ROTARY BLOOD PUMP

[Technical Field]

The present invention relates to a rotary blood pump which is implanted into the patient's body to facilitate ejection of blood from the heart into the aorta, and more particularly, to a rotary blood pump in which an impeller has large-size blades, so as to achieve a sufficient flow rate of blood with a low speed rotation while maintaining a constant efficiency of a motor.

[Background Art]

Generally, a blood pump, which is used as an auxiliary ventricle device, may be classified into a pulsatile flow type and a continuous flow type. Nowadays, a rotary blood pump, of a type producing a continuous flow of blood, has been widely used because the rotary blood pump has an advantage of a smaller size than that of the pulsatile flow type and thus, is easily implanted into the patient's body.

However, in conventional rotary blood pumps, blood is ejected by a rotating impeller and therefore, there is a problem in that damage to blood cells or production of thrombus in a flow stagnation section of blood may be caused depending on the shape of a blood flow pathway defined between the impeller and a pump case as well as a rotating speed of the impeller. Another problem of the conventional rotary blood pumps is in that such damage to blood cells or production of thrombus may be caused due to the use of a hard-contact bearing. To solve these problems, devices, which employ a magnetic bearing for rotating an impeller while preventing the impeller from coming into contact with other structures, have been developed.

FIG. 1 schematically illustrates an example of conventional non-contact type rotary blood pumps as disclosed in U.S. Patents No. 6,527,699 and No. 6,742,999, and so on. The conventional rotary blood pump shown in FIG. 1 is configured in such a manner that an impeller 4 is adapted to rotate, within a case 1, while being magnetically suspended by a permanent magnet 5 and an electromagnet 6. In the above mentioned Patents, the impeller 4 having a rotor 3 is disposed in the center of the case 1 through which blood flows and a stator 2 is installed along an inner periphery of the case 1.

To achieve a desired performance of the rotary blood pump, special regard will be paid to the flow dynamic performance and adaptability of blood and it is necessary to rotate an impeller having large-size blades at a high speed in order to obtain a sufficient flow rate of blood. However, rotating the impeller at the high speed may cause damage to blood cells and result in deterioration in the adaptability of blood. Therefore, the impeller having the large-size blades has to be rotated at a low speed, to fulfill both the flow dynamic performance and adaptability of blood.

Considering the configuration of the blood pumps disclosed in the above mentioned U.S. Patents, blades 7, which are formed at an outer surface of the impeller 4 to produce a flow of blood, have a limit in size by a space between the impeller 4 and the stator 2. A magnetic force between the stator 2 and the rotor 3 is greatly affected by a distance between the stator 2 and the rotor 3. The farther the distance between the stator 2 and the rotor 3, the magnetic force decreases in inverse proportion to square of the distance.

Accordingly, in association with a motor included in the above described conventional rotary blood pump, if the stator 2, which is to rotate the impeller 4 having the rotor 3, is disposed in the case 1 at the outside of the impeller 4, a distance between the impeller 4 and an inner wall surface of the case 1 has a limit required for maintaining production efficiency of a magnetic force between the stator 2 and the rotor 3 beyond a predetermined level. This inevitably results in a reduction in the size of the blades 7 formed at the outer surface of the impeller 4. For this reason, the disclosed conventional rotary blood pumps should be

configured such that the small-size blades 7 are rotated at a high speed in order to increase the operational efficiency of the motor, but such a high speed rotating of the blades 7 may cause damage to blood cells.

Meanwhile, referring to FIG. 2 illustrating another conventional blood pump as disclosed in U.S. Patent No. 6,015,272, the disclosed blood pump is configured in such a manner that an intermediate member 8, which has a curved portion and contains a stator 2 therein, is fixedly disposed in the case 1 and a cylindrical impeller 4 having a curved portion corresponding to that of the curved portion of the intermediate member 8 is inserted around the stator 2 and kept in a magnetically suspended state. Here, the impeller 4 is kept at a constant radial position by a repulsive force produced between permanent magnets 5 that are mounted to a linear portion of the intermediate member 8 and a linear portion of the impeller 4, respectively. Also, the impeller 4 is kept at a constant axial position by a force produced between an electromagnet 6 and a permanent magnet 9 that are mounted to both the curved portions and by a magnetic force between the permanent magnets 5 mounted to both the linear portions.

