INTRODUCTION: The platypnea orthodeoxia syndrome is a rare clinical entity combining positional dyspnea and arterial oxygen desaturation during the transition to orthostatism, reversible on return to decubitus. The most frequent etiology of this syndrome is the presence of a patent foramen ovale (PFO) responsible for a right-to-left intracardiac shunt, the severity of which results in significant functional disability and a risk of death from hypoxia. CASE REPORT: We report the case of a 93-year old patient on long-term oxygen, initially hospitalized for acute heart failure following a community-acquired urinary tract infection. The onset of recurrent positional dyspnea with desaturation on raising revealed a platypnea orthodeoxia syndrome. Transesophageal echocardiogram with bubble test revealed a large right-to-left shunt through a PFO, percutaneous closure of which led to complete resolution of symptoms and discontinuation of oxygen therapy. DISCUSSION AND CONCLUSION: The platypnea orthodeoxia syndrome associated with a patent foramen ovale often suffers from delayed diagnosis. Advanced age and co-morbidities should not prevent patients from undergoing percutaneous PFO closure, as the clinical benefit is important.