AUTHOR=Kermorgant Marc , Leca Florian , Nasr Nathalie , Custaud Marc-Antoine , Geeraerts Thomas , Czosnyka Marek , Arvanitis Dina N. , Senard Jean-Michel , Pavy-Le Traon Anne TITLE=Impacts of Simulated Weightlessness by Dry Immersion on Optic Nerve Sheath Diameter and Cerebral Autoregulation JOURNAL=Frontiers in Physiology VOLUME=8 YEAR=2017 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2017.00780 DOI=10.3389/fphys.2017.00780 ISSN=1664-042X ABSTRACT=
Dry immersion (DI) is used to simulate weightlessness. We investigated in healthy volunteers if DI induces changes in ONSD, as a surrogate marker of intracranial pressure (ICP) and how these changes could affect cerebral autoregulation (CA). Changes in ICP were indirectly measured by changes in optic nerve sheath diameter (ONSD). 12 healthy male volunteers underwent 3 days of DI. ONSD was indirectly assessed by ocular ultrasonography. Cerebral blood flow velocity (CBFV) of the middle cerebral artery was gauged using transcranial Doppler ultrasonography. CA was evaluated by two methods: (1) transfer function analysis was calculated to determine the relationship between mean CBFV and mean arterial blood pressure (ABP) and (2) correlation index Mxa between mean CBFV and mean ABP.ONSD increased significantly during the first day, the third day and the first day of recovery of DI (