Membrane catheter

A substance exchange device for intracorporal use includes a cavity for receiving blood having at least one blood inlet and at least one blood outlet, a substance exchange membrane adjoining the cavity, a supply duct for supplying an exchange fluid to the substance exchange membrane, a blood pump arranged within the cavity and a drive unit for the blood pump. The blood pump is configured to pump blood in a direction from a blood inlet to a blood outlet of the cavity. The drive unit includes a turbine, which is connected to the supply duct and may be driven by an exchange fluid supplied via the supply duct, where the turbine includes at least a rotor coupled to the blood pump and a stator (turbine nozzle) arranged upstream of the rotor.

BACKGROUND OF THE INVENTION

The invention relates to a substance exchange device for intracorporeal use, comprising a cavity for receiving blood having at least one blood inlet and at least one blood outlet, a substance exchange membrane adjoining the cavity, a supply duct for supplying an exchange fluid to the substance exchange membrane, a blood pump arranged within the cavity and a drive unit for the blood pump, wherein the blood pump is configured to pump blood in a direction from the blood inlet to the blood outlet of the cavity.

In this context, a substance exchange device is any device for exchanging substances from blood or into blood. The substance exchange membrane may have a first side and a second side opposite the first side, wherein the first side may adjoin the cavity and wherein the supply duct may be configured to supply the exchange fluid to the second side of the substance exchange membrane. An exchange substance contained in or corresponding to the exchange fluid may pass over the membrane into the blood on the other side or, the other way round, an exchange substance may pass from the blood into the exchange fluid. During operation the blood pump may be used to create a local pressure difference between the blood inlet and the blood outlet to enable the required blood flow via the membrane. Otherwise, there would hardly be any blood flow via the membrane due to its flow resistance. By virtue of the blood pump, the pressure loss caused by the substance exchange device is compensated at least in part. In particular, the blood pump may enable the blood flow via the membrane and increase it along the substance exchange device, and optionally the blood flow may be supported by a bypass arranged upstream of the membrane.

The blood pump may be any conveying device which is configured to at least partially compensate for a pressure difference between the blood inlet and the blood outlet during operation. The conveying device may comprise a drive unit for generating a torque and a pump rotor connected with the drive unit for the transmission of a torque. For example, the drive unit may comprise an electric motor. That achieves a simple control of the conveying device, in particular of the rotational speed of the rotor.

Substance exchange devices, such as intravascular membrane oxygenators, are known from patent documents in different embodiment variations. For example, WO 2004/016300 A2 discloses an intravenous oxygenator configured as a catheter for oxygenating the blood, having a membrane in the form of a fibre bundle, with each of the fibres connected to a gas supply via a first port and to a gas exhaust via a second port. The fibre bundle is torsion-bent by a relative twisting of the first port of the fibres with respect to the second port of the fibres around the longitudinal axis of the oxygenator during operation. As a consequence, the fibres extend along the entire length of the fibre bundle as continuous gas conduits. During operation of the oxygenator, oxygen is supplied, flowing into the fibres via the first port and causing a diffuse gas exchange with blood on the surface of the fibres. During this, the blood is enriched with oxygen while CO2is being removed at the same time. Consequently, a gas mixture of oxygen and carbon dioxide is present in the fibres at the second port, which mixture flows through an exhaust chamber in a tube and out of the patient's body through the tube. The blood flowing into the oxygenator passes through the torsion-bent fibre bundle and reaches a pump. Here, the blood is conveyed in the flow direction of the vein and leaves the oxygenator through an outlet. Thus, the pressure drop of the blood is compensated for by the pump, so the pressure at the outlet equals the physiological pressure again.

Only marginally, US 2010/258116 A1 mentions the use of a rotor, but without any indication of its use as a blood pump. The impeller is not presented in more detail and no executable technical solution on how to possibly arrange and drive such a rotor is given, so the function of the impeller remains unclear.

The pump shown in US 2013/053623 A1 serves to support the cardiac function and thus relates to an entirely different field of application than the present device. Naturally, the pump shown does not comprise a membrane as defined by the device according to the invention, i.e., for the exchange of substances.

In the device shown in GB 2505068 A, a blood pump is driven by a drive shaft of a drive unit located outside the body. This means that in this case the drive unit is not a part of the substance exchange device for intracorporeal use.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to avoid a separate power supply of the drive unit.

This object is achieved according to the invention by a substance exchange device of the initially presented type in such a way that the drive unit comprises a turbine, which is connected to the supply duct and may be driven by an exchange fluid supplied via the supply duct, wherein the turbine comprises at least a rotor coupled to the blood pump and a stator (turbine nozzle)

Preferably, the stator of the turbine is arranged upstream of the rotor of the turbine. This means that the stator (turbine nozzle) is arranged upstream of the rotor with respect to the flow direction of the exchange fluid during operation. The turbine element may form part of a general drive unit. The exchange fluid or carrier medium may flow around the turbine element during operation. The stator (turbine nozzle) arranged upstream of the rotor provides for a correct approaching flow to the turbine's rotor by the exchange fluid flowing (such as an exchange substance or a carrier medium) through the stator (turbine nozzle).

