Compressible rotor for a fluid pump

Abstract

Compressible rotor (2,15) for a fluid pump (1) with at least one blade (20,25,26) and with at least one deformable cavity (27,28,29) filled or fillable with a fluid.

Description

[0001] The present invention is in the field of mechanical engineering, in particular precision engineering, and relates to rotors for fluid pumps.

[0002] Rotary pumps are well known, but they are constantly being improved, especially for specialized applications. Axial pumps have become known, for example, which feature a rotor that conveys fluid in an axial direction within a housing. The rotor and housing are deformable, preferably compressible, to allow them to be moved to a desired, difficult-to-access location before operation, where they can be decompressed and operated.

[0003] Such pumps are used in micro-design, for example in medicine, to be introduced into the body of a patient, for example via a bloodstream, and to be operated there, either in the blood vessel or in a heart chamber.

[0004] The pumps can be compressed in such a way that they can be pushed through the blood vessel and then, if necessary, decompressed in a larger body cavity to unfold the rotor and achieve high flow rates.

[0005] A compressible rotor is known, for example, from US 6 860 713 B2.

[0006] Other rotors are known from US Pat. No. 7,393,181 B2 and FR 2,329,874 A1. These documents do not show a compressible rotor with at least one blade and a deformable cavity filled or fillable with a fluid. The known solutions are based either on the elasticity and deformability of the rotor material or on mechanical designs such as the provision of kinks or joints for folding and unfolding the individual components.

[0007] Such designs often have the disadvantage that compressibility is limited, since, for example, the hub of a rotor remains unchanged, that complex joints have to be provided that are stabilized during operation, and that superelastic materials are sometimes used, such as shape memory alloys, which change their shape depending on the ambient temperature.

[0008] These designs often require the use of composite materials, and it is difficult to construct support structures without impeding the flow of the fluid being pumped and, if necessary, to largely exclude damage to the fluid. This is particularly important when pumping blood, which contains highly functional and mechanically vulnerable components.

[0009] Against the background of the prior art, the object of the present invention is to create a rotor in the simplest possible manner, which is structurally simple, highly reversibly compressible and reliable in operation.

[0010] The object is achieved according to the invention with the features of patent claim 1.

[0011] The rotor according to the invention for a fluid pump has at least one blade and at least one deformable cavity filled or fillable with a fluid.

[0012] This results in volume compressibility of the rotor, which, upon compression, already leads to a reduction in the rotor volume and, if necessary, the rotor diameter. In addition, the various components of the rotor, such as the blades, can be bent and pressed toward the rotor axis to further reduce the diameter.

[0013] The rotor is thus characterized by a material mixture or a material that can be converted from a first, lower density or a first lower specific gravity to a second, higher density or a higher specific gravity through compression. The cavities can be closed and filled with a gas such as air or nitrogen, or a noble gas or another bio-inert gas that is easily compressible in volume under pressure.

[0014] Such closed cavities tend to expand again due to gas elasticity when the external pressure force is removed, so that the rotor can unfold automatically once it has been brought to the deployment site. At the very least, the unfolding movement is assisted by the gas elasticity.

[0015] However, gas lines can also be provided to the rotor, which terminate in one or more cavities and allow the cavities to be actively inflated. The same lines can also be used to extract the gas for compression if necessary.

[0016] A similar procedure can be used with a liquid if it is introduced into the cavities. If a liquid is present in the cavities, it is usually much less compressible. However, by choosing the appropriate viscosity in conjunction with the other structural components of the rotor, it can enable high mobility and thus compressibility, while still supporting a certain degree of rotor stability during operation due to its incompressibility after the rotor unfolds.

[0017] The cavities can also be designed open, which also provides high compressibility. The material defining the cavities must then be appropriately elastic. This can be achieved, for example, with an open-pore foam.

[0018] The invention can also be advantageously carried out in that the cavity(ies) is / are at least partially delimited by a partially permeable membrane.

