Fast track articleA new modulation technique and compensation algorithm for mainstream CO2 capnography

Carbon dioxide, as a metabolic product of human, is correlated with a patient's perfusion and ventilation. In medicine, the end-tidal carbon dioxide partial pressure refers to the measurement of exhaled carbon dioxide, and end-tidal carbon dioxide partial pressure monitoring has become an important tool in clinical monitoring. However, there are some aspects needed to be improved. So, the low-frequency modulation is used to reliably acquire the respiration information. The measurement method is improved based on the Lambert-Beer Law. Also, we compensate the initial absorbance because of the light absorbance of the sensor at different wavelengths. The influence of the temperature change is analyzed on the measurement. All of these methods make the end-tidal carbon dioxide partial pressure accurate and convenient.