given an inner diameter of the windings of 6 mm, the outer diameter of the rotor magnets can be, for example, larger than 5.25 mm.

[0010] For example, the radial distance between the windings and the rotor magnets may be at most 2 mm, preferably at most 1.25 mm, particularly preferably at most 0.75 mm.

[0011] The gap usually has a circular cross section. The gap has a width that corresponds to or is smaller than the width of the magnetic gap. The gap is conceivable to have a width of at most 1 mm, preferably at most 0.5 mm, particularly preferably at most 0.25 mm. Also conceivable is a gap having a width of at least 0.1 mm, preferably at least 0.15 mm, particularly preferably at least 0.2 mm.

[0012] Further, a rinse opening may be provided that is fluidly connected to the gap. The rinse opening may be fluidly connected to a rinse connection. The fluid connection may be located, for example, at a proximal end of the motor.

[0013] Furthermore, the gap can be considered to be fluidly connected to the intermediate space formed between the catheter and the drive shaft. This allows the rinsing fluid to flow through the gap via the rinse connection into the intermediate space between the drive shaft and the catheter. This allows lubrication of the drive shaft in the catheter. Furthermore, by introducing the rinsing fluid through the rinse connection, it is possible to prevent the patient's blood from entering the motor, in particular the gap. The rinsing fluid can also be introduced into the patient's body through the intermediate space between the rinse connection, the gap and the catheter drive shaft. For example, a glucose solution is used as the rinsing fluid.

[0014] The rinse fluid can be thought of as washing around the rotor from the proximal end to the distal end.The rinse fluid can also be thought of as washing around the rotor from the distal end to the proximal end.

[0015] Forward and return rinsing can also be achieved using a catheter with several lumens, as described, for example, in US Patent No. 4,895,557, in which case two or more connections for the rinsing fluid can be provided on the motor.

[0016] To ensure that the rinsing fluid can flow through the gap, the gap may be considered to have a minimum width of 0.05 mm.

[0017] The windings can be considered to be potted in a potting compound. Potting the windings with a potting compound is suitable for closing and smoothing out any depressions that may occur in the surface of the windings. The potting compound can include a low viscosity material suitable for flowing into and filling the depressions.

[0018] The potting compound may be considered to form a portion of the stator that defines the gap. The potting compound may provide a substantially smooth boundary surface of the gap. The potting compound may include, for example, an epoxy resin. It may also be considered that the potting compound includes, for example, aluminum oxide, iron powder, or other thermally conductive substances that improve heat transfer. The potting compound may reduce the number of air bubbles that adhere to the stator after venting the gap.

[0019] The potting compound can prevent damage or corrosion of the windings from the rinsing fluid, or from particles carried by the rinsing fluid, and can also prevent particles from settling on the windings.

[0020] It is further conceivable that the potting compound contains a biocompatible material, which typically consists entirely of such material so that no harmful substances can be released to the patient via the rinse connection, for example it is conceivable to coat the windings with parylene.

[0021] It is also possible to consider the stator as comprising a liquid-tight sleeve having an essentially annular cross section, the liquid-tight sleeve defining the gap. For example, the sleeve can separate the windings of the stator from the rinsing fluid, thereby preventing the windings from being damaged by the rinsing fluid. It is also possible to consider the sleeve as constituting the part of the stator defining the gap.

[0022] The sleeve can also be designed so that not only the windings but other parts of the motor are protected from damage by being isolated from the rinsing fluid by the sleeve. For example, solder locations, which may be present in the motor, can be protected from corrosion by the sleeve.

[0023] The sleeve may, for example, comprise a plastic, in particular polyetheretherketone or polyethylene, or glass. It is also conceivable that the sleeve is made of an elastic plastic, including, for example, polyethylene. The sleeve serves to guide the rinsing fluid, but does not necessarily serve to mechanically stabilize the motor. It is therefore possible to manufacture the sleeve with a thin wall and / or from a flexible material. Furthermore, the outer shape of the motor or parts of the motor is not determined by the shape of the sleeve. It may therefore be advantageous for the sleeve to cover only a small part of the windings and / or rotor in the axial direction. For example, it is also conceivable that the sleeve has an axial length that is less than 1.5 times the axial length of the rotor magnets.

