Noninvasive ventilation (NIV) weaning strategies differ considerably from one another. These strategies have yet not been compared to each other. Therefore, the investigators planned to perform a prospective, randomized, pilot study involving hypercapnic acute respiratory failure patients ready to be weaned off from NIV. The investigators are going to compare the success rate of NIV weaning and the duration of NIV after randomization between 3 NIV weaning methods: gradual decrease in duration of NIV or level of ventilator support, and abrupt discontinuation of NIV.

Inclusion Criteria:

Patients will be screened by the physician 24 hours (±6 hours) after initiation of NIV treatment if:

• Age ≥18 years old
• Hypercapnic ARF ( baseline pH<7.35, paCO2>45 mmHg, BORG>4)
• Breathing frequency< 25 bpm under NIV
• pH >7.35 under NIV
• 10% or more decrease from baseline PaCO2 under NIV
• Kelly ≤ 2 under NIV (Alert. Follows simple/3 step complex commands)
• PaO2 between 60 and 70 mmHg under NIV
• No need for sedation
• Systolic blood pressure 90-180 mmHg without vasopressors
• Body temperature 36-38°C
• Heart rate 50-120 bpm

The patient will be enrolled to the study and will be randomized to one of the NIV weaning protocols, if passes daily weaning criteria listed below after 1 hour of spontaneous breathing (with supplementary oxygen),

• Respiratory rate 8-30 bpm
• Systolic blood pressure 90-180 mmHg without vasopressors
• Body temperature 36-38°C
• Heart rate 50-120 bpm
• Neurologic score of Kelly ≤2 (Alert. Follows simple/ 3-step complex commands),
• SaO2 ≥88-92% with a FiO2≤40%.
• pH≥7.35
• Absence of severe dyspnea (BORG>4).

Exclusion Criteria:

• Age <18 years old
• NIV use at home for chronic respiratory failure
• CPAP use for acute respiratory failure
• NIV use as palliative treatment
• Severe heart failure with cardiac index ≤ 2 L/min/m2
• Severe hepatic failure with bilirubin ≥ 34.2µmol/L
• Severe renal failure with creatinine ≥ 220 µmol/L