WO2006053384A1 - Pompe à fluide - Google Patents
Pompe à fluide Download PDFInfo
- Publication number
- WO2006053384A1 WO2006053384A1 PCT/AU2005/001748 AU2005001748W WO2006053384A1 WO 2006053384 A1 WO2006053384 A1 WO 2006053384A1 AU 2005001748 W AU2005001748 W AU 2005001748W WO 2006053384 A1 WO2006053384 A1 WO 2006053384A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- impeller
- cavity
- fluid
- vanes
- fluid pump
- Prior art date
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D13/00—Pumping installations or systems
- F04D13/02—Units comprising pumps and their driving means
- F04D13/06—Units comprising pumps and their driving means the pump being electrically driven
- F04D13/0666—Units comprising pumps and their driving means the pump being electrically driven the motor being of the plane gap type
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/10—Location thereof with respect to the patient's body
- A61M60/122—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
- A61M60/165—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable in, on, or around the heart
- A61M60/178—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable in, on, or around the heart drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
- A61M60/183—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable in, on, or around the heart drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices drawing blood from both ventricles, e.g. bi-ventricular assist devices [BiVAD]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/10—Location thereof with respect to the patient's body
- A61M60/122—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
- A61M60/196—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body replacing the entire heart, e.g. total artificial hearts [TAH]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/20—Type thereof
- A61M60/205—Non-positive displacement blood pumps
- A61M60/216—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller
- A61M60/226—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller the blood flow through the rotating member having mainly radial components
- A61M60/232—Centrifugal pumps
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/40—Details relating to driving
- A61M60/403—Details relating to driving for non-positive displacement blood pumps
- A61M60/422—Details relating to driving for non-positive displacement blood pumps the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/50—Details relating to control
- A61M60/508—Electronic control means, e.g. for feedback regulation
- A61M60/515—Regulation using real-time patient data
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/81—Pump housings
- A61M60/812—Vanes or blades, e.g. static flow guides
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/81—Pump housings
- A61M60/816—Sensors arranged on or in the housing, e.g. ultrasound flow sensors
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/818—Bearings
- A61M60/82—Magnetic bearings
- A61M60/822—Magnetic bearings specially adapted for being actively controlled
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/33—Controlling, regulating or measuring
- A61M2205/3331—Pressure; Flow
- A61M2205/3334—Measuring or controlling the flow rate
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/10—Location thereof with respect to the patient's body
- A61M60/122—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
- A61M60/126—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable via, into, inside, in line, branching on, or around a blood vessel
- A61M60/148—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable via, into, inside, in line, branching on, or around a blood vessel in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
Definitions
- the present invention relates to a motor, and in particular a fluid pump using an impeller which is suitable for use as a heart assist or heart replacement device, such as a BiVAD (Bi-ventricular device).
- a biVAD Bi-ventricular device
- Self bearing motors create magnetic fields that act to suspend and rotate the rotor, thus allowing the capacity for bearing and motor functions from either the same set of coils, or two coil sets occupying the same circumferential location.
- a number of magnetic principles can achieve this goal, based on so called Reluctance and Lorentz theories.
- self bearing motors When applied to centrifugal pump technology, self bearing motors eliminate the need for a shaft or seal, as the rotor is completely encapsulated within the pump cavity.
- Hydrodynamics bearings require relatively small clearances to provide sufficient bearing force. High shear stress is found in such clearances and is a possible site of haemolysis should blood cells enter this region. Hydrodynamic bearings rely on a passive response to forces imposed on the impeller, that is bearing stiffness cannot be altered for a given condition. Should forces exceed the predetermined bearing stiffness, touchdown is imminent. Additionally, rotors suspended hydrodynamically generate bearing force stiffness in direct proportion to rotor rotational speed. Ventricular assist devices have the potential to collapse the ventricle wall and thus block the inlet canula to the pump when excessive flow is demanded by the circulation system.
- the rotational speed of the pump must be reduced for a period of time to allow the ventricular wall to detach, a situation not afforded to pumps suspended via hydrodynamic bearings, since a reduction in rotational speed results in reduced bearing stiffness and potential impeller touchdown.
- US Patent No. 5,326,344 entitled “Magnetically Suspended and Rotated Rotor” describes an impeller for a blood pump which is supported by permanent magnets located in the impeller and pump housing respectively and stabilised by an electromagnet on the housing.
- the configuration of the magnetic suspension system lends itself to low efficiency due to relatively large magnetic "Air Gaps". That is, the distance from rotor magnets to housing magnets is relatively large resulting in excess magnetic flux leakage and thus poor efficiency. Additionally, the magnetic suspension system is separated from the drive mechanism leading to increased size and electronics to provide both functions independently.
- International Publication No. WO 99/01663 describes an improved rotor for a blood pump which relies on positioning of an impeller to give dynamic balance which is achieved through a combination of hydrodynamic and buoyant forces.
- the rotor is driven electromagnetically by means of an electromagnetic drive system operating in conjunction with one or more arrays of permanent magnets.
- the permanent magnets may be enclosed within radial vanes on the surface of the rotor with the drive components being arranged in a brushless motor configuration. In this device rotational movement of the rotor may occur around an axis which varies relative to the pump housing.
- the arrangement was provided to attempt to eliminate the need for highly precise axis control and design fabrication. Part of the problem addressed is the need to avoid the introduction of large forces which otherwise are created when the axis of the rotor shifts away from its normally centrally disposed position in a magnetic levitation system.
