Circulatory effects of internal jugular vein compression: a computer simulation study.

The effects of compression of the internal jugular veins and the inferior vena cava are simulated using an equivalent electronic circuit, which included simulation of cardiocirculatory phenomena and special features of the cerebral circulation. Compression of the inferior vena cava resulted in a profound decrease in cardiac output (from 4.5 to 1.51min(-1)) and arterial pressure (from 140/85 to 50/35 mmHg). Compression of the internal jugular veins resulted in a negligible decrease in cardiac output and arterial pressure, with a cerebral blood flow that was slightly decreased. Cerebral capillary and internal jugular pressures were considerably increased, leading to obstruction of cerebral veins and increased pressure (from 9 to 22 mmHg) and volume (from 120 to 145 ml) of the cerebrospinal fluid (CSF). Increased cerebral capsule compliance resulted in decreased CSF pressure (from 9 to 8.5 mmHg), but CSF volume increased (from 120 to 190 ml). A small increase in brain volume (from 1,000 ml to 1,060 ml, 6% volume increase) was compensated for by an equal decrease in the volume of CSF. When brain volume was above 1,080 ml, the absorption of CSF was reduced, and its pressure increased.