Strategies to prevent lung injury, facilitate lung development, and to support the preterm infant's capacity to breathe are decisive. Continuous positive airway pressure (CPAP) is the gold standard in non-invasive breathing support in preterm infants with a positive pressure that keeps the alveoli slightly inflated during expiration. Non-invasive neurally adjusted ventilator assist (NIV NAVA) is a novel method of breathing support and uses the electrical activity from the diaphragm to trigger the ventilator and synchronize with the breathing cycle. During NIV NAVA the preterm infant controls the onset of the inspiration, the respiratory rate, inspiratory time and peak pressure. This method has the potential to improve the positive pressure transmission to the infant's lower airways, accurate synchronization with the breathing pattern and be a comfortable breathing support system for the preterm infant.

The investigators will compare the effect on breathing effort in preterm infants during continuous positive airway pressure and non-invasive neurally adjusted ventilatory assist measured by electrical activity in the diaphragm, respiratory vital signs, systematic clinical scoring of breathing effort and comfort, and parent reported outcomes.

This is a randomized cross-over study with AB/BA sequences. The infants will receive both interventions in 4 hours intervals, a 30 minutes period to change the breathing support and a 30 minutes wash out period between interventions. Initially positive end expiratory pressure are set to 5 cm H2O and can be adjusted up to 7 cm H2O if needed decided by the medical team for both interventions. The neurally adjusted level will be set to obtain average Edi peak < 15 microvolt. Back-up setting and apnea time in the ventilator assist intervention (NIV NAVA) will be individualized according to clinical parameters in each preterm infant.

Modification approved by ethical committee REK 2021, 6th of August:

After two hours in each intervention, the nurse responsible for the infant will perform the clinical scoring. In addition it will be investigated if there is a difference in respiratory vital signs during skin to skin care and in the incubator. During each intervention period, the preterm infants are placed on the parent's chest skin to skin for at least one hour.

A modified version of the scoring tool will be used, i.e. without the item of nasal flaring and expiratory grunting. The headgear for CPAP and NIV NAVA covers parts of the nose and makes nasal flaring difficult to observe.

Inclusion Criteria:

• spontaneously breathing preterm infants 24 to 96 hours old
• gestational age (GA) between week 28+0 and 31+6
• preterm infants with GA < 28+0 with a postmenstrual age (PMA) > 28 weeks
• at least 72 hours old treated with CPAP or NIV NAVA

Exclusion Criteria:

• preterm infants with severe congenital malformation
• need for vasopressors
• preterm children in need of a specific respiratory support system due to medical reasons

Study protocol Statistical analysis Informed consent form

2022 and to 2027