Accurate Detection Of EtCO₂ Based On NDIR

In clinical monitoring, end tidal carbon dioxide (EtCO2) is a very important parameter,it can also reflect the patient’s pulmonary ventilation function and the patient’s blood circulation function and pulmonary blood flow status. Because of the advantages of noninvasive and continuous monitoring of EtCO2, it has a very wide range of applications in clinical medicine in recent years. The temperature, moisture and atmospheric pressure of the patients can affect the accuracy of EtCO2 detection. At present,EtCO2 testing equipment is mainly produced by foreign manufacturers, it is less likely to be seen in China.Therefore, our independent research and development of high precision EtCO2 detection system should have a great market potential.EtCO2 detection system in this paper is non dispersive infrared gas detection technology based on (NDIR), and the influence of temperature, water vapor, breath with atmospheric pressure on the EtCO2 concentration test results. This technology based on Lambert-Beer’s law, which is the use of the detector to detect the infrared light attenuation to calculate the concentration of CO2, with high sensitivity, stability and anti-interference ability of the system. Based on the NDIR principle to build a set of intelligent monitoring system for ETCO2 of temperature, humidity, air pressure, CO2 concentration, and the concentration of CO2 was calibrated, the effects of temperature, humidity and air pressure effect on measuring the concentration of CO2.This paper uses CC2530 chip ZigBee wireless transmission system, build the hardware system using ATmegal6A chip, in the part of the hardware system is introduced to realize the function of hardware construction, including the ATmegal6A chip circuit, voltage conversion circuit, voltage regulator circuit and liquid crystal display module design.CO2 in order to improve the accuracy of test results, this paper studied the effects of temperature, humidity and pressure measurement of exhaled carbon dioxide concentration measurement, and the temperature and humidity sensors, carbon dioxide sensors were calibrated in advance, improve the measurement accuracy of the sensor.In the software part, it mainly introduces the software of the upper computer and the lower computer.PC software is written using LabVIEW. The lower computer program is mainly developed by IAR. In this paper, a more intuitive and convenient operation interface of the upper computer is designed, which is convenient for the operation of medical staff. It has four functions of parameter information collection, information display, data processing and data storage. The software part of this paper is the simple introduction to the development platform of the host computer, and then the data acquisition, information display function, data processing and storage function module are mainly introduced.In order to improve the accuracy of EtCO2 measurement, the calibration model of temperature, humidity and gas pressure on CO2 measurement was established, and the data were processed. The calibration model was established with the simulation data, and the calibration model was verified by the data of the validation set. The results showed that the calibration model improved the measurement accuracy of EtCO2.