A part of the internal energy of the flowing exchange fluid is converted to mechanical power by the turbine and delivered to the blood pump by a shaft. The exchange fluid may be liquid or gaseous. It may be supplied to the substance exchange device from outside of the body by means of a catheter and be conveyed through the substance exchange device by an extracorporeal pump. The exchange fluid may be a liquid or gaseous exchange substance, or a liquid or gaseous carrier medium or conveying medium in which the exchange substance is present in solution and/or with which the exchange substance is mixed and/or by which the exchange substance is taken in from the blood.

An object of the drive unit is the conversion of energy supplied by the fluid to a torque within the substance exchange device, which torque is transmitted to a shaft. In this way, the power supply of the drive unit is obtained together with the supply of the exchange fluid and not separately and/or independently thereof. In particular, no electrical connection of the drive unit from outside of the body is required. This means that both the blood pump and the turbine are integrated into the substance exchange device. The axis of the shaft is arranged substantially parallel to a longitudinal extension axis of the substance exchange device. The shaft transmits the torque created in the drive unit to a pump rotor of the blood pump, which pump rotor is connected to the drive unit. Eventually, the pump rotor transmits the torque to the blood. In such a conveying device, comprising a turbine as the drive unit and a blood pump as the working machine, a part of the flow energy of the exchange fluid is transmitted to the conveyed blood.

In addition to the supply duct the substance exchange device may comprise a return duct for returning the exchange fluid from the substance exchange membrane. The present invention is not limited to one of each of a supply duct and a return duct. In particular, two supply ducts and/or two return ducts may be provided, for example with different supply ducts and/or different return ducts being connected to the membrane and the turbine, respectively. This makes it possible to obtain an independent control of the substance exchange membrane and the turbine. In particular, in this case the systems turbine and substance exchange membrane may be controlled independently of each other even when possible controlled valves are not located within the body but arranged within an external control unit.

Connected to an extracorporeal conveying and exchange assembly for reprocessing and conveying of the exchange fluid, the substance exchange device may be dimensioned as a complete system using components already present in the market such that it is portable and the extracorporeal circuit with or at the console may even be carried in a bag.

A torque is preferably transmitted from the drive unit to the pump rotor along a shaft the axis of which is arranged substantially in parallel to a longitudinal axis of extension of the substance exchange device (e.g. a catheter). In the simplest and most reliable case, the turbine element is coupled directly to the pump rotor, so both elements operate at the same speed during use. Even in case of an indirect coupling, for example via a magnetic coupling (see below), the blood pump and the turbine may be operated at the same speed, for example by using the same number of magnet pole pairs in the coupling. By adapting the blood pump and the turbine to a desired operating point (speed, pressure conditions, volumetric flows), an optimised operation of the substance exchange device may be obtained in both cases.

It is favourable for a pump rotor of the blood pump to be supported in a sliding contact bearing. In this case, the blood itself is used as the lubricant. This advantage may be obtained independently of the arrangement of the rotor and the stator of the turbine.

Furthermore, a pump rotor and other parts of the blood pump may be made of technical ceramics such as alumina, a metal such as titanium or a plastic material such as PEEK (poly-ether ether ketone) and, preferably, be provided with a surface coating as well. These materials are particularly suited for use in the blood circuit.

Moreover, it is advantageous to integrate at least one speed sensor in the substance exchange device, which speed sensor is configured to sense the speed of the turbine, the blood pump or a coupling between the blood pump and the turbine. In this context, integrated means that the speed sensor is a part of the substance exchange device and is thus located intracorporeally during operation of the substance exchange device. Multiple speed sensors may be provided for sensing the speed at several of the mentioned locations. The sensed speed may then be converted to an electronic signal and be used to monitor and check the proper operation of the substance exchange device. In particular, a Hall sensor may be provided as the speed sensor.

In an embodiment of the present invention the blood pump may be coupled to the turbine via a gearing, which gearing is configured to reduce the speed of the blood pump with respect to the speed of the turbine. Such a reduction is particularly advantageous when using a gaseous exchange fluid, so the turbine can be operated at a correspondingly higher speed than required for the blood pump. In general, an operating point of the turbine suited for the respective exchange fluid at a specified speed of the blood pump may be obtained with the aid of the gearing.

Furthermore, it has proven favourable for the present substance exchange device to comprise one or more return duct(s) for returning an exchange fluid from the substance exchange membrane and/or the turbine, wherein the return duct is configured to withstand a negative pressure (i.e., a negative differential pressure with respect to an ambient pressure of approx. 1 bar). In this case, the overpressure of the supply duct may be reduced or avoided in its entirety, so the risk of exchange fluid escaping into the blood in case of leakage may be reduced. By applying a vacuum instead of the exchange fluid, a concentration gradient at the substance exchange membrane may be obtained as well.

