Five weeks of head-down tilt bed rest induced inward remodeling of the femoral artery and altered local carotid pulse pressure, without changing arterial stiffness or shear rate.
Does 5-week head-down tilt bed rest alter the structure and function of large arteries in healthy men?
Prolonged simulated microgravity via head-down tilt bed rest induces differential structural and flow adaptations in the carotid and femoral arteries.
The effects of simulated microgravity on the static and dynamic properties of large arteries are still mostly unknown. The present study evaluated, using an integrated vascular approach, changes in structure and function of the common carotid and femoral arteries (CCA and CFA) after prolonged head-down tilt bed rest (HDTBR). Ten healthy men were enrolled in a 5-week HDTBR study endorsed by the Italian Space Agency (ASI). Arterial geometry, flow, stiffness, and shear rate were evaluated by ultrasound. Local carotid pulse pressure and wave reflection were studied by applanation tonometry. After five weeks of HDTBR, CFA showed a decrease in lumen diameter without significant changes in wall thickness (IMT), resulting in an inward remodeling. Local carotid pulse pressure decreased and carotid-to-brachial pressure amplification increased. The ratio of systolic-to-diastolic volumetric flow in CFA decreased, whereas in CCA it tended to increase. Indices of arterial stiffness and shear rate did not change during HDTBR, either in CCA or CFA. In summary, prolonged HDTBR has a different impact on CCA and CFA structure and flow, probably depending on the characteristics of the vascular bed perfused.
Palombo et al. (Thu,) conducted a other in Healthy volunteers (n=10). Head-down tilt bed rest (HDTBR) was evaluated on Changes in structure and function of the common carotid and femoral arteries. Five weeks of head-down tilt bed rest induced inward remodeling of the femoral artery and altered local carotid pulse pressure, without changing arterial stiffness or shear rate.