platypnea–orthodeoxia syndrome: multiple pathophysiological interpretations of a clinical picture primarily consisting of orthostatic dyspnea

Platypnea–orthodexia syndrome (POS) is often a challenging diagnostic problem. It is characterized by dyspnea that is accentuated by standing or sitting positions due to a marked fall in blood oxygen saturation, and instead is improved by assuming the lying position. In the present brief review, the authors address the pathophysiology of POS, and outline its clinical symptoms as well as the main modalities of diagnostic evaluation and possible therapeutic options. Moreover, some problems concerning much-debated issues and persistent uncertainties about the pathophysiology of POS are presented along with the description of the diagnostic and therapeutic resources currently available for this syndrome.