Abstract
Changes of body fluid distribution in response to the levels and/or direction of gravity, created by the parabolic flight of a jet airplane, were investigated in 5 healthy male subjects. Distribution of body fluid was estimated by using the impedance plethysmography. Electrodes were placed around the chest, abdominal, thigh, and calf regions. The gravity levels were altered from 1- to 1.8-G during the ascending phase and then μ-G was created for ∼23 sec. The recordings were performed in each subject with sitting, upright standing using both feet, and horizontal positions. For sitting position, the subject maintained the knee either at ∼120° on a seat or fully extended on a bed. Recordings were also performed at both supine and prone positions on a bed keeping their head toward either the nose or rear of the airplane. The greatest shift of fluid toward lower limbs was noted when the standing subjects were exposed to 1.8-G, and the shift was reversed toward the upper body at μ-G. Similar shifts were observed in sitting position on a seat, even though the magnitude was minor. Profound shift was not induced when the subjects were sitting on a bed. Further, slight, but significant, shift from the upper body toward lower extremity was seen in μ-G environment, when the subjects were at horizontal position keeping their head toward the nose of the airplane, or vice versa. These results suggest that body fluid clearly shifts toward upper body when the Gz gravity becomes zero. [J Physiol Sci. 2007;57 Suppl:S191]
