, Volume 32, Issue 2, pp 203-206
Date: 01 Feb 2006

Ultrasonographic examination of the venae cavae

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There are two venae cavae in humans. The superior vena cava (SVC) comprises the connection of the left and right brachiocephalic veins and ends on the top of the right atrium, after entering the pericardium. The inferior vena cava (IVC) comprises the connection of the left and right iliac veins and ends on the floor of right atrium, after crossing the diaphragm. Whereas the SVC is an intrathoracic vessel, the IVC is an intraabdominal one, its short intrathoracic part being purely virtual. Both venae cavae provide venous return to the right heart, approx. 25% via the SVC and 75% via IVC [1, 2].

Ultrasonographic examination of the SVC can be performed by a transesophageal approach [3]. To remain open this collapsible vessel requires a distending pressure greater than the critical pressure producing collapse, i.e. its closing pressure. Because lung inflation increases pleural pressure more than right atrial pressure, the distending pressure of the SVC, i.e. right atrial pressure minus pleu ...