Human jugular vein collapse in the upright posture: implications for postural intracranial pressure regulation.

The agreement between predicted and measured IJV area in sitting supports the occurrence of a hydrostatic-viscous pressure balance in the IJVs, which would result in a constant pressure segment in these collapsed veins, corresponding to a zero transmural pressure. This balance could thus serve as the mechanism by which collapse of the IJVs regulates P dural and consequently ICP in the upright posture.