Blood pump control with motor voltage measurements

Abstract

A percutaneous circulation support device includes an impeller, a motor configured to rotate the impeller to flow blood through the percutaneous circulation support device, and a controller operably coupled to the motor. The controller is configured to determine a vascular pressure within the patient, an operating voltage applied to the motor to cause the motor to rotate the impeller, an operating speed of the motor caused by providing the operating voltage to the motor, a blood flow parameter based on the vascular pressure, the operating voltage, and the operating speed, and a heart performance parameter based on the blood flow parameter.

Description

[0001] Cross - reference to related patent applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 427,527, filed on November 23, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to percutaneous circulatory support systems. More particularly, the present disclosure relates to a percutaneous circulatory support device for determining one or more cardiac performance parameters of a patient. Background Art

[0004] Percutaneous circulatory support devices or blood pumps can provide transient support for up to approximately several weeks to patients with impaired cardiac function or cardiac output. However, when using such devices, it is often difficult for medical practitioners to determine whether the amount of support provided by such devices should be adjusted and when to adjust it, and to determine when treatment should be terminated. To assist medical practitioners, assessment values of cardiac performance are provided by some devices. These assessment values are obtained in part from the operating parameters of these devices, particularly motor speed and torque. The motors of percutaneous circulatory support devices typically do not have an onboard speed sensor (due to size limitations), so motor speed is typically estimated based on fluctuations in motor current. Such current is typically measured using a series of resistors and amplifiers. These additional components can increase both the complexity and cost of these devices. In addition, such current measurements can be error-prone. Accordingly, there is a need for improved devices. Summary of the Invention

[0005] In Example 1, a percutaneous circulatory support device includes: an impeller; a motor configured to rotate the impeller to cause blood to flow through the percutaneous circulatory support device; and a controller operably coupled to the motor, the controller configured to determine: a vascular pressure in a patient's body, a working voltage applied to the motor to cause the motor to rotate the impeller, a working speed of the motor resulting from providing the working voltage to the motor, a blood flow parameter based on the vascular pressure, the working voltage, and the working speed, and a cardiac performance parameter based on the blood flow parameter.

[0006] In Example 2, the percutaneous circulatory support device according to Example 1 further includes a pressure sensor operably coupled to the controller, wherein the controller is configured to determine the vascular pressure in the patient's body via the pressure sensor.

[0007] In Example 3, the percutaneous circulatory support device according to any one of Examples 1 or 2, wherein the controller determines the blood flow parameter by using a mathematical function that includes the vascular pressure, the working voltage, and the working speed.

[0008] In Example 4, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the square of the vascular pressure.

[0009] In Example 5, the percutaneous circulatory support device according to any one of Examples 19 or 4, wherein the mathematical function includes the square of the operating voltage.

[0010] In Example 6, the percutaneous circulatory support device according to any one of Examples 19 to 5, wherein the mathematical function includes the square of the operating speed.

[0011] In Example 7, the percutaneous circulatory support device according to any one of Examples 19 to 6, wherein the mathematical function includes the product of the vascular pressure and the operating voltage.

[0012] In Example 8, the percutaneous circulatory support device according to any one of Examples 19 to 7, wherein the mathematical function includes the product of the vascular pressure and the operating speed.

[0013] In Example 9, the percutaneous circulatory support device according to any one of Examples 19 to 8, wherein the mathematical function includes the product of the operating voltage and the operating speed.

[0014] In Example 10, the percutaneous circulatory support device according to any one of Examples 19 to 9, wherein the mathematical function includes the product of the vascular pressure, the operating voltage, and the operating speed.

[0015] In Example 11, a method of operating a percutaneous circulatory support device, the device including: an impeller, a motor configured to rotate the impeller to cause blood to flow in a patient, and a controller operably coupled to the motor, the method including: determining, via the controller, a vascular pressure in the patient; determining, via the controller, an operating voltage applied to the motor to rotate the impeller; determining, via the controller, an operating speed of the motor resulting from providing 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 performance parameter based on the blood flow parameter.

[0016] In Example 12, the method according to Example 27, further comprising adjusting the operation of the percutaneous circulatory support device based on the cardiac performance parameter.

[0017] In Example 13, the method according to any one of Examples 27 or 12, further comprising determining, via the controller, the contractility of the patient's cardiac function by changing the operating speed of the motor.

[0018] In Example 14, the method according to any one of Examples 27 to 13, further comprising segmenting, via the controller, the waveform of the operating voltage.

