Managing pump speed when power is limited in a fully implanted lvad system

Abstract

A method of managing the speed of an implantable blood pump. The implantable blood pump is in communication with an internal battery and a transcutaneous energy transfer system (TETS). The method includes starting the pump at a programmed set speed. If the capacity of the internal battery is less than a predetermined reserve level and TETS power is not available, or there is not enough TETS power to maintain the programmed set speed, the speed of the pump is reduced from the programmed set speed to a minimum set speed. If there is not enough power to maintain the programmed set speed, the speed of the pump is gradually reduced from the programmed set speed.

Description

TECHNICAL FIELD

[0001] The present technology relates generally to implantable blood pumps, and in particular to managing the speed of a blood pump when power is limited. BACKGROUND

[0002] With the advent of transcutaneous energy transfer systems (TETS) for implantable blood pumps, the phenomenon of power provided to the implantable blood pump being limited is increased. For example, each of low internal battery power, misalignment of the coil of the TETS without internal battery power, thrombus, or transient power demand can limit the available power of the blood pump. SUMMARY

[0003] The present technology relates generally to implantable blood pumps, and in particular to managing the speed of a blood pump when power is limited.

[0004] In one aspect, the present disclosure provides a method of managing the speed of an implantable blood pump. The implantable blood pump is in communication with an internal battery and a transcutaneous energy transfer system (TETS). The method includes starting the pump at a programmed set speed. If the capacity of the internal battery is less than a predetermined reserve level and TETS power is not available, or there is not enough TETS power to maintain the programmed set speed, the speed of the pump is decreased from the programmed set speed to a minimum set speed. If there is not enough power to maintain the programmed set speed, the speed of the pump is gradually decreased from the programmed set speed.

[0005] In another aspect of the present embodiment, if the capacity of the internal battery is greater than the predetermined reserve level or TETS power is available, and there is enough power margin, the method further includes gradually increasing the speed of the pump from the minimum set speed to the programmed set speed.

[0006] In another aspect of the present embodiment, if the programmed set speed cannot be achieved by the available power, the method further includes decreasing the speed of the pump to the minimum set speed after gradually increasing the speed of the pump from the minimum set speed.

[0007] In another aspect of the present embodiment, if the power is sufficient to maintain the minimum set speed, the method further includes increasing the speed of the pump to the programmed set speed after gradually decreasing the speed of the pump from the minimum set speed.

[0008] In another aspect of the present embodiment, if the pump speed is less than a critical cutoff speed after gradually decreasing the speed of the pump, the method further includes confirming that the pump has stopped.

[0009] In another aspect of the present embodiment, the method further includes attempting to restart the pump after the pump has stopped.

[0010] In another aspect of the present embodiments, the pump is in communication with an implantable controller, and wherein the implantable controller comprises a battery.

[0011] In another aspect of the present embodiments, the battery is in communication with an internal coil of a TETS.

[0012] In another aspect of the present embodiments, the internal coil of the TETS is in communication with an external coil of the TETS, which is further in communication with a power source.

[0013] In another aspect of the present embodiments, the power source is one from a group consisting of a wall outlet and a battery.

[0014] In one aspect, a control circuit for controlling a speed of an implantable blood pump (the control circuit being in communication with a battery and a transcutaneous energy transfer system (TETS)) comprises a processing circuit configured to start the pump at a programmed set speed. If a capacity of the battery is less than a predetermined reserve level and TETS power is not available, or there is not enough power margin, the speed of the pump is decreased from the programmed set speed to a minimum set speed. If there is not enough power to maintain the minimum set speed, the speed of the pump is gradually decreased from the programmed set speed.

[0015] In another aspect of the present embodiments, if the power level of the battery is greater than the predetermined reserve level or TETS power is available, and there is enough power margin, the processing circuit is further configured to gradually increase the speed of the pump from the minimum set speed to the programmed set speed.

[0016] In another aspect of the present embodiments, if the programmed set speed cannot be achieved by the available power, the processing circuit is further configured to decrease the speed of the pump to the minimum set speed after gradually increasing the speed of the pump from the minimum set speed.

[0017] In another aspect of the present embodiments, if the power is sufficient to maintain the minimum set speed, the processing circuit is further configured to increase the speed of the pump to the programmed set speed after gradually decreasing the speed of the pump to the minimum set speed.

[0018] In another aspect of the present embodiments, if the pump speed is less than a critical cutoff speed after gradually decreasing the speed of the pump, the processing circuit is further configured to confirm that the pump has stopped.

[0019] In another aspect of the present embodiments, the processing circuit is further configured to attempt to restart the pump after the pump has stopped.

