It is hypothesized that the use of Neurally Adjusted Ventilatory Assist (NAVA) compared to pressure support to provide noninvasive ventilation to children will result in a decrease in the number of children with moderate to severe respiratory failure failing noninvasive ventilation and requiring endotracheal intubation. It is further hypothesized that noninvasive ventilation with NAVA compared to pressure support will result in a decrease in the length of mechanical ventilation, and the length of PICU and hospital stay.

Mechanical ventilation (MV) refers to the use of life-support technology to perform the work of breathing for patients who are unable to breathe on their own. One of the most common reasons for a Pediatric Intensive Care Unit (PICU) admission is the need for mechanical ventilation. However, MV is associated with increased morbidity (endotracheal intubation, tracheal edema, atelectasis, cardiovascular instability, ventilator-associated pneumonia, bleeding, pneumothorax, chronic lung disease, etc), a long length of stay in the PICU and high health care costs. Noninvasive ventilation (NIV) has become a primary approach to ventilatory support of patients of all ages and it is estimated that it can avoid endotracheal intubation and replace conventional mechanical ventilation in around 60% of patients with acute respiratory failure. NIV has been shown to ameliorate clinical signs of failure and improve gas exchange while reducing the need for endotracheal intubation (ETI) thus avoiding the risks associated with invasive ventilation. NIV has been shown to decrease the length of mechanical ventilation, the risk of ventilator associated pneumonia, the sedation requirement, the length of ICU and hospital stay and mortality, while improving the ability to tolerate enteral feeds. NIV does not increase beside caregiver time and does decrease cost.

With children because of the difficulty in assuring the patient's cooperation, the lack of available high quality masks and the resulting size of the air leak, synchrony between the ventilatory pattern of the patient and the support provided by the ventilator is poor. This problem had lead to repeated failure of noninvasive ventilation in children. The primary mode of noninvasive ventilatory support is pressure support (NIV PS). This mode is triggered to inspiration and cycled to exhalation by changes in patient inspiratory gas flow. But with air leaks the ability of the ventilator to coordinate with the patient is decreased.

A new mode of ventilation, Neurally Adjusted Ventilatory Assist (NAVA) has been recently introduced. This mode triggers, cycles and regulates gas delivery based on the diaphragmatic EMG signal via a specially designed nasogastric tube (Edi). As a result, air leaks do not affect the ability of the ventilator to synchronize gas delivery with the patient increasing patient ventilator synchrony. Based on the operation of NAVA it is expected to increase the successful application of noninvasive ventilation to children.

Inclusion Criteria:

1. Age > 1 month age or weight > 3 Kg to 18 years
2. Not intubated.
3. Admitted to the PICU.
4. Minimally agitated/sedated: between -2 and +2 on the Richmond agitation-sedation scale (Table 2).
5. Moderate/severe Pediatric Acute Respiratory failure of any origin evaluated after a period of respiratory stabilization (aspiration of secretions, physiotherapy, oxygen and nebulized therapy) defined as: a) Modified Silverman-Wood Downess test >or= 5 or <or= 9; b) Hypoxemic ARF(SpO2< 94% FiO2 0,5). c)Hypercapnic ARF (PaCO2 (mmHg) and/or pH <7,30)
6. The attending pediatric intensive care physician believes that the patient is likely to require endotracheal intubation (ETI).

Exclusion Criteria:

1. Patients younger than 1 month or older than 18 year
2. Severe ARF defined as Modified Silverman-Wood Downes test >9.
3. Patients who need immediate endotracheal intubation: i.e.: Severe ARF with signs of exhaustion
4. Facial trauma/burns
5. Recent facial, upper way, or upper gastrointestinal tract surgery excepting gastrostomy for feeding
6. Fixed obstruction of the upper airway.
7. Inability to protect airway
8. Life threatening hypoxemia defined as SpaO2 <90% with FiO2 > 0.8 on hi-flow oxygen.
9. Hemodynamic instability: refractory at volume expansion >60 ml/kg and dopamine >10 mcg/kg/min
10. Impaired consciousness defined as Glasgow coma scale < 10.
11. Bowel obstruction.
12. Untreated pneumothorax.
13. Poor short term prognosis (high risk of death in the next 3 months)
14. Known esophageal problem (hiatal hernia, esophageal varicosities)
15. Active upper gastro-intestinal bleeding or any other contraindication to the insertion of a NG tube.
16. Neuromuscular disease
17. Vomiting
18. Cough or gag reflex impairment.

18. Cyanotic congenital heart disease. 19. Complete absence of cooperation 20. This patient has previously been randomized in the study. 21. Repeated extubation failures (>or= 2).