A laboratory investigation of two new portable gas analysers.

Two new portable infrared gas analysers, the Irina (Drägerwerke, Lübeck, Germany) and the Normac (Datex Instrumentarium Corporation, Helsinki, Finland), were tested and the results compared to those from such established methods as gaschromatography and the Beckman LB-2 (Beckman, USA) infrared gas analyser using exactly defined gas mixtures from a vaporizer developed in our laboratory. The analysers were evaluated for their accuracy and precision, noise, zero stability, gain stability and the impact of flow, over-pressure, carrier gas and humidity. All three analysers showed good accuracy and precision. The noise level was acceptable except in the older version of the Normac, but this error has now been corrected by the manufacturer. Zero and gain stability are very good; gas flow and over-pressure do not affect the measurement. The influence of carrier gases and humidity is negligible except for the strong N2O effect on the Beckman. We conclude that this new generation of highly sophisticated and reliable but handy analysers will meet the clinical demands.