Task Mechanical and gravitational countermeasures to ocular changes during strict head-down tilt bedrest (Marshall-Goebel)
Last Published:  07/30/21 01:05:34 PM (Central)
Short Title: SANS CM Bedrest - LBNP
Responsible HRP Element: Human Health Countermeasures
Collaborating Org(s):
Funding Status: Active - Currently funded and in progress
Procurement Mechanism(s):
Directed
Aims:

 

This study aims to evaluate countermeasures that prevent or mitigate the signs and symptoms associated with Spaceflight Associated Neuro-ocular Syndrome (SANS) and SANS-related behavioral outcomes including sleep, as well as investigation of potential mechanisms by which SANS occurs in this ground-based analog.

The bed rest campaign will consist of six arms, each lasting 30 days. Four of the study arms are captured in this task:

  1. A “posture-control” arm, where for the 30-day duration the subjects will be seated during the daytime and supine when sleeping (16 hrs. seated vs. 8 hrs. supine). This is a unique approach that has not been used before in bed rest research, but which is considered necessary to explore further:

    1. The mechanistic aspects of the fluid shift induced manifestations of SANS.

    2. Whether the objective and subjective aspects of sleep (which were correlated with the degree of thickening of retinal tissues) are associated with the fluid shifts and whether they are related to any degree of edema formation in the brain.

    3. A better insight into the mechanisms of the tested countermeasures in the other bed rest arms.

  2. A 6° head-down tilt "no countermeasure" control arm.

  3. A 6° head-down tilt “mechanical countermeasures” arm to test 25mmHg of lower body negative pressure (LBNP) applied 6 hours/ day.

  4. A 6° head-down tilt bed rest arm, where 6 hrs. seated will be used as the countermeasure to be tested and for example, compared to outcomes of the two control and the mechanical countermeasure arm, respectively.


The specific aims of this study:

  1. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular and cerebral structural changes during 30 days of strict 6° head-down tilt bedrest.
  2. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular functional changes during 30 days of strict 6° head-down tilt bedrest.
  3. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents vascular and cerebrospinal fluid changes during 30 days of strict 6° head-down tilt bedrest.
 
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