In conjunction with the drive unit it is favourable for the pump rotor to be connected to the drive unit via a magnetic coupling, wherein the magnetic coupling comprises two coupling parts for torque transmission along an axis of rotation, said coupling parts being rotatable relative to each other and each having a permanent magnet. For example, a concentric ring coupling or a disc coupling may be used as the magnetic coupling. Compared to a continuous mechanical connection, for example in the form of a continuous shaft, a magnetic coupling has the advantage that the transmitted torque is limited and a hermetic separation between blood-carrying and non-blood-carrying parts may be established. While the pump rotor also stops in case of the turbine getting stuck, the limitation is technically reasonable nevertheless since failure can be detected. Should the turbine rev up due to a fault, the magnetic coupling would cease transmitting the power at some point in time. This protects the blood circuit from overloading.

In order to be able to transmit a desired torque with a particularly compact magnetic coupling as well, it has been proven advantageous for one of the coupling parts to comprise an at least partially ferromagnetic guiding element which is non-rotatably connected to the permanent magnet of the coupling part, wherein one part of the guiding element is disposed radially outside of the permanent magnet of the other coupling part. Such a magnetic coupling is shown in WO 2015/172173 A2, for example, the content of which is incorporated in this application herewith. This means that the magnetic coupling comprises two coupling parts which can be rotated relative to each other, wherein a drive-side coupling part comprises a drive-side permanent magnet and an output-side coupling part comprises an output-side permanent magnet that lies opposite and at a distance from the drive-side permanent magnet along the axis of rotation, wherein one of the coupling parts comprises an at least partially ferromagnetic guiding element which is non-rotatably connected to the permanent magnet of the coupling part, wherein one part of the guiding element is disposed radially outside of the opposite permanent magnet. With respect to traditional concentric ring couplings, this design has the advantage that it may be produced in a simpler and more economical way and requires a smaller total coupling area since a part of the torque is transmitted via the front side of the coupling parts. With respect to traditional disc couplings, it has the advantage that smaller radial dimensions are required for transmitting a certain torque. Comparable to the outer coupling part of a concentric ring coupling, the guiding element may be shaped as a cup or a hollow cylinder and may surround the respective other coupling part circumferentially, i.e., preferably it extends radially outside of both permanent magnets. The guiding element may be formed as a thin-walled hollow cylinder, for example, so that with unchanged dimensions the magnetised volume of the disc coupling is retained to the greatest possible extent and, at the same time, a transmittable torque comparable to that of a concentric ring coupling may be obtained between the guiding element and the opposite permanent magnet at a distance therefrom. The direction of magnetisation of the permanent magnets is preferably oriented perpendicular to the axis of rotation, i.e., the poles of the magnets extend circumferentially from south to north and are—at least in a two-pole design—diametrically opposite each other with respect to the axis of rotation. By means of the guiding element, magnetic field lines extending radially from the permanent magnets are bundled, and due to the ferromagnetic material of the guiding element the magnetic force between the coupling parts is further increased. The magnetic force for transmitting the torque is raised by compressing the magnetic field lines in the ferromagnetic material. Advantageously, due to the larger volumes of the permanent magnets when compared to concentric ring couplings with equal dimensions of the couplings, a shorter axial extension and thus lower radial transverse forces on the bearings of the coupling parts can be achieved.

The permanent magnets of the magnetic coupling may each be 2-, 4- or 6-pole permanent magnets. Preferably they are two-pole permanent magnets with each having two half-cylindrical magnetic poles. The at least partially ferromagnetic guiding element may comprise at least one diamagnetic or paramagnetic separation. This separation parts the guiding element into at least two ferromagnetic sections and thus avoids magnetic short circuits. A diamagnetic separation or a para-magnetic separation (made of aluminum or brass, for example) may be used. Paramagnetic refers to materials having a magnetic permeability of just slightly above 1, in particular having a magnetic permeability below 1.2, preferably having a magnetic permeability below 1.05.

In addition to the radially outside arrangement the guiding element may also extend at a rear side of the non-rotatably connected permanent magnet, which rear side is facing away from the opposite permanent magnet. Alternatively or in addition, the guiding element may have a substantially H-shaped longitudinal section with a cross web disposed perpendicular to the axis of rotation and cup-shaped recesses formed on both sides, wherein a permanent magnet is received and non-rotatably connected in one of these recesses. This means that the guiding element may comprise a hollow cylindrical jacket and preferably be configured with an intermediate base arranged substantially at half height of the jacket.

