Q:  What is Platypnea-orthodeoxia?

Answer: Platypnea-orthodeoxia is a clinical syndrome characterized by dyspnea and deoxygenation accompanying a change to a sitting or standing from a recumbent position.

Two conditions must coexist to cause platypnea-orthodeoxia:

an anatomical component - in the form of an interatrial communication such as PFO or ASD and

a functional component - that produces a deformity in the atrial septum and results in a redirection of shunt flow with the assumption of an upright posture. This includes pericardial effusion, constrictive pericarditis, emphysema, pneumonectomy, cirrhosis, ileus, aortic aneurysm etc.

Standing upright could stretch the interatrial communication, allowing more streaming of venous blood from inferior vena cava through the defect. This redirection of flow caused by an anatomic distortion of the right atrium or the atrial septum get clinically enhanced by functional component present.



Reference:

Cheng TO. - Platypnea-orthodeoxia syndrome: etiology, differential diagnosis, and management. Cathet Cardiovasc Interv. 1999; 47: 64–66..