- the rotor is fashioned around an internal bore for accommodating inlet fluid and it is provided with a series of external shrouds providing multiple annular flow channels. This arrangement provides a larger surface area to contact blood during normal pumping operation. Erythrocyte fragility becomes a very relevant concern in such a device as shear force and frictional force interaction between the moving components and the blood volume may tend to lysis of red blood cells.
- centrifugal heart pumps used for left ventricular assistance to date feature a conventional single sided impeller. That is, a rotating impeller with one set of vanes used to urge blood from one inlet to one outlet.
- this technique can result in stagnation zones beneath the impeller, as well as unbalanced hydraulic forces experienced by the impeller which must be countered by forces generated from the suspension technique, thus leading to increased bearing power requirements and an overall loss of efficiency.
- Placement of magnetic material within the rotor required for suspension and/or drive is limited due to the miniature rotor size.
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; ii) two fluid outlets; and, iii) a set of coils for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having two sets of vanes, each set of vanes being adapted to urge fluid from a respective inlet to a respective outlet, in use; and, c) a drive system for: i) rotating the impeller about the cavity axis; and, ii) controlling an axial position of the impeller in a direction parallel to the cavity axis to thereby control the relative flows from each inlet to each respective outlet.
- reducing the physical separation between a respective set of vanes and the housing increases the efficiency of the vanes thereby increasing the flow of fluid to the respective outlet.
- the impeller cooperates with the cavity to define first and second cavity portions, each cavity portion including a respective inlet, outlet, and the impeller and cavity being configured to substantially prevent fluid transfer between the cavity portions.
- the drive system includes: a) a set of coils for generating a magnetic field; b) magnetic material provided in the impeller and positioned in the magnetic field in use; and, c) a controller for controlling the magnetic field generated by the coils to thereby control: i) rotation of the impeller about the cavity axis; and, ii) the axial position of the impeller.
- the impeller typically includes a shroud coupled to the vanes, the magnetic material being provided in the shroud.
- the magnetic material includes at least one of: a) magnets; and, b) iron.
- the drive system includes at least two sensors positioned in the housing, the sensors being adapted to detect the position of the impeller within the cavity, the controller being coupled to the sensors and controlling the axial position of the impeller in accordance with signals from the sensors.
- the impeller includes a shroud coupled to the vanes, the sensors being adapted to determine the position of the shroud.
- the impeller typically includes position magnets, the sensors being formed from Hall effect sensors adapted to determine the magnetic field generated by the position magnets.
- the controller is formed from a processing system having a memory and a processor, the processing system being adapted to generate control signals to control the magnetic field generated by the coils in accordance with a predetermined algorithm stored in the memory.
- the processing system is coupled to a signal generator, the control signal being formed by having the processing system cause the signal generator to apply a predetermined current to the coils.
- the fluid pump typically includes a radial bearing for controlling the position of the impeller in a direction orthogonal to the cavity axis.
- the radial bearing includes: a) an inner surface of the housing; and, b) at least a portion of an outer surface of the impeller, the outer surface portion being shaped so as to cooperate with the inner surface such that when fluid is pumped in use, a boundary layer is formed between the inner and outer surface portions, to thereby restrict movement of the impeller in a direction orthogonal to the cavity axis.
- the impeller includes one or more wedges positioned on an outer circumference of the body to thereby cooperate with the inner surface to hydrodynamically control the position of the impeller in a direction orthogonal to the cavity axis.
- the dimensions of the vanes are selected to control at least one of the fluid pressure and the flow rate at the outlet.
- the dimensions include at least one of: a) The height of the vanes; b) The diameters of the impellers; c) The length of the vanes; d) The width of the vanes; e) The inlet and outlet vane angles; f) The shape of the vanes; and, g) The number of vanes.
- the impeller and the cavity have a substantially cylindrical shape.
- the drive system is adapted to move the impeller in a direction parallel to the cavity axis in a reciprocating manner to thereby control induce a pulsatile flow from the outlets.
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; ii) two fluid outlets; and, iii) a set of coils for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having first and second sets of vanes, each set of vanes being adapted to urge fluid from a respective inlet to a respective outlet, in use, wherein the impeller cooperates with a shaped portion of the housing to define first and second cavity portions, each cavity portion including a respective inlet, outlet, and the impeller and shaped portion being configured to substantially prevent fluid transfer between the cavity portions; and, c) a drive system for: i) rotating the impeller about the cavity axis; and, ii) controlling the position of the impeller within the cavity.
- the shaped portion is in the form of an annular ridge extending radially inwardly toward the cavity axis.
- the shaped portion cooperates with a substantially cylindrically shaped vane mounting.
- the vane mounting is used to mount the second set of vanes to the impeller, the second set of vanes having a smaller diameter than the first set of vanes to thereby minimise the cross sectional area of a gap between the impeller and the housing.
- the fluid pump is a fluid pump according to the first broad form of the invention.