A particularly high concentration of magnetic field lines within the guiding element of the magnetic coupling may be achieved if a diamagnetic or paramagnetic shielding element is arranged at a rear side of the permanent magnet non-rotatably connected to the guiding element, which rear side is facing away from the opposite permanent magnet. In this way, field lines running outside of the coupling parts, in particular outside of the guiding element, may be avoided and thus losses related thereto may be reduced. This means that the “shielding” obtained by the shielding element preferably consists in the magnetic field lines preferably passing through the guiding element rather than through the shielding element.

Furthermore, it has proven favourable in the magnet coupling if a diamagnetic or paramagnetic shielding element is arranged at a front side of the permanent magnet non-rotatably connected to the guiding element, which front side is facing the opposite permanent magnet, in particular in a region centred around the axis of rotation, which shielding element adjoins the guiding element preferably circumferentially or radially on the outside. Such a shielding makes it possible to guide the magnetic field to regions located at larger radial distances from the axis of rotation so the torque transmitted at a given magnetic force is increased.

For preventing a passing over of the carrier medium into the blood in a reliable manner, it is also favourable for the two coupling parts to be hermetically separated. Such a hermetic separation may be obtained, for example, by a hermetic separating wall arranged between the two coupling parts, which wall separates the drive unit and the blood pump hermetically from one another. The hermetic separating wall should be non-conductive both magnetically and electrically. In particular, at least one of the coupling parts may be accommodated in a substantially non-magnetic and electrically non-conductive housing in order to be able to avoid losses due to a reversal of magnetism of the housing and/or induced eddy currents in the housing.

Preferably, the guiding element may be connected non-rotatably to the drive-side coupling part, wherein at least one flushing duct is provided within a hermetic separating wall between the two coupling parts, which flushing duct connects, during operation, a gap between the front side of the pump-side coupling part and the hermetic separating wall to at least one blood flow outside of the hermetic separating wall, wherein said blood flow may either be a blood flow through the blood inlet or a blood flow upstream of the blood inlet. In this way, the flushing duct connects a blood- and a pump-side part of the coupling to a blood flow outside of the coupling. Inflow to the blood- and the pump-side part of the coupling is accomplished via a sliding contact bearing near the coupling in front of the blood-side magnet or via a bore in the shaft of the pump. This means that a connection to a blood flow outside the coupling is established between the front side of the pump-side coupling part and through the hermetic separating wall while the function of the hermetic separation between blood-carrying and non-blood-carrying parts remains intact. By means of such flushing ducts, dead spaces at an output side (“blood side”) within the magnetic coupling may be reduced or avoided in their entirety.

In particular, it has been shown that an integrated support, preferably a rolling contact bearing between a drive-side coupling part and the hermetic separating wall, and a sliding contact bearing support between the hermetic separating wall and the output-side coupling part, are provided. This means that the drive-side coupling part is supported rotatably in a rolling contact bearing opposite the hermetic separating wall and the output-side coupling part is supported rotatably in a sliding contact bearing opposite the hermetic separating wall. Such a support provides for a more stable operation and an increased running smoothness in the region of the coupling when compared to coupling parts without support at the front side, since these are subject, among other things, to the risk of the magnetic cup starting to swing and the torque transmission being interrupted.

The conveying of substance via the membrane is determined by three transport resistances: the blood-side substance transition resistance which is also referred to as concentration polarisation, the substance transport resistance by the membrane and the substance transport resistance into the receiving phase (carrier substance) at the permeate side of the membrane. Due to the substantially laminar flow conditions, the boundary layer thickness and thus the substance transition resistance increase with the length of the flow over the membrane. Due to the material properties of the blood—rheology, low coefficient of diffusion and buffer effect—it is most important to reduce the substance transition resistance at the blood side. This is obtained by: a) increasing the speed of the overflow and thus reducing the boundary layer thickness, b) improving the flow distribution and equalisation of the residence time, c) geometric measures by controlled flow guidance, by the installation of statical turbulence promoters, by the geometrically caused induction of secondary flow phenomena and by targeted interruption of the boundary layer build-up, d) more controlled distributing, merging, mixing and redistributing of the blood onto the membrane. The present invention solves this problem by combining measures a) to d).

For this reason it is particularly advantageous to arrange a diverting member between the blood pump and the at least one blood outlet in the cavity, wherein the diverting member is configured to partially divert in the radial direction a blood flow flowing axially through the cavity and/or the diverting member is configured to induce turbulences in this very blood flow. For example, the diverting member may act as a statical turbulence promoter. The partial diverting of the blood in the direction of a radial flow component and/or the inducing of turbulences in the flow make it possible to improve the exchange with the exchange fluid at the substance exchange membrane.

For example, the diverting member may comprise helical, conical (and/or frustum-conical), arrow-shaped and/or disc-shaped guiding surfaces, which are concentric with respect to a longitudinal axis between the blood pump and the blood outlet.

The diverting member may be supported rotatably within the cavity. It may be freely rotatable or preferably coupled to the pump rotor of the blood pump for a forced rotation of the diverting member.

