Reliability of gas exchange measurements from two different spiroergometrysystems

Reliability of two different spiroergometric systems was investigated by co mparing gas exchange measurements from two consecutive identical bicycle er gometer ramp exercise tests which were conducted after an initial habituati on trial. Twenty-three healthy subjects (age: 25 +/- 5 years; weight: 71 +/ - 10 kg; peak oxygen uptake: 55 +/- 9 ml x min(-1) x kg(-1)) took part in t he study. One apparatus was a portable mixing chamber system (MetaMax I, Co rtex, Leipzig, Germany), the other one a stationary spiroergometric device measuring in the breath-by-breath mode (MetaLyzer 3B, Cortex). There were n o relevant systematic changes in gas exchange measurements and heart rate f rom test 1 to test 2. Intra-class reliability coefficients were 0.984 (oxyg en uptake = VO2), 0.977 (carbon dioxide Output = VCO2), and 0.973 (minute v entilation = V-E) for the MetaMax I, and 0.969 (VO2), 0.964 (VCO2), and 0.9 53 (V-E) for the MetaLyzer 3B. Bland-Altman plots revealed a slightly small er variability of MetaLyzer 3B measurements compared to those of MetaMax I. It is concluded that the spiroergometric devices MetaMax I and MetaLyzer 3 B represent reliable instruments for exercise testing in sports medical rou tine and research. This is important to decide if longitudinal changes in g as exchange measurements represent clinically meaningful differences in per formance or merely inconsistencies of the measuring tool.