Online mass-spectrometric monitoring of O2 and CO2 during anesthesia

It is suggested to determine the breathing cycle duration during anesthesia by the online method based on synchronous mass-spectrometric monitoring of the concentrations of an inert gas (not involved in metabolism), CO₂, and O₂. Comparative results of determining the temporal boundaries of the breathing cycle using the proposed method with argon (Ar) and krypton (Kr) are presented. The concentrations of CO₂, O₂, and Ar (or Kr) were measured using an electron-impact ionization mass spectrometer. The gas mixture was sampled directly from the breathing circuit of an anesthesia machine during low-flow balanced inhalation anesthesia. The obtained results show the possibility of using mass-spectrometric monitoring of the CO₂/O₂ metabolism in order to assess online the adequacy of anesthesia with respect to surgical invasion during anesthesia.