Blood pump system and method for controlling the speed of a drive unit of a blood pump

Abstract

The present invention relates to a blood pump system (10) comprising a blood pump (12), in particular an intravascular blood pump, having a pump housing (20) with a blood flow inlet (22) and a blood flow outlet (24) connected by a passage (26), an impeller (30) disposed in said pump housing (20), a drive unit (28) configured to drive the impeller (30) at an actual speed so that a flow is generated between the blood flow inlet (22) and the blood flow outlet (24). The blood pump (12) further comprises a sensor arrangement (14) configured to output pressure data comprising an indication for blood vessel pressure and / or an indication for ventricular pressure and a controller (16). The controller (16) is configured to adjust a speed profile controlling the actual speed of the drive unit (28) based on the pressure data outputted by the sensor arrangement (18) so that an actual flow at the blood flow outlet (24) corresponds to a target flow.

Description

[0001] BLOOD PUMP SYSTEM AND METHOD FOR CONTROLLING THE SPEED OF A DRIVE UNIT OF A BLOOD PUMP

[0002] The present invention relates to a blood pump system. In particular, the present invention relates to a blood pump system comprising a blood pump, in particular an intravascular blood pump for percutaneous insertion into a patient’s blood vessel, to support a blood flow in a patient’s blood vessel. The blood pump may also be an intracardiac blood pump. The present invention further relates to a method for controlling the speed of a drive unit of the blood pump.

[0003] BACKGROUND OF THE INVENTION

[0004] Various blood pumps are known from the prior art, e.g. axial blood pumps, centrifugal (i.e. radial) blood pumps or mixed-type blood pumps, where the blood flow is caused by axial forces as well as by radial forces. Such blood pumps may be introduced into the heart of a patient to support the blood flow from the heart into a blood vessel e.g., the aorta or the pulmonary artery. The blood pump may be introduced percutaneously during a cardiac procedure through the vascular system, such as by a catheterization procedure. After the blood pump has been placed, blood may be unloaded by the blood pump from the left ventricle into the aorta or from the right ventricle into the pulmonary artery to restore adequate systemic blood flow. Therefore, a blood pump typically comprises of a pump housing having a blood flow inlet and a blood flow outlet connected by a passage, a pump element in form of an impeller disposed in said pump housing and a drive unit configured to drive the impeller at an actual speed so that a flow of blood is generated between the blood flow inlet and the blood flow outlet.

[0005] During the cardiac cycle (i.e. during one heartbeat) the pressure conditions in the respective ventricle and the blood vessel are not constant, but rather are modified due to relaxation of the heart and refilling with blood during the diastole and contraction and pumping action of the heart during systole. Thus, the pressure conditions and hence the actual flow is not continuous.

[0006] An intravascular blood pump placed in the patient’s heart is operated at a given speed and generates a continuous flow. Although intravascular blood pumps are intended as ventricular assist devices, the patient’s heart is performing a (likely decreased or impaired) pumping action which adds a non- continuous flow to the continuous flow generated by the intravascular blood pump. Accordingly, a continuous intended target flow of e.g., 3.5 l / min or 4 l / min may not be achieved.

[0007] Hence, it is an objective to provide a blood pump system and a method for operating a blood pump allowing for constant flow independent of the pressure conditions in the patient’s heart. SUMMARY OF THE INVENTION

[0008] According to a first aspect, the blood pump system comprises a blood pump, in particular an intravascular blood pump, having a pump housing with a blood flow inlet and a blood flow outlet connected by a passage. A pump element in form of an impeller is disposed in said pump housing. The blood pump further comprises a drive unit configured to drive the impeller at an actual speed so that a flow is generated between the blood flow inlet and the blood flow outlet. The blood pump system further comprises a controller and a sensor arrangement configured to output pressure data comprising an indication for blood vessel pressure and / or an indication for ventricular pressure. The controller is configured to adjust a speed profile controlling the actual speed of the drive unit based on the pressure data outputted by the sensor arrangement so that an actual flow at the blood flow outlet corresponds to a target flow.

[0009] In case the blood pump system is used as a left ventricular support, the blood vessel pressure is the aortic pressure and the ventricular pressure is the left ventricular pressure. Accordingly, if used as a right ventricular support, the blood vessel pressure is the pulmonary artery pressure and / or the central venous pressure and the ventricular pressure is the right ventricular pressure.

[0010] In sense of the invention, the actual flow is the entire flow exiting the blood pump through the blood flow outlet. In other words, the actual flow is the pump flow i.e., the flow which runs through the pump housing. Accordingly, the actual flow meets the set target flow during a full heartbeat independent of the pressure conditions within the heart during the full heartbeat, as the actual flow is composed of the flow generated by the pumping element and a possible but likely impaired flow generated by the pumping action of the patient’s heart which runs through the blood pump. Thus, The actual flow remains virtually constant at the intended target flow as the actual speed of the drive unit is modified based on the speed profile. The controller computes the pressure conditions in the heart from the received pressure data and adjusts the speed profile for a complete heartbeat and controls the actual speed to computed pressure conditions. The pressure conditions in the heart can be computed from pressure data giving indications for the blood vessel pressure or the ventricular pressure. Of course, it is preferable that the pressure data gives indications for both, the blood vessel pressure and the ventricular pressure. The speed profile depicts a curve or a collection of speed values denoting the modification of the speed of the drive unit during a full heartbeat or any other suitable time span. As such, during diastole the actual speed of the drive unit will be higher than during systole.

