Acute Onset of Refractory Hypoxemia: A Rare Hemodynamic Cause of Dyspnea

Abstract

Platypnea-orthodeoxia syndrome (POS) is a rare condition of positional dyspnea with hypoxemia that can pose a diagnostic challenge to clinicians. We report two cases of POS with different pathophysiologic triggers and similar clinical features. In our report, both patients manifested a severe hypoxemia with low response to increase of fractional inspired oxygen, unremarkable physical examination of the lungs, and no radiological findings of the pulmonary embolism. In both cases, an interatrial communication was found in association with a right-to-left interatrial shunting. Recognition of POS is crucial because symptoms can be quickly relieved by recumbency, unlike other types of hypoxemia. This simple solution may prevent the use of sedative therapy, invasive ventilatory support, and vasopressor agents, which could even exacerbate the right-to-left extrapulmonary shunt and worsen clinical conditions.