Accurate and stable continuous monitoring module by mainstream capnography.

End-tidal partial pressure of [Formula: see text] is an important index in clinical monitoring. Medical mainstream capnography has become widely used, but there are still limitations in accuracy and stability. A type of mainstream capnometer based on the principle of non-dispersive infrared was designed. This capnometer inhibits signal drift by using electric modulation and thus ensures the accuracy of long-term CO2 monitoring. Statistical methods are used to find the best setting for sampling respiratory signals and improving precision. Several digital filtering techniques are used to process various interferences and improve capnogram quality. Clinical tests and targeted experiments show this mainstream capnometer can accurately monitor respiratory CO2 concentrations, especially at the end-tidal peak point. This capnometer also shows high accuracy and stability in long-term continuous monitoring.