Use of Fiber Optic Sensors as Diagnostic Tools in Catheter-Based Medical Devices

Abstract

To provide use of an optical fiber sensor as a diagnostic tool in catheter-based medical devices.SOLUTION: A blood pump system includes: an optical sensor configured to detect an optical signal during pumping operation of the blood pump, and an optical fiber configured to transmit the optical signal from the optical fiber sensor to an evaluation device communicatively coupled to the optical fiber sensor. The evaluation device is configured to receive as inputs the transmitted optical signal and a signal indicative of a motor current, and determine a mechanical failure event associated with the blood pump based on the motor current and the optical signal.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] Related technologies This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 734,702, entitled "USE OF OPTICAL FIBER SENSOR AS A DIAGNOSTIC TOOL IN CATHETER-BASED MEDICAL DEVICE," filed September 21, 2018. The entire contents of the foregoing application are incorporated herein by reference. [Background technology]

[0002] background Catheter-based medical devices can be monitored to ensure proper operation. For example, early and reliable detection of bearing failure in a blood pump can help prevent sudden pump shutdown and associated adverse patient outcomes. Some blood pumps use motor current as a sensing signal to monitor pump performance. However, motor current does not necessarily capture early signs of bearing failure and can be affected by other factors.

[0003] Blood pumps can be integrated with fiber optic pressure sensors to monitor the placement of the pump in a patient's vascular system. In addition to monitoring pressure signals, fiber optic sensors can also be used to monitor stress / strain, temperature, and vibration. For example, as described in U.S. Pat. No. 9,669,144, fiber optic sensors can be used to monitor catheter twist. However, fiber optic sensors have not been employed to detect ongoing operational characteristics of catheter-based medical devices. Summary of the Invention

[0004] overview The systems, methods, and devices described herein provide for the use of fiber optic sensors as diagnostic tools to evaluate the performance and status of catheter-based medical devices and ultimately detect potential failures. Adaptive configurations of the system can include an optical sensor and an optical fiber connecting the sensor to a monitor or other signal processing device configured to receive input signals from the sensor and determine characteristics of the medical device. In some embodiments, the tool is used to detect mechanical failures in blood pumps. Aspects are disclosed for blood pump systems including an optical sensor configured to detect optical signals during pumping operation of the blood pump and an optical fiber configured to transmit the optical signals from the optical fiber sensor to an evaluation device communicatively coupled to the optical fiber sensor. The sensor is positioned near the pump to detect disturbances in the blood caused by the pumping action of the pump, which alter or deform an optical sensor head. The sensor head deforms based on the pressure of the blood pressing against the sensor head. As the sensor head deforms, light bounces back into the sensor fiber and is detected by the evaluation device. This reflected light is compared to a reference or baseline signal, and a pressure signal is extracted from the comparison. Using reflected light, the sensor can also detect disturbances in the blood caused by vibrations of a pump housing, rotor, motor, or cannula included in the pump system. In some applications, the sensor is attached to or located adjacent to the pump housing, or located near the pump motor (in the case of an implantable motor). The evaluation device can be configured to receive as input the transmitted optical signal and a signal indicative of the pump motor current and determine a mechanical fault event associated with the pump based on the motor current and the optical signal.

[0005] This tool may be used in combination with one or more other parameters, such as motor current readings and other sensor readings, such as a position signal or flow rate, to enhance detection. In a first embodiment, the tool is implemented in a blood pump system including a catheter having a proximal end and a distal end, a blood pump having a motor coupled to the catheter, an optical sensor configured to detect an optical signal during pumping action of the blood pump, and an optical fiber extending through the catheter and configured to transmit the optical signal from the optical sensor to an evaluation device communicatively coupled to the optical sensor. The optical sensor is disposed at or near the pump to detect disturbances in the blood resulting from the pumping action of the pump. The evaluation device is configured to receive the input signal and determine whether a mechanical fault event associated with the blood pump has occurred. In certain embodiments, the determination is made based on the input optical signal and the motor current of the blood pump motor. If the pump stops pumping or encounters resistance during operation, the optical signal (and noise associated with the optical signal) will change due to changes in vibration of the motor, pump, or pump components or cannula, and the change can be detected by the evaluation device. The evaluation device can be configured to receive as inputs the transmitted optical signal and a signal indicative of the motor current, calculate a signal-to-noise ratio (SNR) of the optical signal, receive a predetermined threshold value for the SNR, compare the calculated SNR with the predetermined threshold value, and determine a mechanical fault event associated with the blood pump, pump component, cannula, or pump motor.

[0006] SNR changes can indicate pump problems. The SNR correlates with blood pump vibration or the vibration of system components such as the cannula or motor. (As used herein, pump vibration generally refers to mechanical vibration of the pump, pump components, or implanted devices, including the cannula or motor, that occurs when the device is operating in vivo.) When the motor is stopped, the pump also stops, resulting in zero motor current and minimal vibration. In this state, the SNR is relatively high because the noise level of the optical signal is low due to low pump mechanical vibration. Under normal conditions, when the motor is running, the motor current is greater than zero and pump vibration increases. In this state, the noise level of the optical signal is high, resulting in a relatively low SNR. A mechanical failure event can occur that clogs the pump, slows it down, or stops it completely. In such a state, a failure can be detected if, over a period of time, the motor current is greater than zero (indicating that the motor is driving current) but the SNR is increasing, e.g., the calculated SNR increases to above a predetermined threshold during that period. A motor current greater than zero indicates that the motor is operating as if the pump were running normally, but an increase in SNR indicates that the pump is experiencing more vibration, which may indicate that the pump is failing even though it continues to pump (e.g., the bearings may be worn out).