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; ii) two fluid outlets; and, iii) a set of coils for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion, each set of vanes being adapted to urge fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the magnetic field in use; c) at least two sensors, the sensors being adapted to detect the position of the impeller within the cavity; d) a radial bearing for controlling the position of the impeller in a direction orthogonal to the cavity axis; e) an axial coupling for
- a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlets; iii) first and second sets of coils for generating respective first and second magnetic fields; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first and second magnetic fields in use; c) at least two sensors, the sensors being adapted to detect the position of the impeller within the cavity; and, d) a controller coupled to the sensors and the first and second sets of coils, wherein in use the controller: i) controls the first magnetic field to thereby control rotation of the imp
- the present invention provides a fluid pump including: a) a housing having an inner surface defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlets; iii) a set of coils coupled the housing for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the magnetic field in use; and, iv) an outer surface, at least a portion of the outer surface being shaped so as to cooperate with a correspondingly shaped portion of the inner surface such that when fluid is pumped in use, a boundary layer is formed between the inner and outer surface portions, to thereby restrict movement of the impeller in a direction orthogonal to the cavity axis
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlet; iii) a set of coils for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first magnetic field in use; c) at least two sensors, the sensors being adapted to detect the position of the impeller within the cavity; and, d) a controller coupled to the sensors and the set of coils, wherein in use the controller controls the magnetic field to thereby control: i) rotation of the impeller about the impeller
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlet; iii) a set of coils to generate a first magnetic field; iv) a set of magnets to generate an axial control magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first magnetic field in use; and, iv) a number of support magnets positioned in the axial control magnetic field to thereby restrict movement of the impeller in a direction parallel to the cavity axis; c) a controller coupled to the set
- the present invention provides a fluid pump including: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; ii) two fluid outlets; and, iii) a first bearing member; iv) a set of coils for generating a respective magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets; and, iv) a second bearing member, the first and second bearing members being in contact in use to thereby restrict movement of the impeller in a direction parallel to the cavity axis; c) a controller coupled to the set of coils, the controller being adapted to control the magnetic field generated by the
- the present invention provides a fluid pump including: a) a housing having an inner surface defining a cavity having a cavity axis, the housing having: i) two fluid inlets; ii) two fluid outlets; iii) a set of coils coupled the housing for generating a first magnetic field; and, iv) a set of magnets coupled to the housing to generate an axial control magnetic field; b) an impeller positioned in the cavity for urging fluid from the inlet to the outlet, wherein the impeller has: i) two body portions defining an impeller axis, ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first magnetic field in use; iv) an outer surface, at least a portion of the outer surface being shaped so as to cooperate with a correspondingly shaped portion of the inner surface such that when fluid is pumped in use
- the present invention provides a method of pumping fluid, using a fluid pump having: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlets; iii) first and second sets of coils for generating respective first and second magnetic fields; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first and second magnetic fields in use; and, c) at least two sensors, the sensors being adapted to detect the position of the impeller within the cavity, wherein the method includes: i) controlling the first magnetic field to thereby control rotation of the impeller about the impeller axis, the housing having:
- the present invention provides a method of pumping fluid using a fluid pump having: a) a housing defining a cavity having a cavity axis, the housing having: i) two fluid inlets; and, ii) two fluid outlets; iii) a set of coils for generating a magnetic field; b) an impeller positioned in the cavity, the impeller having: i) two body portions defining an impeller axis, the impeller axis being substantially parallel to the cavity axis in use; ii) a set of vanes positioned on each body portion for urging fluid from a respective inlet to a respective outlet, in use; iii) a number of driver magnets positioned in the first magnetic field in use; c) at least two sensors, the sensors being adapted to detect the position of the impeller within the cavity, wherein the method includes controlling the magnetic field to thereby control: i) rotation of the impeller about the impeller axis; and, ii) movement of the
- the present invention provides a computer program product including computer executable code which when executed on a suitable processing system causes the processing system to perform the method of tenth or eleventh broad forms of the invention.
- the present invention provides a impeller for use in a fluid pump, the impeller being mounted in a pump cavity and being adapted to urge fluid from first and second inlets to corresponding first and second outlets, wherein the impeller includes: a) a body defining an impeller axis, the body including first and second body end portions; b) a set of vanes positioned on each body end portion for urging fluid from a respective inlet to a corresponding outlet, in use; c) a number of driver magnets positioned in the first and second magnetic fields in use; and, d) an outer surface portion shaped so as to cooperate with a correspondingly shaped portion of the inner surface such that when fluid is pumped in use, a boundary layer is formed between the inner and outer surface portions, to thereby restrict movement of the impeller in a direction orthogonal to the cavity axis.
- the present invention provides a impeller for use in a fluid pump, the impeller being mounted in a pump cavity and being adapted to urge fluid from first and second inlets to corresponding first and second outlets, wherein the impeller includes: a) a body defining an impeller axis, the body including first and second body end portions; b) a set of vanes positioned on each body end portion for urging fluid from a respective inlet to a corresponding outlet, in use; c) a number of driver magnets positioned in the first and second magnetic fields in use; and, d) at least a first part of an axial coupling for restricting movement of the impeller in a direction parallel to the impeller axis.
- the axial coupling includes: a) a second set of coils for generating a second magnetic field; and, b) a number of axial support magnets provided in the body and positioned in the second magnetic field in use, wherein the controller controls the second magnetic field to thereby control movement of the impeller in a direction parallel to the cavity axis.
- the axial coupling includes the first set of coils and a number of axial support magnets provided in the body and positioned in the magnetic field in use, wherein the controller controls the magnetic field to thereby control movement of the impeller in a direction parallel to the cavity axis.
- the axial coupling includes at least one of: a) a set of magnets coupled to the housing to generate an axial control field; and b) a number of axial support magnets provided in the body and positioned in the axial control magnetic field in use to thereby restrict movement of the impeller in a direction parallel to the cavity axis.
