THE BLOOD FLOW IN THE CAVAL VEINS AT REST AND DURING EXERCISE IN NORMAL SUBJECTS

Abstract The relation between the flow in the superior vena cava and inferior vena cava has been measured on ten normal subjects both at rest and during exercise using the results of the oxygen saturation determinations on blood samples drawn from the pulmonary artery, superior vena cava and inferior vena cava. The result is that, with a doubling of the cardiac output caused by exercise using the lower extremities, the flow in the inferior vena cava is increased from 48% to 75% of the total flow. The importance of this for the calculation of the size of the shunt both at rest and during exercise in patients with atrial septal defects is discussed.