WO2012100210A1 - Flow estimation in a blood pump - Google Patents
Flow estimation in a blood pump Download PDFInfo
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- WO2012100210A1 WO2012100210A1 PCT/US2012/022096 US2012022096W WO2012100210A1 WO 2012100210 A1 WO2012100210 A1 WO 2012100210A1 US 2012022096 W US2012022096 W US 2012022096W WO 2012100210 A1 WO2012100210 A1 WO 2012100210A1
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- WIPO (PCT)
- Prior art keywords
- flow rate
- rotor
- bemf
- pump
- control circuit
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/50—Details relating to control
- A61M60/585—User interfaces
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/10—Location thereof with respect to the patient's body
- A61M60/122—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
- A61M60/165—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable in, on, or around the heart
- A61M60/178—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable in, on, or around the heart drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/20—Type thereof
- A61M60/205—Non-positive displacement blood pumps
- A61M60/216—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller
- A61M60/237—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/20—Type thereof
- A61M60/205—Non-positive displacement blood pumps
- A61M60/216—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller
- A61M60/237—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
- A61M60/242—Non-positive displacement blood pumps including a rotating member acting on the blood, e.g. impeller the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps with the outlet substantially perpendicular to the axis of rotation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/40—Details relating to driving
- A61M60/403—Details relating to driving for non-positive displacement blood pumps
- A61M60/422—Details relating to driving for non-positive displacement blood pumps the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/50—Details relating to control
- A61M60/508—Electronic control means, e.g. for feedback regulation
- A61M60/538—Regulation using real-time blood pump operational parameter data, e.g. motor current
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/50—Details relating to control
- A61M60/508—Electronic control means, e.g. for feedback regulation
- A61M60/538—Regulation using real-time blood pump operational parameter data, e.g. motor current
- A61M60/546—Regulation using real-time blood pump operational parameter data, e.g. motor current of blood flow, e.g. by adapting rotor speed
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/818—Bearings
- A61M60/82—Magnetic bearings
- A61M60/822—Magnetic bearings specially adapted for being actively controlled
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/818—Bearings
- A61M60/824—Hydrodynamic or fluid film bearings
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/80—Constructional details other than related to driving
- A61M60/802—Constructional details other than related to driving of non-positive displacement blood pumps
- A61M60/818—Bearings
- A61M60/825—Contact bearings, e.g. ball-and-cup or pivot bearings
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/33—Controlling, regulating or measuring
- A61M2205/3331—Pressure; Flow
- A61M2205/3334—Measuring or controlling the flow rate
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/10—Location thereof with respect to the patient's body
- A61M60/122—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
- A61M60/126—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable via, into, inside, in line, branching on, or around a blood vessel
- A61M60/148—Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body implantable via, into, inside, in line, branching on, or around a blood vessel in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
Definitions
- a ventricular assist device may be arranged to pump blood at about 1 -10 liters per minute at a pressure differential across the pump of about 10-1 10 mm Hg, depending on the needs of the patient. The needs of the patient may vary with age, height, and other factors.
- One aspect of the invention provides an implantable blood pump system.
- the system desirably comprises a pump and a control circuit.
- the pump includes a housing having an axis, and a rotor disposed within the housing, the rotor being rotatable around the axis.
- the control circuit is operatively coupled to the pump and configured to determine a parameter related to thrust on the rotor along the axis, and to determine a flow rate of blood based at least in part on the parameter.
- the control circuit may be arranged to control operation of the pump based at least in part on the determined flow rate.
- the parameter related to thrust may be the back electromotive force generated in a coil or coils of the pump stator.
- a control circuit for controlling the operation of a blood pump.
- the control circuit desirably comprises a parameter determination circuit and a flow rate determination circuit.
- the parameter determination circuit desirably is operative to determine a parameter related to thrust generated by a rotor of the pump.
