A full optical end-tidal capnography device for high flow oxygen supply

Abstract

This invention provides a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply, comprising an air inlet (1), an air outlet (2), an infrared light source (3), a near-infrared light source (4), a cavity (5), M photodiodes (6), and a control unit (7); the infrared LED light source has a center wavelength of 4.3 μm, the near-infrared LD light source has a center wavelength of 1310 nm, the M photodiodes (6) are arranged in a ring within the detection tube (8), and the control unit (7) carries a detection method to achieve high-speed and high-precision measurement. This invention can be used for high-speed and accurate measurement of exhaled CO2 concentration in clinical high-flow ventilators.

Description

Technical Field

[0001] This invention relates to a CO2 sensing system, and more particularly to a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply. Background Technology

[0002] Infrared spectroscopy is the primary method for detecting CO2 content in gases. While it offers high speed, it suffers from limitations in accuracy and sensitivity, and is easily affected by environmental factors. This is mainly because the method relies solely on the infrared absorption effect and Beer-Lambert's law, resulting in high accuracy for stationary gases but making it difficult to guarantee accuracy for CO2 in fluids. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply, which combines infrared absorption and near-infrared scattering to significantly improve the detection accuracy of CO2 concentration in fluids.

[0004] The specific technical solution adopted in this invention is as follows:

[0005] A fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply, the device comprising a detection tube, an inlet tube, an outlet tube, a cavity, multiple photodiodes, a far-infrared light source, a near-infrared light source, and a control unit, wherein the cavity is disposed inside the detection tube, the inlet tube passes through the detection tube and connects to the cavity, the outlet tube passes through the detection tube and connects to the cavity, and windows are opened on both sides of the diameter opposite to the central region of the cavity, namely a first window and a second window, respectively; the far-infrared light source and the near-infrared light source are positioned near the cavity to illuminate the cavity; the multiple photodiodes are arranged in a ring relative to the cavity, at least one photodiode is aligned with the second window; the multiple photodiodes, the far-infrared light source, and the near-infrared light source are all signal-connected to the control unit, and the control unit is configured as follows:

[0006] The far-infrared light source and the near-infrared light source are controlled to work alternately at a preset switching frequency, and simultaneously receive photoelectric signals collected by each photodiode. The switching frequency is matched with the collection frequency of the multiple photodiodes.

[0007] Based on the photoelectric signals collected by each photodiode, the CO2 concentration is calculated using the following formula (1):

[0008]

[0009] Where St represents the CO2 concentration of the gas flowing through it during time t, Δt represents the time interval between two consecutive switching of the infrared and near-infrared light sources, and I1t represents the photoelectric signal collected by the photodiode aligned with the second window. When m = 2…M1, I… m t represents the photoelectric signal collected by the photodiode located on one side of the second window but not aligned with the second window; M1 represents the number of photodiodes located on one side of the second window; when m = M1 + 1…M, I m t represents the photoelectric signal collected by the photodiode set on one side of the first window, M represents the total number of photodiodes, and parameters a, b, and c represent preset thresholds.

[0010] Furthermore, the parameters a, b, and c are determined by the following method: calibration samples of different concentrations are introduced into the device according to different flow rate settings, and the parameters a, b, and c are determined by least squares fitting in combination with the photoelectric signals collected by each photodiode.

[0011] Furthermore, the calibration sample is configured as follows: using a gas compressor, the sample is configured according to the composition ratio of human exhaled gas or air, the N2 and O2 ratio is fixed, and different concentrations of CO2 are mixed within a preset limit range of CO2 concentration to obtain the calibration sample.

[0012] Furthermore, the size of the first window is such that two light sources can be placed side by side, with the far-infrared light source and the near-infrared light source located on one side of the first window.

[0013] Furthermore, the size of the second window is 1 to 1.5 times that of the first window.

[0014] Furthermore, the cavity is cylindrical and is made of transparent glass randomly doped with titanium dioxide particles, the particle size of which is between 100nm and 1000nm.