[0011] The blood pump of the blood pump system according to the present disclosure may correspond to the aforementioned blood pump. Hence, the blood pump may be an intravascular blood pump or an intracardiac blood pump. The blood pump may comprise the sensor arrangement in that sensors are positioned e.g., at the pump housing. The sensors may be optical sensors. The sensor arrangement of the blood pump system may also be a sensor arrangement independent from the blood pump.

[0012] Preferably, the sensor arrangement is configured to output pressure data comprising at least one of a pressure value relating to the pressure upstream of or at the blood flow inlet as an indication for the ventricular pressure or a pressure value relating to the pressure downstream of or at the blood flow outlet as an indication for the blood vessel pressure. Said pressure values may be measured with sensors disposed in close vicinity to the blood flow inlet and / or the blood flow outlet.

[0013] The blood pump system my comprise a storage device. The speed profile may be stored in the storage device. A characteristic diagram relating the pressure data to a flow of the drive unit may be stored in the storage device. The controller may be configured to read out an ideal speed from the characteristic diagram based on the pressure data and the target flow. The controller may calculate a set speed of the speed profile based on the ideal speed and may set the actual speed to the set speed of the speed profile.

[0014] The characteristic diagram may be an individual characteristic diagram for the individual blood pump. The characteristic diagram may also be a characteristic diagram for the type series of the blood pump. In addition or alternatively, the characteristic diagram may also be a characteristic diagram for a group of blood pumps within a type series. In this regard, the individual blood pump used may be classified to belong to a certain group. Further, the characteristic diagram may be adaptable to account for changes over the runtime of the blood pump caused e.g., by wear.

[0015] The characteristic diagram comprises hydraulic flow curves for different speeds of the drive unit denoting a resulting flow based on the pressure data. Each hydraulic curve may denote a P-level of the drive unit, i.e. a certain speed of the drive unit delivering a certain flow for a pressure difference or pressure gradient across the blood pump, i.e. between the blood flow inlet and the blood flow outlet. The ideal speed may either be derived directly from the corresponding hydraulic curve or may be derived via extrapolation or interpolation. Preferably, the extrapolation and / or interpolation is carried out by the controller.

[0016] The controller may be configured to consider a speed offset based on the actual speed of the drive unit for calculation of the set speed. As the blood pump is generating a certain blood flow when the pressure data is determined, the generated blood flow of the blood pump needs to be accounted. Thus, a certain speed offset is deducted from the calculated set speed. The speed offset may be a constant value, a value related to the actual speed, ideal speed or set speed respectively. Alternatively, the speed offset may be value computed from the characteristic diagram. The controller may be configured to store a time section of the set speed and / or a time section of the ideal speed and / or a time section of the actual speed and / or a time section of the pressure data in the storage device. Preferably, the controller is further configured to determine an inertia of the impeller based on an analysis of the time section of the actual speed and / or the set speed and / or the time section of the pressure data and to consider the inertia of the impeller for calculation of the set speed. Thus, when the speed profile is adjusted or initially generated, the inertia of the impeller may be considered allowing for a smoothing of the generated flow.

[0017] The controller may be configured to identify a recurring pattern in the pressure data. The recurring pattern may a characteristic timepoint in the ventricular pressure i.e., the left ventricular pressure or the right ventricular pressure. In case of the blood pump being used as a left ventricular support, the recurring pattern may for instance be depicted by the minimum value at the end of the relaxation phase of the left ventricle which depicts the beginning of the diastole. The recurring pattern may for instance also be the maximum pressure gradient during the contraction phase at the beginning of the systole. The recurring pattern may for instance also be the starting point of the contraction phase of the left ventricle, the so-called end-diastolic pressure point. The recurring pattern is used to define the beginning and the end of one heartbeat.

[0018] The controller may further be configured to repeat the adjustment of the speed profile based on optimizing a mathematical cost function. Based on the pressure data, the controller computes a statistical dispersion or variability between an actual value and the set value i.e., the control error. For instance, the controller may compute a variability or mean difference between the target flow and an actually generated flow per heartbeat. An error dimension like standard deviation, standard error or root mean squared error may be computed and compared to a predefined threshold value or acceptance interval. As soon as the error dimension exceeds the threshold value or the acceptance interval, the adjustment of the speed profile is replayed. In other words, in case the patient’s heartbeat is absolutely constant and the pressure conditions do not change, nearly no adjustment of the speed profile will occur.

[0019] The controller may also be configured to adjust the speed profile at a predefined frequency, preferably to adjust the speed profile at a predefined frequency of the recurring pattern. For instance, the speed profile may be adjusted in predefined time intervals e.g., every 5 seconds. The speed profile may also be adjusted e.g., every five heartbeats, with the beginning and the end of an heartbeat being defined by the recurring pattern.

[0020] The controller may be configured to apply a signal filter, for instance a low pass filter. Thus, insignificant erroneous pressure data can be filtered. Overall, this avoids unnecessary adjustment of the speed profile. According to a second aspect, a method for controlling the speed of a drive unit of a blood pump of a blood pump system is provided. The blood pump of the blood pump system according to the present disclosure may correspond to the aforementioned blood pump. Hence, the blood pump may be an intravascular blood pump or an intracardiac blood pump. The blood pump comprises a pump housing having a blood flow inlet and a blood flow outlet connected by a passage and a pump element in form of an impeller disposed in said pump housing. The blood pump further comprises a drive unit configured to drive the impeller at an actual speed so that a flow is generated between the blood flow inlet and the blood flow outlet. The method comprises the following steps: receiving pressure data comprising an indication for blood vessel pressure and / or an indication for ventricular pressure, and adjusting a speed profile controlling the actual speed of the drive unit based on the received pressure data so that an actual flow at the blood flow outlet corresponds to a target flow.