[0019] For example, a body made of open-cell foam can be at least partially sealed on its exterior by a semipermeable membrane, or a closed-cell foam can be made of a partially permeable material. The membranes can be used to specifically transport substances, filling or emptying the cavity(ies), thus causing or supporting expansion / compression of the body.

[0020] A cavity may be filled with a liquid which, together with the membrane used and depending on the liquid in which the pump is used, in particular human blood, allows diffusion into the cavity(ies) due to osmosis, leading to an increase in pressure and to inflation of the rotor.

[0021] Likewise, substances can be used as cavity-limiting material or as filling of the cavities, which, after coming into contact with the liquid to be pumped, lead to swelling processes as a result of absorption of the liquid and thus support decompression of the rotor via an increase in volume.

[0022] Depending on the cavity filler materials and the substances to be permeated or retained, microfiltration membranes (0.5-0.1 µm particle size), ultrafiltration membranes (0.1-0.01 µm particle size), and nanofiltration membranes (1-10 nm) can be used as semi-permeable membranes to define cavities. Regardless of the particle size, biological or synthetic membrane materials can be used (for biological materials, for example, Cuprophan, Hemophan, or cellulose triacetate; for synthetic membranes, for example, Teflon or Goretex).

[0023] Synthetic materials generally exhibit higher water permeability and are often hydrophobic themselves. Synthetic materials that can be used include polysylphon, polyamide, polyacrylonitrile, and their copolymers, as well as polymethyl methacrylate, polytetrafluoroethylene, and their derivatives.

[0024] High-flux membranes are advantageously used, as they allow molecules up to a molecular weight of 50,000 Daltons to pass through and ensure rapid mass transport.

[0025] Advantageously, the material is chosen so that it retains germs / bacteria / microorganisms, which prevents contamination or infection.

[0026] In the case of the osmosis process, it is advisable to fill the cavities with a salt or a salt solution whose salt concentration is higher than that of the liquids to be pumped.

[0027] Advantageously, it can also be provided that at least the majority of the cavities are surrounded by solid material of the rotor and connected to each other via openings. In this case, fluid can be transported through the cavities and, if necessary, out of the rotor during compression, so that the corresponding cavities can be easily and completely compressed.

[0028] The rotor can, for example, be partially made of a porous material such as foam, particularly polyurethane. Such foam can be open- or closed-pore. In the case of an open-pore foam, the elasticity is based on the supporting material surrounding the pores, which spontaneously returns to its original shape after compression, allowing the gas or fluid to flow back into the pores, and / or on the elasticity of a filling gas if the open-pore foam body is completely surrounded by an impermeable or partially permeable outer layer. Due to the limited flow cross-sections of the connections between the cavities / pores, a time constant for compression / decompression can be selected within certain limits. This can ensure that sudden deformations of the rotor caused by uneven mechanical loading are counteracted during pump operation.

[0029] The invention can also advantageously provide that the rotor has at least one cavity which has a greater extent in a first direction than in the directions substantially perpendicular thereto.

[0030] The provision of such anisotropic cavities, when correctly positioned, also allows the rotor to achieve anisotropic mechanical properties. This makes it possible to design the rotor to be radially compressible easily and with minimal force, without the same easy deformability occurring during operation due to the dynamic resistance of the fluid being pumped.

[0031] During operation, the rotor is thus stabilized against the axial and circumferential forces, while it offers relatively little resistance to radial compression.

[0032] The corresponding cavities can be round, hexagonal, triangular, or square in cross-section, for example, and can have a strand shape, so that their cross-section is essentially the same along their length. This creates a symmetry that contributes to the stability of the rotor.

[0033] Corresponding cavities can, for example, be provided particularly advantageously in at least one blade, since on the one hand these contribute the greatest part to the diameter reduction of the rotor and on the other hand they are exposed to the highest dynamic forces during operation.

