Cuff-free calibration-free flexible patch type blood pressure detection system based on ultrasonic echo method

Abstract

The invention discloses a cuff-free calibration-free flexible patch type blood pressure detection system based on an ultrasonic echo method, and relates to the technical field of blood pressure detection of biomedical engineering. Comprising a transmitting and receiving integrated probe, a transmitting circuit, an amplitude limiting circuit, an amplifying circuit, a filter circuit, an A / D conversion circuit, an FPGA chip, a Bluetooth module and a mobile terminal. Wherein the FPGA chip outputs a high-frequency signal, a low-voltage signal is converted into a negative high-voltage signal through the transmitting circuit to drive the ultrasonic transducer, the ultrasonic transducer generates ultrasonic waves under excitation and receives an echo signal from a blood vessel wall, the echo signal firstly passes through the amplitude limiting circuit, and the high-voltage component is limited while the signal is received; signals sequentially pass through the amplification circuit and the filter circuit, finally voltage signals are converted into digital signals through the A / D conversion circuit, and after the digital signals are processed by the FPGA chip, data are sent to a mobile terminal through the Bluetooth module. The accuracy of blood pressure detection is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of blood pressure detection in biomedical engineering, and more specifically, to a cuffless and calibration-free flexible patch type blood pressure detection system based on the ultrasonic echo method. Background Art

[0002] Cuffed blood pressure detection: In the prior art, traditional blood pressure detection mainly relies on cuffed devices. By inflating the cuff to wrap around the upper arm and using a pressure sensor to measure, the blood pressure value range can be obtained.

[0003] Cuffless technology: In recent years, cuffless blood pressure detection devices have emerged, such as those using the principle of photoplethysmography (PPG), ultrasonic waves, or skin impedance, etc., and performing blood pressure detection based on blood flow characteristics. These devices usually detect at parts such as the wrist, finger, or earlobe, which are convenient to carry.

[0004] Smart wearable devices: Some smart watches and health trackers have also started to integrate blood pressure detection functions and use non-invasive methods for data collection. Such products are connected to mobile phone applications to provide real-time data analysis and health management.

[0005] Problems and disadvantages of the prior art:

[0006] Although traditional ultrasonic probes can continuously detect blood pressure. However, such devices are rigid and need to be held by an operator during detection, with high requirements for holding stability. Therefore, it is impossible to achieve long-term fitting to the human skin for blood pressure monitoring.

[0007] (1) Lack of non-invasive, long-term and high-precision blood pressure monitoring devices

[0008] Although some commercial cuffless blood pressure monitoring devices have emerged on the market, these devices are mainly based on optical detection methods and are easily affected by skin color, ambient light, and other external factors, resulting in insufficient measurement accuracy and difficulty in meeting clinical requirements. In addition, other cuffless blood pressure monitoring methods are still in the research stage and are only tested in a small-scale population, and no devices meeting clinical standards have been developed.

[0009] (2) The ultrasonic hardware system is large in volume

[0010] Currently, systems based on ultrasonic detection methods are usually large in volume, and their excitation modules mostly rely on pulse generators, failing to achieve miniaturization and high integration of electronic devices. This limits the portability of the device and is not conducive to the application of long-term blood pressure monitoring.

[0011] Related researchers have developed flexible ultrasonic sensors that can adhere to the skin and continuously detect blood pressure. However, current flexible ultrasonic devices still have the following problems: (1) Insufficient resolution and sensitivity. Due to the acoustic properties of flexible materials restricting the generation and reception of high-frequency ultrasound, the image resolution and sensitivity of flexible ultrasonic devices are generally lower than those of traditional rigid probes, making it difficult to clearly display tiny structures or lesions; (2) Material and manufacturing challenges. It is difficult for flexible materials to maintain consistent acoustic properties during the manufacturing process, with poor durability and stability. They are prone to aging or damage during long-term use, and the process is complex and costly; (3) Complex signal processing and imaging algorithms. The shape change of the flexible probe increases the difficulty of signal processing. The signal processing and imaging algorithms of the flexible probe are complex and vulnerable to noise interference, affecting image quality.

