Figure 1.

Indirect calorimetry on mechanically ventilated patient (A) and on spontaneous breathing patient in canopy mode (B). In mechanical ventilation the gas sampling is acquired by the circuit connecting the endotracheal tube to the ventilator and measured by ‘breath-by-breath’ or mixing chamber analyses. In spontaneous breathing mode, the subject is placed under a clear canopy with a plastic drape to avoid air leakage. Breath exchanges are collected by the calorimeter for gas analysis and enable calculation of REE using Weir’s equation (REE (kcal/day) = [(VO₂ × 3.941) + (VCO₂ × 1.11)] × 1440).