Patent ID: 12226623

DETAILED DESCRIPTION OF THE INVENTION

The illustrations generally show preferred and non-limiting examples of the apparatus and methods of the present disclosure. While the description presents various aspects of the apparatus, it should not be interpreted in any way as limiting the disclosure. Furthermore, modifications, concepts, and applications of the disclosure's aspects are to be interpreted by those skilled in the art as being encompassed by, but not limited to, the illustrations and descriptions herein.

The following description is provided to enable those skilled in the art to make and use the described examples contemplated for carrying out the disclosure. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present disclosure.

For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the disclosure as it is oriented in the drawing figures.

As used herein, the term “substantially parallel” means a relative angle as between two objects (if extended to theoretical intersection), such as elongated objects and including reference lines, that is from 0° to 5°, or from 0° to 3°, or from 0° to 2°, or from 0° to 1°, or from 0° to 0.5°, or from 0° to 0.25°, or from 0° to 0.1°, inclusive of the recited values.

As used herein, the term “substantially perpendicular” means a relative angle as between two objects (if extended to theoretical intersection), such as elongated objects and including reference lines, that is from 85° to 90°, or from 87° to 90°, or from 88° to 90°, or from 89° to 90°, or from 89.5° to 90°, or from 89.75° to 90°, or from 89.9° to 90°, inclusive of the recited values.

It is to be understood, however, that the disclosure may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary aspects of the disclosure. Hence, specific dimensions and other physical characteristics related to the examples disclosed herein are not to be considered as limiting.

It should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and/or” unless specifically stated otherwise, even though “and/or” may be explicitly used in certain instances. Further, in this application, the use of “a” or “an” means “at least one” unless specifically stated otherwise. The term “at least” is synonymous with “greater than or equal to”. As used herein, “at least one of is synonymous with “one or more of. For example, the phrase “at least one of A, B, and C” means any one of A, B, or C, or any combination of any two or more of A, B, or C. For example, “at least one of A, B, and C” includes one or more of A alone; or one or more B alone; or one or more of C alone; or one or more of A and one or more of B; or one or more of A and one or more of C; or one or more of B and one or more of C; or one or more of all of A, B, and C.

Referring to the drawings, in which like reference characters refer to the like parts throughout the several views thereof,FIG.1illustrates a rotary blood pump10in accordance with one example of the present invention. The rotary blood pump10may be used, for example, in an extracorporeal circuit for supporting the function of a patient's heart and/or lungs. Generally, the rotary blood pump10has a pump housing12with an upper or inlet housing portion14and a lower or outlet housing portion16. The inlet housing portion14and the outlet housing portion16may be removably or non-removably coupled together and define a pumping chamber18therebetween. In some examples, the inlet housing portion14is formed as a separate component that is removably or non-removably secured to the outlet housing portion16(seeFIG.2). The pumping chamber18may have a substantially cylindrical structure defined by a sidewall24extending circumferentially around a central longitudinal axis26.

With continued reference toFIG.1, the inlet housing portion14has an inlet20that is in fluid communication with the pumping chamber18for delivering blood into the pumping chamber18. The inlet20has a tubular shape with an inlet axis42that is substantially parallel with the central longitudinal axis26of the pumping chamber18. The inlet20may have a circular cross-sectional shape, an oval cross-sectional shape, or any other geometric shape, such as polygonal. In some examples, the inlet axis42may be angled relative to the central longitudinal axis26. The inlet axis42may be substantially coaxial with the central longitudinal axis26. In some examples, the inlet axis42may be offset radially relative to the central longitudinal axis26. The inlet20has one or more barbs30or other connection elements to facilitate connecting with an inlet tube (not shown).

With continued reference toFIG.1, the outlet housing portion16has an outlet22in fluid communication with the pumping chamber18for delivering blood from the pumping chamber18. The outlet22has a tubular shape with an outlet axis44that is substantially perpendicular relative to the central longitudinal axis26of the pumping chamber18. The outlet22may have a circular cross-sectional shape, an oval cross-sectional shape, or any other geometric shape, such as polygonal. In some examples, the outlet axis44may be angled relative to the central longitudinal axis26and/or the inlet axis42. The outlet22has one or more barbs30or other connection elements to facilitate connecting with an outlet tube (not shown).