With the above described configuration, it is allowable that the stator 2 is installed close to the impeller 4 and a distance between the impeller 4 and an inner wall surface of the case 1 increases. Therefore, blades 7, which protrude from an outer surface of the impeller 4, can achieve an increase in size.

As stated above, in the above mentioned Patents, to maintain the radial and axial positions of the impeller 4, the repulsive force between the permanent magnets 5 is used for the radial position and the magnetic force obtained by the electromagnet 6 is used for the axial position. However, to maintain the position of the impeller 4 by regulating the magnetic force obtained by the electromagnet 6, it is necessary to measure positions of the impeller 4 in an axial direction (i.e. y-axis direction) and two radial directions (i.e. x- and z-axes directions). On the basis of the measured position values, magnetic forces in the above three directions should be regulated by coils wound on the electromagnet 6. This configuration has a problem of increasing complexity in the measurement of positions and the control of measurement. Furthermore, there is a problem in

that a highly precise control is necessary to prevent a possible axial deviation of the impeller 4 and a possible contact between the impeller 4 and the case 1 , which may be generated under the absence of stability.

Further, since the blood pump must have a small size suitable for being implanted into the human body, the intermediate member 8 has a limit in size.

However, it is difficult to install the stator 2 and the permanent magnets 5 in the intermediate member 8, having a limited size, at accurate circumferential positions of the intermediate member 8.

[Disclosure] [Technical Problem]

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a rotary blood pump in which an impeller can produce a flow of blood by rotating in a magnetically suspended state without a risk of mechanical contact with other structures, the rotary blood pump being capable of maintaining a constant efficiency of a motor even while providing large-size blades at an outer circumferential surface of the impeller and of producing a sufficient flow rate of blood with a low-speed rotation of the impeller.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a rotary blood pump comprising: a cylindrical case including a cylindrical center portion and truncated conical end portions protruding from opposite sides of the cylindrical center portion, the truncated conical portions having an inlet and an outlet, respectively; a first fixture mounted in the case and including a base portion and an extended portion protruding from the base portion toward the outlet of the case, the base portion having an annular end surface facing the outlet of the case and being connected to an inner wall surface of the case by use of a plurality of fixing blades, the extended portion having a circular column shape with a smaller cross sectional area than that of the base portion; a cylindrical impeller

having an opened annular end surface facing the inlet of the case and a blind end surface facing the outlet of the case, the impeller being rotatably inserted around the extended portion of the first fixture; a blade spirally formed at an outer circumferential surface of the impeller in a longitudinal direction of the impeller; a second fixture spaced apart from the impeller by a predetermined distance, the second fixture having a flat wall surface facing the inlet of the case and being connected to the inner wall surface of the case by use of a plurality of fixing blades; a plurality of magnetic bearings, respectively, disposed between the outlet-side annular end surface of the base portion and the inlet-side annular end surface of the impeller and between the inlet-side wall surface of the second fixture and the outlet-side blind end surface of the impeller, the magnetic bearings being adapted to apply an axial magnetic force to the impeller, so as to achieve a magnetic suspension of the impeller while maintaining the impeller at predetermined axial and radial positions between the first fixture and the second fixture; and a motor including a stator disposed in the extended portion of the first fixture and a rotor disposed in the impeller, the motor being used to rotate the impeller about the circular column shaped extended portion of the first fixture

The outlet-side blind end surface of the impeller may be perforated with a center hole to allow blood introduced between the extended portion of the first fixture and the impeller to flow between the inlet and the outlet.