[0019] In Example 15, according to the method of any one of Examples 27 to 14, wherein determining the blood flow parameter via the controller includes using a mathematical function that includes vascular pressure, operating voltage, and operating speed.

[0020] In Example 16, the percutaneous circulatory support device includes: a housing configured to be located 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 being configured to determine: the vascular pressure within the patient, the operating voltage applied to the motor to rotate the impeller, the operating speed of the motor caused by applying the operating voltage to the motor, a blood flow parameter based on the vascular pressure, operating voltage, and operating speed, and a cardiac performance parameter based on the blood flow parameter.

[0021] In Example 17, the percutaneous circulatory support device according to Example 16 further includes a pressure sensor operably coupled to the controller, wherein the controller is configured to determine the vascular pressure within the patient via the pressure sensor.

[0022] In Example 18, the percutaneous circulatory support device according to Example 16, wherein the motor includes a plurality of motor windings, and the controller is configured to determine the operating speed of the motor based on voltage fluctuations of the plurality of motor windings.

[0023] In Example 19, the percutaneous circulatory support device according to Example 16, wherein the controller determines the blood flow parameter by using a mathematical function that includes vascular pressure, operating voltage, and operating speed.

[0024] In Example 20, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the square of the vascular pressure.

[0025] In Example 21, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the square of the operating voltage.

[0026] In Example 22, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the square of the operating speed.

[0027] In Example 23, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the product of the vascular pressure and the operating voltage.

[0028] In Example 24, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the product of the vascular pressure and the operating speed.

[0029] In Example 25, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the product of the operating voltage and the operating speed.

[0030] In Example 26, the percutaneous circulatory support device according to Example 19, wherein the mathematical function includes the product of vascular pressure, operating voltage, and operating speed.

[0031] In Example 27, a method of operating a percutaneous circulatory support device located within a patient, the device including: an impeller; a motor configured to rotate the impeller to cause blood to flow within the patient; and a controller operably coupled to the motor, the method including: determining, via the controller, the vascular pressure within the patient; determining, via the controller, the operating voltage applied to the motor to rotate the impeller; determining, via the controller, the operating speed of the motor caused by providing the operating voltage to the motor; determining, via the controller, a blood flow parameter based on the vascular pressure, operating voltage, and operating speed; and determining, via the controller, a cardiac performance parameter based on the blood flow parameter.

[0032] In Example 28, the method according to Example 27, further comprising adjusting the operation of the percutaneous circulatory support device based on the cardiac performance parameter.

[0033] In Example 29, the method according to Example 27, further comprising determining, via the controller, the contractility of the patient's cardiac function by changing the operating speed of the motor.

[0034] In Example 30, the method according to Example 27, further comprising segmenting, via the controller, the waveform of the operating voltage.

[0035] In Example 31, a percutaneous circulatory support device includes: a housing configured to be located 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 operating voltage applied to the motor to rotate the impeller, determine a blood flow parameter using a mathematical function including the square of the operating voltage, and determine a cardiac performance parameter based on the blood flow parameter.

[0036] In Example 32, the percutaneous circulatory support device according to Example 31, wherein the controller is further configured to determine the vascular pressure within the patient, and the mathematical function further includes the square of the vascular pressure.

[0037] In Example 33, the percutaneous circulatory support device according to Example 31, wherein the controller is further configured to determine the operating speed of the motor caused by providing the operating voltage to the motor, and the mathematical function further includes the square of the operating speed.

[0038] In Example 34, the percutaneous circulatory support device according to Example 31, wherein the controller is further configured to determine the vascular pressure within the patient, and the mathematical function further includes the product of the vascular pressure and the operating voltage.

[0039] In Example 35, the percutaneous circulatory support device according to Example 31, wherein the controller is further configured to determine: the vascular pressure in the patient; the operating speed of the motor caused by providing an operating voltage to the motor; and wherein the mathematical function further includes the product of the vascular pressure, the operating voltage, and the operating speed.

[0040] Although multiple embodiments are disclosed, other embodiments of the present invention will be apparent to those skilled in the art from the following detailed description, which illustrates and describes exemplary embodiments of the present invention. Accordingly, the drawings and the detailed description are to be regarded as illustrative rather than restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a side cross-sectional view of an exemplary percutaneous circulatory support device (also interchangeably referred to herein as a "blood pump") according to an embodiment of the subject matter disclosed herein.

[0042] Figure 2 is according to an embodiment of the subject matter disclosed herein Figure 1 a schematic diagram of the electronic components of the percutaneous circulatory support device in

[0043] Figure 3 is a flow chart of an exemplary method of operating a percutaneous circulatory support device and determining one or more cardiac performance parameters of a patient according to an embodiment of the subject matter disclosed herein.