[0007] The evaluation device may be configured to generate and output an indicator associated with the mechanical failure event in response to determining the mechanical failure event.

[0008] In some embodiments, the evaluation device is configured to determine a threshold value based on a baseline SNR. The threshold value can be the SNR (or average value) during steady-state operation of a normal pump. In some embodiments, the determined threshold value is twice the magnitude of the baseline SNR, or at least three times or ten times or more.

[0009] In certain embodiments, the evaluation device is configured to determine a pressure signal based on the transmitted optical signal and use the signal to evaluate performance of the pump. For example, the evaluation device may be configured to determine a mechanical fault event based on the calculated SNR, the motor current, and the determined pressure signal.

[0010] The optical fiber is positioned to receive a detectable signal that can be easily used to evaluate the performance of the device. In some embodiments, the optical fiber sensor is attached to the pump housing or to a catheter or cannula near the motor, but is positioned so that it is in contact with the blood flowing from the pump (or through the motor). According to certain embodiments, the optical fiber sensor is located at the distal end of the catheter. In some embodiments, the diagnostic tool includes a second optical fiber sensor that detects the second optical signal and a second optical fiber that transmits the second optical signal to an evaluation device. The second optical signal can be positioned near the distal end of the pump (e.g., near the pump inlet opening) to detect, for example, a change in the SNR of the pumping rhythm associated with the distal end of the pump. Such a signal can also be used to determine mechanical failure events.

[0011] The period over which pump performance (and particularly SNR and motor current) is monitored can be adjusted by the user for short-term or long-term monitoring. In some embodiments, this period is set to about 1 to about 5 minutes. According to specific embodiments, this period is about 5 to about 10 minutes, or up to 6 hours, up to 24 hours, or up to a week or more.

[0012] The present disclosure also contemplates various methods, including a method for determining a mechanical failure event of a blood pump during operation. The method includes determining a motor current of a motor driving the blood pump. The method also includes detecting an optical signal in the blood pump during operation and transmitting the optical signal from an optical sensor (e.g., located near the pump housing or the pump rotor) to an evaluation device using optical fiber. The method further includes calculating a signal-to-noise ratio (SNR) in the evaluation device based on the transmitted optical signal. The method further includes determining a mechanical failure event associated with the blood pump motor based on the calculated SNR and the determined motor current. A change in SNR may indicate a problem with the pump (e.g., mechanical stress that could lead to device failure). In some configurations, a mechanical failure event is triggered when the motor current is greater than zero for a period of time and an increase in the calculated SNR during that period exceeds a predetermined threshold.

[0013] In some embodiments, the method further includes generating and outputting a signal indicative of the mechanical failure event in response to determining the mechanical failure event. For example, the signal indicative of the mechanical failure event may be sent to a processing system and displayed as an audible alarm, a visual alarm, or both.

[0014] In certain embodiments, the method further includes determining a threshold value based on, for example, a baseline SNR occurring during normal operation of the pump. According to some embodiments, the determined threshold value is twice the magnitude of the baseline SNR.

[0015] In some embodiments, the method further includes determining a pressure signal based on the transmitted optical signal. In certain embodiments, the method further includes determining a mechanical fault event based on the calculated SNR, the determined motor current, and the determined pressure signal.

[0016] In certain embodiments, the fiber optic sensor is coupled to the motor. According to some embodiments, the fiber optic sensor is located at the distal end of the catheter.

[0017] In some embodiments, the period is from about 1 to about 5 minutes. In some embodiments, the period is from about 5 to about 10 minutes.

[0018] According to further embodiments of the present disclosure, there is provided a method for operating a motor-driven catheter-based blood pump system, the blood pump system including an inlet cannula and a pump having a rotor within a shroud. The method includes actuating the rotor by sending current from the motor to the rotor of the pump. The method further includes detecting current flowing to and from the motor. The method further includes detecting vibrations of a component of the pump, or the cannula, the motor, or other system component. The method may further include adjusting current to the motor based on the detected vibrations. In some embodiments, the detected vibrations indicate a bearing fault in the rotor or motor of the pump. In other embodiments, detecting vibrations includes detecting an optical signal from an optical sensor located on or near at least one of the shroud, the cannula, and the motor. In certain embodiments, the method further includes identifying a pump rotor fault by detecting a change in vibration of a system component (e.g., the pump or the cannula) during periods when the current to the motor is positive.

