The investigators design a pilot randomised, single-centred, controlled trial to compare different withdrawal methods of Non-invasive ventilation. Our study aims at comparing stepwise withdrawal of Non-invasive ventilation versus immediate withdrawal of Non-invasive ventilation. The primary endpoint is to compare the rate of success between two withdrawal methods. The investigators define success as no recurrence of acute hypercapnic respiratory failure or restitution of Non-invasive ventilation within 48 hours after NIV is stopped. The secondary endpoints include time to recurrence of acute hypercapnic respiratory failure measured from the time of randomisation, the total days of Non-invasive ventilation use and the days of hospitalisation. Results from this trial will inform design of future randomised trial in this area.

All patients would receive standard medical treatment with inhaled bronchodilator, systemic steroid, antibiotics according to our local bacteriology. Acute NIV was initiated by trained respiratory nurses according to standardised protocols. The nurses would be at the bedside during the initial acclimatization. BIPAP vision was used to provide bi-level pressure support ventilation. Interfacing with different types of nasal or full-mask would be individualised. NIV was used for as many as possible in the first day, at least 20 hrs. Throughout the NIV treatment, the following parameters will be monitored when NIV is started: arterial blood gases, respiratory rate, heart rate and blood pressure, mental state, pulse oximetry. If a patient failed to respond to NIV, he or she would be intubated if appropriate. Criteria for failure include lack of clinical improvement with increasing dyspnea and deterioration of blood gases, hemodynamic instability, uncontrolled ventricular arrythmia, development of hypercapnic coma and cardiopulmonary arrest.

A patient would be considered suitable to withdraw from the ventilator if he or she fulfil the criteria at rest.

Inclusion Criteria:

• COPD patients with AHRF requiring NIV

• the patient is cooperative with NIV treatment

• the patient is willing to give their written informed consent to participate in the study

• patient is stabilised after acute treatment after NIV as evidenced by ALL of the below::

  • normalisation of arterial pH
  • clinical stability as evidenced by
  • SpO2 > 88% on 2LO2 or less
  • respiratory rate < 25
  • heart rate < 120 bpm
  • systolic blood pressure > 90 mmHg
  • patient not in agitation, diaphoresis or anxiety

Exclusion Criteria:

• patients with non-COPD causes of AHRF, for example, chest infection and heart failure
• patients who are currently on home NIV
• patients who have contraindications to NIV and those who refused or failed NIV during an initial 15 minutes acclimatization period
• other significant co-morbid conditions that in the investigators' view , would confer an adverse prognosis during the study period