[0012] Therefore, it is an urgent problem for those skilled in the art to propose a cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method to solve the difficulties existing in the prior art. Summary of the Invention

[0013] In view of this, the present invention provides a cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method, which solves the technical problems such as hard probe material, insufficient resolution and sensitivity, and complex signal processing and imaging algorithms existing in the use of traditional blood pressure detection devices.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] A cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method, which mainly consists of an external hardware circuit, an FPGA chip, and a mobile terminal.

[0016] The cuffless and calibration-free blood pressure monitoring system designed by the present invention has high measurement accuracy and can achieve long-term and accurate blood pressure monitoring under the condition of no cuff constraint, providing an effective solution for continuous blood pressure monitoring.

[0017] A cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method, including: a transceiver probe, a transmitting circuit, a limiting circuit, an amplifying circuit, a filtering circuit, an A / D conversion circuit, an FPGA chip, a Bluetooth module, and a mobile terminal;

[0018] Among them, the FPGA chip outputs a high-frequency signal, which is converted into a negative high-voltage signal by the transmitting circuit to drive the ultrasonic transducer. The ultrasonic transducer generates ultrasonic waves under excitation and receives the echo signal from the blood vessel wall. The echo signal first passes through the limiting circuit, which limits the high-voltage component while receiving the signal to protect the subsequent circuit;

[0019] Subsequently, the signal is successively subjected to gain processing by an amplification circuit and noise suppression by a filtering circuit, and finally the voltage signal is converted into a digital signal via an A / D conversion circuit. After the FPGA chip processes the digital signal, the data is sent to the mobile terminal through a Bluetooth module.

[0020] Optionally, the transmitting circuit includes: a high-voltage excitation circuit and a level conversion circuit.

[0021] Optionally, the transceiver probe uses a flexible ultrasonic sensor.

[0022] Optionally, the FPGA chip realizes wearable blood pressure detection by calculating the arrival time of the ultrasonic echo signal and combining it with a blood pressure transmission model.

[0023] Optionally, the mobile terminal is an Android client.

[0024] Optionally, it further includes: a power management module, which is powered by a 12V DC voltage source.

[0025] Optionally, it further includes: a cloud server, which is used to realize remote storage and management of data, support long-term preservation and remote access of data.

[0026] From the above technical solutions, it can be seen that compared with the prior art, the present invention discloses a cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method. Its beneficial effects are as follows:

[0027] 1) Improve the image resolution and information processing of the device:

[0028] Adopt a higher-frequency micro ultrasonic transducer array to improve spatial resolution and signal sensitivity, capture arterial wall movement and hemodynamic parameters more accurately, obtain more comprehensive vascular structure and blood flow information through multi-angle scanning and three-dimensional reconstruction technology, improve the accuracy of blood pressure measurement, and develop an adaptive signal processing algorithm to effectively suppress noise interference and extract high-quality ultrasonic echo signals;

[0029] 2) Improve the flexibility and wearability of the sensor:

[0030] Most traditional electronic strain sensors are based on metal and semiconductor materials, with poor flexibility and strong discomfort when in contact with human skin; the present invention uses a flexible ultrasonic sensor, taking advantage of its high elasticity, stretchability and biocompatibility to improve the flexibility and wearability of the sensor, making the device fit the human skin better and enhancing the user's comfort;

[0031] 3) Realize real-time continuous detection:

[0032] Train a deep learning model using a large amount of clinical data to establish a non - linear mapping relationship between multi - modal physiological signals and blood pressure values; denoise, filter, and extract features from multi - modal sensing signals to improve signal quality and provide high - precision input for the deep learning model.

