II. Brief Description of the Related Art Blood pumps used in surgical procedures such as cardiopulmonary bypass (CPB) and coronary artery bypass grafting (CABG) are single-use devices. These blood pumps are generally powered by a reusable motor which drives the pump through a magnetic coupling. However, the reusable motors are not sterilizable. Thus, the motor and attached pump are positioned outside the sterile surgical field at a location away from the patient. The disposable pump which is driven by the motor is connected to the patient by long lengths of tubing which transport the patient's blood to and from the blood pump. The long lengths of tubing increase the priming volume of the pump which is the amount

of the patient's blood and/or saline which must be drawn into the tubing and the pump to prime the pump before blood begins to be returned to the patient.

Long lengths of tubing connecting the pump to the patient also increase the amount of foreign material which comes into contact with the patient's blood, increasing trauma to the patient. A typical CPB circuit includes several feet of flexible tubing that the patient's blood flows through. In order to prevent blood clots, the patient's blood is generally treated with Heparin. The use of Heparin is preferably minimized because Heparin prevents the blood from clotting.

In addition to the priming volume problem with known blood pumps, the magnetic coupling for transmitting rotation between the pump and the motor has associated disadvantages. With the magnetic coupling, accurate measurements of the load on the pump are difficult to obtain because of the possible slippage that occurs between the magnets of the magnetic coupling. Because the coupling is not direct, the magnetic plates may slip relative to each other resulting in the motor turning faster than the pump impeller. Further, the current drawn by the motor to control the rotation of the rotor is used to measure impeller loads. Due to the possible slippage of the magnetic coupling between the pump impeller and motor unit, an accurate measurement of current is difficult to obtain.

Previous attempts to move the blood pump closer to the patient have involved the use of a cable drive between the motor and the pump which allows the sterile pump to be located within the sterile surgical field while the motor is placed outside of the sterile surgical field. The use of a cable drive increases the load on the motor due to friction between the cable housing and the cable and makes it more difficult to accurately control the pumping volume due to rpm fluctuations. Also, the use of a cable

introduces the possibility of the cable breaking or becoming kinked during the surgical procedure causing pump failure.

Blood pumps may be used during still heart surgery where the bypass pump is needed to perform the work of the heart. Alternatively, heart surgery may be done on a beating heart. During beating heart surgery the blood pump is used to provide supplemental support. In addition, during a beating heart surgical procedure the heart may fibrillate and cease pumping blood thereby requiring full support. Therefore it is necessary that the blood pump utilized for beating heart supplemental support be capable of providing full CPB support if needed. In either stopped heart or beating heart surgery, it is desirable to minimize the priming volume of the blood pump by placing the pump as close as possible to the surgical site. By placing the pump closer to the surgical field, the amount of saline required to prime the bypass circuit is reduced which reduces the likelihood that a transfusion will be required.

Accordingly, it would be desirable to provide a blood pump which can be positioned within the surgical field close to the surgical site to minimize the priming volume of the pump. In order to position the pump within the surgical field close to the heart, the pump and associated motor must be provided in a sterile condition.

SUMMARY OF THE INVENTION One aspect of the present invention involves a blood pump system. The blood pump system comprises a housing having an impeller chamber and a motor chamber. The impeller chamber includes a fluid inlet and a fluid outlet.

The motor chamber includes an access aperture. A motor is disposed in the motor chamber, the motor having a stator and a rotor. An impeller is disposed in the impeller chamber and coupled to the rotor. A sealing member is provided for selectively sealing the access aperture to

enclose the motor within the motor chamber of the housing.

In one embodiment of the blood pump, the stator is generally cylindrical and includes a generally cylindrical receiving area for receiving the rotor therein.

In one embodiment of the blood pump, the housing includes a plate member disposed between the motor chamber and the impeller chamber, and a generally cylindrical rotor housing extending from the plate member into the motor chamber, and wherein the stator is received between a side wall of the housing and the rotor housing.

In one embodiment of the blood pump, the plate member and the rotor housing are selectively removable from the housing.

In one embodiment of the blood pump, a registration assembly is provided for registering the stator in a predetermined orientation within the motor chamber.

In one embodiment of the blood pump, the fluid inlet is generally axial with respect to a longitudinal axis of the housing, and the fluid outlet is generally tangential to the longitudinal axis of the housing.

In one embodiment of the blood pump, the fluid inlet is generally axial with respect to a longitudinal axis of the housing, and the fluid outlet is generally coaxial with the fluid inlet.

In one embodiment of the blood pump, a sleeve member is provided extending from the housing.

In another aspect of the present invention, a blood pump assembly is provided. The blood pump assembly comprises a pump having a blood inlet, a blood outlet, and an impeller for pumping blood from the inlet to the outlet.