[0015] Furthermore, the wavelength of the far-infrared light emitted by the far-infrared light source is 4.3 μm.

[0016] Furthermore, the wavelength of the near-infrared light emitted by the near-infrared light source is 1310nm.

[0017] Furthermore, the plurality of photodiodes are attached to the inner wall of the detection tube.

[0018] Furthermore, the far-infrared light source is an infrared LED light source, and the near-infrared light source is a near-infrared laser diode light source.

[0019] The beneficial effects of the present invention are as follows: The all-optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply provided by the present invention uses infrared absorption effect and near-infrared scattering effect to significantly improve the accuracy and sensitivity of CO2 concentration detection in flowing gas, while ensuring accuracy and realizing real-time detection of CO2 concentration in fluid. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0021] Figure 1 A schematic diagram of a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply according to an embodiment of the present invention is shown.

[0022] Figure 2 A schematic diagram of signal transmission is shown for a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply according to an embodiment of the invention.

[0023] In the diagram, 1 is the air inlet pipe, 2 is the air outlet pipe, 3 is the far-infrared light source, 4 is the near-infrared light source, 5 is the cavity, 6 is the photodiode, 7 is the control unit, and 8 is the detection tube. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0025] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0028] Figure 1 A schematic diagram of a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply according to an embodiment of the present invention is shown. The present invention provides a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply. Figure 1 As shown, the all-optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply includes a detection tube 8, an inlet tube 1, an outlet tube 2, a cavity 5, multiple photodiodes 6, a far-infrared light source 3, a near-infrared light source 4, and a control unit. The cavity 5 is disposed inside the detection tube 8. The inlet tube 1 passes through the detection tube 8 and connects to the cavity 5. The outlet tube 2 passes through the detection tube 8 and connects to the cavity 5. Windows are opened on both sides of the diameter of the central region of the cavity 5, namely the first window and the second window, respectively. The side corresponding to the first window is marked as side A in the figure, and the side corresponding to the second window is marked as side B in the figure. The far-infrared light source 3 and the near-infrared light source 4 are disposed near the cavity 5 so that the light source can illuminate the cavity 5. The multiple photodiodes 6 are arranged in a ring relative to the cavity 5, and at least one photodiode 6 is aligned with the second window. It should be noted that the cavity 5 can be fixedly disposed inside the detection tube 8. The fixing method includes, but is not limited to, fixing by at least one support beam, or fixing one end of the cavity 5 to the inlet pipe 1 and outlet pipe 2 respectively, and then fixing the detection tube 8 to the inlet pipe 1 and outlet pipe 2, using the inlet pipe 1 and outlet pipe 2 to fix the cavity 5 inside the detection tube 8. The first window and the second window are located in... Figure 1 The image is not shown and is only an example. In practice, it can be implemented as a transparent window on cavity 5 that allows infrared light waves to pass through.

[0029] When the device provided in the embodiments of the present invention is used, the design of multiple photodiodes 6 in conjunction with the first and second windows enables the photodiodes aligned with the second window to detect forward scattered light when the far-infrared light source 3 and the near-infrared light source 4 alternately irradiate the flowing gas inside the cavity 5. The photodiodes aligned with the second window can detect forward scattered light, while the photodiodes on the side of the second window (side B) that are not aligned with the second window can detect backward scattered light. The photodiodes on the side of the first window (side A) can detect backscattered light. Based on the scattered light detected by the multiple photodiodes in various directions, the CO2 concentration is calculated by the control unit 7.

[0030] Specifically Figure 2 A schematic diagram of signal transmission is shown for a fully optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply according to an embodiment of the invention. Figure 2 As shown, Figure 2 The middle arrow indicates the direction of signal flow. The multiple photodiodes 6, far-infrared light source 3, and near-infrared light source 4 are arranged according to... Figure 2 The connection method shown is a signal connection with the control unit 7. It should be noted that the "signal connection" mentioned herein includes, but is not limited to, one or a combination of connection via wire, connection via WiFi module, connection via Bluetooth module, and connection via 2G / 3G / 4G / 5G module. The specific form of signal connection in this embodiment of the invention is not specifically limited.

