A wearable arteriovenous fistula blood flow non-invasive monitoring device

Abstract

The present application relates to a kind of wearable arteriovenous fistula blood flow noninvasive monitoring device, which is based on the principle of fluid heat transfer, and is a wireless wearable electronic device for noninvasive measurement of arteriovenous fistula blood flow of patients undergoing maintenance hemodialysis due to renal failure, comprising a top PDMS package (1), a back-end processing module (2), a middle PDMS partition package (4), a front-end test module (5) and a bottom PDMS package (6). Compared with the prior art, the present application fully utilizes the small and portable characteristics of wearable electronics, the low sensitivity of material thermodynamic properties to motion state and the time average effect, solves the problems of low measurement accuracy, inconvenience of carrying and easy to cause treatment delay of existing blood flow measurement equipment, and reduces the risk of fistula occlusion of hemodialysis patients.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of medical biosensors, and particularly relates to a wearable internal arteriovenous fistula blood flow noninvasive monitoring device. BACKGROUND

[0002] The internal arteriovenous fistula is mainly used for maintenance hemodialysis treatment of patients with renal failure; the internal arteriovenous fistula plasty makes the artery near the wrist or elbow and the adjacent vein anastomose, and the anastomosed vein arterialized, forming an internal arteriovenous fistula; the mature internal arteriovenous fistula is not only convenient for repeated puncture, but also can provide sufficient blood flow for several times of hemodialysis treatment per week, providing guarantee for the sufficiency of hemodialysis treatment.

[0003] The internal arteriovenous fistula maturation failure, internal arteriovenous fistula stenosis and thrombosis are the most common complications after internal arteriovenous fistula surgery. Such patients often have internal fistula failure or occlusion within a period of time after internal fistula neoplasty or repair due to poor vascular conditions or intimal hyperplasia, and need to be discovered in time for surgical intervention. Failure to repair in time will cause unnecessary surgical trauma to the patient and loss of valuable vascular resources; therefore, it is necessary to monitor the blood flow velocity of the internal arteriovenous fistula of maintenance hemodialysis patients, especially high-risk patients, on a daily basis. If the blood flow is too slow, it indicates that the internal arteriovenous fistula is at risk of blockage, and measures need to be taken to eliminate stenosis or thrombosis to restore patency.

[0004] Currently, the technologies applied to blood flow measurement mainly include traditional blood flow monitoring technology and wearable blood flow monitoring technology. The traditional blood flow monitoring technology relies on large fixed medical equipment deployed in hospitals, and the wearable blood flow monitoring technology relies on small portable electronic devices. In particular, wearable medical technology has been widely used in clinical practice, such as traditional devices: 24-hour dynamic electrocardiogram, dynamic blood pressure monitoring and insulin pump, as well as new forms of devices: continuous glucose monitoring (CGM) for diabetic patients, new electronic skin patches and other emerging wearable medical devices. Wearable blood flow monitoring technology is a wearable medical device applied to the field of blood flow monitoring.

[0005] In one aspect, in the traditional blood flow monitoring technology, the main monitoring devices and methods that already exist are digital subtraction angiography (DSA) and vascular Doppler ultrasound.

[0006] Digital subtraction angiography is the "gold standard" for diagnosing vascular stenosis. This method injects a contrast agent that cannot be penetrated by X-rays into the blood vessels, and uses the image displayed by the contrast agent under X-rays to diagnose blood vessel lesions. Since vascular puncture is required, the clinical use of this method has limitations.

[0007] Vascular Doppler ultrasound is a technique that uses an ultrasound generator to emit signals, which are reflected off the surface of moving red blood cells after passing through the skin, muscle, and blood vessels, and are then received by an ultrasound receiver. Based on the frequency shift of the reflected ultrasound waves, blood flow velocity signals are obtained. The K / DOQI guidelines for kidney disease recommend that vascular Doppler ultrasound be used to measure the blood flow of arteriovenous fistulas every month.

