Blood oxygen signal dynamic analysis method based on timer and cycle extreme value analysis

Abstract

The invention discloses a blood oxygen signal dynamic analysis method based on a timer and cycle extreme value analysis. The method comprises the steps that S1, the frequency of the timer in a basic microcontroller is set to be the same as the sampling frequency of a blood oxygen sensor; s2, collecting a blood oxygen signal based on a blood oxygen sensor; s3, a blood oxygen signal is obtained from the blood oxygen sensor through the basic microcontroller, whether the obtained blood oxygen signal is accurate or not is judged according to a set verification rule, if yes, the step S4 is executed, and if not, an error reporting program is executed; s4, updating the alternating current component and the direct current component in real time based on a user-defined period extreme value analysis method; and obtaining a continuous blood oxygen detection result based on the alternating current component and the direct current component which are updated in real time. According to the invention, blood oxygen calculation is realized on the basis of the basic microcontroller, the stability and the anti-interference capability of the basic microcontroller on blood oxygen measurement are improved, blood oxygen measurement equipment has a price advantage, popularization and promotion of products are facilitated, and development of the technology in the field of blood oxygen measurement is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical signal detection, and in particular to a dynamic analysis method for blood oxygen signals based on a timer and periodic maximum and minimum value analysis. Background Art

[0002] Blood oxygen saturation is an important physiological parameter reflecting the oxygen content in human blood. Accurate and rapid acquisition of blood oxygen signals is of great significance for disease diagnosis and health monitoring. Currently, the hardware design scheme for detecting blood oxygen saturation usually combines two light-emitting diodes and a photodetector, and a fixed signal processing circuit is used to send the blood oxygen signal to a microcontroller for processing. To achieve a certain degree of filtering and data stability, common processing algorithms for blood oxygen signals in the microcontroller include the fast Fourier algorithm, the adaptive wavelet transform algorithm, the Kalman filter algorithm, etc. These algorithms have a high computational complexity and require high computing power from the microcontroller. For example, the microcontroller needs to have floating-point operation or fixed-point operation support to achieve high-complexity blood oxygen signal filtering to reach a certain stability, resulting in a high computational cost and being not conducive to wide application. Summary of the Invention

[0003] The present invention provides a dynamic analysis method for blood oxygen signals based on a timer and periodic maximum and minimum value analysis to overcome the technical problem that when processing blood oxygen signals in the prior art, due to the high computational complexity of the algorithms used and the high requirements for the microcontroller, the computational cost is high and it is not conducive to wide application.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A dynamic analysis method for blood oxygen signals based on a timer and periodic maximum and minimum value analysis, the specific steps include:

[0006] S1: Set the frequency of the timer in the basic microcontroller to be the same as the sampling frequency of the blood oxygen sensor;

[0007] S2: Collect blood oxygen signals based on the blood oxygen sensor, and the blood oxygen signals include red light and infrared light signals;

[0008] S3: Obtain the blood oxygen signal from the blood oxygen sensor through the basic microcontroller, and judge whether the obtained blood oxygen signal is accurate according to the set verification rule. If it is accurate, execute S4; otherwise, execute the error reporting program;

[0009] S4: Design a custom periodic maximum and minimum value analysis method based on the basic microcontroller, and update the AC component and DC component in the blood oxygen signal acquisition process in real time based on the custom periodic maximum and minimum value analysis method; obtain continuous blood oxygen detection results based on the AC component and DC component updated in real time.