- the axial support magnets are the driver magnets.
- the axial coupling includes: a) a first bearing member coupled to the housing; and, b) a second bearing member coupled to the impeller, the first and second bearing members cooperating to thereby restrict movement of the impeller in a direction parallel to the cavity axis.
- the radial bearing includes a second set of coils for generating a second magnetic field, wherein the controller controls the third magnetic field using signals from the sensors to thereby control movement of the impeller orthogonal to the cavity axis.
- the fluid pump includes at least one sensor positioned at a first end of the cavity and at least two sensors positioned at a second opposing end of the cavity.
- the dimensions of the vanes are selected to control at least one of the fluid pressure and the flow rate at the outlet.
- the impeller cooperates with the cavity to define first and second cavity portions, each cavity portion including a respective inlet, outlet, and the impeller and cavity being configured to substantially prevent fluid transfer between the cavity portions.
- Each set of vanes may have substantially identical dimensions to thereby provide fluid at substantially equal pressures and flow rates at the outlets or may have different dimensions to thereby provide fluid at respective first and second pressures at the respective outlet.
- a first outlet is coupled to a second inlet.
- the cavity is substantially rotational symmetric around the cavity axis, the coils being arranged circumferentially spaced around the cavity, in which case the body is typically substantially rotational symmetric around the impeller axis, with the driver magnets being positioned radially outwardly from and circumferentially spaced around the impeller axis.
- driver magnets are positioned radially inwardly of the coils.
- coils are mounted on a yoke that includes slots for receiving the coils.
- the set of coils includes three pairs of first coils, the first coils in each pair being positioned in circumferential opposition, the controller being adapted to cause current to flow through the coils in corresponding directions, to thereby cause rotation of the impeller.
- the controller is adapted to: a) determine a required impeller rotation rate; b) determine a control signal sequence for each pair of first coils; and, c) apply the respective control signal sequence to the respective pair of first coils to urge the driver in a direction predetermined direction thereby causing rotation of the impeller.
- the second set of coils include three pairs of second coils, the second coils in each pair being positioned in circumferential opposition, the controller being adapted to cause current to flow through the coils in counter-corresponding directions, to thereby cause radial movement of the driver member with respect to the cavity axis.
- the controller is adapted to: a) monitor the sensors; b) determine any movement of the driver axis in a direction radial to the cavity axis; c) select one or more pairs of second magnets; d) generate a control signal for each selected pair; and, e) apply the control signal to the respective selected pair to urge the driver in a direction
- the driver magnets include eight circumferentially spaced permanent magnets, the poles of the magnets being aligned perpendicularly to the driver axis, and arranged such that the direction of pole alignment is reversed in adjacent magnets.
- the vanes extend from a surface of the body end portions in a direction substantially parallel to the driver axis, and being positioned radially outwardly from and circumferentially spaced around the driver axis.
- the body includes a substantially cylindrical central body portion positioned between the two body portions, the driver magnets being positioned in the cylindrical central body portion.
- the cavity includes first and second cavity end portions each cavity end portion having: a) an inlet positioned along the cavity axis; and, b) an outlet directed orthogonally with respect to the cavity axis, and arranged radially offset from the cavity axis; and, c) a shape for cooperating with the impeller to allow the vanes to urge fluid from the inlet to the outlet in response to rotation of the impeller.
- the impeller and the cavity cooperate to substantially prevent fluid flow from one cavity end portion to the other, the vanes on each body end portion having a respective height or length to thereby control the pressure or rate of fluid flow at the outlet in the respective end portion.
- the pump includes at least three sensors positioned radially outwardly from and circumferentially spaced about the cavity axis.
- the sensors include a radiation source adapted to emit radiation towards the surface of the respective body end portion and a detector for detecting reflected radiation.
- the impeller includes position magnets, the sensors being formed from Hall effect sensors adapted to determine the magnetic field generated by the position magnets.
- the position magnets are the driver magnets.
- the impeller and the cavity have a substantially cylindrical shape.
- the wedges are provided in a central body portion.
- the axial support magnets are formed from a magnetic material positioned in a magnetic field, such as soft iron.
- each shroud can include driver magnets such as axial support magnets.
- the pump typically includes a set of second magnets provided in each of two cavity end portions, in which case the controller controls the second magnetic field to thereby control movement of the impeller parallel to the cavity axis.
- the fluid pump typically includes an axial coupling for restricting movement of the impeller in a direction parallel to the cavity axis.
- Figures IA to IG are schematic views of an example of a fluid pump incorporating an impeller
- Figures 2A to 2F are schematic plan views of examples of inlet and outlet volutes for use in the pump of Figures IA to IE;
- Figures 3A to 3H are schematic perspective and plan views of examples of impellers for use in the pump of Figures IA to IE;
- Figure 4A is a schematic diagram of an example of a control system
- Figures 4B and 4C are schematic diagrams of the positioning of the sensors of the control system of
- Figures 5A to 5D are schematic diagrams of the use of impeller position to control the relative flows provided by the fluid pump.
- FIG. IA to IF An example of a fluid pump incorporating a double impeller is shown in Figures IA to IF.
- the pump includes a housing 101 having two end portions 101 A, 101B, defining a cavity 102, containing an impeller 103.
- the impeller has two set of vanes 104A, 104B, mounted thereon.