[0044] Although the present invention may be modified to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. However, the present invention is not limited to the specific embodiments described. Instead, the present invention is intended to cover all modifications, equivalents, and alternative forms falling within the scope of the present invention as defined by the appended claims. DETAILED DESCRIPTION

[0045] Figure 1 depicts a partial side cross-sectional view of an exemplary percutaneous circulatory support device 100 (also interchangeably referred to herein as a "blood pump") according to an embodiment of the subject matter disclosed herein. The device 100 may form part of a percutaneous circulatory support system together with, for example, a guide wire and a introducer sheath (not shown). More specifically, the guide wire and the introducer sheath may facilitate percutaneous delivery of the device 100 to a target location within the patient's body, such as within the patient's heart. Alternatively, the device 100 may be delivered to different target locations within the patient's body.

[0046] Continuing to refer Figure 1, the device 100 generally includes a housing 101, and the housing 101 includes an impeller housing 102 and a motor housing 104. In some embodiments, the impeller housing 102 and the motor housing 104 may be integrally or monolithically formed. In other embodiments, the impeller housing 102 and the motor housing 104 may be separate components configured to be removably or permanently coupled. In some embodiments, the blood pump 100 may not have a separate motor housing 104, and the impeller housing 102 may be directly coupled to the motor 105 described below, or the motor housing 104 may be integrally formed with the motor 105 described below.

[0047] The impeller housing 102 houses the impeller assembly 106 therein. The impeller assembly 106 includes an impeller shaft 108, and the impeller shaft 108 is rotatably supported by at least one bearing (such as bearing 110). The impeller assembly 106 further includes an impeller 112, and the impeller 112 rotates relative to the impeller housing 102 to drive blood through the device 100. More specifically, the impeller 112 causes blood to flow from a blood inlet 114 formed on the impeller housing 102 through the impeller housing 102 and out of a blood outlet 116 formed on the impeller housing 102. In some embodiments and as shown, the impeller shaft 108 and the impeller 112 may be separate components; and 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 a plurality of orifices. In other embodiments, the inlet 114 and / or the outlet 116 may each include a single orifice. In some embodiments and as shown, the inlet 114 may be formed on an end portion of the impeller housing 102, and the outlet 116 may be formed on a side portion of the impeller housing 102. In other embodiments, the inlet 114 and / or the outlet 116 may be formed on other portions of the impeller housing 102. In some embodiments, the impeller housing 102 may be coupled to a cannula (not shown) extending distally, and the cannula may receive blood and deliver it to the inlet 114.

[0048] Continuing to refer Figure 1 , the motor housing 104 houses the motor 105, and the motor 105 is configured to rotatably drive the impeller 112 relative to the impeller housing 102. In the illustrated embodiment, the motor 105 rotates a drive shaft 120, and the drive shaft 120 is coupled to a drive magnet 122. The rotation of the drive magnet 122 causes the rotation of a driven magnet 124, and the driven magnet 124 is connected to and rotates with the impeller assembly 106. More specifically, in embodiments incorporating the impeller shaft 108, the impeller shaft 108 and the impeller 112 are configured to rotate with the driven magnet 124. In other embodiments, the motor 105 may be coupled to the impeller assembly 106 via other components.

[0049] The motor housing 104 is oppositely coupled to the impeller housing 102 and is coupled to the conduit 126. The conduit 126 can be coupled to the motor housing 104 in various ways, such as by laser welding, brazing, etc. The conduit 126 extends proximally away from the motor housing 104. The conduit 126 carries the motor cable 128 within the main lumen 130, and the motor cable 128 can operably couple the motor 105 to a controller (shown elsewhere) and / or a power source (shown elsewhere).

[0050] Continuing to refer Figure 1 And additionally referring Figure 2 to, the controller 132 is operably coupled to the motor 105 and is configured to control the motor 105. In some embodiments, the controller 132 can be disposed within the motor housing 104. In other embodiments, the controller 132 can be disposed outside the motor housing 104 (e.g., disposed in a separate housing, etc.) and is coupled to the motor 105 via the motor cable 128. In some embodiments, the controller 132 can include multiple components, and one or more of these components can be disposed within the motor housing 104. According to an embodiment, the controller 132 can be, can include, or can be included in 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 dedicated processors (e.g., microprocessors), one or more central processing units (CPUs), software, hardware, firmware, or any combination of these and / or other components. Although the controller 132 is referred to herein in the singular, the controller can be implemented as multiple entities, distributed across multiple computing devices, instantiated within multiple virtual machines, etc. In other embodiments, the motor 105 can be controlled in other ways. The controller 132 is operably coupled to the power source 134.

