FLUID SHIFTS INTO AND OUT OF SUPERFICIAL TISSUES UNDER MICROGRAVITY AND TERRESTRIAL CONDITIONS

The microgravity environment can be expected in man to induce a swelli ng of facial tissues and a shrinking of the tissues in the lower limbs together with a loss in body weight. To quantitate fluid shifts into and out of superficial tissues an ultrasound A-mode method was used in one cosmonaut during a 7-day spaceflight. Measurements were taken fro m frontal and tibia tissues, where the underlying bone provides a good back-wall echo. During the spaceflight the cosmonaut showed a swellin g of facial tissues during the first 3 days. At the same time the supe rficial tissues of the caudal areas shrank by 20%. In space he lost 7. 7% of body weight. After the spaceflight the superficial tissues were dried out but regained their water content within the next 4 days even before body weight returned to control level. Per kilogram of body we ight an increase of 400 cm3 entered the superficial tissue layers of t he body. It is concluded that water loss as well as wasting of tissues contribute to the loss in body weight during space flight.