[0033] 4) Calibration - free detection:

[0034] The present invention proposes a cuffless calibration - free flexible patch - type blood pressure detection system based on the ultrasonic echo method, whose core combines ultrasonic echo dynamic tracking, multi - modal sensing fusion, and deep learning modeling techniques. The patch uses a flexible piezoelectric array to capture the subtle changes in arterial wall displacement and blood vessel diameter in real - time through high - frequency ultrasonic waves. At the same time, it integrates a Doppler module optimized by MEMS technology to synchronously monitor blood flow velocity and the dynamic characteristics of the blood vessel wall, forming a multi - dimensional hemodynamic signal input. To achieve calibration - free operation, the system introduces a deep learning model based on the Residual Neural Network (ResNet). By training over 100,000 sets of clinical arterial wall displacement - blood pressure waveform paired data, an end - to - end physical correlation model is constructed to directly map the non - linear relationship between ultrasonic echo features and blood pressure waveforms, circumventing the limitations of traditional methods that rely on individual calibration. Brief Description of the Drawings

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following - described drawings are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0036] Figure 1 It is a structural diagram of a cuffless calibration - free flexible patch - type blood pressure detection system provided by the present invention;

[0037] Figure 2 It is a schematic diagram of the principle of measuring blood vessel diameter by the pulse - echo method provided by the present invention;

[0038] Figure 3 It is a schematic diagram of the overall structure and hierarchical structure of the flexible ultrasonic sensor device provided by the present invention;

[0039] Figure 4 It is the overall software block diagram of the system provided by the present invention;

[0040] Figure 5 It is the excitation amplification circuit diagram provided by the present invention;

[0041] Figure 6 It is the echo amplification circuit diagram provided by the present invention;

[0042] Figure 7The AD conversion and external attenuation circuit provided by the present invention. Detailed implementation manners

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] The basic principle of ultrasonic pulse-echo method detection:

[0045] See Figure 2 As shown, ultrasonic waves are divided into continuous waves and pulse waves. Continuous waves are waves radiated by a continuously vibrating wave source without gaps in the middle, while pulse waves are time-dependent and can control the starting point of their emission and the pulse repetition period. Generally, the ultrasonic pulse width is very narrow. Compared with the pulse emission time, the propagation time of ultrasonic waves in the human body is relatively long, so the quiescent period is also slightly longer. During the quiescent period, the ultrasonic transmitter can act as a receiver to receive the reflected acoustic wave signals. The ultrasonic pulse-echo method is a method of transmitting ultrasonic pulse waves to the detected object, receiving the echo signals after reflection from the target interface, and obtaining the position, distance, and motion state of the detected object by analyzing the amplitude, frequency change, and generation time of the echo signals.

[0046] Assume that the artery to be detected is rotationally symmetric, that is, the cross-section of the artery can be regarded as a circle. Then the relationship between the cross-sectional area A(t) of the artery and the artery diameter d(t) is expressed as:

[0047]

[0048] The maximum arterial cross-sectional area A s is defined as the arterial cross-sectional area at peak systole, and the minimum value between A(t) and A s is defined as the arterial cross-sectional area A d at end-diastole. The functional relationship between the blood pressure waveform P(t) and the arterial cross-sectional area A(t) is expressed as:

[0049] P(t) = p0e γ A(t)

[0050] In the formula, P(t) represents the arterial blood pressure at time t, and p0 and γ represent constants. In addition, if the systolic blood pressure and diastolic blood pressure are respectively represented by P S and P d , the vascular cross-sectional area is represented by A S and A d . By solving for p0 and γ, we can obtain:

[0051]

[0052] In the arterial vascular mechanics model, α represents the elastic stiffness parameter of the blood vessel wall, and P d represents the intravascular pressure during diastole, and A d corresponds to the maximum cross-sectional area of the blood vessel during diastole. It can be derived that:

[0053]

[0054] See Figure 1 As shown, a cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method includes: a transceiver probe, a transmitting circuit, a limiting circuit, an amplifying circuit, a filtering circuit, an A / D conversion circuit, an FPGA chip, a Bluetooth module, and a mobile terminal;

[0055] Among them, the FPGA chip outputs a high-frequency signal. The transmitting circuit converts the low-voltage signal into a negative high-voltage signal to drive the ultrasonic transducer. The ultrasonic transducer generates ultrasonic waves under excitation and receives the echo signal from the blood vessel wall. The echo signal first passes through the limiting circuit to limit the high-voltage component while receiving the signal to protect the subsequent circuit;

[0056] Subsequently, the signal is successively subjected to gain processing through the amplifying circuit and noise suppression through the filtering circuit. Finally, the voltage signal is converted into a digital signal via the A / D conversion circuit. After the FPGA chip processes the digital signal, the data is sent to the mobile terminal through the Bluetooth module.

