The purpose of this study in patients with obstructive sleep apnoea (OSA) and concomitant patent foramen ovale (PFO) is to assess the impact of percutaneous PFO closure on nocturnal hypoxemia and apnea/hypopnea, pulmonary and systemic artery pressure, endothelial function and arterial stiffness.

Inclusion Criteria:

• Patients with newly diagnosed moderate to severe OSA
• Age > 17 years
• Written informed consent for study participation.

Exclusion Criteria:

• Patients with other pulmonary disease associated with oxygen desaturation (other than obesity-associated pulmonary restriction)
• Patients with central sleep apnea syndrome
• Patients with other causes of pulmonary hypertension
• Intracardiac shunt other than via PFO
• Severe valvular heart disease
• Abnormal left ventricular (LV) systolic function (ejection fraction <50%)
• Obesity with BMI > 40
• Contraindication to TOE
• Severe pulmonary arterial hypertension (mean pulmonary artery pressure > 45 mmHg)