Flow estimation method for axial flow blood pump in aorta

Abstract

The invention discloses a flow estimation method for an axial flow blood pump in an aorta, and belongs to the field of medical instruments. The method comprises the steps that an axial flow blood pump flow-pressure rise performance in-vitro test circulation loop is built, and pressure rise data changes of a blood pump at different rotating speeds and flows are recorded through a flow sensor and a pressure sensor; performing linear fitting on the flow-pressure rise test data based on a least square method, and obtaining flow-pressure rise characteristic equations corresponding to different rotating speeds; further establishing a function relation between the slope and the rotating speed and a function relation between the intercept coefficient and the rotating speed in the flow-pressure rise characteristic equation, and establishing a flow estimation equation containing rotating speed and pressure rise parameters in parallel. By measuring the pressure rise data of the blood pump and combining the real-time rotating speed signal fed back by the controller, the pump blood flow of the blood pump in the human body is indirectly estimated, the problem of dependence on a flow sensor in a clinical environment is solved, and the real-time performance of clinical hemodynamics monitoring is improved.

Description

Technical Field

[0001] The invention relates to a flow estimation method for an intra-aortic axial flow blood pump, and belongs to the field of medical devices. Background Art

[0002] The aortic axial flow pump is a short- to medium-term ventricular assist device that, by being implanted in locations such as the abdominal aorta or thoracic aorta, can effectively reduce the left ventricular load and increase perfusion at the downstream end of the aorta, helping to treat decompensated heart failure with cardiogenic shock.

[0003] To ensure the safety and reliability of blood pumps, real-time monitoring of the blood pump's operating status within the patient's body is necessary. Flow data is one of the key parameters reflecting the blood pump's operating status. Existing flow measurement methods for intra-aortic axial flow blood pumps have many shortcomings. Some methods rely on complex and expensive external equipment, such as ultrasonic flowmeters, which not only increases medical costs but also limits the convenient use of blood pumps in clinical practice. Furthermore, due to the limited implantable space for axial flow blood pumps, it is difficult to install a flow sensor. Therefore, a flow estimation method that does not require the installation of a flow sensor within the blood pump is needed. Summary of the Invention

[0004] The object of the present invention is to provide a flow estimation method for an intra-aortic axial flow blood pump, which can monitor the flow of the intra-aortic axial flow blood pump in real time without installing a flow sensor in the blood pump.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for estimating flow rate of an intra-aortic axial flow blood pump, the method comprising the following steps: (1) Build an in vitro test loop for the flow-pressure rise performance of an axial blood pump, and use flow and pressure sensors to record the changes in the pressure rise data of the blood pump at different speeds and flow rates; (2) Based on the least squares method, linear fitting is performed on the flow-pressure rise test data, and the corresponding flow-pressure rise characteristic equations at different speeds are obtained; (3) Establish the functional relationship between the slope and intercept coefficients of the flow-pressure rise characteristic equation and the speed, and construct the flow estimation equation including the speed and pressure rise parameters in parallel; (4) Adjust the axial blood pump to the target speed, measure the pressure rise values ​​corresponding to different flow rates at the speed, substitute the pressure rise and speed data into the flow estimation equation, and compare and verify with the measured flow results.

[0006] Furthermore, the circulation loop includes an axial blood pump, a partition, a liquid storage tank, a throttle valve, an ultrasonic flow sensor, a pressure sensor and an axial blood pump controller arranged on the auxiliary pipeline; wherein, The axial flow blood pump is inserted into the central hole of the partition through its pump housing, so that the liquid to be tested can only flow out through the axial flow blood pump; The pressure sensor is used to measure the inlet pressure and outlet pressure of the axial blood pump; The axial flow blood pump controller is used to adjust the speed of the axial flow blood pump and collect speed, flow and pressure test data at the same time.

[0007] Furthermore, the physical properties of the liquid to be measured are similar to those of blood, and the inner diameter of the auxiliary pipeline is 18-25 mm.

[0008] Furthermore, in step (1), the blood pump speed is adjusted by the axial flow blood pump controller, the circulation loop flow is adjusted by the throttle valve, and the flow rate and pressure rise ∆P=P2-P1 of the axial flow blood pump at different speeds are recorded.

[0009] Furthermore, in step (2), a linear fit is performed on the flow-pressure rise data at different speeds, and a fitting equation Q=k*∆P+b is obtained based on the least squares method, where Q represents the flow rate, k represents the slope coefficient, and b represents the intercept coefficient.

