Disclosure of Invention
The invention aims to overcome the defects of the existing extracorporeal circulation system, and provides a novel extracorporeal circulation system which can reduce the blood damage degree, improve the oxygenation efficiency, and accurately control and monitor the circulation parameters so as to ensure the safety and health of patients in the extracorporeal circulation process.
The technical scheme of the invention is as follows:
an extracorporeal circulation system, the system comprising:
a blood pumping device for driving blood to flow in the extracorporeal circulation system;
a filtering device for removing impurities in blood;
a warming device for regulating the temperature of blood;
a gas exchange device for regulating the gas content in blood;
and the monitoring and control system is used for monitoring and controlling the operation parameters of the extracorporeal circulation system in real time.
Further, the blood pumping device includes:
The centrifugal pump comprises a centrifugal pump body, wherein blades of the centrifugal pump body are made of titanium alloy, the surfaces of the blades of the centrifugal pump body are coated with hydrophilic polymers through a plasma enhanced chemical vapor deposition technology, and the inner wall of a centrifugal cavity is provided with a nanoscale ceramic coating;
And the electromagnetic driving system consists of an electromagnetic coil and a permanent magnet, and generates a variable magnetic field by controlling the current and the frequency in the electromagnetic coil so as to push the permanent magnet to drive the centrifugal pump to rotate.
Further, the filtering device adopts a multi-layer filtering membrane structure, wherein,
The first layer adopts a microporous filter membrane with specific pore size distribution for filtering thrombus, tissue fragments and other visible impurities;
The second layer adopts ultrafiltration membrane for filtering small molecular harmful substances, inflammatory mediators and protein aggregates.
Further, the pore diameter of the microporous filter membrane is between 50 and 200 microns, and the molecular weight cut-off of the ultrafiltration membrane is between 5 and 50 kDa.
Further, the filtering device further comprises a pressure monitoring device, wherein the pressure monitoring device is positioned at an inlet and an outlet of the filtering device and is used for measuring the pressure difference of the inlet and the outlet of the filtering device.
Further, the warming device includes:
The hydrothermal heating system adopts a spiral heat exchange pipeline to increase the contact area between blood and circulating water, wherein the heat exchange pipeline is made of medical-grade polycarbonate or silicon rubber;
And the temperature monitoring system is used for uniformly distributing a plurality of thermocouple temperature sensors at the blood inlet and outlet and the heating area, transmitting blood temperature signals at different positions to the monitoring and control system in real time and accurately monitoring the blood temperature at multiple points.
Further, the gas exchange apparatus includes:
the membrane oxygenator consists of hollow fibers with uniform micropore structures and a shell, wherein the shell is provided with a blood inlet and a blood outlet and a gas inlet and a gas outlet and is used for effectively flowing and separating blood and gas;
And the gas flow regulating system is used for regulating the flow of the entering and exiting oxygen and carbon dioxide according to the real-time monitoring result of the oxygen partial pressure and the carbon dioxide partial pressure in the blood.
Further, the hollow fibers have an inner diameter between 200 and 500 microns.
Further, the monitoring and control system consists of a sensor system, a microprocessor and a man-machine interaction interface, wherein,
The sensor system comprises a pressure sensor, a temperature sensor, an oxygen partial pressure sensor, a carbon dioxide partial pressure sensor and a flow sensor, and is used for collecting pressure, temperature, blood oxygen partial pressure, carbon dioxide partial pressure and blood flow information in an extracorporeal circulation system in real time;
The microprocessor is used for controlling an electromagnetic driving system of the blood pumping device, a gas flow regulating system of the gas exchange device and the heating device according to the set physiological parameter range;
The man-machine interaction interface and the alarm system are used for realizing interaction between a user and the extracorporeal circulation system and warning of abnormal states of the system.
Compared with the prior art, the invention has the following advantages:
the blood pumping device greatly reduces mechanical damage to blood, obviously reduces the risks of hemolysis and thrombosis, ensures the integrity and physiological functions of the blood, and is beneficial to improving the postoperative recovery effect and long-term health condition of patients through an optimized blade structure, a coating technology and an electromagnetic driving system.
The multi-layer filtering membrane structure and the accurate pressure monitoring mechanism of the filtering device can comprehensively remove various impurities in blood, and harmful substances, inflammatory mediums and protein aggregates from large-particle thrombus and tissue fragments to small molecules effectively reduce postoperative complications caused by impurities, improve the purity of the blood and ensure the safety and quality of the blood.