[0010] Furthermore, based on the custom cycle maximum and minimum value analysis method, the AC component and DC component in the blood oxygen signal acquisition process are updated in real time; the specific steps for obtaining continuous blood oxygen detection results based on the AC component and DC component updated in real time include:

[0011] S41: Set a custom blood oxygen signal acquisition cycle, and acquire the blood oxygen signal according to the custom blood oxygen signal acquisition cycle to obtain the blood oxygen signals of the continuous first custom cycle, second custom cycle,..., Nth custom cycle;

[0012] S42: Obtain the maximum value and minimum value of the blood oxygen signal in the first custom cycle, and calculate the AC component AC and DC component DC of the blood oxygen signal based on the maximum value and minimum value of the blood oxygen signal in the first custom cycle;

[0013] S43: Calculate the blood oxygen ratio and blood oxygen saturation of the first custom cycle based on the AC component AC and DC component DC of the blood oxygen signal;

[0014] S44: Switch to the next custom cycle, and obtain the maximum value and minimum value of the blood oxygen signal in the next custom cycle, and calculate the AC component AC and DC component DC of the blood oxygen signal based on the maximum value and minimum value of the blood oxygen signal in the next custom cycle;

[0015] S45: Calculate the blood oxygen ratio and blood oxygen saturation of this custom cycle based on the AC component AC and DC component DC of the blood oxygen signal in the next custom cycle;

[0016] S46: Repeat S44 - S45 until the blood oxygen ratio and blood oxygen saturation of the Nth custom cycle are obtained.

[0017] Furthermore, the formulas for calculating the AC component AC and DC component DC of the blood oxygen signal based on the maximum value and minimum value of the blood oxygen signal in the custom cycle include:

[0018] Calculate the AC components AC Red and AC Ir of the red light signal and infrared light signal in the blood oxygen signal respectively, and use AC Red and AC Ir as the pulsating components, expressed as:

[0019] AC Red = Max Red - Min Red

[0020] AC Ir = Max Ir - Min Ir

[0021] Obtain the DC components of the red light signal and the infrared light signal in the blood oxygen signal respectively Red and DC Ir ,and use DC red and DC Ir as the baseline, expressed as:

[0022] DC Red =Min Red

[0023] DC ir =Min Ir

[0024] In the formula, Max Red is the peak value of the red light signal; Min Red is the trough value of the red light signal; Max Ir is the peak value of the infrared light signal; min Ir is the trough value of the infrared light signal.

[0025] Furthermore, the calculation formulas for the blood oxygen ratio R with a custom period and the blood oxygen saturation SpO2 calculated based on the AC component and the DC component are respectively:

[0026]

[0027] SpO2=A*R 2 +B*R+C (2)

[0028] Among them, A, B, and C are all set calibration coefficients.

[0029] Furthermore, the basic microcontroller includes but is not limited to the 51 series microcontrollers and the STM32F10x series microcontrollers.

[0030] Furthermore, the set verification rules include:

[0031] Judge whether the sum of the intensities of the red light and the infrared light signals is less than or equal to the threshold. If it is less than or equal to, it means that the user has not accurately placed the finger on the sensor, indicating that the obtained blood oxygen signal is inaccurate. If it is greater, it means that the obtained blood oxygen signal is accurate.

[0032] Beneficial effects: In the present invention, the frequency of the timer in the basic microcontroller is set to be the same as the sampling frequency of the blood oxygen sensor to ensure the real-time effectiveness of data. At the same time, a custom cycle maximum and minimum analysis method is designed based on the basic microcontroller. Based on the custom cycle maximum and minimum analysis method, the AC component and DC component in the blood oxygen signal acquisition process are updated in real time. The custom cycle maximum and minimum analysis method can offset baseline drift and replace the traditional high-complexity blood oxygen filtering algorithm for dynamically monitoring blood oxygen. A continuous blood oxygen detection result is obtained based on the AC component and DC component updated in real time. The present invention is committed to implementing blood oxygen calculation on a basic microcontroller, improving the stability and anti-interference ability of blood oxygen measurement based on the basic microcontroller. Compared with other high-performance floating-point microcontrollers, it has a certain price advantage, reducing the hardware cost of blood oxygen acquisition equipment, making the blood oxygen measurement equipment more price-competitive, facilitating the popularization and promotion of products, and promoting the development of technologies in the field of blood oxygen measurement. Description of the Drawings

[0033] In order 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 the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a flowchart of a dynamic analysis method for blood oxygen signals based on a timer and cycle maximum and minimum analysis in the present invention;