[0021] In case the blood pump system is used as a left ventricular support, the blood vessel pressure is the aortic pressure and the ventricular pressure is the left ventricular pressure. Accordingly, if used as a right ventricular support, the blood vessel pressure is the pulmonary artery pressure and / or the central venous pressure and the ventricular pressure is the right ventricular pressure.

[0022] The step of receiving pressure data may further comprise: receiving at least one of a pressure relating to the pressure upstream of or at the blood flow inlet as an indication for the ventricular pressure or a pressure relating to the pressure downstream of or at the blood flow outlet as an indication for the blood vessel pressure.

[0023] The step of adjusting the speed profile may further comprise: reading out an ideal speed based on the pressure data from a characteristic diagram relating the pressure data to the target flow, calculating a set speed of the speed profile based on the ideal speed, and setting the actual speed to the set speed of the speed profile.

[0024] The step of calculating the set speed of the speed profile may further comprise: considering a speed offset based on the actual speed.

[0025] The method may further comprise: storing a time section of the set speed and / or a time section of the ideal speed and / or a time section of the actual speed and / or a time section of the pressure data.

[0026] The step of calculating the set speed of the speed profile may further comprise: determining an inertia of the impeller based on an analysis of the time section of the actual speed and / or the set speed and / or the pressure data, and considering the inertia of the impeller for calculation of the set speed.

[0027] The method may further comprise: identifying a recurring pattern in the pressure data. The method may further comprise: adjusting the speed profile based on optimizing a mathematical cost function, and / or adjusting the speed profile at a predefined frequency, preferably adjusting the speed profile at a predefined frequency of the recurring pattern.

[0028] The method according to the present disclosure has the corresponding features and advantages over known methods for controlling the speed of a drive unit of a blood pump of a blood pump system as the blood pump system according to the disclosure as described above to which is thus referred to.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing summary as well as the following detailed description of preferred embodiments will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, reference is made to the drawings. However, the scope of the disclosure is not limited to the specific embodiments disclosed in the drawings.

[0031] In the drawings:

[0032] Fig. 1 shows a schematic overview of a blood pump system according to the present disclosure;

[0033] Fig. 2 is a side view of a pump housing of a blood pump of the blood pump system of Fig. 1 ;

[0034] Fig. 3 is a chart showing left ventricular pressure, aortic pressure, actual speed of a drive unit of the blood pump and set speed for one heartbeat;

[0035] Fig. 4 is a characteristic diagram for the blood pump relating pressure data to a flow;

[0036] Fig. 5 is a chart showing left ventricular pressure and aortic pressure for six consecutive heartbeats;

[0037] Fig. 6 is a chart showing the actual speed of the drive unit of the blood pump and the set speed for the heartbeats shown in Fig. 5; and

[0038] Fig. 7 is a chart showing target flow and actual flow.

[0039] DETAILED DESCRIPTION

[0040] Fig. 1 shows a schematic overview over a blood pump system 10. The blood pump system 10 comprises a blood pump 12, a sensor arrangement 14, a controller 16 and a storage device 18. The blood pump 12, the sensor arrangement 14 and the storage device 18 are connected to the controller 16 by suitable devices e.g., by cables. Of course, wireless connections are also possible. In addition, the storage device 18 may be an integral part of the controller 16.

[0041] The blood pump 12 may be an intravascular blood pump belonging to the Impella® product family of the applicant. The blood pump 12 comprises a pump housing 20 with a blood flow inlet 22 and a blood flow outlet 24. The blood flow inlet 22 is connected to the blood flow outlet 24 by a passage 26. Here, the pump housing 20 comprises a plurality of blood flow outlets 24 evenly distributed around the circumference of the blood pump housing 20, see also Fig. 2.

[0042] A drive unit 28 is disposed within the pump housing 20. The drive unit 28 is configured to drive a pump element in form of an impeller 30 disposed in the pump housing 20 at a certain speed, as will be explained in more detail below. Although the drive unit 28 is disposed in the pump housing 20 in the embodiment shown, it is also possible that the drive unit 28 is externally provided and connected to the impeller 30 by suitable device.

[0043] Rotation of the impeller 30 may be caused by a direct connection between the drive unit 28 and the impeller 30 or an indirect connection, like a magnetic coupling. When the impeller 30 rotates, a blood flow is generated between the blood flow inlet 22 along the passage 26 to the blood flow outlet 24. In particular, when placed in the patient’s heart, the blood flow inlet 22 is positioned so that blood from the ventricle of the patient’s heart can be drawn into the blood pump 12 and can exit the blood pump 12 through the blood flow outlet 24 into the blood vessel. In addition to the blood flow generated by the blood pump 12 between blood flow inlet 22 and the blood flow outlet 24, a blood flow generated by the pumping action of the patient’s heart may be added, which depends on the cardiac conditions of the patient so that the actual blood flow at the blood flow outlet 24 does not necessarily correspond to only the blood flow generated by the blood pump 12. Rather, the actual flow is the entire flow exiting the blood pump 12 through the blood flow outlet 24.