- the flow rate determination circuit is operative to determine a flow rate of blood based at least in part on the parameter.
- the pump driver circuit may also be operative to control the pump based on the determined flow rate.
- a method for controlling an implantable blood pump.
- the method desirably comprises determining a parameter relating to thrust generated by a rotor of the pump, and determining a flow rate of blood through the pump, wherein the flow rate is determined based on the parameter and speed of rotation of a rotor of the pump.
- the method may also include controlling the operation of the pump based on the determined flow rate.
- FIG. 1 is a schematic, partially sectional view of a blood pump system in accordance with one embodiment of the invention
- Fig. 2 is a diagrammatic sectional view taken along line 2-2 in Fig. 1.
- Fig. 4 depicts a plot of voltage sampled across a coil in a stator of the blood pump of Figs. 1 -3.
- Fig. 5 is a schematic diagram showing the hardware and software used in the blood pump system of Fig. 1 -3
- Fig. 6 is a graph depicting certain relationships in operation of the blood pump system of Figs. 1 -3.
- the pump also includes a stator 130.
- the stator includes coils 132a-e (Fig. 2) connected in a WYE or delta configuration and placed around the circumference of the housing 1 10.
- the coils are arranged in pairs diametrically opposed to one another.
- coils 132a and 132b form one pair
- coils 132c and 132d form another pair
- coils 132e and 132f form another pair.
- the coils When the coils are driven using a 3-phase current, they provide a magnetic field directed transverse to the bore axis and which rotates around the axis. The magnetic field will interact with the magnetic field of the rotor 120 causing the rotor to turn.
- the voltage applied to the pair of coils varies repeatedly between zero and a selected maximum value at a pulse modulation or chopping frequency much higher than the frequency of the rectangular waveform of the repeating closed-phase and open-phase period.
- Fig. 4 depicts the voltage across coil pair 132a and 132b.
- the voltage applied by the drive circuit is repeatedly chopped or pulse-width modulated.
- the coils 132a and 132b are not energized by the driver circuit 310.
- a relatively small voltage appears across coils 132a and 132b. This voltage is composed primarily of voltage induced in the coil pair 132a and 132b by the rotating magnetic rotor 120.
- the flow determination module 360 may include hardware and/or software for determining the rate at which blood is impelled by the pump 101.
- the flow determination module is operatively connected to current determination module 320, speed determination module 330 and transformation module 350 so that the flow determination module 360 receives values representing current, speed and F(BEMF).
- the flow determination module is arranged to determine the flow rate from the pump based on this information as further discussed below.
- Pump control module 370 is operatively linked to flow determination module 360 so that the pump control module 370 receives values representing the flow rate from the flow determination module.
- the pump control module is also linked to driver circuit 310.
- the pump control module is arranged to determine a desired pump speed based, at least in part, on the flow rate and to command driver circuit 310 accordingly.
- the pump control module can control the pump 100 based on the blood flow rate determined by the flow determination module 370 as further discussed below.
- the control circuit 140 powers the pump 101 , via the driver circuit 310, thereby causing the rotor 120 to spin.
- the rotor 120 spins, blood enters the pump 101 through the inflow end 380 after which the blood is impelled by the rotor 120 from the outflow end 390.
- the blood passes through the pump 101 , it imparts a thrust on the rotor 120. The magnitude of this thrust is related to the flow rate of blood through the pump.
- the rotor 120 is held in position by magnetic and hydrodynamic forces. However, these forces do not hold the rotor with infinite rigidity. Therefore, thrust imparted to the rotor 120 causes the rotor 120 to move by a displacement distance D towards the inflow end 380.
- distance is related to the magnitude of the thrust and, thus, related to the blood flow rate.
- Distance D is greatly exaggerated in Fig. 3 for clarity of illustration; in practice, distance D is small in comparison to the dimension of the rotor and pump.
- Axial displacement of rotor 120 also changes the alignment between the rotor and the coils 132 of the pump.
