Pulsatile Fluid Pump System

Abstract

A pulsatile fluid pump system includes a pump-valving assembly including a chamber and a diaphragm assembly coupled to the chamber and including a flexible diaphragm. The diaphragm assembly and the pump-valving assembly are configured as an integral pump assembly. The system further includes a linear motor having a magnet and a coil, the magnet moving in relation to the coil, the coil having an electrical input. The system also includes a control housing rigidly coupled to the linear motor and a controller system having an electrical output coupled to the electrical input of the coil, the controller system defining an electrical waveform at the electrical output to cause desired operation of the diaphragm. The integral pump assembly is configured to be removably coupled to the control housing, and the diaphragm assembly of the integral pump assembly is configured to be removably coupled to the linear motor.

Claims

1. A pulsatile fluid pump system comprising: a pump-valving assembly including a chamber and a set of ports; a diaphragm assembly coupled to the chamber and including an edge-mounted flexible diaphragm; wherein the diaphragm assembly and the pump-valving assembly are configured as an integral pump assembly surrounded by a flange having a pair of opposed sides; a control housing configured to removably and slideably couple to the integral pump assembly, the control housing including: a channel having a pair of opposed sides configured to receive the flange when the control housing is slideably coupled to the integral pump assembly, and to prevent rotation of the diaphragm assembly while the control housing is coupled to the integral pump assembly; a push rod configured to removably and slideably couple to the diaphragm assembly when the control housing is slideably coupled to the integral pump assembly; a motor coupled to the push rod and configured to reciprocate the push rod in an axial direction; and a controller system electrically coupled to the linear motor and configured to cause a desired operation of the motor.

2. The pulsatile fluid pump assembly of claim 1, wherein the diaphragm assembly further comprises a coupler having a slot configured to slideably receive a head and an upper portion of the push rod.

3. The pulsatile fluid pump assembly of claim 2, wherein the integral pump assembly includes a pump housing having a neck in which the coupler reciprocates.

4. The pulsatile fluid pump assembly of claim 3 wherein the neck is configured to maintain axial and rotational alignment of the coupler.

5. The pulsatile fluid pump assembly of claim 1, wherein the set of ports includes an inlet ball check valve and an outlet ball check valve.

6. The pulsatile fluid pump assembly of claim 1, wherein the edge-mounted diaphragm comprises three layers.

7. The pulsatile fluid pump assembly of claim 1, wherein the pump-valving assembly is preload sensitive and afterload sensitive.

8. The pulsatile fluid pump assembly of claim 1, wherein at least one of the flange and the channel has a set of compliant members to physically bias the flange in the control housing.

9. The pulsatile fluid pump assembly of claim 8, wherein each compliant member includes a spring.

10. The pulsatile fluid pump assembly of claim 9, wherein the set of compliant members includes a set of ball detents.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0018] FIG. 1 is a vertical section of the pulsatile fluid pump system 301 showing the controller system 311, power amplifier 321, linear motor 330 (coil 332, cooling fins 334, and magnet 339), push rod assembly 341, flexible seal 351, control housing 361, and the integral pump assembly 200.

[0019] FIG. 2 is an example of the touch-sensitive graphic display 400 user interface showing the user-specifiable motor parameters 401, flow characteristics 411, and user-specifiable input parameters 421.

[0020] FIG. 3 is a vertical section of the push rod assembly 341.

[0021] FIG. 4 is a vertical section of the linear motor 330.

[0022] FIG. 5 is a block diagram describing a waveform program 511.

[0023] FIG. 6 is a block diagram describing a first embodiment 511a of the waveform program 511.

[0024] FIG. 7 is a block diagram describing a second embodiment 511b of the waveform program 511.

[0025] FIG. 8 is a block diagram describing a graphics program 611.

[0026] FIG. 9 is a horizontal section of a pump-valving assembly 101 in accordance with an embodiment of the present invention, wherein the pump-valving assembly 101 is in diastole mode in which the chamber 102 is being filled.

[0027] FIG. 10 is a vertical section of an integral pump assembly 200 showing a diaphragm assembly 201 mounted to a pump-valving assembly 101 in diastole mode, in which the chamber 102 is being filled.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0028] Definitions. As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires:

[0029] A set includes at least one member.

[0030] An electrical waveform is a waveform selected from the group consisting of an electrical current waveform, a voltage waveform, and combinations thereof.

