Gas-exchange and resting energy expenditure measurement with indirect calorimetry in children supported with non-invasive ventilation

Introduction. Nutrition plays a fundamental role in critically ill children and personalized nutritional therapy requires the measurement of resting energy expenditure (REE) [1-2]. Indirect calorimetry (IC) is the gold standard for REE assessment and is based on VO2 and VCO2 measurements. Furthermore, IC provides information on carbohydrates/lipids consumption by defining the respiratory quotient (RQ). However, while IC is validated for spontaneously breathing and mechanically ventilated patients, it is not for patients undergoing non-invasive ventilation (NIV) [3]. Aim of the study is therefore to validate IC for children undergoing NIV by comparing IC results obtained during spontaneous breathing with data gathered during NIV-CPAP (continuous positive airway pressure). Methods. Patients (age <6 years) admitted to our pediatric intensive care unit (PICU) and weaning from NIV-CPAP were enrolled. Two IC measurements (Canopy mode) were performed for 20 minutes in randomized order in the following conditions: 1) Spontaneous breathing (SB), 2) NIV-CPAP (performed by single-limb circuit and vented mask). Average values for VCO2 , VO2, RQ and REE were obtained in the two conditions. Comparison between groups was performed via paired t-test. Agreement was assessed via Bland-Altman analysis. Statistical significance was defined as p<0.05. Results. Four patients (median age 8 months, median weight 8 kg) were enrolled. VCO2 , VO2, RQ and REE did not differ significantly between groups. Limits of agreement (LOA) and BIAS indicate a good agreement between the two measures (Table 1). Conclusions. Our preliminary data suggest that IC can be accurately performed in children undergoing NIV using a single limb circuit with intentional leaks. These results need to be confirmed on a broader cohort of critically ill children. References 1. De Cosmi V et al. Nutrients. 2017, 18:9 2. Mehta NM et al. Pediatr Crit Care Med. 2017, 18:675-715 3. Taku Oshima et al. Clinical Nutr 2017; 36:651-662