Erythropoietin and Hematological Responses in Recreational Scuba Divers: Insight Into the Hyperoxic-Hypoxic Paradox.

Abstract

During scuba diving, breathing under elevated pressure leads to hyperoxia, which may induce oxidative stress and erythrocyte damage. Hyperoxia may also influence erythropoietin (EPO) production, a phenomenon referred to as the hyperoxic-hypoxic paradox. This study investigated changes in EPO levels and red blood cell (RBC) parameters after 1) a single dive, 2) three successive dives over 2 d, 3) the summer diving season. 1) Divers ( N = 23) completed a single 30-min dive to 30 m. Blood samples were collected immediately pre- and post-dive, and 3 h post-dive. 2) Divers ( N = 18) continued with successive 30-min dives, with blood collected immediately pre- and post-dive for each dive. 3) Divers ( N = 12) with more than 20 summer dives were resampled in September, 21 wk after the first sampling. No significant changes in EPO concentration were observed immediately post-dive or 3 h post-dive. During successive dives, EPO increased post-dive 2 ( P = 0.045, 18%), increased further pre-dive 3 ( P = 0.001, 24%), and reached the highest value post-dive 3 ( P < 0.001, 34%). After the summer diving season, no significant changes in EPO were observed. Decreases in RBC count, hemoglobin concentration, and hematocrit observed 3 h after a single dive were not observed across successive dives or after regular summer dives. Three successive dives over 2 d and regular recreational diving over 21 wk did not affect RBC count, hemoglobin concentration, or hematocrit. The progressive increase in EPO during successive dives warrants further investigation to clarify the underlying biological mechanisms.