Venoarterial Shunting in Obstructive Pulmonary Disease

THERE is conflicting evidence for the existence of direct pulmonary-artery-to-vein shunts in obstructive pulmonary disease.1 , 2 The venous admixture that occurs in these patients has been estimated after inhalation of 100 per cent oxygen and is probably due to the continued perfusion of collapsed or otherwise unventilated alveoli.3 , 4 Another possible cause of venous admixture is a shunt through a foramen ovale; the following review of previous work provides support for its existence in some patients with cor pulmonale.A patent foramen ovale has been observed in about 20 per cent of persons surveyed.5 A similar proportion has been observed in this . . .