PRECISION AND ACCURACY IN A METABOLIC MONITOR FOR INDIRECT CALORIMETRY

Objective: To determine within-machine and between-machine precision ( reproducibility) and accuracy, of the Deltatrac Mk 1 Metabolic Monitor . Design: Within-machine and between-machine comparison for gas exchan ge (VO2 and VCO2), respiratory quotient (RQ) and energy expenditure (E E). Subjects: 3 Deltatrac Mk 1 Metabolic Monitors. Methods: Within-mac hine and between-machine reproducibility were assessed by five success ive 10 min gas infusion tests in each machine. Accuracy was assessed b y measuring independently the gas content of the infusion mixture. The Deltatrac flowmeters were evaluated by further infusion tests. Result s: Within-study reproducibility was < 1 ml/min for VCO2, < 2.5 ml/min for VO2, <5 kcal/d for EE and < 0.01 for RQ. Between-study reproducibi lity was < 0.2% for RQ, < 1% for VCO2 and < 2% for VO2 and EE. Between -machine reproducibility was < 0.1% for RQ and < 1% for VO2, VCO2 and EE. Accuracy in all three machines was within 3% for VO2, VCO2 and EE, and within 0.2% for RQ. Conclusions: The Deltatrac Mk 1 is a very pre cise metabolic monitor, and is accurate within 3% for gas exchange and EE. RQ is measured with greatest reproducibility and accuracy (within 0.2%), making the monitor particularly suitable for studies of substr ate utilisation.