Background and Aims: The 2 currently available indirect calorimeters, CCM Express Indirect Calorimeter (MedGraphics, St Paul, MN) and Quark RMR ICU Indirect Calorimeter (COSMED, Rome, Italy), have not been validated against a gold standard in mechanically ventilated patients. Our aim was to do so using a gold-standard, modified Tissot bell-spirometer method in mechanically ventilated patients who were hemodynamically, respiratory, and metabolically stable. Methods: We studied 30 patients undergoing general anesthesia and major gynecological surgery. We measured oxygen consumption (
O2) and resting energy expenditure (REE) in a randomized, sequential, crossover design with double determination of each device. Results: Compared with the modified Tissot bell-spirometer, the CCM Express Indirect Calorimeter demonstrated a mean Δ-REE of +361 kcal/d, corresponding to a 31% overestimation of energy requirements. Bland-Altman analysis for REE showed a mean (SD) bias of 384 (124) with limits of agreement 142–627 kcal/d. QUARK RMR ICU demonstrated a mean Δ-REE of 81 kcal/d, corresponding to a 7% overestimation of energy requirements. Bland-Altman plot analysis showed a mean (SD) bias of 77 (167) with limits of agreement −249 to 404 kcal/d. Conclusions: The QUARK RMR ICU Indirect Calorimeter compared better with the gold standard for values of
O2 and REE than did the CCM Express Indirect Calorimeter in mechanically ventilated patients who were circulatory and respiratory stable. Both indirect calorimeters had low precision.