[0024] It can also be considered that the rotor is radially mounted by at least one plain bearing. For example, the rotor can be mounted by two plain bearings. The at least one plain bearing can, for example, comprise a non-magnetizable material and / or a ceramic material, in particular aluminum oxide, zirconium oxide, yttrium-stabilized zirconium oxide or silicon nitride. The plain bearing can further comprise a steel, in particular an implant steel. It can also be provided with a biocompatible coating, for example with diamond-like amorphous carbon.

[0025] It can further be considered that the rotor is radially mounted by at least one ball bearing. This at least one ball bearing can be considered to comprise a non-magnetizable material. In particular, the parts of the ball bearing where wear occurs due to the operation of the motor can be considered to comprise or consist of a non-magnetizable material. This ensures that wear debris from those parts of the ball bearing do not adhere to ferromagnetic components of the motor. This can, for example, prevent ferromagnetic wear debris from remaining attached to the rotor and damaging it. It can further prevent ferromagnetic wear debris from damaging the windings or other components of the motor.

[0026] For example, the at least one ball bearing can include balls having a ceramic material. Additionally, the at least one ball bearing can include a cage including a plastic. The cage can include, for example, polyethylene or polytetrafluoroethylene. The balls can be entirely made of a ceramic material. The cage can be entirely made of a plastic.

[0027] Typically, the rotor comprises a coating and / or a cover to protect the rotor magnets. The coating and / or cover may also constitute parts of the rotor that define the gap. The coating and cover may comprise or consist of a biocompatible material. For example, a coating of parylene or a biocompatible epoxy resin may be provided. A coating of diamond-like amorphous carbon may also be provided. The coating may have a thickness of less than 100 μm, preferably less than 10 μm. The rotor may comprise, for example, a coating of polyetheretherketone or stainless steel.

[0028] The blood pump can include a deployable pump head including a delivery element and a housing that are designed to automatically deploy after being forcefully compressed. The deployable pump head allows the pump head and delivery elements to be of a relatively large design while still allowing for a relatively small diameter hole for inserting the blood pump into the patient's tissue.

[0029] Typically, the pump is configured to pump blood from a ventricle into a patient's blood vessel when the motor is located outside the patient's body. The motor may be configured to be fixed to the patient's thigh, for example.

[0030] To that end, the flexible drive shaft has a sufficient length, as determined by the patient's anatomy. Typically, the flexible shaft in this case has a length of at least 50 cm, preferably at least 90 cm. The maximum length of the flexible drive shaft is 200 cm, preferably 150 cm.

[0031] The use of blood pumps driven by a motor located outside the patient's body may require higher efficiency demands to be met compared to blood pumps driven by a motor inside the patient's body. Removal of heat generated during operation via the patient's blood system is advantageous, for example, for motors located inside the patient's body. In contrast, pumps that generate heat and are located outside the patient's body may, in certain circumstances, require additional elements for heat dissipation or a particularly efficient method of operation.

[0032] The present application further relates to a proposed method of operating a blood pump, using which the accessible surfaces of the motor housing heat up to a temperature below 60° C., preferably below 48° C., particularly preferably below 43° C., during continuous operation at a speed of 15000 rpm, preferably at least 30000 rpm. It is important that the motor housing does not heat up too much during operation, especially when the motor is fixed to the patient's thigh.

[0033] Further contemplated is an operating method in which the accessible surfaces of the motor housing are heated to a temperature of 60°C or less, preferably 48°C or less, particularly preferably 43°C or less, during continuous operation of the blood pump at a delivery rate of at least 1 l / min, preferably at least 2 l / min.

[0034] It is also conceivable that the blood pump includes a cooling body, for example with cooling ribs thermally connected to the motor, or a heat tube for dissipating heat generated during operation. It is also conceivable that the blood pump is configured to dissipate heat to the patient's tissue, for example through the skin of the thigh.