[0019] The systems and methods can be applied to blood pump systems having a variety of pump configurations, including pumps with an internal motor having a motor coupled to a pump rotor and catheter (e.g., Impella systems) and pumps with an external motor and drive cable (e.g., blood pump-style pumps for converting torque supplied by an external motor). [Brief explanation of the drawings]

[0020] These and other objects and advantages will become apparent from the following detailed description considered in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.

[0021] [Figure 1] FIG. 1 is an isometric view showing an exemplary trans-aortic blood pump extending through the aortic valve into the left ventricle and having one or more integrated fiber optic sensors. [Figure 2] 2 is a cross-sectional view of the optical fiber sensor of FIG. 1 having an optical fiber. [Figure 3] 3 shows an exemplary graph of continuous logging of motor current of the blood pump of FIG. 1 and calculated signal-to-noise ratio based on signals from the fiber optic sensor of FIGS. 1 and 2. FIG. [Figure 4] 3 shows an exemplary graph of continuous logging of calculated SNR based on signals from the fiber optic sensor of FIG. 2. [Figure 5] 5A-5C show exemplary graphs of continuous logging of the position signal and motor current of the blood pump of FIG. 1 and the calculated SNR based on the signal from the fiber optic sensor of FIGS. [Figure 6] 2 illustrates an exemplary method for determining a mechanical failure event associated with the blood pump of FIG. 1. [Figure 7] 7 illustrates an exemplary method for generating and outputting indicators associated with the determined mechanical fault event of FIG. 6 and the blood pump of FIG. 1. [Figure 8] FIG. 1 shows seven exemplary graphs representing data collected from a blood pump system. [Figure 9] 9A-9C show seven exemplary graphs representing data collected from the blood pump system during a period subsequent to that shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0022] Detailed Description To provide an overall understanding of the systems, methods, and devices described herein, certain exemplary embodiments will be described. The systems, methods, and devices described herein provide for the use of fiber optic sensors as diagnostic tools for evaluating the performance and status of catheter-based medical devices. An evaluation device is used to calculate the signal-to-noise ratio (SNR) of an optical signal from the fiber optic sensor. The SNR can be used to determine the magnitude of mechanical vibration in a medical device, such as an intracardiac blood pump. In cases of higher vibration, the SNR is much lower than in cases of lower vibration. Additionally, while the medical device is operating, an increase in the SNR signal coincides with the occurrence of a mechanical failure event in the medical device. For example, a momentary spike in the SNR signal of a blood pump may coincide with a pump bearing failure. Conversely, in a static state without vibration, no momentary change is observed.

[0023] The SNR of a fiber optic sensor can be used (alone or in combination with other operating parameters) to facilitate earlier and more reliable detection of mechanical failure events and instabilities. Early and reliable detection of mechanical failures in blood pumps helps prevent sudden, harmful shutdown of the pump and associated adverse effects on the patient. The SNR of a fiber optic sensor can also help determine the location of a device within the body. Correct placement of a device within the body is important for optimal performance. Another advantage of using the SNR of a fiber optic sensor is that it can be used to detect vibrations and assess device performance, stability, and temperature.

[0024] FIG. 1 shows an intracardiac blood pump having a catheter 10 introduced retrogradely into the descending aorta 11. The descending aorta 11 is a portion of the aorta 12, which ascends and then descends from the heart, and includes an aortic arch 14. At the beginning of the aorta 12, an aortic valve 15 connects the left ventricle 16 to the aorta 12, through which the intracardiac blood pump extends. In addition to the catheter 10, the blood pump includes a rotary pumping device 50 secured at the distal end of a catheter hose 20. The pumping device 50 has a motor section 51 coupled to the catheter, a pump section 52 located distally from the motor section 51, and a flow cannula 53 protruding distally from the pump section 52. The pump section has a rotor within a shroud. The cannula has a distal inlet 54 and a proximal outlet located proximal to the rotor. The motor speed of the rotary pumping device 50 depends on the motor current driving the rotary pumping device 50. Distal to the suction inlet 54 is a soft flexible tip 55 configured, for example, as a "pigtail."

[0025] Various fluid, electrical, and other lines extend through the catheter hose 20 to operate the pumping device 50. Of these, FIG. 1 shows a configuration with two optical fibers 28 and 29 attached at their proximal ends to the evaluation device 100. These optical fibers 28 and 29 are part of optical pressure sensors whose sensor heads 60 and 30, respectively, are located outside the housing of the pump section 52 on the one hand and outside the suction inlet 54 on the other. The sensor head 60 is in contact with the blood flowing into the aorta and can therefore detect optical signals in the blood flowing therethrough (to measure aortic pressure and detect pump vibrations). The sensor head 30 (if used) is located near the distal end of the pump in the left ventricle and therefore in contact with the blood therein to measure left ventricular pressure (and also to detect pump or cannula vibrations). Optical signal measurements are made, for example, by sending pulses (or a continuous stream) of light into the blood flow and receiving return pulses that form optical sensor signals that can be returned to the evaluation device for processing. The return pulse is a reflection of the original pulse that is coupled back into the sensor heads 30 and 60 due to deformation of the glass membranes of the sensor heads, as explained further below. The optical signals from the sensor heads are sent to the evaluation device 100, which converts them into electrical signals and sends them for display on the display screen 101. Although two sensors are shown, the system may be configured to use only one. As discussed further below, the sensor head 60 may be better suited to detecting mechanical fault events than the sensor 30 because it is located near the pump housing and motor section 51, where vibrations are likely to be greatest. However, the sensor 30 can also be used to detect changes in the rhythm of the cannula's movement during pumping, which may also indicate a pump failure. The motor current of the rotary pumping device 50 is also sent to the evaluation device 100 through leads in the catheter and can be displayed on the display screen 101.

