阅读说明：本技术 一种呼出气体中内源性丙酮的检测系统及方法 (System and method for detecting endogenous acetone in exhaled air ) 是由 娄存广 刘秀玲 王鑫 侯凯旋 荆聪蕊 张建涛 于 2019-10-22 设计创作，主要内容包括：本发明提供了一种呼出气体中内源性丙酮的检测系统及方法,所述检测系统包括冷肼预浓缩装置、赫里奥特气体池、两个垂直腔面发射激光二极管、两个光电探测器、信号处理系统以及控制系统。本发明利用冷肼预浓缩装置去除了呼出气体中水分的干扰,提高了待测气体浓度,利用近红外可调谐半导体吸收光谱测量系统实现死腔气和肺泡气的在线实时检测,同时,能够实时获得不同呼吸阶段丙酮气体含量,具有更高的检测精度和灵敏度。(The invention provides a detection system and a detection method for endogenous acetone in exhaled air, wherein the detection system comprises a cold hydrazine preconcentration device, a Herriott gas pool, two vertical cavity surface emitting laser diodes, two photoelectric detectors, a signal processing system and a control system. The invention utilizes the cold hydrazine preconcentration device to remove the interference of moisture in the exhaled air, improves the concentration of the gas to be detected, utilizes the near-infrared tunable semiconductor absorption spectrum measurement system to realize the online real-time detection of dead space gas and alveolar gas, can obtain the content of acetone gas at different respiratory stages in real time, and has higher detection precision and sensitivity.)

1. A detection system for endogenous acetone in exhaled breath, comprising:

the cold hydrazine preconcentration device is used for removing moisture in the exhaled gas so as to discharge concentrated acetone gas molecules, and the front end of the cold hydrazine preconcentration device is provided with a gas blowing port;

the Herriott gas pool is a closed cavity, two ends of the cavity are respectively provided with a high-reflectivity concave mirror with a light hole, the side wall of the cavity is provided with a gas inlet, a gas outlet, a pressure monitoring port and a pressure control port, the gas inlet is communicated with the cold hydrazine preconcentration device, the gas inlet and the gas outlet are respectively provided with a one-way valve, the gas outlet and the pressure control port are respectively provided with a vacuum pump, and the pressure monitoring port is provided with a gas pressure sensor;

two vertical cavity surface emitting laser diodes, which are both arranged on the left side of the Herriott gas pool, are controlled by a laser driver and generate laser with central wavelengths of 1579.57nm and 1669.73nm respectively, and two beams of laser can be simultaneously emitted into the Herriott gas pool;

the two photoelectric detectors are arranged on the right side of the Herriott gas pool and are used for respectively detecting the optical signal intensity of the corresponding laser after the laser penetrates through the Herriott gas pool;

the signal processing system is used for calculating the change conditions of the carbon dioxide and acetone concentrations in the Herriott gas pool along with the time according to the detected light signal intensity change, and distinguishing alveolar gas and dead space gas in real time according to the carbon dioxide concentration information so as to respectively obtain the acetone gas concentrations corresponding to the alveolar gas and the dead space gas;

and the control system is used for controlling the corresponding vacuum pump to exhaust the gas in the Herriott gas pool.

2. The system for detecting endogenous acetone in exhaled air according to claim 1, wherein the temperature in the cold hydrazine preconcentration device is-30 ℃, and the blowing port is provided with an HDPE blowing nozzle and a filter.

3. The system of claim 1, wherein the Herriott cell is a cylindrical stainless steel chamber with a diameter of 4cm and a length of 20cm, and a wedge window is disposed between the VCSEL and the Herriott cell.

4. The system of claim 1, wherein the vertical cavity surface emitting laser diode for carbon dioxide detection has an output wavelength tunable within 1578 ~ 1583nm, the vertical cavity surface emitting laser diode for acetone gas detection has a wavelength tunable within 1667 ~ 1673nm, the operating current of each vertical cavity surface emitting laser diode is less than 10mA, and the power of each vertical cavity surface emitting laser diode is no more than 10 mw.

5. The system for detecting endogenous acetone in exhaled breath according to claim 1, wherein the optical path of the two laser beams can reach 20m after the two laser beams are continuously reflected between the two high-reflectivity concave mirrors of the herriott gas cell respectively.

