Portable gas analyser Cosmed K4b² compared to a laboratory based mass spectrometer system

Aim. The purpose of this study was to systematically test the accuracy of an automated, portable, gas analysis system, the Cosmed K4b² with a laboratory based mass spectrometer system, the Morgan EX670 across a number of gas and ventilation parameters. Methods. Eight subjects (mean±SE) age, 23.7±1.1 y, height, 1.78±0.01 m, mass, 74.4±2.1 kg performed a V̇O_2max test and a submaximal exercise test at 150, 200, 250 and 300 Watts (W), on an SRM cycle ergometer. The Morgan EX670 system and the K4b² were randomly connected in series, using the same breath for the calculation of gas and ventilatory parameters. Results. The K4b ² system reads significantly higher than the Morgan EX 670 for both V̇O₂ and V̇CO₂ at 250 (V̇O₂/ V̇CO₂: p<0.05, p<0.002), and 300 W (V̇O ₂/V̇CO₂: p<0.002, p<0.005). Unsystematic bias between the 2 analysers varies between 1% and 16% and systematic bias between 3% and 8%. Conclusion. There are some significant unsystematic and systematic differences between these 2 systems and laboratories should endeavour to utilise either one or the other piece of equipment to test their subjects.