Inclusion Criteria:  Adults undergoing an elective RFCA for atrial fibrillation in the Maastricht UMC Cardiac Catheter Labs under deep sedation administered by a clinician anesthesiology  Exclusion Criteria:  Age under 18 years Body Mass Index (BMI) > 32 kg/m² Diagnosed Sleep Apnoea Syndrome (SAS) Chronic Pulmonary Obstructive Disease (COPD) gold IV and COPD gold III with frequent or recent exacerbation Diagnosed pulmonary or cardiac condition requiring chronic oxygen therapy Complete nasal obstruction Active nose bleeding Untreated pneumothorax (pre- existing) Recent upper airway surgery Recent base of skull fracture Expected difficult airway