The heating device ensures the accurate and stable temperature of blood through the optimal design of the spiral heat exchange pipeline, accurate temperature monitoring and intelligent control algorithm, controls the temperature fluctuation in a very small range, avoids adverse effect on the physiological function of blood due to temperature change, and enhances the safety and stability of the extracorporeal circulation process.
The high-efficiency hollow fiber membrane and the accurate gas flow regulating system of the gas exchange device realize high-efficiency gas exchange, ensure accurate regulation of oxygen and carbon dioxide content in blood, meet oxygen requirements of tissues and organs in a long-time extracorporeal circulation process, avoid accumulation of carbon dioxide in the blood, and maintain acid-base balance of the blood.
The monitoring and control system realizes real-time, accurate and automatic control and monitoring of the extracorporeal circulation system through a comprehensive sensor system, an intelligent microprocessor and a convenient human-computer interaction interface, reduces the need and error of manual intervention, improves the reliability of the system and the convenience of operation, and provides safer and more stable guarantee for the treatment of patients.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
As shown in fig. 1, the extracorporeal circulation system of the present invention is mainly composed of the following important parts:
(one) a blood pumping device:
Centrifugal pump:
The blades of the centrifugal pump are made of titanium alloy materials, and the materials have excellent mechanical properties and biocompatibility and can bear high stress and shearing force in the blood pumping process. The shape of the blade is designed and optimized in fluid dynamics, and the contour and the surface curvature of the blade are determined according to fluid mechanics calculation so as to ensure that turbulence and shearing force of blood flow are minimized in the blood pumping process and reduce the risk of damage to blood cells in blood. As shown in fig. 2, the blades of the centrifugal pump have a unique three-dimensional curved shape, the cross-sectional shape of which is approximately streamline, and the thickness of the blades is gradually reduced from the leading edge to the trailing edge, so as to reduce the resistance when fluid flows therethrough. The leading edge of the vane has a radius of curvature, typically between 2-5 mm, which helps to guide the blood smoothly into the vane channel, avoiding the creation of separate flows and eddies. The trailing edge of the blade is designed to be sharp and has a thickness of about 0.5-1.5 mm to promote efficient outflow of blood and reduce wake loss.
The blade surface is coated with a hydrophilic polymer by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) technology, specifically polyethylene glycol (PEG) is used as a precursor gas, and the precursor gas is decomposed and uniformly deposited on the blade surface in a plasma environment to form a hydrophilic coating with the thickness of about 30-80 nanometers. The coating greatly enhances the hydrophilicity of the surface of the blade, and effectively reduces the adsorption and aggregation of components such as cells, proteins and the like in blood on the surface of the blade, thereby reducing the possibility of thrombus formation.
The inner wall of the centrifugal cavity is covered with a nano-scale ceramic coating, the coating is generated by a Chemical Vapor Deposition (CVD) process, and a coating with the thickness of about 200-600 nanometers is formed on the inner wall of the centrifugal cavity by taking precursor gases of ceramics such as hexamethyldisilazane and the like as raw materials. The nano ceramic coating has low friction coefficient and excellent blood compatibility, further reduces interaction between blood and the cavity wall, and prevents adhesion and aggregation of blood components on the cavity wall.
Electromagnetic drive system:
The electromagnetic coil is wound on a specially designed insulating framework by high-purity copper wires, and the turns, shape and size of the coil are designed according to the structure of the centrifugal pump and the required magnetic field intensity distribution.
The permanent magnet adopts high-performance rare earth permanent magnet materials, such as neodymium iron boron permanent magnets, and the shape and the size of the permanent magnet are designed according to the rotor structure and the load requirement of the centrifugal pump, so that the permanent magnet can be ensured to stably drive the impeller to rotate under the action of a magnetic field.
The system is provided with a special power supply and a driving circuit, and is precisely controlled through a micro controller ARM Cortex-M series. The microcontroller uses a pulse width modulation technique to precisely adjust the magnitude and frequency of the current output to the electromagnetic coil according to a preset rotational speed or flow demand. For example, when the blood pumping speed needs to be increased, the microcontroller correspondingly increases the duty ratio of the PWM signal, so that the average current of the electromagnetic coil is increased, the magnetic field strength is enhanced, and the impeller is driven to rotate in an accelerating way.
For monitoring the rotational speed of the centrifugal pump in real time, an optical rotational speed sensor is provided on the centrifugal pump, which sensor uses the principle of optical reflection or refraction. The special reflective mark is arranged on the impeller, when the impeller rotates, the light emitted by the sensor can generate periodic signal change due to periodic shielding or reflection of the mark, the signal is received by the photoelectric detector and converted into an electric signal, and finally the electric signal is transmitted to the microcontroller, so that the accurate measurement and real-time monitoring of the rotation speed of the impeller are realized.