[0008] Both of the above techniques rely on specialized medical equipment and require patients to repeatedly visit the hospital to schedule ultrasound or specialist doctors for examination, which cannot achieve daily monitoring, especially for high-risk patients and patients who need to closely observe the changes in fistula flow. It is not possible to monitor at all times, and it is not possible to prevent stenosis and occlusion of arteriovenous fistulas in a timely and effective manner. Other indirect monitoring methods, such as laser vibration measurement technology for measuring the speed and amplitude of fistula tremor, also involve the problem of large size of the measuring equipment, and are rarely used for maintenance of arteriovenous fistulas in dialysis patients in domestic medical institutions.

[0009] On the other hand, the currently disclosed wearable blood flow monitoring technology is mainly divided into three categories: portable ultrasound Doppler technology, photoplethysmography technology, and blood flow thermodynamic analysis technology.

[0010] The basic principle of portable ultrasound Doppler technology is the same as that of traditional vascular Doppler ultrasound. Patent publication numbers CN112155600A, CN204909456U, CN210931524U, and CN213551925U each disclose a wristband-type ultrasound Doppler blood flow velocity measuring device, which greatly reduces the size of the ultrasound device. F. Wang et al. published a Flexible Doppler ultrasound device for the monitoring of blood flow velocity in Science Advance (Vol. 7, No. 44, 2021), which arranges the ultrasound probe on a flexible substrate to form a flexible blood flow monitoring device that is directly bonded to the skin, further reducing the size of the blood flow monitoring device and improving the convenience of use. However, compared to fixed special-purpose ultrasound Doppler devices, portable ultrasound devices have fewer probes and less ultrasound energy, resulting in low image clarity and limited flow measurement accuracy, which has not yet been widely recognized by medical personnel.

[0011] Photoplethysmography (PPG) is based on photoelectric analysis principle, which uses photoelectric elements to detect the changes in skin light transmittance caused by heart pumping to reflect blood flow. Patent publication CN112426577A discloses an implantable PPG blood flow measurement device, which implants photoelectric devices on the surface of internal fistula, establishes a personalized database for a single patient with a duration of 72 hours, extracts waveform pattern data and characteristic numerical signal of blood flow, and realizes the measurement of internal fistula blood flow. This technology is based on implantable devices, and the actual acceptance is limited.

[0012] Blood flow thermodynamic analysis technology is based on fluid mechanics and thermodynamics to indirectly measure blood flow. Patent publication CN106999060A discloses a skin device for analyzing temperature characteristics and heat transfer characteristics, which sequentially arranges three groups of electronic devices on the skin surface directly above the blood vessel, including a group of heaters in the middle, and two groups of temperature sensors located upstream and downstream respectively. After the blood is heated, the heat is transferred to the downstream blood vessel wall, causing a significant difference in skin temperature upstream and downstream of the heater, which changes with the change of blood flow. Measuring this difference can reflect the size of blood flow. Patent publication CN111970962A discloses a cerebrospinal fluid drainage tube flow measurement device based on the same principle, which expands the application field of this technology. However, the relationship between the temperature difference upstream and downstream and the flow size is not monotonically related, and this technology needs to rely on other semi-quantitative flow testing methods to determine the approximate interval of the current flow, which is inconvenient to use.

[0013] According to the research results of the prior art, the special medical equipment is bulky, which limits the promotion of traditional blood flow monitoring technology; the test precision is low and other equipment is needed to assist, so that the wearable blood flow monitoring technology is not widely recognized. SUMMARY

[0014] The purpose of the present application is to overcome the defects of the prior art and provide a wearable arteriovenous fistula blood flow non-invasive monitoring device. The device is flexible and wearable, which realizes real-time non-invasive monitoring of arteriovenous fistula blood flow of hemodialysis patients, can timely grasp the patency of arteriovenous fistula, and can timely alert doctors and patients when the internal fistula flow decreases and is suspected of thrombus, so as to take thrombus removal measures and blood vessel expansion measures as soon as possible, and ensure the normality of internal fistula and the health of patients.

