CO2 calibration-based exhaled air nitric oxide (FeNO) detection system

Abstract

The invention discloses an exhaled air nitric oxide (FeNO) detection system based on CO2 calibration, and belongs to the technical field of medical detection equipment. Comprising a gas collection module, a gas calibration module, a detection pool and a pressure control module, the gas collecting module comprises a two-way blowing handle, a one-way valve and a molecular sieve filtering cavity which are arranged in the two-way blowing handle, and a flow sensor arranged outside an expiration channel, and is used for separating and filtering interference gas; the gas calibration module monitors the CO2 concentration in expired gas in real time through a CO2 sensor array, when the CO2 concentration reaches 4%, FeNO detection is triggered, and pulmonary alveolar gas is accurately calibrated; the pressure control module adjusts the flow through linkage of a vacuum pump, a needle valve and a pressure sensor, and maintains the pressure of the detection pool to be stabilized at 0.3 atm. Through CO2 concentration calibration and dynamic pressure control, the problems of identification deviation and insufficient detection precision of alveolar gas in the prior art are solved, the detection error is smaller than or equal to 1 ppb, and the method is suitable for portable medical detection scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of medical gas detection equipment, and in particular to an exhaled nitric oxide (FeNO) detection system based on CO2 concentration calibration, and is particularly suitable for a portable medical device that can achieve high-precision FeNO measurement through dynamic pressure control and alveolar gas identification. Background Art

[0002] Exhaled nitric oxide (EeNO), as a key biomarker of airway inflammation, is widely used in the diagnosis, efficacy evaluation and disease monitoring of respiratory diseases such as asthma. Existing EeNO detection technology mainly relies on chemiluminescence and electrochemical methods, but there are still technical bottlenecks. First, the calibration accuracy of alveolar gas is insufficient. Although the chemiluminescence method has high sensitivity (detection limit <1ppb), it relies on multi-flow segment measurement and needs to indirectly infer the source of alveolar gas through the flow rate threshold, resulting in a calibration error of >15%. Although the electrochemical method is low-cost, it is easily affected by environmental temperature and humidity, and cannot distinguish between airway and alveolar gas, resulting in poor detection consistency. Second, the gas flow control is poorly stable. The existing equipment uses mechanical valves to control the flow. At high flow rates (>50 mL / s), the response delay is >200 ms, resulting in over-pumping or accumulation of gas (pressure fluctuation +20%), thereby diluting the sample.

[0003] Therefore, there is an urgent need for a portable FeNO detection system that can accurately calibrate alveolar gas and achieve dynamic flow control. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in view of the defects of the existing FeNO detection technology, such as the error ≥15% caused by the dependence of alveolar gas calibration on flow rate and the poor stability of gas flow control (pressure fluctuation ±20%), an exhaled nitric oxide (FeNO) detection system based on CO2 concentration calibration and dynamic pressure control is provided. Through CO2 threshold trigger detection, detection cell and vacuum pump-needle valve linkage adjustment, portable detection with detection error ≤0.5 ppb, pressure stability ±5% and total weight ≤2kg is achieved.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: The present invention provides an exhaled nitric oxide (FeNO) detection system based on CO2 calibration, comprising a gas collection module, a gas calibration module, a detection cell and a pressure control module; The collaborative working logic of each module is as follows: The gas collection module includes a double-pass blowing handle, a molecular sieve filter chamber, and a flow sensor outside the exhalation channel. The molecular sieve filter chamber is used to adsorb external NO interference components (adsorption rate ≥ 95%). The CO2 calibration module is integrated into the gas flow path and is equipped with a CO2 sensor array with an in-built detection error of ≤±0.1%. When the CO2 concentration in exhaled breath reaches 4%±0.2%, it sends a trigger signal to the control module; The detection cell has a volume of 250 mL and an optical path of 26.4 m. It uses a silver-plated concave spherical mirror with a reflectivity of ≥99.9% (mirror spacing 12.3 cm), and a porous ceramic diffuser with a pore diameter between 1 - 10 μm is set at the inlet. Combined with an impeller-type gas stirring device (rotation speed 100 - 500 rpm), it achieves uniform gas distribution; The pressure control module is linked by a vacuum pump, a needle valve, and a pressure sensor to dynamically adjust the gas flow rate and maintain the pressure in the detection cell stable at 0.3 atm±5%; The control module processes temperature, pressure, and flow rate data in real time based on the PID algorithm and outputs the corrected FeNO concentration value (error ≤0.5 ppb).