- the thrust on the rotor is a composite of reaction components directed upstream toward the inlet end of the pump and viscous components directed downstream toward the outlet end. At zero flow, the reaction components predominate and thus the thrust is directed upstream. As the flow rate increases from zero, the viscous components increase and thus the magnitude of the thrust decreases. As the thrust decreases, distance D decreases and the rotor moves into better alignment with the coils, so that BEMF increases.
- F(BEMF) the rate of change in BEMF in the open phase period
- the same curve 620 depicts the relationship between F(BEMF) and the blood flow rate.
- F(BEMF) is a parameter related to the thrust on the rotor.
- the flow determination module 360 determines the flow rate of blood through the pump based in part on this parameter as further explained below.
- the current consumed by the pump also varies with flow rate.
- Curve 610 depicts the variation of current with flow rate at a particular pump operating speed.
- the flow determination module 360 uses both current and F(BEMF) to determine the flow rate.
- the flow determination module uses the value of F(BEMF) and the relationship between F(BEMF) to derive an initial estimate of flow rate. If this initial estimate indicates that the flow rate is below a value M referred to herein as the "fiducial" value, the flow determination module uses the value of current and the relationship between current and flow rate indicated in the left region of curve 610 to determine the flow rate. If the initial estimate of flow rate indicates that the flow rate is above the fiducial value M, the flow determination module uses the value of the current and the relationship between current and flow rate indicated in the right region of curve 610 to determine the flow rate. [0030] The various modules discussed above with reference to Fig.
- Fig. 5 depicts this implementation.
- the control circuit 140 is implemented using a processor 510, a memory 520, data 530, instructions 540, and an interface 550.
- Memory 520 stores information accessible by processor 510, including instructions 540 that may be executed by the processor 510.
- the memory also includes data 530 that may be retrieved, manipulated or stored by the processor.
- the memory may be of any type capable of storing information accessible by the processor, such as a hard-drive, memory card, ROM, RAM, DVD, CD-ROM, write-capable, and read-only memories.
- the processor 510 may be any well-known processor, such as commercially available processors. Alternatively, the processor may be a dedicated controller such as an ASIC.
- Data 530 may be retrieved, stored or modified by processor 510 in accordance with the instructions 540.
- the data may also be formatted in any computer-readable format such as, but not limited to, binary values, ASCII or Unicode.
- the data may comprise any information sufficient to identify the relevant information, such as numbers, descriptive text, proprietary codes, pointers, references to data stored in other memories (including other network locations) or information that is used by a function to calculate the relevant data.
- a current-to-flow table 532 is a tabular representation of the function 610 depicted in Fig. 6.
- the current-to-flow table 532 may identify one or more blood flow rates that result when a given amount of current is used to power the pump 101.
- An example of a current-to flow table 532 is provided as Table 1.
- Curve 610 illustrates, for instance, that when C amperes are used to power the pump 101 , the pump 101 may impel blood at either Fi L/min or L/min.
- the plot illustrates that in this embodiment, there is a many-to-one mapping between current and blood flow rate.
- the BEMF-to-flow table 534 indicates that when the BEMF in the coil 132a changes at the rate of 5.5V/s, the pump 101 impels blood at the rate of 2.5 L/min.
- the BEMF-to-flow table 534 may be implemented as a file, a data structure, as part of a database, or in any other suitable form.
- the instructions 540 may be instructions to be executed directly (such as machine code) or indirectly (such as scripts) by the processor.
- the terms "instructions,” “steps” and “programs” may be used interchangeably herein.
- the instructions may be stored in object code format for direct processing by the processor, or in any other computer language including scripts or collections of independent source code modules that are interpreted on demand or compiled in advance. Functions, methods and routines of the instructions are explained in more detail below.