[0044] In the embodiment shown in Fig. 2, the sensor arrangement 14 comprises two sensors 32, 34 which are disposed on an outer peripheral surface of the pump housing 20. The two sensors 32, 34 may be optical pressure sensors. One of the sensors 32 is positioned in close vicinity to the blood flow inlet 22 so that the detected pressure delivers an indication for the ventricular pressure, in particular for the left ventricular pressure LVP (when the blood pump 12 is used as a left ventricular support). The other one of the two sensors 34 is positioned in vicinity to the blood flow outlet 24 so that the detected pressure delivers an indication for the blood vessel pressure, in particular for the aortic pressure AOP (when the blood pump 12 is used as a left ventricular support). Hence, the sensor arrangement 14 is configured to output pressure data comprising an indication for aortic pressure AOP and left ventricular pressure LVP. The blood pump 12 may also be used a right ventricular support. In this case, right ventricular pressure and pulmonary artery pressure are indicated by the pressure detected by the two sensors 32, 34. However, in the following it is exemplarily referred to the blood pump 12 being a left ventricular support.

[0045] The sensor arrangement 14 may be an externally provided sensor arrangement delivering pressure data comprising an indication for aortic pressure AOP and left ventricular pressure LVP. For instance, the sensor arrangement may comprise a sensor introduced by a catheter into the aorta to determine the aortic pressure AOP or into the left ventricle to determine the left ventricle pressure LVP. The pressure data outputted by the sensor arrangement 14 is signaled to the controller 16 for adjustment of a speed profile controlling the actual speed AS of the drive unit 28.

[0046] Although it is described in the exemplary embodiment that the pressure data comprises aortic pressure AOP as well as left ventricular pressure LVP, it is sufficient for the below described method for controlling the speed of the drive unit 28 of the blood pump 12 to determine only one of the aortic pressure AOP and left ventricular pressure LVP.

[0047] The drive unit 28 drives the impeller 30 at an actual speed AS which is defined in the speed profile. The speed profile depicts a curve or a collection of speed values denoting the modification of the speed of the drive unit 28 during a full heartbeat or any other suitable time span. The speed profile may be stored in the storage device 18 and may be adjusted and modified by the controller 16, as will now be described in more detail.

[0048] Initially, the speed profile comprises an initial set speed SS which drives the drive unit 28, and hence the impeller 30, at a given speed e.g., 24,000 rpm. However, the controller 16 can adjust the speed profile so that the actual flow AF at the blood flow outlet 24 corresponds to a predefined target flow TF of e.g., 4 l / min independently of the pumping action of the patient’s heart. Of course, it is not possible to exactly reach an actual flow AF corresponding to the target flow TF. Hence, a certain deviation between the actual flow AF and the target flow TF is tolerated. Accordingly, the term “corresponding” as used herein for describing the relationship between the actual flow AF and the target flow TF is to be understood broadly.

[0049] After placement of the blood pump 12, the drive unit 28 is operated by the controller 16 to drive the impeller 30 at the set speed SS stored in the speed profile. This initial operation is shown for one heartbeat in Fig. 3. There, the set speed SS of the speed profile of 24,000 rpm is denoted by a dashed line on the secondary ordinate. The actual speed AS of the drive unit 28 and hence the impeller 30 is shown by the black solid line. The peak in the beginning with the speed dropping to about 20,000 RPM is caused by blooming of the impeller 30 e.g., due to inertia. Thereafter, the actual speed AS virtually corresponds to the set speed SS.

[0050] During this initial phase, the pressure data is recorded by the controller 16 and stored in the storage device 18. In Fig. 3, the left ventricular pressure LVP is shown as a bold gray solid line and the aortic pressure AOP is shown by the thin black solid line for one heartbeat. The controller 16 then identifies a recurring pattern in the pressure data, namely a recurring pattern in the left ventricular pressure LVP. The recurring pattern is a characteristic timepoint for every heartbeat and is used to differentiate between two heartbeats. The recurring pattern may for instance be depicted by the minimum value of the left ventricular pressure LVP at the end of the relaxation phase, which corresponds to the beginning of the diastole (approximately at timepoint 110 in Fig. 3). In the embodiment shown, the recurring pattern is set to be the maximum pressure gradient during the contraction phase at the beginning of the systole (approximately at timepoint 0 in Fig. 3). The recurring pattern may for instance also be the starting point of the contraction phase of the left ventricle, the so-called end- diastolic pressure point.

[0051] Next, the controller 16 reads out an ideal speed from a characteristic diagram CD stored in the storage device 18. An example for a characteristic diagram is shown in Fig. 4. The characteristic diagram comprises hydraulic flow curves (P1 to P9) for different speeds of the blood pump 12 relating the pressure difference or pressure gradient across the blood pump 12 to the reached blood flow. For instance, the hydraulic flow curve P5 denotes the speed of 24,000 rpm. The hydraulic flow curves ascend and descend in steps of 2,000 rpm. Hence, the hydraulic flow curve P6 denotes a speed of 26,000 rpm and the hydraulic flow curve P4 denotes a speed of 22,000 rpm. The hydraulic flow curves P1 to P9 may be individual flow curves for the particular blood pump 12, or may be hydraulic flow curves for the entire type series of the blood pump 12 or for a group of blood pumps within a type series.