[0006] As a further optimization of the present invention, the trigger signal of the CO2 calibration module starts the NO detection process of the detection cell, and the detection band is in the mid-infrared spectrum of 5.2 - 5.3 μm; The detection cell integrates a temperature control unit (temperature control range 25°C±1°C, accuracy ±0.5°C) and a modular packaging structure (total weight ≤1.5 kg), and is connected to an external light source through an M12 aviation plug; The control module dynamically corrects the detection results using the PID algorithm and transmits data to the terminal device via Wi-Fi / Bluetooth.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: The calibration accuracy of alveolar gas is high. By directly calibrating alveolar gas through the CO2 concentration threshold (4%±0.2%), replacing the traditional multi-flow rate indirect inference method, the calibration error is reduced from ≥15% to ≤3%; The detection sensitivity and stability are improved. The detection cell (250 mL) combined with an optical path of 26.4 m and a gas stirring device enables the detection limit to reach 0.5 ppb, and the repeatability error ≤0.5 ppb; It has strong anti-interference ability. The molecular sieve filter chamber (adsorption rate ≥95%) and the temperature control unit (±0.5°C) effectively suppress environmental NO and temperature and humidity interference. Description of the Drawings

[0008] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings: Figure 1 It is a schematic diagram of the system structure and gas flow path of the present invention; Figure 2It is a sectional view structure diagram of the gas collection module of the present invention; Figure 3 It is the dynamic change curve of CO2 and NO concentrations over time during human exhalation (flow rate 50 mL / s); In the figure: 1. Gas collection module; 2. CO2 calibration module; 3. Detection cell; 4. Pressure control module; 11. Double-pass blowing handle; 12. Check valve; 13. Molecular sieve filtration chamber; 14. Flow sensor; 31. Temperature control unit; 32. Temperature sensor; 33. Gas stirring device; 41. Vacuum pump; 42. Needle valve; 43. Pressure sensor; 44. PID control unit. Specific embodiments

[0009] The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0010] As Figures 1-3 shown, the present invention provides a fractional exhaled nitric oxide (FeNO) detection system based on CO2 calibration, including: a gas collection module 1, a CO2 calibration module 2, a detection cell 3, and a pressure control module; The gas collection module 1 includes a double-pass blowing handle 11, a check valve 12 installed inside the double-pass blowing handle 11, a molecular sieve filtration chamber 13 (using zeolite molecular sieve, pore size 0.5 nm, adsorption rate ≥ 95%), and a flow sensor 14 (monitoring range 10–200 mL / s) outside the exhalation channel; The CO2 calibration module 2 is built-in with a CO2 sensor array with a detection error ≤ ±0.1%. When the CO2 concentration in exhaled breath reaches 4% ± 0.2%, it triggers the detection process of the detection cell; The detection cell 3 has a volume of 250 mL, an optical path of 26.4 m, a reflectivity ≥ 99.9% (the reflectivity test wavelength is 5.2~5.3 μm), and is integrated with a temperature control unit (25°C ± 1°C) and an impeller-type gas stirring device (rotation speed 100 - 500 rpm); The pressure control module 4 is linked through a vacuum pump 41, a needle valve 42, and a pressure sensor 43 to maintain the pressure in the cell at 0.3 atm ± 5%.

[0011] Furthermore, the CO2 calibration module 2 is integrated in the path of the flowing gas. The CO2 sensor in this module real-time detects the CO2 concentration in exhaled breath. When the CO2 concentration reaches 4%, the CO2 calibration module 2 sends a signal to the control module. After receiving the signal, the control module starts the NO concentration detection process of the detection cell 3, thereby accurately determining the alveolar gas stage for detecting FeNO and achieving the accurate extraction of FeNO.

[0012] Further, the detection cell 3 is composed of two silver-plated concave spherical mirrors with a reflectivity higher than 99.9%. The distance between the mirrors is 12.3 cm, and the weight of the cell body is ≤ 1.5 kg; A micro gas diffuser is provided at the gas inlet of the detection cell 3. The diffuser is made of porous ceramic material with a uniform pore size distribution between 1 - 10 μm. After the gas passes through the diffuser, it can be evenly dispersed into the interior of the cell body, avoiding problems such as air flow impact and excessive local concentration; The outer shell of the detection cell 3 is made of corrosion-resistant material, which can maintain good airtightness and stability for a long time. The total weight of the entire detection system is ≤ 2 kg, meeting the requirements of portable devices; The detection cell 3 is connected to an external light source and a detection module through a standardized interface and can be configured with lasers of different wavelengths; Further, a temperature control unit 31 and a temperature sensor 32 are provided inside the detection cell 3. The temperature sensor 32 monitors the temperature change inside the cell body in real time. When the temperature deviates from the preset operating temperature range, such as 25°C ± 1°C, the control unit will activate the cooling sheet or heating wire of the temperature control unit 31 for temperature adjustment, and the adjustment accuracy can reach ±0.5°C. Through precise temperature control, the optical performance of the detection cell can be ensured to be stable, reducing the impact of temperature change on the detection result.

[0013] Further, a gas stirring device 33 is also provided inside the detection cell 3. The gas stirring device 33 is an impeller structure driven by a micro motor, which can form a weak turbulent flow of the gas inside the cell body without affecting stability, promoting the full mixing and reaction of gas molecules and light, and improving the detection sensitivity.

[0014] Further, the detection cell 3 is electrically connected to the control module, and transmits the data collected by the internal integrated temperature sensor 32 and pressure sensor 43 to the control module in real time. The control module dynamically corrects the detection result through the PID algorithm and outputs the FeNO concentration value with an error ≤ 0.5 ppb; The detection cell 3 is also connected to an external light source and a detection module through a standardized interface, obtains the laser light source required for detection, and transmits the detected NO concentration signal to the detection module for subsequent analysis and processing.