- Flow estimation module 542 may include instructions for determining the blood flow rate produced by the pump 101 as further explained below, whereas pump control module 544 may include instructions for controlling the operation of the drive circuit 310 (Fig. 3) and thus controlling pump 101 .
- the operations according to instructions 540 is further discussed below with respect to Fig. 7.
- the control circuit 140 may optionally include an interface 550 which connect the control circuit 140 to an output device 560.
- the interface 550 may be an analog interface ⁇ e.g., audio interface) or a digital interface, such as Bluetooth, TCP/IP, 3G, and others. Where the control circuit is implemented in an implantable structure adapted to be disposed within the body of the patient, the interface 550 may include known elements for communicating signals through the skin of the patient.
- the output device 560 may be a speaker, a communications terminal ⁇ e.g., computer, cell phone) or any other type of device.
- Fig. 5 functionally illustrates the processor and memory as being within the same block, it will be understood that the processor and memory may actually comprise multiple processors and memories that may or may not be stored within the same physical housing.
- the memory may include one or more media on which information can be stored.
- the medium holding the instructions retains the instructions in non-transitory form.
- Some or all of the instructions and data may be stored in a location physically remote from, yet still accessible by, the processor.
- the processor may actually comprise a collection of processors which may or may not operate in parallel.
- Fig. 7 depicts a flowchart of a process 700 for determining the rate at which blood is impelled by the pump 101.
- the control circuit 140 determines the amount of current that is used to power the pump 101.
- the control circuit determines a parameter related to thrust imparted on the rotor 120 by the flow of blood exiting the pump 101.
- the determined parameter is the function F(BEMF), the rate of change of BEMF during the open phase periods of coil pair 132a and 132b as discussed above.
- Fig. 8 depicts the sub-steps of step 720.
- the control circuit 140 To determine the F(BEMF), the control circuit 140 first samples voltage across the coil pair 132a and 132(b). In one embodiment, for example, the sampling frequency may be 200 kHz (Task 810). The samples may then be filtered using an average filter.
- the control circuit 140 determines the speed of rotation of the rotor 120. As discussed above the control circuit samples voltage across the coil pair 132a and 132b, identifies open-phase periods in which the voltage appearing across the coil is less than a threshold voltage, and determines the number of the open-phase periods per unit time or, equivalently, the time between successive open-phase periods for a particular coil. The control circuit determines the speed based on this measurement. The greater the number of open- phase periods per unit time, or the lesser the time between successive open-phase periods, the faster the speed.
- control circuit 140 determines the rate at which blood is impelled by the pump 101 based on the parameter related to thrust determined at task 720
- the control terminal retrieves a function that maps the BEMF slope to a blood flow rate, i.e., F(BEMF)-to-flow table 534 (Fig. 5 and Table II, above), for the speed at which the pump is operating.
- the control circuit 140 determines whether the blood flow rate associated with the value of F(BEMF) is above or below a predetermined threshold value ⁇ associated the function 620 (Fig. 6). As depicted in Fig.
- the threshold value 7 ⁇ is a value which is the same, or approximately the same, as the blood flow rate M at the fiducial point which separates the left and right regions of the current-to-flow rate relationship 610 at the speed at which the pump is operating.
- the control circuit may use F(BEMF)-to-flow table 534 (Table II above) and retrieve the value of flow corresponding to the value of F(BEMF). In this process, the control circuit may interpolate between stored values using standard interpolation techniques. The circuit then compares the retrieved value of flow to the threshold T, and determines whether the value of flow indicated by F(BEMF) is above or below the threshold T.
- the same step can be performed by simply comparing F(BEMF) to a threshold value of F(BEMF) indicated T' (Fig. 6) which corresponds to the threshold value of flow T. If this alternative method is used, the memory may not store the entire F(BEMF)-to-flow table 534, but instead may simply store a value T' associated with each operating speed.
- the control circuit 140 retrieves the function 610 that maps an amount of current supplied to the pump 101 to blood flow rate that is generated by the pump 101 , i.e., the current-to-flow table 532 (Fig. 5 and Table 1 , above).
