Capillary refilling time detection method and device

Abstract

The invention discloses a capillary refilling time detection method and device, and relates to the field of microcirculation monitoring. The device comprises a diffusion correlation spectrum module, an automatic control module and a pressure modulation optical probe, the diffusion correlation spectrum module is used for sending near-infrared light to a finger area of a measured object, detecting scattered light spots of the measured area, calculating a light intensity autocorrelation function according to the scattered light spots to determine tissue blood flow of the measured area, and sending the tissue blood flow to the automatic control module. The tissue blood flow change of the detected part in the pressure change process of the optical probe is detected in real time in the whole process; the automatic control module is used for establishing an rBF-CRT model according to the real-time change of the tissue blood flow of the detected area, performing fitting calculation to determine the capillary refilling time, and controlling the interactive interface to display the real-time change condition of the tissue blood flow of the detected area and the capillary refilling time; and the pressure modulation optical probe is used for automatically controlling the pressure change between the optical probe and the finger part after receiving an instruction that the display interaction interface starts capillary refilling time measurement.

Description

Technical Field

[0001] The invention relates to the field of microcirculation monitoring and evaluation, and in particular to a capillary refill time detection method and device. Background Art

[0002] Capillary refill time (CRT) is the time required for the distal capillary bed to restore its original color after being compressed. It is the most direct observation index of blood flow to the distal capillaries. CRT is the most convenient and commonly used observation index for peripheral circulation monitoring.

[0003] Diffusion Correlation Spectroscopy (DCS) is an emerging near-infrared spectroscopy technology that can continuously, real-time and non-invasively obtain tissue blood flow change data. Diffusion correlation spectroscopy uses near-infrared spectrum to illuminate the tissue surface, and calculates the light intensity autocorrelation function of the scattered light spot on the tissue surface to infer the movement state of red blood cells in the tissue, thereby calculating and realizing quantitative detection of blood flow (rBF) changes in tissue microcirculation.

[0004] The present invention proposes for the first time to use diffusion correlation spectroscopy technology for the detection of capillary refill time (CRT). Diffusion correlation spectroscopy obtains the changes in blood flow in tissue microcirculation. Compared with the existing capillary refill time detection methods, diffusion correlation spectroscopy technology can more directly reflect the capillary refill time (CRT). In addition, the present invention automatically controls the pressure value adjustment between the optical probe and the finger through the changes in tissue blood flow for the first time, realizes the synchronous detection of tissue blood flow (rBF) and capillary refill time (CRT), and independently develops a capillary refill time detection device based on diffusion correlation spectroscopy technology. The present invention essentially solves the pain points of existing microcirculation assessments, and establishes an rBF-CRT model to fit and calculate the capillary refill time (CRT) based on the tissue blood flow change (rBF) signal. Summary of the invention

[0005] The purpose of the present invention is to provide a method and device for detecting capillary refill time, so as to realize accurate detection of capillary refill time by directly acquiring changes in tissue blood volume.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows.

[0007] In a first aspect, the present invention provides a method for detecting capillary refill time, the capillary refill time detection method comprising:

[0008] Place the finger of the object to be measured at the optical probe position;

[0009] Irradiate the finger of the object to be tested with a near-infrared light signal, receive the near-infrared scattered light spot signal after diffuse reflection, and detect the change of tissue blood flow in the finger of the object to be tested in real time based on the diffusion correlation spectroscopy technology;

[0010] The operator turns on the measurement of capillary refill time (CRT), and the automatic control realizes the adjustment of the pressure change between the optical probe and the finger part;

[0011] During the pressure change adjustment process, the changes in tissue blood flow (rBF) of the measured finger are detected in real time throughout the process;

[0012] Based on the real-time change data of tissue blood flow (rBF), the rBF-CRT model was established to fit and calculate the capillary refill time (CRT) and display it.

[0013] In a second aspect, the present invention provides a capillary refill time detection device, the capillary refill time detection device comprising: a diffusion-related spectroscopy module, an automatic control module and a pressure-modulated optical probe; the diffusion-related spectroscopy module and the pressure-modulated optical probe are both connected to the automatic control module; the diffusion-related spectroscopy module is connected to the pressure-modulated optical probe;

[0014] The diffusion correlation spectroscopy module is used to: send near-infrared light to the finger area of ​​the object to be measured, detect the scattered light spots in the measured area, calculate the light intensity autocorrelation function based on the scattered light spots to determine the tissue blood flow (rBF) in the measured area, and detect the changes in tissue blood flow in the measured part in real time during the pressure change of the optical probe.

