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.


METHODS
Within-machine and between-machine comparison for gas exchange (VO2 and VCO2), respiratory quotient (RQ) and energy expenditure (EE).


METHODS
3 Deltatrac Mk 1 Metabolic Monitors.


METHODS
Within-machine and between-machine reproducibility were assessed by five successive 10 min gas infusion tests in each machine. Accuracy was assessed by measuring independently the gas content of the infusion mixture. The Deltatrac flowmeters were evaluated by further infusion tests.


RESULTS
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 reproducibility 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 precise 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 substrate utilisation.
Dunn Clinical Nutrition Centre, Cambridge.
J C
JC
Wells
N J
NJ
Fuller
D000328:Adult; D001481:Basal Metabolism; D002153:Calorimetry, Indirect / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data; D004734:Energy Metabolism; D006801:Humans; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity