Blood pump control using motor voltage measurement

Abstract

The percutaneous circulatory assist device includes an impeller, a motor configured to rotate the impeller to cause blood to flow through the percutaneous circulatory assist device, and a controller operatively coupled to the motor, the controller configured to determine a vascular pressure in the patient, an operating voltage applied to the motor to cause the motor to rotate the impeller, an operating speed of the motor resulting from applying the operating voltage to the motor, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed, and a cardiac function parameter based on the blood flow parameter.

Description

[Technical Field]

[0001] The present disclosure relates to a percutaneous circulatory assist system, and more particularly, to a percutaneous circulatory assist system that determines one or more cardiac performance parameters of a patient. [Background technology]

[0002] Percutaneous circulatory assist devices, or blood pumps, can provide temporary assistance for up to approximately several weeks to patients with reduced cardiac function or cardiac output. However, when using such devices, it is typically difficult for medical professionals to determine whether and when the amount of assistance provided by such devices should be changed, as well as when to terminate therapy. To assist medical professionals, estimates of cardiac function are provided by some devices. These estimates are derived in part from the operating parameters of these devices, particularly motor speed and torque. Percutaneous circulatory assist device motors typically lack on-board speed sensors (due to size constraints), and as a result, motor speed is typically estimated from fluctuations in motor current. Such current is typically measured using a series of resistors and an amplifier. These additional components can increase both the complexity and cost of these devices. Furthermore, such current measurements can be subject to error. Therefore, improved devices are needed. Summary of the Invention

[0003] In Example 1, a percutaneous circulatory assist device includes an impeller, a motor configured to rotate the impeller to cause blood to flow through the percutaneous circulatory assist device, and a controller operably coupled to the motor, the controller configured to determine a patient's vascular pressure, an operating voltage applied to the motor to cause the motor to rotate the impeller, an operating speed of the motor resulting from supplying the operating voltage to the motor, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed, and a cardiac function parameter based on the blood flow parameter.

[0004] In Example 2, the percutaneous circulatory assist system of Example 1 further comprises a pressure sensor operably coupled to the controller, the controller configured to determine vascular pressure within the patient via the pressure sensor.

[0005] In Example 3, in the percutaneous circulatory assist system of Example 16 or Example 2, the controller determines the blood flow parameter using a mathematical function including vascular pressure, actuation voltage, and actuation speed. In Example 4, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the square of the vascular pressure.

[0006] In Example 5, in the percutaneous circulatory assist system of Example 19 or Example 4, the mathematical function includes the square of the actuation voltage. In Example 6, the percutaneous circulatory assist system of any one of Examples 19-5, wherein the mathematical function includes a square of the actuation rate.

[0007] In Example 7, the percutaneous circulatory assist system of any one of Examples 19-6, wherein the mathematical function includes the product of vascular pressure and actuation voltage. In Example 8, the percutaneous circulatory assist system of any one of Examples 19-7, wherein the mathematical function includes the product of vascular pressure and actuation speed.

[0008] In Example 9, the percutaneous circulatory assist system of any one of Examples 19-8, wherein the mathematical function includes the product of the actuation voltage and the actuation rate. In Example 10, in the percutaneous circulatory assist system of any one of Examples 19-9, the mathematical function includes a product of vascular pressure, actuation voltage, and actuation rate.

[0009] Example 11 is a method of operating a percutaneous circulatory assist device, the device comprising: an impeller; a motor configured to rotate the impeller to generate blood flow within a patient; and a controller operably coupled to the motor, the method comprising: determining, via the controller, a vascular pressure of the patient; determining, via the controller, an operating voltage to be applied to the motor to cause the motor to rotate the impeller; determining, via the controller, an operating speed of the motor resulting from applying the operating voltage to the motor; determining, via the controller, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed; and determining, via the controller, a cardiac function parameter based on the blood flow parameter.

[0010] In Example 12, the method of Example 27 further comprises altering operation of the percutaneous circulatory assist device based on the cardiac function parameter. In Example 13, the method of Example 27 or Example 12 further comprises determining, via the controller, a contractility of the patient's cardiac function by varying an operating speed of the motor.

[0011] In Example 14, the method of any one of Examples 27-13 further comprises dividing the waveform of the actuation voltage via the controller. In Example 15, the method of any one of Examples 27-14, wherein determining the blood flow parameter via the controller includes using a mathematical function including the vascular pressure, the actuation voltage, and the actuation speed.