(II) a filtering device:
A first layer of microporous filter membrane:
The microporous filter membrane adopts polysulfone or polyethersulfone as a base material. Firstly, the polymer material is dissolved in an organic solvent (such as N-methyl pyrrolidone) to form a solution with the concentration of 18-22% (w/v). The solution is then poured onto a specially treated support substrate, which may be a polyester fiber or stainless steel wire mesh, having a mesh size smaller than the pore size of the microporous filter membrane, providing mechanical support to the filter membrane. Then immersing the polymer solution in a coagulating bath (such as deionized water), and carrying out phase separation on the polymer solution by a phase inversion method by precisely controlling the temperature of the coagulating bath (controlled at 28-32 ℃), the coating thickness of the solution (precisely controlled at 0.5-1.5 mm) and the diffusion speed of the solution in the coagulating bath (by adjusting the viscosity of the solution and the stirring speed of the coagulating bath), so as to form the microporous filter membrane with the pore diameter ranging from 50 micrometers to 200 micrometers. The microporous filter membrane has higher porosity and good mechanical strength, can effectively intercept thrombus, tissue fragments and other visible impurities in blood, and prevents the large-particle impurities from entering a subsequent circulatory system.
Second layer ultrafiltration membrane:
The ultrafiltration membrane takes polyamide or cellulose acetate as a base membrane material. The method comprises the steps of firstly immersing a base film in an aqueous solution containing amine monomers (such as m-phenylenediamine) to enable the surface of the base film to fully adsorb the amine monomers, immersing the base film in an organic solution containing acyl chloride monomers (such as trimesoyl chloride), and forming an ultrathin separation layer through interfacial polymerization reaction. The reaction time is strictly controlled between 2 and 4 minutes, and an ultrafiltration membrane with the molecular weight cutoff of 5 to 50kDa is formed. The thickness of the ultrafiltration membrane is about 60-180 micrometers, and the effective filtration of small molecular harmful substances, inflammatory mediums and protein aggregates is realized while the sufficient mechanical strength is ensured.
Pressure monitoring device:
The pressure monitoring device adopts a piezoresistance sensor, and the pressure monitoring device is characterized in that a piezoresistance chip based on a semiconductor piezoresistance effect is arranged on an inlet and outlet pipeline of the filtering device. When blood flows through the filter device, the pressure difference between the inlet and the outlet can cause the resistance value of the piezoresistor to change, and the resistance value change is converted into an electric signal through the Wheatstone bridge circuit. The electric signal is amplified by an amplifying circuit, noise interference is removed by a filtering circuit, and finally an analog signal is converted into a digital signal by an analog-to-digital conversion (ADC) circuit and is transmitted to a monitoring and control system. When the detected inlet-outlet pressure difference exceeds a preset threshold (40-60 mmHg, for example), the monitoring and control system can give an alarm to indicate that the filtering membrane is blocked or the performance is reduced.
(III) a heating device:
A hydrothermal heating system:
The core component of the hydrothermal heating system is a spiral heat exchange pipeline which is made of medical-grade polycarbonate or silicon rubber materials through an extrusion molding process. The spiral heat exchange pipeline has specific parameters including spiral diameter of 4-7cm, spiral pitch of 1.5-2.5cm, and length of 40-70cm, depending on the required heat exchange area and blood flow. The inner wall of the pipeline is specially treated to ensure that the surface is smooth and the surface roughness is 0.1-0.3 microns so as to reduce the resistance of blood flowing in the pipeline.
The heating element is a high-power resistance wire, adopts nichrome material, is tightly wound on the outer part of the heat exchange pipeline through insulating ceramic fiber, ensures the electrical insulation between the resistance wire and the pipeline, and prevents electric leakage and short circuit. The power of the resistive wire is determined by the heating requirements and system design and is typically 800-1200W.
The circulating water system comprises a water tank, a water pump and a temperature sensor. The water tank is of a sealing structure, the circulating water stored in the water tank is used as a heat exchange medium, and the capacity of the water tank is designed according to the heat exchange requirement of the system and is generally 5-10 liters. The water tank is equipped with the liquid level sensor, when the water level is less than certain level, can trigger alarm system, prevent to lead to the resistance wire dry combustion method because of the water level is too low. The water pump ensures the stable flow of the circulating water in the pipeline, and the flow rate of the circulating water is adjusted according to the heat exchange efficiency and the heating power of the system.