The impeller may have spiral protrusions or grooves formed longitudinally at an inner circumferential surface of the impeller to guide the delivery of the introduced blood easily. The first fixture may have spiral protrusions or grooves formed longitudinally at an outer circumferential surface of the extended portion to guide the delivery of the introduced blood easily.

A hall sensor may be installed to an outer circumferential surface of the extended portion of the first fixture and used to sense a rotating speed of the impeller.

A gap sensor may be installed to the inlet-side wall surface of the

second fixture and used to sense a distance between the second fixture and the impeller.

The magnetic bearings may comprise: an electromagnet containing a permanent magnet, which is installed to any one of the outlet-side annular end surface of the base portion and the inlet-side wall surface of the second fixture: and a permanent magnet and a ferromagnetic material installed to each of the other one of the outlet-side annular end surface and the inlet-side wall surface and the inlet-side annular end surface and the outlet-side blind end surface of the impeller. The magnetic bearings may comprise: an electromagnet containing a permanent magnet installed to each of the outlet-side annular end surface of the base portion and the inlet-side wall surface of the second fixture: and a permanent magnet and a ferromagnetic material installed to each of the inlet- side annular end surface and the outlet-side blind end surface of the impeller. A pressure sensor and a flow sensor may be installed to a side of the outlet of the case and used to predict flow dynamic performance of blood in the blood pump, so as to regulate an ejection rate of blood by regulating the rotating speed of the impeller.

[Description of the Drawings]

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a sectional view illustrating a conventional rotary blood pump;

FIG. 2 is a sectional view illustrating another conventional rotary blood pump;

FIG. 3 is a sectional view illustrating a rotary blood pump according to an exemplary embodiment of the present invention;

FIG. 4 is a partial sectional view illustrating, in enlarged scale, a magnetic bearing part according to the exemplary embodiment of the present

invention;

FIG. 5 is a perspective view illustrating a first fixture according to the exemplary embodiment of the present invention;

FIG. 6 is a perspective view illustrating an impeller according to the exemplary embodiment of the present invention;

FIG. 7 is a perspective view illustrating a second fixture according to the exemplary embodiment of the present invention;

FIG. 8 is a perspective view illustrating a coupled state of the first fixture, impeller, and second fixture according to the exemplary embodiment of the present invention; and

FIGS. 9 A to 9C are graphs illustrating experimental results of the rotating speed of the impeller and the delivery rate of blood depending on the size of a blade, FIG. 9A pertaining to a blade having a height of 2mm, FIG. 9B pertaining to a blade having a height of 3mm, and FIG. 9C pertaining to a blade having a height of 4mm.

[Best Mode]

Now, a rotary blood pump according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 is a sectional view illustrating the internal configuration of the rotary blood pump according to the exemplary embodiment of the present invention, and FIG. 4 is a partial sectional view illustrating, in enlarged scale, a magnetic bearing part shown in FIG. 3.

As shown in FIG. 3, the rotary blood pump of the present invention comprises a cylindrical case 10, first and second fixtures 20 and 40 fixedly mounted in the cylindrical case 10, an impeller 30 inserted around an extended portion 22 of the first fixture 20, a motor 50 used to rotate the impeller 30 about the extended portion 22 of the first fixture 20, magnetic bearings 60 used to magnetically suspend the impeller 30 so as to maintain the impeller 30 at

predetermined axial and radial positions, and a gap sensor 70 used to sense a gap between the impeller 30 and the second fixture 40. In operation of the rotary blood pump having the above described configuration, the impeller 30 is magnetically suspended and rotated within the case 10 and blood is ejected from the entrance side to the exit side of the blood pump by rotation of the impeller 30.

In the present invention, the first fixture 20 is located in the case 10 near the entrance side of the case 10 to define a blood introduction path, and the second fixture 40 is located in the case 10 near the exit side of the case 10 to define a blood discharge path. The impeller 30 is located between the two fixtures 20 and 40. The impeller 30 has a plurality of blades 31 formed at an outer circumferential surface of a cylindrical body and serves to push blood toward an outlet of the case 10 while rotating in the case 10.

