Abstract
PurposeTo evaluate the intra-unit (RELINTRA) and inter-unit reliability (RELINTER) of two structurally identical units of the metabolic analyser K5 (COSMED, Rome, Italy) that allows to utilize either breath-by-breath (BBB) or dynamic mixing chamber (DMC) technology.MethodsIdentical flow- and gas-signals were transmitted to both K5s that always operated simultaneously either in BBB- or DMC-mode. To assess RELINTRA and RELINTER, a metabolic simulator was applied to simulate four graded levels of respiration. RELINTRA and RELINTER were expressed as typical error (TE%) and Intraclass Correlation Coefficient (ICC). To assess also inter-unit differences via natural respiratory signals, 12 male athletes performed one incremental bike step test each in BBB- and DMC-mode. Inter-unit differences within biological testing were expressed as percentages.ResultsIn BBB, TE% of RELINTRA ranged 0.30–0.67 vs. RELINTER 0.16–1.39 and ICC ranged 0.57–1.00 vs. 0.09–1.00. In DMC, TE% of RELINTRA ranged 0.38–0.90 vs. RELINTER 0.03–0.86 and ICC ranged 0.22–1.00 vs. 0.52–1.00. Mean inter-unit differences ranged -2.30–2.20% (Cohen’s ds (ds) 0.13–1.52) for BBB- and -0.55–0.61% (ds 0.00–0.65) for DMC-mode, respectively. Inter-unit differences for and RER were significant (p < 0.05) at each step.ConclusionTwo structurally identical K5-units demonstrated accurate RELINTRA with TE < 2.0% and similar RELINTER during metabolic simulation. During biological testing, inter-unit differences for and RER in BBB-mode were higher than 2% with partially large ES in BBB. Hence, the K5 should be allocated personally wherever possible. Otherwise, e.g. in multicenter studies, a decrease in total reliability needs to be considered especially when the BBB-mode is applied.
Highlights
Cardiopulmonary exercise (CPX) testing is frequently used to evaluate fitness in healthy and unhealthy populations in cross-sectional [1] or longitudinal [2] evaluations or studies, as underlined by 3357 hits on the search item “V_ O2max testing” in pubmed within 5 years (Aug. 2020)
Inter-unit differences for V_O2 and RER in BBB-mode were higher than 2% with partially large ES in BBB
As for any scientific method, reliability is an important quality measure for CPX devices and if testing is conducted within one laboratory and only one CPX-unit is applied, the overall variability of one unit between two or more trials is a key quality measure
Summary
Cardiopulmonary exercise (CPX) testing is frequently used to evaluate fitness in healthy and unhealthy populations in cross-sectional [1] or longitudinal [2] evaluations or studies, as underlined by 3357 hits on the search item “V_ O2max testing” in pubmed within 5 years (Aug. 2020). As for any scientific method, reliability is an important quality measure for CPX devices and if testing is conducted within one laboratory and only one CPX-unit is applied, the overall variability of one unit between two or more trials is a key quality measure. This will be called intra-unit reliability (i.e. intra-rater reliability [3]) hereafter. As soon as more than one unit of a particular device is used–be that within one or in multiple labs–the variability between two or more CPX-units needs to be considered, too This will be called inter-unit reliability (i.e. inter-rater reliability [3]) hereafter.
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