[0026] The sensor can provide a variety of useful information. When the sensor head 60 (and optionally another sensor, such as the sensor 30) is positioned within the patient, the system can measure aortic pressure. If other sensors are used, other pressures, such as ventricular pressure, can also be detected by the sensor head 30. The pressure measurement can also provide a contractility measurement to track cardiac recovery. Contractility represents the inherent ability of the heart muscle to contract. The pressure signal can also be evaluated to identify a pressure difference that can be used to calculate blood flow through the cannula of the pumping device 50. Ventricular pressure and blood flow during a heartbeat can be used to determine contractility. The distal sensor head 30 can also extend into a flexible tip 55, for example, positioned so that the head protrudes from the tip, to detect ventricular pressure. By detecting ventricular pressure with the sensor head 30, a clinician can detect when the pump has crossed the aortic valve. Additionally, the sensor is sensitive enough to detect slight bending of the tip 55, which can guide the clinician to push the pump across the valve more efficiently. When the pump is positioned close to the heart wall, similar to Figure 1, the sensor can also detect excessive pressure on the heart wall as a result of bending or twisting, for example, caused by the inlet sucking on the mitral valve and tendons in the ventricle. Detection of this condition allows the user to rotate or withdraw the pump.

[0027] Electro-optical pressure measurement is further illustrated in FIG. 2. FIG. 2 shows a pressure-measuring catheter 26 having a lumen 27 through which an optical fiber 29 (and optionally 28) can move freely. The catheter 26 can preferably be made of Nitinol or another shape-memory alloy or polymer hose. As shown in FIG. 1, the catheter 26 exits the catheter hose 20 at an exit point 57 and is guided (e.g., externally) along a flexible flow cannula 53. The pressure-measuring catheter has a sensor head (such as 30 or 60) at the distal end 34 of the optical fiber 29 (or 28). The sensor head has a head housing 31 including a thin glass membrane 32 adjacent to a cavity 33. Light impinges on the glass membrane 32 and enters and exits the fiber 28 (or 29) with low loss (i.e., low attenuation loss over the entire length of the fiber). The glass membrane 32 is pressure-sensitive and deforms according to the magnitude of pressure acting on the sensor head 30 (or 60). Deformation of the glass membrane 32 causes the light to reflect and couple back into the optical fiber 28 (or 29). At the proximal end of the optical fiber 28 (or 29), i.e., in the evaluation device 100, a digital camera, e.g., a CCD camera or CMOS, receives the incident light and generates a pressure-dependent electrical signal. For example, the camera may receive the incident light, generate an optical image or pattern, and send the image or pattern to a signal processor within the evaluation device configured to receive the image or pattern as input and use it to calculate a pressure signal. In some embodiments, the signal processor is configured to use the calculated pressure signal to control the power supply to the motorized pumping device 50. For example, if the calculated pressure signal is low, the signal processor increases the power supply to the motorized pumping device 50. If the calculated pressure signal is high, the signal processor decreases the power supply to the motorized pumping device 50.

[0028] As described above, the distal sensor head 30 extends into the flexible tip 55 of the pump to detect ventricular pressure at the tip 55. As shown, head 60 is positioned proximal to the pump and remains within the aorta to detect aortic pressure. The signal is detected and sent to evaluation device 100. The signals from heads 30 and 60 can be compared by evaluation device 100 and used to generate a differential pressure signal / measurement for use in pump positioning and monitoring. The differential signal or measurement can also be used in combination with motor current and other parameters to monitor pump positioning and performance, as discussed herein. Furthermore, this allows for highly sensitive detection of bending of tip 55, which can simplify valve traversal. If the pump is positioned close to the wall, as in Figure 1, excessive pressure on the heart wall as a result of bending or twisting can also be detected. The latter can lead to the inlet suctioning cardiac structures. This condition can be corrected by the user rotating or withdrawing the pump.

[0029] Using the distal sensor head 60 and optical fiber 28B, a mechanical fault event can be detected in the motor section 51 of the rotary pumping device 50. Using the optical signal transmitted from the distal sensor head 60 to the evaluation device 100 using the optical fiber 28B, the evaluation device 100 can calculate the SNR of the optical signal. The SNR is correlated to the mechanical vibration of the rotary pumping device 50. When the rotary pumping device 50 is stopped, the mechanical vibration of the rotary pumping device 50 is minimal. In this state, the noise level of the optical signal is low, so the SNR is relatively large. When the rotary pumping device 50 is operating, the mechanical vibration of the rotary pumping device 50 increases. During normal operation, the noise level of the optical signal is large, so the SNR is relatively low, and the motor current is greater than zero (because the motor is driving the current to the pump). The SNR when the rotary pumping device 50 is operating under its normal conditions can be considered a baseline SNR and can be used to determine a threshold SNR for detecting SNR changes that may signal a mechanical fault event. During a mechanical fault event, the SNR may increase for a short period of time as the speed of the rotary pumping device 50 slows, for example, due to a bearing failure or a partially clogged rotor, but the motor current is positive, indicating that the motor is still working.

