1. Any contraindications to surfactant administration e.g., pulmonary haemorrhage and pneumothorax) 2. Weight < 40kg 3. Stage 4 severe chronic kidney disease (i.e., eGFR < 30) 4. Pregnancy 5. Administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration 6. Extracorporeal membrane oxygenation* * [Exclusion criterion NOT applicable for patients eligible for the ECMO-cohort]

1. Any contraindications to surfactant administration e.g., pulmonary haemorrhage and pneumothorax) 2. Weight < 40kg 3. Stage 4 severe chronic kidney disease (i.e., eGFR < 30) 4. Pregnancy 5. Administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration 6. Extracorporeal membrane oxygenation* * [Exclusion criterion NOT applicable for patients eligible for the ECMO-cohort]