Assessing the effects of artificial gravity in an analog of long-duration spaceflight: The protocol and implementation of the AGBRESA bed rest study.

A comprehensive strategy is required to mitigate risks to astronauts' health, well-being, and performance. This strategy includes developing countermeasures to prevent or reduce adverse responses to the stressors astronauts encounter during spaceflight, such as weightlessness. Because artificial gravity (AG) by centrifugation simultaneously affects all physiological systems, AG could mitigate the effects of weightlessness in multiple systems. In 2019, NASA and the German Aerospace Center conducted a 60-days Artificial Gravity Bed Rest Study with the European Space Agency (AGBRESA). The objectives of this study were to 1) determine if 30 min of AG daily is protective during head down bed rest, and 2) compare the protective effects of a single daily bout (30 min) of AG versus multiple daily bouts (6 × 5 min) of AG (1 Gz at the center of mass) on physiological functions that are affected by weightlessness and by head-down tilt bed rest. The AGBRESA study involved a comprehensive suite of standard and innovative technologies to characterize changes in a broad spectrum of physiological systems. The current article is intended to provide a detailed overview of the methods used during AGBRESA.

Gravity and Mastoid Effusion.

BACKGROUND: Asymptomatic mastoid effusions have recently been observed in astronauts returning from long-term spaceflight. In hospitalized patients, mastoid effusion increases the risks for bacterial otitis and mastoiditis. We reasoned that cephalad fluid shifts during strict -6° head down tilt bed rest could reproduce space-flight associated mastoid effusion and that artificial gravity may reverse the response. METHODS: The recent Artificial Gravity Bed Rest Study-European Space Agency study (AGBRESA) tested influences of artificial gravity during 60 days head down bed rest on a short-arm human centrifuge in healthy participants. The two intervention groups received daily artificial gravity with 30 minutes continuous artificial gravity or intermittent artificial gravity. A third group served as a control group and received no artificial gravity. We assessed cranial magnetic resonance images for mastoid effusions 1 day before bed rest, at days 14 and 52 of bed rest, and 3 days after bed rest. RESULTS: None of the participants exhibited mastoid effusions before bed rest. Six participants showed mastoid effusions at bed rest day 14 (4 continuous, 2 intermittent, 0 control). Fifteen participants showed mastoid effusions at bed rest day 52 and 3 days after bed rest (7 continuous, 3 intermittent, 5 control). CONCLUSIONS: Mastoid effusions commonly occur during strict head down tilt bed rest. The model can be applied to study the mechanisms and potential countermeasures for space flight-associated mastoid effusions. Formation of mastoid effusions during head down tilt bed rest is not prevented by daily 30 minutes short-arm intermittent or continuous centrifugation.