[0030] An increase in SNR above a baseline (or other threshold) can be detected and evaluated to evaluate pump performance. In some applications, the evaluation device 100 determines whether a mechanical failure event has occurred by determining whether the increase in SNR over a certain period of time exceeds a threshold during (or at) the time the pump is operating (e.g., indicated by a positive motor current). The evaluation device 100 will be configured with a threshold based on the baseline SNR prior to the mechanical failure event. For example, the threshold can be set as a multiple (e.g., one-quarter, one-third, one-half, or two times) the magnitude of the baseline SNR. Other thresholds can also be used by the evaluation device 100 to determine a mechanical failure event. Alternatively, the evaluation device 100 can receive input from a user indicating a threshold for evaluating the SNR change. The period over which the SNR is evaluated can be any desired period. For example, the input period can be 1 minute, about 1 to about 5 minutes, about 5 to about 10 minutes, or about 10 to about 20 minutes. Other periods can also be used by the evaluation device 100 to determine a mechanical failure event. If the evaluation device 100 determines that a mechanical fault event has occurred, for example, if the SNR exceeds a threshold during an evaluation period while the motor current remains positive, the evaluation device 100 may generate and output an indicator associated with the mechanical fault event, which may be displayed on the display screen 101.

[0031] FIG. 3 illustrates an exemplary graph 300 of continuous logging of the motor current of the rotary pumping device 50 of FIG. 1 and the calculated SNR based on signals from the fiber optic sensor of FIGS. 1 and 2 over several days. Graph 300 includes a motor current 302 and an SNR 304. The motor current 302 of the rotary pumping device 50 is sent to the evaluation device 100 over several days and is greater than zero when the rotary pumping device 50 is operating and is zero when the motor is stopped. The baseline SNR is the SNR when the rotary pumping device 50 is operating because the SNR is relatively low. During a bearing failure event 306, the SNR 304 increases from the baseline SNR over a short period of time (e.g., a few minutes in the example of FIG. 3 ). For example, as shown in FIG. 3 , the SNR 304 increases from a baseline SNR of approximately 3500 to an SNR 304 of 5500. The SNR increases over this short period of time because the bearing failure causes the rotary pumping device 50 to slow down, thereby slowing down the pump vibrations. In this example, the increase in SNR over the short period is approximately 2000. The evaluation device 100 determines a threshold SNR for detecting a bearing failure event 306. For example, the evaluation device 100 may determine the threshold based on the baseline SNR, since the baseline SNR is the SNR during normal operation of the pump. A large deviation from the SNR during pump operation indicates a bearing failure event, which may also indicate other faults in the pump. The evaluation device 100 may determine that the threshold is a fixed and / or predetermined amount of the baseline SNR. For example, as shown in FIG. 3 , the evaluation device 100 may determine that the threshold is one-half the baseline SNR (3500), or 1750. Because the motor current is greater than zero (the rotary pumping device 50 is operating) and the increase in SNR over the short period (2000) is greater than the threshold (1750), the evaluation device 100 determines that a bearing failure event 306 has occurred.At least one advantage of using the fiber optic sensor's SNR 304 in combination with the motor current 302 is that it enables earlier and more reliable detection of pump failure events 306 (e.g., bearing failures that are typically difficult to detect). Unlike previous generations of blood pumps, the systems and methods of the present disclosure contemplate using optical sensors to assess pump performance by detecting signals from fiber optic sensors such as the SNR 304. The sensors may also be used to monitor the placement of the pump in the vasculature.

[0032] FIG. 4 shows an exemplary graph 400 of continuous logging of calculated SNRs based on signals from the fiber optic sensor of FIG. 2 over a one-month period. Graph 400 includes a first SNR 402 and a second SNR 404. The first SNR 402 and the second SNR 404 were each obtained from the evaluation device 100 at different times and are compared in graph 400. During normal operation over several days, the first SNR 402 and the second SNR 404 do not increase for a short period of time. To simulate a bearing failure event 406, power to the blood pump was turned off. During the bearing failure event 406, the first SNR 402 and the second SNR 404 increase for a short period of time due to the loss of power. The loss of power causes the speed of the rotary pumping device 50 to decrease, resulting in a decrease in vibration. The decrease in vibration simulates the bearing failure event 406. As described with respect to Figure 3, the evaluation device 100 can determine that a bearing fault event 406 has occurred based on the first SNR 402 and the second SNR 404. Figure 4 illustrates the reliability of using the SNR signal as an indicator of bearing fault, as there are few, if any, false positives.

