NASA
organizes the bed rest studies into campaigns. These campaigns
are composed of subject volunteers medically cleared to
participate in the Standard Measures and research tests
designed for each campaign. Every campaign and science
complement has been reviewed and approved by the NASA
JSC Committee for the Protection of Human Subjects, the
UTMB Institutional Review Board, the UTMB GCRC Advisory
Committee and any required investigator review boards.
All subjects have provided informed consent to participate
in the campaign.
Standard Measures are a series of multi-disciplinary
tests and reflect the same assessments as those performed
on ISS astronauts as part of their medical evaluation.
The results from these assessments:
- Became part of the medical monitoring of the subjects
- Increased the description of the physiologic responses
to bed rest in humans
- Provided a basis to compare bed rest results with
results from flight investigations
- Served as control data for the countermeasures and
provided ancillary data to individual investigators
The Standard Measures that were run on all subjects who
participated throughout the campaigns included:
- Neurocognitive Assessment
Cognitive changes are reported and measured during spaceflight and in simulations. Cognitive function of all subjects is measured before, during, and after bed rest using the same neurocognitive assessment tool required for crew members flying aboard long-duration spaceflight missions. Sustained concentration, verbal working memory, attention, short-term memory testing, spatial processing, and math skills are assessed by this computer-based tool.
- Clinical Laboratory Assessment
The Clinical Laboratory provides fundamental medical
hematologic, chemical, immunologic and urinary biochemical
analyses. This laboratory provides the capability
to perform sample analysis from the various investigations.
- Bone Mineral Density
These tests obtain measures of bone mineral density
before and after exposure to long-duration bed
rest to assess the effects of various proposed countermeasures
on disuse bone loss. A standard clinical technique
 known
as dual-energy X-ray absorptiometry (DEXA) and a peripheral
quantitative computed tomography (pQCT) are used to
obtain these measurements. Bone mineral density decreases
in bone sites such as the hip, spine, pelvis, and
heel when loads on the skeleton are reduced. Bed rest
has been shown to be a suitable analog for spaceflight
when studying changes in bone. When comparing spaceflight
results of bone loss to bed rest, the skeletal sites
affected and the underlying mechanism of bone loss
are the same.
- Clinical Nutritional Assessment
The goal of this protocol is to assess the nutritional
status of subjects before, during, and after bed rest.
This helps determine the response of nutrition and
related systems to bed rest, and to evaluate countermeasure
effectiveness in preventing negative side effects
of simulated weightlessness, and additionally to assess
whether countermeasures for one system have a negative
impact on another system.
 Maintaining dietary intake and nutritional status is essential to compare results from different bed rest studies. Maintaining crew health is imperative for long-duration space missions, and adequate nutrition will be critical for this effort. To provide nutritional recommendations to crew members for long-duration space travel, NASA needs to better understand how nutritional status and general physiology are affected by the microgravity environment. Bed rest is a well-accepted ground-based model of this environment.
In this nutritional status assessment protocol, blood and urine samples are analyzed
to provide information on general chemistry, as well
as to assess markers of hematologic, vitamin, and
mineral status. Markers of oxidative damage and of
bone metabolism (formation and breakdown) also are
measured. Detailed dietary intake analysis and anthropometric
information are also evaluated to better understand
the human response to bed rest and countermeasures.
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