Mechanical Countermeasures for Spaceflight-Associated Neuro-Ocular Syndrome during 30-days of Head Down Tilt Bed Rest: Design, Implementation, and Tolerability

Stefan Möstl ^1* Laura De Boni ¹ Jan-Niklas Hoenemann ^1,2 Tilmann Kramer ^1,2 Jan Schmitz ³ Dominik H. Pesta ^1,4,5,6 Timo Frett ¹ Maria Bohmeier ¹ Petra Frings-Meuthen ¹ Ann Charlotte Ewald ¹ Andrea Nitsche ¹ Patricia Loehr ¹ Alexandra Noppe ¹ Nicolas Klischies ¹ Alex S. Huang ⁷ Steven Laurie ⁸ Karina Marshall- Goebel ⁸ Brandon Richard Macias ⁹ Jens Tank ¹ Jens Jordan ^1,6 Edwin Mulder ¹

• ¹ Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Nordrhein-Westfalen, Germany
• ² University Hospital Cologne, Department of Internal Medicine III, Division of Cardiology, Pneumology, Angiology and Intensive Care, Cologne, Germany
• ³ University Hospital Cologne, Department of Anesthesiology and Intensive Care, Cologne, Germany
• ⁴ University Hospital Cologne, Centre for Endocrinology, Diabetes and Preventive Medicine (CEDP), Cologne, Germany
• ⁵ Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases, Faculty of Medicine, University of Cologne, Cologne, North Rhine-Westphalia, Germany
• ⁶ Faculty of Medicine, University of Cologne, Cologne, North Rhine-Westphalia, Germany
• ⁷ Shiley Eye Institute, School of Medicine, University of California, San Diego, La Jolla, California, United States
• ⁸ KBR, Inc, Houston, Texas, United States
• ⁹ Johnson Space Center, National Aeronautics and Space Administration, Houston, Texas, United States

Long-term space missions can cause the spaceflightassociated neuro-ocular syndrome (SANS), presumably evoked by cranial fluid shift.Lower body negative pressure and venous constrictive thigh cuffs can reduce cranial fluid shift, but have only been successfully tested in short-term studies. It is unclear whether these countermeasures are effective, and can be tolerated in the long term.For the first time, we tested these mechanical countermeasures during a 30-day strict head-down tilt bed rest study, a highly standardized model for microgravity-related immobilization, fluid shifts and neuro-ocular changes, akin to SANS. Novel to the present study is that we implemented a negative as well as a positive control group.The positive control group, which was exposed to a controlled seated position for six hour per day, is a particular strength of the study. In this work, we provide a detailed description of the entire study protocol and standardization procedures as well as countermeasure tolerability and safety.