Inclusion Criteria:

• COPD patient with AHRF who survives after treatment with NIV and successfully weaned off for at least 48 hours.
• Patients who have been intubated and mechanically ventilated can be included if they have also been treated with NIV in the same hospital admission
• Significant obstructive sleep apnoea ruled out by overnight polysomnography done after successful weaning of NIV (Apnoea-hypopnoea index, AHI, < 10/hr
• Patients willing to give their written informed consent to participate in the study
• Patients understand that he/she would be randomised into receiving home NIV or sham ventilation
• Patients who are able to use the home pressure support ventilators after a period of acclimatisation and training before discharge from the hospital

Exclusion Criteria:

• Patients with non-COPD causes of AHRF (e.g. asthma, bronchiectasis or lobar pneumonia, fibrothorax, acute pulmonary oedema, etc)
• Patients who have contraindications to NIV and those who refused or failed NIV during an initial 15-minute acclimatization period
• Active smoker
• An increase of ≥ 15% in FEV1 after inhaled salbutamol (200μg)
• Obstructive sleep apnoea (OSA) with apnoea-hypopnoea index (AHI) of ≥ 10/hr
• Other significant co-morbid conditions that in the investigators' view, would confer an adverse prognosis during the study period, e.g., congestive heart failure, uncontrolled diabetes mellitus, tuberculosis, neoplasms, peripheral vascular disease threatening organ functions
• Adverse psycho-social circumstances not conducive to home NIV treatment (Appendix 2)
• On long-term systemic steroid (prednisolone ≥ 7.5 mg per day for ≥ 3 months)