[0057] Specifically, the patch adopts a three-dimensional directional sweat transport structure (such as a bionic liquid diode design) and an MXene-enhanced flexible circuit to ensure breathability and signal stability during long-term wear, and realizes low-power data transmission and real-time feedback through wireless near-field communication technology; Clinical verification shows that in complex scenarios such as exercise and posture change, the mean absolute errors of systolic and diastolic blood pressures of this system are respectively lower than 1.8 mmHg and 1.0 mmHg, and the accuracy is comparable to that of invasive arterial catheters, and no initial calibration steps are required to achieve the purpose of long-term monitoring; According to the individual differences of users, personalized parameter calibration is carried out to improve the accuracy and reliability of blood pressure measurement.

[0058] Specifically, information processing, module control, and display interaction are all based on the FPGA chip, and the FPGA chip can ensure the normal operation of the entire system.

[0059] Furthermore, the transmitting circuit includes: a high-voltage excitation circuit and a level conversion circuit.

[0060] Furthermore, the transceiver probe adopts a flexible ultrasonic sensor.

[0061] Specifically, the flexible ultrasonic sensor uses a piezoelectric material with the most stable mechanical properties, the highest relative dielectric constant, and the best flexibility.

[0062] Specifically, refer to Figure 3 As shown, the schematic diagram of the overall structure and hierarchical structure of the flexible ultrasonic sensor device. The flexible ultrasonic sensor mainly consists of a piezoelectric layer, a serpentine electrode, a flexible substrate, and a wire, and its structure is a sandwich structure. Among them, the piezoelectric layer is the core of the ultrasonic sensor, which emits and receives ultrasonic waves through the direct and inverse piezoelectric effects. The electrode is connected to the piezoelectric layer through an adhesive layer. The electrical signal excites the piezoelectric layer through the electrode to emit ultrasonic waves, and the received ultrasonic echo signal is converted into an electrical signal by the piezoelectric layer and then transmitted out through the electrode. The flexible substrate encapsulates the ultrasonic sensor, making it flexible and capable of conforming to complex surfaces. The wire is connected to the backend hardware device, transmits the electrical excitation signal to the ultrasonic sensor, and transmits the electrical signal converted from the ultrasonic echo to the acquisition device for data processing and analysis.

[0063] Furthermore, the FPGA chip realizes wearable blood pressure detection by calculating the arrival time of the ultrasonic echo signal and combining it with the blood pressure transmission model.

[0064] Specifically, by combining ultrasonic echo dynamic tracking, multi-modal sensing fusion, and deep learning modeling techniques, the initial calibration step is not required to achieve the purpose of long-term monitoring.

[0065] Furthermore, the mobile terminal is an Android client.

[0066] Furthermore, it also includes: a power management module, which is powered by a 12V DC voltage source.

[0067] Furthermore, it also includes: a cloud server, which is used to realize remote storage and management of data, and supports long-term preservation and remote access of data.

[0068] Specifically, from the acquisition, processing, and transmission of the signal acquisition terminal, to the Android client for signal preprocessing and blood pressure calculation, while displaying the signal waveform and the calculated parameters after processing, and finally realizing the cloud storage of data.

[0069] Specifically, refer to Figure 4 As shown, the signal acquisition terminal integrates the collected data and then transmits it to the Android client. After receiving the data, the Android client displays and preprocesses it, and then uploads it to the cloud server for storage in the database. The specific implementation is as follows:

[0070] The signal acquisition terminal synchronizes the analog signal through a piezoelectric ultrasonic transducer, transmits the data to the main controller, the main controller integrates the data, and finally sends it to the Android client in the form of a data packet through low-power Bluetooth.

[0071] The Android client receives the data from the signal acquisition terminal, displays and preprocesses it. First, the received data packet is separated, and then the electrocardiogram signal in it is preprocessed for quality evaluation and denoising. Then, the waveform characteristic values of the analog signal are calculated. Finally, the blood pressure value is calculated by the blood pressure regression model, and the result data is uploaded to the cloud server through 5G at the same time.