A motor is provided having a stator and a rotor, the rotor being coupled to the impeller. A housing is provided having a stator chamber for selectively isolating the stator from a surrounding environment.

In one embodiment of the blood pump assembly, the

housing comprises a flexible sleeve extending from the pump over the stator element.

In one embodiment of the blood pump assembly, the housing comprises a structure having a motor chamber for receiving the stator and rotor therein, and an impeller chamber for receiving the impeller therein.

In one embodiment of the blood pump assembly, a plate member is provided positioned between the motor chamber and the impeller chamber. A generally cylindrical member is provided extending from the plate member into the motor chamber for receiving the rotor therein.

In one embodiment of the blood pump assembly, a registration assembly is provided for registering the stator in a predetermined orientation within the motor chamber.

In one embodiment of the blood pump assembly, the registration assembly includes a first registration element formed as part of the housing, and a second registration element formed as part of the stator. The second registration element is engageable with the first registration element to position the stator in the predetermined orientation within the motor chamber.

In one embodiment of the blood pump assembly, the first registration element is one of a pin member and an elongated key member extending from an interior surface of the motor chamber. The second registration element is a recess formed on the stator for receiving one of the pin member and the key member.

In one embodiment of the blood pump assembly, the housing is evacuated to form a vacuum around the stator such that if a seal in the pump fails, fluid flowing past the seal in the pump will be drawn into the housing so as to prevent the introduction of the fluid into the patient's blood stream.

In a still further aspect of the present invention,

a method of pumping blood during heart surgery is provided, comprising the steps of: (a) sealing a stator within a sterile pump housing; (b) coupling a rotor disposed within the stator to an impeller; (c) placing the sterile pump housing within a sterile surgical field; and (d) energizing the stator to rotate the rotor and thereby pump a patient's blood.

In one embodiment, the method of pumping blood includes the steps of removing the stator from the sterile pump housing, disposing of the sterile pump housing, and reusing the stator.

In one embodiment, the method of pumping blood includes the step of providing a plate member disposed between the impeller and the stator, and a cylindrical element extending into a rotor receiving area formed in the stator.

In one embodiment, the method of pumping blood includes the step of providing the sterile pump housing as a flexible sleeve extending over the stator.

In another aspect of the present invention, a blood pump is provided. The blood pump comprises a disposable blood pump having a blood inlet, a blood outlet, and an impeller for pumping blood from the inlet to the outlet.

A reusable stator is provided configured to be received within a selectively sealable chamber of the disposable blood pump such that the disposable blood pump forms a sterile housing surrounding the stator to isolate the stator from a surrounding environment. A coupler is provided for coupling a rotor disposed within the stator and the impeller.

In one embodiment of the blood pump, the coupler is a magnetic coupling.

In one embodiment of the blood pump, the coupler is a mechanical coupling.

The present invention provides advantages of a

compact blood pump and motor assembly which can be placed within the sterile field close to the surgical incision or even within the chest cavity.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which like elements bear like reference numerals, and wherein: FIG. 1 is an exploded perspective view of a blood pump according to the present invention; FIG. 2 is a side cross sectional view of a pump element with the motor removed; FIG. 3 is a cross sectional end view of the pump element taken along line 3-3 of FIG. 2; FIG. 4 is a side view of a cap for the sterile motor housing; FIG. 5 is an exploded side cross sectional view of the pump element according to the present invention with the motor removed; FIG. 6 is an exploded perspective view of a blood pump with a coaxial blood inlet and blood outlet; FIG. 7 is an exploded side view of a blood pump with a flexible sleeve; FIG. 8 is an assembled side view of the blood pump with the flexible sleeve of FIG. 7 illustrating the flexible sleeve in an expanded condition; FIG. 9 is a side cross sectional view of an alternative embodiment of a blood pump with a magnetic motor coupling; and FIG. 10 is a side cross sectional view of an alternative embodiment of a blood pump with a mechanical motor coupling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A blood pump 10 having a reusable motor stator element 12, a pump body 14, and a cap 16, is illustrated in

FIG. 1. The entire blood pump 10 is sufficiently small that it may be placed within the surgical field during CPB and other heart surgery. The pump body 14 and cap 16 together provide a sterile casing for the reusable motor stator element 12. The motor stator element 12 when completely encased by the body 14 and cap 16 does not need to be sterile and can be reused. The reusable motor stator element 12 reduces the overall cost of the blood pump 10 by allowing the user to reuse the stator element numerous times, thereby reducing the overall per unit cost of the entire blood pump 10. In addition, the blood pump 10 according to the present invention greatly reduces the priming volume of the system when placed close to the patient thereby reducing the amount of saline and anti- coagulants which are introduced into the patient's blood.