[0031] It should be noted that the control unit 7 can be a processing device that includes one or more general-purpose processing devices, such as a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), etc. More specifically, the control unit 7 can be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor that runs other instruction sets, or a processor that runs a combination of instruction sets. The control unit 7 can also be one or more special-purpose processing devices, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), system-on-a-chip (SoCs), etc.

[0032] The control unit 7 is configured as follows:

[0033] The far-infrared light source 3 and the near-infrared light source 4 are controlled to work alternately at a preset switching frequency, and simultaneously receive photoelectric signals collected by each photodiode 6. The switching frequency is matched with the collection frequency of the multiple photodiodes. The preset switching frequency is generally greater than or equal to 40Hz. The switching frequency determines the time interval between two adjacent switching of the infrared and near-infrared light sources. If the switching frequency is 40Hz, Δt = 0.025s.

[0034] Based on the photoelectric signals collected by each photodiode, the CO2 concentration is calculated using the following formula (1):

[0035]

[0036] Where St represents the CO2 concentration of the gas flowing through it during time t, Δt represents the time interval between two consecutive switching of the infrared and near-infrared light sources, and I1t represents the photoelectric signal collected by the photodiode aligned with the second window. When m = 2…M1, I… m t represents the photoelectric signal collected by the photodiode located on one side of the second window but not aligned with the second window; M1 represents the number of photodiodes located on one side of the second window; when m = M1 + 1…M, I m t represents the photoelectric signal collected by the photodiode located on one side of the first window, M represents the total number of photodiodes, and parameters a, b, and c represent preset thresholds. The preset thresholds can be fixed thresholds or a threshold range.

[0037] In some embodiments, the parameters a, b, c are determined by the following method:

[0038] Calibration samples of different concentrations are introduced into the device according to different flow rates, and the parameters a, b, c are determined by least squares fitting in combination with the photoelectric signals collected by each photodiode.

[0039] In this context, the "calibration sample" specifically refers to a customized standard sample of the flowing gas to be detected by this device. The calibration sample varies depending on the application scenario. As an example only, the device provided in this embodiment can be applied to high-flow ventilators. By rapidly detecting the concentration of CO2 in exhaled gas (more than 20 times per second), the oxygen supply flow rate of the high-flow ventilator can be adjusted, improving the treatment effect for patients with various respiratory failures and reducing the workload of medical staff. In this case, the calibration sample can be human exhaled gas.

[0040] In this embodiment of the invention, calibration samples with different CO2 concentrations are introduced into the cavity through the inlet pipe at different flow rate / velocity settings. The far-infrared light source 3 and the near-infrared light source 4 are controlled by the control unit 7 to work alternately at a preset switching frequency, while simultaneously receiving photoelectric signals collected by each photodiode 6. Given the current CO2 concentration in the fluid, the parameters a, b, and c are determined by least squares fitting based on formula (1). The parameters a, b, and c determined in this way can greatly improve the accuracy of real-time detection of CO2 concentration in flowing gas.

[0041] In some embodiments, a gas compressor is configured according to the composition ratio of human exhaled gas or air, the N2 and O2 ratio is fixed, and different concentrations of CO2 are mixed within a preset limit range of CO2 concentration to obtain a calibration sample.

[0042] In some embodiments, such as Figure 1 As shown, the size of the first window is such that two light sources can be placed side by side, and the far-infrared light source 3 and the near-infrared light source 4 are located on one side (side A) of the first window.

[0043] In some embodiments, the size of the second window is 1 to 1.5 times the size of the first window.

[0044] In some embodiments, such as Figure 1 As shown, the cavity 5 is cylindrical and is made of transparent glass randomly doped with titanium dioxide particles, the particle size of which is between 100nm and 1000nm.

