Jessica M Scott1,2, Wesley J Tucker3, David Martin4, James B Crowell5, Elizabeth Goetchius4, Omar Ozgur6, Scott Hamilton6, Christian Otto1,2, Rebecca Gonzales5, Monica Ritter4, Nathanial Newby4, John DeWitt4, Michael B Stenger7, Robert Ploutz-Snyder1,8, Lori Ploutz-Snyder1,9, William H Morgan10, Mark J Haykowsky3. 1. Universities Space Research Association, Houston, Texas. 2. Memorial Sloan Kettering Cancer Center, New York, New York. 3. Integrated Cardiovascular Exercise Physiology and Rehabilitation Laboratory, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington. 4. KBRWyle, Houston, Texas. 5. MEI Technologies, Houston, Texas. 6. New York Eye & Ear Infirmary, New York. 7. National Aeronautics and Space Administration Johnson Space Center, Houston, Texas. 8. Applied Biostatistics Laboratory, Department of Systems, Populations, and Leadership, University of Michigan, Ann Arbor. 9. School of Kinesiology, University of Michigan, Ann Arbor. 10. Lions Eye Institute, Nedlands, Western Australia, Australia.
Abstract
Importance: Astronauts on International Space Station missions demonstrate adverse neuro-ocular changes. Reversing a negative translaminar pressure gradient (TLPG) by modulating cerebral blood flow, decreasing intracranial pressure, or increasing intraocular pressure (IOP) has been proposed as potential intervention for spaceflight-associated neuro-ocular syndrome (SANS). Objective: To examine whether exercise (resistance, moderate-intensity aerobic, and high-intensity aerobic) or artificially increasing IOP is associated with modulated cerebro-ocular hemodynamic and pressure changes during head-down tilt (HDT), an analogue of spaceflight, in healthy adults. Design, Setting, and Participants: A single-center investigation was conducted at Johnson Space Center, Houston, Texas, from January 1, 2014, to December 31, 2016, in 20 healthy men. Exposure: On 3 separate days, participants rested supine, were tilted to -15° HDT, and then completed 1 of 3 experimental exercise conditions (moderate-intensity aerobic, resistance, or high-intensity interval aerobic). A subset of 10 participants wore swimming goggles on all days. Main Outcomes and Measures: Applanation rebound tonometry was used to noninvasively assess IOP, and compression sonography was used to assess internal jugular venous pressure (IJVP). Estimated TLPG was calculated as the difference between IOP and IJVP. Cerebral inflow and outflow were measured in extracranial arteries using color-coded duplex ultrasonography. Results: Twenty men participated in the study (mean [SD] age, 36 [9] years). Compared with supine IOP (mean [SD], 19.3 [3.7] mm Hg), IJVP (mean [SD], 21.4 [6.0] mm Hg), and estimated TLPG (mean [SD], -2.1 [7.0] mm Hg), -15° HDT was associated with increased IOP (mean difference, 2.3 mm Hg; 95% CI, 1.4-3.3 mm Hg; P < .001) and IJVP (mean difference, 10.5 mm Hg; 95% CI, 8.9-12.2 mm Hg; P < .001) and with decreased TLPG (mean difference, -8.2 mm Hg; 95% CI, -10.1 to -6.3 mm Hg; P < .001). Exercise (regardless of modality) at -15° HDT was associated with decreased IOP (mean difference, -1.6 mm Hg; 95% CI, -2.6 to -0.6 mm Hg; P = .002) and TLPG (mean difference, -3.5 mm Hg; 95% CI, -6.2 to -0.7 mm Hg; P = .01) compared with rest. Both IOP (mean difference, 2.9 mm Hg; 95% CI, 0.7-5.1 mm Hg; P = .01) and TLPG (mean difference, 5.1 mm Hg; 95% CI, 0.8-9.4 mm Hg; P = .02) were higher in participants who wore swimming goggles compared with those not wearing goggles. Conclusions and Relevance: In this study, exercise was associated with decreased IOP and estimated translaminar pressure gradient in a spaceflight analogue of HDT. The addition of swimming goggles was associated with increased IOP and TLPG in HDT. Further evaluation in spaceflight may be warranted to determine whether modestly increasing IOP is an effective SANS countermeasure.
