Describe the principles of measurement of end-tidal CO2, including the sources of
Candidates were expected to be detail the principles required to measure carbon dioxide in
expired gas. This would involve some comment on ways to sample end tidal gas (in line vs side
stream) and also ways to measure carbon dioxide. It was expected candidates could provide a
detailed description of infrared analysis including the apparatus design and principles such as
the asymmetric nature of CO2 as a polyatomic gas allowing absorption if infrared radiation with
some discussion of response times and equipment design. It was expected these principles
would be related to the potential errors (e.g. other gases, collision broadening).