[0012] In Example 16, a percutaneous circulatory assist device includes a housing configured to be placed within a patient, an impeller carried within the housing, a motor configured to rotate the impeller relative to the housing to cause blood to flow through the housing, and a controller operably coupled to the motor, the controller configured to determine the patient's vascular pressure, an operating voltage applied to the motor to cause the motor to rotate the impeller, an operating speed of the motor resulting from supplying the operating voltage to the motor, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed, and a cardiac function parameter based on the blood flow parameter.

[0013] In Example 17, the percutaneous circulatory assist system of Example 16 further comprises a pressure sensor operably coupled to the controller, the controller configured to determine vascular pressure within the patient via the pressure sensor.

[0014] In Example 18, the percutaneous circulatory assist system of Example 16, wherein the motor comprises a plurality of motor windings, and the controller is configured to determine an operating speed of the motor based on voltage fluctuations across the plurality of motor windings.

[0015] In Example 19, in the percutaneous circulatory assist system of Example 16, the controller determines the blood flow parameters using a mathematical function including vascular pressure, actuation voltage, and actuation speed. In Example 20, in the percutaneous circulatory assist system of Example 19, the mathematical function includes a square of the vascular pressure.

[0016] In Example 21, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the square of the actuation voltage. In Example 22, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the square of the actuation rate.

[0017] In Example 23, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the product of vascular pressure and actuation voltage. In Example 24, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the product of vascular pressure and actuation speed.

[0018] In Example 25, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the product of the actuation voltage and the actuation rate. In Example 26, in the percutaneous circulatory assist system of Example 19, the mathematical function includes the product of vascular pressure, actuation voltage, and actuation rate.

[0019] Example 27 is a method of operating a percutaneous circulatory assist device placed within a patient, the device comprising: an impeller; a motor configured to rotate the impeller to generate blood flow within the patient; and a controller operably coupled to the motor, the method comprising: determining, via the controller, a vascular pressure within the patient; determining, via the controller, an operating voltage to be applied to the motor to cause the motor to rotate the impeller; determining, via the controller, an operating speed of the motor resulting from supplying the operating voltage to the motor; determining, via the controller, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed; and determining, via the controller, a cardiac function parameter based on the blood flow parameter.

[0020] In Example 28, the method of Example 27 further comprises altering operation of the percutaneous circulatory assist device based on the cardiac function parameter. In Example 29, the method of Example 27 further comprises determining, via the controller, a contractility of the patient's cardiac function by varying an operating speed of the motor.

[0021] In Example 30, the method of Example 27 further comprises, via the controller, dividing the waveform of the actuation voltage. In Example 31, a percutaneous circulatory assist device includes a housing configured to be placed within a patient, an impeller carried within the housing, a motor configured to rotate the impeller relative to the housing to force blood through the housing, and a controller operably coupled to the motor, the controller configured to determine an operating voltage applied to the motor to cause the motor to rotate the impeller, a blood flow parameter using a mathematical function including the square of the operating voltage, and a cardiac function parameter based on the blood flow parameter.

[0022] In Example 32, the percutaneous circulatory assist system of Example 31, wherein the controller is further configured to determine a vascular pressure within the patient, and the mathematical function further includes a square of the vascular pressure. In Example 33, in the percutaneous circulatory assist system of Example 31, the controller is further configured to determine an actuation speed of the motor resulting from supplying an actuation voltage to the motor, and the mathematical function further includes a square of the actuation speed.

[0023] In Example 34, the percutaneous circulatory assist system of Example 31, wherein the controller is further configured to determine a vascular pressure within the patient, and the mathematical function further comprises a product of the vascular pressure and the actuation voltage.

[0024] In Example 35, in the percutaneous circulatory assist system of Example 31, the controller is further configured to determine a vascular pressure in the patient and an actuation speed of the motor resulting from supplying an actuation voltage to the motor, and the mathematical function further includes a product of the vascular pressure, the actuation voltage, and the actuation speed.

[0025] While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. [Brief explanation of the drawings]

[0026] [Figure 1]1 is a side cross-sectional view of an exemplary percutaneous circulatory assist device (also referred to interchangeably herein as a "blood pump") according to an embodiment of the subject matter disclosed herein. [Figure 2] FIG. 2 is a schematic diagram of electronic components of the percutaneous circulatory assist device of FIG. 1 according to an embodiment of the subject matter disclosed herein. [Figure 3] 1 is a flow diagram of an exemplary method of operating a percutaneous circulatory assist device and determining one or more cardiac function parameters of a patient, according to an embodiment of the subject matter disclosed herein.