[0035] Figure 2 It is a timer flowchart for detecting the blood oxygen result in the embodiment of the present invention;

[0036] Figure 3 It is a main flowchart for detecting the blood oxygen result in the embodiment of the present invention;

[0037] Figure 4 It is a structural diagram of a blood oxygen signal analysis system in the embodiment of the present invention;

[0038] Figure 5 It is a threshold simulation result diagram of red light and infrared light signals during the blood oxygen signal acquisition process in the embodiment of the present invention;

[0039] Figure 6 It is a SpO2 stability test result diagram in the embodiment of the present invention;

[0040] Figure 7 It is a comparison result diagram of predicted values and true values in the embodiment of the present invention. Detailed Embodiments

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] This embodiment provides a dynamic analysis method for blood oxygen signals based on a timer and periodic maximum and minimum value analysis. As Figures 1 to 3 shown, in order to achieve a certain stable and fast dynamic acquisition effect on a simple, basic microcontroller, the specific steps include:

[0043] S1: Set the frequency of the timer in the basic microcontroller to be the same as the sampling frequency of the blood oxygen sensor;

[0044] Specifically, in this embodiment, precise signal acquisition is achieved by using the timer of the basic microcontroller. The frequency of the timer is set to be equal to the sampling frequency of the blood oxygen sensor to ensure that the working rhythms of the timer and the blood oxygen sensor are completely consistent, avoiding data omission or repeated acquisition caused by frequency differences, ensuring the integrity and accuracy of the acquired blood oxygen signal data, and providing a reliable basis for subsequent analysis. At the same time, in the interrupt service function of the timer, start the function of reading the blood oxygen signal collected by the blood oxygen sensor;

[0045] S2: Collect blood oxygen signals based on the blood oxygen sensor, where the blood oxygen signals include red light and infrared light signals;

[0046] S3: Obtain the blood oxygen signal from the blood oxygen sensor through the basic microcontroller, and determine whether the obtained blood oxygen signal is accurate according to the set verification rules. If it is accurate, execute S4; otherwise, execute the error reporting program;

[0047] S4: Design a custom periodic maximum and minimum value analysis method based on the basic microcontroller, and update the AC component and DC component in the blood oxygen signal acquisition process in real time based on the custom periodic maximum and minimum value analysis method; obtain continuous blood oxygen detection results based on the AC component and DC component updated in real time.

[0048] In a specific embodiment, the specific steps of updating the AC component and DC component in the blood oxygen signal acquisition process in real time based on the custom periodic maximum and minimum value analysis method and obtaining continuous blood oxygen detection results based on the AC component and DC component updated in real time include:

[0049] S41: Set a custom blood oxygen signal acquisition period, and acquire blood oxygen signals according to the custom blood oxygen signal acquisition period to obtain continuous blood oxygen signals for the first custom period, the second custom period, …, the Nth custom period;

[0050] S42: Obtain the maximum value and minimum value of the blood oxygen signal in the first custom period, and calculate the alternating current component AC and direct current component DC of the blood oxygen signal based on the maximum value and minimum value of the blood oxygen signal in the first custom period;

[0051] Specifically, in this embodiment, the first red light Fifo Red and infrared light Fifo Ir signal values in the blood oxygen signal of the first custom period are used as the initial values for maximum and minimum value comparison, and the maximum value (peak value Max Red ) and minimum value (valley value Min Red ) of the red light signal, the maximum value (peak value Max Ir ) and minimum value (valley value Min Ir ) of the infrared light signal in the current custom period are recorded in real time through subsequent comparisons to perform dynamic maximum and minimum value updates. By designing a custom period maximum and minimum value analysis method in this embodiment, the calculation amount is reduced, the calculation efficiency is improved while maintaining the accuracy, and the dynamic monitoring requirements are met.

[0052] Specifically, as Figure 3 shown, after the acquisition of each custom period is completed, the data ready flag bit is set. When the main program of the basic microcontroller recognizes the data ready flag bit, the blood oxygen result of this custom period is calculated in real time.