[0052] The pressure difference across the blood pump 12 corresponds to the pressure gradient between the blood flow inlet 22 and the blood flow outlet 24 and hence, to the pressure gradient between the left ventricular pressure LVP and the aortic pressure AOP. The controller 16 derives an ideal speed from the characteristic diagram CD for reaching the intended target flow TF of e.g. 4 l / min for every timepoint within one heartbeat. In case no hydraulic flow curve P1 to P9 is given for a certain pressure difference, the controller 16 is configured to calculate an ideal speed based on interpolation and extrapolation between neighboring hydraulic flow curves P1 to P9. The so derived ideal speeds for every timepoint within one heartbeat are then computed by the controller 16 to derive set speeds SS for the drive unit 28 for every time point. In doing so, the controller 16 is configured to consider a speed offset based on the actual speed AS of the drive unit 28 during this initial phase. In the exemplary embodiment described, the actual speed AS of the blood pump is set to be 24,000 rpm during the initial phase. In other words, the actual speed AS of 24,000 rpm has a certain influence on the pressure gradient across the blood pump 12 and hence, on the ideal speeds derived from the characteristic diagram. As such, a fixed speed offset is deducted from the derived ideal speeds. In the exemplary embodiment, the speed offset is set to be 1 ,600 rpm. However, the speed offset does not need to be a fixed value, but may be dependent from further variables, like the pressure data.

[0053] The controller 16 then stores the computed set speeds SS in the speed profile. For the next heartbeat beginning at the recurring pattern, the actual speed AS of the drive unit 28 is set to correspond to the set speeds SS of the speed profile. In essence, the drive unit 28 is operated at different speeds based on modulated set speeds SS during one heartbeat so that the actual flow AF at the blood flow outlet 24 corresponds to the predefined and intended target flow TF of e.g., 4 l / min. With every recurring pattern for every consecutive heartbeat, the speed profile is replayed from the beginning.

[0054] The controller 16 is further configured to store a time section of the various data in the storage device 18, in particular of the pressure data, the set speed SS and the actual speed AS. From analyzing said data, the controller 16 may derive an inertia for the impeller 30 based on a comparison between the timing of setting of an actual speed AS to a set speed SS and the timing of reaching the intended actual speed AS. Based thereupon, the controller 16 determines information on the inertia of the impeller 30 and adjusts the speed profile to consider the inertia of the impeller 30. The controller 16 may derive a fixed value for considering the inertia, or may derive a function for the inertia based on the set speed SS.

[0055] The speed profile is reevaluated during normal operation of the blood pump 12 to account for altered conditions. Therefore, the above described method for adjusting the speed profile is reiterated e.g., every five heartbeats. Accordingly, once the speed profile has been adjusted, it is assumed that the conditions remain constant for the next consecutive four heartbeats. A time section showing the left ventricular pressure LVP (bold grey line) and the aortic pressure AOP (black solid thin line) for six consecutive heartbeats is shown in Fig. 5. Accordingly, the speed profile will be adjusted again during last heartbeat shown in Fig. 5, beginning approximately at timepoint 1190. The thin vertical lines denote the recurring pattern which differentiates one heartbeat from the next heartbeat.

[0056] In addition, a time section for the set speed SS (dotted line) and the actual speed AS (black solid line) is shown in Fig. 6. As shown, during the initial phase which lasts until approximately timepoint 250, the set speed SS rather corresponds to the initial speed of 24,000 rpm. Thereafter, the actual speed AS of the drive unit 28 follows the set speed SS as laid down in the speed profile. However, during the first heartbeat between about timepoint 250 and 480 the inertia of the impeller 30 is not yet been accounted for. During the next heartbeat, the controller 16 already has accounted for the inertia of the impeller 30 and the actual speed AS closely follows the set speed SS.

[0057] In sum, this delivers an actual flow AF at the blood flow outlet 24 which virtually corresponds to the intended target flow TF of 4 l / min, see Fig. 7. In Fig. 7, the actual flow AF is denoted by a solid black line whereas the target flow TF is depicted by a dashed line. Of course, a certain deviation between the actual flow AF and the target flow TF is tolerable, as long as the deviation is within predefined limits. Hence, the adjustment of the speed profile may additionally or alternatively be carried out based on a mathematical cost function which is minimized. The controller 16 may be configured to computer statistical variability between the actual flow AF and the target flow TF. To do so, a suitable control error like standard deviation, standard error or root mean squared error is computed and maybe compared to predefined thresholds or acceptance intervals. As soon as the error dimension exceeds the threshold value or the acceptance interval the adjustment of the speed profile is carried out. In addition, the controller 16 may also be configured to adjust the speed profile at given time intervals e.g., for the first heartbeat after every five seconds. Furthermore, the controller 16 may be configured to apply a signal filter so that possible erroneous measurements are disregarded and do not cause an unnecessary adjustment of the speed profile. The signal filter may for instance be a low pass filter, a high pass filter, a band pass filter and / or a moving average filter.

[0058] EXEMPLARY IMPLEMENTATIONS

[0059] As already described, the technology described herein may be implemented in various ways. In that regard, the foregoing disclosure is intended to include, but not be limited to, the systems, methods, and combinations and subcombinations thereof that are set forth in the following exemplary implementations. Preferred embodiments are described in the following paragraphs:

[0060] A1 Blood pump system comprising: a blood pump, in particular an intravascular blood pump, having a pump housing with a blood flow inlet and a blood flow outlet connected by a passage, a pump element disposed in said pump housing, a drive unit configured to drive the pump element at an actual speed so that a flow is generated between the blood flow inlet and the blood flow outlet; a sensor arrangement configured to output pressure data comprising an indication for blood vessel pressure and / or an indication for ventricular pressure; and a controller; wherein the controller is further configured to adjust a speed profile controlling the actual speed of the drive unit based on the pressure data outputted by the sensor arrangement so that an actual flow at the blood flow outlet corresponds to a target flow.

