Inter- and intra-unit reliability of the COSMED K5: Implications for multicentric and longitudinal testing

• Published in: PloS one Vol. 15; no. 10; p. e0241079
• Main Authors: Winkert, Kay, Kamnig, Rupert, Kirsten, Johannes, Steinacker, Jürgen M, Treff, Gunnar
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.10.2020; Public Library of Science (PLoS)
• Subjects: Accuracy; Adult; Athletes; Biological variation; Biology and Life Sciences; Blood-brain barrier; Breath Tests - methods; Cardiorespiratory Fitness - physiology; Correlation coefficient; Correlation coefficients; Engineering and Technology; Evaluation; Exercise Test - methods; Exercise Test - standards; Exercise Test - statistics & numerical data; Exports; Humans; Humidity; Laboratories; Longitudinal Studies; Male; Medicine; Medicine and Health Sciences; Metabolism; Multicenter Studies as Topic; Observer Variation; Patient monitoring equipment; Physical Sciences; Practice Guidelines as Topic; Rehabilitation; Reliability analysis; Reliability engineering; Reproducibility of Results; Research and Analysis Methods; Respiration; Simulation; Stroke; Structural reliability; Validity; Ventilation; Warm up (exercise); Germany; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0241079

To 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. Identical 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. In 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 [Formula: see text] and RER were significant (p < 0.05) at each step. Two structurally identical K5-units demonstrated accurate RELINTRA with TE < 2.0% and similar RELINTER during metabolic simulation. During biological testing, inter-unit differences for [Formula: see text] 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.