Comparison between the Datex-Ohmeda M-COVX metabolic monitor and the Deltatrac II in mechanically ventilated patients
Objective. To compare the M-COVX and the Deltatrac II metabolic monitors under clinical conditions.
Design. Prospective clinical comparison.
Setting. A general Intensive Care Unit of a university hospital.
Patients. Twenty mechanically ventilated critically ill patients.
Interventions. The monitors were compared at FiO2 0.3, 0.5, and 0.7 in each patient where possible.
Measurements and results. Pulmonary gas exchange measurements were recorded using the two monitors sequentially (Deltatracbefore, M-COVX, Deltatracafter). Each measurement consisted of five consecutive 1-min readings of VO2 and VCO2. We compared the Deltatracbefore with the Deltatracafter and the mean of the Deltatrac with the M-COVX. There was no clinically significant bias between the two monitors for VO2 or VCO2 but the limits of agreement (LOA) were wide (bias ±95% LOA: VCO2 –13±30 ml/min, –8±36 ml/min, 7±50 ml/min; VO2 –7±50 ml/min, –5±56 ml/min, 6±64 ml/min, at FiO2 0.3, 0.5, and 0.7, respectively). The Deltatrac before and after measurements displayed good agreement for VCO2 but poorer agreement for VO2 (bias±95% LOA: VCO2 0±18 ml/min, –6±16 ml/min, –1±12 ml/min; VO2 2±12 ml/min, 3±38 ml/min, 10±42 ml/min, at FiO2 0.3, 0.5, and 0.7, respectively). Using within-patient standard deviation as a measure of reproducibility suggested that for VO2 the M-COVX performed better than the Deltatrac at high FiO2, and for VCO2 Deltatrac was better at lower FiO2.
Conclusions. The M-COVX is a suitable integrated device for measuring metabolic gas exchange in ventilated patients.
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