[0033] Alternatively, the evaluation device 100 can use the position signal, motor current, and SNR to determine whether a mechanical failure event has occurred. The position signal is calculated by the evaluation device 100 from the optical signal sent by the sensor head 60 and indicates pressure. The position signal can be used in combination with the process described above with respect to FIGS. 3 and 4 to determine a mechanical failure event. For example, FIGS. 5A-5C show three exemplary graphs of continuous logging of the position signal and motor current of the rotary pumping device 50 of FIG. 1 and the calculated SNR based on the signal from the optical fiber sensor of FIGS. 1 and 2. As shown in each of the three graphs in FIGS. 5A-5C, when the position signal is stable, the evaluation device can determine a decrease in SNR as the motor speed increases because the mechanical vibration of the rotary pumping device 50 increases with increasing motor speed. The evaluation device 100 will identify a mechanical failure event if the position signal is stable, the motor speed / current is stable, and the SNR increases over a short period of time. For example, the increase in SNR may be instantaneous. In some examples, the increase in SNR may occur over a period of about 100 milliseconds to about 1 second, or about 1 second to about 10 seconds. In other examples, the increase in SNR may occur over a period of about 1 to about 5 minutes, or about 5 to about 10 minutes. Using the SNR in combination with the positioning signal and motor current is advantageous because the positioning signal provides more information about the position of the pump within the patient.

[0034] Figure 6 shows a process 600 for determining a mechanical fault event associated with the blood pump 50 of Figure 1. In step 602, the evaluation device 100 determines the motor current of the motor driving the blood pump. For example, as described above with respect to Figures 1 and 2, the motor current of the rotary pumping device 50 is sent to the evaluation device 100 and can be displayed on the display screen 101.

[0035] At step 604, the evaluation device 100 determines whether the motor current is greater than zero. For example, if the rotary pumping device 50 is stopped, the motor current is zero, and if the rotary pumping device 50 is running, the motor current is greater than zero. If the motor current is zero, the process 600 ends at step 606. However, if the motor current is greater than zero, the process 600 proceeds to step 608.

[0036] In step 608, the evaluation device 100 detects the optical signal at the blood pump. For example, as described above with respect to Figures 1 and 2, the glass membrane 32 is pressure sensitive and deforms depending on the amount of pressure acting on the sensor head 60 (or 30). For example, deformation of the glass membrane 32 causes light to reflect and couple back into the optical fiber 28 (or 29).

[0037] In step 610, optical fiber 28 transmits the optical signal from the optical fiber sensor to an evaluation device 100. For example, as described above with respect to Figures 1 and 2, the optical signal transmitted by sensor heads 30 and 60 can be converted into an electrical signal in evaluation device 100 and displayed, for example, on display screen 101.

[0038] In step 612, the evaluation device 100 calculates the SNR based on the transmitted optical signal. For example, using an optical signal transmitted from the distal sensor head 60 to the evaluation device 100 using the optical fiber 28, the evaluation device 100 can calculate the SNR of the optical signal. The SNR is linked to the mechanical vibration of the rotary pumping device 50. When the rotary pumping device 50 is stopped, the motor current is zero and the mechanical vibration of the rotary pumping device 50 is minimal. In this state, the noise level of the optical signal is low, so the SNR is relatively large. When the rotary pumping device 50 is operating, the motor current is greater than zero and the mechanical vibration of the rotary pumping device 50 increases. In this state, the noise level of the optical signal is high, so the SNR is relatively low.

[0039] In step 614, the evaluation device 100 determines a mechanical fault event associated with the blood pump motor based on the calculated SNR. As described above with respect to FIGS. 1 and 2, when the rotary pumping device 50 is stopped, the mechanical vibration of the rotary pumping device 50 is minimal. In this state, the SNR is relatively large because the noise level of the optical signal is low. When the rotary pumping device 50 is operating, the motor current is greater than zero and the mechanical vibration of the rotary pumping device 50 increases. A sudden increase in the SNR from a baseline (e.g., when the pump is operating normally) signals a mechanical problem with the pump. For example, in a fault state, the noise level of the optical signal is large but the motor current is greater than zero, resulting in a relatively low SNR, indicating that the motor is driving the pump with current but the pump is not pumping (or is slowing down). The evaluation device 100 determines a threshold SNR for detecting a mechanical fault event. In one aspect, the evaluation device can receive the threshold SNR from a user input. Alternatively, the SNR when the rotary pumping device 50 is operating can be considered a baseline SNR and used to determine a threshold SNR for detecting a mechanical fault event. During a mechanical fault event, the SNR increases for a short period of time due to, for example, a bearing failure causing the rotary pumping device 50 to slow down. Step 614 is described in more detail below in connection with process 700 of FIG. 7.

[0040] 7 illustrates a process 700 for generating and outputting indicators associated with the determined mechanical fault events of process 600 and the blood pump of FIG. 1. In step 702, evaluation device 100 receives as inputs a transmitted optical signal and a signal indicative of the motor current. For example, as described above with respect to FIGS. 1 and 2, the motor current of rotary pumping device 50 is transmitted to evaluation device 100 and may be displayed on display screen 101, and optical signals transmitted by one or both of sensor heads 30 and 60 may be converted to electrical signals in evaluation device 100 and displayed, for example, on display screen 101.

