Inclusion Criteria:  Age ≥18 years.  Newly diagnosed OSA with AHI ≥ 15 events/hours.  Indication for OSA PAP therapy in routine clinical care according to applicable medical guidelines within one month prior to study enrolment.  Naïve to PAP therapy, i.e. even no PAP therapy during a PSG night.  Weight > 30kg.  Signed informed consent.  Exclusion Criteria:  Body Mass Index (BMI) of ≤20 kg/m² or ≥ 35 kg/m².  Pathologically low blood pressure (systolic ≤90mm Hg; diastolic ≤60 mm Hg).  Current unstable or serious medical conditions (such as angina pectoris, myocardial infarction, cancer, stroke, dementia, congestive heart failure) which based on the physician's judgment might put the patient at high risk.  Mixed and central apnea index ≥ 5 events/hour in PSG without PAP therapy.  Bullous lung disease.  Tracheostomy.  Pneumothorax.  Pneumocephalus.  Cerebrospinal fluid leak.  Current sinus or middle ear infection.  Persistent blockage of one or both nostrils (including nasal septum deviation and nasal polyps) or any other reason that leads to difficulty of breathing through the nose while awake.  Any nasal, facial or head abnormalities that would not allow adequate placement of the device.  Previous diagnosis of insomnia, narcolepsy or periodic limb movement disorder that in the judgment of the clinician could affect sleep quality assessment.  Chronic respiratory disease (COPD, pulmonary fibrosis or asthma) or FEV/FVC ≤ 60% in history.  History of respiratory failure.  Supplemental oxygen is required.  Uvulopalatopharyngoplasty or other surgical procedure to correct apnea.  Acute respiratory infection.  Subject recovered from Covid-19 but suffers from on-going symptoms or when subject's Covid-19 illness history can affect the study outcome based on the physician's judgment.  Pregnancy.  Medication that may alter sleep architecture.