[0061] A2 Blood pump system according to paragraph A1 , wherein the pump element is an impeller. A3 Blood pump system according to paragraph A1 or A2, wherein the sensor arrangement is configured to output pressure data comprising at least one of a pressure value relating to the pressure upstream of or at the blood flow inlet as an indication for the left ventricular pressure or a pressure value relating to the pressure downstream of or at the blood flow outlet as an indication for the aortic pressure.

[0062] A4 Blood pump system according to any one of the preceding paragraphs, wherein the blood pump comprises the sensor arrangement.

[0063] A5 Blood pump system according to paragraph A4, wherein the sensor arrangement comprises two sensors.

[0064] A6 Blood pump system according to paragraph A5, wherein one of the sensors is disposed in vicinity to the blood flow inlet and / or wherein the other one of the sensors is disposed in vicinity to the blood flow outlet.

[0065] A7 Blood pump system according to paragraph A5 or A6, wherein the sensors are optical sensors, in particular optical pressure sensors.

[0066] A8 Blood pump system according to any one of the preceding paragraphs A1 to A3, wherein the sensor arrangement is separate from the blood pump.

[0067] A9 Blood pump system according to any one of the preceding paragraphs A1 to A8, wherein the blood pump system further comprises a storage device.

[0068] A10 Blood pump system according to paragraph A9, wherein a characteristic diagram relating the pressure data to a flow of the drive unit is stored in the storage device.

[0069] A11 Blood pump system according to paragraph A10, wherein the controller is configured to read out an ideal speed from the characteristic diagram based on the pressure data and the target flow.

[0070] A12 Blood pump system according to paragraph A11 , wherein the controller is further configured to calculate a set speed of the speed profile based on the ideal speed and to set the actual speed to the set speed of the speed profile.

[0071] A13 Blood pump system according to paragraphs A12, wherein the controller is further configured to consider a speed offset based on the actual speed for calculation of the set speed.

[0072] A14 Blood pump system according to paragraph A13, wherein the controller is further configured to determine the ideal speed based on interpolation and extrapolation. A15 Blood pump system according to any one of the preceding paragraphs A10 to A14, wherein the characteristic diagram is an individual characteristic diagram for the specific blood pump.

[0073] A16 Blood pump system according to any one of the preceding paragraphs A10 to A14, wherein the characteristic diagram is a characteristic diagram for the type series of the blood pump or for a group of blood pumps within the type series of the blood pump.

[0074] A17 Blood pump system according to any one of the preceding paragraphs A10 to A16, wherein the characteristic diagram comprises a plurality of hydraulic flow curves for different speeds of the drive unit.

[0075] A18 Blood pump system according to any one of the preceding paragraphs A9 to A17, wherein the controller is further configured to store a time section of the set speed and / or a time section of the ideal speed and / or a time section of the actual speed and / or a time section of the pressure data in the storage device.

[0076] A19 Blood pump system according to paragraph A18, wherein the controller is further configured to determine an inertia of the pump element based on an analysis of the time section of the actual speed and / or the set speed and / or the time section of the pressure data and to consider the inertia of the pump element for calculation of the set speed.

[0077] A20 Blood pump system according to any one of the preceding paragraphs A1 to A19, wherein the controller is further configured to identify a recurring pattern in the pressure data.

[0078] A21 Blood pump system according to paragraph A20, wherein the recurring pattern is a pattern in the pressure signal indicating the ventricular pressure.

[0079] A22 Blood pump system according to paragraph A20 or A21 , wherein the recurring pattern is the minimum value at the end of the relaxation phase of the ventricle or wherein the recurring pattern is the maximum pressure gradient during the contraction phase at the beginning of the systole or wherein the recurring pattern may is the starting point of the contraction phase of the left ventricle, in particular the end-diastolic pressure point.

[0080] A23 Blood pump system according to any one of the preceding paragraphs A1 to A22, wherein the controller is further configured to repeat the adjustment of the speed profile based on optimizing a mathematical cost function and / or to adjust the speed profile at a predefined frequency, preferably to adjust the speed profile at a predefined frequency of the recurring pattern. A24 Blood pump system according to paragraph A24, wherein the controller is configured to compute a statistical dispersion or variability between an actual value and a set value, preferably between the actual flow and the target flow.

[0081] A25 Blood pump system according to any one of the preceding paragraphs A1 to A24, wherein the controller is further configured to apply a signal filter.

[0082] A26 Blood pump system according to any one of the preceding paragraphs A1 to A25, wherein the blood vessel pressure is the aortic pressure and / or wherein the ventricle pressure is the left ventricle pressure.

[0083] A27 Blood pump system according to paragraph A26, wherein the blood pump system is a left ventricular support blood pump system.

[0084] A28 Blood pump system according to any one of the preceding paragraphs A1 to A25, wherein the blood vessel pressure is the pulmonary artery pressure and / or wherein the blood vessel pressure is the central venous pressure and the ventricular pressure is the right ventricular pressure.

[0085] A29 Blood pump system according to paragraph A28, wherein the blood pump system is a right ventricular support blood pump system.