[0035] The blood pump with all the described components can be delivered in a sterile package. The blood pump can be sterilized, for example, by gamma sterilization or using ethylene oxide. The blood pump can be disposed of in its entirety after use. Thus, with the proposed blood pump, the user does not have to repeatedly clean or sterilize the parts of the blood pump, especially the motor.

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Brief description of the drawings]

[0037] [Figure 1] FIG. 2 is a schematic diagram showing a pump configuration. [Diagram 2] FIG. 2 is a schematic diagram showing a pump head. [Figure 3(a)] FIG. 13 is yet another schematic diagram showing the pump head. [Figure 3(b)] FIG. 13 is yet another schematic diagram showing the pump head. [Figure 4] FIG. [Diagram 5] FIG. 2 is a schematic diagram showing a motor. [Figure 6] FIG. 13 is a schematic diagram showing another motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] FIG. 1 is a schematic diagram of a pump arrangement 1. The pump arrangement 1 comprises a catheter 2, in which a flexible drive shaft 3 is guided. The catheter 2 is connected to a pump head 4. The pump head 4 comprises a housing 5 and a delivery element 6 arranged in the housing 5, which can be driven via the drive shaft 3 by a motor 7 connected to the proximal end of the drive shaft 3. The pump head 4 with the catheter 2 and the drive shaft 3 are introduced into the femoral artery 9 through a port 8, so that the pump head 4 in the region of the left ventricle 10 is located in the region of the aortic valve 11. In operation, the drive shaft 3 is driven by the motor 7 and the pump arrangement 1 delivers blood from the left ventricle 10 into the aorta 12. In the illustrated configuration for left heart support, the delivery direction of the pump arrangement 1 corresponds to the direction from the distal end 13 of the pump arrangement 1 towards the proximal end 14 of the pump arrangement 1.

[0039] However, the pump arrangement 1 may also be configured to deliver blood in a direction from the proximal end 14 towards the distal end 13 of the pump arrangement 1, suitable for right heart assistance, for example.

[0040] The pump head 4 is shown diagrammatically in FIG. 2. Features that are repeated in FIG. 2 and the following figures are provided with the same reference numbers. The pump head 4 comprises a delivery element 6 and a housing 5. The delivery element 6 in this example is designed as a pump rotor with two flexible sections in the form of rotor vanes. Furthermore, a drive shaft 3 is shown, which is attached to the distal region 15 of the pump head 4. A so-called pigtail 17, which is made of an elastically deformable material, is provided at the distal end 16 of the pump head 4. A cylindrical element 18 is rigidly connected to the drive shaft 3. The delivery element 6 is fixed to the cylindrical element 18. The delivery element 6 and the housing 5 are of deployable design, such that they can be deployed automatically after being forcibly compressed. The delivery element 6 is made of plastic. The housing 5 is made of the shape memory material Nitinol. The deployable design of the delivery element 6 and the housing 5 allows the entire pump head 4 to be deployed.

[0041] The housing 5 is designed as a diamond grid 19 and is provided with an elastic covering 21 made of polyurethane in the liquid-tight areas 20. The elastic covering 21 covers the inside and outside of the diamond grid 19 so that the diamond grid openings formed by the grid 19 in the liquid-tight areas 20 can be closed in a liquid-tight manner by the elastic covering 21.

[0042] The housing 5 further comprises an inlet region 22 which is not covered by the elastic covering 21. In the inlet region 22, the diamond lattice openings serve as inlet openings, one of which is shown for illustrative purposes with the reference number 23 in Fig. 2. The housing 5 comprises an outlet region 24 which is also not covered by the elastic covering 21. In the outlet region 24, the diamond lattice openings serve as outlet openings, one of which is shown for illustrative purposes with the reference number 25.

[0043] In operation of the pump arrangement 1, the drive shaft 3 is driven by the motor 7, causing the delivery element 6 connected to the drive shaft 3 to rotate about its axis. This causes blood to be transported into the housing 5 through an inlet opening in the inlet region 22 and then out of the housing 5 through an outlet opening in the outlet region 24. Blood is thus delivered by the pump arrangement 1 in a delivery direction 26.

