There is currently a consensus that non-invasive ventilation (NIV) in preterm infants is preferred over intubation. There are two ways of delivering NIV in preterm infants, nasal continuous positive airway pressure (CPAP) or nasal intermittent positive pressure ventilation (NIPPV), where ventilator inflations are delivered intermittently over a fixed end-expiratory pressure. The synchronization in conventional mode is very difficult to obtain in premature infants. In all ventilation modes PEEP (end-expiratory pressure) is fixed. Considering that preterm infants are more likely to develop atelectasis, an active and ongoing management of the PEEP is very important to prevent de-recruitment.

A new respiratory support system (NeuroPAP) was developed to address these issues (synchronization problems and control the PEEP). It uses the electrical activity of the diaphragm (EDI) to control the ventilator assist continuously, both during inspiration (principle of NAVA mode) and also during expiration (based on tonic Edi level).

The mode NeuroPAP will work with the continuous Edi-level and deliver pressures according to the Edi-signal x set NeuroPAP-level, over the whole breath (inspiration and expiration). The NeuroPAP will work between two pressure levels set by the user and named higher Pressure limit (Plimit) and minimum Pressure (Pmin).

A safety upper pressure limit (UPL) will also be set. A backup ventilation will be possible.

A specific gastric tube equipped with an array of microelectrodes (Edi catheter, Maquet, Solna, Sweden) will be installed after inclusion, by the same oral or nasal route as the tube previously in place. Patients will then be ventilated in the 5 aforementioned conditions:

• On conventional NIPPV device on clinical settings for a 30 minute period. The investigators will note the mean airway pressure being delivered with the clinical settings and the resulting peak Edi, as well as neural respiratory rate, tonic Edi, Fraction of inspired oxygen (FiO2), and Oxygen saturation by pulse oximetry (SpO2).
• With NeuroPAP without modification of Pmin (=peep). The exchange of the nasal interface may be necessary, depending on the original interface. FiO2 will initially be the same as previously set in conventional NIPPV. The Pmin will initially be set at the level of PEEP used during conventional NIPPV. A titration maneuver will be conducted to identify the optimal NeuroPAP level. The infant will be ventilated for one hour. Clinical adjustments in pressures and FiO2 are permitted. Safety termination will be established.
• NeuroPAP with adjusted Pmin: the Pmin in NeuroPAP will be reduced by 2 cm H2O, with the same NeuroPAP level. The patients will be ventilated for one hour.
• CPAP delivery with NeuroPAP device: the device will be switched to CPAP mode, for a 15 minute period
• A second 30 minutes period of the conventional NIPPV will be conducted.

Inclusion Criteria:

• Preterm infants, >26 0/7 and < 34 weeks GA, at least 3 days old and younger than 1 month,
• on NIPPV with settings in the range : Maximal inspiratory pressure (total, including PEEP) < 20 cmH2O, and PEEP : 5-7 cmH2O,
• with FiO2 <40%, and stable.

Exclusion Criteria:

• Suspected or proven pneumothorax
• Patient on high-flow nasal cannula or nasal continuous positive airway pressure (nCPAP)
• Infants with severe recurring apnea
• Recent worsening of respiratory status with increase work of breathing, recent increase in FiO2, or linked with a suspected sepsis
• Contraindications to the placement of a new nasogastric tube (e.g. severe coagulation disorder, malformation or recent surgery in cervical, nasopharyngeal or esophageal regions)
• Hemodynamic instability requiring inotropes.
• Severe respiratory instability requiring imminent intubation according to the attending physician, or FiO2 > 45%, or PaCO2 > 65 mmHg on blood gas in the last hour.
• Patient for whom a limitation of life support treatments is discussed or decided.
• Refusal by the treating physician.