Haematology studies during a 350-metre dive

Routine haematological monitoring of 6 deep-sea divers was performed pre-dive, during the three phases of the 350 m working dive, and at two post-dive medical examinations. In the compression phase a small percentage (less than 5%) of each subject's red cells became non-discoid in shape and this trend continued during the 6 d at 350 m. Concomitantly each subject was mildly dehydrated by compression diuresis and had a raised haematocrit (+5%); all other haematological parameters remained within normal limits. The number of morphologically aberrant cells continued to increase during decompression but were not present at the 1 month post-dive medical examination. The subjects' mean relative reticulocyte number was decreased during the dive to 0.4%, showing a rapid and sustained increase to 2.1% at both post-dive examinations. The red cell count was reduced by 10% during the course of the dive. Hb concentration and haematocrit evidenced no differences between the pre- or post-dive measurements.