[0015] The purpose of the application can be realized by the technical scheme: a wearable arteriovenous fistula blood flow noninvasive monitoring device is designed based on fluid heat transfer principle, which is a wireless wearable electronic device for noninvasive measurement of arteriovenous fistula blood flow of hemodialysis patients. It comprises a top PDMS package, a rear-end processing module, a middle PDMS partition package, a front-end test module and a bottom PDMS package. The middle PDMS partition package and the bottom PDMS package are bonded with the front-end test module, the top PDMS package is bonded with the rear-end processing module, and the rear-end processing module and the front-end test module are electrically connected through connecting wires.

[0016] Further, the front-end test module is directly bonded with the patient's skin or bonded with the patient's skin with the help of a coupling agent, and the components include: a heater, a temperature sensor, a flexible circuit substrate and a matching circuit, the heater and the temperature sensor are arranged on the flexible circuit substrate, and the front-end test module is provided with an external connector interface concentrated on the edge of the module, and the matching circuit supplies power to the heater or conducts the voltage signal of the temperature sensor through the docking interface.

[0017] Further, the flexible circuit substrate is a flexible sheet made of insulating high-temperature resistant polymer material;

[0018] The heater uses a ceramic heating sheet or a metal resistance heating wire;

[0019] The temperature sensor uses a thermistor or a metal coil;

[0020] The matching circuit uses copper wire or aluminum wire.

[0021] Further, the front-end test module contains a heater and a temperature sensor, which are arranged flat on the flexible circuit substrate, the area of the temperature sensor is smaller than that of the heater, the temperature sensor is located at the center of the heater range, or at other positions within the heater range, or surrounded by the heater, or outside the heater range.

[0022] Further, the top PDMS package uniformly covers the surface of each device in the front-end test module to realize external insulation except the interface.

[0023] Further, in the front-end test module, the heater adopts a whole layout or a split layout, that is, the heater adopts a whole heating sheet or a whole resistance wire, or a combination of multiple heating sheets or multiple resistance wires at corresponding positions.

[0024] The shape of the heater is rectangular, rhombic, circular or elliptical.

[0025] Further, the temperature sensor in the front-end test module adopts a whole layout or a split layout, that is, each temperature sensor adopts a thermistor or a metal resistance wire, or adopts an array combination of multiple thermistors or multiple metal resistance wires at corresponding positions.

[0026] Further, the back-end processing module comprises a circuit substrate, a signal conditioning circuit, a micro-processing chip, a battery and a wireless communication module arranged on the circuit substrate.

[0027] The signal conditioning circuit comprises a Wheatstone bridge, a low-pass filter, an operational amplifier and an analog-to-digital converter.

[0028] The temperature sensor of the front-end processing module is connected to the measured arm of the Wheatstone bridge through an external connector interface, the Wheatstone bridge is connected to the low-pass filter, the low-pass filter is connected to the operational amplifier, the operational amplifier is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the micro-processing chip, and the micro-processing chip is connected to the wireless communication module.

[0029] Further, the circuit substrate adopts a hard insulating material or a flexible insulating material, the low-pass filter adopts a resistance-capacitance network, the operational amplifier, the analog-to-digital converter, the wireless communication module and the micro-processing chip adopt small commercial modules with a patch type package, and the battery adopts a button cell.

[0030] Further, the front-end test module and the back-end processing module adopt a stacked layout or a tiled layout, the back-end processing module is stacked on the front-end test module, or is tiled on the skin of other positions of the patient or is tiled on other tables and chairs through a lengthened solid lead wire.

[0031] The device delivers the internal fistula blood flow information to the communication equipment of the patient through a wired or wireless manner, and the patient reads the information through an application software.

[0032] The application heats the skin through the resistance heater placed on the body surface directly above the internal fistula, measures the body surface temperature at the point through the temperature sensor placed inside or near the resistance heater, calculates the change amplitude of the temperature at the point when the blood flow in the internal fistula changes, and evaluates the blood flow according to the corresponding relationship between the size of the amplitude and the size of the blood flow.