[0031] The term user-specifiable input parameter includes a user-definable attribute pertinent to an alarm setting or calculation for a user interface, such as low flow limit 421a, high flow limit 421b, and body surface area 421c (BSA), as well as combinations of any of the foregoing attributes.

[0032] The term user-specifiable parameter defining the performance of the linear motor in the course of pumping includes a motor performance attribute such as stroke strength 401a, beat rate 401b, flow rate, average flow rate, stroke volume, flow index, pulse pressure, output pressure, magnet displacement, as well as combinations of any of the foregoing attributes.

[0033] The term physical flow characteristic includes a measured attribute such as stroke strength, beat rate, flow rate, average flow rate 411a, stroke volume 411b, flow index 411c, flow rate waveform 412, stroke volume waveform 413, duration over which the pump has been running (e.g., measured by timer 414), as well as combinations of any of the foregoing attributes. If an attribute is user-specified in a given embodiment of the present invention, then measurement of the attribute is of subsidiary importance since its value has been specified. Similarly, if an attribute being measured has primary importance a given embodiment of the present invention, then the parameter would not have been user-specified.

[0034] Normal flow is flow from the entrance to the inlet port 111 through the chamber 102 to the exit of the outlet port 121.

[0035] A slight reversal of flow past a ball in a ball check valve is a small, controlled amount of desired reverse flow past the ball before the ball is seated in a closed position.

[0036] Diastole mode is a phase of operation of a pulsatile pump, according to embodiments of the present invention, during which the diaphragm 202 of the pump-valving assembly 200 is pulled away from the chamber 102 so as to create negative pressure within the chamber 102, inlet ball check valve assembly 110, and third tapered tract 126, but not the fourth tapered tract 122.

[0037] Systole mode is a phase of operation of a pulsatile pump, according to embodiments of the present invention, during which the diaphragm 202 of the pump-valving assembly 200 is pushed towards the chamber 102, so as to create positive pressure within the chamber 102, outlet ball check valve assembly 120, and the second tapered tract 116, but not the first tapered tract 112.

[0038] FIG. 1 is a vertical section of the pulsatile fluid pump system 301 showing the controller system 311 (with electrical output 311b), power amplifier 321 (with electrical input 321a and electrical output 321b), linear motor 330 (comprised of a stationary member 331 which includes a coil 332 [with electrical input 332a], a frame 333, and cooling fins 334, and a moving member which includes a spring 338 of FIG. 4 and a magnet 339), position sensor 371, push rod assembly 341 (comprised of a push rod 342 and force sensor 372), flexible seal 351, control housing 361, and chassis 363. An integral pump assembly 200 (comprised of the pump-valving assembly 101 with chamber 102, diaphragm assembly 201, and peripheral flange 221a) is configured to be removably coupled to the control housing 361, and the diaphragm assembly 201 of the integral pump assembly 200 is configured to be removably coupled to the linear motor 330. The integral pump assembly 200 has a flange 221a that slides in the channel 362. The integral pump assembly 200 is held in place by the peripheral flange 221a and compliant member 221c of FIG. 10 in the channel 362 within the control housing 361. (In these figures, like numbered items correspond to similar components across different figures.)

[0039] FIG. 2 is an example of a touch-sensitive graphic display 400 user interface showing user-specifiable motor parameters 401. In this interface appear parameters stroke strength 401a and beat rate 401b. These parameters are a subset of user-specifiable parameters defining the performance of the linear motor. Additionally, in this interface appear flow characteristics 411 (average flow rate 411a, stroke volume 411b, flow index 411c), flow rate waveform 412, stroke volume waveform 413, and timer 414. These flow-based attributes are a subset of physical flow characteristics. Additionally, the interface displays user-specifiable inputs 421 (low flow limit 421a, high flow limit 421b, and body surface area 421c).

[0040] FIG. 3 is a vertical section of the push rod assembly 341 comprised of the push rod 342 and force sensor 372.

[0041] FIG. 4 is a vertical section of the linear motor 330, showing the coil 332 with electrical input 332a, the frame 333, the magnet centering spring 338, and the magnet 339. Other components and detail of the motor are provided in FIG. 1.