6. A method for detecting endogenous acetone in exhaled air is characterized by comprising the following steps:

a. setting the detection system of claim 1 ~ 5, starting the detection system, pumping the Herriott gas pool to vacuum of-50 kPa by the control system, leading the lung gas into the cold hydrazine preconcentration device by the subject through the air blowing port, and leading the gas into the Herriott gas pool after the moisture interference of the gas is removed by the cold hydrazine preconcentration device;

b. the laser driver drives the two vertical cavity surface emitting laser diodes to respectively generate and emit light beams of sawtooth wave signals, the sawtooth wave signals are loaded with sine waves, the two light beams respectively focus on corresponding photoelectric detectors after passing through the Herriott cell, and the photoelectric detectors transmit the obtained signals to the signal processing system for analysis and processing;

c. the signal processing system extracts the amplitude of the second harmonic signal through the phase-locked amplifier, calculates to obtain oscillograms of the carbon dioxide and acetone concentrations in the gas along with the change of time, and automatically judges alveolar gas and dead space gas according to the oscillogram of the carbon dioxide so as to obtain the acetone gas concentrations corresponding to the alveolar gas and the dead space gas respectively;

d. and the control system controls the corresponding vacuum pump to discharge the gas and carry out measurement in the next period.

7. The method according to claim 6, wherein the amplitude of the second harmonic generated after the nitrogen is filled in the Herriott gas cell is measured before the measurement, and the absorption of nitrogen is calculated as background subtraction.

8. The method according to claim 6, wherein during the measurement, the pressure and temperature in the Herriott gas cell are monitored and maintained at preset target values.

Technical Field

The invention relates to the technical field of gas detection, in particular to a system and a method for detecting endogenous acetone in exhaled gas.

Background

The exchange of certain metabolites and chemicals of body or blood flow between the blood circulation system and the pulmonary circulation system in the alveolus leads to the reflection of the metabolic function and disease state of human body by the components and concentration of exhaled air, and the measurement of volatile chemicals (VOCs) in the exhaled air of human body is a highly potential noninvasive detection technology. Acetone gas is the marked VOCs gas exhaled by the diabetic, the exhaled content of healthy people is approximately 0.3-0.9ppm, the content of acetone gas exhaled by the diabetic is generally more than 1.8ppm, and analysis of the concentration of acetone gas exhaled by a human body is a novel method for realizing rapid diagnosis of diabetes. This new approach is suitable for screening of premonitory patients in a healthy population and is therefore receiving increasing attention. However, the concentration of characteristic VOCs in exhaled air is generally in the ppm level and below, the gas composition is complex and many hundreds, stable molecules and free radicals exist, meanwhile, the interference of environmental gas is large, the measurement accuracy is affected, and the interference molecules are difficult to distinguish by the currently common laser spectroscopy. In addition, the content of disease markers is extremely low, the types of the disease markers are multiple, and the development of a detection method with high sensitivity, strong specificity and high signal-to-noise ratio is urgently needed.

Disclosure of Invention

The invention aims to provide a detection system for endogenous acetone in exhaled air, which aims to solve the problems of difficult spectral feature identification, low detection sensitivity and long response time of the conventional device.

The invention also aims to provide a method for detecting endogenous acetone in exhaled air.

One of the purposes of the invention is realized by the following technical scheme: a system for detecting endogenous acetone in exhaled breath, comprising:

the cold hydrazine preconcentration device is used for removing moisture in the exhaled gas so as to discharge concentrated acetone gas molecules, and the front end of the cold hydrazine preconcentration device is provided with a gas blowing port;

the Herriott gas pool is a closed cavity, two ends of the cavity are respectively provided with a high-reflectivity concave mirror with a light hole, the side wall of the cavity is provided with a gas inlet, a gas outlet, a pressure monitoring port and a pressure control port, the gas inlet is communicated with the cold hydrazine preconcentration device, the gas inlet and the gas outlet are respectively provided with a one-way valve, the gas outlet and the pressure control port are respectively provided with a vacuum pump, and the pressure monitoring port is provided with a gas pressure sensor;

two vertical cavity surface emitting laser diodes, which are both arranged on the left side of the Herriott gas pool, are controlled by a laser driver and generate laser with central wavelengths of 1579.57nm and 1669.73nm respectively, and two beams of laser can be simultaneously emitted into the Herriott gas pool;

the two photoelectric detectors are arranged on the right side of the Herriott gas pool and are used for respectively detecting the optical signal intensity of the corresponding laser after the laser penetrates through the Herriott gas pool;

the signal processing system is used for calculating the change conditions of the carbon dioxide and acetone concentrations in the Herriott gas pool along with the time according to the detected light signal intensity change, and distinguishing alveolar gas and dead space gas in real time according to the carbon dioxide concentration information so as to respectively obtain the acetone gas concentrations corresponding to the alveolar gas and the dead space gas;

and the control system is used for controlling the corresponding vacuum pump to exhaust the gas in the Herriott gas pool.

The temperature in the cold hydrazine preconcentration device is-30 ℃, and an HDPE blow nozzle and a filter are arranged at the air blowing opening.

The Herriott gas pool is a cylindrical stainless steel cavity with the diameter of 4cm and the length of 20cm, and a wedge-shaped window is arranged between the vertical cavity surface emitting laser diode and the Herriott gas pool.