[0033] Compared with the prior art, the application has the beneficial effects that:

[0034] (1) The present application realizes non-invasive and wireless measurement of fistula flow based on the principle of thermodynamic analysis, realizes measurement accuracy higher than that of portable ultrasonic Doppler technology, arranges a heater and a temperature sensor on the surface of the patient's arm, associates the absolute temperature change of a single sensor with the flow change, and avoids the additional semi-quantitative detection procedure of the existing blood flow thermodynamic analysis technology. The technical effect of the technology can realize real-time monitoring of internal fistula blood flow, and meets the needs of timely warning to medical staff and kidney dialysis patients when the internal fistula gradually narrows.

[0035] (2) The present application adopts a patch type configuration, and the device with small volume is bonded on the body surface directly above the fistula, replacing the existing belt type design, and the force on the internal fistula is lower, which is more conducive to maintaining the healthy state of the internal fistula.

[0036] (3) The present application determines a quantitative monitoring method from the function of measuring the real flow of the fistula, can monitor the specific value of the internal fistula blood flow in real time, replaces the qualitative judgment mode of the internal fistula state in the prior art, and can give more direct and reliable internal fistula state feedback to patients and medical staff.

[0037] (4) The mapping relationship between the body surface temperature and the internal fistula flow is established in advance through CFD simulation, and only one calibration of the internal fistula of a single patient is needed with the aid of an ultrasonic Doppler device, and the device of the present application can work with the aid of the prior database, and the time for establishing the basic database is reduced from 72 hours to 1 hour required for single calibration. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of the overall structure of the present application.

[0039] Figure 2 is an exploded view of Figure 1 .

[0040] Figure 3 is an embodiment 1 front-end test module structure design scheme in the present application

[0041] Figure 4 is an effect schematic diagram of the present application worn on the patient's arm.

[0042] Figure 5 is a composition schematic diagram of the back-end processing module in the present application.

[0043] Figure 6 is a working effect schematic diagram of the present application when there is no blood flow in the internal fistula.

[0044] Figure 7 is a working effect schematic diagram of the present application when there is blood flow in the internal fistula.

[0045] Figure 8is the front-end test module structure design scheme in the embodiment 2 of the present application.

[0046] Figure 9 is the front-end test module structure design scheme in the embodiment 3 of the present application.

[0047] In the above-mentioned drawings, each figure number mark represents:

[0048] 1 top PDMS package, 2 rear-end processing module, 21 circuit substrate, 22 signal conditioning circuit, 23 microprocessor chip, 24 battery, 25 Bluetooth module, 3 connecting wire, 4 middle PDMS partition package, 5 front-end test module, 51 heater, 52 temperature sensor, 53 flexible circuit substrate, 6 bottom PDMS package. DETAILED DESCRIPTION

[0049] The purposes, technical solutions and advantages of the embodiments of the present application will be further described in detail below with reference to the drawings in the embodiments of the present application. It should be understood that the specific embodiments described herein are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] The various components and raw materials used in the present application are all commonly used commercially available products in the art, for example

[0051] The PDMS package uses SYLGARD184 polydimethylsiloxane film produced by Dow Corning Company of the United States;

[0052] The amplifier uses OPA2277UA precision operational amplifier produced by Texas Instruments of the United States;

[0053] The microprocessor chip uses STM32F103C8T6 series chip produced by STMicroelectronics of Italy;

[0054] The analog-to-digital converter uses ADS1148 sixteen-bit analog-to-digital converter produced by Texas Instruments of the United States;

[0055] The Wheatstone bridge and low-pass filter use conventional components in the art.