By placing the pump 10 close to or within the surgical field, the likelihood that a patient will require a blood transfusion is reduced. The pump 10 according to the present invention can be used for either beating heart or still heart surgeries.

As illustrated in FIGS. 1 and 2, the pump body 14 includes a blood inflow port 26 arranged axially with respect to a pump impeller 18 and a blood outflow port 28 arranged substantially tangentially to an exterior of the pump body 14. The pump body 14 has a cylindrical side wall 30 extending from an impeller chamber 32 and configured to surround the reusable motor stator 12.

FIG. 2 illustrates the impeller 18 arranged in the impeller chamber 32 and non-rotatably connected to a cylindrical magnet 34 positioned within a magnet housing 44. The magnet housing 44 hermetically seals the impeller chamber 32 from the motor stator 12 and affords protection against the formation of emboli. Bearings 36,38 rotatably support the cylindrical magnet 34 and impeller 18. The impeller 18 is connected to the cylindrical magnet 34 by a

shaft 40 extending through a flexible blood seal 42. The blood seal 42 may be constructed of Teflon, silicone, or any other bio-compatible material which prevents blood from the impeller chamber 32 from passing into the magnet housing 44. The cylindrical magnet 34 and bearings 36,38 are surrounded by and supported in the magnet housing 44 which has a generally cylindrical shape and is configured to be received within a central bore of the reusable motor stator element 12. The impeller 18 includes a plurality of vanes arranged to move the blood from the inflow port 26 to the outflow port 28. As is known in the art, the vanes preferably do not contact the walls of the impeller chamber 32.

The reusable motor stator element 12 may be any of a variety of known motor elements, including but not limited to a cylindrical central bore 48 for receiving and driving a rotatable cylindrical magnet element such as the cylindrical magnet 34. One example of a suitable motor stator element 12 is available as motor # 22anl00aa from Koford Engineering, Lisle, IL.

The motor stator element 12, as shown in FIG. 1, includes two locating recesses 50,52 in a top surface 54 thereof. The motor stator element 12 also includes a longitudinal groove 56 along a cylindrical side surface 58 of the element. The locating recesses 50,52 and the longitudinal groove 56 function to allow the pump body 14 to be received over the motor stator element 12 in only one particular desired orientation.

The pump body 14, as shown in FIGS. 2 and 3, preferably includes two locating pins 60,62 which correspond to the locating recesses 50,52 in the motor stator element 12. The pump body 14 also includes an interior key element 64 which is configured to be received in the longitudinal groove 56 in the motor stator element 12. It should be understood that one or more of the

locating features described above may be used with or without the other locating features.

FIG. 4 shows the locking cap 16 which is received over a bottom surface 66 of the motor stator element 12 and provides electrical connections to the motor stator. The locking cap 16 includes an electrical cable 70 connected to an electrical connector 72 of the cap. The cap 16 also includes a locking element 76 and an annular sealing member 78. The cap 16 snaps onto the pump body 14 when the locking element 76 which is preferably a flexible element snaps into a groove 80 in the interior surface of the pump body cylindrical side wall 30. The annular sealing member 78 of the cap 16 is received in a sealing groove 82 in the pump body 14. When assembled, the pump body 14 and cap 16 provide a secure fluid tight hermetic seal to prevent contamination from the non-sterile motor stator element 12 from escaping into the sterile environment in which the blood pump 10 has been placed.

When assembled, the motor stator chamber may be evacuated through a port (not shown) disposed on the cap 16. Once evacuated, the chamber surrounding the motor stator 12 may be left in a state of negative pressure or carbon dioxide may be introduced into the chamber to equalize the pressure. If the fluid tight seal provided by the magnet housing 44 fails, the negative pressure or carbon dioxide in the motor stator chamber prevents air bubbles or emboli from entering the patients blood stream.

In fact, if any of the seals between the pump body 14 and the motor stator 12 fail because of high suction pressure or some other unforeseen accident, air will not enter the patient's blood stream. Instead, if there is a vacuum in the motor stator chamber, the motor stator chamber will fill with blood and the leak will stop. If the motor stator chamber is filled with carbon dioxide, blood will readily absorb the carbon dioxide without the danger of

emboli formation.

Although the invention has been illustrated with a two component housing formed by the pump body 14 and the cap 16, it should be understood that the sterile housing may be formed from two or more members. The cylindrical side walls 30 may be formed as a part of the pump body 14, as shown, or as a part of the cap 16. Alternatively, the sterile housing may be formed around the motor stator element 12 as a one-piece molded element.

After use and before disposal of the blood pump 10, the removable motor stator element 12 may be removed for reuse. In order to remove the motor stator element 12, the locking cap 16 is removed from the pump body 14 and the motor stator element 12 slides out of the pump body.