Preferably, the cavity may comprise at least two blood outlets at different distances from the at least one blood inlet. In particular, a first blood outlet may be provided immediately downstream of the blood pump and a second blood outlet may be provided downstream of the substance exchange membrane. The first blood outlet forms a bypass for the substance exchange membrane. During operation, blood may flow through the first blood outlet, from the cavity and from the substance exchange device to the outside into the surroundings of the substance exchange device, for example a surrounding vessel. Due to the drive by the blood pump, this blood has a higher internal energy than the blood passing by the substance exchange device, so the delivery results in a comparably higher local pressure in the vessel. Such an arrangement of multiple blood outlets may also be provided independently of the use of a turbine as the drive unit and thus independently of the arrangement of the rotor and the stator of a turbine as well. Instead of a turbine, the substance exchange device could, for example, comprise an electric motor as the drive unit for the blood pump.

The invention also relates to a substance exchange device for intracorporeal use in general, comprising a cavity for receiving blood having at least one blood inlet and at least one blood outlet, a substance exchange membrane adjoining the cavity, a supply duct for supplying an exchange fluid to the substance exchange membrane, a blood pump arranged within the cavity and a drive unit for the blood pump, wherein the blood pump is configured to pump blood in a direction from the blood inlet to the blood outlet of the cavity, wherein the drive unit comprises a turbine, which is connected to the supply duct and may be driven by an exchange fluid supplied via the supply duct.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a substance exchange device1during operation in an intracorporeal arrangement. In this arrangement, the substance exchange device1is used as an intravascular catheter in a blood vessel2. The substance exchange device1comprises a cavity3, a substance exchange membrane4, a supply duct5, a blood pump6and a drive unit7. During operation, blood is contained within the cavity3. The cavity3comprises two blood inlets8,9and two blood outlets10,11. The two blood outlets10,11are arranged at different distances from the two blood inlets8,9. The first blood outlet10is arranged immediately downstream of the blood pump6and forms a bypass for the substance exchange membrane4. The second blood outlet11is arranged downstream of the substance exchange membrane4and forms the proximal end of the substance exchange device1. The substance exchange membrane4adjoins the cavity3. It may be a hollow-fibre membrane having fibres arranged cylindrically around the cavity3. The substance exchange membrane4keeps a substantially consistent position within the surrounding vessel2and is not rotated with respect thereto.

The supply duct5is configured to supply an exchange fluid to the substance exchange membrane4. For example, the exchange fluid may be a low-CO2gas mixture. The supply duct5may connect the inlet12of a hollow-fibre membrane to a supply tube13, which connects the substance exchange device1to an extracorporeal transfer device for reconditioning the exchange fluid. Furthermore, the substance exchange device1comprises a return duct14for returning an exchange fluid from the substance exchange membrane4. The return duct14as well as a return tube15connected thereto are configured to withstand a negative pressure. The supply tube13and the return tube15may be formed as a single multilumen tube, for example a double-walled tube.

The blood pump6is arranged within the cavity3. It is configured to pump blood in a direction from the blood inlets8,9to the blood outlets10,11. Preferably, the blood pump6is a rotary pump of radial, diagonal or axial design. A pump rotor16of the blood pump6is supported in at least one sliding contact bearing17. A diffuser18may be arranged downstream of the pump rotor16to reduce or entirely remove the rotatory portion of the conveyed medium and convert it to a pressure increase. If this diffuser18is not used (for compensating the rotation), however, the flow may also be guided to the substance exchange membrane4with a rotation, so the flow does not (only) approach the membrane in the longitudinal direction. The blood pump6is arranged for conveying the blood flow in such a way that a sufficient amount of blood flows through the substance exchange membrane4. In case of intravascular use, the substance exchange device1embodies an additional resistance in the vessel2, which is at least partially compensated by the motion power imparted to the blood by the blood pump6. At the same time, the pressure loss through the substance exchange device1in the vessel2may be compensated partially or entirely, or a pressure increase within the vessel2may be obtained, depending on the mode of operation. In particular, this may be accomplished by means of the first blood outlet10, which makes it possible that volumes of blood flowing through the blood pump6do not necessarily have to flow through the substance exchange membrane4as well.

The drive unit7is used for driving the blood pump6. With its aid, the blood pump may be rotated and thus define the inflow of the blood into the substance exchange membrane4with respect to flow direction and volumetric flow. The drive unit7comprises a turbine19. The turbine19is connected to the supply duct5, in particular arranged within the supply duct5, and may be driven by means of an exchange fluid supplied via the supply duct5. The turbine19comprises a rotor21, coupled to the blood pump6via a rotatably supported shaft20, and a stator (turbine nozzle)22arranged upstream of the rotor21. The blood pump6is coupled to the turbine19via a gearing23. The gearing23is configured to reduce the speed of the blood pump6with respect to the speed of the turbine19. It may be a planetary gearing, for example. The drive unit7and the blood pump6together form a conveying device for conveying blood through the cavity3of the substance exchange device1. During operation, the pump rotor16of the blood pump6is driven by the turbine19in such a way that an acceleration of the blood flow in the region of the blood inlets8,9and thus an overpressure at the distal end of the cavity3is created. Here, the speed of the turbine19may be controlled by the substance flow and/or the volumetric flow of the exchange fluid such that the differential pressure obtained at the pump just compensates all occurring pressure losses from the blood inlets (8,9) to the proximal blood outlet (11). This results in an effective compensation of the flow resistance inside the substance exchange device1caused by the substance exchange membrane4.

