Figure 6.8 Dose Equivalent as a Function of Aluminum Shielding Thickness Table 6.6 NASA Astronaut Organ Dose - Equivalent Radiation __________ _____________ Exposure Limits______________________ Cardiovascular Adaptation With the loss of gravity's influence on the circulatory system, it is well established that a general cephalad fluid shift occurs as the fluid volume redistributes, free of the 1g force which normally pulls it Earthward. Symptoms of this fluid shift are facial puffing, sinus congestion, engorged neck veins and a remarkable reduction in lower limb girth (irrespective of muscular wasting). Blood pressure sensors, aortic and carotid baroreceptors, in the upper body sense only the increased blood volume and hence cause increased fluid loss through urination, resulting in a new lowered set point of blood volume. The primary concern comes with reentry into a 1g environment and a sudden loss of upper body blood volume, often resulting in fainting. This has been countered with a pre-return oral intake of fluid. However, the redistribution of body fluid and new set-point must be considered in any medical treatment or procedure in micro gravity. A more important concern to on-orbit construction may be reports of occasional arrhythmia's [Dietlein, 1983] detected especially during EVA. More research must be conducted on the impact of
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