[0015] The automatic control module is used to: establish an rBF-CRT model to fit and calculate the capillary refill time (CRT) according to the real-time changes in the tissue blood flow of the measured area, and display an interactive interface to show the real-time changes in the tissue blood flow (rBF) of the measured area and the capillary refill time (CRT);

[0016] The pressure modulated optical probe is used to transmit the near-infrared light emitted by the diffusion correlation spectroscopy module to the surface of the measured part, receive the scattered light spot after diffuse reflection and transmit it to the diffusion correlation spectroscopy module, and adjust the pressure change between the optical probe and the finger part according to the instructions of the automatic control module.

[0017] According to the specific embodiments provided by the present invention, this application discloses the following technical effects:

[0018] The present invention discloses a capillary refill time detection method and device, which relates to the field of microcirculation monitoring and evaluation. The detection method non-invasively obtains fingertip tissue blood flow changes (rBF) in real time based on diffusion correlation spectroscopy technology, and determines the capillary refill time (CRT) in real time based on tissue blood flow change signals. The device comprises a diffusion correlation spectroscopy module, an automatic control module and a pressure modulation optical probe. The diffusion correlation spectroscopy module is used to send near-infrared light to a finger region of a measured object, detect scattered light spots in the measured region, calculate the light intensity autocorrelation function according to the scattered light spots to determine the tissue blood flow (rBF) of the measured region, and detect the change of tissue blood flow of the measured part in real time during the pressure change of the optical probe. The automatic control module is used to establish an rBF-CRT model to fit and calculate the capillary refill time (CRT) according to the real-time change of tissue blood flow in the measured region, and control the interactive interface to display the real-time change of tissue blood flow (rBF) and capillary refill time (CRT) in the measured region. The pressure modulation optical probe is used to automatically control the pressure change between the optical probe and the finger region after receiving an instruction to start capillary refill time (CRT) measurement on the display interactive interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart of a capillary refill time detection method provided by one embodiment of the present invention;

[0021] Figure 2 A schematic structural diagram of a capillary refill time detection device provided by one embodiment of the present invention;

[0022] Figure 3 A schematic diagram of changes in tissue blood flow during the entire process of pressure modulation provided by an embodiment of the present invention.

[0023] Explanation of symbols: diffusion correlation spectroscopy module—1, automatic control module—block 2, pressure modulation optical probe—3. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] The present invention provides a capillary refill time detection method and device, aiming to solve the problem that capillary refill time detection in the field of microcirculation is subjective, inaccurate and unreal-time.

[0026] Based on this, the present invention provides a capillary refill time detection method and device. The detection method non-invasively obtains fingertip tissue blood flow changes (rBF) in real time based on diffusion correlation spectroscopy technology, and determines the capillary refill time (CRT) in real time according to the tissue blood flow change signal; the device includes a diffusion correlation spectroscopy module, an automatic control module and a pressure modulation optical probe, which can directly determine the capillary refill time based on the real-time acquired changes in the measured tissue blood flow.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] In an exemplary embodiment, Figure 1 As shown, a capillary refill time detection method is provided, comprising:

[0029] Step 1: Realize continuous real-time detection of blood flow in tissue of the measured part.

[0030] Specifically, the finger of the object to be measured is placed at the position of the optical probe; a near-infrared light signal is irradiated to the finger part to be measured, and a near-infrared scattered light spot signal after diffuse reflection is received, and the tissue blood flow change (rBF) of the finger part of the object to be measured is detected in real time based on the diffuse correlation spectroscopy technology;

[0031] Furthermore, the diffusion correlation spectroscopy technique detects the near-infrared scattered light spot signal and calculates the light intensity autocorrelation function to evaluate the movement state of red blood cells in the measured tissue, and obtains the real-time blood flow index (BFI) signal based on the light intensity autocorrelation function fitting calculation. The calculation formula of the light intensity autocorrelation function (g2(τ)) is:

[0032]

[0033] Where I(t) represents the light intensity detected at time t, τ is the delay time, and <> represents the time average.

