Noninvasive respiratory supports (NRS), such as continuous positive airway pressure (CPAP), noninvasive ventilation, high flow nasal cannula (HFNC) or nasal oxygen (O2), are commonly used in preterm newborns hospitalized in neonatal intensive care unit. However, given the lack of validated criteria, clinicians usually choose the NRS according to clinical parameters and patients' comfort. Several studies have demonstrated the interest of the measurement of the work of breathing (WOB) to optimize the settings of NRS in children, but no study has already demonstrated the utility of WOB to optimize the settings of NRS in preterm infants. Therefore, the aim of this study is to measure the WOB during the utilisation of three different NRS (CPAP, HFNC, O2), in order to optimize the choice of the type and settings of NRS in a randomized group of 30 newborns born prematurely before 30 gestational weeks and still requiring NRS at 29 post conceptual weeks. Moreover, the investigators will compare in the newborns with the optimized NRS by WOB vs. a standard care control group (NRS type and settings determined as clinical routine): 1) the respiratory morbidity and mortality one month after the initial assessment, and at the time of hospital discharge (or transfer) or at 36 weeks of age corrected (whatever comes first), 2) the weaning time of the NRS, 3) the incidence and severity of broncho-pulmonary dysplasia (BPD) at 36 weeks of age corrected. Indeed, incidence of BPD is still around 40% in premature infants born before 28 gestational weeks. The hypothesis of the investigators' study is that the optimization of the type and settings of the NRS could reduce the weaning delay and contribute to reduce the incidence and severity of BPD in premature newborns.

Inclusion Criteria:

• Preterm infants born between 23 and 30 GA
• Aged over 29 weeks of corrected age at the time of assessment and needing a non invasive respiratory support since at least 4 weeks of age

Exclusion Criteria:

• Hemodynamic and/or neurologic instability
• Invasive ventilation
• Congenital cardiopathy and/or significant patent ductus arteriosus
• Sedation
• Congenital pulmonary disease and/or other malformations

Preterm infants needing a non invasive respiratory support after 4 weeks of life