Nasal continuous positive airway pressure (CPAP) and Nasal High Flow (NHF) therapy are two primary therapies for the treatment of respiratory distress in newborns. However, a considerable number of infants, who are initially treated with CPAP and NHF, will develop worsening respiratory failure and eventually require intubation for mechanical ventilation and the administration of surfactant. Infants who fail noninvasive respiratory therapy may suffer the consequences of delayed intubation, surfactant administration and other adverse outcomes. The most challenging decisions in the management of respiratory distress after birth is to decide when to move from a noninvasive respiratory support to invasive mechanical ventilation and give surfactant to decrease pulmonary damage and improve outcomes. There are no clinically adequate predictors of early CPAP failure at the time of admission to the neonatal intensive care unit. Many measurements have been investigated for their ability to predict CPAP failure in infants such as fraction of inspired oxygen (FiO2), partial pressure of oxygen (PaO2), PaO2/FiO2 and the stable micro bubble test as soon as possible after birth. Roca and colleagues first established the ROX index to predict the success of NHF therapy in adults with pneumonia. The ROX index combines three common measurements: FiO2, peripheral oxygen saturation (SpO2) and respiratory rate. Combining the ROX values with the change in the respiratory rate and FiO2 can indicate whether escalation is required. It was proposed that XY plot of the key components of ROX may show the direction of changes in vector form.

The investigators hypothesized that the ROX index and ROX vector can be used for predicting the failure of CPAP and NHF in neonates.

The objective is to explore the usefulness of ROX index to predict treatment failure of NHF and CPAP therapies in neonates.

The primary outcome is treatment failure within 72 h after start of the therapy with NHF or CPAP

Treatment failure criteria is reached once an infant is receiving maximal therapy for their treatment (NHF 8 L/min) or CPAP 7 cm H2O plus at least one of:

1. Sustained increase in oxygen requirement ≥50% to maintain peripheral oxygen saturation (SpO2) 90%-94%.
2. Any infant requiring urgent intubation and the subsequent mechanical ventilation, as determined by the physician.

Inclusion criteria:

• They are admitted to a NICU when <24 h old, AND
• The decision has been made by the attending clinician, to commence or continue (from stabilization at birth) non-invasive respiratory support (this does not include the provision of supplemental oxygen alone), AND
• They have not previously been intubated or received surfactant

Exclusion criteria:

• They immediately require intubation and ventilation (determined by attending clinician), OR
• They already satisfy 'treatment failure' criteria, OR
• They have a known major congenital anomaly or air leak

neonates with respiratory distress