[0034] Nevertheless, the blade can be designed so robustly that it is self-supporting, even eliminating the need for a hub. Such a blade can, for example, be formed as a flat body, particularly made of foam, that is helically bent around an axis. For example, a polyurethane foam sheet can be cut to a flat shape as desired, then twisted around an axis, and then hardened or stiffened. The shape of the blade is thus stabilized, while retaining elastic compressibility.

[0035] However, it may also be provided to produce such a blade or an entire rotor by injecting a foam into a prefabricated mold.

[0036] The invention can also be used in rotors provided with hubs, and in this case, in particular, the hub body can have the cavities according to the invention or can be made at least partially from a foam.

[0037] If anisotropic cavities are provided in the rotor, it is advantageous to align them with the direction of their greatest stability along the force / stress curves that arise within the rotor during operation.

[0038] For example, the longitudinal axes of strand-shaped hollow bodies, such as honeycomb bodies, can be aligned perpendicular to the blade surface in order to absorb the forces acting in this direction or circumferential direction.

[0039] The object of creating a rotor which is as simply constructed as possible, which is highly (in particular reversibly) compressible and reliable in operation, is also achieved by a compressible rotor for a fluid pump with at least one blade, wherein the rotor is constructed in such a way that it can assume a compressed and a decompressed state and the average density change of the rotor material between the compressed and decompressed state is at least 10%.

[0040] What's important in contrast to the state of the art is that the volume change is primarily caused by changes in the density of the rotor material. This is not simply a matter of elastic deformation processes, where the average density of the rotor material remains essentially constant. The aforementioned density change is "temperature-adjusted," meaning that the density change at a rotor temperature of, for example, 36°C is used as the basis for both the compressed and decompressed states.

[0041] The approaches described in this application can be used to achieve this density change. Both reversible and irreversible processes are possible. These include, for example, osmotic processes, but also processes that use open-cell or closed-cell foam.

[0042] The density change of the rotor does not have to be uniform at all points. For example, it is possible that a smaller density change is achieved in the area of ​​a hub or the blade because of the higher stiffness that may be desired there, and a stronger compression takes place in the area of ​​a virtual "joint" between the hub and the blade.

[0043] The average density change of the entire rotor can preferably be even greater, for example, at least 15%, or alternatively at least 20%. Based on a plastic, exemplary starting values ​​for the density are 0.01...2 g / cm 3 in the decompressed state and 0.05...3 g / cm 3 in compressed state.

[0044] In addition to a rotor of the type described, the invention also relates to a fluid pump with such a rotor, in which a compressible housing surrounding the rotor is provided.

[0045] According to the invention, the housing can also be made at least partially of a material with cavities, in particular of a foam, for example, polyurethane. In this way, the housing can be easily compressed and decompressed together with the rotor.

[0046] In the following, the invention is shown using an embodiment in a drawing and then described.

[0047] This shows Fig. 1 a schematic view of an axial pump in use in the body of a patient, Fig. 2 an enlarged view of a pump, partly in longitudinal section, Fig. 3 a rotor in three-dimensional view with hub, Fig. 4 a rotor without hub in three-dimensional view, Fig. 5 a part of an airfoil in a partially cutaway view with honeycomb-shaped cavities, Fig. 6 a section through a porous material, Fig. 7 three-dimensional a possible form of cavities, Fig. 8 three-dimensional another possible form of cavities, Fig. 9 a structure with circular cylindrical cavities, Fig. 10 a structure with hexagonal honeycomb cavities in densest arrangement and Fig. 11 a structure with octagonal honeycomb spaces and additional cavities in between.

[0048] Fig. 1 shows an axial pump 1 with a rotor 2 and a housing 3 inside a heart chamber 4 in a schematic view.

[0049] Within the heart chamber 4, blood is sucked in by the pump 1 through openings 5, as indicated by the arrows 6. The blood is expelled again within a blood vessel 7 in the direction of the arrows 8, thus replacing or supporting the pumping function of the heart.

