The goal of this clinical trial is to evaluate the feasibility, safety, and preliminary effectiveness of applying external continuous negative pressure (ECNP) during less invasive surfactant administration (LISA) in preterm infants with respiratory distress syndrome (RDS). It will also assess whether ECNP can improve surfactant distribution and reduce procedural complications. The main questions it aims to answer are:

Does ECNP during LISA improve surfactant distribution and oxygenation in preterm infants with RDS?

Does ECNP reduce the occurrence of complications such as desaturation, bradycardia, or apnea during the procedure?

Does ECNP reduce the need for repeated surfactant administration?

Researchers will evaluate ECNP combined with LISA in preterm infants on HFNC or CPAP to see if it improves outcomes compared to standard methods.

Participants will:

Receive LISA with ECNP support via a soft thoracoabdominal cuirass

Be monitored for procedural complications like desaturation, bradycardia, or apnea

Have their oxygenation levels, surfactant distribution, and need for repeated surfactant doses assessed

Primary Outcome:

The procedure will be considered safe if no more than 20% of participants experience serious adverse events, such as apnea requiring positive pressure ventilation or persistent desaturation.

Secondary Outcomes:

Completion of LISA without interruption due to complications

Reduction of FiO₂ to ≤0.25 within 3 hours post-surfactant administration

Avoidance of repeated surfactant doses via the INSURE method

This pilot study evaluates the feasibility, safety, and preliminary effectiveness of applying external continuous negative pressure (ECNP) during less invasive surfactant administration (LISA) in preterm infants with respiratory distress syndrome (RDS) supported by non-invasive respiratory support. ECNP, delivered via a modern negative-pressure ventilation device and a soft thoracoabdominal cuirass, generates a sustained sub-atmospheric pressure around the chest wall. This mode of support is intended to facilitate spontaneous breathing, promote more homogeneous lung inflation, and potentially enhance the distribution of intratracheally delivered surfactant.

LISA using thin catheters is a widely adopted method for surfactant administration in spontaneously breathing neonates receiving CPAP or HFNC. Although effective, the procedure is frequently complicated by transient hypoxemia, bradycardia, apnea, and surfactant reflux, occasionally requiring temporary interruption or conversion to more invasive therapy. These complications may impair surfactant delivery, contribute to uneven lung aeration, and lead to the need for repeated dosing. To date, the integration of continuous negative-pressure support during LISA has not been evaluated in clinical practice.

In this single-arm feasibility study, ECNP will be initiated shortly before and maintained throughout the LISA procedure. The study will assess whether negative-pressure support stabilizes spontaneous ventilation, improves oxygenation, and facilitates more uniform surfactant distribution during administration. Safety will be evaluated based on the occurrence of serious procedure-related events requiring interruption, such as significant desaturation, bradycardia, or apnea requiring positive-pressure ventilation. Effectiveness will be explored through measures of post-procedure oxygenation stability, need for repeat surfactant dosing, and indicators of adequate surfactant distribution (e.g., imaging assessments when clinically indicated).

This exploratory study is designed to inform the potential utility of ECNP as an adjunct during LISA and to determine whether a larger controlled trial is warranted. The protocol focuses on documenting feasibility (ability to complete LISA under ECNP), characterizing physiologic responses, and capturing any adverse events specifically associated with ECNP use in this population

Inclusion Criteria:

• Preterm infants ≥ 32 weeks of gestational age
• FiO₂ > 0.30 for more than 30 minutes on CPAP (6 - 8 cm H₂O) or HFNC (8 l/min)
• Increased work of breathing despite FiO₂ < 0.30
• Birth weight > 800 g
• X-ray confirmed RDS
• Availability of all required devices and appropriately fitting cuirass

Exclusion Criteria:

• Requirement for endotracheal intubation or mechanical ventilation prior to surfactant administration
• Major congenital anomalies (cardiac, pulmonary, chromosomal)
• Known or suspected neuromuscular or metabolic disorders
• Lack or withdrawal of informed parental consent