In France, over 2.5 million people suffer from asthma, including one-third of children. This is the chronic respiratory disease leading to the highest rate of hospitalization. The conventional oxygen delivery means in children are the non-rebreather face mask or low flow nasal cannula (standard oxygen therapy - SOT). New non-invasive ventilatory support systems such as High Flow Nasal Cannula (HFNC) are emerging. These are nasal cannulas allowing the delivery of a high air (or oxygen) flow, exceeding the inspiratory flow of patients with acute respiratory failure, allowing to deliver a slight positive expiratory pressure while ensuring humidification and warming of the airways. Aerosol administration is also possible with excellent efficiency and without interrupting respiratory assistance. Physiological data and clinical studies in other pathologies suggest the interest of this technique during the asthma attack, but no comparative study currently exists in this indication. The HFNCs could have their place upstream of Non Invasive Ventilation (NIV), thus replacing non-rebreather face mask sometimes not tolerated by the children. The investigators's hypothesis is that HFNCs could improve patients' health faster, reduce the use of other ventilatory assistance (NIV, invasive ventilation) and reduce the duration of hospitalization in intensive care units or continuous monitoring units (CMU).

Inclusion Criteria:

• Age ≥ 6 months and <18 years old

• Hospitalized in PICU with status asthmaticus defined by

  1. a PRAM score > 7 with no response at H2 to the conventional treatment according to the GINA (Global Initiative for Asthma guidelines) protocol: Oxygen therapy, Continuous nebulization of beta2 agonist for at least one hour then every hour, Oral or intravenous corticosteroid (ie methylprednisolone 2mg/kg/j)
  2. or with hypercapnic acidosis (pCO2 > 45 mmHg and pH < 7,35)

• Informed consent signed by at least on parent or legal guardians prior to inclusion and oral consent of the other parent if absent

Exclusion Criteria:

• Non-corrected congenital heart disease, or neuromuscular disease, or chronic respiratory disease (pulmonary or bronchial fibrosis, cystic fibrosis), or ENA disease (laryngo or tracheo malacia), scoliosis or chronic metabolic disease
• Need for non-invasive or invasive ventilation (Glasgow comas scale <8, hemodynamic instability, refractory hypoxemia, cardiac arrest)
• Pneumothorax confirmed on the X-ray
• No national health coverage