[0051] The pressure sensor 136 can be operably coupled to the controller 132. The pressure sensor 136 measures the fluid (i.e., blood) pressure within the patient's heart or blood vessel ("vascular pressure"), e.g., the fluid pressure within the aorta. The pressure sensor 136 can be located outside or within the housing 101, or on the conduit 126. The pressure sensor 136 can be, for example, an optical or an electrical pressure sensor. As described in more detail below, the controller 132 determines the vascular pressure within the patient's body via the pressure sensor 136.

[0052] Generally, controller 132 is configured to determine one or more cardiac performance parameters based on one or more device performance parameters. Such device performance parameters may include, for example, the pressure sensed by pressure sensor 136, the operating voltage applied to motor 105, and the operating / output speed of motor 105. Cardiac performance parameters may include, for example, cardiac output, cardiac power, 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, which may be associated with a specific point in the pressure waveform of device 100), pulse pressure, stroke volume, load state, and / or volume load state. The cardiac performance parameters or changes thereof may provide an indication of cardiac health. Accordingly, the cardiac performance parameters may be provided to a medical practitioner (e.g., via a display (not shown) operably coupled to controller 132), who may then adjust device operation (e.g., device position, motor operating speed, and thus the blood flow through device 100) to adjust patient treatment. Alternatively, device 100 may automatically adjust its operation based on the cardiac performance parameters. More specifically, device 100 may follow a predetermined pattern for reducing the support provided to the patient by device 100.

[0053] Reference Figure 3 , in some embodiments, controller 132 is configured to determine one or more cardiac performance parameters as follows. First, at block 300, controller 132 determines one or more cardiac performance parameters, more specifically, the vascular pressure in the patient, the operating voltage applied to motor 105, and the operating speed of motor 105. In some embodiments, the vascular pressure determined by controller 132 is the aortic pressure. In some embodiments, controller 132 determines the vascular pressure in the patient via pressure sensor 136. In some embodiments, using known techniques for controlling a sensorless motor, controller 132 determines the operating speed of motor 105 by observing voltage fluctuations across the windings of motor 105. Next, at block 302, controller 132 inputs the pressure, operating voltage, and operating speed into a mathematical function to determine a blood flow parameter, such as the blood flow rate through device 100. In some embodiments, the mathematical function is a sum of terms including the pressure, the operating voltage applied to motor 105, and the operating speed of motor 105. Such terms may include the squares of the pressure, operating voltage, and / or operating speed, and / or the products of the pressure, operating voltage, and / or operating speed. More specifically, the function may be a polynomial function, such as:

[0054] Flow = (a0 * p 2 ) + (a1 * p) + (b0 * v 2) + (b1 * v) + (c0 * s 2)+(c1*s)+(d*p*v)+(e*p*s)+(f*v*s)+(g*p*v*s)+k

[0055] Wherein the "flow rate" is the blood flow velocity through the 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 velocity, respectively. In some embodiments, these coefficients are based on the characteristics of a particular pump, motor, and controller. These coefficients also depend on the units of measurement of the terms involved. Generally, the coefficients of the higher-order terms will be between -1 and 1, and the coefficients of the first-order terms can be larger. In some embodiments, the polynomial function may also include various higher-order terms, but these terms do not significantly affect the calculated flow rate. Similarly, in some embodiments, the polynomial function may also include various exponential or trigonometric terms. Whether these additional terms should be included can be determined by comparing the flow rate data collected from control trials with the predicted flow rate; and any differences between the two values are compared with available parameters or combinations thereof. At block 304, in addition to pressure, the controller 132 determines cardiac performance parameters using the calculated blood flow velocity. In particular, the aortic pressure and the additional blood flow provided by the pump can be used to estimate the effects on cardiac output and cardiac power output. Such determination can also be based on the sensed pressure, pulse, and anatomical data provided by the operator. The cardiac performance parameters can be any of the parameters listed above, for example, and the operation of the device can be adjusted based on these parameters.

[0056] In some embodiments, the controller 132 is configured to determine the contractility of cardiac function by changing the speed of the motor 105, more specifically, by pulsing the speed of the motor 105 over one cycle (heartbeat) or multiple cycles. Once determined, the contractility contributes to the calculation of cardiac output power. That is, the device 100 effectively self-calibrates the determination of cardiac power during operation.