With continued reference toFIG.1, an impeller34is rotatably supported within the pumping chamber18and is configured for pumping blood from the inlet20to the outlet22. The impeller34is rotatably driven by a drive mechanism36. As described herein, the drive mechanism36is configured to rotate the impeller34about the central longitudinal axis26such that the impeller34pumps blood from the inlet20to the outlet22. The impeller34is rotatably supported within the pumping chamber18by a bearing mechanism38. As described herein, the bearing mechanism38assists in positioning the impeller34within the pumping chamber18such that the impeller34rotates about the central longitudinal axis26without touching the sidewall24of the pumping chamber18.

With reference toFIG.3, the inlet housing portion14has a cover40that encloses the pumping chamber18. The inlet20is monolithically formed with the cover40and protrudes therefrom in a direction of inlet axis42. As described herein, the inlet axis42may be substantially parallel with the central longitudinal axis26(shown inFIG.2). The cover40may have a substantially circular shape with at least a portion of the outlet22extending tangentially from an outer circumference of the cover40in a direction of an outlet axis44. As described herein, the inlet axis42and the outlet axis44may be substantially perpendicular to one another. In some examples, the cover40may have a first portion of the outlet22while the outlet housing portion16(shown inFIG.1) may have a second portion of the outlet22such that, when combined, the cover40and the outlet housing portion16together define the outlet22. In some examples, the cover may have a circumferential groove32(shown inFIG.5) that interacts with a corresponding projection on the outlet housing portion16to position the cover40over the outlet housing portion16.

With reference toFIGS.4A-4B, the inlet housing portion14has at least one strut46connected to an inner sidewall48and extending radially inward toward the inlet axis42. For example, the strut46may be monolithically formed with the inlet housing portion14, or it may be formed as a separate component that is removably or non-removably connected to the inner sidewall48of the inlet20. The strut46has a single connection point with the inner sidewall48of the inlet20in a circumferential direction around the inlet axis42when viewed in a cross-sectional plane perpendicular to the inlet axis42. With reference toFIG.4C, the strut46has a first radial end46aconnected to the inner sidewall48of the inlet20and a second radial end46bprotruding a radially inward from the first radial end46aand toward the inlet axis42. In some examples, the first radial end46aof the strut46is connected to the inner sidewall48of the inlet housing portion14at a circumferential position about the inlet axis42such that a major axis of the strut46between the first radial end46aand the second radial end46band the outlet axis44define a predetermined angle α in the cross-sectional plane perpendicular to the inlet axis42, such as shown inFIGS.4A-4B. The major axis of the strut46between the first radial end46aand the second radial end46bmay be coincident with the inlet axis42. In some examples, the predetermined angle α has an absolute value of about 0° to about 135°, preferably about 15° to about 90°, more preferably about 30° to about 60°, more preferably about 40° to about 50°, more preferably about 43° to about 47°, such as about 45°. The predetermined angle α is based on an orientation of the strut46wherein the second radial end46bof the strut46extends in a direction toward the outlet axis44rather than away from the outlet axis44, or wherein the second radial end46bof the strut46extends in a direction away from the outlet axis44rather than toward the outlet axis44.

With reference toFIGS.5A-5C, the first radial end46aof the strut46may be connected to the inner sidewall48of the inlet20along a connection surface47that is substantially parallel with the inlet axis42. As shown inFIG.5B, a first axial end49aof the strut46is positioned proximate to the inlet20(shown inFIG.3) at an angle β relative to the inlet axis42when viewed in a cross-sectional plane parallel to the inlet axis42. The angle β is about 15° to about 75°, preferably about 30° to about 60°, more preferably about 40° to about 50°, such as about 45°. The angle β is configured to smooth the blood flow around the strut46at a leading end of the strut46defined by the first axial end49a. A second axial end49bof the strut46is positioned opposite the first axial end49a. The second axial end49bof the strut46is positioned proximate to the outlet22(shown inFIG.3) at an angle γ relative to the inlet axis42when viewed in a cross-sectional plane parallel to the inlet axis42. The angle γ is about 15° to about 75°, preferably about 30° to about 60°, more preferably about 40° to about 50°, such as about 45°. The angle γ is configured to smooth the blood flow around the strut46at a trailing end of the strut46defined by the second axial end49b. A terminal portion50of the second axial end49bis positioned substantially coaxially with the inlet axis42. The terminal portion50has a bearing support member51configured for supporting at least a portion of an axial bearing. As described herein, the axial bearing is configured for supporting the axial load on the impeller34directed along the inlet axis42.