[0044] The elastic covering 21 does not completely surround the entire axial length of the delivery element 6. The delivery element 6 projects partway into the exit region 24 such that at least the exit opening, indicated by reference number 25, is located laterally, i.e. radially adjacent to the delivery element 6. In contrast, the elastic covering 21 at the distal end is designed such that the delivery element 6 does not project at all or significantly into the entrance region 22 and is therefore not surrounded laterally by the entrance opening.

[0045] The design of the elastic membrane 21 and the delivery element 6, and their arrangement relative to each other, are such that approximately one third of the axial length of the delivery element 6 is not surrounded by the elastic membrane 21 forming the liquid-tight region 20. In the example shown, this axial length of the delivery element 6 is surrounded by the outlet region 24.

[0046] The pump head 4 further comprises an outflow element, which can be designed as an outflow shield 27 as shown in figure 3(a) or as an outflow tube 27' as shown in figure 3(b).

[0047] The outflow shield 27 shown in Fig. 3(a) is fixed to the housing 5 in the liquid-tight region 20 of the housing 5. The outflow shield 27 has the shape of a frustoconical lateral surface and extends in the delivery direction 26 so as to widen towards the delivery direction 26. The delivery element 6 and the exit region 24 are surrounded by the outflow shield 27. In another embodiment, it is also conceivable that the exit region 24 is partially surrounded by the outflow shield 27.

[0048] The pump head 4 of FIG. 3(b) differs from the pump head 4 shown in FIG. 3(a) only in that instead of the outflow shield 27 an outflow tube 27' is provided. This outflow tube 27' is fixed to the housing 5 in the liquid-tight region 20 and extends therefrom in the delivery direction 26. The outflow tube 27' is made of polyurethane and comprises openings 28, 28', 28'' in the region located in the delivery direction 26. In the example shown, the outlet region 24 is completely surrounded by the outflow tube 27'. The outflow tube 27' is flexible and closes automatically by pressing against the catheter 2 and / or the housing 5 in the event of a blood flow in the direction opposite to the delivery direction 26.

[0049] FIG. 4 is a schematic diagram of a diamond-shaped grid 19 of the housing 5. Also shown are the liquid-tight area 20 with the elastic covering 21, as well as the inlet area 22 and the outlet area 24. Both areas have a conical shape, while the liquid-tight area 20 is essentially tubular. The grid 19 comprises grid struts, one of which is given the reference number 45 for illustrative purposes. The grid struts 45 run in such a way that the essentially diamond-shaped grid openings are larger in the inlet area 22 and the outlet area 24 than in the liquid-tight area 20. In FIG. 4, for the sake of clarity, the grid struts on the far side of the housing 5 are only shown with dotted lines.

[0050] In the liquid-tight region 20, the lattice struts 45 form a relatively fine mesh-like lattice. The lattice 19 comprises 32 struts along the circumference of the housing 5 in the liquid-tight region 20, or 16 nodes if this circumference is considered at the axial position of the housing 5 with the nodes. Such a dense mesh-like lattice 19 results in an approximately circular cross section of the housing 5 in the liquid-tight region 20.

[0051] The number of lattice struts 45 along the periphery of the housing 5 is halved by connecting the lattice struts in pairs from the liquid-tight region 20 in the direction towards the inlet region 22 and the outlet region 24, so that in the corresponding regions the housing 5 comprises 16 lattice struts 45 along the periphery without nodes. The number of lattice struts 45 is then reduced again by connecting the lattice struts in pairs in the direction towards the inlet region 22 and the outlet region 24, so that in these regions the housing 5 comprises eight lattice struts 45. Furthermore, the number of lattice struts 45 is further reduced in the manner described above in the outlet region 24, so that in the region further in the delivery direction 26 the housing 5 has only four lattice struts 45 along the periphery.

