Exposure to the microgravity environment results in various adaptive and maladaptive physiological changes in the human body, with notable ophthalmic abnormalities developing during 6-month 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 (ICP) 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 CO2 during Head-Down Tilt), a randomized, double-blinded cross-over 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% CO2. The internationally collaborative SPACECOT study utilized an innovative approach to study the effects of headward fluid shifting induced by 12° HDT and increased ambient CO2 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.
- intracranial pressure
- visual impairment
- Copyright © 2016, Journal of Applied Physiology