Hereinafter, detailed configurations of the rotary blood pump according to the exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the case 10 includes a cylindrical body portion and truncated conical end portions protruding from the cylindrical body portion to have a gradually decreasing cross sectional area away from the cylindrical body portion. Both the truncated conical end portions of the case 10 are formed with a blood inlet 11 and a blood outlet 12, respectively.

FIG. 5 is a perspective view illustrating the first fixture 20 according to the exemplary embodiment of the present invention. The first fixture 20 is mounted in the case 10 near the inlet 11 of the case 10, and includes a streamline base portion 21 and the extended portion 22. The first fixture 20 is oriented such that the streamline base portion 21 faces the inlet 11. This is to reduce flow resistance of blood being introduced into the case 10. The first fixture 20 further includes a plurality of fixing blades 23 formed longitudinally at an outer surface of the base portion 21. The fixing blades 23 are connected to an inner wall surface 13 of the case 10. Although the base portion 21 having a streamline wall surface facing the inlet 11 of the case 10 is illustrated, it will be appreciated that the wall surface of the base portion 21 may have a conical

shape.

The plurality of fixing blades 23 serve not only to fixedly secure the first fixture 20 to the case 10, but also to guide the blood introduced between the case 10 and the base portion 21 of the first fixture 20 toward the outlet 12 of the case 10. The extended portion 22 takes the form of a circular column protruding longitudinally from an end surface of the base portion 21 facing the outlet 12 of the case 10. The extended portion 22 has a smaller cross sectional area than that of the base portion 21. A stator 51 is disposed in the extended portion 22 of the first fixture 20, to constitute a part of the motor 50. FIG. 6 is a perspective view illustrating the impeller 30 according to the exemplary embodiment of the present invention. Now, the configuration of the impeller 30 will be described with reference to the drawing.

The cylindrical impeller 30 has an opened annular end surface 32 and a blind end surface 33. The extended portion 22 of the first fixture 20 is inserted into the impeller 30 through the opened end surface 32. A permanent magnet 52 is mounted at an inner circumferential surface of the impeller 30 facing the extended portion 22 and serves as a rotor of the motor 50. With this configuration, the impeller 30 is rotatable about the extended portion 22 of the first fixture 20. The impeller 30 has the plurality of spiral blades 31 arranged, in a longitudinal direction, at the outer circumferential surface of the impeller 30. If blood is introduced into the case 10 through the inlet 11, the blood is able to be forcibly delivered toward the outlet 12 under operation of the blades 31 of the rotating impeller 30. Most of the blood, which was introduced through the inlet 11 of the case 10, first passes through a space defined between the case 10 and the fixing blades 23 of the first fixture 20 and then, is delivered toward the outlet 12 through a space defined between the case 10 and the blades 31 formed at the outer circumferential surface of the impeller 30. In this case, to allow a slight amount of the blood to flow between the inlet 11 and the outlet 12 of the case 10 through a gap 24 that is defined between the first fixture 20 and the inner

circumferential surface of the impeller 30, the impeller 30 may have a center hole 35 perforated through the blind end surface 33 of the impeller 30 facing the outlet 12.

To facilitate the delivery of the slight amount of the blood that flows through the gap 24 between the extended portion 22 of the first fixture 20 and the inner circumferential surface of the impeller 30, the inner circumferential surface of the impeller 30 may have spiral protrusions or grooves formed in a longitudinal direction of the impeller 30. Thereby, once the blood is introduced into the gap 24, the blood is able to be delivered easily without a risk of stagnation.

Alternatively, the spiral protrusions or grooves may be formed longitudinally at an outer circumferential surface of the extended portion 22 of the first fixture 20, to guide efficiently the blood introduced into the gap 24.