[0034] Furthermore, based on the Siegert relationship, the normalized electric field autocorrelation function can be derived from the measured normalized light intensity autocorrelation function. The blood flow index BFI used to characterize the change of tissue blood flow is obtained by fitting the normalized electric field autocorrelation function and the solution of the related diffusion equation through a nonlinear minimization algorithm or a deep learning method, thereby obtaining the change of tissue blood flow rBF:

[0035]

[0036] Where BFI(t) represents the BFI at time t, <BFI(t b )> represents the average value of BFI in the initial stage over time, and rBF(t) represents the change value of tissue blood flow at time t. The initial stage is the stable stage after the measurement begins, and the default duration is 60s.

[0037] Step 2, start the measurement of capillary refill time, detect the changes of tissue blood flow in the measured finger in real time throughout the whole process, and store the tissue blood flow data in the automatic control module for backup.

[0038] Specifically, the measurement of capillary refill time is mainly divided into three steps.

[0039] Step (1) is to measure the changes in tissue blood flow in the initial stage, that is, to obtain <BFI(t b )>.

[0040] Step (2) increases the pressure between the optical probe and the finger, and obtains the tissue blood flow change value rBF(t) in real time during the pressure increase process. When the change in the measured tissue blood flow rBF(t) value, i.e., rBF(t)-1|≥△, stops increasing the pressure, and keeps the pressure stable for 60s and measures the tissue blood flow rBF(t) value. Δ is an empirical coefficient, which is set between 0.75-0.95.

[0041] In step (3), the pressure between the optical probe and the finger is quickly released to 0, and the tissue blood flow change value rBF(t) during the entire pressure reduction process is obtained in real time. The tissue blood flow change value rBF(t) is continuously detected for 60 seconds to ensure that the tissue blood flow change value rBF(t) is restored to the initial moment.

[0042] Step 3: Establish rBF-CRT model to fit and calculate capillary refill time (CRT).

[0043] Specifically, according to the whole-process real-time tissue blood flow change data rBF(t) under the probe pressure change stored in step 2, a model between rBF(t) and CRT is established to calculate the CRT.

[0044] For further information, see Figure 3, a schematic diagram of the change of tissue blood flow rBF during the whole process of pressure modulation provided by an embodiment of the present invention. Among them, the time from t0 to t1 is the initial stage t1-t0=t b =60s, t2 to t3 is the stable holding stage after the pressure stops increasing (t3-t2=60s), t3 to t5 is the 60s of continuous detection after the pressure is released (t3-t2=60s), and t4 is the time t4 when rBF rebounds and returns to the initial value after the pressure is released. Therefore, capillary refill time CRT=t4-t3.

[0045] Step 4: Output and display of capillary refill time (CRT) results.

[0046] Specifically, the calculated capillary refill time data is displayed on the display interaction interface.

[0047] In an exemplary embodiment, Figure 2 As shown, the present invention provides a capillary refill time detection device, including a diffusion-related spectroscopy module 1, an automatic control module 2 and a pressure-modulated optical probe 3; the diffusion-related spectroscopy module 1 and the pressure-modulated optical probe 3 are both connected to the automatic control module 2; the diffusion-related spectroscopy module 1 is connected to the pressure-modulated optical probe 3.

[0048] The diffuse correlation spectroscopy module 1 is used to: send near-infrared light to the finger area of ​​the object to be measured, detect the scattered light spots in the measured area, calculate the light intensity autocorrelation function based on the scattered light spots to determine the tissue blood flow (rBF) in the measured area, and detect the change of tissue blood flow in the measured part in real time during the process of pressure change of the optical probe;

[0049] The automatic control module 2 is used to: establish an rBF-CRT model to fit and calculate the capillary refill time (CRT) according to the real-time changes in the tissue blood flow of the measured area, and display an interactive interface to show the real-time changes in the tissue blood flow (rBF) of the measured area and the capillary refill time (CRT);

[0050] The pressure modulated optical probe 3 is used to transmit the near-infrared light emitted by the diffusion correlation spectroscopy module to the surface of the measured part, receive the scattered light spot after diffuse reflection and transmit it to the diffusion correlation spectroscopy module, and adjust the pressure change between the optical probe and the finger part according to the instructions of the automatic control module.

