Method and system for dynamically monitoring wound healing area through bioelectrical impedance technology

Abstract

The invention discloses a method and system for dynamically monitoring the wound healing area through a bioelectrical impedance technology, and belongs to the field of biomedical engineering. A mathematical model of the skin surface impedance and the wound surface area is provided, and quantitative evaluation of the wound area is achieved by detecting the change condition of the impedance value. According to the biological impedance acquisition system for dynamically monitoring the wound area, quantitative monitoring of the wound healing state is achieved, the method is different from a clinical visual inspection method, and a new evaluation device is provided; non-contact non-invasive detection is realized, the possibility of secondary infection is avoided, the pain of a patient is reduced, and the pressure of medical resources is relieved; real-time uninterrupted monitoring is achieved, and the clinical treatment effect is optimized; the dual-calibration impedance acquisition device is realized, and the measurement accuracy is improved.

Description

Technical Field

[0001] The invention belongs to the field of biomedical engineering and relates to a method and system for dynamically monitoring wound healing area using bioelectrical impedance technology. Background Art

[0002] The treatment and healing of open wounds is a common and thorny problem faced by many clinical departments. The monitoring and evaluation of wound healing is a key way to prevent disease progression, guide treatment plans, prevent complications, and improve quality of life. Therefore, quantitative monitoring and analysis of wound healing has gradually developed into an important clinical need for auxiliary wound treatment.

[0003] At present, clinical wound healing monitoring is mainly carried out through appearance observation, exudate evaluation, bacterial culture and other methods. The wound healing state is evaluated by observing information such as wound size, swelling, color, temperature, etc. The inflammatory state of the wound is evaluated by methods such as blood inflammatory detection, exudate evaluation, and bacterial culture. The above-mentioned evaluation method requires multiple changes of gauze, which is easy to cause infection, and the evaluation results depend on the clinical experience of the doctor. In recent years, some studies have used spectral imaging technology and electrochemical technology to measure physical and chemical indicators such as cell number, hyperspectral reflectivity, secretion pH, and inflammatory factors in the healing stage to evaluate the wound healing state. Although the wound condition can be estimated, it is limited to the laboratory research stage and the detection process is long and the equipment is complex, which is difficult to meet the real-time, portable, and miniaturized clinical monitoring needs. Bioimpedance technology has the advantages of safety and non-invasiveness, simple operation, multi-parameter measurement, dynamic monitoring, wearable and portable. The technology is applied to skin impedance analysis, human body composition analysis, disease diagnosis assistance and other fields, but has not yet been applied and promoted in the field of real-time monitoring and evaluation of wound healing. The present invention is aimed at the clinical needs of wound healing monitoring, combined with the advantages of bioimpedance technology, and provides a method and system for dynamically monitoring the healing area of ​​the wound surface using bioimpedance technology. The present invention proposes a method for dynamically monitoring wound healing area based on bioimpedance technology, and designs and constructs a miniature portable impedance monitoring system for non-invasive quantitative monitoring of wound healing area. It has important clinical application prospects and economic value for portable real-time dynamic monitoring of the healing status of open wounds and non-invasive quantitative and accurate evaluation. Summary of the invention

[0004] The purpose of the present invention is to propose and construct a method and system for dynamically monitoring wound healing area using bioimpedance technology. Based on the principle of bioimpedance, a mathematical model describing the quantitative relationship between skin surface impedance and wound area is established, and a method for determining the wound area by detecting skin surface impedance signals is obtained using the established mathematical model; it is beneficial to design and construct a miniaturized, portable bioimpedance detection system based on single-chip microcomputer and automatic control principles, so that it can be applied to non-invasive quantitative monitoring and evaluation of wound healing area.

