Comparison between two metabolic monitors in the measurement of resting energy expenditure and oxygen consumption in diabetic and non-diabetic ambulatory and hospitalized patients

Objective: The aim of this study was to assess the validity and reliability of the Fitmate metabolic system in measuring the oxygen consumption and resting metabolic rate (RMR) in ambulatory and hospitalized patients. Methods: We conducted a prospective simultaneous clinical comparison. We enrolled 37 patients (19 women and 18 men) for the four groups of the study. Group 1 (n=12) included patients receiving home parenteral nutrition. Group 2 (n=5) included diabetic overweight outpatients with body mass index >30kg/m²; and hemoglobin A_1c>8g/dL. Group 3 (n=10) included hospitalized patients receiving artificial nutrition. Group 4 (n=10) included patients with congenital heart disease, pulmonary hypertension of any etiology, and other heart disease who have had hemodynamic evaluation during catheterization by the adult congenital team. The patients were tested successively during the same session using the Fitmate metabolic system for 15min and the Deltatrac II metabolic monitor for 20min, measuring resting energy expenditure and oxygen consumption. The test was conducted in random order. Results: No significant differences were found between Fit Mate and Deltatrac II for oxygen consumption (238±18 and 240±18mL/min, respectively, P=0.72, r=0.86, mean±SD absolute difference 22.32±16.99mL/min) or RMR (1659±122.34 and 1625±118.4kcal/d, P=0.28, r=0.87, mean±SD absolute difference 152.9±111.95kcal/d). A degree of limit of agreement (403kcal) was observed using the Bland-Altman test. When compared with Harris-Benedict predictive equations, Fitmate was found to be superior in accuracy. Conclusions: These data indicate that the Fitmate using a mask provided a fair evaluation of REE despite a large limit of agreement. It remains a reliable and valid system for measuring oxygen consumption and RMR in nonventilated patients.