Two speed sensors24,25are integrated into the substance exchange device1. The first speed sensor24is configured to sense the speed of the turbine19, the second speed sensor25is configured to sense the speed of the blood pump6. Both speed sensors24,25are Hall sensors. The speed sensors24,25are integrated into a housing71of the substance exchange device1, which surrounds the drive unit7and the blood pump6. As a signal transmitter for the speed sensors24,25, a magnet72is arranged in each of the rotor21of the turbine19and the pump rotor16of the blood pump6, preferably centrically (the eccentric illustration is schematically and for easier visibility only; in practice, unbalance is to be avoided).

A pump rotor16of the blood pump6is coupled to the turbine19via a magnetic coupling26(cf.FIG. 7). For torque transmission along an axis of rotation27, the magnet coupling26comprises two coupling parts28,29which can be rotated relative to each other, each comprising a two-pole permanent magnet. One of the coupling parts28comprises an at least partially ferromagnetic, cup-shaped guiding element30. The guiding element30is non-rotatably connected to the permanent magnet of the drive-side coupling part28. A part of the guiding element30is located radially outside of the permanent magnet of the other coupling part29. The jacket of the guiding element30is only interrupted by a diamagnetic or para-magnetic separation (not illustrated) in a narrow angular region. The diamagnetic separation parts the guiding element30substantially into two ferromagnetic halves or half-shells. An intersecting plane running through the diamagnetic or paramagnetic separation is thus perpendicular to a direction of magnetisation of the drive-side two-pole permanent magnet that is connected to the guiding element30. Consequently, the ferromagnetic sections of the guiding element30defined by the diamagnetic or paramagnetic separation are magnetised in accordance with the drive-side permanent magnet.

Due to the contact-free coupling, a hermetic separating wall31is provided between the drive-side coupling part28and the output-side coupling part29. At least one flushing duct32is provided within the hermetic separating wall31. The flushing ducts32connect a gap33between the front side34of the pump-side coupling part29and the hermetic separating wall31to a region adjoining the blood inlets8,9. An additional flushing duct73is provided within the pump-side shaft section38for lubricating a fixed sliding contact bearing cup74, in which the shaft section38is supported. As can be seen in detail inFIG. 7, the rotatable components of the substance exchange device at the output side (also pump side or “blood side”) are supported in sliding contact bearings17, and the rotatable components of the substance exchange device at the drive side (also turbine side) are supported in rolling contact bearings35(cf. alsoFIG. 1).

During operation, a torque is applied to the rotor21via the blades of the turbine19by the flow of the supplied exchange fluid. The turbine19transmits the torque via the shaft36, which is rotatably supported in rolling contact bearings35, to the drive side of the gearing23. At the output side of the gearing23, a correspondingly higher torque with lower speed is transmitted to the drive-side coupling part28of the magnetic coupling26via a further shaft section37. If the drive fluid is a liquid medium, the gearing23may be omitted, provided that the turbine and the pump have the same speed at their individual adapted operating points and the torque delivered by the turbine corresponds to the required input torque of the pump. Due to the magnetic forces between the coupling parts28,29, the torque is transmitted from the drive-side coupling part28to the output-side coupling part29, wherein the strength of the magnetic forces defines a certain transmittable maximum torque beyond which the coupling parts28,29will “slip” with respect to one another. The output-side coupling part29transmits a torque exerted by the drive-side coupling part28via a third shaft section38, which is supported in sliding contact bearings17, to the pump rotor16of the blood pump6. The pump rotor16conveys the blood40, which approaches through an (optional) flow straightener39, from the blood inlets8,9through the cavity3towards the substance exchange membrane4of the substance exchange device1. In this way, the conveying device creates a pressure difference between the blood inlets8,9and the proximal end of the cavity3, which pressure difference preferably compensates, substantially entirely, a pressure loss between the proximal and the distal end of the substance exchange device1due to the flow resistance of the substance exchange membrane4, so the blood41flowing in the vessel2after the substance exchange device1has at least the same internal energy as the blood40before. The concentration of a substance may have experienced a reduction (e. g. CO2reduction) or an increase (e.g. O2enrichment) at the location in the blood40to the location in the blood41.

Instead of a hollow-fibre membrane a different type of membrane may also be used as the substance exchange membrane4in the substance exchange device1, wherein those skilled in the art will adjust the conveying device including the drive unit7and the blood pump6to the expected pressure difference due to the different flow resistances of other types of membrane.

