participants were excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) 2. weight \< 40kg 3. stage 4 severe chronic kidney disease (i.e., estimated glomerular filtration rate (egfr) \< 30) 4. pregnancy 5. administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration 6. extracorporeal membrane oxygenation (ecmo)

participants were excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) 2. weight \< 40kg 3. stage 4 severe chronic kidney disease (i.e., estimated glomerular filtration rate (egfr) \< 30) 4. pregnancy 5. administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration 6. extracorporeal membrane oxygenation (ecmo)

participants were excluded from the study if any of the following criteria apply: any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) weight < 40kg stage 4 severe chronic kidney disease (i.e., estimated glomerular filtration rate (egfr) < 30) pregnancy administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration extracorporeal membrane oxygenation (ecmo)

participants were excluded from the study if any of the following criteria apply: any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) weight < 40kg stage 4 severe chronic kidney disease (i.e., estimated glomerular filtration rate (egfr) < 30) pregnancy administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration extracorporeal membrane oxygenation (ecmo)

participants are excluded from the study if any of the following criteria apply: any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) weight < 40kg stage 4 severe chronic kidney disease (i.e., egfr < 30) pregnancy administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration

participants are excluded from the study if any of the following criteria apply: any contraindications to surfactant administration e.g., pulmonary hemorrhage and pneumothorax) weight < 40kg stage 4 severe chronic kidney disease (i.e., egfr < 30) pregnancy administration of any nebulized surfactant in the 48 hours before the first poractant alfa administration

participants are excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage 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

participants are excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage 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

participants are excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage 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]

participants are excluded from the study if any of the following criteria apply: 1. any contraindications to surfactant administration e.g., pulmonary hemorrhage 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]