[0005] The technical solution of the present invention is as follows:

[0006] A method for dynamically monitoring wound healing area using bioimpedance technology requires the establishment of a mathematical model that describes the quantitative relationship between skin surface impedance and wound area. The specific method is as follows:

[0007] Skin surface electrical impedance Electrode impedance , electrode contact impedance between electrode and skin , Skin epidermal impedance , dermis and subcutaneous tissue impedance Therefore, the skin surface electrical impedance satisfies:

[0008] (1)

[0009] Electrode impedance : Since the electrode is composed of a metal wire with good conductivity and a metal electrode sheet, it exhibits pure resistance, therefore:

[0010] (2)

[0011] Electrode contact impedance between electrode and skin :In addition to the resistive In addition, the electrodes and the skin are difficult to fit tightly due to the presence of air and sweat, so there is also capacitive , so the electrode contact impedance between the electrode and the skin is expressed as:

[0012] (3)

[0013] Skin epidermal impedance :In addition to the resistive In addition, the epidermis contains a stratum corneum, which has extremely poor conductivity and is equivalent to a dielectric. Under the epidermis is the dermis and subcutaneous tissue, which contain a large number of blood vessels and have better conductivity. Therefore, a layer of epidermis with extremely poor conductivity is sandwiched between the dermis with better conductivity and the electrode sheet. This structure is equivalent to a capacitor, so it also has capacitance. , so the skin epidermis impedance is expressed as:

[0014] (4)

[0015] Dermis and subcutaneous tissue impedance Size: This part has good conductivity, so it behaves as pure resistance. :

[0016] (5)

[0017] Therefore, the skin surface impedance model is equivalent to a series-parallel circuit composed of resistors and capacitors (such as Figure 1 ). According to circuit theory, the skin surface impedance consists of its real part and imaginary part:

[0018] (6)

[0019] The real part :

[0020] (7)

[0021] Imaginary part :

[0022] (8)

[0023] The amplitude and Phase for:

[0024] (9)

[0025] (10)

[0026] in, represents the imaginary unit, Indicates the measured angular frequency.

[0027] From formulas (1)-(10), we know that the skin surface impedance is Electrode impedance , electrode contact impedance between electrode and skin In addition, the resistance of biological tissue , , and capacitive , Determine, based on the principle of circuit and biological similarity, the resistance of biological tissue Capacitance It is expressed as:

[0028] (11)

[0029] (12)

[0030] in and are the electrical resistivity and dielectric constant of biological tissue, and It is a geometric parameter related to the area and depth of the wound surface. Therefore, the change in wound geometry during wound healing will change the resistance of biological tissue. Capacitance , which in turn affects the impedance of the skin epidermis , dermis and subcutaneous tissue impedance , which eventually causes the skin surface electrical impedance Therefore, by combining the above numerical model of skin surface impedance and wound area, the wound area can be quantitatively analyzed and evaluated by measuring the change of wound skin surface impedance.

[0031] A system for dynamically monitoring wound healing area using bioelectrical impedance technology comprises a control and interaction module I, an excitation signal loading module II and an impedance signal acquisition and processing module III.

[0032] The control and interaction module I includes: a parameter setting and data display unit A-1, a Bluetooth communication unit A-2, a main controller A-3, and a power supply unit A-4. The parameter setting and data display unit A-1 is connected to the main controller A-3 through the Bluetooth communication unit A-2 to transmit the preset parameters of the detection process, and to transmit data back in real time and display it in real time. The power supply unit A-4 is connected to the main controller A-3 to supply power to the subsequent working modules;

[0033] The excitation signal loading module II includes: a high-precision voltage source A-5, an excitation signal generating unit A-6, and an analog-to-digital conversion unit A-7. When the main controller A-3 sends a work instruction to the high-precision voltage source A-5 and the excitation signal generating unit A-6 through the serial communication line, the excitation signal generating unit A-6 generates an excitation signal and converts it into an excitation voltage signal through the analog-to-digital conversion unit A-7. At this time, the analog-to-digital conversion unit A-7 compares and corrects the excitation voltage signal with the excitation voltage generated by the high-precision voltage source A-5. When the error is less than 1%, it will be output and act on the wound tissue through the first excitation electrode A-8-1 and the second excitation electrode A-8-4;

