Ultrasonographic evaluation of ventilatory effect on inferior vena caval configuration.

Ventilatory effect on inferior vena caval configuration was studied by ultrasonography in 14 subjects, including 5 with chronic obstructive pulmonary disease, 3 with cardiac tamponade due to carcinomatous pericardial effusion, one with tuberculous constrictive pericarditis, and 5 normal subjects. The inferior vena caval lumen decreased in the early inspiratory phase, reached a minimum at the end of inspiration, distended again during expiration, and closed transiently 2 to 3 cm below the diaphragm during maximal inspiration. These ventilatory changes of the inferior vena cava reversed with increase in intrathoracic pressure during the Valsalva maneuver and positive-pressure ventilation. When the central venous pressure was increased, as in cardiac tamponade, the inferior vena cava was fully distended through the entire phase of inspiration and expiration. Collapsibility of the inferior vena cava was inversely proportional to central venous pressure when the pressure was less than 10 cm H2O, but not when the pressure was greater than approximately 10 cm H2O. Our results suggest that the study of inferior vena caval configuration with ultrasonogrphy is a valuable noninvasive clinical aid for estimating central venous pressure and for analyzing inferior vena caval hemodynamics in various clinical conditions.