Measurement of gas concentrations

Gas analysis is one of the minimum standards of monitoring for any patient undergoing anaesthetic intervention. Side stream analysers are commonly employed to allow for measurement of gas concentrations. The systems used to measure oxygen (O2) concentration include the paramagnetic analyser, the Clark electrode and the fuel cell. Infrared absorption spectroscopy is used to measure carbon dioxide (CO2), nitrous oxide (N2O), and volatile anaesthetic agents in gaseous form. Refractometry, piezoelectric absorption, Raman scattering, and mass spectrometry may also be used. The Severinghaus electrode is used to measure CO2 concentration in solution. This article will provide an overview of the techniques used for gas analysis and their associated potential sources of error.