Accuracy of Oxygen Consumption and Carbon Dioxide Elimination Measurements in 2 Breath-by-Breath Devices

Abstract

BACKGROUND:

Although accurate quantification of oxygen consumption (V̇_O2 ) and carbon dioxide elimination (V̇_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). V̇_O2 and V̇_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 V̇_O2 and V̇_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 V̇_O2 and V̇_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 V̇_O2 and V̇_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 V̇_O2 and V̇_CO2 in the range 40–100 mL/min (which corresponds to patients in the range of ∼5–16 kg).