Comparison of 2 Portable Respiratory Gas Analysers

Abstract

The aim of this study was to compare respiratory measures taken simultaneously using the Cosmed K4b² and Cortex Metamax II portable metabolic systems. 10 trained male cyclists performed a graded exercise cycle test to exhaustion (40w.3 min^− 1) under standardized conditions. The measured respiratory variables were significantly correlated between both devices: r=0.97 and 0.98 (n=10, p<0.01) for oxygen uptake ( V˙O₂) and ventilation (V_E), respectively. Further Bland and Altman plots revealed a good level of agreement for measures of V˙O₂ expressed in mL.min^− 1 [− 670 to 486] (mean bias of − 91.7, i. e., − 3.1%) or in mL.min^− 1.kg^− 1 [− 7.3 to 9.0] (mean bias of 0.85, i. e., 2.3%) and V_E [− 23.1 to 18.2] (L.min^− 1, mean bias of − 2.4, i. e. − 4.1%). However, poor agreement was found for measures of carbon dioxide (VCO₂, mL.min^− 1) [− 280 to 1 394] (mean bias of 671 i.e., 20.3%). VCO₂ at maximal exercise intensity was also significantly (p<0.01) greater in the Cortex compared to the Cosmed system. The higher measured CO₂ concentrations led to significantly (p<0.01) higher calculated respiratory exchange ratio (RER) values with the Cortex device. In conclusion, there was satisfactory agreement between the Cosmed K4b² and Cortex Metamax II systems for most respiratory measures; however there was a poor level of agreement between VCO₂ and calculated RER measurements between the 2 systems.

Key words

respiratory gas exchanges - exercise - breath-by-breath gas analysers - comparison

• References

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