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EXPERIMENT INFORMATION

Effects of Microgravity on Intracranial Pressure (NCC958CA02801)
Principal Investigator
Research Area:
Cardiovascular physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

Description
OBJECTIVES:
Astronauts have experienced visual changes that could be due to increased pressure in the brain. However the mechanism(s) underlying this problem remain unknown. The current working model is that microgravity induced fluid shifts increase intracranial pressure (ICP) and may be exacerbated by increases in the partial pressure of carbon dioxide in the International Space Station (ISS) atmosphere or exercise. Fluid compartment pressures have been very difficult to determine the expected and measured effects of microgravity. For example, central venous pressure (CVP) was expected to increase in space but actually fell to zero in microgravity. Moreover, it is difficult to conceive how the ICP in space could be greater than that which is routinely experienced on the ground in the recumbent posture. A more robust and reliable way to measure ICP with confidence is to make direct, invasive measurements of ICP during relevant changes in hydrostatic gradients. Moreover, concomitant evaluation of inflow (arterial) and outflow (venous) pressures and flows are essential to build the science base of the effect of gravitational gradients on intracranial hemodynamics.

The primary objective of this application was to make the first direct, invasive measurements of ICP and cerebral hemodynamics during changes in hydrostatic gradients induced by simulated (bed rest) and real (parabolic flight) microgravity. In order to accomplish these objectives, the following hypotheses was investigated:

Hypothesis 1: The transition from upright to supine posture increases intracranial and venous pressures that result in minimal changes in cerebral blood flow, oxygen delivery, and cerebral autoregulation. Additional gravitational loading and unloading by maneuvers result in small additional changes compared to the difference from standing to supine.

Hypothesis 2: True microgravity induced by parabolic flight will produce cerebrovascular changes that are qualitatively, and quantitatively similar to those observed during bed rest.


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Publications
Lawley JS, Levine BD, Williams MA, Malm J, Eklund A, Polaner DM, Subudhi AW, Hackett PH, and Roach RC. Cerebral spinal fluid dynamics: Effect of hypoxia and implications for high-altitude illness. Journal of Applied Physiology. (1985). 2016. January 15;120(2):251-62. [DOI]

Keywords
Intracranial pressure
Venous pressure
Central venous pressure
Cerebrovascular circulation
Arterial pressure

Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

Parameters
Arterial carbon dioxide tension
Cerebral autoregulation
Cerebral blood flow
Cerebrovascular hemodynamics
Intraarterial pressure
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Ground 05/01/2009 In Progress

Human Research Program (HRP) Human Research Roadmap (HRR) Information
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/

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Additional Information
Managing NASA Center
National Space Biomedical Research Institute (NSBRI)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Space Biomedical Research Institute (NSBRI)
Proposal Date
10/01/2012
Proposal Source
2011 Crew Health NNJ11ZSA002NA