Validation of ventilator-derived VCO2 measurements to determine energy expenditure in ventilated critically ill children

Summary Background & aims Indirect calorimetry (IC) is considered the gold standard to determine resting energy expenditure (REE) but its availability in PICUs worldwide is limited. Ventilator-derived VCO2 could potentially improve the possibility of performing REE measurements. We investigated whether ventilator-derived VCO2 values are comparable to IC-derived VCO2 values and can clinically be used in clinical practice to determine REE. Methods VCO2 -values were simultaneously collected in mechanically ventilated children from IC (Deltatrac® ) and Servo-I® ventilator on a minute base over at least 10 min period of steady state. REE was calculated using the modified Weir formula (for IC) or REE = 5.5*VCO2 (L/min)*1440 (for the Servo-I values) and compared with frequently used predictive equations by Schofield and the WHO to calculate REE. Results Measurements were performed in 41 children; median age 2 years. The mean relative difference between VCO2 measured by IC and Servo-I® was 15.6% (p = 0.002), and limits of agreement in the Bland–Altman analysis were wide. Comparable measurements, defined as a difference ≤10% between IC and Servo-I® VCO2 values, were seen in 18 (44%) children, but this proportion was 70% in children ≥15 kg. In this group, REE could be accurately predicted using Servo-I® derived VCO2 values and this method was superior to the use of predictive equations. The Servo-I® derived VCO2 values were not sufficiently accurate for the large proportion of children weighing