Properties of red blood cell after multiday exposure to 31 ATA.

Hematologic changes, osmotic fragility of red cells, and lipid contents of plasma and red blood cells were determined during the course of a 14-day dry saturation dive at 31 ATA (SEADRAGON IV). Increases in hematocrit and red blood cell count were observed during the early period at 31 ATA, which was attributed to hemoconcentration resulting from a diuresis. The osmotic fragility of red blood cells decreased slightly during the course of the experiment, but the changes were not related to the atmospheric pressure. Cholesterol and phospholipid content of the red blood cell and the plasma showed slight, insignificant daily variations independent of pressure. However, the same overall correlation was observed between the osmotic fragility and the phosphatidylcholine content of red blood cells and between the osmotic fragility and the total cholesterol level in the plasma, at both 1 ATA and 31 ATA. These correlations revealed an intimate relationship between the cell fragility and lipid composition of the cell membrane and the plasma within intra- and interindividual variations during the course of the experiment, but did not indicate any significant alteration of red blood cell function by the prolonged exposure to 31 ATA helium-oxygen environment. These results indicate that the exposure of human divers to 31 ATA for 14 days does not seem to induce any irreversible chemical changes in the red blood cell.