[0034] The impedance signal acquisition and processing module III includes: a signal acquisition and processing unit A-9, a high-precision current source A-10, an impedance data calculation and storage unit A-11, and an SPI communication interface A-12. When the main controller A-3 sends a work instruction to the signal acquisition and processing unit A-9 and the high-precision current source A-10 through the serial communication line, the signal acquisition and processing unit A-9 acquires the current signal generated by the wound tissue due to the application of the excitation voltage in real time through the second measuring electrode A-8-2 and the third measuring electrode A-8-3, and then the signal acquisition and processing unit A-9 calculates the acquired current signal based on the current signal generated by the high-precision current source A-10. Real-time calibration is performed to suppress zero-point drift, control the signal error below 1%, and ensure accurate signal acquisition; the calibrated current signal will be transmitted to the impedance data calculation and storage unit A-11 through a wire. The impedance data calculation and storage unit A-11 will calculate the real-time skin surface electrical impedance value of the wound tissue being measured based on the obtained current signal and the real-time applied excitation voltage signal output by the analog-to-digital conversion unit A-7, and store it; at the same time, the data will be transmitted to the main controller A-3 in real time through the SPI communication interface A-12, and transmitted to the parameter setting and data display unit A-1 through the Bluetooth communication unit A-2, thereby realizing real-time display of data.

[0035] Furthermore, the contrast correction output of the excitation voltage, the real-time correction of the collected current signal, and the double-calibration signal generation and collection design were designed to improve the detection accuracy of the bioelectrical impedance signal.

[0036] Furthermore, bioimpedance measurement technology is used to quantitatively evaluate the wound area. By the change of impedance value, the corresponding change of wound area can be judged, thus achieving quantitative and accurate evaluation of the wound healing process.

[0037] Furthermore, a non-contact and non-invasive wound healing assessment is achieved.

[0038] Furthermore, real-time monitoring of wound healing can be achieved, and the monitoring time can be selected as required.

[0039] Furthermore, an electrical signal of 0.5-2.4V AC signal, 0-200KHz is used.

[0040] Compared with the prior art, the advantages of the present invention are:

[0041] (1) A mathematical model of skin surface impedance and wound area was proposed, which enabled quantitative assessment of wound area by detecting changes in impedance values.

[0042] (2) A bioimpedance acquisition system for dynamic monitoring of wound area was proposed, which achieved quantitative monitoring of wound healing status. Different from the clinical visual inspection method, it provided a new evaluation device. It achieved non-contact, non-invasive and non-invasive detection, avoided the possibility of secondary infection, reduced patient pain and alleviated the pressure on medical resources. It achieved real-time and uninterrupted monitoring and optimized clinical treatment effects. It realized a dual-calibration impedance acquisition device to improve measurement accuracy.

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Model diagram of skin surface impedance and wound area.

[0045] Figure 2 System block diagram of the bioimpedance detection device.

[0046] Figure 3 Flow chart for using the bioimpedance detection device.

[0047] Figure 4 Figure 2. Results of biological tissue wound experiment.

[0048] In the figure: I control and interaction module, II excitation signal loading module, III impedance signal acquisition and processing module, A-1 parameter setting and data display unit, A-2 Bluetooth communication unit, A-3 main controller, A-4 power supply unit, A-5 high-precision voltage source, A-6 excitation signal generating unit, A-7 analog-to-digital conversion unit, A-8 electrode, A-9 signal acquisition and processing unit, A-10 high-precision current source, A-11 impedance data calculation and storage unit, A-12 SPI communication interface. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0050] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0051] The specific settings are based on actual construction requirements and are not specifically limited in this application.

[0052] like Figures 1 to 4As shown, a method and system for dynamically monitoring wound healing area using bioelectrical impedance technology includes a device control and interaction module I, an excitation signal loading module II, and an impedance signal acquisition and processing module III. The device control and human-computer interaction module I includes: a parameter setting and data display unit A-1, a Bluetooth communication unit A-2, a main control unit A-3, and a power supply unit A-4; the excitation signal loading module II includes: a high-precision voltage source A-5, an excitation signal generating unit A-6, and an analog-to-digital conversion unit A-7; the impedance signal acquisition and processing module III includes: a signal acquisition and processing unit A-9, a high-precision current source A-10, an impedance data calculation and storage unit A-11, and an SPI communication interface A-12; and finally, there is an electrode A-8. Before starting the test, place the device according to Figure 3 way to connect.