[0051] In this embodiment, the diffusion correlation spectrum module 1 includes: a light source module, a detection module, and an autocorrelation calculation module;

[0052] The light source module is used to: send near infrared light to the finger area of ​​the object to be measured;

[0053] The detection module is used to: receive scattered light spots after diffuse reflection;

[0054] The autocorrelation calculation module is used to calculate the light intensity autocorrelation function according to the near-infrared scattered light spot signal to evaluate the movement state of red blood cells in the measured tissue.

[0055] In this embodiment, the automatic control module 2 includes: a data storage module, a pressure automatic modulation module, a tissue blood flow calculation module, a capillary refill time calculation module, and a display interaction interface;

[0056] The data storage module is used to store the near-infrared scattered light spot signal acquired by the pressure modulated optical probe, the light intensity autocorrelation function signal calculated by the diffusion correlation spectrum module, the real-time change signal of the tissue blood flow, the capillary refilling time signal and other related data;

[0057] The automatic pressure modulation module is used to: control the pressure change between the pressure modulation optical probe and the finger part;

[0058] The tissue blood flow calculation module is used to: obtain a real-time tissue blood flow (rBF) signal by fitting and calculating the light intensity autocorrelation function signal in the data storage module;

[0059] The capillary refill time calculation module is used to establish an rBF-CRT model to fit and calculate the capillary refill time (CRT) signal according to the real-time tissue blood flow (rBF) signal determined by the tissue blood flow calculation module.

[0060] See also Figure 3 , a schematic diagram of the change of tissue blood flow rBF during the whole process of pressure modulation provided by an embodiment of the present invention. Among them, the time from t0 to t1 is the initial stage t1-t0=t b =60s, t2 to t3 is the stable holding stage after the pressure stops increasing (t3-t2=60s), t3 to t5 is the 60s of continuous detection after the pressure is released (t3-t2=60s), and t4 is the time t4 when rBF rebounds and returns to the initial value after the pressure is released. Therefore, capillary refill time CRT=t4-t3.

[0061] In the present embodiment, the acquisition and calculation of tissue blood flow (rBF) data during the pressure regulation process is a core step, which is directly related to the calculation accuracy of the capillary refill time (CRT). It is crucial to obtain information reflecting the changes in tissue blood flow in the finger part of the measured object through diffusion correlation spectroscopy technology; in the present embodiment, the automatic modulation of pressure between the pressure modulation optical probe and the finger part is another key step. Through the real-time acquisition of tissue blood volume change data, the pressure value between the optical probe and the measured part is automatically controlled, laying the foundation for the tissue blood flow in the subsequent pressure modulation process; in the present embodiment, the establishment of the rBF-CRT model and the capillary refill time (CRT) fitting calculation are another key step. The model evaluation algorithm is used to perform in-depth analysis of the real-time change signal of the blood flow of the measured tissue, thereby realizing the accurate calculation of the capillary refill time.

[0062] The display interaction interface is used to display the real-time changes in tissue blood flow (rBF) and capillary refill time (CRT) in the measured area, and to achieve coordinated control among the pressure automatic modulation module, tissue blood flow calculation module and capillary refill time calculation module according to operator instructions.

[0063] In this embodiment, the pressure modulated optical probe 3 is used to: transmit the near-infrared light emitted by the diffusion-related spectroscopy module to the surface of the measured part, receive the scattered light spot after diffuse reflection and transmit it to the diffusion-related spectroscopy module, and adjust the pressure change between the optical probe and the finger part according to the instructions of the automatic control module.

[0064] A specific implementation process of the above capillary refill time detection device in practical application is as follows:

[0065] Step 1: Input the information of the object to be measured.

[0066] The capillary refill time detection device first inputs the basic information of the subject to be detected, including name, age, gender, height, weight, etc., through an input detection device (such as a touch screen, keyboard or external data interface).

[0067] Step 2: Real-time continuous detection of finger tissue blood flow (rBF).

[0068] The subject places the finger on the pressure modulated optical probe 3, and the diffusion correlation spectrum module 1 sends near-infrared light to the finger area of ​​the subject, detects the scattered light spots in the measured area, calculates the light intensity autocorrelation function based on the scattered light spots, and determines the tissue blood flow in the measured area, and detects the changes in tissue blood flow in the measured part in real time.