In the section of an exemplary embodiment shown inFIG. 2, a diverting member44is arranged inside a substance exchange membrane43between the blood pump (on the right-hand side, not illustrated here) and a blood outlet42in the cavity3. The diverting member44is configured to partially divert in the radial direction a blood flow flowing axially through the cavity3. The diverting member44schematically illustrated inFIG. 2comprises helical guiding surfaces46concentric to a longitudinal axis45between the blood pump and the blood outlet42. The diverting member44may be fixed rigidly within the cavity3of the substance exchange device1or supported rotatably within the cavity3. By means of the helical guiding surfaces46, the blood47approaching from the pump during operation is forced along the longitudinal axis45in the centre, constantly radially through the helix over its length and transversely to the substance exchange membrane43due to the helical shape. In the substance exchange membrane43, a mass exchange with an exchange fluid takes place, which exchange fluid is supplied to the substance exchange membrane43and/or returned from the substance exchange membrane43by supply and return ducts48.

InFIGS. 3 and 4, a further variation of a diverting member49is illustrated schematically. The substance exchange membrane43as well as the supply and return ducts48are the same as those inFIG. 2. The diverting member49according toFIGS. 3 and 4comprises frustum-conical guiding surfaces50concentric to a longitudinal axis45between the blood pump (not illustrated; right-hand side inFIG. 4) and the blood outlet42. The blood47approaching from the pump during operation flows along the outside of the guiding surfaces50through the clearances or holes51of the diverting member49left open therebetween and through the substance exchange membrane43. The diverting member49is supported freely rotatable between two sliding contact bearings52,53. The sliding contact bearing53arranged downstream comprises flushing ducts for ensuring lubrication in the region of the bearings. Furthermore, the diverting member49comprises a turbine element54of its own, which is driven by the blood47approaching from the blood pump and thus rotates the diverting member49. The centrifugal force caused by the rotation effects an additional acceleration of the blood flow in the radial direction through the substance exchange membrane43arranged radially outside. A part of the blood flows in the centre of the diverting member49, which is continuously hollow on its inside, along the longitudinal axis45.

FIG. 5shows, highly simplified, a diverting member55with similar operation having arrow-shaped guiding surfaces, andFIG. 6shows, highly simplified as well, a diverting member56having disc-shaped guiding surfaces. The diverting members44,49,55,57may each be freely rotatable or optionally be non-rotatably coupled to the pump rotor16of the blood pump6to co-rotate at the same speed in order to obtain, via a centrifugal force caused by the rotation, an acceleration of the blood flow in the radial direction through a substance exchange membrane43arranged radially outside. As an alternative to the coupling to the pump rotor16, a turbine element54(cf.FIG. 4) may be integrated into the respective diverting members.

In the use shown inFIG. 8, a substance exchange device59according to the invention (only indicated schematically) having a substance exchange membrane60and a conveying device61is arranged within a tube62foreign to the body, which interconnects two blood vessels63,64. A part of the blood flow or the entire blood flow is taken from the first blood vessel63through a first tube section65and supplied, via a blood inlet66of the substance exchange device59, to the conveying device61having a turbine, a magnetic coupling and a blood pump and the substance exchange membrane60of the substance exchange device59. From the blood outlet67of the substance exchange device59, the blood is supplied to the second blood vessel64through a second tube section68. The second blood vessel64may be identical to the first blood vessel63. The flow direction of the blood is indicated by arrows69. An exchange fluid is supplied to the substance exchange device59and returned from the substance exchange device59through a multi-lumen tube70. In this use, a gearing between the turbine and the blood pump may be omitted since when using a gas as the drive fluid for the turbine, the turbine may be configured correspondingly larger due to the spatial conditions. Provided that the turbine and the pump have the same speed at their individual adapted operating points and the torque delivered by the turbine corresponds to the required input torque of the pump.

The conveying device represented inFIG. 9comprises a pump rotor75and a drive unit76in the form of an electric motor77. During operation, the electric motor77transmits a torque via a shaft78to the pump rotor75. The shaft78is supported by means of an end79lying opposite the electric motor77in a stator80. The stator80is fastened in the catheter81in a connecting area82via wings83. Here, the wings83are arranged substantially in parallel or slightly angled to a flow direction (indicated by the direction arrows84) of the blood entering through the lateral blood inlets (not shown) into the catheter81. The pump rotor75itself also has blades85which are arranged propeller-like for the axial transport of the blood located between the blades85during a rotation of the pump rotor75.

During operation, the pump rotor75is driven by the electric motor77—which forms a drive unit—in such a way that an acceleration of the blood flow in the area of the blood inlets and, thus, an excess pressure at the distal end86of the catheter81are generated. In this connection, the rotational speed of the electric motor77is controlled via a control (not shown) such that the obtained excess pressure just compensates for a pressure difference between the blood inlets and the blood outlet11(seeFIG. 1). Thereby the flow resistance caused by the hollow fibres87,88inside the catheter81is effectively compensated for.