[0050] The pump 1 is arranged at the distal end of a hollow catheter 8, which is inserted through the blood vessel 7 into the heart chamber 4 and whose proximal end protrudes through a sheath 9 from the blood vessel and ultimately from the patient's body.

[0051] A drive shaft 10 is provided within the hollow catheter 8, which can be driven by a motor 11 located outside the body at high speed, typically above 10,000 revolutions per minute. In the pump 1, the rotor 2 is connected to the shaft 10 and rotates with it.

[0052] During operation, the pump 1 has a larger diameter within the heart chamber 4 than during insertion through the blood vessel 7. In particular, it may have a larger diameter than the inner diameter of the blood vessel.

[0053] To remove the pump from the body, it is compressed again and pulled back through the sheath 9.

[0054] The Fig. Figure 2 shows schematically in enlarged form the pump, with the end of the hollow catheter 8 being shown in the lower area with a compression funnel 12.

[0055] The shaft 10 extends through the hollow catheter 8 and is rotatably mounted in a bearing 13 at the proximal end of the pump housing 3. The bearing can be designed to be tensile-resistant, so that the pump housing 3 can be retracted at least a short distance into the compression funnel 12 along the shaft 10 and thus simultaneously be radially compressed. The housing can also be retracted by means of an additional pull thread running through the hollow catheter.

[0056] The shaft 10 is connected to the hub body 14 of the rotor 15, which in turn is again rotatably mounted in a second bearing 17, either directly or via a shaft extension 16 at the distal end of the pump housing 3. This bearing can also be designed to be tensile-resistant in order to transmit tensile forces to the housing via the shaft 10 and the rotor 15.

[0057] The bearing 17 is mounted in a strut assembly 18 of the pump housing 3, which has enough openings to allow blood or other body fluids to flow to the rotor.

[0058] 19 denotes the front contour of the pump housing, which is designed in a grid-like manner in order to avoid direct contact with the rotor when the pump comes into contact with body tissue and to keep larger particles away during suction.

[0059] During insertion of the pump, the pump housing 3 and the rotor 15 can initially be strongly radially compressed and mounted at the distal end of the hollow catheter 8. After insertion into a heart chamber, the pump can then be pushed slightly out of the catheter 8 by means of the shaft and unfold automatically due to elastic effects. The pump housing 3 unfolds to the diameter shown, and at the same time, the blades 20 are oriented away from the hub body 14 and move away from the rotation axis 21.

[0060] As an alternative or in addition to the pushing movement via the shaft 10, the pump 1 can also be pushed out of the hollow catheter 8 by additional wires 22, 23, which are tightly guided in or on the hollow catheter and thus allow both pulling and pushing movements. These wires 22, 23 can be attached to a manipulation ring at the proximal end outside the patient's body, which can be pushed and pulled from the outside. The wires can, for example, be tightly guided and axially displaceable in guides on the outside of the hollow catheter.

[0061] The pump housing 3 can be made of an open-cell foam or a closed-cell foam, thus being elastic. However, larger cavities can also be provided therein, which can be sucked out or filled with a fluid, for example, by means of a hose 24 connected to a gas reservoir or a pump at the proximal end, in order to compress or expand / decompress the pump.

[0062] With the compression movement of the housing, the rotor 15 can also be compressed by radial pressure exerted on it. However, the rotor can also be compressed independently by suctioning a fluid from corresponding cavities, or its compression can at least be assisted by such an effect.

[0063] However, a corresponding compression and decompression effect can also be achieved simply by pushing the pump out of the hollow catheter and pulling it into the compression nozzle 12.

[0064] In the Fig. Figure 3 shows a three-dimensional view of a rotor with a rotating blade 25. The rotor and blade can be made in one piece, for example, from a foam material, e.g., polyurethane. Alternatively or additionally, larger cavities can also be provided, particularly in the hub, but also in the blade 25.