With reference toFIG.5C, the strut46is desirably shaped to reduce flow stagnation around the strut46. In some examples, at least a portion of the strut46has a teardrop or an airfoil cross-sectional shape. In such examples, the first axial end49adefines a leading edge or end, while the second axial end49bdefines a trailing edge or end. The strut46may gradually widen from the first axial end49ato a maximum thickness point T, and then gradually narrow from the maximum thickness point T to the second axial end49balong a chord line C. The chord line C is substantially parallel with the inlet axis42. By varying the position of the maximum thickness point T between the first and second axial ends49a,49b, a pressure profile of the strut46can be changed to reduce or eliminate damage to the blood cells within the blood flowing around the strut46.

Without intending to be bound by theory, it has been found that positioning the strut46at the predetermined angle α, particularly in the range a range of about 45°, reduces or eliminates fluttering or vibration of the strut46due to blood flowing through the inlet20during pump operation. Such fluttering or vibration of the strut46may lead to premature damage or failure of the strut46, in addition to disrupting the blood flow around the strut46. While it is possible to reduce such vibration of the strut46by making the strut46and the inlet housing14from a high strength material, such as stainless steel or titanium, positioning the strut46at the predetermined angle a allows the strut46and the inlet housing14to be made from a lower strength material, such as medical grade plastic.

The circumferential position of the strut46relative to the inlet axis42is chosen to minimize or eliminate static pressure on the strut46which may cause a deflection, vibration, or wobble of the strut46in a radial direction relative to the inlet axis42. With reference toFIG.11, a pressure distribution graph shows a static pressure (in mmHg) at various points of the inlet housing portion14(shown inFIG.3) during pump operation at 5 l/min for various pump rotations per minute (rpm) ranging from 3,500 rpm to 7,500 rpm. Pressure spots A-O in the graph represent various positions on the inlet housing portion14at which measurements were taken, with points A-H measuring the static pressure at positions surrounding the inlet axis42of the inlet20and leading to the outlet22. By plotting the resultant pressure measurements as force vectors around the inlet axis42of the inlet housing14, it can be seen inFIG.12that various circumferential positions on the inner sidewall48of the inlet14are subject to various pressures. Positioning the strut46at a circumferential position about the inlet axis42such that a major axis of the strut46and the outlet axis44define a predetermined angle a in the cross-sectional plane perpendicular to the inlet axis42minimizes or eliminates the net side or radial loads on the strut46which lead to strut vibration or fluttering. In this manner, damage to blood (such as thrombosis of blood) due to strut vibration or fluttering is reduced or eliminated.

With reference toFIGS.6-8, the impeller34has a generally cylindrical shape that corresponds to the shape of the pumping chamber18(shown inFIG.1). The impeller34has a plurality of blades52at an upper end thereof that are configured for pumping blood from the inlet20toward the outlet22. In some examples, the impeller34has six blades52radially spaced apart at equal or unequal angular intervals. The blades52may be identical to each other. In some examples, a first subset52aof blades52may be different from a second subset52bof blades52. The first and second subsets52a,52bof blades52may be arranged in an alternating manner (seeFIG.8). The blades52may be substantially planar. In some examples, the blades52may be curved.

With reference toFIGS.9-10, the impeller34has a hollow central portion54surrounded by an outer shell56. The hollow central portion54is disposed within a hollow interior of the outer shell56. In some examples, the hollow central portion54and the outer shell56may be formed as separate components which are removably or non-removably connected together. A cap58having the blades52is positioned on an upper end of the outer shell56. The cap58encloses at least a portion of the hollow interior of the outer shell56.