[0020] In another aspect of the present embodiments, the pump is in communication with an implantable controller, and wherein the implantable controller comprises a battery.

[0021] In another aspect of the present embodiments, the internal battery is in communication with the internal coil of the TETS.

[0022] In another aspect of the present embodiments, the internal coil of the TETS is in communication with an external coil of the TETS, which is also in communication with a power source, wherein the power source is one from a group consisting of a wall outlet and a battery.

[0023] In one aspect, a control circuit for controlling a speed of an implantable blood pump, the control circuit in communication with an internal battery and a transcutaneous energy transfer system (TETS), the control circuit comprising a processing circuit configured to start the pump to a programmed set speed. If a capacity of the internal battery is less than a predetermined reserve level and TETS power is not available, or there is not enough TETS power to maintain the programmed set speed, the speed of the pump is reduced from the programmed set speed to a minimum set speed. If there is not enough power to maintain the minimum set speed, the speed of the pump is gradually reduced from the minimum set speed. If the power is sufficient to maintain the minimum set speed, the speed of the pump is increased to the programmed set speed after the speed of the pump is gradually reduced from the minimum set speed. If the pump speed is less than a critical cutoff speed after the speed of the pump is gradually reduced, the pump is turned off.

[0024] The specifics of one or more aspects of the present disclosure are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the technology described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0025] A more complete understanding of the present application, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0026] Figure 1 is an internal system view of an implantable blood pump with a TETS receiver source constructed in accordance with the principles of the application;

[0027] Figure 2 is Figure 1 is an external view of a TETS transmitter and controller of the system shown; and

[0028] Figure 3 is a flow chart illustrating a method of managing blood pump speed when power is limited. DETAILED DESCRIPTION

[0029] It should be understood that various aspects disclosed herein can be combined in different combinations than the combinations expressly presented in the description below. It should also be understood that, depending on the example, certain acts or events of any of the processes described herein can be performed in a different sequence, can be added, modified or omitted (e.g., all described acts or events can not be required, or a desired result can be achieved in only some acts or events). Additionally, the described processes can be performed by a single module or a combination of modules. For example, the processes can be performed by a combination of a medical device and a medical device application running on a computing device.

[0030] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to

[0031] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor" as used herein can refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the

[0032] Referring now to the drawings, in which like reference numerals represent like elements Figure 1 and Figure 2 An exemplary transcutaneous energy transfer system ("TETS") constructed in accordance with the principles of the present application is shown in FIGS. 1-3 and is indicated generally at "10." The TETS 10 can be fully implanted within a patient (whether human or animal), that is, there is no transcutaneous connection between the implanted components of the TETS 10 and components external to the patient. In Figure 1In the illustrated configuration, the TETS 10 includes an internal controller 12 implanted within the patient. The internal controller 12 includes control circuitry having processing circuitry configured to control operation of an implantable blood pump 14. The internal controller 12 can include an internal power source 13 configured to power components of the controller and to power one or more implantable medical devices, such as the implantable blood pump, such as a ventricular assist device ("VAD") 14 implanted within the left ventricle of the patient's heart. The power source 13 can include various different types of power sources, including an implantable battery. The VAD 14 can comprise a centrifugal pump, an axial pump, or other kind of electromagnetic pump configured to pump blood from the heart to a blood vessel for circulation around the body. One such centrifugal pump is an HVAD, and is shown and described in U.S. Patent No. 7,997,854. One such axial pump is an MVAD, and is shown and described in U.S. Patent No. 8,419,609. In one exemplary configuration, the VAD 14 is electrically coupled to the internal controller 12 by one or more implantable conductors 16 configured to power the VAD 14, relay one or more measured feedback signals from the VAD 14, and / or provide operational instructions to the VAD 14.

[0033] With continued reference to Figure 1 , the receiving coil or internal coil 18 can also be coupled to the internal controller 12 by, for example, one or more implantable conductors 20. In one exemplary configuration, the receiving coil 18 can be implanted subcutaneously near the chest, although any subcutaneous location can be utilized for implanting the receiving coil 18. The receiving coil 18 is configured to be inductively powered by a transmitting coil or external coil 22 (see Figure 2 ) disposed opposite the receiving coil 18 outside / external to the patient. For example, as shown in Figure 2 , the transmitting coil 22 can be coupled to an external controller 23 having a power source 24, such as a portable battery or wall power source carried by the patient. In one configuration, the battery is configured to generate a radio frequency signal for transmitting energy from the transmitting coil 22 to the receiving coil 18. The receiving coil 18 can be configured to be in transcutaneous inductive communication with the transmitting coil 22.