[0027] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the specific embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1 illustrates a partial side cross-sectional view of an exemplary percutaneous circulatory assist device 100 (interchangeably referred to herein as a "blood pump") according to an embodiment of the subject matter disclosed herein. Device 100 may form part of a percutaneous circulatory assist device, for example, along with a guidewire and introducer sheath (not shown), among other devices. More particularly, the guidewire and introducer sheath may facilitate percutaneous delivery of device 100 to a target location within a patient, for example, into the patient's heart. Alternatively, device 100 may be delivered to a different target location within the patient.

[0029] 1 , device 100 generally includes housing 101, which includes impeller housing 102 and motor housing 104. In some embodiments, impeller housing 102 and motor housing 104 may be integrally or monolithically constructed. In other embodiments, impeller housing 102 and motor housing 104 may be separate components configured to be removably or permanently coupled. In certain embodiments, blood pump 100 may lack a separate motor housing 104, and impeller housing 102 may be directly coupled to motor 105, described below, or motor housing 104 may be integrally constructed with motor 105, described below.

[0030] The impeller housing 102 carries an impeller assembly 106 therein. The impeller assembly 106 includes an impeller shaft 108 rotatably supported by at least one bearing, such as bearing 110. The impeller assembly 106 also includes an impeller 112 that rotates relative to the impeller housing 102 to pump blood through the device 100. More specifically, the impeller 112 flows blood from a blood inlet 114 formed on the impeller housing 102, through the impeller housing 102, and out a blood outlet 116 formed on the impeller housing 102. In certain embodiments, and as shown, the impeller shaft 108 and the impeller 112 may be separate components; in other embodiments, the impeller shaft 108 and the impeller 112 may be integrated. In some embodiments, and as shown, the inlet 114 and / or the outlet 116 may each include multiple openings. In other embodiments, inlet 114 and / or outlet 116 may each include a single opening. In some embodiments, and as shown, inlet 114 may be formed on an end of impeller housing 102 and outlet 116 may be formed on a side of impeller housing 102. In other embodiments, inlet 114 and / or outlet 116 may be formed on other portions of impeller housing 102. In certain embodiments, impeller housing 102 may be coupled with a distally extending cannula (not shown), which may receive and deliver blood to inlet 114.

[0031] 1 , motor housing 104 carries motor 105, which is configured to rotatably drive impeller 112 relative to impeller housing 102. In the embodiment shown, motor 105 rotates drive shaft 120, which is coupled to drive magnet 122. Rotation of drive magnet 122 causes rotation of driven magnet 124, which is coupled to impeller assembly 106 and rotates therewith. More particularly, in embodiments incorporating impeller shaft 108, impeller shaft 108 and impeller 112 are configured to rotate with driven magnet 124. In other embodiments, motor 105 may be coupled to impeller assembly 106 via other components.

[0032] The motor housing 104 couples to a catheter 126 on the opposite side of the impeller housing 102. The catheter 126 may be coupled to the motor housing 104 in a variety of ways, for example, by laser welding, soldering, etc. The catheter 126 extends proximally away from the motor housing 104. The catheter 126 carries a motor cable 128 within a main lumen 130, which may operably couple the motor 105 to a controller (shown elsewhere) and / or a power source (shown elsewhere).

[0033] With continued reference to FIG. 1 and with additional reference to FIG. 2, controller 132 may be operatively coupled to motor 105 and configured to control motor 105. In some embodiments, controller 132 may be located within motor housing 104. In other embodiments, controller 132 may be located outside motor housing 104 (e.g., in a separate housing, etc.) and coupled to motor 105 via motor cable 128. In some embodiments, controller 132 may include multiple components, one or more of which may be located within motor housing 104. According to embodiments, controller 132 may be, include, or may include one or more field programmable gate arrays (FPGAs), one or more programmable logic devices (PLDs), one or more complex PLDs (CPLDs), one or more custom application specific integrated circuits (ASICs), one or more special purpose processors (e.g., microprocessors), one or more central processing units (CPUs), software, hardware, firmware, or any combination thereof and / or other components. Although controller 132 is referred to in the singular herein, the controller may be implemented in multiple instances, distributed across multiple computing devices, instantiated within multiple virtual machines, for example. In other embodiments, motor 105 may be controlled in other manners. Controller 132 may be operatively coupled to power source 134.

[0034] Pressure sensor 136 may be operatively coupled to controller 132. Pressure sensor 136 measures the pressure of fluid, e.g., blood, within the patient's heart or blood vessels, e.g., the aorta (vascular pressure). Pressure sensor 136 may be located outside or inside housing 101 or on catheter 126. Pressure sensor 136 may be, for example, an optical or electrical pressure sensor. As described in further detail below, controller 132 determines the vascular pressure within the patient via pressure sensor 136.