- the housing includes a clearance gap 108A between a rim 108 and the impeller 103, which cooperate to effectively split the cavity 102, into two cavities 102A, 102B, and reduce fluid flow between the two cavities.
- the pump effectively includes two pumps defined by the cavities 102A, 102B.
- the impeller 103 is rotated about an axis shown generally at 107. This causes fluid at the respective inlets 105A, 105B to be urged towards respective outlets 106A, 106B, via volutes 137, as will be appreciated by persons skilled in the art. Position and rotation of the impeller 103 are controlled by coupling magnetic fields generated by two sets of coils H lA, H lB, wound on respective stators 115A, 115B, to driver magnets 109 embedded in a shroud 103D provided on the impeller 103.
- this form of pump assembly can provide either assistance or replacement of both ventricles of a mammalian heart. This is achieved by connecting the inlet 105 A, of the pump to either the left ventricle or atrium, imparting energy to the blood via the double sided centrifugal impeller 103, and connecting the outlet 106A, to the aorta, thus assisting the natural function of the left heart. Additionally, the inlet 105B may be connected to the right ventricle/atrium, with the outlet 106B connected to the pulmonary artery, thus providing right heart assistance. In combination, the device functions to assist both ventricles of a failing heart.
- fluid is drawn from the left ventricle into the cavity 102 A via a canula connected to the inlet 105 A. Fluid passes onto the cylindrical impeller 103, whose vanes 104A urge fluid via the volute
- vanes 104B are designed to provide a flow rate and pressure suitable for the pulmonary circulatory system, which in one example is a pressure of 20 mmHg at a flow rate of 5 L/min. Fluid is transferred via a suitable canula connected to the pulmonary artery.
- the fluid should enter each cavity from a direction substantially perpendicular to the cavity axis.
- the inlet includes a 90° a turn to align entry of the fluid into the cavity 102 along the cavity axis 107.
- inlet volutes 105C, 105D This may be achieved using inlet volutes 105C, 105D, examples of which are shown in Figures 2A and 2B.
- Flow enters the inlets volutes 105C, 105D via respective ports 105E, 105F and is provided with a rotational component by the shape of the volute shown at 105G, and the lip 105H at the impeller eye. This lip 5H also reduces recirculation and potential stagnation in the region.
- the inlet volutes 105C, 105D provide additional anatomical compatibility when implanting the fluid pump beneath a subject's heart. In one example the pump, the inlet, and outlet flow should preferably be in the same plane.
- the axial size of the fluid may be reduced by employing a flattened 'pancake' style inlet volute.
- the inlet volutes 105C, 105D direct blood onto the revolving impeller 103.
- the vanes 104 have the effect of urging blood via respective outlet volutes 137A, 137B, which describe a spiral channel, which leads to a respective one of the outlets 106A, 106B.
- inlet volutes 105 A, 105B may be replaced with an elbow bend, or straight canula parallel to the axis of impeller rotation 107.
- fluid leaving the impeller 103 is collected by split volutes 137A, 137B and transmitted to the outlets 106A, 106B, with the angle of spiral corresponding to the relative angle of flow off the vanes 104 at design conditions.
- FIG. 2C Examples of a number of alternative outlet volutes are shown in Figures 2C to 2F.
- the volutes 137A, 137B commence with a narrow space between the vanes 104 and an inner surface of the cavity 102, known as the 'cutwater' 138A.
- the volute increases in volume and flares out to be continuous with the respective outlet 106A, 106B, or alternatively can further flare out into a diffuser 138C, as shown in Figure 2E.
- This volute structure can help decrease turbulent flow and wall friction during flow as the volume of blood is urged towards the outlet, since fluid velocity is kept uniform, thereby reducing shear stress development and preserving the components of the fluid being pumped.
- the embodiment shown in Figure 2D implements a split volute.
- the radial clearance gap or first volute area 137A between the rotor and the housing increases from the initial point (cutwater) 138A, until it encompasses half or approximately 180° of the impeller.
- a second cutwater 138B is implemented at 180° as the beginning to the second volute 137B.
- the split, or 'double' volute encounters a reduced radial thrust and improved efficiency over a larger operating range, which is encountered by a patient with varying levels of heart failure and thus assistance required during the course of their support.
- Figure 2F shows a concentric volute. Radial hydraulic thrust is reduced only at the best efficiency point of the single volute, whereas concentric volute encounters the most radial thrust over all expected operating conditions.
- Impellers A number of example impeller configurations are described by Figures 3A to 3H.
- the impeller 103 includes respective sets of vanes 104A, 104B, each set of vanes 104 having a shroud 103D mounted thereon.
- the shroud 103D improves hydraulic efficiency as well as providing closer proximity for the magnetic material used in the drive system.
- the shroud can lend itself to potentially higher shear values between the shroud 103D and the wall of the cavity 102, it does increase magnetic flux in the drive and bearing systems, as will be described in more detail below.
- FIG. 3 G An alternative impeller arrangement incorporating a shroud is shown in Figure 3 G.
- FIGs 3D, 3E and 3F A further example of an un-shrouded or semi-open type impeller is shown in Figures 3D, 3E and 3F. This configuration improves the ability to alter fluid output characteristics from each of the outlets 106A, 106B, as will be described in more detail later.
- Figure 3A shows a 'backward inclined' vane embodiment, with outer and inner blade diameter 4D, 4C, outer vane angle 4E, inlet vane angle 4F and vane height 4G, which can be used to produce the desired flow characteristics.
