Platypnea-Orthodeoxia: A Case of Unexplained Hypoxia.

Introduction: Platypnea-orthodeoxia syndrome is a rare clinical syndrome defined by worsening deoxygenation and dyspnea when changing to an upright sitting or standing position. It is seen in 3 different clinical scenarios: intracardiac shunts, pulmonary arteriovenous shunts, and ventilation/perfusion mismatch in the lungs.

Case: An 82-year-old woman with a history of nonischemic cardiomyopathy with reduced ejection fraction was admitted with dyspnea and hypoxemia. She was found to have atrial septal defect with right to left shunting in the setting of normal right atrial pressures.

Discussion: Platypnea-orthodeoxia syndrome is a clinical syndrome where, in the setting of an interatrial communication, a right to left shunt can occur without elevated pulmonary or right atrial pressure, resulting in significant hypoxia.

Conclusion: Platypnea-orthodeoxia syndrome is a clinical condition that is being recognized more frequently due to more accurate diagnosis, and its treatment can alleviate symptomatic hypoxemia.