[0053] S43: Calculate the blood oxygen ratio and blood oxygen saturation of the first custom period based on the alternating current component AC and direct current component DC of the blood oxygen signal;

[0054] S44: Switch to the next custom period, and obtain the maximum value and minimum value of the blood oxygen signal in the next custom period, and calculate the alternating current component AC and direct current component DC of the blood oxygen signal based on the maximum value and minimum value of the blood oxygen signal in the next custom period;

[0055] S45: Calculate the blood oxygen ratio and blood oxygen saturation of this custom period based on the alternating current component AC and direct current component DC of the blood oxygen signal in the next custom period;

[0056] S46: Repeat S44 - S45 until the blood oxygen ratio and blood oxygen saturation of the Nth custom period are obtained.

[0057] In a specific embodiment, the formulas for calculating the AC (alternating current component) and DC (direct current component) of the blood oxygen signal based on the maximum and minimum values of the blood oxygen signal in a custom period include:

[0058] Calculate the AC of the red light signal and the infrared light signal in the blood oxygen signal respectively Red and AC Ir , and use AC Red and AC Ir as the pulsating component, expressed as:

[0059] AC Red = Max Red - Min Red

[0060] AC Ir = Max Ir - Min Ir

[0061] Obtain the DC of the red light signal and the infrared light signal in the blood oxygen signal respectively Red and DC Ir , and use DC Red and DC Ir as the baseline, expressed as:

[0062] DC Red = Min Red

[0063] DC Ir = Min Ir

[0064] In the formula, Max Red is the peak value of the red light signal; Min Red is the trough value of the red light signal; Max Ir is the peak value of the infrared light signal; Min Ir is the trough value of the infrared light signal.

[0065] Specifically, since the DC component (baseline) reflects the absorption of light by static blood in blood vessels, which is mainly determined by the static component and corresponds to the baseline level of the blood oxygen signal, and the baseline is easily affected by external environmental or self-movement-generated pseudo signals such as breathing and emotions, causing the blood oxygen signal to deviate from the normal range. Therefore, in this embodiment, by dynamically tracking and continuously updating the DC component in real time, the real signal and the interference signal can be dynamically distinguished, avoiding misjudging the interfered baseline as a "new static level" during the blood oxygen signal acquisition process, better identifying and removing the interference signal, improving the signal quality and the stability of the measurement. At the same time, the AC component directly corresponds to the periodic fluctuation of the arterial blood volume (which is the principle of blood oxygen acquisition). Cooperating with the real-time updated DC component can maximize the extraction of the pulsating component, ensuring that the calculation of key parameters such as the blood oxygen ratio is based on the latest signal characteristics, thereby improving the measurement accuracy.

[0066] In a specific embodiment, the calculation formulas for the blood oxygen ratio R and the blood oxygen saturation SpO2 with a custom period calculated based on the AC component and the DC component are respectively:

[0067]

[0068] SpO2 = A * R 2 + B * R + C (2)

[0069] Wherein, A, B, and C are all set calibration coefficients. In this embodiment, preferably, A, B, and C are set as:

[0070] SpO2 = -45.06 * R 2 + 30.35 * R + 94.84 (3)

[0071] In a specific embodiment, the basic microcontroller includes but is not limited to the 51 series microcontrollers and the STM32F10x series microcontrollers.

[0072] Specifically, the method proposed in this embodiment is applied to fingertip blood oxygen measurement. The set verification rules include: determining whether the sum of the intensities of the red light and infrared light signals is less than or equal to a threshold. If it is less than or equal to, it means that the user has not accurately placed the finger on the blood oxygen sensor, indicating that the obtained blood oxygen signal is inaccurate. If it is greater, it means that the obtained blood oxygen signal is accurate. Specifically, as Figure 5 shown, the user starts to place the finger at point A. Since the transmissive blood oxygen sensor collects the reflected signal, the light value increases significantly. When it is greater than the set threshold, sampling is started and blood oxygen calculation is performed. If the threshold is not reached, an alarm prompt needs to be given in a timely manner through the display device or the communication device to avoid performing invalid calculations when not worn correctly.

