Studies with the "Severinghaus" Pco2 electrode II: CO2 measurement using a single control analyser

A simple, single calibration point, single control Pco2 analyser is described. Results are presented to show that such an analyser will provide extremely accurate and reproducible results over a limited range around the calibration point, and this technique has been applied to the measurement of the apparent blood-gas and water-gas difference for a Pco2 electrode. The accuracy and working range of this simple system has been compared with a two-calibration-point, two-control analyser similar to commercial systems and results are presented to show that the more complicated system, although accurate over a wider range of Pco2, did not produce accurate results when the Pco2 of test samples lay outside the calibration range. Reasons are presented to explain this unexpected behaviour.