Accuracy of oxygen consumption and carbon dioxide elimination measurements in 2 breath-by-breath devices

BACKGROUND: Although accurate quantification of oxygen consumption (V˙ O2) and carbon dioxide elimination (V˙_CO2) provides important insights into a patient’s nutritional and hemodynamic status, few devices exist to accurately measure these parameters in children. Therefore, we assessed the accuracy and agreement of 2 devices currently on the market using a pediatric in vitro model of gas exchange. METHODS: We utilized a Huszczuk simulation model, which simulates oxygen consumption and carbon dioxide production using gas dilution, to examine the accuracy of two FDA-cleared respiratory modules (E-COVX and E-sCAiOVX-00). V˙ O2 and V˙_CO2 were set at 20, 40, 60, and 100 mL/min, ranges typical for infant and pediatric patients. Bland-Altman analysis was used to calculate the bias and limits of agreement of each device relative to simulated values for V˙ O2 and V˙_CO2. RESULTS: The E-COVX mean percentage bias (limits of agreement) was =26.3% (=36.1 to =16.6%) and =39.3% (=47.5 to =31.1%) for V˙ O2 and V˙_CO2, respectively. The mean bias (limits of agreement) for the E-aCAiOVX-00 was =0.5% (=13.3 to 12.3%) and =6.0% (=13.8 to 1.7%) for V˙ O2 and V˙_CO2, respectively. CONCLUSIONS: The E-COVX demonstrated bias and limits of agreement that were not clinically acceptable; therefore, application of this module to pediatric patients would not be recommended. The new module, E-sCAiOVX, demonstrated acceptable bias and limits of agreement for the V˙ O2 and V˙_CO2 in the range 40–100 mL/min (which corresponds to patients in the range of ∼5–16 kg).