Study flow chart and pathway. Study flow chart and pathway. Detailed study design and procedures including inclusion, exclusion and exit criteria. CPAP, continuous positive airway pressure; FiO2, oxygen concentration; HFNC, high-flow nasal annula; LPM, litres per minute; NIV, non-invasive ventilation; SpO2, oxygen saturation;TOSCA, transcutaneous CO2. Zheyi Liew et al. Arch Dis Child Fetal Neonatal Ed doi:10.1136/archdischild-2018-316773 Copyright © BMJ Publishing Group Ltd & Royal College of Paediatrics and Child Health. All rights reserved.