Platypnea Orthodeoxia Syndrome Secondary to a Persistent Eustachian Valve.

Platypnea-Orthodeoxia syndrome (POS) is a rare and poorly understood syndrome characterized by platypnea and oxygen desaturation in the upright position that is relieved by recumbency. Here, we report a case of an 84-year-old woman who had chronic hypoxia in an upright position despite using home oxygen. The patient presented for hypoxia evaluation and was noted to have a restrictive pattern on pulmonary function tests (PFT). An echocardiogram showed a prominent eustachian valve extending from inferior to superior vena cava with contrast approaching the interatrial septum. The patient had a complete resolution of her platypnea following the closure of the patent foramen ovale.