Effect of FiO 2 in the measurement of VO 2 and VCO 2 using the E-COXV metabolic monitor.

OBJECTIVE: We evaluated the effect of changes in FiO2 on the bias and accuracy of the determination of oxygen consumption (V˙O2 ) and carbon dioxide production (V˙CO2 ) using the E-COVX monitor in patients with mechanical ventilation.

DESIGN: Descriptive of concordance.

SETTING: Intensive Care Unit.

PATIENTS OR PARTICIPANTS: Patients with mechanical ventilation.

INTERVENTIONS: We measured V˙O2 and V˙CO2 using the E-COVX monitor. Values recorded were the average in 5min. Two groups of 30 patients. We analyzed: 1) the reproducibility in the measurement of V˙O2 and V˙CO2 at FiO2 0.4, and 2) the effect of the changes in FiO2 on the measurement of V˙O2 and V˙CO2 . Statistical analysis was performed using Bland and Altman test.

VARIABLES OF MAIN INTEREST: Bias and accuracy.

RESULTS: 1) FiO2 0.4 reproducibility: The bias in the measurement of V˙O2 and V˙CO2 was 1.6 and 2.1mL/min, respectively, and accuracy was 9.7 to -8.3% and 7.2 to -5.2%, respectively, and 2) effect of FiO2 on V˙O2 : The bias of V˙O2 measured at FiO2 0.4 and 0.6 was -4.0mL/min and FiO2 0.4 and 0.8 was 5.2mL/min. Accuracy between FiO2 0.4 and 0.6 was 11.9 to -14.1%, and between FiO2 0.4 and 0.8 was 43.9 to -39.7%.

CONCLUSIONS: The E-COVX monitor evaluates V˙O2 and V˙CO2 in critical patients with mechanical ventilation with a clinically acceptable accuracy until FiO2 0.6.