NIV NAVA Versus NIV-PS in Pediatric Patients - Pilot Study

Inclusion Criteria: * Age: \> 1 month age to 18 years * Moderate/severe Pediatric Acute Respiratory failure of any origin evaluated after a period of respiratory stabilization (aspiration of secretions, physiotherapy, oxygen and nebulized therapy) when the attending pediatric intensive care physician believes that the patient is likely to require endotracheal intubation (ETI). * Non intubated * Admitted to the PICU * Minimally agitated/sedated: between -2 and +2 on the Richmond agitation-sedation scale (Table 2) Exclusion Criteria: 1. Patients younger than 1 month or older than 18 year 2. Patients who need immediate endotracheal intubation: i.e.: Severe ARF with signs of exhaustion 3. Facial trauma/burns 4. Recent facial, upper way, or upper gastrointestinal tract surgery excepting gastrostomy for feeding 5. Fixed obstruction of the upper airway 6. Inability to protect airway 7. Life threatening hypoxemia defined as SpaO2 \<90% with FiO2 \> 0.8 on hi-flow oxygen. 8. Hemodynamic instability: refractory at volume expansion \>60 ml/kg and dopamine \>10 mcg/kg/min 9. Impaired consciousness defined as Glasgow coma scale \< 10. 10. Bowel obstruction. 11. Untreated pneumothorax. 12. Poor short term prognosis (high risk of death in the next 3 months) 13. Known esophageal problem (hiatal hernia, esophageal varicosities) 14. Active upper gastro-intestinal bleeding or any other contraindication to the insertion of a NG tube. 15. Neuromuscular disease 16. Vomiting 17. Cough or gag reflex impairment. 18. Cyanotic congenital heart disease. 19. Complete absence of cooperation 20. This patient has been included (randomized) previously in the study