With particular reference toFIG.9, the hollow central portion54has at least one passage60that is substantially coaxial with the central longitudinal axis26(shown inFIG.1). The at least one passage60is in fluid communication with the pumping chamber18via one or more openings62on an end piece64at an upper end of the hollow central portion54. The at least one passage60defines a portion of a secondary flow path, as discussed herein. During operation of the blood pump10, the impeller34delivers a first portion of blood flow from the inlet20directly to the outlet22, and delivers a second portion of the blood flow from the inlet20to the outlet22via the at least one passage60and the one or more openings62on the end piece64. In some examples, the at least one passage60is shaped such that its diameter increases in a direction from an upper end to a lower end. In other examples, the at least one passage60may have a uniform diameter throughout its length.

With reference toFIGS.9-10, the impeller34has a first bearing magnet66at a lower end thereof. The first bearing magnet66may be disposed in a first cavity68between the hollow central portion54and the outer shell56. In some examples, the first bearing magnet66engages a lower skirt70that surrounds a central post72of the hollow central portion54. The first bearing magnet66is desirably a permanent magnet. In some examples, the first bearing magnet66has an annular shape comprised from a single, monolithically formed element. In other examples, the first bearing magnet66may be formed from a plurality of discrete magnet segments. For example, the first bearing magnet66may have a plurality of arcuate segments having an equal or unequal angular span. The first bearing magnet66is configured to magnetically interact with a second bearing magnet associated with the pump housing12, as described herein.

With continued reference toFIGS.9-10, the impeller34has a rotor magnet74axially spaced apart from the first bearing magnet66. A spacer80(shown inFIG.9) may be provided to axially separate the first bearing magnet66from the rotor magnet74. In some examples, the spacer80is monolithically formed with the outer shell56. In other examples, the spacer80is removably or non-removably insertable into a hollow interior of the outer shell56.

With continued reference toFIGS.9-10, the rotor magnet74may be disposed in a second cavity76between the hollow central portion54and the outer shell56. In some examples, the rotor magnet74is at least partially supported on a lip78extending radially outward from the central post70of the hollow central portion54. The rotor magnet74is desirably a permanent magnet. In some examples, the rotor magnet74has an annular shape comprised from a plurality of discrete magnet segments. For example, the rotor magnet74may have a plurality of arcuate segments having an equal or unequal angular span. In some examples, the rotor magnet74has four magnet segments each spanning9Cf. The magnet segments may form a continuous shape. In some examples, the magnet segments are separate from each other by predetermined spacing.

With reference toFIG.1, the rotor magnet74is configured to magnetically interact with an electromagnetic coil82associated with the pump housing12to rotatably drive the impeller34within the pump housing12, as described herein. Together, the rotor magnet74and the electromagnetic coil82define the drive mechanism36. The rotor magnet74is desirably positioned radially opposite the electromagnetic coil82such that no net axial force is imparted on the impeller34during pump operation. In some examples, any axial force on the impeller34due to interaction between the rotor magnet74and the electromagnetic coil82may be compensated by the bearing mechanism38, as described herein. The electromagnetic coil82is selectively energized to cause the rotor magnet74to spin and thereby rotate the impeller34about the central longitudinal axis26. Operation of the electromagnetic coil82, such as the current and/or voltage it receives, is controlled by a controller84. The controller84is operative for controlling the speed at which the impeller34is rotated due to interaction between the rotor magnet74and the electromagnetic coil82.

With continued reference toFIG.1, the bearing mechanism38has a radial bearing86having the first bearing magnet66associated with the impeller34and a second bearing magnet88associated with the pump housing12. The first bearing magnet66is coaxial with and magnetically interacts with the second bearing magnet88to radially position the impeller34within the pumping chamber18. In particular, the first and second bearing magnets66,88are configured to provide radial stability to the impeller34so that the impeller34does not contact the sidewall24of the pump housing12during rotation. The second bearing magnet88is desirably a permanent magnet. In some examples, the second bearing magnet88has an annular shape comprised from a single, monolithically formed element. In other examples, the second bearing magnet88may be formed from a plurality of discrete magnet segments. For example, the second bearing magnet88may have a plurality of arcuate segments having an equal or unequal angular span.

