Pulmonary embolus and patent foramen ovale: a rare cause of refractory hypoxaemia

A patient with a large pulmonary embolus is described. The striking features were those of cardiovascular stability with hypoxaemia and hypercapnia. Cardiac catheterization confirmed the pulmonary embolus; in addition there was found to be a patent foramen ovale (PFO), causing a large right-to-left shunt. Removal of the pulmonary embolus and closure of the PFO dramatically improved alveolar-arterial oxygen gradient and ventilatory requirements.