The output wavelength of the vertical cavity surface emitting laser diode for detecting carbon dioxide can be tuned within 1578-1583 nm, the wavelength of the vertical cavity surface emitting laser diode for detecting acetone gas can be tuned within 1667-1673 nm, the working current of the vertical cavity surface emitting laser diode is less than 10mA, and the power of the vertical cavity surface emitting laser diode is not more than 10 mw.

After two beams of laser are continuously reflected between two concave mirrors with high reflectivity of a Herriott gas cell, the optical path can reach 20 m.

The second purpose of the invention is realized by the following steps: a method for detecting endogenous acetone in exhaled air comprises the following steps:

a. setting the detection system; starting the detection system, pumping the Herriott gas pool to vacuum pressure of-50 kPa by the control system, enabling a subject to inhale the lung gas into a cold hydrazine preconcentration device through a gas blowing port, and enabling the gas to enter the Herriott gas pool after moisture interference of the gas is removed by the cold hydrazine preconcentration device;

b. the laser driver drives the two vertical cavity surface emitting laser diodes to respectively generate and emit light beams of sawtooth wave signals, the sawtooth wave signals are loaded with sine waves, the two light beams respectively focus on corresponding photoelectric detectors after passing through the Herriott cell, and the photoelectric detectors transmit the obtained signals to the signal processing system for analysis and processing;

c. the signal processing system extracts the amplitude of the second harmonic signal through the phase-locked amplifier, calculates to obtain oscillograms of the carbon dioxide and acetone concentrations in the gas along with the change of time, and automatically judges alveolar gas and dead space gas according to the oscillogram of the carbon dioxide so as to obtain the acetone gas concentrations corresponding to the alveolar gas and the dead space gas respectively;

d. and the control system controls the corresponding vacuum pump to discharge the gas and carry out measurement in the next period.

Before measurement, the amplitude of the second harmonic generated after nitrogen is filled in the Herriott gas pool is measured, and the absorption of the nitrogen is calculated to be used as background subtraction.

During the measurement, the pressure and temperature in the herriott cell are monitored and maintained at preset target values.

Compared with the prior art, the invention has the following beneficial effects:

(1) the concentration of carbon dioxide in alveolar gas is two to three times higher than that of expired gas sample mixed with dead space gas, and the system utilizes a near-infrared tunable absorption spectrum measurement system to analyze and obtain carbon dioxide concentration information according to second harmonic spectrum and CO₂The change of the gas content realizes the on-line real-time detection of dead space gas and alveolar gas, and canThe method can accurately judge different stages of the gas exhaled by the testee, can distinguish the acetone content in different respiratory stages, and is favorable for improving the measurement precision of characteristic molecules.

(2) The online accurate measurement of the acetone gas content is realized in the near infrared region by a tunable semiconductor absorption spectrum technology.

(3) The second harmonic technology in the long optical path wavelength modulation can realize the measurement precision of the mu s level response time and the ppb level.

(4) Through the cold hydrazine concentration system, the interference of a large amount of water vapor is eliminated, the concentration of trace characteristic gas molecules to be detected is improved, and the detection sensitivity is further improved.

(5) The tunable semiconductor absorption spectrum technology is combined with a vertical cavity surface emitting laser diode with low cost and low power, has the advantages of high signal-to-noise ratio, low cost, small volume, low power consumption, quick response and the like, and has the potential of being developed into portable instruments.

Drawings

FIG. 1 is a flow chart of the detection method of the present invention.

Fig. 2 is a schematic structural diagram of a human body exhaled acetone measuring system based on a tunable semiconductor absorption spectrum technology.

Fig. 3 is a waveform diagram of the variation of carbon dioxide concentration in the normal respiratory cycle of a human body.

FIG. 4 is a schematic view of the beam path inside the Herriott gas cell.

FIG. 5 is a distribution diagram of two concave mirror spots of a Herriott gas cell. The inner ring is a laser spot with the central wavelength of 1669.73nm, the outer ring is a laser spot with the central wavelength of 1579.57nm, and in fig. 5, 1 and 2 are light inlet holes, and 3 and 4 are light outlet holes.

FIG. 6 is a schematic diagram of a sawtooth wave received by the photodetector and a processed second harmonic.

In fig. 2: 1. a Herriott gas cell; 2. a high-reflectivity concave mirror; 3. an air blowing port; 4. an air outlet; 5. a pressure control port; 6. a pressure monitoring port; 7. a first laser diode; 8. an optical isolator; 9. a first photodetector; 10. a control system; 11. a cold hydrazine preconcentration device; 12. a laser driver; 13. a signal processing system; 14. a second laser diode; 15. a second photodetector; 16. an air inlet.

Detailed Description