The trial was terminated early based on interim analysis results indicating futility. The decision was approved by the Data Safety Monitoring Committee (DSMC).

BACKGROUND Non-invasive ventilation (NIV) treatment have been developed to minimize lung damage and to avoid invasive mechanical ventilation (IMV) in preterm infants, especially in those with gestational age less than 30 weeks. Our hypothesis is that for preterm infants less than 30 weeks with potential to develop neonatal respiratory distress syndrome (NRDS), nasal continuous positive airway pressure (NCPAP) is non-inferior to the nasal intermittent positive pressure ventilation (NIPPV) as primary respiratory support before minimal invasive surfactant administration (MISA).

DESIGN, SETTING, AND PARTICIPANTS The NIV-MISA-NRDS trial is planned as an unblinded, multicenter, randomized, non-inferiority trial at 11 tertiary care neonatal intensive care units in China. Eligible infants are preterm infants of 24 to 29+6 weeks' gestational age who have spontaneous breaths at birth and require primary NIV support for NRDS in the first 2 h of life. Infants are randomized 1:1 to treatment with either NCPAP or NIPPV once admitted into neonatal intensive care unit (NICU). If the patient with progressively aggravates respiratory distress and clinically diagnose as NRDS, pulmonary surfactant will be supplemented by minimal invasive surfactant administration (MISA) in the first 2 hours .

MAIN OUTCOMES AND MEASURES The primary outcome is NIV treatment failure within 72 hours after birth, as determined by objective oxygenation, blood gas, and apnea criteria, or the need for intubation and mechanical ventilation. Secondary outcomes mainly include the incidence of complications during hospitalization . With a specified noninferiority margin of 10%, using a two-sided 95% CI and 80% power, the study requires 480 infants per group (total 960 infants in the study).

The ventilator parameter of NCPAP group are set with positive end expiratory pressure [PEEP] of 6cmH2O (adjustment range 6-8cmH2O) and FiO2 of 0.21-0.40, in order to maintain an oxygen saturation level of 90%-95%.

NIPPV group are set with PEEP of 6cmH2O (adjustment range 6-8cmH2O), peak inspiratory pressure [PIP] of 15cmH2O (regulation range 15-20cmH2O), inspiratory time of 0.3s (regulation range 0.3-0.4s), respiratory rate of 30 times/min (regulation range 20-40 times/min) and FiO2 of 0.21-0.40.

Inclusion Criteria

Infants who meet all of the following criteria will be included:

1. Infants of 24 to 29+6 weeks GA.
2. Infants with spontaneous breathing and signs of respiratory distress will receive non-invasive respiratory support (PEEP of 6 cmH2O and fraction of inspired oxygen[FiO2]≤0.40) immediately after birth in the delivery room and during transfer to NICU. Once the infant is settled down in the incubator, and the ventilation support of NCPAP or NIPPV by ventilator in NICU will by started according to the randomization of protocol.
3. Under NCPAP or NIPPV, the surfactant will be administered via MISA approach within 120 minutes after birth if the infant required FiO2>0.3 for transcutaneous oxygen saturation [SpO2]>85%, or Silverman Anderson Score [SAS] >5 points or SAS increasing >2 points per hour.
4. Parental consent will be obtained for all participants.

Exclusion Criteria

Infants who meet any of the following criteria will be excluded:

1. Infants who have been intubated prior to pulmonary surfactant administration due to postnatal resuscitation or other reasons.
2. Infants with obvious malformations affecting respiratory function.
3. Infants who have been transferred out to other hospitals for surgery or died for other complications with uncompleted data.
4. Infants who have participated in other interventional researches.