Blood cell changes in asymptomatic divers

Many recent reports have suggested that diving and decompression cause changes in blood cells even when no overt symptoms of decompression sickness are present. This study subjected 10 normal persons to a pressure exposure of 100 fsw (30.5 msw) for 60 min followed by the standard U.S. Navy decompression schedule. No subject had symptoms of clinical decompression sickness. Repeated blood samples over a 3-week period spanning the simulated dive were analyzed for numbers of red cells, white cells, reticulocytes, platelets (by three methods), and size distribution of platelets. The study was designed to detect postdive changes of less than 5%. Small but definite decreases were found in levels of red cells, white cells, hematocrit, and platelets (by microscopic methods but not by machine), and the proportion of large platelets rose. The changes were too mild to support a proposed mechanism of decompression damage.