[0065] Fig. 4 shows a self-supporting blade 26, which can be made of a foam, for example, and is designed without a hub. It is cut, for example, from a flat material and twisted at the proximal and distal ends relative to each other about a longitudinal axis 21 to create the corresponding helical shape. For example, such a blade can be made of a foam, cut accordingly from a flat foam material, then formed into the helical shape, and subsequently heated to stabilize the helical shape after cooling. After that, the body is stable enough to maintain the desired shape during pumping operation, but can still be radially compressed upon application of an appropriate compression force.

[0066] In the Fig. Figure 5 schematically shows a section of an airfoil 26, showing that honeycomb-shaped cavities 27, which are hexagonal in cross-section, are perpendicular to the airfoil surface with their longitudinal axes 33. In this way, a highly anisotropic stability can be achieved, which means that the airfoil can exert large forces on a fluid in the direction perpendicular to its conveying surface and in the circumferential direction without significantly deforming, but that the airfoil is more easily compressible by the action of radial forces with respect to its axis of rotation.

[0067] Instead of the honeycomb-shaped cavities 27, cavities with a different cross-section shape are also conceivable, as shown in the Fig. 7-11. Fig. 7 cuboid cavities, Fig. 8 cavities in strand form with rounded cuboid shape, Fig. 9 circular cylinders, Fig. 10 hexagonal honeycombs in densest packing and Fig. 11 octagonal honeycombs in a loose arrangement with square spaces in cross-section.

[0068] Within a hub body, if present, such cavities can be aligned, for example, with their longitudinal axes in the circumferential direction relative to the axis of rotation 21 of the hub.

[0069] Fig.Figure 6 shows a greatly enlarged, microscopic view of a foam 32 with closed pores 28, 29, wherein in one variant (cavity 28), the material of the walls between the pores is designed as a semipermeable membrane. Such a membrane allows the diffusion of certain liquids, which can be used, for example, for an osmotic effect. If, for example, the cavities / pores 28 are filled with a liquid in which a salt is dissolved in high concentration, and the foam is placed in a liquid with a lower solution concentration, the constellation tends to bring the concentrations of both liquids closer together by the solvent diffusing from the outside into the interior of the cavity 28 through the membrane 30. This creates an increased osmotic pressure, which can be used to inflate the cavity 28 to the shape shown in dashed lines.This allows expansion and stiffening of the foam.

[0070] This effect can also be used specifically for larger cavities in the rotor body. Alternatively, swelling processes can also be used to expand the rotor.

[0071] In connection with the cavity 29, a hose 31 is shown, which symbolizes that corresponding cavities can also be filled with a fluid via individual or collective supply lines or that such a fluid can be sucked out of them in order to control corresponding decompression / compression processes.

[0072] The invention thus creates a rotor that is highly compressible, and its manufacture can largely be made from materials already commonly used in other applications, most of which have already been proven in the medical field. Despite the high possible degree of compression, this ensures reliable functioning of a corresponding fluid pump.