[0072] The cloud server receives the data transmitted by the client, establishes a database, permanently stores the data, and also provides a historical record query function.

[0073] In a specific embodiment, the system includes a high-voltage excitation circuit, an echo amplification circuit, and an A / D sampling circuit.

[0074] High-voltage excitation circuit:

[0075] The transmitting circuit is powered by low voltage (12V power supply, meeting the national safety voltage standard). An instantaneous sharp pulse signal up to 60V is generated through the instantaneous discharge of the energy storage element, so as to drive the piezoelectric sensor to work normally. Since the duration of the instantaneous high-voltage pulse is extremely short and the generated energy is small, it will not cause damage to the human body. The pulse excitation amplification circuit is designed as Figure 5 shown.

[0076] Figure 5 The upper N and lower P type push-pull circuit composed of NPN and PNP transistors Q4 and Q2 in

[0077] Echo amplification circuit:

[0078] such as Figure 6 shown non-inverting amplifier circuit, the amplification factor relationship between the input voltage V in and the output voltage V out is shown in the following formula:

[0079]

[0080] Different voltage amplification factors can be achieved by changing the ratio relationship between f R g and R

[0081] A / D sampling circuit:

[0082] As Figure 7 shown in the schematic diagram of the high-speed AD conversion and external attenuation circuit, 3PA1030 works under the drive of the clock (CLK). 3PA1030 has an on-chip sample-and-hold amplifier built-in and adopts a multi-stage differential pipelined architecture, ensuring no missing codes within the full temperature range at a data conversion rate of 50 MSPS. 3PA1030 integrates a reference source internally, and an external high-precision reference can also be selected according to the system requirements to meet the system's requirements. The data output by 3PA1030 is represented in binary format. When the input analog voltage exceeds the range, the OVR signal will be pulled high; when the input analog voltage is within the range, the OVR signal is at a low level. Therefore, the OVR signal can be used to determine whether the input analog voltage is within the measurement range. In addition, 3PA1030 has an OE signal. When this signal is high, the output of 3PA1030 is in a high-impedance state, and when it is low, it can output normally.

[0083] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0084] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cuffless and calibration-free flexible patch type blood pressure detection system based on ultrasonic echo method, characterized in that, Including: A transceiver probe, a transmitting circuit, a limiting circuit, an amplifying circuit, a filtering circuit, an A / D conversion circuit, an FPGA chip, a Bluetooth module, and a mobile terminal; Among them, the FPGA chip outputs a high-frequency signal, and the transmitting circuit converts the low-voltage signal into a negative high-voltage signal to drive the ultrasonic transducer. The ultrasonic transducer generates ultrasonic waves under excitation and receives the echo signal from the blood vessel wall. The echo signal first passes through the limiting circuit to limit the high-voltage component while receiving the signal, which is used to protect the subsequent circuits; Subsequently, the signal is successively subjected to gain processing through the amplifying circuit and noise suppression through the filtering circuit. Finally, the voltage signal is converted into a digital signal via the A / D conversion circuit. After the FPGA chip processes the digital signal, the data is sent to the mobile terminal through the Bluetooth module.

2. The cuffless and calibration-free flexible patch type blood pressure detection system based on the ultrasonic echo method according to claim 1, wherein The transmitting circuit includes: a high-voltage excitation circuit and a level conversion circuit.

3. A cuffless and calibration-free flexible patch type blood pressure detection system based on the ultrasonic echo method according to claim 1, wherein The transceiver probe uses a flexible ultrasonic sensor.

4. A cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method according to claim 1, wherein, The FPGA chip realizes wearable blood pressure detection by calculating the arrival time of the ultrasonic echo signal and combining with the blood pressure transmission model.

5. The cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method according to claim 1, wherein, The mobile terminal is an Android client.

6. The cuffless and calibration-free flexible patch-type blood pressure detection system based on the ultrasonic echo method according to claim 1, wherein, Also including: A power management module, powered by a 12V DC voltage source.

7. A cuffless and calibration-free flexible patch type blood pressure detection system based on the ultrasonic echo method according to claim 1, characterized in that Also including: a cloud server, which is used to realize remote storage and management of data, and supports long-term preservation and remote access of data.

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