[0069] Step 3: Turn on the capillary refill time (CRT) test.

[0070] The operator starts the measurement of capillary refill time, and the detection device automatically controls the pressure change between the optical probe and the finger. During the pressure change adjustment process, the change of tissue blood flow (rBF) of the measured finger is detected in real time throughout the whole process. The pressure value between the optical probe and the finger is detected in real time, and the pressure value between the optical probe and the finger is automatically controlled according to the change of the real-time detected tissue blood flow (rBF) signal. Based on the real-time change data of tissue blood flow (rBF), the rBF-CRT model is established to fit and calculate the capillary refill time (CRT).

[0071] Step 4: Output and display the results.

[0072] The capillary refill time detection device displays and outputs the calculated capillary refill time (CRT) data through the display interaction interface.

[0073] The present invention proposes for the first time to use diffusion correlation spectroscopy technology for the detection of capillary refill time (CRT). Diffusion correlation spectroscopy obtains changes in blood flow in tissue microcirculation. Compared with existing capillary refill time detection methods, diffusion correlation spectroscopy technology can more directly reflect capillary refill time (CRT). In addition, the present invention automatically controls the pressure value adjustment between the optical probe and the finger through changes in tissue blood flow for the first time, establishes an rBF-CRT model to fit and calculate the capillary refill time (CRT), realizes the synchronous detection of tissue blood flow (rBF) and capillary refill time (CRT), and independently develops a capillary refill time detection device based on diffusion correlation spectroscopy technology. It can be seen that the present invention essentially solves the pain point problems of existing microcirculation assessments, and realizes accurate quantification of capillary refill time (CRT) through real-time detection of changes in tissue blood flow and combined with model calculations.

[0074] In addition, there are some alternatives to the above capillary refill time detection method and device that can also achieve the purpose of the present invention, that is, to detect the capillary refill time (CRT). The following are several possible alternatives:

[0075] (1) Capillary refill time detection based on multimodal biosignals.

[0076] In addition to tissue blood flow, other medical signals of the measured object (such as electrocardiogram, blood pressure, respiratory rate, etc.) also contain rich and effective information. Therefore, a capillary refill time detection system based on multimodal biological signals can be designed. The system comprehensively determines the capillary refill time of the measured object by simultaneously collecting and analyzing multiple medical signals.

[0077] (2) Comprehensive evaluation based on artificial intelligence and big data

[0078] With the continuous development of artificial intelligence and big data technology, the above advanced technologies can be used to build a comprehensive evaluation model to achieve accurate prediction of capillary refill time. The model can integrate multi-source data (including biological signals, medical images, blood biochemical indicators, etc.), extract key features through deep learning and data mining algorithms, and train and optimize based on a large amount of historical data to improve the accuracy and reliability of the evaluation.

[0079] It should be noted that although these alternatives can realize the assessment of heart failure prognosis, in actual work, they are affected by the connection problems between various examination methods, the complexity of data integration, and the accuracy and consistency of the assessment results.

[0080] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A capillary refill time detection device, characterized in that: The capillary refill time detection device comprises: a diffusion-related spectroscopy module, an automatic control module and a pressure modulation optical probe; the diffusion-related spectroscopy module and the pressure modulation optical probe are both connected to the automatic control module; the diffusion-related spectroscopy module is connected to the pressure modulation optical probe; The diffusion correlation spectroscopy module is used to: send near-infrared light to the finger area of ​​the object to be measured, detect the scattered light spots in the measured area, calculate the light intensity autocorrelation function based on the scattered light spots to determine the tissue blood flow (rBF) in the measured area, and detect the change of tissue blood flow in the measured part in real time during the process of pressure change of the optical probe; The automatic control module is used to: calculate and determine the capillary refill time (CRT) according to the real-time change of tissue blood flow in the measured area, and display the real-time change of tissue blood flow (rBF) and capillary refill time (CRT) in the measured area on the display interactive interface; The pressure modulated optical probe is used to transmit the near-infrared light emitted by the diffusion correlation spectroscopy module to the surface of the measured part, receive the scattered light spot after diffuse reflection and transmit it to the diffusion correlation spectroscopy module, and adjust the pressure change between the optical probe and the finger part according to the instructions of the automatic control module.