[0010] Furthermore, in step (3), a quadratic polynomial function relationship k=A*N²+B*N+C between the slope coefficient k and the speed N in the flow-pressure rise characteristic equation and a linear function relationship b=D*N+E between the intercept coefficient b and the speed N are established, and the flow estimation equation Q=(A*N²+B*N+C)*∆P+(D*N+E) is constructed jointly.

[0011] Furthermore, the blood pump operation data under each working condition were measured three times and the average value was taken.

[0012] Furthermore, when collecting flow-pressure rise performance curve data of the axial blood pump, the pressure rise range meets clinical requirements, and the number of speed samples is not less than 3.

[0013] Furthermore, the axial flow blood pump is mainly composed of a micro motor, a pump housing, a tail guide piece and an impeller. Micro pressure sensors are respectively provided on the surface of the pump housing and the tail guide piece for real-time collection of pressure data when the axial flow blood pump is implanted in the aorta.

[0014] Furthermore, the micro pressure sensor is fixed to the outer wall of the pump housing or the tail guide member through a bonding process, or is embedded in a pre-set groove.

[0015] The advantages of the present invention are: The present invention provides a flow estimation method for an intra-aortic axial flow blood pump. It can pre-collect the flow-pressure rise performance data of the blood pump at different rotational speeds through in vitro experiments, and obtain the functional equation of the blood pump flow, rotational speed and pressure rise through linear fitting and quadratic polynomial fitting methods. This method obtains the inlet and outlet pressure difference of the blood pump in real time through an implantable pressure sensor, and combines the real-time rotational speed data fed back by the controller to indirectly calculate the pump blood flow through the above equation, thus avoiding the implantation risk and signal interference problems of traditional flow sensors. Compared with the existing technology, the present invention does not need to rely on external flow monitoring equipment, and can achieve real-time estimation of the pump blood flow only through the dual parameter collection of rotational speed and pressure rise, which significantly improves the real-time performance and clinical applicability of hemodynamic monitoring of axial flow blood pumps. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the intra-aortic axial flow blood pump in the present invention.

[0017] Figure 2 Schematic diagram of the blood pump flow-pressure rise performance in vitro test circuit in the present invention.

[0018] Figure 3 Schematic diagram of the installation of the blood pump in the in vitro test circulation loop of the present invention (a cross-sectional view of the blood pump installation position).

[0019] Figure 4 Flow chart of the steps of the blood pump flow estimation method in the present invention.

[0020] Figure 5 The flow-pressure rise data and fitting curves of the blood pump at different speeds in the present invention are shown.

[0021] Figure 6 This is the relationship curve between the slope coefficient, intercept coefficient and rotation speed in the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be noted that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0023] The present invention proposes a flow estimation method for an intra-aortic axial flow blood pump. Figure 1As shown, the intra-aortic axial-flow blood pump 1 primarily consists of a micromotor 11, a pump housing 12, a tail guide 13, and an impeller 14. Micropressure sensors 111 and 112 are mounted on the surfaces of the pump housing 12 and tail guide 13, respectively (their leads are not shown). These sensors are used to collect real-time pressure data while the axial-flow blood pump 1 is implanted in the aorta. These two micropressure sensors can be flexibly mounted and can be fixed to the outer wall of the pump housing 12 or tail guide 13 via adhesive bonding, or embedded in pre-defined grooves in either, to meet diverse installation requirements and ensure accurate pressure measurement.

[0024] like Figure 2 As shown, the test circulation loop for measuring the flow-pressure rise performance of the intra-aortic axial blood pump mainly includes an axial blood pump 1, a partition 2, a liquid reservoir 3, a throttle valve 4, a flow sensor 5, a pressure sensor 7 and an axial blood pump controller 8 arranged on an auxiliary pipeline 6. The controller 8 is used to adjust the speed of the axial blood pump 1 and collect speed, flow and pressure test data at the same time. The speed data of the blood pump is collected by the Hall sensor integrated in the motor and transmitted to the controller 8. Among them, the installation of the axial blood pump 1 in the test is as follows Figure 3 As shown. The axial-flow blood pump 1 is inserted into the center hole of the partition 2 via the pump housing 12, allowing the liquid to be tested to flow out only through the axial-flow blood pump 1. Micro pressure sensors 111 and 112 measure the inlet pressure P1 and outlet pressure P2 of the axial-flow blood pump, respectively. The flow sensor 5 can employ a variety of probe types, including contact-type measuring probes such as electromagnetic flowmeters, differential pressure flowmeters, and turbine flowmeters, or non-contact measuring probes such as ultrasonic flow sensors.

