Last Updated on Jan 09, 2020

Recent Findings Related to Vascular Pressures in Space

Arterial blood pressure and heart rate are more difficult to evaluate during a space mission, as many factors can affect them. While some studies have demonstrated that microgravity can decrease both arterial blood pressure and heart rate, others have shown that heart rate, for example, remains unchanged in microgravity.(4)


However, the Spaceflight Associated Neuro-Ocular Syndrome (SANS), formerly the Visual Impairment and Intracranial Pressure (VIIP) Syndrome, has been recently identified as a health issue occurring in astronauts who have stayed in microgravity for at least 6 months. This syndrome was first reported in 2005, when a refractive change in visual acuity (mainly hyperopia) was detected after a long-term space mission.(5)

Visual Impairment and Intracranial Pressure Syndrome

This finding was further confirmed through evaluations conducted by means of a series of questionnaires applied to astronauts who took part in long space flight missions on the International Space Station (ISS). Very little is known regarding the risk factors and pathophysiological mechanisms involved in SANS. The current consensus within the spaceflight community is that visual changes and eye alterations (papilledema, posterior globe flattening, hyperopic shift, choroidal folds) are a consequence of raised intracranial pressures resulting in optic nerve sheath distension. This increase in optic nerve sheath diameter can readily be measured using a simple, non-invasive and low-cost ophthalmic procedure, resulting in an easy way to diagnose this medical condition. However, other factors, such as increased levels of carbon dioxide in the spacecraft, genetic predisposition, ocular and/or brain structural changes secondary to microgravity could also be involved in the aetiology of this syndrome.

References:

  1. What is microgravity? - (https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html)
  2. Human Pathophysiological Adaptations to the Space Environment - (https://www.frontiersin.org/articles/10.3389/fphys.2017.00547/full)
  3. Astronaut Lingo: What Is Puffy Head Bird Legs? - (https://airandspace.si.edu/stories/editorial/astronaut-lingo-puffy-head-bird-legs)
  4. Recent Findings in Cardiovascular Physiology with Space Travel - (https://www.ncbi.nlm.nih.gov/pubmed/19635590)
  5. Spaceflight-Induced Intracranial Hypertension and Visual Impairment - Pathophysiology and Countermeasures - (https://www.physiology.org/doi/full/10.1152/physrev.00017.2016)
  6. Emergencies in Space - (https://pdfs.semanticscholar.org/a102/d4e61620dd77f93639cf47492f7ca6f8c44f.pdf)
  7. Artificial gravity as a countermeasure for mitigating physiological deconditioning during long-duration space missions - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4470275/)

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