Temperature monitoring system:
A plurality of thermocouple temperature sensors are uniformly distributed in the blood inlet and outlet and the heating area, and K-type thermocouples are adopted. The probe of the thermocouple is in direct contact with the blood or heat exchange line, converting the change in temperature into a change in thermoelectric voltage according to the seebeck effect. The thermoelectric signal is transmitted to a signal conditioning circuit through a compensation wire, the circuit comprises a pre-amplifier, a low-pass filter, a linearization circuit and an analog-to-digital conversion (ADC) circuit, wherein the pre-amplifier amplifies the weak thermoelectric signal by 100-500 times, the low-pass filter filters high-frequency noise, the linearization circuit converts the thermoelectric signal into a signal which is in linear relation with temperature, and finally the analog signal is converted into a digital signal through the ADC circuit and is transmitted to a monitoring and control system. The monitoring and control system precisely controls the power of the resistance wire according to the temperature data collected by the thermocouples according to a PID control algorithm, precisely controls the temperature of blood at 36.5-37.5 ℃ and ensures that the blood keeps stable temperature in the extracorporeal circulation process without exceeding +/-0.3 ℃, thereby avoiding adverse effects on the physiological functions of the blood due to temperature fluctuation.
(IV) a gas exchange device:
membrane oxygenator:
The membrane oxygenator comprises hollow fibers of uniform microporous structure and a housing. The hollow fiber is made of silicone rubber or polymethylpentene material through stretching and heat setting processes. The material is first made into thin tube and stretched at specific stretch ratio (350-450%) and temperature (130-170 deg.c) to form hollow fiber with inside diameter of 200-500 microns. The hollow fibers are arranged in parallel and encapsulated in the transparent medical-grade polycarbonate or acrylic resin shell, the shape and the size of the shell are designed according to the flow of blood and gas and the layout of a system, and the shell is provided with a blood inlet, a blood outlet, a gas inlet and a gas outlet, so that the reasonable flow paths of the blood and the gas are ensured, and the effective separation and flow of the blood and the gas are realized. The arrangement of the hollow fibers has high uniformity and compactness, the distance between adjacent fibers is 0.1-0.5 mm, and when blood flows in the fibers, gas can be fully diffused outside the fibers, so that efficient gas exchange is realized.
Gas flow regulating system:
The gas flow regulation system employs a Mass Flow Controller (MFC) and an electrically operated regulator valve. The mass flow controller is provided with a high-precision flow sensor based on a thermal or differential pressure principle, and the flow measurement error is within +/-1.5%. The flow sensor measures the mass flow of the gas based on the heat transfer characteristics of the gas or the differential pressure generated when the gas flows through the restriction. The electric regulating valve accurately regulates the opening of the valve according to the control signal of the microcontroller.
An oxygen partial pressure sensor based on a fluorescence quenching principle and a carbon dioxide partial pressure sensor based on an infrared absorption principle are respectively arranged at a blood outlet and a gas inlet of the gas exchange device. The oxygen partial pressure sensor accurately measures the oxygen partial pressure in blood by measuring the fluorescence intensity change of fluorescent substances under different oxygen partial pressures, and the carbon dioxide partial pressure sensor accurately measures the carbon dioxide partial pressure in blood by detecting the change of the infrared absorption peak intensity by utilizing the absorption characteristic of carbon dioxide molecules to a specific infrared band. According to the monitored oxygen partial pressure and carbon dioxide partial pressure, the microcontroller controls the opening degree of the electric regulating valve according to preset gas exchange parameters (such as the target range of the oxygen partial pressure in blood is 85-115mmHg and the target range of the carbon dioxide partial pressure is 32-48 mmHg), so that the oxygen and carbon dioxide contents in blood are ensured to be in ideal states, and sufficient oxygen supply is provided for tissues and organs and carbon dioxide is effectively discharged.
And (V) a monitoring and control system:
sensor system:
a pressure sensor:
and piezoresistive pressure sensors are arranged at the inlet and outlet of the blood pumping device, the inlet and outlet of the filtering device, the inlet and outlet of the gas exchange device and other key parts. The measuring range of the pressure sensor at the inlet and the outlet of the blood pumping device is 0-600mmHg with the accuracy of +/-1.5 mmHg, the measuring range of the inlet and the outlet of the filtering device is 0-300mmHg with the accuracy of +/-1 mmHg, and the measuring range of the inlet and the outlet of the gas exchange device is 0-400mmHg with the accuracy of +/-1.2 mmHg. The pressure sensor converts the pressure signal into a weak electric signal through a Wheatstone bridge circuit, and then the weak electric signal is processed through an amplifying, filtering and analog-to-digital conversion (ADC) circuit, and the processed digital signal is transmitted to the microcontroller.