[0041] In step 704, the evaluation device 100 determines whether the motor current is greater than zero. For example, when the rotary pumping device 50 is stopped, the motor current is zero, and when the rotary pumping device 50 is operating, the motor current is greater than zero. If the motor current is zero, the process 700 ends in step 706. However, if the motor current is greater than zero, the process 700 proceeds to step 708. When the rotary pumping device 50 is stopped (or slowed down), the mechanical vibration of the rotary pumping device 50 slows down and reaches a minimum when the pump is stopped. In the pump-stopped state, the noise level of the optical signal is low, so the SNR is relatively large. When the rotary pumping device 50 is operating, the motor current is greater than zero, and the mechanical vibration of the rotary pumping device 50 increases. In this state, during normal pump operation, the noise level of the optical signal is high, so the SNR is relatively low.

[0042] However, during a pump failure or malfunction, the SNR will change, and the following steps can help identify this. In step 708, the evaluation device 100 calculates the SNR based on the transmitted optical signal. For example, using an optical signal transmitted from the proximal sensor head 60 to the evaluation device 100 using the optical fiber 28, the evaluation device 100 can calculate the SNR of the optical signal. The SNR is correlated to the mechanical vibration of the rotary pumping device 50.

[0043] In step 710, the evaluation device 100 receives a predetermined threshold value for SNR. For example, the SNR when the rotary pumping device 50 is operating can be considered a baseline SNR and can be used to determine a threshold SNR for detecting a mechanical failure event. The evaluation device 100 can determine the threshold value based on the baseline SNR before the mechanical failure event. For example, the threshold value can be a multiple (e.g., one-quarter, one-half, or two times) the magnitude of the baseline SNR.

[0044] At steps 712 and 714, the evaluation device 100 compares the calculated SNR to a predetermined threshold over a period of time to determine whether the increase in the calculated SNR over that period exceeds the predetermined threshold. For example, during a mechanical fault event, the SNR increases over a short period of time because the speed of the rotary pumping device 50 decreases due to a pump component failure (e.g., a bearing failure). The evaluation device 100 can determine whether a mechanical fault event has occurred by determining whether the increase in SNR over that period of time exceeds the threshold. This period of time can be any period set by the user. For example, the period of time can be longer than one minute. In other examples, the period of time can be from about one minute to about five minutes, or from about five minutes to about ten minutes. As described with respect to FIG. 3 , because the motor current is greater than zero (the rotary pumping device 50 is operating) and the increase in SNR (2000) over the short period of time is greater than the threshold (1750), the evaluation device 100 can determine that a fault event 306 has occurred.

[0045] If the evaluation device 100 determines that the increase in the calculated SNR over the period does not exceed the predetermined threshold, the process 700 ends at step 716. However, if the evaluation device 100 determines that the increase in the calculated SNR over the period does exceed the predetermined threshold, the process 700 proceeds to step 718.

[0046] At step 718, evaluation device 100 generates and outputs an indicator associated with the mechanical failure event. For example, if evaluation device 100 determines that a mechanical failure event has occurred, evaluation device 100 can generate and output an indicator associated with the mechanical failure event. The indicator can be displayed on display screen 101. Device 100 can also send a control signal to stop the motor in response to the determination.

[0047] 8-9 show data collected from a blood pump system experiencing a mechanical fault. Figure 8 shows seven exemplary graphs representing data collected from the blood pump system. Graph 804 shows the optical sensor SNR (unitless), graph 806 shows the raw purge flow rate (mL / hr), graph 808 shows the disposition signal (mmHg), graph 810 shows the motor current (mA), graph 812 shows the motor speed (rpm), graph 814 shows the pump flow rate (L / min), and graph 816 shows the alarm occurrence (alarm number). Graphs 804 through 816 are plotted on the same time scale and begin at the same time (March 7, 2019, 12:31:34). At time 802, the SNR (shown in graph 804) significantly increases relative to the SNR prior to time 802. Before time 802, the average SNR was about 2500, with a maximum of about 6000 and a minimum of about 1000. After time 802, the average SNR was about 5000, with a maximum of over 8000 and a minimum of about 1000. At time 802, the motor current (shown in graph 810) also increased rapidly for a short period of time, from a maximum of about 830 mA, a minimum of about 690 mA, and an average of about 760 mA before time 802 to a maximum of over 1000 mA, a minimum of about 780 mA, and an average of about 850 mA after time 802. The amplitude of the pump flow variance (shown in graph 814) also decreased at time 802, from an amplitude of about 1 L before time 802 to an amplitude of about 0.2 L after time 802. These increases in SNR and motor current at time 802 indicate a mechanical problem or instability in the blood pump system, a problem that corresponds in time to the bearing failure that led to the motor failure described below and shown in FIG. 9.

