title: An international collaboration studying the physiological and anatomical cerebral effects of carbon dioxide during head-down tilt bed rest: the SPACECOT study.
abstract: Exposure to the microgravity environment results in various adaptive and maladaptive physiological changes in the human body, with notable ophthalmic abnormalities developing during 6-mo missions on the International Space Station (ISS). These findings have led to the hypothesis that the loss of gravity induces a cephalad fluid shift, decreased cerebral venous outflow, and increased intracranial pressure, which may be further exacerbated by increased ambient carbon dioxide (CO2) levels on the ISS. Here we describe the SPACECOT study (studying the physiological and anatomical cerebral effects of CO2during head-down tilt), a randomized, double-blind crossover design study with two conditions: 29 h of 12° head-down tilt (HDT) with ambient air and 29 h of 12° HDT with 0.5% CO2The internationally collaborative SPACECOT study utilized an innovative approach to study the effects of headward fluid shifting induced by 12° HDT and increased ambient CO2as well as their interaction with a focus on cerebral and ocular anatomy and physiology. Here we provide an in-depth overview of this new approach including the subjects, study design, and implementation, as well as the standardization plan for nutritional intake, environmental parameters, and bed rest procedures.NEW & NOTEWORTHYA new approach for investigating the combined effects of cephalad fluid shifting and increased ambient carbon dioxide (CO2) is presented. This may be useful for studying the neuroophthalmic and cerebral effects of spaceflight where cephalad fluid shifts occur in an elevated CO2environment.
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.|Faculty of Medicine, University of Cologne, Cologne, Germany.|Neural Systems Group, Massachusetts General Hospital, Harvard Medical School Charlestown, Massachusetts; and.
authors.forename: Karina
authors.identifier: http://orcid.org/0000-0002-5240-7625
authors.initials: K
authors.lastname: Marshall-Goebel
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
authors.forename: Edwin
authors.initials: E
authors.lastname: Mulder
authors.affiliation: Baylor College of Medicine, Houston, Texas.
authors.forename: Dorit
authors.initials: D
authors.lastname: Donoviel
authors.affiliation: Baylor College of Medicine, Houston, Texas.|Neural Systems Group, Massachusetts General Hospital, Harvard Medical School Charlestown, Massachusetts; and.
authors.forename: Gary
authors.initials: G
authors.lastname: Strangman
authors.affiliation: Baylor College of Medicine, Houston, Texas.
authors.forename: Jose I
authors.initials: JI
authors.lastname: Suarez
authors.affiliation: Baylor College of Medicine, Houston, Texas.
authors.forename: Chethan
authors.initials: C
authors.lastname: Venkatasubba Rao
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Frings-Meuthen
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Limper
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.|Department of Pediatrics and Adolescent Medicine, University of Cologne, Germany.
authors.forename: Jörn
authors.initials: J
authors.lastname: Rittweger
authors.affiliation: Baylor College of Medicine, Houston, Texas; bershad@bcm.edu.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Bershad
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000379:methods; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D002550:Cerebral Veins / Q000378:metabolism / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D018475:Head-Down Tilt / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012146:Rest / Q000502:physiology*; D013026:Space Flight / Q000379:methods; D014893:Weightlessness; D018474:Weightlessness Simulation / Q000379:methods
chemical_list: D002245:Carbon Dioxide
keywords: analog; intracranial pressure; microgravity; spaceflight; visual impairment