June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Effect of Spaceflight and Lower Body Negative Pressure on Intracranial Pressure
Author Affiliations & Notes
  • Jessica V Jasien
    CVL - NASA, JES Tech, Texas, United States
  • Steven Laurie
    KBR, Texas, United States
  • Stuart MC Lee
    KBR, Texas, United States
  • Karina Marshall-Goebel, PhD
    KBR, Texas, United States
  • Douglas J Ebert
    KBR, Texas, United States
  • David Kemp
    University College London, London, London, United Kingdom
  • Ashot Sargsyan
    KBR, Texas, United States
  • Scott A Dulchavsky
    Henry Ford Hospital, Detroit, Michigan, United States
  • Alan Hargens
    University of California San Diego, La Jolla, California, United States
  • Michael B Stenger
    NASA, Texas, United States
  • Brandon Macias
    NASA, Texas, United States
  • Footnotes
    Commercial Relationships   Jessica Jasien, None; Steven Laurie, None; Stuart Lee, None; Karina Marshall-Goebel, PhD, None; Douglas Ebert, None; David Kemp, None; Ashot Sargsyan, None; Scott Dulchavsky, None; Alan Hargens, None; Michael Stenger, None; Brandon Macias, None
  • Footnotes
    Support  NASA Human Research Program
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 2681. doi:
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    • Get Citation

      Jessica V Jasien, Steven Laurie, Stuart MC Lee, Karina Marshall-Goebel, PhD, Douglas J Ebert, David Kemp, Ashot Sargsyan, Scott A Dulchavsky, Alan Hargens, Michael B Stenger, Brandon Macias; Effect of Spaceflight and Lower Body Negative Pressure on Intracranial Pressure. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2681.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The head-to-foot hydrostatic pressure gradient causes intracranial pressure (ICP) to be ~0 cmH2O during upright posture on Earth, but the gradient is absent during spaceflight, resulting in a cephalad shift of blood and cerebrospinal fluid. It has been hypothesized that ICP is elevated during spaceflight and may contribute to development of optic disc edema which occurs in some astronauts; invasive ICP measures have not been obtained during spaceflight. On Earth, use of lower body negative pressure (LBNP) redistributes fluid caudally and lowers ICP, so may be capable of lowering ICP during spaceflight. The purpose of this study was to assess ICP during spaceflight using 3 noninvasive techniques (nICP) and to determine if LBNP can lower ICP during spaceflight to levels similar to upright posture on Earth.

Methods : Twelve astronauts were tested three months before spaceflight (preflight) in the seated and supine posture, and ~150 days (FD150) into spaceflight with and without 25 mmHg LBNP. Optic disc edema was determined using fundoscopy and optical coherence tomography (OCT) images. We assessed ICP using 3 noninvasive techniques: ultrasound measures of optic nerve sheath diameter (ONSD), cerebral and cochlear fluid pressure (CCFP) tympanic membrane displacement, and otoacoustic emission (OAE) phase shift. Mixed effects models were used to detect differences between conditions.

Results : One astronaut developed Frisen grade 1 optic disc edema, while OCT imaging showed subclinical retinal thickening in 8 of 12 astronauts. Measures of nICP after 150 days of spaceflight were not greater than nICP measured in either the seated or supine postures preflight. During spaceflight, the use of LBNP resulted in a reduction in nICP assessed by CCFP (94.7 -nL, p < 0.02), compared to -39.1 and 66.4 -nL changes in the seated and supine postures related to FD150, respectively. No changes were detected by the other nICP measures.

Conclusions : Despite development of subclinical and Frisen grade optic disc edema in some astronauts, our data suggest spaceflight results in a mild, chronic elevation of ICP similar to the supine position on Earth, and that LBNP did not result in changes indicative of ICP values similar to those of upright posture on Earth. Invasive measures of ICP may clarify these findings. Research is needed to determine if small reductions in ICP induced by LBNP would be sufficient to prevent optic disc edema.

This is a 2021 ARVO Annual Meeting abstract.

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