Body position and oxygenation: An intriguing relationship.

Dyspnea and hypoxemia are among the most common symptoms and signs that need to be assessed in clinical practice. This case illustrates how simple steps in history taking and physical examination can be crucial for diagnosis. We present a patient with intermittent hypoxemia, initially attributed to a pulmonary infection. However, the hypoxemia persisted even after successful treatment of the infection. Computed tomography angiography of the chest and ventilation/perfusion lung scan excluded pulmonary embolism. We then observed that the hypoxemia and dyspnea were triggered by orthostatism. An echocardiogram with a bubble test showed a patent foramen ovale, with a right-to-left shunt, without pulmonary hypertension. After percutaneous closure of the foramen ovale, the symptoms completely resolved. This is a case of platypnea-orthodeoxia syndrome, which is usually associated with patent foramen ovale or atrial septal defect and is typically observed in the elderly. The features and causes of this curious syndrome are discussed.