In this pilot study the feasibility of performing a larger trial to study the non-inferiority of High Flow Nasal Oxygen compared to non-invasive ventilation in patients with acute acidotic hypercapnic exacerbation of COPD wil be investigated

Rationale: Chronic Obstructive Pulmonary Disease (COPD) is frequently complicated by a worsening of symptoms, known as acute exacerbations (AECOPD). These exacerbations can result in a life-threatening condition with an impaired gas exchange, resulting in hypercapnia and as a result respiratory acidosis. The current standard of care of respiratory support for these patients is non-invasive ventilation (NIV), which has been shown to reduce morbidity and mortality. However, NIV is often unsuccessful, due to intolerance, agitation or patient-ventilation dyssynchrony. Furthermore, NIV is a resource-intensive therapy. High flow nasal oxygen (HFNO) is a non-invasive respiratory support mode that provides heated and humidified gas through soft nasal prongs. Several studies have shown that HFNO improves gas exchange and reduces work of breathing in non-hypercapnic respiratory failure. Furthermore, HFNO is thought to be better tolerated than NIV and the nursing effort may be lower compared to NIV. The hypothesis is that HFNO is non-inferior to NIV for patients with acidotic, hypercapnic AECOPD regarding the need for intubation and mortality, and that it increases patient comfort and reduces nursing effort.

Objective: To assess the feasibility of a larger study comparing HFNO with NIV as first line treatment in hypercapnic, acidotic AECOPD.

Study design: prospective, randomized, multi-center, unblinded, pilot study. Study population: Patients with acidotic, hypercapnic AECOPD Intervention (if applicable): HFNO versus NIV as first line treatment at presentation Main study parameters/endpoints: Feasibility: screening rate, inclusion rate, feasibility as qualified by staff and nurses.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: All participating patients will receive standard of care (i.e., admission to the monitored ward or ICU for intensive monitoring and regular blood withdrawals, steroids, bronchodilator inhalation therapy). There will be one extra questionnaire after 3 months, but no extra blood samples or site visits, compared to regular care for the participating patients. Permission of the patient will be obtained to register date of hospital discharge and outcome after ICU discharge and ask them to fill out questionnaires at 3 months after admission about their quality of life. Previous studies have not shown that HFNO is inferior to NIV with regards to outcomes (intubation rate, mortality), albeit that they were not powered to prove non-inferiority.

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