Seadragon VI: a 7-day dry saturation dive at 31 ATA. I. Objectives, design, and scope.

Seadragon VI dive was designed to determine the effects on humans of a prolonged exposure to a 31 ATA, dry helium-oxygen environment. The specific objectives were to study a) circadian changes in renal-endocrine function, including a comprehensive characterization of nocturia; b) cardiovascular-endocrine responses to a 90 degree tilt; c) erythrocyte functions, including intracellular organic phosphates and the Donnan ratio for chloride; and d) blood enzyme profiles. The experiment was conducted over a period of 30 d in September and October 1984 at the Japan Marine Science and Technology Center, Yokosuka. Following a 5-d predive control period at 1 ATA in air, 4 male divers spent 7 d at 31 ATA in a helium-oxygen environment, and then returned to 1 ATA air after 12 d of decompression. They stayed an additional 3 d inside the chamber for postdive control measurements. The chamber temperature was maintained at 27-28 degrees C during pre- and postdive periods, 31-32 degrees C at 31 ATA, and 28-31 degrees C during decompression. At 31 ATA, PO2 and PCO2 of the chamber gas were maintained at approximately 225 and 2 mmHg, respectively. In this introductory paper, physical and physiologic characteristics of individual subjects, the major daily activity schedule, daily caloric intake, and the scope of investigation are presented.