History of respiratory gas monitoring in anesthesia

Abstract

Before 1950, anesthetists assessed adequacy of ventilation by watching or rarely measuring gas volume exchange or chest movements. About 1950, infrared (IR) light absorption by CO2 was used to continuously measure expired CO2, a first real monitor of respiration. It was dubbed capnometry, and remains the basis of all respiratory gas monitors. Gaseous oxygen was first monitored in anesthetic circuits using a polarographic oxygen electrode, made available about 1960. Mass spectrometers that could continuously measure O2, CO2, N2O and anesthetic gases were rarely used until 1975 when methods were introduced to use one mass spectrometer to sequentially measure gases sampled through long catheters from many patients. In the late 1980s, infra red detectors of CO2 and anesthetic vapors were combined with polarographic O2 electrodes to make the modern operating room gas monitoring devices.