Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Hasso, R.
Effects of bedrest immobilization on vascular function
Humanmedizin; [ Diplomarbeit ] Graz Medical University; 2018. pp.
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Goswami Nandu
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- Abstract:
- Background: Cardiovascular deconditioning due to weightlessness is a major concern regarding long-term human spaceflight. Prolonged stay in a microgravity environment also causes a sometimes irreversible degradation in vision. 6° head down tilt bedrest (HDBR) has been established to simulate and study the effects of microgravity on earth. Retinal imaging offers a non-invasive and easily reproducible in-vivo depiction of the eye’s microvasculature to study changes in retinal vascular function during HDBR. The aim of this study is to assess the changes in microvascular function during HDBR by analyzing changes in central retinal vessel diameter via fundus photography. Methods: Data was collected during an ESA long-term bedrest campaign at MEDES space clinic in Toulouse. Retinal vascular images were obtained from ten healthy male subjects using a non-mydriatic, handheld fundus camera. Data collection took place two days prior to bedrest (BDC-2, baseline data collection) as well as on day 1, 8, 16 and 29 of HDBR (HDT01, HDT08, HDT16, HDT29, head-down tilt). Software image analysis was used to calculate central retinal arterial and venous equivalents (CRAE, CRVE) as well as arteriovenous ratio (AVR). Paired t-test was used to compare results between sampling time points. A p-value less than 0.05 was considered statistically significant. Results: The average central retinal vessel diameters were 128.78 ± 10.65µm (CRAE) and 197.07 ±13.56µm (CRVE), respectively. On the first day of bedrest (HDT01) no significant changes took place compared to the baseline (BDC-2). In comparison to HDT01 statistically significant changes happened to CRAE on HDT08 (125.41 ± 10.90, p = 0.007) and on HDT29 (126.80 ± 10.05, p = 0.011) and to CRVE on HDT29 (191.89 ± 11.90, p = 0.003). AVR showed no significant changes over the course of the study, averaging at 0.65 ± 0.04. Discussion: These results suggest that head down bedrest influences central retinal vessel diameter. Specifically, bedrest confinement leads to significant decreases in both central retinal artery and vein equivalent over the course of the study. These changes could be attributed to a myogenic response to the increased hydrostatic pressure caused by a cephalad-fluid shift induced by 6 degree head down bedrest. To my knowledge no previous study that has examined vascular changes in the retina over 60 days of bedrest immobilization.