Comparison of the Cosmed K4b(2) Portable Metabolic System in Measuring Steady-State Walking Energy Expenditure

BACKGROUND AND AIMS: Recent introduction of the Cosmed K4b(2) portable metabolic analyzer allows measurement of oxygen consumption outside of a laboratory setting in more typical clinical or household environments and thus may be used to obtain information on the metabolic costs of specific daily life activities. The purpose of this study was to assess the accuracy of the Cosmed K4b(2) portable metabolic analyzer against a traditional, stationary gas exchange system (the Medgraphics D-Series) during steady-state, submaximal walking exercise. METHODS: Nineteen men and women (9 women, 10 men) with an average age of 39.8 years (±13.8) completed two 400 meter walk tests using the two systems at a constant, self-selected pace on a treadmill. Average oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) from each walk were compared. RESULTS: Intraclass Correlation Coefficient (ICC) and Pearson correlation coefficients between the two systems for weight indexed VO(2) (ml/kg/min), total VO(2) (ml/min), and VCO(2) (ml/min) ranged from 0.93 to 0.97. Comparison of the average values obtained using the Cosmed K4b(2) and Medgraphics systems using paired t-tests indicate no significant difference for VO(2) (ml/kg/min) overall (p = 0.25), or when stratified by sex (p = 0.21 women, p = 0.69 men). The mean difference between analyzers was – 0.296 ml/kg/min (±0.26). Results were not significantly different for VO(2) (ml/min) or VCO(2) (ml/min) within the study population (p = 0.16 and p = 0.08, respectively), or when stratified by sex (VO(2): p = 0.51 women, p = 0.16 men; VCO(2): p = .11 women, p = 0.53 men). CONCLUSION: The Cosmed K4b(2) portable metabolic analyzer provides measures of VO(2) and VCO(2) during steady-state, submaximal exercise similar to a traditional, stationary gas exchange system.