[0045] In some embodiments, such as Figure 1 As shown, the wavelength of the far-infrared light emitted by the far-infrared light source 3 is 4.3 μm. The wavelength of the near-infrared light emitted by the near-infrared light source 4 is 1310 nm.

[0046] In some embodiments, such as Figure 1 As shown, the plurality of photodiodes 6 are attached to the inner wall of the detection tube 8.

[0047] In some embodiments, the far-infrared light source 3 is an infrared LED light source, and the near-infrared light source 4 is a near-infrared laser diode light source.

[0048] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A fully optical end-tidal capnography device for high flow oxygen supply, characterized in that, The device includes a detection tube, an inlet tube, an outlet tube, a cavity, multiple photodiodes, a far-infrared light source, a near-infrared light source, and a control unit. The cavity is disposed inside the detection tube. The inlet tube passes through the detection tube and connects to the cavity. The outlet tube passes through the detection tube and connects to the cavity. Windows are opened on both sides of the diameter opposite to the central region of the cavity, namely a first window and a second window. The far-infrared light source and the near-infrared light source are positioned near the cavity to illuminate it. The multiple photodiodes are arranged in a ring relative to the cavity, with at least one photodiode aligned with the second window. The multiple photodiodes, the far-infrared light source, and the near-infrared light source are all signal-connected to the control unit. The control unit is configured as follows: The far-infrared light source and the near-infrared light source are controlled to work alternately at a preset switching frequency, and simultaneously receive photoelectric signals collected by each photodiode. The switching frequency is matched with the collection frequency of the multiple photodiodes. Based on the photoelectric signals collected by each photodiode, the CO2 concentration is calculated using the following formula (1): Where S(t) represents the CO2 concentration of the gas flowing through it during time t, Δt represents the time interval between two consecutive switching of the infrared and near-infrared light sources, and I1(t) represents the photoelectric signal collected by the photodiode aligned with the second window. When m = 2…M1, I m (t) represents the photoelectric signal collected by the photodiode located on one side of the second window but not aligned with the second window, and M1 represents the number of photodiodes located on one side of the second window. When m = M1 + 1…M, I m (t) represents the photoelectric signal collected by the photodiode set on one side of the first window, M represents the total number of photodiodes, and parameters a, b, c represent preset thresholds.

2. The apparatus of claim 1, wherein, The parameters a, b, and c are determined by the following method: Calibration samples of different concentrations are introduced into the device according to different flow rates, and the parameters a, b, c are determined by least squares fitting in combination with the photoelectric signals collected by each photodiode.

3. The apparatus of claim 2, wherein, The calibration sample is configured using the following method: A calibration sample is prepared by using a gas compressor to prepare the gas according to the composition ratio of human exhaled gas or air, fixing the N2 and O2 ratio, and mixing different concentrations of CO2 within a preset limit range of CO2 concentration.

4. The apparatus of claim 1, wherein, The size of the first window is such that two light sources can be placed side by side, and the far-infrared light source and the near-infrared light source are located on one side of the first window.

5. The apparatus of claim 1 or 4, wherein The size of the second window is 1 to 1.5 times that of the first window.

6. The apparatus of claim 1, wherein, The cavity is cylindrical and is made of transparent glass randomly doped with titanium dioxide particles, the particle size of which is between 100nm and 1000nm.

7. The apparatus of claim 1, wherein, The wavelength of the far-infrared light emitted by the far-infrared light source is 4.3 μm.

8. The apparatus of claim 1, wherein, The wavelength of the near-infrared light emitted by the near-infrared light source is 1310nm.

9. The all-optical capnometry device for high flow oxygen supply of claim 1, wherein, The plurality of photodiodes are attached to the inner wall of the detection tube.

10. The all-optical end-tidal carbon dioxide monitoring device for high-flow oxygen supply as described in claim 1, characterized in that, The far-infrared light source is an infrared LED light source, and the near-infrared light source is a near-infrared laser diode light source.

Images