Temperature sensor:
In addition to the thermocouple temperature sensor in the warming device, a thermocouple or thermistor temperature sensor is additionally arranged at the position of the blood pumping device, the filtering device, the gas exchange device and the like which possibly influence the blood temperature. The thermistor temperature sensor is based on the characteristic that the resistance of the thermistor changes along with the temperature, the measurement range is 22-43 ℃ and the precision is +/-0.2 ℃. The resistance change is converted into an electric signal through a Wheatstone bridge circuit or other signal conditioning circuits, and the electric signal is transmitted to the microcontroller after analog-to-digital conversion, so that the omnibearing temperature monitoring of the system is realized.
Oxygen partial pressure and carbon dioxide partial pressure sensors:
The oxygen partial pressure sensor and the carbon dioxide partial pressure sensor work according to the principle in the gas exchange device, so that accurate monitoring of the partial pressure of the gas in the blood is ensured. The measuring range of the oxygen partial pressure sensor is 60-140mmHg with the accuracy of +/-1 mmHg, the measuring range of the carbon dioxide partial pressure sensor is 25-55mmHg with the accuracy of +/-0.8 mmHg.
Flow sensor:
an ultrasonic doppler flow sensor is used to transmit ultrasonic waves of a specific frequency into blood and to receive reflected waves. The blood flow rate is calculated according to the Doppler shift principle of ultrasonic waves. The sensor probe is arranged on the blood pipeline, the transmitting frequency is determined according to the range of the blood flow velocity and the pipeline size, the measuring range is 0.2-8L/min, and the measuring precision is +/-4%. The ultrasonic Doppler flow sensor converts the flow velocity information into an electric signal, and the electric signal is transmitted to the microcontroller after signal conditioning and analog-to-digital conversion, so that accurate data is provided for flow control of the system.
And (3) a microprocessor:
The microprocessor adopts a high-performance microcontroller, such as an ARM Cortex-M series chip. The microprocessor receives digital signals from the sensor system through a plurality of high-speed input/output interfaces, and controls the electromagnetic driving system of the blood pumping device, the gas flow regulating system of the gas exchange device and the heating device in real time according to a preset physiological parameter range (including a blood flow range of 3.5-7.5L/min, a temperature range of 36.2-37.8 ℃ and a gas partial pressure range) by utilizing a complex control strategy of combining a built-in fuzzy logic control algorithm and a PID control algorithm. For example, when the blood flow rate is monitored to be lower than 3.5L/min, the microprocessor can increase the driving current and frequency of the blood pumping device to increase the blood pumping speed, when the blood temperature is higher than 37.8 ℃, the microprocessor can reduce the resistance wire power of the heating device, and when the oxygen partial pressure in the blood is lower than 85mmHg or the carbon dioxide partial pressure is higher than 48mmHg, the microprocessor can correspondingly adjust the opening of the electric regulating valve of the gas flow regulating system. The microprocessor also has a data storage function, can store the operation data of the system, including the historical data of each sensor, the adjustment record of control parameters and the like, has a storage capacity of 2GB, and is convenient for subsequent data analysis and system performance evaluation.
Human-computer interaction interface and alarm system:
The human-computer interaction interface adopts a high-resolution touch screen, and the screen size is 8-12 inches. Through Graphic User Interface (GUI) software, an intuitive and easy-to-operate user interface is developed to display the running state of the system, real-time data of each sensor, setting parameters, system operation menus and other information. The medical staff can conveniently input and adjust parameters such as target blood flow, temperature range, gas exchange parameters and the like through the touch screen.
The alarm system comprises a buzzer and LED lamps with different colors. When the system operation parameters are monitored to exceed the preset range, different alarm mechanisms are triggered according to the abnormality degree. For serious anomalies such as over-high or over-low pressure, out-of-control temperature, abnormal gas partial pressure and the like, the buzzer can give out high-frequency (1000-2000 Hz) alarm sound, meanwhile, the red LED lamp continuously flashes, and for slight anomalies or early warning conditions, the buzzer gives out low-frequency (200-500 Hz) alarm sound, and the yellow LED lamp flashes. The abnormal information is stored in the internal flash memory storage device, the storage capacity is 1.5GB, and the latest 200 abnormal records can be stored, so that the medical staff can conveniently check and analyze the abnormal records, and corresponding treatment measures can be taken.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical solution of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.