[0048] FIG. 9 is a continuation of the graphs shown in FIG. 8 (starting at 14:52:57 on March 7, 2019, where the x-axis of the graphs shown in FIG. 8 ends). Graph 904 shows a continuation of the SNR from graph 804, graph 906 shows a continuation of the raw purge flow rate from graph 806, graph 908 shows a continuation of the configuration signal from graph 808, graph 910 shows a continuation of the raw motor current from graph 810, graph 912 shows a continuation of the motor speed signal from graph 812, graph 914 shows a continuation of the raw pump flow rate signal from graph 814, and graph 916 shows a continuation of the alarm generation signal from graph 816. At time 902, the motor of the blood pump system failed. As shown in FIG. 9 , when the motor failed (after the bearing failure at time 802), the SNR increased, the position signal decreased, the motor current decreased to approximately 0 mA, the motor stopped working (motor speed went to 0 rpm), pump flow stopped, and an alarm (shown in graph 916) was triggered. The increase in SNR and motor current at time 802 indicated a mechanical problem in the blood pump system approximately one hour before the motor failed at time 902. At least one benefit of identifying an increase in SNR and motor current (e.g., at time 802) is earlier and more reliable detection of mechanical problems and instabilities in the blood pump system. In some embodiments, such an increase in SNR, motor current, or both may trigger an alarm, shut down the motor, or prompt the user to remove (and potentially replace) the blood pump system before the motor fails.

[0049] In view of the foregoing, those skilled in the art will appreciate that the present disclosure provides for the use of fiber optic sensors as diagnostic tools for assessing the performance and status of catheter-based medical devices. While the aspects and features described herein are particularly illustrated for use in connection with percutaneous heart pump systems, it will be understood that the components and other features described below may be combined with one another in any suitable manner and adapted and applied to other types of medical devices, such as electrophysiology study and catheter ablation devices, angioplasty and stenting devices, angiography catheters, peripherally inserted central catheters, central venous catheters, midline catheters, peripheral catheters, inferior vena cava filters, abdominal aortic aneurysm treatment devices, thrombectomy devices, TAVR delivery systems, cardiac therapy and cardiac assist devices including balloon pumps, cardiac assist devices implanted using surgical incisions, and any other venous or arterial-based intraluminal introducer catheters and devices.

[0050] The foregoing is merely illustrative of the principles of the present disclosure, and the systems, methods, and devices may be practiced in other than the described manner, which is presented for purposes of illustration and not limitation. It should be understood that while the systems, methods, and devices disclosed herein are illustrated for use in a percutaneous heart pump, they may also be applied to systems, methods, and devices for other implantable heart pumps or implantable cardiac assist devices.

[0051] Variations and modifications will occur to those skilled in the art after reviewing this disclosure. The various features described or illustrated above may be combined or integrated in other systems, including any combination thereof. Additionally, certain features may be omitted or not implemented. The various embodiments described or illustrated above may be combined in any manner.

[0052] Examples of changes, substitutions, and alterations would be ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made a part of this application.

Claims

1. 1. A method performed by a motor-driven catheter-based blood pump system, the blood pump system including a cannula and a pump having a rotor within a shroud, the method comprising: detecting a current flowing to the motor; detecting with a sensor disturbances in the blood caused by vibrations of components of the pump; and identifying a mechanical fault event associated with the pump based on the current flowing to the motor and the detected disturbance.

2. The method of claim 1 , wherein the mechanical failure event is a bearing failure in the pump.

3. The method of any one of claims 1 to 2, wherein the sensor is an optical sensor located on or near the shroud, the cannula, or the motor.

4. 4. The method of claim 1, wherein identifying the mechanical fault event comprises identifying a rotor fault by detecting a change in blood disturbances caused by a change in vibration of the pump component during a period when the current to the motor is positive.

5. The method of claim 4, wherein the period of time is from about 1 to about 5 minutes.

6. The method of claim 4, wherein the period is from about 5 to about 10 minutes.

7. The method of claim 4 , wherein the change in the vibration of the component of the pump is a decrease in the vibration of the component of the pump.

8. The method of any preceding claim, further comprising, in response to identifying the mechanical failure event, generating and outputting an indicator associated with the mechanical failure event.

9. 1. A catheter-based blood pump system driven by a motor, the blood pump system including a cannula and a pump having a rotor within a shroud, the blood pump system comprising: detecting a current flowing to the motor; detecting with a sensor disturbances in the blood caused by vibrations of components of the pump; Identifying a mechanical fault event associated with the pump based on the current flowing to the motor and the detected disturbance. The blood pump system is configured as follows.

10. The system of claim 9 , wherein the mechanical failure event is a bearing failure in the pump.

11. The system of any one of claims 9 to 10, wherein the sensor is an optical sensor located on or near the shroud, the cannula, or the motor.

12. 12. The system of claim 9, wherein identifying the mechanical fault event comprises identifying a fault in the rotor by detecting a change in disturbances in the blood caused by a change in vibration of the component of the pump during a period when the current to the motor is positive.

13. The system of claim 12, wherein the period of time is from about 1 to about 5 minutes.

14. The system of claim 12, wherein the period of time is about 5 to about 10 minutes.

15. The system of claim 12 , wherein the change in the vibration of the component of the pump is a decrease in the vibration of the component of the pump.

16. The system of any one of claims 9 to 15, wherein the blood pump system is further configured to generate and output an indicator associated with the mechanical failure event in response to identifying the mechanical failure event.

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