Abstract
PurposeThis study aimed to examine the validity, reliability and minimum detectable change (MDC) of the Cosmed K5 in breath by breath (BxB) mode, against VacuMed metabolic simulator. Intra and inter-units reliability was also assessed.MethodsFourteen metabolic rates (from 0.9 to 4 L.min-1) were reproduced by a VacuMed system and pulmonary ventilation (VE), oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured by two different K5 units. Validity was assessed by ordinary least products (OLP) regression analysis, Bland-Altman plots, intraclass correlation coefficients (ICC), mean percentage differences, technical errors (TE) and MDC for VE, VO2, and VCO2. Intra- and inter-K5 reliability was evaluated by absolute percentage differences between measurements (MAPE), ICCs, TE, and MDC.ResultsValidity analysis from OLP regression data and Bland- Altman plots indicated high agreement between K5 and simulator. ICC values were excellent for all variables (>0.99). Mean percentage differences in VE (-0.50%, p = 0.11), VO2 (-0.04%, p = 0.80), and VCO2 (-1.03%, p = 0.09) showed no significant bias. The technical error (TE) ranged from 0.73% to 1.34% (VE and VCO2 respectively). MDC were lower than 4% (VE = 2.0%, VO2 = 3.8%, VCO2 = 3.7%). The intra and inter K5 reliability assessment reveled excellent ICCs (>0.99), MAPE <2% (no significant differences between trials), TE < or around 1%, MDC <or around 3%.ConclusionsK5 in BxB mode is a valid and reliable system for metabolic measurements. This is the first study assessing the MDC accounting only for technical variability reporting intra- and inter-units MDCs <3.3%.
Highlights
The use of automated metabolic systems to measure oxygen consumption (VO2) and carbon dioxide production (VCO2) has become an essential tool for the analysis of physical performance and clinical diagnoses
intra-class correlation coefficient (ICC) values were excellent for all variables (>0.99)
minimum detectable change (MDC) were lower than 4% (VE = 2.0%, VO2 = 3.8%, VCO2 = 3.7%)
Summary
The use of automated metabolic systems to measure oxygen consumption (VO2) and carbon dioxide production (VCO2) has become an essential tool for the analysis of physical performance and clinical diagnoses. This option, called ‘IntelliMET’ (Intelligent Dual Metabolic Sampling Technology), allows users to select either the dynamic mixing chamber or the BxB sampling modality to measure either steady-state metabolic rates or oxygen kinetics during transients This technology is supported by a series of significant hardware and firmware/software updates that aim to improve the reliability of its’ measures: 1) a dynamic mixing chamber that uses a constant flow pump; 2) a 4th generation opto-electronic reader and high performance turbine flowmeter with 0.08–16 L/s flow range; 3) an external scrubber to obtain real zero carbon dioxide and allow for more accurate gas calibration; 4) an external ambient temperature sensor for the calculation of the inspiratory BTPS factor and a capacitive ambient humidity and piezo-resistive pressure sensors inside the K5 unit for the calculation of the expiratory BTPS and STPD factors. Additional functions have been included to improve flexibility and durability of the product such as a 3.5@ TFT back-lit LCD touch-screen; a 4h Li-ion “smart battery”, an integrated 10 Hz GPS receiver for navigation/motion, integrated ANT+ technology for optional wireless sensors, a weatherproof case (IP54 standard), a standard or long-range Bluetooth 2.1 and an SDHC card for additional data storage [2]
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