THIS HIS PAPER is based on data obtained by direct recording of the pressures in the major intra-abdominal veins during respiration with the subject horizontal and erect. This investigation was carried out in an effort to determine whether or not normal respiration produces alterations of intraabdominal venous pressure which are sufficient to contribute to central flow while the subject is erect.
With the patient under local anesthetic, catheters of PE200 polyethylene were introduced into the iliac veins or inferior vena cava via the long or short saphenous vein. In a few instances difficulty was experienced in negotiating the saphenofemoral junction and a Seldinger guide was used. During the introduction of the catheters and at various times between recordings, the catheters were flushed with a slow infusion of heparinized saline. The exact levels at which recordings were made were established by injecting 60% sodium diatrizoate (Urografin) through the catheter in