[0056] Embodiment 1

[0057] As Figure 1 and Figure 2The wearable non-invasive arteriovenous fistula blood flow monitoring device shown includes a top PDMS package 1, a back-end processing module 2, a connecting wire 3, a middle PDMS barrier package 4, a front-end testing module 5, and a bottom PDMS package 6. The back-end processing module 2 includes a circuit substrate 21, a signal conditioning circuit 22, a microprocessor chip 23, a battery 24, and a Bluetooth module 25. The front-end testing module 5 includes a heater 51, a temperature sensor 52, and a flexible circuit substrate 53. The top PDMS package 1, back-end processing module 2, middle PDMS barrier package 4, front-end testing module 5, and bottom PDMS package 6 are all sheet-like and stacked to form the main body of the device. The middle PDMS barrier package 4 and the bottom PDMS package 6 are bonded to the front-end testing module 5, and the PDMS package 1 is bonded to the back-end processing module 2. The back-end processing module 2 and the front-end processing module are electrically connected by the connecting wire 3, which passes through a rectangular notch on the edge of the middle PDMS barrier package 4.

[0058] In a preferred embodiment, such as Figures 3-7 As shown, the flexible circuit substrate 53 of the front-end test module 5 is a flexible sheet made of insulating high-temperature resistant polymer material (in this embodiment, SYLGARD184 polydimethylsiloxane film manufactured by Dow Corning Incorporated can be used), and the heater 51 adopts a circular, mosquito coil-shaped metal resistance heating wire (such as...). Figure 3 As shown, the temperature sensor 52 is a 0402NTC thermistor, and the supporting circuit uses copper wires directly printed on the flexible circuit substrate 53. In this embodiment, a circular integral heater and a semiconductor thermistor are used, and the thermistor is located in the center of the heater.

[0059] In this embodiment, the front-end testing module 5 includes a heater 51 and a temperature sensor 52, with the centers of the two devices coinciding and their respective perpendicular bisectors intersecting the centerline of the fistula; as shown Figure 3 As shown, there are concentrated external connector interfaces at the edge of the front-end test module 5, and one end of the connecting wire 3 is connected to the interface (e.g., Figure 2 Two of the wires are connected to the heater 51 and the battery 24 to power the heater 51, while the other four wires are connected to the temperature sensor 52 and the signal conditioning circuit 22.

[0060] In this embodiment, the circuit substrate of the back-end processing module 2 is made of flexible insulating material (in this embodiment, SYLGARD184 polydimethylsiloxane film manufactured by Dow Corning Incorporated can be used). The signal conditioning circuit 22 includes a Wheatstone bridge, a low-pass filter, an operational amplifier, and an analog-to-digital converter. The Wheatstone bridge and the low-pass filter use a resistor-capacitor network. The operational amplifier is a precision operational amplifier. The analog-to-digital converter is a 12-bit analog-to-digital converter. The wireless communication module 25 uses an HC05 Bluetooth module. The microprocessor chip 23 uses an STM32F103C8T6 chip. The battery 24 uses a button cell battery.

[0061] In this embodiment, the temperature sensor 52 of the front-end test module 5 is connected to the arm under test of the Wheatstone bridge through an external connector interface. The Wheatstone bridge is connected to a low-pass filter, the low-pass filter is connected to an operational amplifier, the operational amplifier is connected to an analog-to-digital converter, the analog-to-digital converter is connected to a microprocessor chip 23, the microprocessor chip is connected to a wireless communication module 25, and the battery 24 supplies power to all IC components.

[0062] In this implementation plan, such as Figure 4 As shown, when the device is in use, device A is placed on the patient's arm surface. The perpendicular bisector of heater 51 intersects the fistula axis B, and the perpendicular bisectors of the two temperature sensors 52 also intersect the fistula axis. The front-end test module 5 is separated from the patient's skin only by a bottom PDMS package 6.

