Comparison between the Datex-Ohmeda M-COVX metabolic monitor and the Deltatrac II in mechanically ventilated patients

Abstract

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 FiO(2) 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 (Deltatrac(before), M-COVX, Deltatrac(after)). Each measurement consisted of five consecutive 1-min readings of VO(2) and VCO(2). We compared the Deltatrac(before) with the Deltatrac(after) and the mean of the Deltatrac with the M-COVX. There was no clinically significant bias between the two monitors for VO(2) or VCO(2) but the limits of agreement (LOA) were wide (bias +/-95% LOA: VCO(2) -13 +/- 30 ml/min, -8 +/- 36 ml/min, 7 +/- 50 ml/min; VO(2) -7 +/- 50 ml/min, -5 +/- 56 ml/min, 6 +/- 64 ml/min, at FiO(2) 0.3, 0.5, and 0.7, respectively). The Deltatrac before and after measurements displayed good agreement for VCO(2) but poorer agreement for VO(2) (bias +/- 95% LOA: VCO(2) 0 +/- 18 ml/min, -6 +/- 16 ml/min, -1 +/- 12 ml/min; VO(2) 2 +/- 12 ml/min, 3 +/- 38 ml/min, 10 +/- 42 ml/min, at FiO(2) 0.3, 0.5, and 0.7, respectively). Using within-patient standard deviation as a measure of reproducibility suggested that for VO(2) the M-COVX performed better than the Deltatrac at high FiO(2), and for VCO(2) Deltatrac was better at lower FiO(2).

Conclusions: The M-COVX is a suitable integrated device for measuring metabolic gas exchange in ventilated patients.