title: Serum erythropoietin levels in healthy humans after a short period of normobaric and hyperbaric oxygen breathing: the "normobaric oxygen paradox".
abstract: Renal (peritubular) tissue hypoxia is a well-known physiological trigger for erythropoietin (EPO) production. We investigated the effect of rebound relative hypoxia after hyperoxia obtained under normo- and hyperbaric oxygen breathing conditions. A group of 16 healthy volunteers were investigated before and after a period of breathing 100% normobaric oxygen for 2 h and a period of breathing 100% oxygen at 2.5 ATA for 90 min (hyperbaric oxygen). Serum EPO concentration was measured using a radioimmunoassay at various time points during 24-36 h. A 60% increase (P < 0.001) in serum EPO was observed 36 h after normobaric oxygen. In contrast, a 53% decrease in serum EPO was observed at 24 h after hyperbaric oxygen. Those changes were not related to the circadian rhythm of serum EPO of the subjects. These results indicate that a sudden and sustained decrease in tissue oxygen tension, even above hypoxia thresholds (e.g., after a period of normobaric oxygen breathing), may act as a trigger for EPO serum level. This EPO trigger, the "normobaric oxygen paradox," does not appear to be present after hyperbaric oxygen breathing.
authors.affiliation: Divers Alert Network Europe Research Division, Haute Ecole Paul Henri Spaak, Pôle Universitaire de Bruxelles Wallonie, 91 Ave. C. Schaller, 1160 Bruxelles, Belgium. balestra@daneurope.org
authors.forename: Costantino
authors.initials: C
authors.lastname: Balestra
authors.forename: Peter
authors.initials: P
authors.lastname: Germonpré
authors.forename: Jacques R
authors.initials: JR
authors.lastname: Poortmans
authors.forename: Alessandro
authors.initials: A
authors.lastname: Marroni
mesh_terms: D001785:Blood Gas Monitoring, Transcutaneous; D004921:Erythropoietin / Q000097:blood*; D005260:Female; D006801:Humans; D006931:Hyperbaric Oxygenation; D018496:Hyperoxia / Q000097:blood; D000860:Hypoxia / Q000097:blood; D008297:Male; D010100:Oxygen / Q000097:blood; D013997:Time Factors
chemical_list: D004921:Erythropoietin; D010100:Oxygen