[0073] Specifically, in this embodiment, the MDK Keil development tool is used for code writing and debugging in the software environment, and Matlab is used for data simulation.

[0074] Specifically, the hardware design of the operating environment of the method proposed in this embodiment is as Figure 4 shown. A lithium battery is used to power the entire blood oxygen signal analysis system. After passing through a level conversion circuit, it provides appropriate levels for different parts of the blood oxygen signal analysis system. A basic microcontroller is used as the core processing unit of the blood oxygen signal analysis system. The basic microcontroller has the characteristics of low cost and low power consumption, and can meet the communication requirements of blood oxygen signal acquisition. At the same time, a blood oxygen sensor with high precision and high sensitivity is used, which can effectively collect the photoplethysmogram signal of the human body. The blood oxygen sensor integrates a blood oxygen measurement chip for measuring fingertip blood oxygen. The blood oxygen sensor can convert the photoplethysmogram signal of the human body into an electrical signal, and the blood oxygen measurement chip internally performs amplification and filtering processing through an analog front-end circuit and transmits the blood oxygen digital signal. The basic microcontroller and the blood oxygen sensor are connected through IIC to realize the acquisition and transmission of blood oxygen signals. The blood oxygen signal analysis system is not limited to the above parts, but also includes an expandable part, and the communication part can be freely selected to transmit the blood oxygen signal to the server to realize functions such as remote display, AI analysis, and early warning.

[0075] In the specific implementation process, the peripherals of the basic microcontroller are initialized, including the system clock, IIC function, timer, etc. The custom blood oxygen signal acquisition period is set, that is, the acquisition frequency of the blood oxygen sensor is 100 SPS, and the timer update frequency is set to 100 HZ to ensure the synchronization of data acquisition, that is, to ensure that 100 digital red light and infrared light values are collected per second respectively. Through IIC communication, the basic microcontroller reads the red light Fifo Red , infrared light Fifo Ir raw signal values in the fixed address of the blood oxygen sensor in real time.

[0076] To verify the effectiveness of the method proposed in this embodiment, corresponding stability tests and accuracy evaluations are carried out: Figure 6 As the test result of blood oxygen saturation, under the condition of continuously collecting blood oxygen saturation at a frequency of 1 Hz, during the dynamic monitoring process, the blood oxygen data output by the method proposed in this embodiment is recorded, and the standard deviation and coefficient of variation of the data are calculated to evaluate the stability of the method proposed in this embodiment for dynamically monitoring blood oxygen saturation. As Figure 6 shown, the SpO2 value fluctuates within a certain range, the standard deviation is 0.28, and the coefficient of variation is 0.28%. The standard deviation reflects the degree of deviation of the data from the mean value, and the coefficient of variation is the ratio of the standard deviation to the mean value. The smaller the two values, the smaller the fluctuation range of the SpO2 value around the mean value during the sampling process, the relatively concentrated measurement data, and the better the stability.

[0077] Accuracy assessment: Different healthy subjects were invited to be tested in a resting state, and professional medical equipment was used as the reference standard at the same time. Figure 7 It is a comparison chart of predicted values and true values. The measurement results of the two devices are compared and the error rate is calculated. As Figure 7 shown, the relative error is marked at each test point. The relative error reflects the deviation between the predicted value and the true value. Generally, the standard requirement for blood oxygen in a resting state is that the error ≤ ±2%. The maximum relative error during the measurement process using the method proposed in this embodiment is 1.7%, indicating that the measurement results have a certain degree of reliability and can provide an effective reference for judging the blood oxygen state in a conventional use scenario.