- control circuit 140 branches to one of two different paths. If the threshold comparison (task 920) indicates that F(BEMF) is below threshold T (Fig. 6) task 950 is executed. Otherwise, the control circuit 140 executes task 960.
- the control circuit 140 determines the rate at which blood is impelled by the pump 101 based on the left portion of the function 610. To evaluate the left portion of the function 610, the control circuit 140 may use the value of current as an index and retrieve the corresponding value of flow from the entries in the current-to-flow table 532 (and Table 1 , above) that pertains to the left portion. Alternatively, the control circuit 140 may obtain two or more blood flow rate values that correspond to the same amount of current and then select the smallest one. In either process, standard interpolation techniques can be used when the value of current falls between stored values.
- the control circuit 140 determines the rate at which blood is impelled by the pump 101 based on the right portion of the function 410. To evaluate the right portion of the function 610, the control circuit 140 may use the value of current as an index and retrieve the corresponding value of flow from the entries in the current-to-flow table 532 (and Table 1 , above) that pertain to the right portion. Alternatively, the control circuit 140 may obtain two or more blood flow rate values that correspond to the same amount of current and then select the largest one. In either process, standard interpolation techniques can be used when the value of current falls between stored values.
- the control circuit 740 controls the operation of the pump 101 or takes other action in response to the determined flow rate.
- the control circuit may maintain a set point for the flow rate and a moving average of the flow rates as determined over a preset period as, for example, a few minutes.
- the flow rate set point may be a fixed value or a value determined on the basis of physiological parameters such as the patient's heart rate, respiratory rate or blood oxygen level. If a new value of flow rate is below the moving average by more than a predetermined amount, this may indicate either that the pump has created a suction condition at the intake, or that the outlet of the pump is blocked.
- a suction condition may arise where the intake of the pump is positioned so that as the heart beats, the opening of the intake comes to rest against the wall of the ventricle and the opening is blocked.
- the flow rate may fluctuate as the beating motion of the heart periodically blocks and unblocks the intake.
- the outlet of the pump is blocked, the flow rate typically will remain at a low value without such fluctuations.
- the control circuit can differentiate between such a suction condition and a continual blockage of the pump. Where a suction condition is found, the control circuit may command the drive circuit to momentarily reduce the speed of the pump so as to help clear the condition.
- Figs. 7-9 are provided as examples. At least some of the tasks associated with Figs. 7-9 may be performed in a different order than represented, performed concurrently or altogether omitted.
- control circuit 140 may determine the flow rate based in whole or in part on a signal from the transducer which represents displacement. Stated another way, the displacement is a parameter related to thrust on the rotor. Any other parameter related to thrust on the rotor can be used.
- a blood pump system 1000 in accordance with yet another embodiment of the invention incorporates an active control system comprising an active control module which exerts an axial force on the rotor to counteract the effects of thrust on the rotor and maintain the rotor in a substantially constant axial position.
- active control systems are provided in U.S. Published Patent Application No. 201 10237863, entitled “Magnetically Levitated Blood Pump With Optimization Method Enabling Miniaturization.”
- System 1000 comprises a pump 1001 and control circuit 1070.
- the pump 1001 comprises a rotor 1020 disposed within housing 1010 and actuated by a stator 1030.
- the rotor 1020 comprises coils 1030.
- the pump 1001 (Fig. 10) also comprises electromagnets 1040a-b for producing a magnetic field which exerts an axial force on rotor 1020 that is opposite in direction and similar in magnitude to the thrust imparted on the rotor 1020 by the flow of blood impelled by the pump 1001. The force produced by the electromagnets balances out the thrust and allows the rotor 1020 to remain in place.
- thrust can be measured directly.
- the bearing may incorporate a piezoelectric element or other force transducer.