[0034] Reference is now made to Figure 3wherein an exemplary method of managing the speed of an implantable blood pump 14 is shown. The method includes starting the pump 14. That is, initially the pump is off and the control circuit of the controller 12 is configured to start the pump 12 and bring the speed of the pump 14 to a programmed set speed, e.g., 2400 RPM - 3200 RPM. If the pump 14 is not initially started, the control circuit is configured to make multiple attempts to start the pump. The set speed can be programmed by a clinician or can be a default value preprogrammed into the controller 12. If the power level of the internal battery 13 is less than a predetermined reserve level and TETS power is not available, or there is not enough power margin, the control circuit is further configured to reduce the speed of the pump from the programmed set speed to a minimum set speed, e.g., 1800 RPM - 2200 RPM. For example, the power margin can be a predefined threshold related to the difference between, for example, available power and used power. In other configurations, the power margin can be an absolute threshold related to the voltage, current, or power supplied to the pump 14. In yet other configurations, the power margin can be a threshold based on the percentage of the pulse width modulation duty cycle of the signal provided to the pump 14. For example, if common power transients typically cause the PWM duty cycle to increase by 10%, the threshold for "insufficient power margin" can be a PWM duty cycle of 90%.

[0035] The controller 12 can include a minimum set speed at which the pump 14 operates while providing sufficient blood flow. This minimum set speed can be programmed into the controller 12 or set by a clinician. If the power level of the internal battery 13 is greater than a predetermined reserve level or TETS power is available, and there is sufficient power margin, the control circuit is configured to attempt to gradually increase the speed of the pump from the minimum set speed to the programmed set speed. The speed increase can ramp up or step up from the minimum set speed and can occur after a predetermined amount of time or immediately. If the pump 14 cannot reach the programmed set speed, the control circuit reduces the speed of the pump 14 back to the minimum set speed. If there is not enough power to maintain the minimum set speed, the control circuit gradually reduces the speed of the pump 14 from the minimum set speed to attempt to maintain any possible speed with the minimum power. The speed reduction can ramp down or step down from the minimum set speed and can occur after a predetermined amount of time or immediately. If the pump speed is less than a critical cutoff speed (e.g., 900 RPM - 1200 RPM after gradually reducing the speed of the pump 14), the control circuit is configured to turn the pump 14 off. Furthermore, at any one of these stages, the pump 14 can be turned off due to a complete power outage, a malfunction, or via an explicit programming command.

[0036] Those skilled in the art will appreciate that the application described herein is not limited to what has been particularly shown and described above. Furthermore, unless mentioned otherwise, all percentages are on a weight basis, all measurements are at 25°C, and all pressures are at or near atmospheric pressure. In addition, it should be noted that all figures are not drawn to scale. Numerous modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the application, which is defined by the appended claims.

Claims

1. A control circuit for controlling the speed of an implantable blood pump, the control circuit comprising: processing circuitry configured to: start the pump to a programmed set speed; if there is not enough power available to run the pump at the programmed set speed, reduce the speed of the pump from the programmed set speed to a minimum set speed; if there is not enough power to maintain the speed of the pump at the minimum set speed, gradually reduce the speed of the pump from the minimum set speed to maintain any possible speed with minimum power; and if the speed of the pump is less than a critical cutoff speed after gradually reducing the speed of the pump from the minimum set speed, shut down the pump.

2. The control circuit of claim 1, wherein if there is enough power available, the processing circuitry is further configured to gradually increase the speed of the pump from the minimum set speed to the programmed set speed.

3. The control circuit of claim 2, wherein if the programmed set speed cannot be achieved by available power, the processing circuitry is further configured to, after gradually increasing the speed of the pump from the minimum set speed, reduce the speed of the pump to the minimum set speed.

4. The control circuit of claim 1, wherein if power is sufficient to maintain the minimum set speed, the processing circuitry is further configured to, after gradually reducing the speed of the pump to the minimum set speed, increase the speed of the pump to the programmed set speed.

5. The control circuit of claim 1, wherein the processing circuitry is further configured to include attempting to restart the pump after the pump has stopped.

6. The control circuit of claim 1, wherein the programmed set speed is in the range of 2400-3200 RPM.

7. The control circuit of claim 1, wherein the minimum set speed is in the range of 1800-2200 RPM.

8. The control circuit of claim 1, wherein the critical cutoff speed is in the range of 900-1200 RPM.

9. The control circuit of claim 1, wherein the processing circuitry is further configured to shut down the pump due to a complete power outage, a malfunction, or via an explicit programming command. ​

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