[0025] Figure 4 FIG. 1 is a flow chart of a method for estimating flow of an axial blood pump according to the present invention, the method comprising the following steps: S01: Build Figure 2 For the blood flow-pressure-rise performance test loop, the test fluid's physical properties must be similar to those of blood. For example, a 40% glycerol-60% water mixture can be used. The inner diameter of auxiliary line 6 should range from 18-25 mm, closely matching the inner diameter of the human aorta.

[0026] S02: Regulate the blood pump speed via controller 8 and adjust the flow rate within the circulation loop via throttle valve 4. Record the flow rate and the pressure rise of the axial blood pump 1, ∆P = P2 - P1, at different speeds. Specifically, the blood pump is set to a fixed speed, N. When the speed feedback signal from controller 8 differs from the set value by no more than ±0.5%, the speed is considered stable. The throttle valve 4 opening is then continuously adjusted to achieve different flow rates.

[0027] S03: Perform linear fitting on the flow-pressure rise data at different speeds (N1=40000 rpm, N2=45000 rpm, N3=50000 rpm, etc.). Based on the least squares method, the fitting equation is Q=k*∆P+b, that is, Q1=k1*∆P1+b1, Q2=k2*∆P2+b2, Q3=k3*∆P3+b3, etc., where Q represents the flow rate, k represents the slope coefficient, and b represents the intercept coefficient.

[0028] S04: Further establish the functional relationship between the slope coefficient k, intercept coefficient b and speed N in the flow-pressure rise characteristic equation; among them, the functional relationship between the slope coefficient k and speed N is a quadratic polynomial fitting k=A*N 2 +B*N+C, the functional relationship between the intercept coefficient b and the speed N is a linear fit b=D*N+E. Based on the determined A, B, C, D and E parameters, the flow estimation equation Q=(A*N 2 +B*N+C)*∆P+(D*N+E); where the unit of speed N is rpm, the unit of flow rate Q is L / min, and the unit of pressure rise ∆P is mmHg.

[0029] S05: According to the function equation of flow rate, speed and pressure rise obtained in step S04, the speed of the axial blood pump is adjusted to the target speed N4, and the pressure rise values ​​corresponding to different flow rates of the axial blood pump at the speed N4 are measured, and the pressure rise and speed data are substituted into the estimation equation Q=(A*N 2 +B*N+C)*∆P+(D*N+E), and compared and verified with the measured flow results.

[0030] Therefore, before constructing the flow estimation equation, it is necessary to collect the operating parameter samples of the axial flow blood pump under different working conditions and the corresponding actual flow value samples. Figure 2 As shown in the figure, an in vitro simulated circulation loop is used to test the operating parameters and flow values ​​of the blood pump under various working conditions. It should be noted that in order to ensure the accuracy and reliability of the test data, the operating data of the blood pump needs to be measured three times under each working condition and the average value is taken. Figure 5 and Figure 6 As shown in Figure 1, when collecting data on the flow-pressure rise performance curve of the axial flow blood pump, the pressure rise range must meet the actual clinical requirements, and the number of speed samples must be no less than 3. Figure 5 and Figure 6 The data fitting process needs to meet the fitting degree R 2As shown in Table 1, based on the blood pump flow estimation equation proposed in the present invention, a cross-validation study was conducted on the blood pump flow at the new operating condition blood pump speed N4. The validation results showed that the error between the flow estimation value and the measured value was approximately 5%, which can meet clinical application requirements.

[0031] Table 1 Flow rate verification results under blood pump speed-N4 condition In addition, when performing fitting processing on the measurement data in steps S03 and S04, it is not limited to linear fitting or quadratic polynomial fitting, and other nonlinear fitting or exponential fitting methods may also be used according to different blood pump structures.

[0032] The advantages of the present invention are: The present invention provides a flow estimation method for an intra-aortic axial flow blood pump. It can pre-collect the flow-pressure rise performance data of the blood pump at different rotational speeds through in vitro experiments, and obtain the functional equation of the blood pump flow, rotational speed and pressure rise through linear fitting and quadratic polynomial fitting methods. This method obtains the inlet and outlet pressure difference of the blood pump in real time through an implantable pressure sensor, and combines the real-time rotational speed data fed back by the controller to indirectly calculate the pump blood flow through the above equation, thus avoiding the implantation risk and signal interference problems of traditional flow sensors. Compared with the existing technology, the present invention does not need to rely on external flow monitoring equipment, and can achieve real-time estimation of the pump blood flow only through the dual parameter collection of rotational speed and pressure rise, which significantly improves the real-time performance and clinical applicability of hemodynamic monitoring of axial flow blood pumps.

