Effects of Long Duration Spaceflight on Venous and Arterial Compliance

Background: The visual impairment and intracranial pressure (VIIP) syndrome is a spaceflight-associated medical condition consisting of a constellation of symptoms affecting approximately 70 percent of American astronauts who have flown long-duration missions to the International Space Station (ISS). VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures and has been hypothesized to be related to elevated intracranial pressure secondary to spaceflight-induced cephalad fluid shifts. Loss of visual acuity could be a significant threat to crew health and performance and have significant consequences during and post spaceflight. Purpose: The primary objective is to determine whether alterations in vascular compliance are related to the incidence of VIIP. Ocular structural and functional measures and vascular ultrasound of the head and neck were acquired in bed rest subjects completing 10-14 days in 6deg head-down tilt. Specific Aims: To evaluate the effect of age and simulated spaceflight (6 degrees head-down bed rest and sodium ingestion similar to International Space Station (ISS) astronauts) on vascular compliance and on the development of VIIP.