Hemodynamic effects of positive pressure ventilation: vena caval pressure in patients without injuries to the inferior vena cava.

In order to investigate the effect of positive pressure ventilation on vena cava blood flow, intraoperative manometric measurements were made in three patients with blunt abdominal trauma. These patients had intra-abdominal hemorrhage but no injury to the vena cava. The vena cava pressure increased with stepwise increases in the inspiratory pressure of the ventilator. The implications of this for the management of injuries to the inferior vena cava are: control of blood loss from caval wounds requires blockage of retrograde and antegrade caval blood flow; temporary cessation can stop retrograde caval flow from the right atrium and allow identification and repair of the caval defect; and retrograde caval blood flow can be used to flush out air bubbles and blood clots.