[0033] The above are preferred embodiments of the present invention and the technical principles used therein. For those skilled in the art, any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, are within the scope of protection of the present invention.

Claims

1. A method for estimating flow rate of an intra-aortic axial flow blood pump, characterized by: The method comprises the following steps: (1) Build an in vitro test loop for the flow-pressure rise performance of an axial blood pump, and use flow and pressure sensors to record the changes in the pressure rise data of the blood pump at different speeds and flow rates; (2) Based on the least squares method, linear fitting is performed on the flow-pressure rise test data, and the corresponding flow-pressure rise characteristic equations at different speeds are obtained; (3) Establish the functional relationship between the slope and intercept coefficients of the flow-pressure rise characteristic equation and the speed, and construct the flow estimation equation including the speed and pressure rise parameters in parallel; (4) Adjust the axial blood pump to the target speed, measure the pressure rise values ​​corresponding to different flow rates at the speed, substitute the pressure rise and speed data into the flow estimation equation, and compare and verify with the measured flow results.

2. The flow estimation method of an intra-aortic axial flow blood pump according to claim 1, characterized in that: The circulation loop includes an axial blood pump, a partition, a liquid storage tank, a throttle valve, an ultrasonic flow sensor, a pressure sensor and an axial blood pump controller arranged on the auxiliary pipeline; wherein, The axial flow blood pump is inserted into the central hole of the partition through its pump housing, so that the liquid to be tested can only flow out through the axial flow blood pump; The pressure sensor is used to measure the inlet pressure and outlet pressure of the axial blood pump; The axial flow blood pump controller is used to adjust the speed of the axial flow blood pump and collect speed, flow and pressure test data at the same time.

3. The flow estimation method of an intra-aortic axial flow blood pump according to claim 2, characterized in that: The physical properties of the liquid to be measured are similar to those of blood, and the inner diameter of the auxiliary pipeline is 18-25 mm.

4. The flow estimation method of an intra-aortic axial flow blood pump according to claim 1 or 2, characterized in that: In step (1), the blood pump speed is adjusted by the axial flow blood pump controller, the circulation loop flow is adjusted by the throttle valve, and the flow rate and pressure rise ∆P=P2-P1 of the axial flow blood pump at different speeds are recorded.

5. The flow estimation method of an intra-aortic axial flow blood pump according to claim 4, characterized in that: In step (2), a linear fit is performed on the flow-pressure rise data at different speeds, and a fitting equation Q=k*∆P+b is obtained based on the least squares method, where Q represents the flow rate, k represents the slope coefficient, and b represents the intercept coefficient.

6. The flow estimation method of an intra-aortic axial flow blood pump according to claim 5, characterized in that: In step (3), a quadratic polynomial function relationship k=A*N²+B*N+C between the slope coefficient k and the speed N in the flow-pressure rise characteristic equation and a linear function relationship b=D*N+E between the intercept coefficient b and the speed N are established, and the flow estimation equation Q=(A*N²+B*N+C)*∆P+(D*N+E) is constructed jointly.

7. The flow estimation method of an intra-aortic axial flow blood pump according to claim 1 or 2, characterized in that: The blood pump operation data under each working condition were measured three times and the average value was taken.

8. The flow estimation method of an intra-aortic axial flow blood pump according to claim 1 or 2, characterized in that: When collecting the flow-pressure rise performance curve data of the axial blood pump, the pressure rise range meets clinical requirements, and the number of speed samples is not less than 3.

9. The flow estimation method of an intra-aortic axial flow blood pump according to claim 1 or 2, characterized in that: The axial flow blood pump is mainly composed of a micro motor, a pump housing, a tail guide piece and an impeller. Micro pressure sensors are respectively provided on the surface of the pump housing and the tail guide piece for real-time collection of pressure data when the axial flow blood pump is implanted in the aorta.

10. The flow estimation method of an intra-aortic axial flow blood pump according to claim 9, characterized in that: The micro pressure sensor is fixed to the outer wall of the pump housing or the tail guide member through a bonding process, or is embedded in a pre-set groove.

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