[0052] By reducing the number of grid struts 45 as described above, a grid 19 is formed that has larger grid openings in the inlet and outlet regions 22 and 24 than in the liquid tight region 20 .

[0053] The lattice struts 45 in the outlet region 24 and the conical region of the inlet region 22 form a helical structure which ensures that the pump head 4 deploys when pushed out of the cannula.

[0054] 5 is a schematic diagram showing the motor 7. In the region of the shaft stub 29, the motor 7 is connected to the catheter 2, which is glued to the shaft stub 29. The flexible drive shaft 3 is guided within the catheter 2. The motor 7 further comprises a rotor 30 with a rotor magnet 31.

[0055] The flexible drive shaft 3 is connected to a rotor 30 such that as the rotor 30 rotates, torque is transferred from the rotor 30 to the flexible drive shaft 3. This torque is transferred via the flexible drive shaft to a delivery element 6, the pump arrangement being driven by a motor 7.

[0056] The rotor 30 is axially mounted by two bearings 32, 33. One of these bearings, the bearing 33, is biased by a spring element 34 for axially stabilizing the rotor 30. The spring element 34 may be designed, for example, as a coil spring or an annular spring. The bearings 32, 33 may each be designed as a ball bearing or a plain bearing. If the bearings 32, 33 are designed as ball bearings, they comprise ceramic balls and a plastic cage, such that the ball bearings have a non-magnetizable material. The rings of the bearings can be designed, for example, from a magnetizable metal or from a non-magnetizable material. If the bearings 32, 33 are designed as plain bearings, they comprise, respectively, DLC-coated implant steel and yttrium-stabilized zirconium oxide.

[0057] The rotor magnets 31 include a biocompatible DLC coating. The motor 7 further includes a stator 36. The stator 36 includes a number of windings 37 that are conductively connected to electrical connections 38. The stator 36 further includes back-iron laminations 39. The windings 37 are potted with a biocompatible epoxy resin that includes thermally conductive aluminum oxide.

[0058] A gap 40 with an annular cross section is formed between the inside of the coating of the winding 37 and the outside of the coating 35 of the rotor magnet 31. The gap 40 has a width of 0.2 mm. This gap 40 is fluidly connected with a rinse opening 41 connected to a rinse connection 42, which is arranged at the proximal end of the motor 7. The gap 40 is further fluidly connected with an intermediate space formed between the drive shaft 3 and the catheter 2. Thus, for example, a glucose solution can be flowed through the rinse opening 41 and the gap 40 as well as the intermediate space via the rinse connection 42. The glucose solution thus flows around the rotor 30 during operation. The radial distance between the outside of the rotor magnet 31 and the inside of the winding 37 is 0.5 mm. Here, the inner diameter of the winding 37 corresponds to 1.1 times the outer diameter of the rotor magnet 31.

[0059] The stator 36 and the rotor 30 are connected to each other in such a way that they cannot be released by the user and are integrated into a motor housing 43, which can be connected to a grip or a cooling body, for example. The motor can be operated very efficiently due to the very small distance between the windings 37 and the rotor magnets 31, so that the motor housing 43 and the grip or cooling body, which may be connected to this housing, heat up to less than 40° C. on the exposed surfaces when the pump arrangement 1 is operated at a speed of 32000 rpm and a delivery output of 2.5 l per minute.

[0060] The motor 7' shown in FIG. 6 differs from the motor 7 shown in FIG. 5 only in that the stator 36 in this embodiment comprises a liquid-tight sleeve 44 that defines the gap 40. In this embodiment, the width of the gap 40 is, for example, 0.15 mm or 0.22 mm. The sleeve 44 is made of polyetheretherketone and is magnetically inert. The sleeve 44 is, for example, arranged such that the sleeve 44 separates the winding 37 and the rest of the stator 36 from a rinsing fluid that may possibly flow through the gap 40. The length of the sleeve 44 in the axial direction is about 1.2 times the axial length of the rotor magnet 31.

[0061] The features of the various embodiments, which are disclosed merely as examples, may be combined with one another and also claimed separately.