- the vanes 4 can be straight radial in nature as shown in Figure 3H, or forward inclined (not shown).
- differential pressures and flow characteristics is achieved by utilising respective dimensions for the sets of vanes 104A, 104B.
- the difference in pressure is achieved by providing different impeller vanes 104A, 104B on the high pressure impeller side 103 A and low pressure side 103B.
- the vanes 104B on the impeller portion 103B are of a reduced length, as shown in Figure 3 C, when compared to the vanes 104A on the impeller portion 103 A.
- the required flow rates and pressures can be achieved using the following dimensions:
- Impeller end 103B radius R 12.5mm
- vane profile backward, radial, forward dictates the performance characteristic curve. That is, the output pressure and flow rate for a particular system resistance. As such, using a combination of different profiles for each side will alter the output characteristics for each possible operating resistance. This may be advantageous when different output flow rates are required from each outlet port, and dealing with changing systemic and pulmonary resistances, as described in more detail later.
- the drive system is formed from a magnet system formed from the two sets of coils 11 IA, 11 IB, wound on respective stators 115A, 115B, and corresponding driver magnets 109, and which is used to provide both axial suspension and rotation of the impeller 103, with the cavity 102.
- the impeller 103 In use, when the impeller 103 is centrally positioned in the cavity 102, the force required to maintain the position is minimal. However the rotor position is inherently unstable due to the negative stiffness, or attractive force of the permanent magnets to the stator. Therefore, the active magnetic bearing provides additional magnetic flux to counteract any disturbance forces. This practice is common to magnetic motor-bearing systems derived from so called Lorentz and Reluctance theory, as described in "Active Magnetic Bearings : Basics, Properties and Applications of Active Magnetic Bearings", Schweitzer, G. Bleuler, H.,Traxler, A., (1994).
- the stator 115B can be adapted to act solely as a magnetic bearing, coupling to iron 151 on the first end 103B of the impeller, as shown in Figure 4B.
- the rotational torque is only provided by the stator 115A, which has more iron cores, coupled to a suitable number of driver magnets 109 embedded in the end 103 A.
- Stator 115A may be configured as a magnetic motor bearing.
- stator 115 A with 115B and a corresponding switch of magnets 109 with iron target 151.
- Rotational torque can be provided by coupling a three phase motor to magnets 109 embedded in the impeller 103.
- the coils are arranged on a common yoke 115 A, which acts as a stator.
- the yoke is preferably constructed from a laser or water jet cut laminated or sintered iron core, for the purpose of eddy current loss reduction.
- the magnetic field produced by energising these coils with electrical current is coupled to the rotor via a number of permanent magnets embedded in the rotor.
- the magnetic material can be rare-earth, neodynimum, or any material available to provide sufficient magnetic flux.
- twelve coils are coupled to eight permanent magnets, but other numbers amounts could be used.
- the stator may have six slots coupled to four permanent magnets embedded in the impeller. This arrangement allows the bottom stator to produce rotational torque and axial restoring force toward stator 115 A.
- the coils 11 IA may be provided flush on the surface of the yoke 115A (known as a "slotless" arrangement. Compared to other arrangements this results in a lower production of torque, though significantly reduces the degree of negative stiffness instability as well as reducing the inductance and therefore allows for greater rotational speed generation as the EMF generation is lower.
- the coils can be located in slots 115A in the yoke (known as a "slot-type"), so that the yoke extends axially as shown in Figures IA to IG. Greater torque generation is possible for this stator type, however speed is limited due to the relatively larger inductance, although sufficient rotational speed is possible for this application.
- the impeller 103 is cylindrical and employs a shroud 103D to improve hydraulic efficiency as well as providing a region for magnet material placement.
- the magnetic material may be placed beneath the vanes, thus eliminating the shroud requirement.
- magnets can be configured in a Halbach array to improve the flux density. This involves constructing each separate magnet from a plurality of smaller magnets each with slightly changing axial polarity direction. Li use, the driver magnets are arranged with their poles aligned parallel to the axis of the impeller 3, with adjacent magnets having poles aligned in opposing directions. This provides alternating magnetic fields around the impeller.
- Axial Positioning Axial position and tilt can be controlled using a pure axial magnetic bearing located at the housing 101B.
- the stator 115B is constructed with at least four slots with coils wound around each respective pole.
- the magnetic field generated by energising these coils with electrical current couples with an iron only target embedded in the impeller 103 beneath the flat face 151.
- the magnetic fields generated by the coils 11 IB couple directly to iron embedded within the impeller 103, at end 103B. This provides axial bearing control only, and can therefore be used to control the position of the impeller 103 along the cavity axis 107.
- permanent magnetic material may be included in the stator. This arrangement produces bias magnetic flux to attract the iron embedded in the impeller axially toward the stator 115B. The magnitude of this attraction is determined to oppose the axial magnetic attraction of the driver magnets 109 to the stator 115 A. Thus, the impeller has zero resultant attractive permanent magnetic force when located in an axially neutral position, which will be discussed in more detail below with respect to Figure 5D.
- the radial degrees of freedom are restricted by a combination of passive magnetic forces caused by the active axial bearing, coupled with a hydrodynamic journal bearing located at 108.
- the cylindrical circumference of the impeller is constructed from a number of small tapered wedges 130, examples of which are shown in Figure 3B.