Although the protrusions or grooves are not illustrated in the drawings, those skilled in the art will appreciate easily the shape of the protrusions or grooves as well as their detailed formation relative to the impeller 30 or the extended portion 22.

FIG. 7 is a perspective view illustrating the second fixture 40 according to the exemplary embodiment of the present invention. Now, the configuration of the second fixture 40 will be described with reference to the drawing.

The second fixture 40 is separated from the first fixture 20 and has a flat end surface facing the inlet 11 of the case 10. The end surface 33 of the impeller 30 is interposed between the first fixture 20 and the second fixture 40 by predetermined distances. The second fixture 40 has a plurality of fixing blades 41 formed longitudinally at an outer surface of the second fixture 40. The second fixture 40 is fixedly secured to the inner wall surface 13 of the case 10 by the fixing blades 41. Accordingly, the fixing blades 41 serve not only to fixedly secure the second fixture 40 to the case 10, but also to guide the blood introduced from the space between the case 10 and the base portion 21 toward the outlet 12. A wall surface of the second fixture 40 facing the outlet 12 of the case 10 conically protrudes toward the outlet 12, in order to reduce flow

resistance of the blood to be discharged through the outlet 12. Although the drawing illustrates the conical wall surface, the wall surface of the second fixture 40 may have a streamline shape.

The above described first fixture 20, impeller 30, and second fixture 40 are disposed within the case 10 such that they are coupled with one another. FIG. 8 is a perspective view illustrating a coupled state of the first fixture 20, impeller 30, and second fixture 40.

In the rotary blood pump of the present invention having the above described configuration, flow paths are defined by the first and second fixtures 20 and 40, the case 10, and the blades 23, 31, and 41. Accordingly, if blood is introduced from one end of the blood pump, the blood first passes through a flow path between the first fixture 20 and the inner wall surface 13 of the case 10 and is pushed toward the outlet 12 via rotation of the impeller 30. Then, the blood passes through a flow path defined between the second fixture 40 and the inner wall surface 13 of the case 10, so as to be ejected out of the blood pump through the outlet 12. In the present invention, a part of the blood is able to pass through a flow path, i.e. a gap between the outer circumferential surface of the extended portion 22 of the first fixture 20 and the impeller 30. If the gap has an excessively large width, a distance between the permanent magnet 52 in the impeller 30 and the stator 51 in the extended portion 22 of the first fixture 20 increases, and this may cause a reduction in the rotation torque of the impeller 30 and a degradation in the efficiency of a motor system. Conversely, if the gap has an excessively small width, a width of a blood passage decreases, and this may produce thrombosis due to blood stasis. Accordingly, it is important to regulate the gap to have an optimal width. For this, as stated above, it is preferable that the inner circumferential surface of the impeller 30 or the outer circumferential surface of the extended portion 22 of the first fixture 20 be provided with protrusions or grooves, to facilitate more efficient delivery of blood through the flow path between the impeller 30 and the extended portion 22 of the first fixture 20 during rotation of the impeller 30.

Next, the magnetic bearings 60 according to the exemplary embodiment

of the present invention will be described with reference to FIGS. 3 and 4.

The magnetic bearings 60 include electromagnets 61 and 62 containing permanent magnets, respectively, installed in the base portion 21 of the first fixture 20 and in the second fixture 40, and permanent magnets 63 and 64, respectively, installed to the inlet-side end surface 32 and the outlet-side end surface 33 of the impeller 30. Coils 65 and 66 are wound around the electromagnets 61 and 62 that are axially installed in the first and second fixtures 20 and 40, such that a magnetic attraction between the electromagnets 61 and 62 and the permanent magnets 63 and 64 installed to both the end surfaces 32 and 33 of the impeller 30 can be regulated by regulating the amount of electric current flowing through the coils 65 and 66. The magnetic attraction acts on both the first fixture 20 and the second fixture 40. Therefore, if the magnetic attraction acting on the first fixture 20 keeps a balance with the magnetic attraction acting on the second fixture 40, the impeller 30 is able to be kept in a magnetically suspended state while maintaining a predetermined position thereof.