Claims

1. A blood pump comprising a flexible drive shaft (3) guided in a catheter (2), a delivery element (6) connected to the drive shaft (3) at its distal region, and a motor (7), the motor (7) comprising a stator (36) and a rotor (30) rotatably mounted in the stator (36), the stator (36) comprising windings (37), the rotor (30) comprising rotor magnets (31), the drive shaft (3) being connected to the rotor (30) at its proximal end, the stator (36) and the rotor (30) are non-removably connected to one another to define a gap (40) defined by the rotor (30) and the stator (36); A blood pump, characterized in that said winding (37) is potted in a potting compound.

2. A blood pump as described in claim 1, characterized in that the potting compound is biocompatible.

3. A blood pump as described in claim 2, characterized in that the potting compound includes a low viscosity material suitable for flowing into and filling recesses in the surface of the winding (37).

4. A blood pump as described in claim 2 or 3, characterized in that the potting compound forms a portion of the stator that defines the gap (40).

5. A blood pump as described in any one of claims 2 to 4, characterized in that the potting compound includes an epoxy resin and / or the potting compound includes aluminum oxide or iron powder.

6. A blood pump as described in any one of claims 1 to 5, characterized in that the rinsing fluid washes around the rotor (30) from the distal end toward the proximal end.

7. A blood pump as claimed in any one of claims 1 to 5, characterized in that the rinsing fluid washes around the rotor (30) from the proximal end towards the distal end.

8. A blood pump as described in any one of claims 1 to 7, characterized in that the stator (36) is provided with a liquid-tight sleeve (44) having an essentially annular cross-section, and the gap (40) is defined by the liquid-tight sleeve (44).

9. A blood pump as described in claim 8, characterized in that the sleeve (44) has an axial length that is less than 1.5 times the axial length of the rotor magnet (31).

10. A blood pump as described in any one of claims 1 to 9, characterized in that the rotor (30) is radially mounted by at least one plain bearing.

11. A blood pump as described in claim 10, wherein at least one of the sliding bearings comprises a non-magnetizable material.

12. A blood pump as claimed in claim 10, wherein the sliding bearing comprises steel.

13. A blood pump as described in claim 10, wherein the sliding bearing includes a biocompatible coating of diamond-like amorphous carbon.

14. A blood pump as claimed in any one of claims 1 to 13, characterized in that the rotor is radially mounted by at least one ball bearing.

15. A blood pump as described in claim 14, wherein at least one of the ball bearings comprises a non-magnetizable material.

16. A blood pump as described in claim 14 or 15, wherein at least one of the ball bearings has balls comprising a ceramic material.

17. A blood pump as claimed in any one of claims 14 to 16, wherein at least one of the ball bearings has a retainer comprising plastic.

18. A blood pump as described in any one of claims 1 to 17, characterized in that the gap (40) is fluidly connected to an intermediate space formed between the catheter (2) and the drive shaft (3).

19. A blood pump as described in any one of claims 1 to 18, characterized in that the rotor (30) has a coating and / or cover for protecting the rotor magnet (31).

20. A blood pump as described in any one of claims 1 to 19, characterized in that the blood pump is configured to pump blood from a ventricle to a patient's blood vessel when the motor (7) is positioned outside the patient's body.

21. A blood pump as described in any one of claims 1 to 20, characterized by an expandable pump head (4) including the delivery element (6) and a housing (5), wherein the delivery element (6) and the housing (5) are designed to automatically expand after being forcibly compressed.

22. A blood pump as described in any one of claims 1 to 21, characterized in that the gap (40) has a width of at least 0.1 mm, preferably at least 0.15 mm, particularly preferably at least 0.2 mm.

23. A method for operating a blood pump as described in any one of claims 1 to 22, characterized in that the contactable surfaces of the housing (43) of the motor (7) are heated to a temperature of not more than 60°C, preferably not more than 48°C, particularly preferably not more than 43°C, during continuous operation at a speed of 15,000 rpm, preferably at least 30,000 rpm.

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