[0063] In this embodiment, the device heats the skin using a heater 51 and measures the temperature at a point on the skin surface using a temperature sensor 52. Figure 5 and Figure 6 As shown, Figure 5 and Figure 6 The lower half of each image shows a cross-sectional view of the fistula and surrounding tissues, while the upper half shows the temperature distribution along a straight line on the body surface. When there is no blood flow in the vessel, the temperature distribution line is symmetrical, with the line on one side of the symmetry being monotonous, indicating a higher temperature at the temperature sensor at the symmetry line. When there is blood flow in the vessel, the temperature distribution line is also symmetrical, but the line on one side of the symmetry line is not monotonous, indicating a lower temperature at the temperature sensor at the symmetry line. The temperature at the temperature sensor changes significantly with and without blood flow, and the magnitude of this change varies with the amount of blood flow.

[0064] In this implementation plan, such as Figure 7As shown, the front-end testing module 5 and the back-end processing module 2 jointly implement three functions: signal conversion, signal processing, and signal transmission. The temperature sensor 52 of the front-end testing module 5 uses a 0402NTC thermistor, whose resistance decreases as temperature increases. This allows different resistance values ​​to be used to represent different temperatures at the sensor's location in real time. The change in resistance of the temperature sensor 52 causes an imbalance in the Wheatstone bridge "WB" in the signal conditioning circuit 22, resulting in an output voltage signal carrying the temperature signal of the measurement point. This voltage signal is then filtered to remove high-frequency noise, amplified by an operational amplifier, and converted into a digital signal by an analog-to-digital converter. The digital signal is then transmitted to the microprocessor chip 23 for transmission. The microprocessor chip 23 delivers fistula blood flow information to the patient's communication device via the wireless communication module 25. The communication device calculates the flow rate based on the relationship between temperature change and flow rate, and the patient reads this information through application software.

[0065] Example 2

[0066] like Figure 1 and Figure 2 The wearable non-invasive arteriovenous fistula blood flow monitoring device shown includes a top PDMS package 1, a back-end processing module 2, a connecting wire 3, a middle PDMS partition package 4, a front-end testing module 5, and a bottom PDMS package 6. The back-end processing module includes a circuit substrate 21, a signal conditioning circuit 22, an analog-to-digital converter and a microprocessor chip 23, a battery 24, and a Bluetooth module 25. The front-end testing module includes a heater 51, a temperature sensor 52, and a flexible circuit substrate 53. The top PDMS package 1, back-end processing module 2, middle PDMS partition package 4, front-end testing module 5, and bottom PDMS package 6 are all sheet-like and stacked to form the main body of the device. The middle PDMS partition package 4 and the bottom PDMS package 6 are bonded to the front-end testing module 5, and the PDMS package 1 is bonded to the back-end processing module 2. The back-end processing module 2 and the front-end processing module are electrically connected by the connecting wire 3, which passes through a rectangular notch on the edge of the middle PDMS partition package 4.

[0067] In a preferred embodiment, such as Figures 4-8 As shown, the flexible circuit substrate 53 of the front-end test module 5 is a flexible sheet made of insulating high-temperature resistant polymer material, and the heater 51 uses a rhomboid-shaped mosquito coil-shaped metal resistance heating wire (such as...). Figure 8 As shown, the temperature sensor 52 is a 0402NTC thermistor, and the supporting circuit uses copper wires directly printed on the flexible circuit substrate 53. In this embodiment, a diamond-shaped integral heater and a semiconductor thermistor are used, and the thermistor is not located in the center of the heater.

[0068] In the present embodiment, the front-end testing module 5 comprises a heater 51 and a temperature sensor 52, the centers of the two devices do not coincide, and the median lines of the two devices respectively intersect the central line of the internal fistula; as shown in Figure 3 , the edge of the front-end testing module 5 has a concentrated external connector interface, and a section of the connecting wire 3 is connected to the interface (as shown in Figure 2 ), two wires in the section are connected to the heater 51 and the battery 24 to realize the power supply of the heater 51, and the other four wires are connected to the temperature sensor 52 and the signal conditioning circuit 22.

