OBJECTIVES:
Visual impairment and intracranial pressure (VIIP) is a newly described space flight-associated medical condition made up of a constellation of symptoms affecting at least 20% of American astronauts who have flown on International Space Station (ISS) missions (6 months). VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures. It has been hypothesized that the cephalad fluid shifts which occur with the loss of hydrostatic gradients are likely the primary contributor to the development of the syndrome. However, the presentation of the syndrome is similar to the terrestrial equivalent diagnosis of idiopathic intracranial hypertension (IIH) which includes elevated intracranial pressure (ICP). Loss of visual acuity is a significant threat to crew health and performance and may carry implications for years post-flight. It is therefore important to understand the pathogenesis of VIIP.

The purpose of this proposal is to use non-invasive methodologies (ultrasound) to track changes in venous and arterial compliance in vessels of the head and neck and relate these changes to development of the recently identified VIIP syndrome in astronauts. The study is composed of four research objectives (bed rest, astronaut ground, astronaut flight, and data mining), which encompass three specific aims.

Specific Aim I: To determine whether noninvasive measures of venous and arterial compliance are altered by long-duration space flight exposure in ISS astronauts and whether these changes are related to the development of the VIIP syndrome.

Specific Aim II: Using 14-days of 6 degrees head-down tilt bed rest as a model of space flight, to evaluate the effect of aging on vascular compliance using a subject population similar to younger (25-35 years) and older (45-55 years) astronaut cohorts.

Specific Aim III: To determine whether previous space flight experience or training in high performance jet aircraft predispose astronauts to lower venous compliance and/or the development of the VIIP syndrome (data mining effort).

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Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/