[0053] The wound healing measurement process is as follows: the parameter setting and data display unit A-1 is connected to the main controller A-3 through the Bluetooth communication unit A-2, which is used to transmit the preset parameters of the detection process, and to transmit data back in real time and display it in real time. The power supply unit A-4 is connected to the main controller A-3 to power the subsequent working modules; when the main controller A-3 sends a working instruction to the high-precision voltage source A-5 and the excitation signal generating unit A-6 through the serial communication line, the excitation signal generating unit A-6 generates an excitation signal and converts it into an excitation voltage signal through the analog-to-digital conversion unit A-7. At this time, the analog-to-digital conversion unit A-7 will compare and correct this excitation voltage signal with the excitation voltage generated by the high-precision voltage source A-5. When the error is less than 1%, it will be output and act on the wound tissue through the first excitation electrode A-8-1 and the second excitation electrode A-8-4; when the main controller A-3 sends a working instruction to the signal acquisition and processing unit A-9 and the high-precision current source A-10 through the serial communication line, the excitation signal generating unit A-6 generates an excitation signal and converts it into an excitation voltage signal through the analog-to-digital conversion unit A-7. At this time, the analog-to-digital conversion unit A-7 will compare and correct this excitation voltage signal with the excitation voltage generated by the high-precision voltage source A-5. When the error is less than 1%, it will be output and act on the wound tissue through the first excitation electrode A-8-1 and the second excitation electrode A-8-4. Instructions, the signal acquisition and processing unit A-9 collects the current signal generated by the wound tissue due to the application of the excitation voltage in real time through the second measuring electrode A-8-2 and the third measuring electrode A-8-3, and then the signal acquisition and processing unit A-9 calibrates the collected current signal in real time based on the current signal generated by the high-precision current source A-10, suppresses the zero drift phenomenon, and controls the signal error to less than 1%, thereby ensuring the accurate acquisition of the signal; the calibrated current signal will be transmitted to the impedance data calculation and storage unit A-11 through a wire, and the impedance data calculation and storage unit A-11 will calculate the real-time skin surface electrical impedance value of the measured wound tissue based on the obtained current signal and the real-time applied excitation voltage signal output by the analog-to-digital conversion unit A-7, and store it; at the same time, the data will be transmitted to the main controller A-3 in real time through the SPI communication interface A-12, and transmitted to the parameter setting and data display unit A-1 through the Bluetooth communication unit A-2, thereby realizing real-time display of the data.

[0054] After the device was built, the biological tissue wound impedance experiment was carried out using the device to verify the feasibility of the method. The results are shown in the figure below. Figure 4 shown.

[0055] Further, the whole set of electroporation experiments is performed as follows:

[0056] Step 1: Pretreatment: clean both sides of the wound.

[0057] Step 2: Divide the electrode A-8 into an excitation group and a measurement group. The excitation group includes the first excitation electrode A-8-1 and the second excitation electrode A-8-2. The measurement group includes the third measurement electrode A-8-3 and the fourth measurement electrode A-8-4. The two electrodes of the excitation group and the two electrodes of the measurement group are respectively attached to both sides of the wound, and the electrode A-8 of the excitation group and the electrode A-8 of the measurement group are respectively connected to the excitation signal loading module II and the impedance signal acquisition and processing module III.

[0058] Step 3: Turn on the power supply unit A-4 and select the appropriate channel and baud rate in the parameter setting and data display unit A-1.

[0059] Step 4: Press the switch on the main controller A-3, the excitation signal loading module II starts to work, and starts to apply 0.5V-2.4V AC signal output through the electrode A-8 of the excitation group. At the same time, the impedance signal acquisition and processing module III starts to work, and collects current signals in real time through the acquisition electrodes, and transmits the impedance data to the main controller A-3 after processing.

[0060] Step 5: The main controller A-3 transmits the data to the parameter setting and data display unit A-1 through the Bluetooth communication unit A-2, and displays the impedance data change graph on the screen in real time.

[0061] Step 6: When the measurement effect is achieved, remove the electrode A-8 and the measurement is finished.

[0062] Based on the above technical solution, the system was also used to conduct an in vitro tissue wound experiment to verify the feasibility of the method. The experimental results are as follows Figure 4 shown.

