Changes in erythropoietin and haemoglobin concentrations in response to saturation diving

A reduction in haemoglobin concentration is consistently reported after deep saturation dives. This may be due to a downregulation of erythropoietin (EPO) concentration or to a toxic effect of the hyperoxia associated with the dives resulting in an increased destruction rate of erythrocytes. In this study haemoglobin concentration, blood cell counts, serum ferritin, bilirubin, haptoglobin and EPO concentrations were measured before, during and after a 19 day saturation dive to 240 m. The partial pressure of oxygen (PO₂) was 35–70 kPa during the 7 day compression and bottom phase, and 30–50 kPa during the 12 day decompression phase. There was a reduction in EPO concentration from 8.4±1.4 (mean±1SD) to 6.3±1.9 U·L⁻¹ on Dive day 2. On Dive days 7 and 17 EPO concentrations were not significantly different from baseline despite the continued exposure to hyperoxia. Immediately after the dive and return to a normoxic environment there was an increase in the EPO concencentration to 14.5±4.7 U·L⁻¹. Haemoglobin concentration, erythrocyte and reticulocyte counts were decreased at the end of the dive, and there was an increase in serum ferritin. There were no changes in bilirubin or haptoglobin concentrations indicative of haemolysis. It appears that the change in PO₂, rather than the sustained exposure to a hyperoxic environment, induces the changes in the EPO concentrations and erythropoietic activity.