FIG. 10shows a further, preferred embodiment for a conveying device89. The conveying device89forms the distal end90of the catheter81. The conveying device89comprises a pump rotor91which is rotatably arranged between a magnetic coupling92and a pump stator93and is rotatably supported with a shaft94in the pump stator93. The pump stator93is fastened via lateral wings95in a first connecting ring96. The first connecting ring96comprises an embedding mass97in which the hollow fibres87,88of the hollow fibre membrane98are embedded and with which they are connected, wherein the hollow fibres87,88extend through the first connecting ring96axially, i.e. in parallel to a longitudinal axis of the catheter81. The first connecting ring96is connected at a radial outer side to the catheter tube99of the catheter81.

The conveying device89further comprises as a drive unit100a turbine element101which is supported in a turbine stator102such that it is rotatable around a shaft103. The shaft103forms a non-rotatable connection of the turbine element101with the magnetic coupling92, in particular with a drive-side coupling part104. The turbine stator102is arranged between the drive-side coupling part104and the turbine element101which acts as a turbine rotor, wherein the shaft103extends through the turbine stator102. The turbine stator102has lateral wings105by means of which it is fastened in a section106of the inner tube107of a feeding tube108, said section106being widened in the connecting area109. Correspondingly, the turbine element101is also arranged in the widened section106, and, thus, it is subjected to the flow of a carrier liquid110supplied through a supply channel111of the feeding tube108. As is indicated by the direction arrows112, the flow of the carrier liquid110leads out of the supply channel111into the widened section106via propeller-like blades113arranged at the turbine element101for the reception of a torque and past the wings105of the turbine stator102to the inlet114of the hollow fibre membrane98.

The ring-shaped inlet114and outlet115of the hollow fibre membrane98is formed at a second connecting ring116which comprises an embedding mass117in which the ends118of the hollow fibres87,88are embedded so that they lead into the inlet114or into the outlet115. Between the second connecting ring116and the first connecting ring96which is arranged proximal of the second connecting ring116, the catheter81has lateral blood inlets119.

Apart from the drive-side coupling part104, the magnetic coupling92also comprises a corresponding output-side coupling part120which is non-rotatably connected to the pump rotor91. Due to the rotatable support via the separated shafts94,103in the stators93,102, the drive-side coupling part104is rotatably supported relative to the output-side coupling part120. The output-side coupling part120comprises an output-side two-pole permanent magnet121which is non-rotatably connected to the shaft94of the pump rotor91. The drive-side coupling part104comprises a drive-side two-pole permanent magnet122which is non-rotatably connected to the shaft103of the turbine element101. The output-side permanent magnet121is circumferentially surrounded by a substantially cup-shaped guiding element123having a hollow cylindrical jacket. In this connection, there is provided a clearance or gap between the output-side permanent magnet121and the guiding element123so that the output-side coupling part120is coupled to the drive-side coupling part104in a contact-free fashion. The guiding element123is mainly made of a ferromagnetic material. The jacket of the guiding element123is interrupted by a diamagnetic separation (not shown) only in a narrow angular region. Substantially, the separation parts the guiding element123into two ferromagnetic halves or half-shells. An intersecting plane running through the separation is thus perpendicular to a direction of magnetisation of the drive-side two-pole permanent magnet122that is connected to the guiding element123. Consequently, the ferromagnetic sections of the guiding element123defined by the separation are magnetised in accordance with the drive-side permanent magnet122.

Due to the contact-free coupling there is provided a hermetic separation (not shown) between the drive-side coupling part104and the output-side coupling part120. The hermetic separation is formed by a foil sealingly connected with the radial inner side of the second connecting ring116.

During operation, by the flow of the supplied carrier liquid a torque is applied via the blades113to the turbine element101. The turbine element101transmits the torque via the shaft103to the drive-side coupling part104of the magnetic coupling92. By the magnetic forces between the coupling parts104,120, the torque is transmitted from the drive-side coupling part104to the output-side coupling part120, wherein the power of the magnetic forces defines a certain maximum transmittable torque beyond which a “slipping” of the coupling parts104,120relative to each other occurs. The output-side coupling part120transmits a torque exerted by the drive-side coupling part104via the shaft94to the pump rotor91. By means of lateral propeller-like blades124, the pump rotor91transports the blood located between the blades124from the blood inlets119in the direction of the blood passage125inside the catheter81. In this way, the conveying device89generates a pressure difference between the blood inlets119and the proximal end of the blood passage125which preferably and substantially completely compensates for a pressure difference between the proximal and the distal end (not shown) of the catheter81which is due to the flow resistance of the hollow fibre membrane98. Here, the turbine element101and the pump rotor91are preferably tuned with each other.