Hematologic changes after daily asymptomatic dives

Hematologic alterations after daily exposure to compression/decompression in open water are described. A standard dive to 100 fsw for 25 min was employed. Erythrocytes decreased postdive, reaching an apparent minimun 4 to 6 h after exposure and recovering to normal or supranormal value by 20 h postdive. Measurements of plasma volume after repeated dives showed a significant increase in volume at 4 h postdive. It is speculated that a phenomenon akin to cardiovascular deconditioning, caused by loss of the hydrostatic blood column in the lower extremities during immersion, results in a transitory fluid recruitment that may persist following several daily dives. Pre- and postdive partial thromboplastin times measured after repeated exposures failed to show a consistent response to compression/decompression.