Use of Nasal High Flow Oxygen During Breaks of Non-invasive Ventilation for Patients With Hypercapnic Respiratory Failure

In both groups, treatment will start with a first NIV session of 2 hours, with arterial blood gas measurement between one hour and two hours after initiating the NIV session. The NIV will be extended for those patients with a pH < 7.30. In both groups, patients will be assessed for their tolerance of NIV and their ability to switch to spontaneous breathing every hour +/- 30 min, except during sleep (10 pm-8 am); they will be assessed for their tolerance of spontaneous breathing and for the need of resumption of NIV every 2 hours+/- 30 min and every 4 +/- 1 hours thereafter. To ensure the consistency of indications of NIV and invasive mechanical ventilation (IMV) across centers and reduce potential bias, NIV and IMV will be initiated and stopped in the same way in the two groups, using predefined criteria.

• Inclusion (day 0): informed consent, randomisation (HFHO group/standard O2 group), NIV initiation (for 2 hours), clinical and paraclinical exam including ABG, data collection
• Follow-up (day 1 to day 28) : NIV, clinical exam, ABG, data collection

Inclusion criteria

• Adult patients aged 18 or above, admitted to an ICU, an intermediate care or a respiratory care unit;
• Chronic respiratory disease previously documented or strongly suspected on clinical, radiological and blood gazes data and pulmonary function tests, in connection with an obstructive respiratory disease (COPD, emphysema, overlap-syndrome (COPD + obstructive sleep apnoea) or mixed (bronchiectasis, obesity-hypoventilation syndrome))
• Patients requiring NIV for hypercapnic ARF (whatever the precipitating cause) i.e. with clinical signs of moderate to severe respiratory distress : dyspnea and /or respiratory rate > 25/min and/or use of accessory respiratory muscles and/or paradoxical abdominal motion and/or signs of respiratory encephalopathy (sleepiness, asterixis, confusion); and respiratory acidosis on arterial blood gases, defined by pH<7.35 and PaCO2 > 45 mmHg despite the careful supply of oxygen and appropriate therapy that may include bronchodilators, corticosteroids and antibiotics

Exclusion criteria

• Contraindications to NIV;
• Purely restrictive lung disease (thoracic deformity, neuro-muscular pathology) and pure obstructive sleep apnoea (without spirometric disturbance or daytime gas anomaly)
• Immediate need for intubation (respiratory or cardiac arrest);
• Persistent hemodynamic instability (use of vasopressors for > 1 hour);
• Multiple organ failure (score SOFA>6);
• NIV treatement for >3 consecutive hours (without any interruption) before admission to ICU, intermediate care, or respiratory care unit and before randomization;
• Anticipated difficulties to conduct NIV (facial trauma or deformation, edentulous patient);
• End stage chronic respiratory insufficiency (defined as use of NIV at home or CPAP treatment at home and life expectancy below 6 month);
• Non-treated pneumothorax;
• Impossibility to perform subjective assessment of dyspnea and comfort (cognitive impairment);
• Patient under guardianship or trusteeship;
• Pregnancy/breastfeeding;
• Decision to withhold or to withdraw life-sustaining treatments (including intubation)
• Moribund state
• Current participation in another clinical trial with an endpoint related to NIV.
• No affiliation to social security (beneficial or assignee);
• Refusal to participate to the study (patient or legal representative or family member or close relative if present