- the signal from the force transducer, or a function of the signal, may be used as the parameter related to thrust.
- the parameter F(BEMF) related to thrust is used to select a portion of the current-to-flow relationship 610 (Fig. 6), i.e., the left or right portion of the curve.
- the system can determine flow directly from F(BEMF) using the F(BEMF)- to-flow table 534 (Fig. 5 and Table 2, above) whenever the value of flow indicated by F(BEMF) is below the threshold value T, and determine the flow based on the right portion of the current-to-flow relationship 610 when the value of flow indicated by F(BEMF) is above the threshold value T.
- the F(BEMF)- to-flow table 534 Fig. 5 and Table 2, above
- the control circuit 140 need not store relationships between a parameter such as F(BEMF) and flow or between current and flow in the form of lookup tables as discussed above.
- the control circuit may retrieve and evaluate a formula that models the rate at which blood is impelled by the pump as a function of the parameter related to thrust, e.g., a formula for the function 620 (Fig. 6).
- the control circuit may retrieve and evaluate a formula for the current-to-flow relationship, e.g., a formula of the function 610.
- the flow rate determined by the control circuit is used to control the operation of the pump.
- the control circuit may simply determine the flow rate and send a signal representing the flow rate to an external device, and may not control operation of the pump.
- the systems discussed above can determine flow rate through an implanted blood pump, the systems can also deduce the pressure drop across the pump. At a given viscosity and pump operating speed, there is a predetermined relationship between flow rate and pressure drop. For any given pump design, this relationship can be found by experiment and represented in tables of data. Thus, the system can calculate pressure drop from flow rate and report pressure drop in lieu of flow rate, or in addition to flow rate.
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020137022089A KR20140040112A (en) | 2011-01-21 | 2012-01-20 | Flow estimation in a blood pump |
CN201280006098.0A CN103328018B (en) | 2011-01-21 | 2012-01-20 | Flow in blood pump is estimated |
AU2012207146A AU2012207146B2 (en) | 2011-01-21 | 2012-01-20 | Flow estimation in a blood pump |
CA2825354A CA2825354A1 (en) | 2011-01-21 | 2012-01-20 | Flow estimation in a blood pump |
EP12736244.0A EP2665499A4 (en) | 2011-01-21 | 2012-01-20 | Flow estimation in a blood pump |
IL227513A IL227513A0 (en) | 2011-01-21 | 2013-07-17 | Flow estimation in a blood pump |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161434894P | 2011-01-21 | 2011-01-21 | |
US61/434,894 | 2011-01-21 |
Publications (1)
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WO2012100210A1 true WO2012100210A1 (en) | 2012-07-26 |
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PCT/US2012/022096 WO2012100210A1 (en) | 2011-01-21 | 2012-01-20 | Flow estimation in a blood pump |
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US (1) | US9511179B2 (en) |
EP (1) | EP2665499A4 (en) |
KR (1) | KR20140040112A (en) |
CN (1) | CN103328018B (en) |
AU (1) | AU2012207146B2 (en) |
CA (1) | CA2825354A1 (en) |
IL (1) | IL227513A0 (en) |
WO (1) | WO2012100210A1 (en) |
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- 2012-01-20 WO PCT/US2012/022096 patent/WO2012100210A1/en active Application Filing
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Also Published As
Publication number | Publication date |
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US9511179B2 (en) | 2016-12-06 |
IL227513A0 (en) | 2013-09-30 |
US20120245681A1 (en) | 2012-09-27 |
EP2665499A4 (en) | 2017-06-07 |
CN103328018B (en) | 2016-09-21 |
EP2665499A1 (en) | 2013-11-27 |
CN103328018A (en) | 2013-09-25 |
CA2825354A1 (en) | 2012-07-26 |
AU2012207146B2 (en) | 2016-10-06 |
KR20140040112A (en) | 2014-04-02 |
AU2012207146A1 (en) | 2013-09-05 |
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