Claims

1. A method for dynamically monitoring wound healing area using bioelectrical impedance technology, characterized in that: It is necessary to establish a mathematical model to describe the quantitative relationship between skin surface electrical impedance and wound area. The specific method is as follows: Skin surface electrical impedance Electrode impedance , electrode contact impedance between electrode and skin , Skin epidermal impedance , dermis and subcutaneous tissue impedance Therefore, the skin surface electrical impedance satisfies: (1) Electrode impedance :Performs pure resistance: (2) Electrode contact impedance between electrode and skin :In addition to the resistive In addition, it also has capacitive , so the electrode contact impedance between the electrode and the skin is expressed as: (3) Skin epidermal impedance :In addition to the resistive In addition, it also has capacitive , so the skin epidermis impedance is expressed as: (4) Dermis and subcutaneous tissue impedance :Performs pure resistance : (5) Therefore, the skin surface impedance model is equivalent to a series-parallel circuit composed of resistors and capacitors; according to circuit theory, the skin surface impedance consists of its real part and imaginary part: (6) The real part : (7) Imaginary part : (8) The amplitude and Phase for: (9) (10) in, represents the imaginary unit, Indicates the measured angular frequency; From formulas (1)-(10), we know that the skin surface impedance is Electrode impedance , electrode contact impedance between electrode and skin In addition, the resistance of biological tissue , , and capacitive , Determine, based on the principle of circuit and biological similarity, the resistance of biological tissue Capacitance Expressed as （11） （12） in and are the electrical resistivity and dielectric constant of biological tissue, and It is a geometric parameter related to the area and depth of the wound surface; therefore, the change in wound geometry produced during the wound healing process will change the resistance of biological tissues. Capacitance , which in turn affects the impedance of the skin epidermis , dermis and subcutaneous tissue impedance , which eventually causes the skin surface electrical impedance Changes; therefore, combined with the above numerical model of skin surface impedance and wound area, the wound area can be quantitatively analyzed and evaluated by measuring the changes in wound skin surface impedance.

2. A system for dynamically monitoring wound healing area using bioelectrical impedance technology, characterized in that: It includes a control and interaction module (I), an excitation signal loading module (II) and an impedance signal acquisition and processing module (III); The control and interaction module (I) comprises: a parameter setting and data display unit (A-1), a Bluetooth communication unit (A-2), a main controller (A-3), and a power supply unit (A-4). The parameter setting and data display unit (A-1) is connected to the main controller (A-3) via the Bluetooth communication unit (A-2) to transmit preset parameters of the detection process, and to transmit data back in real time and display it in real time. The power supply unit (A-4) is connected to the main controller (A-3) to supply power to subsequent working modules. The excitation signal loading module (II) includes: a high-precision voltage source (A-5), an excitation signal generating unit (A-6), and an analog-to-digital conversion unit (A-7). When the main controller (A-3) sends a working instruction to the high-precision voltage source (A-5) and the excitation signal generating unit (A-6) through the serial communication line, the excitation signal generating unit (A-6) generates an excitation signal and converts it into an excitation voltage signal through the analog-to-digital conversion unit (A-7). At this time, the analog-to-digital conversion unit (A-7) compares and corrects the excitation voltage signal with the excitation voltage generated by the high-precision voltage source (A-5). When the error is less than 1%, it will be output and act on the wound tissue through the first excitation electrode (A-8-1) and the second excitation electrode (A-8-4); The impedance signal acquisition and processing module (III) includes: a signal acquisition and processing unit (A-9), a high-precision current source (A-10), an impedance data calculation and storage unit (A-11), and an SPI communication interface (A-12). When the main controller (A-3) sends a work instruction to the signal acquisition and processing unit (A-9) and the high-precision current source (A-10) through the serial communication line, the signal acquisition and processing unit (A-9) acquires the current signal generated by the wound tissue due to the application of the excitation voltage in real time through the second measuring electrode (A-8-2) and the third measuring electrode (A-8-3), and then the signal acquisition and processing unit (A-9) calculates the current signal based on the current signal generated by the high-precision current source (A-10). The collected current signal is calibrated in real time by the flow signal to suppress the zero drift phenomenon and control the signal error below 1%. The calibrated current signal is transmitted to the impedance data calculation and storage unit (A-11) through the wire. The impedance data calculation and storage unit (A-11) calculates the real-time skin surface electrical impedance value of the wound tissue under test based on the obtained current signal and the real-time applied excitation voltage signal output by the analog-to-digital conversion unit (A-7), and stores it. At the same time, the data is transmitted to the main controller (A-3) in real time through the SPI communication interface (A-12), and is transmitted to the parameter setting and data display unit (A-1) through the Bluetooth communication unit (A-2), thereby realizing real-time display of the data.

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