[0086] B1 Method for controlling the speed of a drive unit of a blood pump, in particular of an intravascular blood pump, wherein the blood pump comprises: a pump housing having a blood flow inlet and a blood flow outlet connected by a passage, a pump element disposed in said pump housing, a drive unit configured to drive the pump element at an actual speed so that a flow is generated between the blood flow inlet and the blood flow outlet; wherein the method comprises the following steps: receiving pressure data comprising an indication for blood vessel pressure and / or an indication for ventricular pressure; adjusting a speed profile controlling the actual speed of the drive unit based on the received pressure data so that an actual flow at the blood flow outlet corresponds to a target flow.

[0087] B2 Method according to paragraph B1 , wherein the pump element is an impeller.

[0088] B3 Method according to paragraph B1 or B2, wherein the step of receiving pressure data further comprises: receiving least one of a pressure relating to the pressure upstream of or at the blood flow inlet as an indication for the ventricular pressure or a pressure relating to the pressure downstream of or at the blood flow outlet as an indication for the blood vessel pressure. B4 Method according to any one of the preceding paragraphs B1 to B3, wherein the step of adjusting the speed profile further comprises: reading out an ideal speed based on the pressure data from a characteristic diagram relating the pressure data to the target flow.

[0089] B5 Method according to paragraph B4, wherein the step of adjusting the speed profile further comprises: calculating a set speed of the speed profile based on the ideal speed.

[0090] B6 Method according to paragraph B5, wherein the step of adjusting the speed profile further comprises: determining the ideal speed based on interpolation and extrapolation.

[0091] B7 Method according to any one of the preceding paragraphs B4 to B6, wherein the characteristic diagram is an individual characteristic diagram for the specific blood pump.

[0092] B8 Method according to any one of the preceding paragraphs B4 or B6, wherein the characteristic diagram is a characteristic diagram for the type series of the blood pump or for a group of blood pumps within the type series of the blood pump.

[0093] B9 Method according to any one of the preceding paragraphs B4 to B8, wherein the characteristic diagram comprises a plurality of hydraulic flow curves for different speeds of the drive unit.

[0094] B10 Method according to any one of the preceding paragraphs B5 to B9, wherein the step of adjusting the speed profile further comprises: setting the actual speed to the set speed of the speed profile.

[0095] B11 Method according to any one of the preceding paragraphs B5 to B10, wherein the step of calculating the set speed further comprises: considering a speed offset based on the actual speed.

[0096] B12 Method according to any one of the preceding paragraphs B1 to B11 , wherein the method further comprises: storing a time section of the set speed and / or a time section of the ideal speed and / or a time section of the actual speed and / or a time section of the pressure data.

[0097] B13 Method according to paragraph B12, wherein the step of calculating the set speed further comprises: determining an inertia of the pump element based on an analysis of the time section of the actual speed and / or the pressure data.

[0098] B14 Method according to paragraph B13, wherein the step of calculating the set speed further comprises: considering the inertia of the pump element for calculation of the set speed.

[0099] B15 Method according to any one of the preceding paragraphs B1 to B14, the method further comprises: identifying a recurring pattern in the pressure data. B16 Method according to paragraph B15, wherein the step of identifying a recurring pattern comprises: identifying a recurring pattern in the pressure signal indicating the ventricular pressure.

[0100] B17 Method according to paragraph B15 or B16, wherein the step of identifying a recurring pattern comprises: identifying the minimum value at the end of the relaxation phase of the left ventricle or identifying the maximum pressure gradient during the contraction phase at the beginning of the systole wherein the recurring pattern may is the starting point of the contraction phase of the left ventricle, in particular the end-diastolic pressure point.

[0101] B18 Method according to any one of the preceding paragraphs B1 to B17, wherein the method further comprises: adjusting the speed profile based on optimizing a mathematical cost function; and / or adjusting the speed profile at a predefined frequency, preferably adjusting the speed profile at a predefined frequency of the recurring pattern.

[0102] B19 Method according to paragraph B18, wherein the step of adjusting the speed profile based on optimizing the mathematical cost function further comprises: computing a statistical dispersion or variability between an actual value and a set value, preferably between the actual flow and the target flow.

[0103] B20 Method according to any one of the preceding paragraphs B1 to B19, wherein the method further comprises: applying a signal filter to the pressure data and / or the speed profile and / or the set speed.

[0104] B21 Method according to any one of the preceding paragraphs B1 to B20, wherein the blood vessel pressure is the aortic pressure and / or wherein the ventricle pressure is the left ventricle pressure.

[0105] B22 Method according to paragraph B21 , wherein the blood pump is a left ventricular support blood pump.

[0106] B23 Method according to any one of the preceding paragraphs B1 to B20, wherein the blood vessel pressure is the pulmonary artery pressure and / or wherein the blood vessel pressure is the central venous pressure and the ventricular pressure is the right ventricular pressure.

[0107] B24 Method according to paragraph B23, wherein the blood pump is a right ventricular support blood pump.

[0108] As utilized herein, the terms “approximately”, “about”, “substantially”, “virtually” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.

