Head-Down Tilt Bed Rest Studies as a Terrestrial Analog for Spaceflight Associated Neuro-Ocular Syndrome

Abstract

Astronauts who undergo prolonged periods of spaceflight may develop a unique constellation of neuro-ocular findings termed Spaceflight Associated Neuro-Ocular Syndrome (SANS). SANS is a disorder that is unique to spaceflight and has no terrestrial equivalent. The prevalence of SANS increases with increasing spaceflight duration and although there have been residual, structural, ocular changes noted, no irreversible or permanent visual loss has occurred after SANS, with the longest spaceflight to date being 14 months. These microgravity-induced findings are being actively investigated by the United States' National Aeronautics Space Administration (NASA) and SANS is a potential obstacle to future longer duration, manned, deep space flight missions. The pathophysiology of SANS remains incompletely understood but continues to be a subject of intense study by NASA and others. The study of SANS is of course partially limited by the small sample size of humans undergoing spaceflight. Therefore, identifying a terrestrial experimental model of SANS is imperative to facilitate its study and for testing of preventative measures and treatments. Head-down tilt bed rest (HDTBR) on Earth has emerged as one promising possibility. In this paper, we review the HDTBR as an analog for SANS pathogenesis; the clinical and imaging overlap between SANS and HDTBR studies; and potential SANS countermeasures that have been or could be tested with HDTBR.

Challenges of Artificial Intelligence in Space Medicine

“…Despite the many challenges, the future of AI in space medicine remains very promising. The investments made in developing AI technology for space medicine will continue to benefit society similar to how previous AI for identifying meteors in space was translated to improve the detection of breast malignancy in mammograms, and how bone demineralization studies in space provided insights on the pathogenesis of osteoporosis [25]. Over time, AI systems will continue to improve, becoming more intelligent and allow healthcare in space to become more data-driven, personalized, and preventative to improve the health outcomes of astronauts.…”

“…Another potential solution is to utilize ground-based analogs on Earth to generate data. To induce many of the physiological changes that occur during spaceflight, terrestrial analog studies such as the six-degree head-down tilt bed rest are utilized [25]. Head-down tilt bed rest is cur-rently the gold standard terrestrial analog for mimicking cephalad fluid shifts that occur in microgravity.…”

A perspective on spaceflight associated neuro-ocular syndrome causation secondary to elevated venous sinus pressure

“…There are similarities between SANS and IIH, however, there are also differences. Terrestrial symptoms of IIH include headache and pulsatile tinnitus, but astronauts with SANS do not complain of these symptoms 7 . IIH presents more often as bilateral eye changes, predominately in women, but SANS has a higher asymmetric or unilateral presentation and is more common in men 1 .…”

Biological and Mechanical Characterization of the Random Positioning Machine (RPM) for Microgravity Simulations

“…Hence, few clinical data are available to clarify the exact impact of microgravity on the human body [27]. Thus, tests focusing on the effects of gravity unloading can be performed on humans with the so-called "head-down tilt bed" studies [28,29], or can be more easily performed in vitro with the help of microgravity simulators [9].…”