[0069] In the present embodiment, the circuit substrate of the back-end processing module 2 adopts a flexible insulating material, the signal conditioning circuit 22 comprises a Wheatstone bridge, a low-pass filter, an amplifier and an analog-to-digital converter, the Wheatstone bridge and the low-pass filter adopt a resistance-capacitance network, the amplifier adopts a precision operational amplifier, the analog-to-digital converter adopts a 12-bit analog-to-digital converter, the wireless communication module 25 adopts an HC05 Bluetooth module, the micro-processing chip 23 adopts an STM32F103C8T6 chip, and the battery 24 adopts a button cell.

[0070] In the present embodiment, the temperature sensor 52 of the front-end testing module 5 is connected to the measured arm of the Wheatstone bridge through the external connector interface, the Wheatstone bridge is connected to the low-pass filter, the low-pass filter is connected to the operational amplifier, the operational amplifier is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the micro-processing chip 23, the micro-processing chip is connected to the wireless communication module 25, and the battery 24 supplies power to all IC components.

[0071] In the present embodiment, as shown in Figure 4 , when the device is in use, the device is placed on the body surface of the patient's arm, the median line of the heater 51 intersects the axis of the internal fistula, the median lines of the two temperature sensors 52 also intersect the axis of the internal fistula, and the front-end testing module 5 is separated from the patient's skin only by a layer of bottom PDMS packaging 6.

[0072] In the present embodiment, the device heats the skin through the heater 51 and measures the temperature at a point on the body surface through the temperature sensor 52. As shown in Figure 5 and Figure 6 , the temperature sensor 52 is connected to the measured arm of the Wheatstone bridge through the external connector interface, the Wheatstone bridge is connected to the low-pass filter, the low-pass filter is connected to the operational amplifier, the operational amplifier is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the micro-processing chip 23, the micro-processing chip is connected to the wireless communication module 25, and the battery 24 supplies power to all IC components. Figure 5 Figure 6 ​The lower part of each is a cross-sectional structure diagram of the internal fistula and the surrounding tissue, and the upper part is a temperature distribution diagram line on the straight line where the cross section is located. When there is no flow in the blood vessel, the temperature distribution diagram line is symmetrical on the left and right, the diagram line on one side of the symmetry line is monotonic, and the temperature sensor at the symmetry line has a higher temperature; when there is flow in the blood vessel, the temperature distribution diagram line is symmetrical on the left and right, the diagram line on one side of the symmetry line is not monotonic, and the temperature sensor at the symmetry line has a lower temperature. When there is flow and when there is no flow, the temperature at the temperature sensor changes significantly, and the amplitude of this change changes with the size of the blood flow.

[0073] In the present embodiment, as shown in Figure 7 The front-end test module 5 and the back-end processing module 2 jointly realize three functions, including signal conversion, signal processing, and signal transmission. The temperature sensor 52 of the front-end test module 5 adopts a 0402 NTC thermistor, the resistance value of which decreases with the increase of temperature, so as to represent different temperatures at the position of the sensing sensor with different resistance values in real time; the resistance value change of the temperature sensor 52 causes the Wheatstone bridge “WB” in the signal conditioning circuit 22 to be unbalanced, so as to output a voltage signal carrying the temperature signal of the measurement point, and then the high-frequency noise is filtered out through the filter, the signal voltage value is amplified through the operational amplifier, and the digital signal is converted through the analog-to-digital converter, which is transmitted to the micro-processing chip 23 for transmission; the micro-processing chip 23 delivers the internal fistula blood flow information to the communication device of the patient through the wireless communication module 25, the communication device calculates the flow size through the relationship between the temperature change amplitude and the flow, and the patient reads the information through the application software.

[0074] Example 3

[0075] As shown in Figure 9 In the present embodiment, a rectangular split-type heater and a semiconductor thermistor are adopted, and the thermistor is located at the center of the heater. The rest is the same as example 1.

[0076] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art within the technical scope disclosed by the present application, according to the technical solution and the inventive concept of the present application, can make equivalent replacement or change, which should be covered in the protection scope of the present application.