- the combination of these wedges and a relative rotational speed cause a thrust force due to the squeezing of fluid through the tapered gap. This radial thrust force is used to balance any radial forces encountered within the pump.
- Hydrodynamic bearing stability is increase by the incorporation of a bias force.
- this may be provided by the weight of the rotor.
- volute casing dictates the magnitude and direction of radial force, and thus can be tuned to act in the desired direction.
- appropriate magnetic forces may be implemented to attract the rotor to the desired radial direction.
- radial control can be provided by a set of coils that generate a magnetic field to thereby control movement of the impeller orthogonal to the cavity axis.
- the controller includes a processing system 20 having a processor 21, a memory 22, and an external interface 23 coupled together via a bus 24.
- An optional input/output device 25 may also be provided.
- the processing system 20 is coupled to four sensors, 26A, 26B, 26C, 26D and a signal generator 27 via the external interface 23.
- the signal generator 27 is coupled to the motor and bearing coils, to allow pairs of opposing coils to be selectively activated as shown generally for the coils 11 IA, H lB.
- the processor 21 determines from data stored in the memory 22 in response to the sensor input, the current that must be applied to the bearing coils to maintain axial position in response to disturbance loads. In the case of desired axial impeller movement to alter output flow rates, a new "zero" set point is determined by the controller, and the impeller axial position is maintained about this new point.
- the processor 21 also determines the current to be supplied to the motor coils in order to provide a required rotation speed. In the case of a heart pump, a single speed may be pre-set before the device is implanted. It will be appreciated that this may be achieved by storing information defining the pre-set speed in the memory 22, using either the I/O device 25, or a remote processing system coupled to the external interface 23.
- signals representing the currents to be supplied are provided to the signal generator 27, which operates to generate appropriate currents, which are then supplied to the motor coils H lA, 11 IB. This will typically involve activating the motor coil pairs in a predetermined sequence in order to create the desired movement of the impeller.
- the pairs of motor coils H lA, 11 IB are driven by three phase currents.
- Exact rotational speed can be monitored by a suitably placed Hall effect sensor mounted to detect the change in driver magnet position with respect to the sensor fixed to a housing position.
- the back EMF encountered in the 1st set of magnets can be related to rotational speed. Once this rate has been determined, it may be fed back to the controller in order for the maintenance of a set rotational speed.
- the sensors 26A, 26B, 26C, 26D located in casing 101B operate by determining the distance "d" between the respective sensor and a surface 113 of the impeller 103, as shown in Figure 4B.
- the determination of the distance between the sensors 26A, 26B, 26C, 26D and the impeller surface 113 can be achieved in a number of ways.
- the sensors 26A, 26B, 26C, 26D can be eddy current sensors adapted to detect the location of the iron 151.
- the magnitude of the current generated in the eddy current sensors can then be used by the processor 21 to derive the position of the impeller 103.
- sensors 26A, 26B, 26C, 26D would be of hall effect type and located in the housing 101A to target the magnets 109 either embedded within the impeller 103 or in the shroud 103D.
- Sensing the position of the impeller using the shroud 103D has the advantage that the distance "d" between the sensor targets (the iron 115 or the magnets 109) and the sensors 26A, 26B, 26C, 26D is less than if the sensor targets 109,115 are positioned in the surface 113 of the impeller.
- the vanes 104 will periodically pass between the sensors 26A, 26B, 26C, 26D and the surface 113, which can affect the measurements.
- the use of the shroud 103D tends to allow the processor to determine the position of the impeller faster and more accurately, with a higher degree of resolution.
- the presence of the shroud 103D can reduce the effectiveness of the impeller 103, by generating higher shear stresses within the respective cavity 102 A, 102B. This is undesirable for some applications, such as use of the system as a heart pump.
- each sensor may be formed from a radiation source such as an LED laser, or the like and corresponding optical detector, as will be appreciated by persons skilled in the art. Other techniques may also be used.
- An alternative method of sensing the position of the impeller within the cavity 102 relates to the so called 'self sensing' technique, whereby the voltage and current waveforms of each motor and/or bearing coil can be monitored by the processing system 20 to sense the position of the impeller.
- a component of the current waveform is related to the circuit inductance, which in turn varies inversely with axial movement of the permanent driver magnets 109 in the air gap. Recording and analysing the back EMF voltage generated by the motor achieves rotational position sensing, with signals from the bearing coils determining the position.
- the bearing coils and the motor coils 11 IA, 11 IB form the sensors 26.
- the processor will use a predetermined algorithm to determine the current that needs to be applied to selected pairs of bearing coils H lB. An indication of this is transferred to the signal generator 27, which in turn responds by generating appropriate currents and applying these to the selected ones of the bearing coils 11 IB. The current in the coils 11 IB causes the impeller body to move in the axial direction.
- the sensors 26 can also be adapted to determine the rotational position of the impeller 1033, thereby allowing the rate of rotation to be monitored and adjusted by the processing system 20.
- the sensors 26 can be mounted to target onto the iron target beneath the flat impeller surface 113, to directly sense motion in the axial direction only, as required for the axial type magnetic bearing.
- the impeller may experience some degree of tilt about the radial x and y axis.
- the axial magnetic bearing 11 IB can be used to reduce the effect. For example, this may be achieved by increasing the electrical current to the coil 11 IB located perpendicularly to the axis of tilt whilst reducing the current to the symmetrically opposite coil.
