Secondary variables will be defined as the total time of nCPAP , the total time of oxygen use; time for the indication of invasive mechanical ventilation, the incidence of pneumothorax and the maximum values of FiO2 in noninvasive support, the average values of CPAP pressure, the incidence of bronchopulmonary dysplasia (defined as oxygen requirement at 36 weeks corrected gestational age), the incidence of intracranial hemorrhage and intracranial hemorrhage grades III and IV according to Papile et al.