Environmental Factors Affecting the Performance of Infrared CO2 Analyzer and the Estimation of Alveolar CO2 Tension

摘要

Theoretical equations were derived from known physico-chemical laws to determine the effects of room temperature and barometric pressure on the performance of the infrared type of CO2 analyzer. They were first tested experimentally and then against empirical equations derived from the Godart nomogram. These equations were found to be valid and useful in the estimation of the fractional concentration of CO2 of gas mixtures under various environmental conditions. Minimal gas temperature recorded with a thermistor probe at the inlet of the analyzer was used to estimate the water vapor pressure of gas samples in the analyzer chamber. This method was experimentally tested to be valid in estimating CO2 fractional concentrations of heated wet gas mixtures. It was used to estimate the alveolar CO2 tension of human subjects with various end-tidal sampling methods. Methods used by others with this type of analyzer were discussed. (Author)