Autotitrating Versus Standard Non-invasive Ventilation (NIV) in Acute Exacerbation of Respiratory Failure

Inclusion Criteria: * patients admitted or transferred to Royal Brompton Hospital with acute exacerbation of chronic respiratory failure, or inpatients who suffer a deterioration in respiratory status, defined as 7.25 \< pH \< 7.35, PaCO2 \> 6.0kPa, and respiratory rate \> 20bpm Exclusion Criteria: * \< 18 years old * pH \< 7.25 * need for immediate intubation * uncontrolled cardiac failure * hypotensive (systolic blood pressure \< 90mmHg) * acute myocardial infarction * acute dysrhythmia * other system failure (e.g. acute renal failure, liver failure) * moderate or severe bulbar weakness * inability to understand rationale and/or consent form for study