Although the motor stator element 12 is preferably reusable, the entire blood pump assembly may also be disposable.

FIG. 5 illustrates one embodiment of a pump body 14 formed from two separate injection molded parts including a main body assembly 86 and a back plate assembly 88. The impeller 18 and cylindrical magnet 34 are assembled and inserted into the main body assembly 86. The back plate assembly 88 is then inserted into the main body assembly 86 until a flange 90 on the back plate assembly 88 abuts a corresponding flange 92 on the main body assembly 86. The parts may be secured together with a bio-compatible glue, by ultrasonic welding, or any other known joining technique.

The locking cap 16 may be formed as a single injection molded piece. The electrical cable 70 and electrical connector 72 may be inserted into the locking cap 16 after molding and secured in place in a known fluid tight manner, such as with a bio-compatible glue.

Alternatively, the electrical connector 72 may be secured within the locking cap 16 during the molding process. The

electrical connector 72 is configured to be received in a corresponding electrical connector of the motor stator element 12 and provides power to the motor and feedback from the motor stator element to a control panel. In addition, the cable 70 may include a plurality of gas lines that can be used to cool the motor stator element. One of the gas lines may be used for delivery of carbon dioxide cooling gas and another of the gas lines would be connected to a vacuum to withdraw heated carbon dioxide.

FIG. 6 illustrates an alternative embodiment of a blood pump 100 including a reusable motor stator element 102, a pump body 104, and a cap 106. The pump body 104 includes an axial blood inlet 108 and a coaxial blood outlet 110 surrounding the blood inlet 108. According to this coaxial blood pump embodiment of FIG. 6, a single coaxial blood tube can be used to deliver blood to and from the patient. This configuration provides space savings and allows the blood tubing to enter the patient through a single incision.

FIG. 7 and 8 illustrate an alternative embodiment of the blood pump 10 of FIG. 1 in which a sterile sleeve 120 is connected to an end of the pump body 14. The sterile sleeve 120 is formed of a flexible material such as polypropylene, polyethylene, or the like, and may be connected to the pump body 14 before or after sterilization of the pump body. According to the embodiment of FIG. 7 and 8, the sterile sleeve 120 is initially folded or otherwise compressed longitudinally and secured to the end of the pump body 14. Once the motor stator element 12 has been inserted into the pump body 14 and the cap 16 has been attached to the pump body, the sterile sleeve 120 is drawn down over the cap and the electrical cable 70. The sterile sleeve 120 allows the use of a nonsterile cap 16 and electrical cable 17 and provides a sterile environment.

Alternatively, the cap 16 may be eliminated entirely or

permanently connected to the motor stator element 12. The integral cap and motor stator element will eliminate the need for the electrical coupling.

FIG. 9 illustrates an alternative embodiment of a blood pump 130 in which the motor stator element 132 is received within a pump body 134 and a magnetic coupling 136 connects an output shaft of the motor stator element with the impeller 138 of the pump body. The magnetic coupling 136 includes a first magnetic disk 140 connected to the output shaft of the motor stator element 132 and a second magnetic disk 142 secured to a shaft of the impeller 138.

The pump body 134 is provided with a sealing partition 144 between the first and second magnetic disks 140,142.

A further alternative embodiment of a blood pump 150 having a mechanical coupling between the rotor (not shown) within the stator element 152 and an impeller 154 of a pump body 156 is shown in FIG. 10. More specifically, the impeller 154 is provided with a square shaft 160 which is connected to a corresponding square socket 162 fixed to a shaft attached to the rotor disposed within the stator element 152. It should be understood that the square shaft 160 and corresponding socket 162 may be replaced with any other known mechanical coupling system.

According to a further alternative aspect of the present invention, the blood pump according to the present invention may be utilized as an implanted cardiac assist pump by eliminating the electric cable 70 and providing an implantable rechargeable battery within the pump.

Preferably, the pump contains a rechargeable battery arranged in the pump housing so that the battery is adjacent the patient's skin surface. The battery can then be recharged by placing an inductive charger over the battery on the exterior of the patient's skin.

The blood pumps 10,100,130,150 according to the present invention each provide a compact, sterile blood

pump which can be placed within the surgical field and even within the chest cavity during heart surgery. The blood pump 10 may be used during beating heart or still heart surgery and may by used for minimally invasive surgery where the heart is accessed through the ribs or for conventional open chest surgery.

While the invention has been described in detail with reference to the preferred embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention.

For example, it is to be readily understood that, while the present invention advantageously provides the ability to place a non-sterile stator within a sterile housing for placement within a sterile surgical field, it is within the scope of the invention to place a sterilized stator within the sterile housing.