[0078] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A blood oxygen signal dynamic analysis method based on timer and cycle maximum value analysis, characterized in that: The specific steps include: S1: Set the frequency of the timer in the basic microcontroller to be the same as the sampling frequency of the blood oxygen sensor; S2: Collecting a blood oxygen signal based on the blood oxygen sensor, where the blood oxygen signal includes red light and infrared light signals; S3: obtaining a blood oxygen signal from the blood oxygen sensor through a basic microcontroller, and judging whether the obtained blood oxygen signal is accurate according to a set verification rule; if it is accurate, executing S4; otherwise, executing an error reporting procedure; S4: Design a custom periodic maximum value analysis method based on a basic microcontroller, and update the AC component and DC component in the blood oxygen signal acquisition process in real time based on the custom periodic maximum value analysis method; obtain continuous blood oxygen detection results based on the real-time updated AC component and DC component.

2. The blood oxygen measurement method based on timer and cycle maximum value analysis according to claim 1, characterized in that: Based on the self-defined periodic maximum value analysis method, the AC component and the DC component in the blood oxygen signal acquisition process are updated in real time; The specific steps of obtaining continuous blood oxygen detection results based on the real-time updated AC component and DC component include: S41: setting a custom blood oxygen signal acquisition cycle, and acquiring blood oxygen signals according to the custom blood oxygen signal acquisition cycle to obtain blood oxygen signals of a first custom cycle, a second custom cycle, ..., an Nth custom cycle in succession; S42: obtaining a maximum value and a minimum value of the blood oxygen signal in a first custom cycle, and calculating an alternating current component AC and a direct current component DC of the blood oxygen signal based on the maximum value and the minimum value of the blood oxygen signal in the first custom cycle; S43: Calculating the blood oxygen ratio and blood oxygen saturation of the first custom cycle based on the alternating current component AC and the direct current component DC of the blood oxygen signal; S44: Switching to the next custom cycle, and obtaining the maximum value and the minimum value of the blood oxygen signal in the next custom cycle, and calculating the alternating current component AC and the direct current component DC of the blood oxygen signal based on the maximum value and the minimum value of the blood oxygen signal in the next custom cycle; S45: Calculating the blood oxygen ratio and blood oxygen saturation of the next custom cycle based on the alternating current component AC and the direct current component DC of the blood oxygen signal of the next custom cycle; S46: Repeat S44-S45 until the blood oxygen ratio and blood oxygen saturation of the Nth custom cycle are obtained.

3. The blood oxygen measurement method based on timer and cycle maximum value analysis according to claim 2, characterized in that: The formulas for calculating the AC component and the DC component of the blood oxygen signal based on the maximum and minimum values ​​of the blood oxygen signal in the custom cycle include: Calculate the AC components of the red light signal and the infrared light signal in the blood oxygen signal respectively Red and AC Ir , and AC Red and AC Ir As a pulsating component, it is expressed as: AC Red =Max Red -Min Red AC Ir =Max Ir -Min Ir Get the DC component of the red light signal and the infrared light signal in the blood oxygen signal respectively Red and DC Ir , and DC Red and DC Ir As a baseline, this is expressed as: DC Red =My Red DC Ir =My Ir Where Max Red is the peak value of the red light signal; Min Red is the trough value of the red light signal; Max Ir is the peak value of the infrared light signal; Min Ir is the trough value of the infrared light signal.

4. The blood oxygen measurement method based on timer and cycle maximum value analysis according to claim 3 is characterized in that: The calculation formulas for the blood oxygen ratio R and blood oxygen saturation SpO2 of the custom cycle are calculated based on the AC component and the DC component: SpO2=A*R 2 +B*R+C (2) Among them, A, B, and C are all set calibration coefficients.

5. The blood oxygen measurement method based on timer and cycle maximum value analysis according to claim 4, characterized in that: The basic microcontroller includes but is not limited to 51 series microcontrollers and STM32F10x series microcontrollers.

6. The blood oxygen measurement method based on timer and cycle maximum value analysis according to claim 5, characterized in that: The validation rules that are set include: Determine whether the sum of the intensities of the red light and infrared light signals is less than or equal to a threshold. If so, it means that the user has not placed the finger on the sensor accurately, and the acquired blood oxygen signal is inaccurate. If greater than, it means that the acquired blood oxygen signal is accurate.

Images