Specifically, the present invention employs active axial magnetic bearings for achieving the magnetic suspension of the impeller 30. Both the end surfaces 32 and 33 of the impeller 30 contain ferromagnetic materials as well as the permanent magnets 63 and 64, and both the first and second fixtures 20 and 40 adjacent to the impeller 30 contain the electromagnets 61 and 62 including permanent magnets. Thereby, the impeller 30 is able to be kept at a fixed position by regulating an axial attractive force or repulsive force with the first and second fixtures 20 and 40. The magnetic bearings 60, as shown in the drawings, include electromagnets containing permanent magnets, which are installed to an outlet- side annular end surface 26 of the base portion 21 and an inlet-side wall surface 42 of the second fixture 40, and permanent magnets and ferromagnetic materials which are installed to the inlet-side annular end surface 32 and the outlet-side end surface 33 of the impeller 30.

Differently from the illustration of the drawings, alternatively, the

magnetic bearings 60 may include an electromagnet containing a permanent magnet installed to any one of the outlet-side annular end surface 26 of the base portion 21 and the inlet-side wall surface 42 of the second fixture 40. In this case, the other one of the outlet-side annular end surface 26 and the inlet-side wall surface 42 may be provided with a permanent magnet and a ferromagnetic material, along with the inlet-side annular end surface 32 and the outlet-side end surface 33 of the impeller 30.

If the impeller 30 is magnetically suspended by the magnetic attraction acting on opposite sides of the impeller 30, the impeller 30 can be continuously kept at predetermined axial and radial positions. That is to say, the impeller 30 can achieve a magnetic suspension while maintaining the predetermined axial and radial positions thereof, so as to push the blood while being rotated in the magnetically suspended state via operation of the motor.

The magnetic bearings 60 for keeping the impeller 30 at a fixed axial position is active axial magnetic bearings suitable for actively regulating a magnetic force using the electric coils 65 and 66. As the magnetic bearings 60 axially apply a magnetic attraction to the impeller 30 that is interposed between the first fixture 20 and the second fixture 40 from opposite sides of the impeller 30, the impeller 30 is also able to be passively kept at a fixed radial position. Keeping the impeller 30 at a fixed radial position is accomplished by use of a passive radial positioning force exhibited by the active axial magnetic bearings.

Accordingly, the impeller 30 can be continuously kept at a fixed position without a risk of, for example, failing to be kept at a predetermined position and easily deviating from its magnetic suspension position by an external shock under an unstable state of the impeller 30.

As shown in FIG. 3, the gap sensor 70 may be installed to a wall surface of the second fixture 40 facing the impeller 30. The gap sensor 70 serves to sense a distance between the impeller 30 and the second fixture 40. Accordingly, if the impeller 30 deviates from a predetermined position thereof, the gap sensor 70 senses the positional deviation of the impeller 30. Then, in response to a signal from the gap sensor 70, a controller increases the amount of

current to be applied to the electric coils 65 and 66 provided in the first and second fixtures 20 and 40, so as to regulate the magnetic attraction obtained by the electromagnets 61 and 62. With the regulation of the magnetic attraction, the impeller 30 is operated to be returned to its predetermined position. The gap sensor 70 is a non-contact type distance sensor for measuring a distance between the impeller 30 and the second fixture 40. The gap sensor 70 may be any one selected from among an eddy current gap sensor, an ultrasonic gap sensor, an infrared optic gap sensor, an inductive sensor, and so on. In addition, the above mentioned controller may be embodied by use of a general circuit that can be easily built by those skilled in the art.

