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http://hdl.handle.net/1942/23114
Title: | Separate and Combined Effects of Hypoxia and Horizontal Bed Rest on Retinal Blood Vessel Diameters | Authors: | LOUWIES, Tijs Jaki Mekjavic, Polona COX, Bianca Eiken, Ola Mekjavic, Igor B. Kounalakis, Stylianos DE BOEVER, Patrick |
Issue Date: | 2016 | Source: | INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, 57(11), p. 4927-4932 | Abstract: | PURPOSE: To assess the separate and combined effects of exposure to prolonged and sustained recumbency (bed rest) and hypoxia on retinal microcirculation. METHODS: Eleven healthy male subjects (mean ± SD age = 27 ± 6 years; body mass index [BMI] = 23.7 ± 3.0 kg m-2) participated in a repeated-measures crossover design study comprising three 21-day interventions: normoxic bed rest (NBR; partial pressure of inspired O2, PiO2 = 133.1 ± 0.3 mm Hg); hypoxic ambulation (HAMB; PiO2 = 90.0 ± 0.4 mm Hg), and hypoxic bed rest (HBR; PiO2 = 90.0 ± 0.4 mm Hg). Central retinal arteriolar (CRAE) and venular (CRVE) equivalents were measured at baseline and at regular intervals during each 21-day intervention. RESULTS: Normoxic bed rest caused a progressive reduction in CRAE, with the change in CRAE relative to baseline being highest on day 15 (ΔCRAE = -7.5 μm; 95% confidence interval [CI]: -10.8 to -4.2; P < 0.0001). Hypoxic ambulation resulted in a persistent 21-day increase in CRAE, reaching a maximum on day 4 (ΔCRAE = 9.4 μm; 95% CI: 6.0-12.7; P < 0.0001). During HBR, the increase in CRAE was highest on day 3 (ΔCRAE = 4.5 μm; 95% CI: 1.2-7.8; P = 0.007), but CRAE returned to baseline levels thereafter. Central retinal venular equivalent decreased during NBR and increased during HAMB and HBR. The reduction in CRVE during NBR was highest on day 1 (ΔCRVE = -7.9 μm; 95 CI: -13.3 to -2.5), and the maximum ΔCRVE during HAMB (24.6 μm; 95% CI: 18.9-30.3) and HBR (15.2 μm; 95% CI: 9.8-20.5) was observed on days 10 and 3, respectively. CONCLUSIONS: The diameters of retinal blood vessels exhibited a dynamic response to hypoxia and bed rest, such that retinal vasodilation was smaller during combined bed rest and hypoxia than during hypoxic exposure. | Keywords: | bed rest; physical inactivity; hypoxia; microvasculature; retina | Document URI: | http://hdl.handle.net/1942/23114 | ISSN: | 0146-0404 | e-ISSN: | 1552-5783 | DOI: | 10.1167/iovs.16-19968 | ISI #: | 000390156400049 | Rights: | This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. | Category: | A1 | Type: | Journal Contribution | Validations: | ecoom 2018 |
Appears in Collections: | Research publications |
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Louwies_2016_Invest Ophthalmol Vis Sci.pdf | Published version | 419 kB | Adobe PDF | View/Open |
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