[0042] In FIG. 5, the waveform program 511 is a computer program executed by the controller system 311 microprocessor 311c which accepts input from a set of sensors 370 (including position sensor 371 of FIG. 1, force sensor 372 of FIGS. 1 and 3, and an external flow sensor 373 of FIG. 8), a set of user-specifiable motor parameters 401 (stroke strength 401a and beat rate 401b) defining performance of a linear motor 330 in the course of pumping. Additionally, FIG. 5 shows a set of user-specifiable input parameters 421 (low flow limit 421a, high flow limit 421b, and body surface area 421c). The waveform program 511 outputs an electrical waveform 512, the result of a set of algorithms 513, at the electrical output 311b. The electrical output 311b is coupled to electrical input 332a of linear motor 330.

[0043] There is growing consensus that desirable characteristics of a pulsatile pump should include both sufficient hemodynamic energy and a human-like waveform architecture. To evaluate pulsatile flow, we choose the human heart as the best model: it delivers a proper stroke volume at a natural cadence with a physiologic rest at the end of each stroke, adapting to the physiologic demands of the patient by adjusting the cardiac output, as the product of stroke volume and beat rate. Via the left ventricle, the human heart provides hemodynamic energy that results in a pressure wave that propagates fully through the elastic arterial tree. It appears that only a biomimetic stroke volume delivered in a biomimetic time frame (like the native systolic contraction produced by the heart) allows the clastic arterial tree to properly relax during the diastolic phase. Use of continuous flow devices stretches the elastic arterial wall but never allows proper relaxation, creating constant and atypical stress on the endothelial cells and interfering with natural baroreceptor sympathetic and parasympathetic signaling, thus disrupting the body's homeostatic control state.

[0044] The waveform program 511 causes the pulsatile fluid pump system 301 to replicate the ability of the left ventricle of the human heart to deliver physiological hemodynamic energy proportional to a user-specified stroke strength 401a by causing delivery of the necessary fraction of the stroke volume of a pump chamber 102 in a physiologic natural cadence at a user-specified beat rate 401b. It is a user (a perfusionist) of the pulsatile fluid pump system 301 who adjusts the stroke strength 401a (an indirect specification of stroke volume) and beat rate 401b to meet the physiologic demand of the patient. Furthermore, the waveform program 511 replicates the physiologic rest at the end of each stroke, thereby allowing natural relaxation of the arterial tree.

[0045] The structure of a pulsatile pump in accordance with various embodiments of the present invention can usefully reflect attributes of the human heart. The human heart is preload sensitivethe heart cannot pull blood into the left ventricle; it can only allow the blood available to flow naturally into the ventricle. The human heart is also afterload sensitive in that it is responsive to the compliance and resistance in the downstream vasculature and doesn't exert excess force on the blood, which could damage the vasculature. Lastly, the left ventricle cannot deliver blood that isn't in the ventricle when it contracts; there is a limited bolus of blood that it can deliver.

[0046] Similarly, the pulsatile fluid pump system 301 has similar attributes of inherent safety: it is preload and afterload sensitive, and it is limited in both the volume of blood it can deliver and the force at which it can deliver that bolus of blood. When filling, the pulsatile fluid pump system 301 allows gravity filling from the venous reservoir, exerting minimal negative pressure. When emptying, the linear motor 330 is inherently limited in the force that it can generate by its design. As such, it cannot overpressure the downstream tubing or vasculature, instead delivering less than the volume of blood in the pump chamber 102, thereby only delivering as much volume as the vasculature can receive.

[0047] The integral pump assembly 200 is analogous to a left ventricle of the human heart; the inlet ball check valve assembly 110 used in various embodiments hereof is analogous to a mitral valve; and the outlet ball check valve assembly 120 used in various embodiments hereto is analogous to an aortic valve. Like the human heart, the inlet 110 and outlet 120 ball check valve assemblies are passive and require a slight reversal of flow to close. This slight reversal of flow mimics the slight reversal that occurs when the aortic valve of the human heart closes.

[0048] In one embodiment, of the present invention, show in FIG. 6, a waveform program 511a is a computer program executed by the controller system 311 microprocessor 311c which accepts input from a set of sensors 370, a set of user-specifiable motor parameters 401, and a set of user-specifiable input parameters 421. The waveform program 511a is configured to simulate a waveform that has been experimentally determined to be appropriate for embodiments of the pulsatile fluid pump system 301 of the present invention. The waveform program 511a simulates the experimentally determined waveform by repeatedly performing a multi-piece polynomial spline algorithm 513a and the resulting waveform is used to drive the linear motor 330. In the event that the user changes one of the user-specifiable motor parameters 401, the waveform program 511a uses zero or more of the current and/or previous values from the set of sensors 370, along with the set of user-specifiable motor parameters 401, zero or more flow characteristics 411, zero or more user-specifiable input parameters 421, and the current electrical waveform 512a to create a new electrical waveform 512b. The waveform program 511a outputs the new electrical waveform 512b, consisting of discrete output voltages at defined time durations, at the electrical output 311b. The electrical output 311b is coupled to electrical input 332a of linear motor 330.

