Absence of gravity-dependent modulation of straight sinus flow velocity in healthy humans.

The influence of whole-body positions on the cerebral blood flow in normal subjects is unclear. Blood flow in cerebral veins and sinuses is continuous, pulsatile and proportional to cerebral blood flow. We examined young healthy volunteers to evaluate peak mean flow velocity (vm) in the straight sinus (SS) assessed by transcranial Doppler sonography in predefined variations of the whole-body pitch position relative to gravity in the presence of a normal (normocarbia) and an impaired (hypercarbia) cerebral autoregulation.