[0035] Generally, controller 132 is configured to determine one or more cardiac function parameters based on one or more device performance parameters. Such device performance parameters may include, for example, pressure sensed by pressure sensor 136, operating voltage applied to motor 105, and operating / output speed of motor 105. Cardiac function parameters may include, for example, cardiac output, cardiac output, left ventricular pressure, aortic pressure, heart rate, mean aortic pressure, systolic blood pressure, diastolic blood pressure, left ventricular end-diastolic pressure ("LVEDP," the minimum pressure in the left ventricle that may be associated with a particular point on the pressure waveform of device 100), pulse pressure, stroke volume, load status, and / or volume loading status. Cardiac function parameters, or changes in cardiac function parameters, may provide an indication of cardiac health. Thus, the cardiac function parameters may be provided to a medical professional (e.g., via a display (not shown) operably coupled to controller 132), who may then modify device operation (e.g., device position, motor operating speed, and, consequently, blood flow through device 100) to alter the patient's therapy. Alternatively, device 100 may automatically modify operation based on the cardiac function parameters. More particularly, device 100 may follow a predetermined profile to reduce the assistance provided by device 100 to the patient.

[0036] 3 , in some embodiments, controller 132 is configured to determine one or more cardiac function parameters as follows. First, in block 300, controller 132 determines one or more cardiac function parameters, more specifically, a vascular pressure within the patient, an operating voltage applied to motor 105, and an operating speed of motor 105. In some embodiments, the vascular pressure determined by controller 132 is an aortic pressure. In some embodiments, controller 132 determines the vascular pressure within the patient via pressure sensor 136. In some embodiments, controller 132 determines the operating speed of motor 105 by analyzing voltage fluctuations on the windings of motor 105, using known techniques for controlling sensorless motors. Next, in block 302, controller 132 inputs the pressure, operating voltage, and operating speed into a mathematical function to determine a blood flow parameter, such as blood flow rate through device 100. In some embodiments, the mathematical function is a sum of various terms including pressure, operating voltage applied to motor 105, and operating speed of motor 105. Such terms may include the square of the pressure, the square of the actuation voltage and / or the square of the actuation speed, and / or the product of the pressure, actuation voltage and / or actuation speed. More particularly, the function may be a polynomial function, for example the following polynomial function:

[0037]

number

[0038] where flow in the function is the blood flow rate through device 100, a0, a1, b0, b1, c0, c1, d, e, f, g, and k are coefficients, and p, v, and s are pressure, voltage, and speed, respectively. In some embodiments, the coefficients are based on the particular pump, motor, and controller. The coefficients also depend on the units of measure of the terms involved. Generally, coefficients of higher-order terms are between −1 and 1, while coefficients of first-order terms may be larger. In some embodiments, the polynomial function may include various higher-order terms, although such terms do not significantly affect the calculated flow rate. Similarly, in some embodiments, the polynomial may include exponential or trigonometric terms. Whether these additional terms should be included can be determined by comparing the predicted flow rate with flow data collected in a controlled test, and any differences between the two values ​​are compared with available parameters or combinations of available parameters. In block 304, controller 132 determines cardiac function parameters using the calculated blood flow rate, in addition to pressure. In particular, the effect on cardiac output and cardiac output can be estimated using aortic pressure and the additional blood flow provided by the pump. Such determinations can also be based on sensed pressure, pulse, and anatomical data provided by the operator. The cardiac function parameter can be, for example, any of the parameters listed above, and the operation of the device can be altered based on that parameter.

[0039] In some embodiments, controller 132 is configured to determine the contractility of cardiac function by varying the speed of motor 105, and more particularly, by pulsing the speed of motor 105 over one cycle (heart beat) or multiple cycles. Once determined, contractility contributes to cardiac output; that is, device 100 effectively self-calibrates its determination of cardiac output during operation.

[0040] In some embodiments, controller 132 is configured to segment the voltage waveform and isolate cardiac cycles for analysis. Controller 132 may analyze the waveform to determine if it substantially matches a known model, which may indicate that device 100 is properly positioned within the patient. Controller 132 may additionally or alternatively analyze the waveform to determine if one or more portions of the waveform exceed a threshold, which may indicate the occurrence of a pump occlusion. More specifically, the steady-state portion of the voltage waveform (near zero Hertz) may be used to detect an occluded blood inlet when the voltage drops below a threshold specific to the pump and impeller design.

[0041] In some embodiments, motor 105 operates at a speed selected by a healthcare professional, and motor 105 is driven by a variable voltage to provide various levels of cardiac assistance. In other words, the healthcare professional selects the motor speed based on the analyzed cardiac function and the healthcare professional's judgment of how much blood flow is needed in addition to the unassisted cardiac output.