[0049] In another embodiment of the present invention, shown in FIG. 7, the waveform program 511b is a computer program executed by the controller system 311 microprocessor 311c which accepts input from a set of sensors 370, a set of user-specifiable motor parameters 401, and a set of user-specifiable input parameters 421. The waveform program 511b reads a prototype electrical waveform 512c stored electronically within the controller system 311. The waveform program 511b then uses an algorithm 513b to adjust the archetype electrical waveform 512c. The algorithm 513b creates a new waveform 512b from the archetype electrical waveform 512c using zero or more of the current and/or previous values of the set of sensors 370, along with the set of user-specifiable motor parameters 401, zero or more flow characteristics 411, zero or more user-specifiable input parameters 421, and the current electrical waveform 512a. The waveform program 511b outputs the new electrical waveform 512b, consisting of discrete output voltages at defined time durations, at the electrical output 311b. The electrical output 311b is coupled to electrical input 332a of linear motor 330.

[0050] In FIG. 8, the graphics program 611 is a computer program executed by the controller system 311, which accepts user-specifiable motor parameters 401 and user-specifiable input parameters 421. The graphics program 611 causes a set of current values of the user-specifiable motor parameters 401, a set of flow characteristics 411, and a set of user-specifiable input parameters 421 to be shown on the graphic display 400.

[0051] The operation of the waveform programs 511, graphics program 611, and graphic display 400 is discussed in further detail in the related application, referenced above, bearing attorney docket number 4747/1003.

[0052] FIG. 9 is a horizontal section of a pump-valving assembly 101 in accordance with an embodiment of the present invention, wherein the pump-valving assembly 101 is in diastole mode in which the chamber 102 is being filled. Fluid flows into the inlet port 111, through the first tapered tract 112, past the inlet ball 114, as that inlet ball 114 engages against the inlet ribs 115 that create gaps between the inlet ball 114 and the second tapered tract 116 that allow fluid to flow into the second tapered tract 116 and then into the chamber 102. The pump-valving assembly 101 operates in cooperation with an edge mount 202a diaphragm 202 that seats around the circumference of the chamber 102. The motion of the diaphragm in cooperation with the inlet ball check valve assembly 110 and the outlet ball check valve assembly 120 causes the flow of fluid into the chamber 102. While the chamber 102 is filling, the outlet ball 124 in the outlet ball check valve assembly 120 settles against the outlet seat 123 to prevent fluid flow from the outlet port 121 back into the chamber 102. The fluidic flywheel 103 is illustrated. The pump-valving assembly 101 is discussed in further detail in the related application, referenced above, bearing attorney docket number 4747/1001.

[0053] FIG. 10 is a vertical section of an integral pump assembly 200 showing a diaphragm assembly 201 mounted to a pump-valving assembly 101 in diastole mode, in which the chamber 102 is being filled. The edge mount 202a diaphragm 202 of the diaphragm assembly 201 is flexible and mounted at the edge of the chamber 102 of the pump valving assembly 101. The diaphragm 202 has an inside surface 202b for contacting a fluid in the chamber 102 to be pumped and an outside surface 202d exposed to ambient air. The integral pump assembly 200 includes a pump housing 221 including a neck 221b in which the coupler 214 reciprocates as the diaphragm 202 reciprocates. The neck 221b is configured to maintain axial alignment of the coupler 214 and (via physical features, such as flattened sides) is also configured to maintain rotational alignment of the coupler 214. The pump-valving assembly 101 is discussed in further detail in the related application, referenced above, bearing attorney docket number 4747/1001. As the diaphragm 202 is pulled down, in a diastole mode (in a direction away from the chamber 102), to cause filling of the chamber 102, it creates a negative pressure that draws fluid into the chamber 102 through the inlet port 111. Similarly, as the diaphragm 202 is pushed up, in a systole mode (in a direction into the chamber 102), it creates a positive pressure that causes flow of the fluid out of the chamber 102 through the outlet port 121. The integral pump assembly 200 is discussed in further detail in the related application, referenced above, bearing attorney docket number 4747/1002.

[0054] The embodiments of the invention described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims.