High Flow Nasal Oxygen for Exacerbation COPD

Inclusion Criteria: * Known chronic obstructive pulmonary disease * Acute hypercapnic exacerbation of this condition, defined as: PaCO2\>45 mmHg or \>6.0 kPa and pH 7.20-7.35 * Age \>40 years Exclusion Criteria: * Asthma * Immediate need for intubation, based on clinical judgement of the attending physician. * Impossibility to apply either one of the two interventions * Patient not expected to give immediate or delayed informed consent (e.g. known cognitive impairment, dementia, active serious psychiatric disease, mental retardation). * Established home-NIV or home CPAP, known indication for home-NIV or CPAP (e.g. OSAS or obesitas hypoventilation syndrome). * Impeding death * Concurrent (respiratory) diseases that may influence treatment efficacy: acute heart infarction, cardiogenic lung edema, massive pulmonary embolism (intermediate-high risk or more). NB; pulmonary infections (viral and bacterial) are a common cause of exacerbation and are no reason for exclusion. * Other acute diseases that preclude participation in the trial such as hemodynamic instability (need for vasopressors), reduced consciousness with need for intubation, severe intoxication * Tracheostomized patients * Participation in other interventional trials * Impossibility to admit the patient to the participating ICU or monitored ward (e.g. medium care / high dependency unit, depending on local infrastructure). * Previous explicit (or written) objection to participation in research - bicarbonate \<20 mmol/L