- the impeller may also encounter hydraulic or external forces causing displacement of the impeller axially. Additional forces resulting in movement toward the stator 115A can be opposed by increasing the current supplied to the coils H lB of stator 115B. Similarly, forces causing impeller displacement toward stator 115B can be reduced by reducing the current supplied to the coils H lB. Additionally, when employing a magnetic motor bearing at 11 IA, current may be increased to the bearing coils in response to the latter condition to provide additional restoring force. It will be appreciated from the above that a number of different axial and radial bearings can be provided, together with a number of different rotational drives. These may be used in any combination, together with an impeller having a cylindrical shape.
- the system can use varying combinations of:
- active axial suspension provided by magnetically coupling coils in the pump housing with permanent magnets or iron in the impeller;
- This axial magnetic bearing configuration enables control of the physical axial "zero" position within the pump cavity. This technique provides the unique ability to alter the respective outflow from the outlets 106A, 106B, which will be described in further detail later.
- the profiles of the sets of vanes 104 A, 104B may be of different shape (backward, radial, forward). This enables the single impeller device to change relative flow rates by altering rotational speed. Take for example a backward facing profile for the vanes 104 A, which correspond to the left side of the heart, and a radial/forward facing profile for the vanes 104B, which correspond to the right side of the heart.
- Operating the pump at a set speed produces a balanced flow from the outlets 106A, 106B. With unchanged systemic and pulmonary resistances, reducing the speed reduces the flow from the outlet 106A, while the flow from the outlet 106B is reduced to a lesser degree. Similarly, increasing the impeller speed increases the flow from the outlet 106A while the flow from the outlet 106B increases to a lesser degree. It is therefore possible to alter relative flow rates from either outlet 106A, 106B by altering rotational speed.
- the left and right impeller vanes may be un-shrouded or semi-open.
- the efficiency of this impeller type is extremely sensitive to the axial clearance above the impeller vanes. This property can be used to provide altering flow rates from the outlets 106A, 106B.
- the impeller 103 when the impeller 103 is situated in the axially neutral position as shown in Figure 5C, flows to the outlets 106A, 106B are in balance at 5 L/min. Urging the impeller 103 in the direction of arrow 115 in Figure 5B reduces the clearance between the impeller 103A and housing 101A. This improves the efficiency of the pump defined by the cavity 102A, thereby increasing the blood flow to the outlet 106A.
- the magnetic bearing system employed has a limit to the range of axial actuation.
- the efficiency and thus output flow rates of each impeller is dependant on the relative ratio of axial clearance and impeller vane height. Therefore, impeller vane heights must be small to obtain a sufficient change in efficiency and consequent range of output flow rates for small actuations.
- the combination of these techniques enables the single BVAD device to output varying flow rates from the left and right outlets in response to the requirements of the systemic and pulmonary circulatory systems.
- appropriate axial movement of the impeller 103 can be used to induce a pulsatile flow. That is, reciprocal movement of the impeller 103 along the axis 107 within the cavity 102 will repeatedly improve and then reduce the efficiency of the pumps defined by the cavities 102 A, 102B. This creates periodic fluctuations in blood flow to each of the outlets 106A, 106B, thereby resulting in a pulsatile flow for the left and right sides of the heart accordingly.
- the controller operates to increase the average the time the impeller spends close to the cavity 102 A, 102B for the pump side requiring more flow, whilst still maintaining a degree of axial reciprocation.
- a small clearance gap 150 is provided as shown in Figure 5D. This gap is defined between an annular ridge 151, which extends radially inwardly of the housing 10 IB, and a vane mounting 152 on which the second set of vanes 104B are mounted.
- the vane mounting 152 has a substantially cylindrical shape, as shown. This helps ensure that the gap between the vane mounting 152 and the ridge 151 is minimised. Additionally however, this also ensures that there is no variation in the size of the gap 150 when the impeller 103 is moved in a direction parallel to the cavity axis 107, as described above.
- This arrangement is also used as the second vanes 104B have a smaller diameter than the first vanes 104A.
- this effective cross sectional area of the clearance gap is smaller than if it were provided at the perphery of vanes 104 A, and therefore reduces the effective gap area and thus the overall amount of leakage from left to right cavities considerably.
- Physiological control of assist devices is desirable to accommodate changes in patient activity.
- a parameter must be identified to be indicative of changing physiological requirements.
- This parameter may be Heart Rate.
- Heart rate can be inferred in this device from magnetic bearing current.
- the failing heart has some latent ability to produce pressure and flow. This reduces the output performance requirements of the device during the systolic period, as the heart assumes some of the load. Therefore, a variable load will be placed on the axial magnetic bearing and motor.
- the power requirements to provide rotation and sustain axial suspension will vary with each heart beat, and this can be recorded to determine the heart rate. For example, an increase in heart rate may indicate increased activity, therefore pump speed may be increased accordingly.
- the fluid pump as a heart assist device
- the fluid pump it is possible for the fluid pump to be used for other purposes, and indeed any fluid pumping application where the pressure and flow rates fall within the operating parameters of the device.
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Abstract
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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AU2004906579A AU2004906579A0 (en) | 2004-11-17 | Fluid pump | |
AU2004906579 | 2004-11-17 |
Publications (1)
Publication Number | Publication Date |
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WO2006053384A1 true WO2006053384A1 (fr) | 2006-05-26 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/AU2005/001748 WO2006053384A1 (fr) | 2004-11-17 | 2005-11-17 | Pompe à fluide |
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