Expiration induced femoral flow in neonatal coarctation of aorta.

In a 3 day old infant with coarctation of the aorta a loud Doppler signal synchronous with expiration was present for some hours in the femoral vessels, with only barely audible signals synchronous with cardiac systole. It is suggested that in the presence of severe aortic constriction and temporary ductal closure, blood was pumped through the infradiaphragmatic arteries by increased intrathoracic expiratory pressure.