Abstract
The objectives of this study were to determine whether 4 days of dry immersion (DI) induced similar arterial aging as spaceflight and to test the impact of thigh cuffs. Eighteen subjects underwent DI; nine wore thigh cuffs. Cardiac and arterial targets were assessed by ultrasound. No significant differences were found between the groups. The left ventricle volume, stroke volume (SV), and ejection fraction decreased with DI (p < 0.001). Carotid distensibility reduced (p < 0.05), carotid to femoral arterial tree became stiffer in 33% of the subjects, and femoral artery intima media thickness increased (p < 0.05). A reduction in plasma volume is likely to have caused the observed cardiac changes, whereas the arterial wall changes are probably best explained by hypokinesia and/or environmental stress. These changes are similar but lower in amplitude than those observed in spaceflight and mimic the natural aging effect on earth. The daytime-worn thigh cuffs had no acute or chronic impact on these arterial-focused measurements.
Highlights
Significant cardiovascular changes were reported during spaceflights and head-down bed rests (HDBRs), such as decreases in the left ventricle diastolic volume (LVDV), stroke volume (SV), decreases in limb arterial vascular resistance, or alteration of the orthostatic tolerance, right after these experiments[1,2,3]
Such changes occurred within the first day of HDBR or spaceflight, and were related to the abrupt cephalad fluid transfer induced by the environment or the position, and the subsequent adaptation
Was to test the chronic effect of the dry immersion with and without daytime thigh cuffs. This was achieved by testing baseline DISCUSSION
Summary
Significant cardiovascular changes were reported during spaceflights and head-down bed rests (HDBRs), such as decreases in the left ventricle diastolic volume (LVDV), stroke volume (SV), decreases in limb arterial vascular resistance, or alteration of the orthostatic tolerance, right after these experiments[1,2,3]. Such changes occurred within the first day of HDBR or spaceflight, and were related to the abrupt cephalad fluid transfer induced by the environment (microgravity) or the position (head-down position), and the subsequent adaptation. A significant increase in carotid artery wall stiffness was found alongside with disturbances in glucose metabolism[7]
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