Claims

1. A wearable arteriovenous fistula blood flow non-invasive monitoring device, characterized in that, The device comprises a top PDMS package (1), a back-end processing module (2), a middle PDMS partition package (4), a front-end testing module (5), and a bottom PDMS package (6); the middle PDMS partition package (4) and the bottom PDMS package (6) are bonded with the front-end testing module (5), the top PDMS package (1) is bonded with the back-end processing module (2), and the back-end processing module (2) is electrically connected with the front-end testing module (5) through a connecting wire (3); The front-end testing module (5) comprises a heater (51), a temperature sensor (52), a flexible circuit substrate (53), and a matching circuit; the heater (51) and the temperature sensor (52) are arranged on the flexible circuit substrate (53); the front-end testing module (5) is provided with an external connector interface which is concentrated on the edge of the module; the matching circuit supplies power to the heater (51) or conducts the voltage signal of the temperature sensor (52) through the interface; The back-end processing module (2) comprises a circuit substrate (21), a signal conditioning circuit (22) arranged on the circuit substrate (21), a micro-processing chip (23), a battery (24), and a wireless communication module (25); The signal conditioning circuit (22) comprises a Wheatstone bridge, a low-pass filter, an operational amplifier, and an analog-to-digital converter; The temperature sensor (52) of the front-end processing module is connected with the measured arm of the Wheatstone bridge through the external connector interface; the Wheatstone bridge is connected with the low-pass filter; the low-pass filter is connected with the operational amplifier; the operational amplifier is connected with the analog-to-digital converter; the analog-to-digital converter is connected with the micro-processing chip (23); and the micro-processing chip (23) is connected with the wireless communication module (25); The front-end testing module (5) and the back-end processing module (2) adopt a stacked layout, and the back-end processing module (2) is stacked on the front-end testing module (5).

2. The wearable arteriovenous fistula blood flow non-invasive monitoring device according to claim 1, wherein, The flexible circuit substrate (53) is a flexible sheet made of an insulating high-temperature-resistant polymer material; The heater (51) is a ceramic heating sheet or a metal resistance heating wire; The temperature sensor (52) is a thermistor or a metal coil; The matching circuit adopts copper wires or aluminum wires.

3. The wearable arteriovenous fistula blood flow non-invasive monitoring device according to claim 1, wherein, In the front-end testing module (5), one heater and one temperature sensor are arranged on the flexible circuit substrate in a flat manner; the area of the temperature sensor is smaller than that of the heater; the temperature sensor is located at the center of the range of the heater, or at other positions within the range of the heater, or is surrounded by the heater, or is located outside the range of the heater.

4. The wearable arteriovenous fistula blood flow non-invasive monitoring device according to claim 1, wherein, The top PDMS package (1) uniformly covers the surfaces of various devices in the front-end testing module, thereby achieving external insulation at positions other than the interface.

5. The wearable device for non-invasive monitoring of blood flow in an internal arteriovenous fistula according to claim 1, characterized in that, In the front-end testing module (5), the heater adopts a whole layout or a split layout, i.e., the heater adopts one entire heating sheet or one entire resistance wire, or adopts a combination of multiple heating sheets or multiple resistance wires at corresponding positions. The shape of the heater (5) is rectangular, rhombic, circular, or elliptical.

6. The wearable device for non-invasive monitoring of blood flow in an internal arteriovenous fistula according to claim 1, characterized in that, The temperature sensor of the front end test module (5) adopts an integral layout or a split layout, that is, each temperature sensor adopts a thermistor or a metal resistance wire, or adopts an array combination of multiple thermistors or multiple metal resistance wires at corresponding positions.

7. The wearable device for non-invasive monitoring of blood flow in an internal arteriovenous fistula according to claim 1, characterized in that, The circuit substrate (21) adopts a flexible insulating material, the low-pass filter adopts a resistance-capacitance network, the operational amplifier, the analog-to-digital converter, the wireless communication module (25), and the micro processing chip (23) adopt small commercial modules with a patch type package, and the battery (24) adopts a button cell.

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