[0057] In some embodiments, the controller 132 is configured to segment the voltage waveform to isolate the cardiac cycle for analysis. The controller 132 can analyze these waveforms to determine if they generally match a known model, which can indicate that the device 100 is properly positioned within the patient. The controller 132 can additionally or alternatively analyze the waveforms to determine if one or more portions of the waveform exceed a threshold, which can indicate the occurrence of a pump blockage. More specifically, the steady-state portion (near zero hertz) of the voltage waveform can be used to detect a blocked blood inlet when the voltage drops below a threshold specific to the pump and impeller design.

[0058] In some embodiments, the motor 105 operates at a speed selected by a medical practitioner, and the motor 105 is driven by a variable voltage to provide various levels of cardiac support. In other words, the practitioner selects the motor speed based on the observed cardiac performance and the practitioner's judgment of the required blood flow rate in addition to the unassisted cardiac output.

[0059] Example

[0060] As a hypothetical example, the percutaneous circulatory support device 100 is located within a patient, and more specifically, within the aorta and left ventricle and spanning the aortic valve. Next, the controller 132 determines a vascular pressure of 123 mmHg, a motor operating voltage of 6.95 V, and a motor operating speed of 29,000 RPM. Then, using the pressure, operating voltage, operating speed, and the following coefficients in the above function, the controller 132 determines a blood flow rate of 0.66 L / min, coefficients: a0 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 2.9707 L / (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 -2 L / (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 0.0 L / (min*mmHg*V*RPM), and k is 7.1132*10 -1 L / min. Using the calculated blood flow rate, the controller 132 determines the effect of the pump on the cardiac power output; in this case, the effect is 0.66 L / min * 90.3 mmHg / 451.1 = 0.13, or a 13% increase in the normalized cardiac output power relative to the patient's baseline cardiac output.

[0061] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to specific features, the scope of the present invention also includes embodiments with different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to cover all such alternative forms, modifications, and variations falling within the scope of the claims, as well as all equivalents thereof.

Claims

1. A percutaneous circulatory support device, comprising: An impeller; A motor configured to rotate the impeller to cause blood to flow through the percutaneous circulatory support device; And A controller operably coupled to the motor, the controller configured to determine: The vascular pressure in a patient; The operating voltage applied to the motor to rotate the impeller; The operating speed of the motor resulting from providing 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 performance parameter based on the blood flow parameter.

2. The percutaneous circulatory support system according to claim 1, further comprising a pressure sensor operably coupled to the controller, wherein the controller is configured to determine the vascular pressure in the patient via the pressure sensor.

3. The percutaneous circulatory support system according to any one of claims 1 or 2, wherein the controller determines the blood flow parameter by using a mathematical function that includes the vascular pressure, the operating voltage, and the operating speed.

4. The percutaneous circulatory support system according to claim 3, wherein the mathematical function includes the square of the vascular pressure.

5. The percutaneous circulatory support system according to any one of claims 3 or 4, wherein the mathematical function includes the square of the operating voltage.

6. The percutaneous circulatory support system according to any one of claims 3 to 5, wherein the mathematical function includes the square of the operating speed.

7. The percutaneous circulatory support system according to any one of claims 3 to 6, wherein the mathematical function includes the product of the vascular pressure and the operating voltage.

8. The percutaneous circulatory support system according to any one of claims 3 to 7, wherein the mathematical function includes the product of the vascular pressure and the operating speed.

9. The percutaneous circulatory support system according to any one of claims 3 to 8, wherein the mathematical function includes the product of the operating voltage and the operating speed.

10. The percutaneous circulatory support system according to any one of claims 3 to 9, wherein the mathematical function includes the product of the vascular pressure, the operating voltage, and the operating speed.

11. A method of operating a percutaneous circulatory support device, the device including an impeller, a motor configured to rotate the impeller to cause blood to flow in a patient, and a controller operably coupled to the motor, the method comprising: Determining, via the controller, the vascular pressure in the patient; Determining, via the controller, the operating voltage applied to the motor to rotate the impeller; Determining, via the controller, the operating speed of the motor resulting from providing 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 performance parameter based on the blood flow parameter.

12. The method according to claim 11, further comprising adjusting the operation of the percutaneous circulatory support device based on the cardiac performance parameter.

13. The method according to any one of claims 11 or 12 further comprises determining the contractility of the patient's cardiac function by changing the operating speed of the motor via the controller.

14. The method according to any one of claims 11 to 13 further comprises segmenting the waveform of the operating voltage via the controller.

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

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