2. The capillary refill time detection device according to claim 1, characterized in that: The automatic control module includes: a data storage module, a pressure automatic modulation module, a tissue blood flow calculation module, a capillary refill time calculation module, and a display interaction interface; The data storage module is used to: store the near-infrared scattered light spot signal acquired by the pressure modulated optical probe, store the light intensity autocorrelation function signal calculated by the diffusion correlation spectrum module, store the real-time change signal of the tissue blood flow, and store the capillary refill time signal; The automatic pressure modulation module is used to: control the pressure change between the pressure modulation optical probe and the finger part; The tissue blood flow calculation module is used to: obtain a real-time tissue blood flow (rBF) signal by fitting and calculating the light intensity autocorrelation function signal in the data storage module; The capillary refill time calculation module is used to: establish an rBF-CRT model to fit and calculate the capillary refill time (CRT) according to the real-time tissue blood flow (rBF) signal determined by the tissue blood flow calculation module; The display interaction interface is used to display the real-time changes in tissue blood flow (rBF) and capillary refill time (CRT) in the measured area, and to achieve coordinated control among the pressure automatic modulation module, tissue blood flow calculation module and capillary refill time calculation module according to operator instructions.

3. The capillary refill time detection device according to claim 1, characterized in that: The pressure modulated optical probe is used to transmit the near-infrared light emitted by the diffusion correlation spectroscopy module to the surface of the measured part, receive the scattered light spot after diffuse reflection and transmit it to the diffusion correlation spectroscopy module, and adjust the pressure change between the optical probe and the finger part according to the instructions of the automatic control module.

4. A detection method using the device of claim 1, characterized in that: include: Place the finger of the object to be measured at the optical probe position; Irradiate the finger of the object to be tested with a near-infrared light signal, receive the near-infrared scattered light spot signal after diffuse reflection, and detect the change of tissue blood flow in the finger of the object to be tested in real time based on the diffusion correlation spectroscopy technology; The operator turns on the measurement of capillary refill time (CRT), and the automatic control realizes the adjustment of the pressure change between the optical probe and the finger part; During the pressure change adjustment process, the changes in tissue blood flow (rBF) of the measured finger are detected in real time throughout the process; Based on the real-time change data of tissue blood flow (rBF), the capillary refill time (CRT) is calculated and displayed.

5. The detection method according to claim 4, characterized in that: Automatic control to adjust the pressure change between the optical probe and the finger, including: Step (1) is to measure the changes in tissue blood flow in the initial stage, that is, to obtain<BFI(tb)> ; Step (2) increases the pressure between the optical probe and the finger, and obtains the tissue blood flow change value rBF(t) in real time during the pressure increase process. When the change in the measured tissue blood flow rBF(t) value, i.e., |rBF(t)-1|≥△, stops increasing the pressure, and keeps the pressure stable for 60 seconds while measuring the tissue blood flow rBF(t) value; where △ is an empirical coefficient, which is set between 0.75 and 0.

95. In step (3), the pressure between the optical probe and the finger is quickly released to 0, and the tissue blood flow change value rBF(t) during the entire pressure reduction process is obtained in real time. The tissue blood flow change value rBF(t) is continuously detected for 60 seconds to ensure that the tissue blood flow change value rBF(t) is restored to the initial moment.

6. The detection method according to claim 4, characterized in that: According to the real-time change data of tissue blood flow (rBF), the rBF-CRT model is established to fit and calculate the capillary refill time (CRT), including: According to the stored real-time tissue blood flow change data rBF(t) under the probe pressure change, a model between rBF(t) and CRT is established to calculate CRT; Provides a schematic diagram of the change of tissue blood flow rBF during the whole process of pressure modulation; among which, the time from t0 to t1 is the initial stage t1-t0=t b =60s, time t2 to t3 is the stable maintenance stage after the pressure stops increasing and t3-t2=60s, time t3 to t5 is the 60s of continuous detection after the pressure is released and t3-t2=60s, t4 is the time t4 when rBF rebounds and returns to the initial value after the pressure is released; capillary refill time CRT=t4-t3.

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