Now, the motor 50 will be described with reference to FIG. 3. The motor 50 includes the stator 51 mounted in the extended portion 22 of the first fixture 20 and the rotor 52 mounted in the impeller 30. The stator 51 in the extended portion 22 has a circular column shape and the rotor 52 is a cylindrical permanent magnet mounted at the inner circumferential surface of the impeller 30. If power is applied to a terminal 53 of the stator 51 to operate the stator 51, the impeller 30 containing the permanent magnet 52 therein is rotated about the extended portion 22 of the first fixture 20, thereby allowing the blood, which was introduced into the case 10 through the inlet 11, to be delivered toward the outlet 12 by operation of the blades 31 of the impeller 30.

Meanwhile, as shown in FIG. 3, a hall sensor 25 may be mounted at a certain position of the outer circumferential surface of the extended portion 22 and serves to sense a rotating speed of the impeller 30. The rotating speed of the impeller 30 can be appropriately controlled by the controller that is not shown in the drawings. The hall sensor 25 may be a generally used one, and the controller may be easily built by use of a control circuit that is generally used by those skilled in the art.

Although not shown in the drawings, the controller is provided at the outside of the impeller 30 for the sake of the magnetic suspension and rotation of the impeller 30. The controller serves to regulate a variety of factors, for example, the amount of current to be applied to the stator 51 that is mounted in

the extended portion 22 of the first fixture 20, a rotating speed of the motor 50 on the basis of the result sensed by the hall sensor 25, and the amount of current to be applied to the electromagnets 61 and 62 mounted in the first and second fixtures 20 and 40. Thereby, the controller performs a feedback control for allowing the impeller 30 to be rotated at a predetermined position by an appropriate rotating speed required to deliver a desired amount of blood. The controller having the above described operation can be easily built by use of a control circuit that is generally used by those skilled in the art.

In the rotary blood pump of the present invention having the above described configuration, the stator 51 and the rotor 52 of the motor 50 may be arranged close to each other with a predetermined distance therebetween, and the blades 31 of the impeller 30 have a size determined on the basis of the size of a space between the impeller 30 and an inner wall surface 13 of the case 10. Accordingly, differently from a conventional pump in that the blades 31 are installed between the stator 51 and the rotor 52, the rotary blood pump of the present invention has no restriction in relation with the size of the blades 31.

FIGS. 9 A to 9C are graphs illustrating experimentally measured values related to the rotating speed and blood delivery rate of the impeller 30 depending on the size of the blades 31. The rotating speed and blood delivery rate of the impeller 30 are important to obtain a desired pressure of blood. As shown in the graphs, the rotating speed of the impeller 30 decreases according to the size of the blades 31 under the condition of the same delivery rate of blood. Specifically, assuming that the ejection rate of blood is 5L/min on the basis of a pressure difference between an inlet pressure and an outlet pressure of the blood of approximately lOOmmHg that corresponds to the blood pressure in the aorta, the rotating speed of the impeller 30 is approximately 6700 RPM when the height of the blades 31 is 2mm (FIG. 9A), is approximately 5400 RPM when the height of the blades 31 is 3mm (FIG. 9B), and is approximately 4800 RPM when the height of the blades 31 is 4mm (FIG. 9C). That is to say, it will be appreciated that the greater the size of the blades 31, the lower the rotating speed of the impeller 30 on the basis of a constant blood flow.

As can be revealed from the above experimental results, with the rotary blood pump of the present invention, the blades 31 can be fabricated to have a sufficient large size such that the blades 31 can efficiently perform ejection of blood even while being rotated at a low speed for the sake of preventing damage to blood cells.

In the rotary blood pump having the above described configuration, additionally, a pressure sensor 14 and a flow sensor 15 for measuring a pressure and a flow rate of blood are provided at a side of the outlet 12. Thereby, the rotary blood pump has functions of predicting flow dynamic performance of blood passing through the blood pump and regulating the rotating speed of the impeller 30 and consequently, the ejection rate of blood.

[Industrial Applicability]

As apparent from the above description, the present invention provides a rotary blood pump, which is implanted into the patient's body and adapted to produce a sufficient flow rate of blood with low speed rotation of an impeller, thereby being capable of ejecting blood from the heart into the aorta.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.