Can calculation of energy expenditure based on CO 2 measurements replace indirect calorimetry?

Abstract Background Methods to calculate energy expenditure (EE) based on CO 2 measurements (EEVCO 2 ) have been proposed as a surrogate to indirect calorimetry. This study aimed at evaluating whether EEVCO 2 could be considered as an alternative to EE measured by indirect calorimetry. Methods Indirect calorimetry measurements conducted for clinical purposes on 278 mechanically ventilated ICU patients were retrospectively analyzed. EEVCO 2 was calculated by a converted Weir\u2019s equation using CO 2 consumption (VCO 2 ) measured by indirect calorimetry and assumed respiratory quotients (RQ): 0.85 (EEVCO 2 _0.85) and food quotient (FQ; EEVCO 2 _FQ). Mean calculated EEVCO 2 and measured EE were compared by paired t test. Accuracy of EEVCO 2 was evaluated according to the clinically relevant standard of 5% accuracy rate to the measured EE, and the more general standard of 10% accuracy rate. The effects of the timing of measurement (before or after the 7th ICU day) and energy provision rates (