TY - JOUR
T1 - Effect of Nightly Lower Body Negative Pressure on Choroid Engorgement in a Model of Spaceflight-Associated Neuro-ocular Syndrome
T2 - A Randomized Crossover Trial
AU - Hearon, Christopher M.
AU - Dias, Katrin A.
AU - Babu, Gautam
AU - Marshall, John E.T.
AU - Leidner, James
AU - Peters, Kirsten
AU - Silva, Erika
AU - Macnamara, James P.
AU - Campain, Joseph
AU - Levine, Benjamin D.
N1 - Funding Information:
Funding/Support: This study was supported by NASA (grants 80NSSC19K0300 and 80NSSC19K0300-P00001).
Publisher Copyright:
© 2022 American Medical Association. All rights reserved.
PY - 2022/1
Y1 - 2022/1
N2 - Importance: Astronauts returning from long-duration spaceflight experience ocular remodeling related to cephalad fluid shifts induced by microgravity. It is hypothesized that the absence of diurnal reductions in intracranial pressure in microgravity creates a low but persistent pressure gradient at the posterior aspect of the eye, which results in ocular remodeling and space-associated neuro-ocular syndrome (SANS) over many months. Objective: To determine whether partial reintroduction of footward fluid shifts during simulated microgravity via lower body negative pressure (LBNP) during sleep attenuates choroid engorgement, an early marker of ocular remodeling related to SANS. Design, Setting, and Participants: Between May 2019 and February 2020, participants with no major cardiovascular, kidney, or ophthalmic disease completed 3 days of supine (0°) bed rest with and 3 days without 8 hours of nightly LBNP in a randomized, crossover design. This single-center investigation took place at the UT Southwestern Medical Center. All analyses were conducted blinded to condition and time point. Interventions: Eight hours of nightly LBNP (-20 mm Hg) vs no LBNP. Main Outcomes and Measures: The primary outcome was the change in choroid area and volume after 3 days of bed rest measured by optical coherence tomography. Results: Of 10 participants, 5 were female, the mean (SD) age was 29 (9) years, and the age range was 18 to 55 years. Central venous pressure increased from the seated to supine position (mean [SD], seated: -2.3 [2.0] vs supine: 6.9 [2.0] mm Hg; P <.001), leading to choroid engorgement over 3 days of bed rest (Δ area: +0.09 mm2[95% CI, 0.04-0.13]; P =.001; Δ volume: +0.37 mm3[95% CI, 0.19-0.55]; P =.001). Nightly LBNP caused a sustained reduction in supine central venous pressure (mean [SD], 5.7 [2.2] mm Hg to 1.2 [1.4 mm Hg]; P <.001) and attenuated the increase in choroid area (74%) (Δ: 0.02 mm2[95% -0.02 to 0.06]; P =.01) and volume (53%) (Δ: 0.17 mm3[95% CI, 0.01-0.34]; P =.05) compared with control. Conclusions and Relevance: Nightly LBNP reinstated a footward fluid shift and mitigated the increase in choroid area and volume. LBNP during sleep may be an effective countermeasure for ocular remodeling and SANS during long-duration space missions..
AB - Importance: Astronauts returning from long-duration spaceflight experience ocular remodeling related to cephalad fluid shifts induced by microgravity. It is hypothesized that the absence of diurnal reductions in intracranial pressure in microgravity creates a low but persistent pressure gradient at the posterior aspect of the eye, which results in ocular remodeling and space-associated neuro-ocular syndrome (SANS) over many months. Objective: To determine whether partial reintroduction of footward fluid shifts during simulated microgravity via lower body negative pressure (LBNP) during sleep attenuates choroid engorgement, an early marker of ocular remodeling related to SANS. Design, Setting, and Participants: Between May 2019 and February 2020, participants with no major cardiovascular, kidney, or ophthalmic disease completed 3 days of supine (0°) bed rest with and 3 days without 8 hours of nightly LBNP in a randomized, crossover design. This single-center investigation took place at the UT Southwestern Medical Center. All analyses were conducted blinded to condition and time point. Interventions: Eight hours of nightly LBNP (-20 mm Hg) vs no LBNP. Main Outcomes and Measures: The primary outcome was the change in choroid area and volume after 3 days of bed rest measured by optical coherence tomography. Results: Of 10 participants, 5 were female, the mean (SD) age was 29 (9) years, and the age range was 18 to 55 years. Central venous pressure increased from the seated to supine position (mean [SD], seated: -2.3 [2.0] vs supine: 6.9 [2.0] mm Hg; P <.001), leading to choroid engorgement over 3 days of bed rest (Δ area: +0.09 mm2[95% CI, 0.04-0.13]; P =.001; Δ volume: +0.37 mm3[95% CI, 0.19-0.55]; P =.001). Nightly LBNP caused a sustained reduction in supine central venous pressure (mean [SD], 5.7 [2.2] mm Hg to 1.2 [1.4 mm Hg]; P <.001) and attenuated the increase in choroid area (74%) (Δ: 0.02 mm2[95% -0.02 to 0.06]; P =.01) and volume (53%) (Δ: 0.17 mm3[95% CI, 0.01-0.34]; P =.05) compared with control. Conclusions and Relevance: Nightly LBNP reinstated a footward fluid shift and mitigated the increase in choroid area and volume. LBNP during sleep may be an effective countermeasure for ocular remodeling and SANS during long-duration space missions..
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U2 - 10.1001/jamaophthalmol.2021.5200
DO - 10.1001/jamaophthalmol.2021.5200
M3 - Article
C2 - 34882176
AN - SCOPUS:85121276662
SN - 2168-6165
VL - 140
SP - 59
EP - 65
JO - JAMA Ophthalmology
JF - JAMA Ophthalmology
IS - 1
ER -