Effects of recreational scuba diving on erythropoiesis-"normobaric oxygen paradox" or "plasma volume regulation" as a trigger for erythropoietin?

Abstract

Previous studies have shown an increase in erythrocyte lipid peroxidation and a decrease in red blood cell (RBC) count, hemoglobin, and hematocrit after only one recreational scuba diving session. The aim of this study was to examine the effect of repetitive scuba diving on RBC parameters and erythropoiesis. Divers (N = 14) conducted one dive per week over 5 weeks at a depth of 20-30m for 30min. For measuring RBC parameters, erythropoietin, iron, and ferritin, blood samples were collected before and after the first, third, and fifth dive. Between pre- and post-dive results, a statistically significant increase in RBC count, hemoglobin, hematocrit, mean corpuscular volume (MCV), RBC distribution width (RDW), iron, and ferritin was observed. Analysis of the results between the first, third, and fifth dive showed that the erythropoietin increase at the third (pre-dive p = 0.009; post-dive p = 0.004) and fifth dive (pre-dive p < 0.001; post-dive p = 0.003) was not accompanied by changes in RBC count, hemoglobin, iron, and ferritin. In parallel, a continuous increase in hematocrit, MCV, and RDW was observed, whereas mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) decreased. Changes in RBC indices and EPO elevation indicate that the occasional switch from hyperoxia to normoxia or mechanisms for plasma volume regulation may be a step in the maintenance of erythropoiesis.