Platypnoea-orthodeoxia syndrome affects nocturnal oxygen desaturation: A case report.

A woman in her late 20s who had received an implantable cardioverter defibrillator in childhood for ventricular arrhythmia was diagnosed with severe obstructive sleep apnoea (apnoea-hypopnoea index, 77.1/h), and she began continuous positive airway pressure treatment. Before initiating this treatment, she had moderate hypoxaemia of unknown cause. She was admitted for adjustment of the position of her implantable cardioverter defibrillator, which had caused purple discoloration and ulceration of the overlying skin. On admission, she had dyspnoea and her arterial oxygen saturation by pulse oximetry significantly decreased while sitting. This led to detection of a patent foramen ovale and a right-to-left shunt while sitting. We diagnosed platypnoea-orthodeoxia syndrome with an atrial septal defect. Atrial septal defects should be suspected in hypoxic patients with obstructive sleep apnoea.