Exploring the utility of indirect calorimetry to optimise nutrition in paediatric intensive care (ICONIC-1): a prospective observational cohort study protocol

The imprecision of predictive equations has led to recommendations for the use of indirect calorimetry (IC) to determine measured energy expenditure (MEE) in the paediatric intensive care unit (PICU). However, the feasibility of newer devices, such as the QNRG+ (COSMED, Italy), and the impact of IC-guided nutrition delivery on patient outcomes remains unclear. This study aims to determine current IC feasibility, assess accuracy of the Schofield predictive equation relative to MEE, explore associations between MEE and defined clinical factors, examine relationships between IC-guided nutrition balance and body composition, and evaluate the health-system economic impact of IC use in PICU. ICONIC-1 is a single-centre, prospective observational cohort study. All mechanically ventilated children aged < 18 years will be screened daily. For eligible participants, IC will be performed two to three times weekly. Body composition will be assessed via skeletal muscle ultrasound and bio-impedance analysis on pre-defined study days. Daily nutrition delivery and clinical data will be collected until PICU discharge. Agreement between predicted energy requirements and MEE will be assessed, alongside associations between MEE and key clinical factors. Relationships between cumulative nutrition balance, longitudinal changes in muscle and fat mass and impact on health system-related costs will also be examined. ICONIC-1 will provide valuable data on the feasibility and clinical utility of the QNRG + IC device in the PICU. Findings will provide evidence to inform optimal PICU nutrition guidelines, practices, resource allocation, and may support the routine use of IC to improve feeding practices in clinical care. This study has been retrospectively registered on the Australian and New Zealand Clinical Trials registry (ACTRN12626000080325) on 21/01/2026. Version 9.0, 11.12.2025.