Shallow habitat air dives I and II: human hematologic responses to compressed air saturation diving.

Two subjects each were exposed to pressure equivalents of 50 (SHAD I) and 60 (SHAD II) feet of sea water gauge (FSWG) for 30 and 28 d, respectively. Red blood cell (RBC) count, hemoglobin (Hb) content, and reticulocyte count of venous blood from divers were measured before, during, and after these exposures. RBC count of the divers decreased a maximum of 7.1% in the 50-ft dive and 10.7% in the 60-ft dive compared to surface control values. Hb content fell 7.7% and 11.1% in the 50- and 60-ft dives, respectively, when compared to nondiving subjects. Reticulocyte counts tended to increase late in the pressurization phase and during the recovery. The total month-long responses of Hgb in SHAD I, and RBC, Hgb, and reticulocyte count in SHAD II were significantly altered when compared to those of the surface control subjects. The changes in these factors were directly attributable to the month-long exposure to the total hyperbaric environment. The threshold for hematological effects of chronic exposure to compressed air would seem to lie between 50 and 60 FSWG.