EFFECT OF RESPIRATION ON VENOUS RETURN TO THE HEART

¹ From the Department of Roentgenology and the Department of Internal Medicine, Thoraxkliniken, Karolinska Sjukhuset, Stockholm, Sweden

In earlier investigations by other writers, it has been asserted that the supply of blood to the right side of the heart from the intra-abdominal part of the inferior vena cava increases during inspiration. On the basis of earlier experiments on animals with a view to studying the flow conditions in the inferior vena cava and the hepatic veins, and of the experiments performed here, it has been possible to show that this cannot be the case. In serial angiography of the passage of contrast material into the inferior vena cava and of the movements in the blood stream of a thin gold chain suspended in the superior vena cava, the following observations were made in the dog: During forced respiration, the venous return to the heart is balanced through an alternating supply of blood from the 3 main vascular regions. During inspiration, the blood flow in the superior vena cava is increased simultaneously with an increase of blood flow from the hepatic veins, while only a relatively small amount of blood passes from the intra-abdominal part of the inferior vena cava to the right atrium. During expiration, the supply of blood in the inferior vena cava flows to the right atrium. A part of the blood from the intra-abdominal part of the inferior vena cava refluxes to the hepatic veins, and flows to the right atrium only during the next inspiratory phase, together with the venous blood coming from the liver.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?