[0015] Specific detection process: The subject holds the double-pass blowing handle 11 and starts to exhale evenly. First, when inhaling, the air passes through the molecular sieve filter chamber 13. The molecular sieve filter chamber 13 adsorbs the NO interference components in the external air, and the adsorbed air is inhaled into the body. When exhaling, the exhaled gas passes through the one-way valve 12. The flow sensor 14 monitors the gas flow rate in real time and transmits the data to the control module, and the preliminarily processed gas enters the CO2 calibration module 2.

[0016] The gas entering the CO2 calibration module 2 has its CO2 concentration detected in real time by the CO2 sensor array inside the module. When the detected CO2 concentration reaches 4%, it indicates that the exhalation enters the third stage, i.e., the alveolar gas stage. At this time, the CO2 calibration module 2 sends a signal to the control module. After receiving the signal, the control module starts the NO concentration detection process in the detection cell 3. This process accurately determines the alveolar gas stage for FeNO detection, effectively eliminating the interference of outside air and airway gas.

[0017] After the control module starts the NO concentration detection process, the vacuum pump 41 begins to work, extracting and transporting the calibrated alveolar gas to the detection cell 3. The gas evenly disperses into the interior of the cell body through the micro gas diffuser at the gas path inlet of the detection cell 3. The optical path length of the detection cell 3 is 26.4 meters, and the number of reflections can reach 215 times, greatly increasing the interaction distance between light and gas. During the detection process, the gas stirring device 33 is started to form a weak turbulent flow of the gas inside the cell body, promoting the full mixing and reaction of gas molecules and light. At the same time, the temperature sensor 32 monitors the temperature change inside the cell body in real time. When the temperature deviates from the preset working temperature range of 25°C ± 1°C, the refrigerating sheet or heating wire of the temperature control unit 31 is started for temperature adjustment to ensure the stable optical performance of the detection cell and reduce the influence of temperature change on the detection result. The pressure sensor 43 inside the detection cell 3 monitors the pressure change inside the cavity in real time and transmits the data to the control module. The optical sensor captures the NO concentration signal and transmits the signal to the detection module for subsequent analysis and processing.

[0018] After the detection module receives the NO concentration signal transmitted from the detection cell 3, it performs preprocessing operations such as amplification and filtering, and then converts the signal into a NO concentration value through a preset algorithm. The control module uses the PID algorithm to dynamically correct the NO concentration data, temperature data, pressure data, and flow data, and finally transmits the data to the terminal device through Wi-Fi / Bluetooth.

[0019] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A CO2-calibrated exhaled nitric oxide (FeNO) detection system, characterized in that: include: Gas collection module, gas calibration module, detection cell and pressure control module; The gas collection module includes a two-way blowing handle, a one-way valve and a molecular sieve filter chamber installed inside the handle, and a flow sensor outside the exhalation channel. The one-way valve is used to separate the sampled gas from the exhaust gas, and the molecular sieve filter chamber is used to absorb NO interference components in the external air. The CO2 calibration module is integrated in the gas flow path and has a built-in CO2 sensor array with a detection error of ≤±0.1%. When the CO2 concentration in the exhaled air reaches 4%, a trigger signal is sent to the control module; The detection cell comprises a cell body with a volume of 250 mL and an optical path length of 26.4 m (achieved by multiple reflections) (the optical path length is configured to enhance detection sensitivity), and a porous ceramic diffuser with an aperture of 1-10 μm is provided at the gas path inlet; The pressure control module includes a vacuum pump, a needle valve and a pressure sensor. The vacuum pump is connected to the outlet of the CO2 calibration module and the detection cell. The needle valve is used to adjust the gas flow rate. The pressure sensor monitors the pressure in the detection cell in real time. The control module dynamically adjusts the vacuum pump speed and the needle valve opening according to the CO2 calibration signal and pressure data to maintain the pressure in the cell stable at 0.3 atm±5%.

2. The detection system according to claim 1, characterized in that: The trigger signal of the CO2 calibration module starts the NO detection process of the detection cell, and the detection band is 5.2~5.3 μm in the mid-infrared spectrum.

3. The detection system according to claim 1, characterized in that: The detection cell comprises: two silver-plated concave spherical mirrors with a reflectivity of ≥99.9% (the reflectivity test wavelength is 5.2-5.3 μm), with a mirror spacing of 12.3 cm; the outer shell is made of indium steel, with a total weight of ≤1.5 kg; a modular packaging structure, connected to an external light source and a detection module through an M12 aviation plug; a porous ceramic micro gas diffuser (aperture between 1-10 μm) at the inlet; an integrated temperature control unit (temperature control range 25°C±1°C, adjustment accuracy ±0.5°C) and an impeller-type gas stirring device (rotation speed 100-500 rpm) are integrated in the detection cell.

4. The detection system according to claim 1, characterized in that: The pressure control module receives the temperature, pressure and flow data of the detection cell, dynamically corrects the detection result through the PID algorithm, and outputs a FeNO concentration value with an error of ≤0.5 ppb and a detection limit of ≤0.5 ppb.

Images