An international collaboration studying the physiological and anatomical cerebral effects of carbon dioxide during head-down tilt bed rest: the SPACECOT study

• Published in: Journal of applied physiology (1985) 2017-06, Vol.122 (6), p.1398-1405
• Main Authors: Marshall-Goebel, Karina, Mulder, Edwin, Donoviel, Dorit, Strangman, Gary, Suarez, Jose I, Venkatasubba Rao, Chethan, Frings-Meuthen, Petra, Limper, Ulrich, Rittweger, Jörn, Bershad, Eric M
• Format: Article
• Language: English
• Subjects: Abnormalities; Adult; Anatomy & physiology; Bed rest; Bed Rest - methods; Blood flow; Brain - blood supply; Brain - physiology; Carbon dioxide; Carbon Dioxide - metabolism; Cerebral Veins - metabolism; Cerebral Veins - physiology; Cross-Over Studies; Design standards; Double-Blind Method; Gravitation; Head-Down Tilt - physiology; Human body; Humans; Immobilization; International cooperation; International Space Station; Intracranial pressure; Intracranial Pressure - physiology; Male; Microgravity; Middle Aged; Missions; Physiological effects; Physiology; Rest - physiology; Space Flight - methods; Standardization; Weightlessness; Weightlessness Simulation - methods
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00885.2016

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 (CO ) levels on the ISS. Here we describe the SPACECOT study (studying the physiological and anatomical cerebral effects of CO during 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% CO The internationally collaborative SPACECOT study utilized an innovative approach to study the effects of headward fluid shifting induced by 12° HDT and increased ambient CO as 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. A new approach for investigating the combined effects of cephalad fluid shifting and increased ambient carbon dioxide (CO ) is presented. This may be useful for studying the neuroophthalmic and cerebral effects of spaceflight where cephalad fluid shifts occur in an elevated CO environment.