[0073] The present subject relates, inter alia, to the following aspects: 1. Compressible rotor for a fluid pump with at least one blade and with at least one deformable cavity filled or fillable with a fluid, characterized in that the cavity(ies) is / are at least partially delimited by a partially permeable membrane. 2. Rotor according to aspect 1, characterized in that the cavity(ies) is / are closed. 3. Rotor according to aspect 1 or 2, characterized in that the at least one cavity is filled with a liquid which, in cooperation with the membrane and a liquid in which the pump can be used, in particular blood, causes osmotic diffusion into the cavity with a corresponding increase in pressure. 4. Rotor according to aspect 1 or one of the following, characterized in that a part of the cavities is surrounded by solid material of the rotor and is connected to the outside area and / or to each other via openings. 5. Rotor according to aspect 1 or one of the following, characterized in that the rotor consists at least partially of a porous material, in particular foam. 6. Rotor according to aspect 1 or one of the following, characterized by at least one cavity which has a greater extent in a first direction than in the directions substantially perpendicular thereto. 7. Rotor according to aspect 6, characterized in that the cavity(ies) is / are round or polygonal in cross-section, in particular octagonal, hexagonal, triangular or square. 8. Rotor according to aspect 6 or 7, characterized in that the cavity(ies) have a strand shape. 9. Rotor according to aspect 7 or 8, characterized in that the cavities are aligned with the direction of their greatest stability, in particular their longitudinal axis, in the direction of the compressive forces occurring within the rotor during operation. 10. Rotor according to aspect 1 or one of the following, characterized in that the cavity(ies) is / are provided in at least one blade. 11. Rotor according to aspect 1 or one of the following, characterized in that the blade is self-supporting and hubless. 12. Rotor according to one of aspects 1 to 11, characterized in that the cavity(ies) are provided in a hub body. 13. A fluid pump having a rotor according to any one of aspects 1 to 12, characterized in that a compressible housing surrounding the rotor is provided. 14. Fluid pump according to aspect 13, characterized in that the housing consists at least partially of a material containing cavities, in particular a foam. 15. A compressible rotor for a fluid pump having at least one blade, wherein the rotor is constructed such that it can assume a compressed and a decompressed state and the average density change of the rotor material between the compressed and decompressed states is at least 10%.

Claims

[1] Compressible rotor (2,15) for a fluid pump (1) with at least one blade (20,25,26) and with at least one deformable cavity (27,28,29) filled or fillable with a fluid. [2] Rotor (2,15) according to claim 1, characterized by that the cavity(ies) (27,28,29) is / are closed. [3] Rotor (2,15) according to claim 2, characterized by that the cavity(ies) (27,28,29) is / are at least partially delimited by a partially permeable membrane. [4] Rotor (2,15) according to claim 3, characterized by that the at least one cavity (28) is filled with a liquid which, in cooperation with the membrane and a liquid in which the fluid pump (1) can be used, in particular blood, causes an osmotic diffusion into the cavity (28) with a corresponding increase in pressure. [5] Rotor (2,15) according to claim 1, characterized bythat at least some of the cavities (27,28,29) are surrounded by solid material of the rotor (2,15) and are connected to an outer area and / or to one another via openings. [6] Rotor (2,15) according to claim 1 or one of the following, characterized by that the rotor (2,15) consists at least partially of a porous material (32), in particular foam. [7] Rotor (2,15) according to claim 1 or one of the following, characterized by at least one cavity (27) which has a greater extent in a first direction (33) than in the directions substantially perpendicular thereto. [8] Rotor (2,15) according to claim 7, characterized by that the cavity(ies) (27) is / are round or polygonal in cross-section, in particular octagonal, hexagonal, triangular or square. [9] Rotor (2,15) according to claim 7 or 8, characterized by that the cavity(ies) (27) have a strand shape. [10] Rotor (2,15) according to claim 8 or 9, characterized by that the cavity(ies) (27) are aligned with the direction of their greatest stability, in particular their longitudinal axis (33), in the direction of the pressure forces occurring during operation within the rotor (2,15). [11] Rotor (2,15) according to claim 1 or one of the following, characterized by that the cavity(ies) (27,28,29) is / are provided in at least one blade (20,25,26). [12] Rotor (2,15) according to claim 1 or one of the following, characterized by that the blade (26) is self-supporting and hubless. [13] Rotor (2,15) according to one of claims 1 to 11, characterized by that the cavity(ies) (27,28,29) are provided in a hub body. [14] Fluid pump (1) with a rotor (2,15) according to one of claims 1 to 13, characterized by that a compressible housing (3) surrounding the rotor (2,15) is provided. [15] Fluid pump (1) according to claim 14, characterized by that the housing (3) consists at least partially of a material containing cavities (27, 28, 29), in particular a foam. [16] Compressible rotor (2,15) for a fluid pump (1) with at least one blade (20,26), wherein the rotor (2,15) is constructed such that it can assume a compressed and a decompressed state and an average density change of the rotor material between the compressed and decompressed state is at least 10%.

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