[0042] (example) As a hypothetical example, percutaneous circulatory assist device 100 is positioned within a patient, and more particularly, across the aortic valve in both the aorta and the left ventricle. Controller 132 then determines a vascular pressure of 123 mmHg, a motor operating voltage of 6.95 V, and a motor operating speed of 29,000 RPM. Controller 132 then calculates the pressure, operating voltage, operating speed, and the following coefficients in the above functions: a is 4.4065*10 -5 L / (min*mmHg 2 ), a1 is -2.0249*10 -3 L / (min*mmHg), b0 is 3.0318*10 -1 L / (min*V 2 ), b1 is 2.9707L / (min*V), c0 is 4.39*10 -8 L / (min*RPM 2 ), c1 is -7.039*10 -4 L / (min*RPM), d is 1.1678*10 -2L / (min*mmHg*V), e is -3.5599*10 -6 L / (min*mmHg*RPM), f is -2.4583*10 -4 L / (min*V*RPM), g is 0.0L / (min*mmHg*V*RPM), and k is 7.1132*10 -1 L / min to determine a blood flow rate of 0.66 L / min. Using the calculated blood flow rate, controller 132 determines the pump's effect on cardiac output, which in this case means 0.66 L / min * 90.3 mmHg / 451.1 = 0.13, or 13% of the normalized cardiac output, was added to the patient's baseline cardiac output.

[0043] Various modifications and additions may be made to the exemplary embodiments described without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not have all of the described features. Accordingly, the scope of the present invention is intended to encompass all such alternatives, modifications, and variations that fall within the scope of the claims, together with their equivalents.

Claims

1. A percutaneous circulatory assist device, comprising: The impeller and a motor configured to rotate the impeller to drive blood through the percutaneous circulatory assist device; a controller operably coupled to the motor, The patient's vascular pressure; an operating voltage applied to the motor to cause the motor to rotate the impeller; an operating speed of the motor resulting from supplying the operating voltage to the motor; and a blood flow parameter based on the vascular pressure, the actuation voltage, and the actuation speed; a controller configured to determine a cardiac function parameter based on the blood flow parameter; A percutaneous circulatory assist device comprising:

2. further comprising a pressure sensor operably coupled to the controller; the controller is configured to determine the vascular pressure within the patient via the pressure sensor. The percutaneous circulatory assist system according to claim 1 .

3. the controller determines the blood flow parameter using a mathematical function including the vascular pressure, the actuation voltage, and the actuation speed. The percutaneous circulatory assist system according to claim 1 or 2.

4. the mathematical function includes the square of the vascular pressure; The percutaneous circulatory assist system according to claim 3 .

5. the mathematical function includes the square of the actuation voltage; The percutaneous circulation assist system according to claim 3 or 4.

6. the mathematical function includes the square of the actuation speed; The percutaneous circulation assist system according to any one of claims 3 to 5.

7. the mathematical function includes the product of the vascular pressure and the actuation voltage; The percutaneous circulation assist system according to any one of claims 3 to 6.

8. the mathematical function includes the product of the vascular pressure and the actuation speed; The percutaneous circulatory assist system according to any one of claims 3 to 7.

9. the mathematical function includes the product of the actuation voltage and the actuation speed; The percutaneous circulation assist system according to any one of claims 3 to 8.

10. the mathematical function includes the product of the vascular pressure, the actuation voltage, and the actuation speed; The percutaneous circulation assist system according to any one of claims 3 to 9.

11. 1. A method of operating a percutaneous circulatory assist device, the device comprising: an impeller; a motor configured to rotate the impeller to induce blood flow in a patient; and a controller operatively coupled to the motor, the method comprising: determining, via said controller, a vascular pressure within the patient; determining, via the controller, an operating voltage to be applied to the motor to cause the motor to rotate the impeller; determining an operating speed of the motor resulting from supplying the operating voltage to the motor via the controller; determining, via the controller, a blood flow parameter based on the vascular pressure, the actuation voltage, and the actuation speed; determining, via the controller, a cardiac function parameter based on the blood flow parameter; A method comprising:

12. further comprising modifying operation of the percutaneous circulatory assist device based on the cardiac function parameter. The method of claim 11.

13. and determining, via the controller, a contractility of the patient's heart function by varying the operating speed of the motor.

13. The method of claim 11 or 12.

14. further comprising dividing the waveform of the actuation voltage via the controller. The method according to any one of claims 11 to 13.

15. determining the blood flow parameter via the controller includes using a mathematical function including the vascular pressure, the actuation voltage, and the actuation speed; The method according to any one of claims 11 to 14.

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