In some examples, the first bearing magnet66and the second bearing magnet88are positioned, for example coaxially arranged and axially offset, such that a net axial thrust force urges the impeller34in a direction toward the inlet20. The net axial thrust force may be generated due to an axial offset between the first bearing magnet66and the second bearing magnet88, a difference in magnetic properties, such as magnetic strength, between the first bearing magnet66and the second bearing magnet88, or a combination thereof. In some examples, the axial offset between the first bearing magnet66and the second bearing magnet88may be such that the impeller34is urged in a direction along the central longitudinal axis26toward the inlet20with an axial thrust force of sufficient magnitude to axially support the weight of the impeller34during operation against an axial bearing90, and without the engagement between the components of the axial bearing90which may generate heat of a degree that may lead to excessive heating of the blood (such as above 42° C.) that flows around the axial bearing90that could cause damage to the blood cells.

With continued reference toFIG.1, the axial bearing90is a mechanical bearing that is configured to take up the axial thrust force due to magnetic interaction between the first bearing magnet66and the second bearing magnet88. The axial bearing90has a first bearing element92associated with the impeller34and a second bearing element94associated with the strut46connected to the inlet housing portion14. In some examples, the first bearing element92is ball-shaped and the second bearing element94is cup-shaped to receive at least a portion of the ball-shaped first bearing element92. Alternatively, the second bearing element94is ball-shaped and the first bearing element92is cup-shaped to receive at least a portion of the ball-shaped second bearing element94. The first bearing element92and the second bearing element94are shaped to allow a slight pivoting movement about the axial bearing90to allow for radial centering of the impeller34during pump operation. The axial thrust force generated by the magnetic interaction between the first bearing magnet66and the second bearing magnet88is transferred to the pump housing12by way of the axial bearing90and the strut46.

With reference toFIG.9, the first bearing element92may be a ball supported on a post72connected to the end piece64of the hollow central portion54of the impeller34. in some examples, the first bearing element92is a jewel bearing, such as a ruby ball.

With reference toFIG.5, the second bearing element94may be a cup that is formed at the terminal end50of the strut46. The second bearing element94may be removably or non-removably connected to the terminal end50of the strut46. In some examples, the second bearing element94is made from a ceramic material.

In operation, the rotor magnet74magnetically interacts with an electromagnetic coil82associated with the pump housing12to rotatably drive the impeller34within the pump housing12. Blood flowing through the inlet20flows around the strut46and washes over the axial bearing90, thereby cooling the axial bearing90. As described herein, the strut46is desirably shaped to reduce flow stagnation around the strut46, as well as eliminate fluttering or vibration as the blood flows around the strut46.

As the blood enters the pumping chamber18through the inlet20, the impeller blades52pump the blood in a radially outward direction relative to the inlet axis42to direct a first portion of the blood flow comprising a majority of the blood entering the pumping chamber18toward the outlet22. A second portion of the blood flow passes through a radial gap96between the sidewall24of the pumping chamber12and the outer surface of the cylindrical portion of the impeller34as a secondary fluid path. This secondary flow path allows blood to pass to the bottom98of the pumping chamber12. In some examples, the bottom98of the pumping chamber12may have a deflector100to direct blood flow in the secondary flow path to the at least one passage60. The blood in the secondary flow path then flows axially through the at least one passage60in a direction toward the inlet20to the bottom of the axial bearing90through the one or more openings62on the end piece64of the hollow central portion54of the impeller34. This reduces blood stagnation and incidence of thrombus formation. The blood flow from the secondary flow path then enters the pumping chamber18before exiting the pumping chamber18through the outlet22.

While examples of a rotary blood pump are provided in the foregoing description, those skilled in the art may make modifications and alterations to these examples without departing from the scope and spirit of the disclosure. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The disclosure described hereinabove is defined by the appended claims, and all changes to the disclosure that fall within the meaning and the range of equivalency of the claims are to be embraced within their scope.