- Severe RDS, defined by one of the following: Silverman-Anderson score > 6, severe hypoxia (FiO2 > 0.5), hemodynamic disorders (HR> 180 / min, MABP <30mmHg, capillary refill time > 5s, pallor), and severe apneas (> 5s and / or with bradycardia <80 /min)