Date Available


Year of Publication


Document Type



Graduate School


Biomedical Engineering

First Advisor

Charles F. Knapp


Magnetic Resonance Imaging (MRI) was used to determine changes in the size of the Inferior Vena Cava (IVC) as a result of blood pooling induced by lower body negative pressure (LBNP). Images of the IVC of supine human subjects (10 males, 10 females) were obtained under four conditions: 1) steady-state 0 mmHg LBNP, 2) steady-state –35 mmHg LBNP, 3) ramping from 0 to –35 mmHg LBNP, 4) ramping from –35 to 0 mmHg LBNP. Volumes for a given IVC segment were obtained under the first two conditions during both end inspiration and end expiration breath-holds. Inferior Vena Cava widths were measured under all four conditions at the levels of portal entry and portal exit. The IVC volume for men and women combined decreased 41% due to LBNP (p andlt; 1.02 x 10-9). The IVC was 64.4% wider at portal exit than at portal entry in men (p andlt; 0.0003). Lower Body Negative Pressure induced a decrease in men's vena cava width up to 46% at portal exit and up to 62% at portal entry. Supported by NASA EPSCoR WKU 522611 and NIH GCRC MO1 RR262.