[0109] List of reference signs

[0110] 10 blood pump system

[0111] 12 blood pump

[0112] 14 sensor arrangement

[0113] 16 controller

[0114] 18 storage device

[0115] 20 pump housing

[0116] 22 blood flow inlet

[0117] 24 blood flow outlet

[0118] 26 passage

[0119] 28 drive unit

[0120] 30 impeller

[0121] 32 sensor

[0122] 34 sensor

[0123] AF actual flow

[0124] AOP aortic pressure

[0125] AS actual speed

[0126] CD characteristic diagram

[0127] LVP left ventricular pressure

[0128] P1-P9 hydraulic flow curves

[0129] SS set speed

[0130] TF target flow

Claims

CLAIMS Blood pump system (10) comprising: a blood pump (12), in particular an intravascular blood pump, having a pump housing (20) with a blood flow inlet (22) and a blood flow outlet (24) connected by a passage (26), an impeller (30) disposed in said pump housing (20), a drive unit (28) configured to drive the impeller (30) at an actual speed (AS) so that a flow is generated between the blood flow inlet (22) and the blood flow outlet (24); a sensor arrangement (14) configured to output pressure data comprising an indication for blood vessel pressure (AOP) and / or an indication for ventricular pressure (LVP); and a controller (16); wherein the controller (16) is further configured to adjust a speed profile controlling the actual speed (AS) of the drive unit (28) based on the pressure data outputted by the sensor arrangement (18) so that an actual flow (AF) at the blood flow outlet (24) corresponds to a target flow (TF). Blood pump system (10) according to claim 1 , wherein the sensor arrangement (14) is configured to output pressure data comprising at least one of a pressure value relating to the pressure upstream of or at the blood flow inlet (22) as an indication for the ventricular pressure (LVP) or a pressure value relating to the pressure downstream of or at the blood flow outlet (24) as an indication for the blood vessel pressure (AOP). Blood pump system (10) according to claim 1 or 2, wherein the blood pump system (10) further comprises a storage device (18), wherein a characteristic diagram (CD) relating the pressure data to a flow of the drive unit (28) is stored in the storage device (18), and wherein the controller (16) is configured to read out an ideal speed from the characteristic diagram (CD) based on the pressure data and the target flow (TF) and to calculate a set speed (SS) of the speed profile based on the ideal speed and to set the actual speed (AS) to the set speed (SS) of the speed profile. Blood pump system (10) according to claim 3, wherein the controller (16) is further configured to consider a speed offset based on the actual speed (AS) for calculation of the set speed (SS).Blood pump system (10) according to claim 3 to 4, wherein the controller (16) is further configured to store a time section of the set speed (SS) and / or a time section of the ideal speed and / or a time section of the actual speed (AS) and / or a time section of the pressure data in the storage device (18), preferably wherein the controller (16) is further configured to determine an inertia of the impeller (30) based on an analysis of the time section of the actual speed (AS) and / or the set speed (SS) and / or the time section of the pressure data and to consider the inertia of the impeller (30) for calculation of the set speed (SS). Blood pump system (10) according to any one of the preceding claims, wherein the controller (16) is further configured to identify a recurring pattern in the pressure data. Blood pump system (10) according to any one of the preceding claims, wherein the controller (16) is further configured to repeat the adjustment of the speed profile based on optimizing a mathematical cost function and / or to adjust the speed profile at a predefined frequency, preferably to adjust the speed profile at a predefined frequency of the recurring pattern. Method for controlling the speed of a drive unit (28) of a blood pump (12), in particular of an intravascular blood pump, wherein the blood pump (12) comprises: a pump housing (20) having a blood flow inlet (22) and a blood flow outlet (24) connected by a passage (26), an impeller (30) disposed in said pump housing (20), a drive unit (28) configured to drive the impeller (30) at an actual speed (AS) so that a flow is generated between the blood flow inlet (22) and the blood flow outlet (24); wherein the method comprises the following steps: receiving pressure data comprising an indication for blood vessel pressure (AOP) and / or an indication for ventricular pressure (LVP); adjusting a speed profile controlling the actual speed (AS) of the drive unit (28) based on the received pressure data so that an actual flow (AF) at the blood flow outlet (24) corresponds to a target flow (TF). Method according to claim 8, wherein the step of receiving pressure data further comprises: receiving least one of a pressure relating to the pressure upstream of or at the blood flow inlet (22) as an indication for the ventricular pressure (LVP) or a pressure relating to thepressure downstream of or at the blood flow outlet (24) as an indication for blood vessel pressure (AOP). Method according to claim 8 or 9, wherein the step of adjusting the speed profile further comprises: reading out an ideal speed based on the pressure data from a characteristic diagram (CD) relating the pressure data to the target flow (TF); calculating a set speed (SS) of the speed profile based on the ideal speed; and setting the actual speed (AS) to the set speed (SS) of the speed profile. Method according to claim 10, wherein the step of calculating the set speed (SS) further comprises: considering a speed offset based on the actual speed (AS). Method according to any one of the preceding claims 8 to 11 , wherein the method further comprises: storing a time section of the set speed (SS) and / or a time section of the ideal speed and / or a time section of the actual speed (AS) and / or a time section of the pressure data. Method according to claim 12, wherein the step of calculating the set speed (SS) further comprises: determining an inertia of the impeller (30) based on an analysis of the time section of the actual speed (AS) and / or the pressure data; and considering the inertia of the impeller (30) for calculation of the set speed (SS). Method according to any one of the preceding claims 8 to 13, the method further comprises: identifying a recurring pattern in the pressure data. Method according to any one of the preceding claims 8 to 14, wherein the method further comprises: adjusting the speed profile based on optimizing a mathematical cost function; and / or adjusting the speed profile at a predefined frequency, preferably adjusting the speed profile at a predefined frequency of the recurring pattern.

Images