Importance: Astronauts on International Space Station missions demonstrate adverse neuro-ocular changes. Reversing a negative translaminar pressure gradient (TLPG) by modulating cerebral blood flow, decreasing intracranial pressure, or increasing intraocular pressure (IOP) has been proposed as potential intervention for spaceflight-associated neuro-ocular syndrome (SANS). Objective: To examine whether exercise (resistance, moderate-intensity aerobic, and high-intensity aerobic) or artificially increasing IOP is associated with modulated cerebro-ocular hemodynamic and pressure changes during head-down tilt (HDT), an analogue of spaceflight, in healthy adults. Design, Setting, and Participants: A single-center investigation was conducted at Johnson Space Center, Houston, Texas, from January 1, 2014, to December 31, 2016, in 20 healthy men. Exposure: On 3 separate days, participants rested supine, were tilted to -15° HDT, and then completed 1 of 3 experimental exercise conditions (moderate-intensity aerobic, resistance, or high-intensity interval aerobic). A subset of 10 participants wore swimming goggles on all days. Main Outcomes and Measures: Applanation rebound tonometry was used to noninvasively assess IOP, and compression sonography was used to assess internal jugular venous pressure (IJVP). Estimated TLPG was calculated as the difference between IOP and IJVP. Cerebral inflow and outflow were measured in extracranial arteries using color-coded duplex ultrasonography. Results: Twenty men participated in the study (mean [SD] age, 36 [9] years). Compared with supine IOP (mean [SD], 19.3 [3.7] mm Hg), IJVP (mean [SD], 21.4 [6.0] mm Hg), and estimated TLPG (mean [SD], -2.1 [7.0] mm Hg), -15° HDT was associated with increased IOP (mean difference, 2.3 mm Hg; 95% CI, 1.4-3.3 mm Hg; P < .001) and IJVP (mean difference, 10.5 mm Hg; 95% CI, 8.9-12.2 mm Hg; P < .001) and with decreased TLPG (mean difference, -8.2 mm Hg; 95% CI, -10.1 to -6.3 mm Hg; P < .001). Exercise (regardless of modality) at -15° HDT was associated with decreased IOP (mean difference, -1.6 mm Hg; 95% CI, -2.6 to -0.6 mm Hg; P = .002) and TLPG (mean difference, -3.5 mm Hg; 95% CI, -6.2 to -0.7 mm Hg; P = .01) compared with rest. Both IOP (mean difference, 2.9 mm Hg; 95% CI, 0.7-5.1 mm Hg; P = .01) and TLPG (mean difference, 5.1 mm Hg; 95% CI, 0.8-9.4 mm Hg; P = .02) were higher in participants who wore swimming goggles compared with those not wearing goggles. Conclusions and Relevance: In this study, exercise was associated with decreased IOP and estimated translaminar pressure gradient in a spaceflight analogue of HDT. The addition of swimming goggles was associated with increased IOP and TLPG in HDT. Further evaluation in spaceflight may be warranted to determine whether modestly increasing IOP is an effective SANS countermeasure.
Authors: Teresa C Chen; Barry Cense; Mark C Pierce; Nader Nassif; B Hyle Park; Seok H Yun; Brian R White; Brett E Bouma; Guillermo J Tearney; Johannes F de Boer Journal: Arch Ophthalmol Date: 2005-12
Authors: William H Morgan; Chandrakumar Balaratnasingam; Christopher R P Lind; Steve Colley; Min H Kang; Philip H House; Dao-Yi Yu Journal: Br J Ophthalmol Date: 2015-04-15 Impact factor: 4.638
Authors: Ronita L Cromwell; Jessica M Scott; Meghan Downs; Patrice O Yarbough; Susana B Zanello; Lori Ploutz-Snyder Journal: Med Sci Sports Exerc Date: 2018-09 Impact factor: 5.411
Authors: David S Martin; Stuart M C Lee; Timothy P Matz; Christian M Westby; Jessica M Scott; Michael B Stenger; Steven H Platts Journal: Physiol Rep Date: 2016-12
Authors: Stuart M C Lee; David S Martin; Christopher A Miller; Jessica M Scott; Steven S Laurie; Brandon R Macias; Nathaniel D Mercaldo; Lori Ploutz-Snyder; Michael B Stenger Journal: Front Physiol Date: 2020-07-28 Impact factor: 4.566
Authors: Alicen A Whitaker; Mohammed Alwatban; Andrea Freemyer; Jaime Perales-Puchalt; Sandra A Billinger Journal: PLoS One Date: 2020-10-29 Impact factor: 3.240